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Characterization and dissolution of secondary weathering products from the gibralter mine site Shum, Michael Gin Wah 1999

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CHARACTERIZATION AND DISSOLUTION OF SECONDARY WEATHERING PRODUCTS FROM THE GIBRALTAR MINE SITE by MICHAEL GIN WAH SHUM B.Sc, Simon Fraser University, 1990 M.Sc., The University of British Columbia, 1995 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Department of Soil Science) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA June 1999 © Michael Gin Wah Shum, \<ffl In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of vS>Q // Sirt«?/i]c£ The University of British Columbia Vancouver, Canada Date BZUb/ ?9 DE-6 (2/88) ABSTRACT Metal leaching and acid rock drainage is one of the most important environmental problems facing the mining industry today. Weathering of mined waste rock leads to the dissolution of minerals, releasing a variety of metals, some of which are retained and temporarily stored. Secondary weathering products formed in mine waste weathering environments can serve as a sink for a variety of metals. Literature suggests that up to 90% of metals released from weathering are retained in waste rock dumps. Mobilization of these stored metals can occur in response to environmental changes and waste re-handling, potentially resulting in detrimental effects for the receiving environment. This research examines the composition, and investigates the stability, of stored weathering products in waste rock at the Gibraltar mine, and assesses their role in controlling the future contribution to metal loading using a pedogenetic approach to waste rock and secondary weathering products. The results indicate that the dominant metals retained in the waste rock were oxidized Fe phases, with lesser amounts of Cu and Al. These phases were in the form of sulphates and oxyhydroxysulphates. Zones of accumulation were identifiable from morphological features (colour). Colour, imparted by Fe allowed for the identification of two distinct zones. Zones of Fe accumulation were associated with higher levels of Al, Mo, S, and Si, and zones of poor Fe accumulation were associated with higher levels of Cu and K. The chemically different zones within the rock dump were not correlated to ii distinct mineralogical or physical differences. Secondary phases seemed to become more stable with aging and advanced weathering, suggesting mineral rearrangement was occurring. This was confirmed by changes in the quantities of soluble and metastable weathering products in different areas of the rock dump. Dissolution of soluble secondary weathering products was shown to be a rapid process, with zones of Fe accumulation releasing greater quantities of metals than zones of low Fe accumulation. After the initial dissolution of soluble weathering products, metastable phases begin to contribute to the level of metals in solution. Dissolution of minerals and the release of metals was more effective with organic chelating acids than with HNO3,which was more effective than unbuffered water, suggesting long term waste management practices must consider changes in metal release as waste rock becomes more soil-like with time through the integration of the biotic component and the incorporation of greater quantities of soil organic matter. i i i T a b l e o f C o n t e n t s ABSTRACT ii TABLE OF CONTENTS iv LIST OF TABLES vii LIST OF FIGURES ix ACKNOWLEDGEMENTS xii 1. INTRODUCTION 1 1.1 GENERAL INTRODUCTION 1 1.2 OBJECTIVES 6 2. LITERATURE REVIEW 8 2. l M I N E WASTE R O C K DUMPS 9 2.1.1 construction methods 9 2.1.2 moisture regime 12 2.2 WEATHERING 16 2.3 WEATHERING PROCESSES 19 2.4 MINERAL STABILITY 24 2.5 A C I D R O C K DRAINAGE CHEMISTRY AND STORED WEATHERING PRODUCTS 27 2.7 STORAGE MECHANISMS FOR WEATHERING PRODUCTS 34 2.8 FACTORS AFFECTING PRODUCT FORMATION 39 2.9 PRECIPITATED WEATHERING PRODUCTS IN OTHER ENVIRONMENTS 42 2.9.1 stream precipitates 42 2.9.2 elemental sulphur stock piles 42 i v 2.9.3 acid sulphate soils 43 2.9.4 salt effloresecences 45 2.9.5 saprolites 46 2.10 IDENTIFICATION AND CHARACTERIZATION METHODS 48 2.11 S U M M A R Y 52 3. STUDY AREA 54 3.1 LOCATION AND CLIMATE 54 3.2 SITE GEOLOGY 55 3.3 WASTE ROCK D U M P CONSTRUCTION AND MINERALOGY 57 3.4 ACID LEACHING 59 3.5 STUDY TRENCHES 60 4. CHEMICAL AND MINERALOGICAL CHARACTERIZATION OF WASTE ROCK SAMPLES COLLECTED BASED ON MORPHOLOGICAL CHARACTERISTICS 62 4.1 INTRODUCTION 62 4.2 METHODS: FIELD AND LABORATORY PROCEDURES 66 4.3 RESULTS AND DISCUSSION 72 4.4 CONCLUSIONS 89 5. DISTRIBUTION AND CHARACTERIZATION OF STORED WEATHERING PRODUCTS IN ACID- AND NON-LEACHED WASTE ROCK 91 5.1 INTRODUCTION 91 5.2 METHODS 94 5.3 RESULTS AND DISCUSSION 96 5.5 CONCLUSIONS 123 6. PARTITIONING OF ELEMENTS IN SECONDARY WEATHERING PRODUCTS.... 125 6.1 INTRODUCTION 125 6.2 METHODS 129 6.3 RESULTS AND DISCUSSION 136 6.4 CONCLUSIONS 174 7. DISSOLUTION OF STORED WEATHERING PRODUCTS F R O M HIGHLY OXIDIZED WASTE ROCK 178 7.1 INTRODUCTION 178 7.2 METHODS 180 7.3 RESULTS AND DISCUSSION 186 7.4 CONCLUSIONS 226 8. SUMMARY AND CONCLUSIONS 229 9. LITERATURE CITED 234 10. APPENDIX 254 vi. List of Tables Table 2.1 Physical properties of waste dumps producing acid rock drainage (taken from Ritchies, 1994) 10 Table 2.2 Factors affecting mine waste dump hydrology (Whiting, 1981) 13 Table 2.3 Function of water in active weathering 21 Table 2.4 Relative stability of some common minerals associated with igneous rocks and their associated elements 26 Table 2.5 Trace elements coprecipitated with secondary soil minerals (Sposito, 1989) 35 Table 4.1 pH, Munsell colour, and particle size characterization of all samples collected from the Gibraltar mine site 74 Table 4.2 Summary of total elemental analyses (XRF) from each trench: sand fraction 78 Table 4.3 Summary of total elemental analyses (XRF) from each trench: silt+clay fraction. 79 Table 4.4 Spearman rank correlation coefficients between sand and silt+clay fractions grouped according to the level of significance 84 Table 4.5 Significant Spearman rank correlations between Hurst colour rating and total elements 85 Table 5.1 Elemental analyses from acid ammonium oxalate extractions of the sand and silt+clay fractions 97 Table 5.2 Elemental analyses from citrate bicarbonate dithionite extraction of the sand and silt+clay fractions 98 Table 5.3 Ratios for acid ammonium oxalate extractable Fe to citrate bicarbonate dithionite extractable Fe, total, and acid ammonium oxalate-S 109 Table 5.4 Average metal concentration in two groups of samples, those with Hurst colour rating < 30 and colour rating > 30 115 Table 6.1 Sequential extraction scheme 132 Table 6.2 Summary of analyses from sequential extraction analyses of the silt+clay fraction. 140 Table 6.3 Relative amounts of sequential extractable metals (%) 142 Table 6.4 Summary of significant correlations for solution pH s i c l with pools of metals from the sequential extraction scheme 147 Table 6.5 Comparison of "red" and "non-red" samples using a Mann-Whitney U-test 173 vii Table 6.6 Comparison of "red" samples from trench A and C using a Mann-Whitney U-test. 173 Table 7.1 Some characteristics of silt+clay fraction from samples selected for the wet-dry and batch experiments 182 Table 7.2 Description of reference materials used in wet-dry cycling and batch experiments. 182 Table 7.3 Classification of metals based on the cumulative metal release curves described in Figure 7.6 199 Table 7.4 Rates of release for Cu, Fe, S042', and Zn during batch experiments from sample 9 in deionized water and citric acid solution buffered at pH 2.2 200 Table 7.5 Distribution of selected aqueous species and saturation indices from selected samples from the 1st and 17th wet-dry cycle, calculated using MINTEQA2 205 Table 7.6 Distribution of selected aqueous species and saturation indices from selected samples on day 0.04 and 153 of the batch experiment, calculated using MINTEQA2.... 206 Table 7.7 Comparison of cumulative metals release data (mg/g) from the two dissolution procedures 224 V t i i List of Figures Figure 2.1 Stages in the formation of acid rock drainage generation 29 Figure 2.2 Biogeochemical model for the precipitation of various ferric iron minerals in mine drainage ochres ;. 31 Figure 3.1 Location of the Gibraltar mine site 55 Figure 3.2 Sampling locations at the Gibraltar mine site 58 Figure 4.1 Colour photo from trench A 68 Figure 4.2 Colour photo from trench C 69 Figure 4.3 Calculated mobility index. The relative mobility of each element expressed as the ratio of the relative average concentration (normalized to Ti concentration) in each trench to the average concentration in the non leached, least weathered trench 81 Figure 4.4 Comparison between total Fe and Hurst colour rating for the whole fine earth and silt+clay fraction 87 Figure 4.5 Relationship between depth in trench A vs. Hurst colour rating and Fesjci 88 Figure 5.1 Spearman rank correlation coefficients for AAO and CBD extractable Al, Fe, Cu from the fine earth, sand, and silt+clay fractions 99 Figure 5.2 Spearman rank correlation for metals analyzed from AAO and CBD extractions.... 101 Figure 5.3 Relationship between AAO extractable Si and Al from the silt+clay fraction 104 Figure 5.4 Comparison of AAO and CBD extractable metals from each trench 106 Figure 5.5 Extractable Fe concentrations plotted against silt+clay fraction colour rating 112 Figure 5.6 Comparison between each trench, of the amount of metal extracted from samples with low Hcr s i ci 118 Figure 5.7 Comparison of extractable and total Al, Fe, and Cu concentration plotted against depth in trench A 120 Figure 5.8 Comparison of extractable and total Al, Fe, and Cu concentration plotted against depth in trench C 121 Figure 6.1 Geochemical reservoirs affecting drainage chemistry from waste rock (modified from Morin etal., 1995) 131 Figure 6.2 Mass % extracted or loss-on-extraction (LOE) for mineral references from sequential extractions 137 IX Figure 6.3 Distribution of mass loss-on-extraction (LOE%) from each extraction vs. depth in each trench 144 Figure 6.4 Maximum, minimum, and mean metal concentration in each trench: Al Fe, Cu, S042\146 Figure 6.5 Summary of multiple comparison tests between extractable metals from each trench. 148 Figure 6.6 Total extractable S as S042" vs. total S (Leco) in each trench 157 Figure 6.7 Saturation indices for various minerals vs. depth in trench A 161 Figure 6.8 Saturation indices for various minerals vs. depth in trench C 162 Figure 6.9 Composition of water extraction solutions relative to the stability of common Fe minerals from acid mine systems 165 Figure 6.10 Composition of water extraction solutions relative to the stability of common Cu minerals from acid mine systems 167 Figure 6.11 Composition of water extraction solutions relative to the stability of common Al minerals from acid mine systems 168 Figure 6.12 Extractable elements (mg/kg) with significant Spearman rank coefficients vs. Hurst colour rating of the silt+clay fraction 170 Figure 6.13 Total S vs. H 2 0 extractable S 171 Figure 7.1 Solution quality during the wet-dry cycling experiment 187 Figure 7.2 Plots of Al, Ca, Cu, Fe, and S042~ dissolution from the wet-dry cycling experiment. 189 Figure 7.3 Solution quality data for samples 2, 9, 22, and 27 from the batch experiments 191 Figure 7.4 Cumulative Ca, Cu, Fe, and S042" released from sample 9 and 27 during the batch experiment 193 Figure 7.5 Cumulative Al, Ca, Cu, Fe, and S042" released from sample 9 plotted against log-time. 195 Figure 7.6 Typical curves for cumulative metal release plotted against log-time 196 Figure 7.7 Total soluble Al concentration (mg/L) determined in solutions from the batch experiment and speciation vs. pH in solutions 209 Figure 7.8 Total soluble Fe concentration (mg/L) determined in solutions from the batch experiment and speciation vs. pH in solutions 210 Figure 7.9 Saturation indexes vs. pH for different Al mineral phases based on thermodynamic data from the geochemical model MINTEQA2 (1991) 212 Figure 7.10 Saturation indexes vs. pH for different Fe mineral phases based on thermodynamic data from the geochemical model MINTEQA2 (1991) 215 x; Figure 7.11 Saturation indexes vs. pH for different Cu mineral phases based on thermodynamic data from the geochemical model MINTEQA2 (1991) 219 Figure 7.12 Saturation indexes vs. pH for different Si mineral phases based on thermodynamic data from the geochemical model MESJTEQA2 (1991).\ 221 xL A C K N O W L E D G E M E N T S In completing this dissertation, I have received support and assistance from numerous people. First, I would like to gratefully acknowledge the financial support from the BC Acid Rock Drainage Task Force, the MEND program, the National Research Council of Canada , and the personnel at the Gibraltar mine site. My dissertation committee deserves a special note insofar as they have always prompted me to see my research problems in ways that were not immediately obvious to me. In particular I thank my research supervisor, Dr. Les Lavkulich, who was always positive and considerate, and provided me with every opportunity to succeed. I consider him a friend, and will always remain grateful for all his support, guidance, encouragement, and effort on my behalf. Thanks also go to Drs. H. E. Schreier for his perspective and guidance, and W.A. Price who never let me forget "the forest beyond the trees". I also acknowledge the contributions of Drs. R. Lawrence, and L. Lowe. I thank all the students and technicians that have passed through the Pedology Lab for their support, companionship, and invaluable discussions. To my office-mates, I will always smile as I remember the laughter, complaining, cheering, and swearing we shared. Inherent to the completion of my dissertation has been the support of my family and friends. I owe the most to Vila, without whom I would not have begun this journey. I humbly thank you, for the endless support, patience, reassurance, and love. I thank you. xiii Ch.l-Introduction 1. Introduction /./ General Introduction Mining activities impact air, land, and water environments. Release of particulates in stack emissions from smelters has been demonstrated to have an impact on vegetation many kilometers downwind. Wind blown dust from crushing, milling, and transportation can also be a problem. Land disturbance caused by mining in BC (past and present) covers approximately 75,000 ha that is roughly one-quarter the area of the Greater Vancouver Regional District (Mining Association of BC, 1991). Disturbance occurs in many ways including road building and usage, pit construction, and waste storage/disposal. Water pollution from mining can originate from a number of sources including erosion and siltation from waste dumps and embankments, nitrates from blasting, flotation chemicals, leach operations, mine seepage and failure of detention ponds and structures. Of particular concern is the problem of acidic drainage and increased metals mobility. The greatest environmental challenge in the mining industry today is addressing acidic drainage (Filion and Ferguson, 1990) and metal leaching. The term acid rock drainage (ARD) is used here in preference to acid mine drainage since the processes are not necessarily confined to mining activities. Natural acid generation occurs wherever sulphide-bearing rock is exposed to air and water (Koyanagi and Panteleyev, 1992), however, it frequently occurs as a problem in mining operations. Drainage exiting a site may not be acidic due to neutralizing processes occurring on-site, but can still be contaminated with other constituents (e.g. metals and sulphate) and remain a problem. 1 Ch.l-Introduction ARD can be described as acidic contaminated drainage resulting from oxidation and leaching of sulphide-bearing rocks when exposed to air and water. A shorter definition would be the inorganic pollution due to mining activities (Paine, 1987). Generally, contaminants associated with mine waters are elevated levels of sulphate, nutrients, radionuclides and metals. Contaminated neutral pH drainage may result from leaching of sulphide-bearing rocks if there is abundant CaC03 or other acid-neutralizing minerals. Regardless of the definition, contaminated drainage (ARD or neutral pH) waters are non-compliant with regulatory requirements and cause adverse environmental impacts. In BC, much of the concern associated with mine drainage is related to metal leaching from waste rock dumps. Vast quantities of waste rock are produced by the mining industry and many can be a source of ARD. Waste rock is produced from bedrock surrounding and overlying the ore body and is generally stored above ground during open pit mining. A recent survey determined that over 50% of the acid-generating or potentially acid generating waste rock in Canada (420 Mt in BC and 740 Mt in Canada) is located in BC, and is associated with a few large open pit mines (Feasby and Jones, 1994). Weathering1, by physical or chemical processes, of waste rock results in the dissolution/solubilization of minerals leading to increased metal loading in drainage waters. Once started, metal leaching and/or ARD generation is difficult to stop and is usually Weathering is defined as " ...physical and chemical changes produced in rocks, at or near the Earth's surface, by atmospheric agents.". 2 Ch. 1 -Introduction managed by treatment of the drainage waters. Attempts to minimize and control the level of pollutants exiting in drainage waters, as well as improving the aesthetic value of the land, involve on-site reclamation. One of the objectives of mine reclamation is to develop a vegetative cover and provide for a system where the cover is self-perpetuating, with minimal maintenance and input, and one that contributes no more than "acceptable" levels of contaminants to the drainage water environment. As such we need to understand processes of pedogenesis occurring in the waste rock (i.e. mine waste -> protosoil -> soil). Environmental problems should not cloud the contribution the mining industry makes to society. The mining and energy industry contributes a combined 9% of the provincial Gross Domestic Product and over $2 billion (almost 12%) of the provincial tax revenue, net revenues of approximately $3 billion, and supported approximately 30,000 jobs in 1995 (Price Waterhouse, 1995). Millions of dollars are spent each year to mitigate the ARD generated. The public, industry, and the government have targeted ARD as a source of pollution. In Canada, the cost of treating ARD generating sites has been estimated at between $2 to 5 billion (Feasby and Jones, 1994). Release of untreated ARD from mining activities is a concern because contaminant levels may pose a danger to the environment and humans. Contamination could have a devastating impact on recreational activities, drinking water supply, food chain structure, fisheries and agricultural land in the floodplain. As one example, Wilkes (1987) estimated a loss of $4.3 million per year if raw acid mine drainage was released uncontrolled into the Bulkey River near the Equity Silver mine in Houston BC. Chemical and physical changes in 3 Ch.l-Introduction freshwater ecosystems (from ARD) can lead to physiological (toxicity), behavioural (avoidance), and community structure changes in fish and benthic populations (Moore et al, 1991; Short et al, 1990; Wilkes, 1987; Katz, 1969). ARD-polluted areas may act as essentially a physical barrier for fish that venture upstream for food or to spawn. One area of intense research is the prediction of drainage quality from waste material (i.e. waste rock). A thorough understanding of the hydrogeochemistry of waste sites and the mineralogy of reaction products are crucial elements of this work (Filion and Ferguson, 1990). Although we know much about the chemical and biological processes leading to acid mine drainage in mine waste (i.e. rock dumps), in reality site-specific differences (i.e. geology, mineralogy, waste materials handling, climate, etc.) are large. Thus, the development of reliable long term models for mine drainage is presently in its infancy (Morin andHutt, 1994; Perkins etal, 1994). One aspect of ARD research that is poorly understood is the nature and role of weathering products stored/retained within a rock pile. Secondary weathering products or neoformed minerals may be formed and the kinds depend on pore water chemistry and microsite conditions. Stored weathering products occur mainly as precipitated secondary and oxidation minerals. As weathering occurs secondary mineral phases form that have different characteristics than the original primary minerals. As the quantity of these neoformed minerals increases they begin to control the reactions that occur at surfaces and thus are an important component to mine water quality prediction. Many weathering products will be 4 Ch. 1-Introduction found as coatings on surfaces in the rock pile or as re-precipitated minerals and can be considered "stored" until microsite conditions allow for dissolution and transport. Under constantly changing conditions, secondary weathering products will be metastable and will remain within a rock dump in an unknown quantity and be released at a rate determined by site-specific conditions and geochemistry. Understanding the role of secondary weathering products will help explain the dynamics of many metals that may contribute to ARD and general water quality. There has been limited research on examining the nature of secondary weathering products (WP) stored in rock dumps. This research investigates the chemical stability of stored weathering products (secondary and oxidized phases) in waste rock and examines their role in controlling the release of metals from rock dumps by using a pedogenetic approach to waste rock and secondary weathering products. The aim. of this research is to enhance our understanding of the stored weathering products by characterizing and identifying the various precipitated phases, examining their relationships to morphological features, and to study their stability and dissolution behavior under longer term leaching events. The fate of stored weathering products is determined by a complex series of reactions, involving factors such as pH, oxygen concentration, and rate of flushing. Little is known about the composition or the long term meta-stability of stored weathering products. Because iron-containing minerals (e.g. pyrite and chalcopyrite) are usually present in potential ARD sites and oxidize to give distinctive colours under different environmental conditions (weathering) and in different mineral assemblages, morphological features (i.e. colour) may 5 Ch.l-Introduction be useful as a field indicator of weathering intensity and secondary weathering product mineral assemblages. 1.2 Objectives The objective of this study is the identification and investigation of the composition and re-dissolution of stored weathering products from an acid-generating rock dump. Research questions to be addressed are: 1) What is the chemical and mineralogical composition of samples taken from zones distinguished on the basis of observed differences in morphological properties and treatment of a rock dump? 2) What is the geochemical distribution of metals/elements within these observable zones and differing areas of a rock dump? 3) What is the potential for the dissolution of metals from stored weathering products under different conditions? These research questions are addressed through a series of chapters. Chapter 2 presents a general literature review discussing weathering, waste rock dumps, acid rock drainage, and types of weathering products. Chapter 3 describes the study site, surrounding area, and the Gibraltar rock dump sampled for this study. An underlying theme of this work will be the examination of the potential value of morphological features to describe observations from the field and the use of morphology to understand and explain processes that may have occurred. Chapter 4 describes sample selection and addresses the first research question. 6 Ch. 1-Introduction The second research question is addressed in chapter 5 and 6 using selective dissolution analysis and sequential extractions. The third question on metal dissolution is addressed in chapter 7 through two longer-term dissolution experiments. 7 Ch.2-LiteratureReview 2. Literature Review Generally, natural mineral soils form from parent materials that are accumulating over relatively long periods of time as a consequence of geological processes. As a result exposure of minerals to oxidative processes, water and co-evolution of the biotic component begins immediately and proceeds gradually over time, including the period of formation of the parent material. Thus, as the parent material is being formed, the soil is gradually changing in relation to the environment of formation. Mine wastes accumulate relatively rapidly as a result of human activity, thus mine wastes have not been exposed to gradual changes and modifications and as such are incipient parent materials. They do not, therefore contain chemically altered minerals nor associations with biologic agents, except for sulphur bacteria. Nevertheless they may be considered proto-soils. (i.e. they are beginning to form natural soil material). The primary difference between soil and mine waste rock is the lack of organic matter and fines in the mined material. Since mine wastes may be considered incipient or proto-soils, the minerals in the waste are similar to geologically formed minerals rather than the high surface charged (electrically) secondary minerals found in natural soil. New surfaces and new minerals are formed during the weathering process of mined material often leading to ARD. Little is known about the weathering characteristics of natural soils affected by ARD. Literature from several areas of studies including acid sulphate soils and leached outcrops may be of particular value in relation to this study because of similar conditions (i.e. low pH and high leaching) and the formation of residual weathering products in an 8 Ch.2-LiteratureReview acidic environment. ' There is substantial literature regarding the mobility and redistribution of iron and aluminum released by natural weathering in soils (e.g. podzolic soils), but little is known about the dynamics of metals that may result in undesirable impacts on biota upon entering the aqueous environment. The formation and the dissolution of residual weathering products can affect the composition of drainage waters associated with mine wastes. Soluble residual weathering products can act as a reserve for metals and acidity during dry periods to be released during rainfall events. Less soluble or metastable residual weathering products such as iron oxyhydroxides may incorporate aluminum and other metals (e.g. iron, copper, zinc, etc.) through a variety of processes thus acting as a mechanism for attenuation. 2.1 Mine Waste Rock Dumps 2.1.1 construction methods Waste rock is rock material that must be removed in order to gain access to an ore body. During open pit mining, which is used when orebodies are shallow and massive, waste rock is generally stored above ground. Typical stripping ratios (ratio of waste to ore) for open pit mining are near 3:1. Some waste rock is also generated during the initial stages from underground mining operations. Low concentrations of ore in waste rock generally make economical extraction by conventional mining methods (i.e. froth flotation) not possible. The size and shape of a waste rock dump reflect the scale of and topography near each mining operation. Waste rock is composed of silt, sand and gravel grade detritus. 9 Ch. 2-Li teratureRe view Typical physical characteristics of waste rock dumps generating acidic drainage are shown in Table 2.1. Table 2.1 Physical properties of waste dumps producing acid rock drainage (taken from Ritchies, 1994). Property Typical Range Units Height 20 2 to 150 m Area 30 0.1 to 150 ha Density 1500 1300 to 1900 kg/m3 Sulfur content as pyrite 2 0.5 to 30 % w/w Temperature -7 to 65 ° C Water content 5 to 25 % v/v In British Columbia, there are over 2 billion tonnes of waste rock occupying 900 ha of land (Feasby and Jones, 1994). The method selected for rock dump construction is dependent on the geography of the site, equipment being used, and the physical and chemical properties of the waste. Morin et al. (1991) describes four common methods used to construct rock dumps as (1) end-dumping, (2) push dumping, (3) free dumping, and (4) drag-line spoiling. Different construction methods lead to some segregation of dump material and some layering (Ritchie, 1994; Nichols, 1987). These features may influence water and gas-transport properties in waste rock piles. Many dumps are constructed by end-dumping which involves dumping of rock over the dump face. Generally, end-dumping of waste rock results in the segregation of particles 10 Ch. 2-LiteratureReview and layering in a dump (Ritchie, 1994). Segregation is a function of size and density, with coarser dense materials at the base and finer lighter particles near the crest (Klohn Leonoff, 1991). Nichols (1987) performed some simple end-dumping simulation experiments and identified three distinct zones of segregation: (1) near the top 10-15% of the dump, fines were concentrated compared to coarser fragments, (2) the zone between the slope to the toe where the material tended to be well-graded and evenly distributed, and (3) the area at the toe where the dominant fraction was composed of coarse fragments. Dumping of greater amounts of fines on a shorter slope led to less segregation (Nichols, 1987). Push-dumped construction involves dumping of rock material from trucks then leveling of the waste by tractor and shovel. Push dumping leads to a greater proportion of coarse fragments throughout the waste rock pile. Waste rock fragments tend to be less segregated, and coarse fractions pushed over the slope crest roll past the toe of the dump. Nichols (1987) determined that a greater proportion of the coarse fraction rolled beyond the toe when end-dumped (70%) compared to push dumping (45%). One reason for this was attributed to the angular momentum a rock achieved by being "dumped" from a truck. Free dumping involves depositing waste rock in small piles on the surface of a dump, grading the material, and compacting in approximately 2 m high layers (lifts) (Morin et al., 1991). There is little segregation of material and much greater compaction compared to the end and push-dumping methods. Waste from dragline spoiling is deposited on the land surface without construction of lifts and minimal compaction. There is minimal segregation of particles in this method. 11 Ch.2-LiteratureReview 2.1.2 moisture regime Microenvironmental conditions, such as in rock microfractures and acid-generating hotspots, in dumps play an important role in determining the formation and dissolution of secondary weathering products. Microsite conditions are controlled by the ability of rock piles to retain and transmit water (i.e. particle size of rock in the pile). In the unsaturated zone of waste rock dumps, pore water is retained as a surface film on the rock or in cracks or voids, which are areas where oxidative reactions occur (MEND, 1992). The aqueous phase in rock piles is charged with various solubilized elements as a result of interactions with solids leading to changing solution chemistry (mineral precipitation/dissolution). Factors controlling weathering processes such as pH, Eh, and leaching will determine if a mineral goes into solution (solubility), the rate of solubilization (kinetics), and formation of secondary products. Factors controlling waste rock dump hydrology fall into two categories: (1) physical properties, and (2) chemical properties (Table 2.2). Other factors such as density of explosive placement, dump truck haulage, dumping and dozing, natural settling, and natural variations in geology can affect the heterogeneity of rock dumps. Waste rock dumps are heterogeneous piles of rubble which tend to exhibit a high initial permeability depending upon the method of construction and amount of coarse particle sizes (Whiting, 1981). Except near the base, conditions in a waste rock dump are generally unsaturated, with estimates of up to 25% moisture (Ritchie, 1994). A large proportion of waste rock by mass and volume has a diameter greater than 20 cm (Brodie et al., 1991). In 12 Ch.2-LiteratureReview BC, a range of 75 - 84% of the material on terraced rock pile benches at porphyry Cu-Mo mines is greater than 2 mm in size (Murray, 1977). The typically coarse nature of waste rock leads to high permeability and is conducive to repeated wetting and drying of rock surfaces. Table 2.2 Factors affecting mine waste dump hydrology (Whiting, 1981). Physical Chemical Other Stratification pH control solution application Channeling precipitation/hydrolysis pollution control Segregation temperature precipitation rates Sorption alteration evapotranspiration Foundation oxidation Permeability solution type Construction Areas with high quantities of fines (< 2mm), can expect to have greater water retention capabilities and lower permeability than areas with cobbles and boulders. Surface material at the surface of most waste rock dumps has an infiltration rate of approximately 1 x 10"8 m/s with a saturated hydraulic conductivity about 10"4 m/s (Ritchie, 1994). A single value for hydraulic conductivity is unlikely to be representative of an entire waste rock dump due to variations in internal structure caused by variations in particle size, construction techniques, and formation of precipitates. Processes such as channeling and stratification are considered to be important considerations (Whiting, 1981). Conceptually, the two processes as described by Morin et al. (1991) are: (1) channeling - the presence of high permeability 13 Ch.2-LiteratureReview flow channels which control and concentrate the migration path of water (i.e. preferential flow through paths of least resistance), and (2) stratification - the presence of low permeability layers causing water to flow with greater ease horizontally. Newman et al. (1997) investigating preferential flow in layered, unsaturated waste rock indicate that although coarse material has a higher saturated conductivity, the layers of fine grained material may well be the primary conduits for moisture transport through a rock dump. This can be explained by the dramatic decreases in water retention and in hydraulic conductivity in a coarse material, in comparison to the finer material, as moisture content decreases in the various layers. Preferential flow tends to occur in layers of fine material at lower moisture contents, and can only occur in coarse layers when moisture increases to a site-specific critical level. Both channeling and stratification are important hydrologic control features of rock dumps. Channeling may be the dominant process for the transmission of water through rock piles. Although probably site-specific, the proportion of mine rock flushed by flowing water is assumed to be in the range of 5-20% (Morin and Hutt, 1994) although the true value is unknown. Staining of channel surfaces may be indicators of preferential water movement (Schoeneberger et al., 1992). Precipitates depositing in flow paths may alter hydrologic flow over time. Investigating the effect of solution and solid phase chemistry on water movement in spoils, Evangelou et al. (1982) found that salt build up in solution percolating through spoil is inversely related to hydraulic conductivity. This is likely the result of physical and chemical disruptions in the pore structure, such as the formation of precipitates. In core 14 Ch.2-LiteratureReview leaching experiments using 5% H2SO4, reaction products of biotite have reportedly expanded up to 30% in volume (Earley et al., 1990). Grussification or volume expansion leading to increased fracturing could lead to significant changes in rock dump permeability. The presence of low permeability layers in mine waste may result from cemented layers. These layers may be similar to duripans reported in soils. In rock dumps these layers may have important implications to the long-term stability of dumps and reclamation efforts. Kent and Johnson (1993) and Dawson et al. (1995) indicate a greater potential for slope instability when there are occurrences of reduced pore-water pressures in fine-grained layers of mine waste. Formation of secondary structures such as hardpans can alter the hydraulic conductivity of a dump by forming conduits for, or barriers to, flow. Transport of fine particles by migrating water may also be important in altering hydraulic conductivity. Few cases of hardpans have been reported in rock dumps (Lin and Herbert, 1997; Lister, 1994). Lin and Herbert (1997) investigating a 50-year-old rock dump in Sweden describe an accumulation zone in a profile of an excavated trench. This Fe-Ni accumulation zone acted as a barrier to downward displacement of the weathering front and to the accumulation of dissolved metals. Lister (1994) reported the occurrence of an indurated horizon in rock dumps at the Island Copper Mine near Port Hardy. She describes the indurate layer as an "oxidation front" in the pile with relatively fresh unoxidized material below. These layers, reported at depths of 15 and 30 cm, were not sampled, thus physical and mineralogical data describing this horizon was not reported. Cemented subsurface horizons have been also been 15 Ch.2-LiteratureReview reported in mine tailings (Blowes et al., 1991; McSweeney and Madison, 1988; Kennedy and Hawthorne, 1987). When the concentration of soluble constituents exceeds a solubility product, precipitation of an authigenic phase may occur. Crucial factors governing precipitation of minerals are pH, Eh, degree of oxidation, moisture content and solution composition (Nordstrom, 1982). In the rock dumps at Gibraltar mines, the controlling factor may be the extremely low pH and high sulphate activity from the acid-leaching process. Precipitation of secondary products along channels and microfractures may affect or be indicative of past waterflow. Studying felsic gneiss saprolites, Schoeneberger et al. (1992) found that Fe and Mn were indicative of past preferential water movement. Colours observed on fractures were controlled by the relative amounts of hematite, goethite, and a Mn-oxide coating (Schoeneberger et al., 1992). McSweeney and Madison (1988) found that gypsum and Fe oxides and hydroxides dominated within inter-aggregate pores and hydrated Fe-sulphates dominated within intra-aggregate pores in > 60 year old mine waste. Mineralogical transformations were determined by variations in moisture, porosity and redox chemistry of the waste. In addition, grain boundaries, grain size, micro- and macrofracture size and continuity of rocks and geologic units all contribute to microsite conditions. 2.2 Weathering Weathering can be described as the natural processes in soils and on rocks causing physical and chemical or mineralogical changes (Brady,1990). Most rocks and minerals are 16 Ch.2-LiteratureReview relatively stable in situ in their stratigraphic column, but once displaced by natural or anthropogenic processes (such as in mining), pressure changes and exposure to weathering agents lead to physical and chemical changes. Weathering agents include wind, water, solar energy, air, and the biota. Waste rock weathering at mine dumps may lead to contaminated drainage and is thus an important factor to consider when studying the environmental implications of a mine site. The minerals found at mine sites are more dynamic than in more neutral pH soils in that the acidic conditions produced by sulphide oxidation attack existing minerals and rapidly change surface characteristics. Waste rock weathering determines the potential for acidic drainage, metal leaching, surface area subject to oxidation and leaching by creating fresh surfaces and fractures, and production of more fine particles (MEND, 1992). Mechanisms controlling metal concentration in mine drainage are closely related to the composition and the weathering of the minerals, release of metals from the overburden and waste, and the metal adsorption capacity of the solids in the system. Weathering occurs because geologic material (i.e. waste rock) is not thermodynamically stable in the surface environment. Evidence of natural rock weathering is shown by the presence of soils and saprolites. As weathering reactions proceed, changes occur in mineralogy and thermodynamic properties of the material. Minerals considered resistant to weathering appear virtually unaltered not because there are no changes, but due to the exceedingly slow rate of change. Weathering reactions take place on mineral surfaces and most actively in cracks or 17 Ch. 2-LiteratureRe view crevasses; therefore, understanding changes occurring in mineralogy and chemistry helps predict speciation and secondary products. Secondary products can be considered any product formed from weathering reactions which may include amorphous gels, saprolites, fine-grained metal oxides and ultimately, soils (Birkeland, 1984). Smectites and vermiculites are often indicators of weathering products. (Weathering products and secondary products are used as synonyms.) Goldich (1938) stated that the chemical weathering of rocks depends on the susceptibility of the individual minerals to change. Although mineral weathering is dependent on numerous external (e.g. water and solar energy) and internal (e.g. crystal defects) factors , weathering processes are ultimately described by their thermodynamic properties. Application of thermodynamics to weathering requires two assumptions to be made: (1) reactions that occur are natural (i.e. controlled by natural laws), and (2) reactions are reversible and spontaneous on an infinitesimal time scale. The tendency of any reaction to occur is governed by the free energy of the mineral (i.e. Gibbs free energy or G). The lower the free energy of an ion, element, or mineral, the greater the stability. When minerals go into solution, the energy of hydration is released, and its free energy decreases, which is why water is such an important weathering factor. The lowest state of free energy attainable by an ion would be at infinite dilution. The free energy of the mineral can be related to the solubility product in water or slightly acidic conditions (K s p), the standard enthalpies or heats of formation (H°), the entropy of a system (S°), the standard cell potentials (E°), and reaction kinetics or rates. 18 Ch. 2-Li teratureRe vie w 2.3 Weathering Processes Weathering is generally divided into two basic processes: (1) physical (disintegration) and (2) chemical (decomposition) (Brady, 1990; Birkeland, 1984). Each process can be further broken down into a number of mechanisms or reactions. Physical processes breakdown rocks into minerals and chemical processes lead to decomposition and subsequent formation of altered or new minerals. Both processes are active in waste rock. Detrital rock grains with stable and resistant primary minerals, secondary weathering products and soluble materials are products of weathering (Brady, 1990). Physical weathering or disintegration is the mechanical process of breaking down rocks as a result of external stress. Rocks break into smaller particles and thus surface area. Generally decreasing particle size or increasing surface area leads to greater chemical reactivity (e.g. sands vs. silts vs. clays) and exposure of fresh mineral surfaces. Physical weathering mechanisms discussed in the literature are: (1) thermal expansion or contraction^'.e. temperature), (2) freeze-thaw , (3) erosion, and (4) plant, and to a lesser extent, animal influences (Brady, 1990; Birkeland, 1984; Wilson and Jones, 1983; Carroll, 1970). These mechanisms are most pronounced at the earth surface where the agents of weathering are most active. The result of physical weathering or disintegration is the formation of a loose granular mass of mineral material or saprolite. Chemical weathering processes are among the most fundamental natural processes operating on the surface of the earth and control processes associated with metal leaching and 19 Ch.2-LiteratureReview acid rock drainage from mine sites. Chemical weathering or decomposition has been divided into 5 basic processes: (1) solution, (2) hydration, (3) hydrolysis, (4) oxidation - reduction, (5) and, acidification (Brady, 1990), the most important being hydrolysis, hydration, and oxidation (Nortcliff, 1988). Chemical weathering of rocks and associated primary minerals is generally a slower process than pedogenic weathering. The primary reason is that the surface area per unit mass of sample increases as particle size decreases (i.e. for a similar mass or volume of material, soil will have greater surface area than rock) (Carroll, 1970). Materials with smaller particle size provide more specific surface area for chemical reactions to occur and generally weather faster. Dissolution of the most soluble minerals and precipitation of the least soluble minerals forming as authigenic phases will tend to control the inorganic composition in the aqueous phase (Chesworth, 1992). Chemical weathering of minerals is primarily the result of the dissolution of solids by water (Bohn, 1985). The presence of water in thin films around surfaces provides a medium for the most soluble phases to dissolve, which may lead to metal mobilization. Alkalis and alkaline earth metals (Na, K, Ca, and Mg), found in many minerals, are easily dissolved and leached in the presence of water. The role of water in active weathering is summarized in Table 2.3. Water acts as a reactant and medium during chemical weathering. All minerals and rocks react with water. Water has the ability to react with many minerals because of its high dielectric constant. 20 Ch. 2-LiteratureReview I -<-> 3 o -a J3 •8 2 C D C D > > s J a ed a S3 .3 C J cd ha .3 't/5 > cd u 21 Ch. 2-Li teratureRe view The solubility of solids can be categorized as being: (1) soluble (e.g. ionic salts such as NaCl), (2) sparingly soluble (e.g. carbonates such as CaCC»3 where other agents control the solubility), and (3) insoluble (usually expressed in terms of solubility products or values of K s p ) . Hydration is the incorporation of a water molecule by a substance or mineral usually resulting in a change in the properties of the material. For example consider the changes for CaS0 4: anhydrite gypsum CaS0 4 + H 2 0 —-> C a S 0 4 « 2 H 2 0 -for anhydrite; pK° r = 4.36, solubility (100°C) = 0.162 g/lOOmL -for gypsum; pK° r = 4.58, solubility (100°C) = 0.241 g/lOOmL Data from Ball and Nordstrom (1991) and Weast (1975). Hydration of anhydrite to gypsum increases solubility by 50% (by weight). Hydrolysis reactions are those which involve the splitting of water (i.e. H 20 = FT + OH") and incorporation of the hydroxide group into the product. Hydrolysis of iron and aluminum are the primary factors in the production and control of soil acidity (Brady, 1990). In acid mine waters, ferric (Fe3+) iron precipitates at sufficiently high pH through a hydrolysis reaction to iron hydroxide: Fe 3 + + 3H 2 0 — - » Fe(OH)3 + 3H + Reduction and oxidation (redox) reactions involve the transfer of electrons from reactant to products. Oxidation is the loss of electrons and reduction is the gain of electrons. 22 Ch.2-LiteratureReview In natural environments, the most important oxidizing agent (causes oxidation of another compound) is oxygen (O2) and the most important reducing agent (causes reduction of another compound) is carbon (C) (Manahan, 1994). In mine waste, the main oxidizing agents are O2 and Fe 3 + . Galvanic contacts between different sulphide mineral species can lead to the preferential oxidation of the more active sulphide (Mehta and Murr, 1983). Redox reactions are important in weathering for all transition elements (e.g. Cu, Mo, Mn, Co, Ni, Fe, etc.) and may indirectly affect the solution process. The initial reaction in the generation of acidity from pyrite is the oxidation of S: FeS 2 + H 2 0 + 7 / 2 0 2 FeS0 4 + Ff 2 S0 4 In soil systems, weathering is accelerated by acidity from C 0 2 and organic acids. Concentrations of C 0 2 are higher in soil than in the atmosphere due to biological activity, while decomposition of organic material produces organic acids (Brady, 1990). At mine sites with sulphide minerals, oxidation of sulphide phases will generate acidity contributing to weathering. Acidity from the various sources leads to the charging of water with FT1" and a decrease in soil water pH, and increased weathering rate (Stumm et al., 1985). The solubility of many metals (Fe, Cu,Ni, Zn, Pb, Al) tends to increase with decreases in pH (Baes and Mesmer, 1976). Another important reaction involved in chemical weathering is the effect of chelation. Elements do not exist in solution in isolation, but combine with ligands or chelating molecules. For example, organic matter (e.g. fulvic acids) can complex or chelate with certain elements and change their behavior in solution by altering properties such as 23 Ch. 2-Li teratureRe view solubility, and thus mobility and total dissolved concentration. The formation of insoluble complex compounds removes metal ions from solution. In soils, the formation of soluble metal-ligand complexes makes the metal more mobile (e.g Fe 3 + complexation with siderophores). In the presence of complex forming ligands, the concentration of the "free" metal ion may be significantly smaller than the total dissolved metal concentration. 2.4 Mineral Stability Mineral weathering is an important process occurring on the earth surface. It is likely the most important process to buffer natural systems from anthropogenic acidification, for nutrient input for plants and animals, and affecting the distribution, development, and stability of agricultural and forest soils. Weathering studies for outcrops and soils have described mineral stability sequences, preferential element dissolution, and descriptions of mechanistic processes. Goldich (1938) proposed a mineral stability sequence essentially stating that minerals far removed from their formation environment (pressure and temperature of crystallization) tend to be least stable. Factors affecting mineral stability are: (1) degree of linkage to Si02 tetrahedral (the greater the degree of linkage, the lower the internal charge imbalance), (2) presence of oxidizable cations (Fe2 +, Mn 2 + ) (oxidation will lead to a change in ionic size and crystal stability), (3) presence of empty positions in lattice (physical instability and increased charge imbalance), (4) presence of foreign cations (isomorphous substitution), (5) surface area, and (6) nature of associated minerals (galvanic contacts and base status). These factors 24 Ch. 2-Li teratureRe vie w are accounted for in Goldich's stability series (Bohn, 1985). The degree of silica (SiC»2) tetrahedron linkage influences the net charge per tetrahedral. The charge on a Si02 tetrahedron ( S i 4 + + O2" x 2 ) is 4". By increasing the linkage of the tetrahedra (i.e. increasing sharing of oxygens between tetrahedra), the charge per unit is decreased. This leads to greater charge stability, a lower requirement for balancing cations (e.g. Na + , K + , Ca 2 +) to neutralize excess negative charges, and a more tightly bonded structure. The presence of cations with more than one oxidation state (e.g. Fe(II and III) and Mn(TJ and TV)) in a mineral increases the potential for weathering. When a cation changes oxidation state, two events occur leading to changes in mineral stability: (1) its ionic radius changes and creates structural stresses within the mineral, and (2) the charge change affects unit charge of the mineral. When a mineral crystal forms, an ordered structure results. Weathering rate of a mineral depends on: mineral and crystal structure and composition, size, shape, perfection and the access of a weathering agent (water) and removal of weathered product (Oilier, 1975). Table 2.4 shows the stability of some common minerals and associated elements that will be released by dissolution. Rock weathering is more complicated than the weathering of the individual minerals. Factors such as rock porosity and permeability are important as they determine the ease of water entry and removal of weathering products. In natural systems, chemical weathering is often divided into two categories: (1) congruent, and (2) incongruent. 25 Ch.2-LiteratureReview Table 2.4 Relative stability of some common minerals associated with igneous rocks and their associated elements. Stability Mineral Dominant Elements Trace Elements Easily Weathered Olivine Hornblende Biotite Mg, Fe, Si Mg, Fe, Ca, Al , Si K, Mg, Fe, Al , Si Ni, Co, Mn, Li , Zn, Cu, Mo Ni, Co, Mn, Sc, Si, V, Zn, Cu, Ga Rb, Ba, Ni, Co, Sc, Li , Mn, V, Zn, Cu, Ga Moderately Stable Apatite Albite Orthoclase Muscovite Magnetite Ca, P, F Na, Al , Si K, Al , Si K, Al , Si Fe Rare earths, Pb, Sr Cu, Ga Rb, Ba, Sr, Cu, Ga F, Rb, Ba, Sr, Ga, V Zn, Co, Ni, Cr, V Very Stable Tourmaline Ca, Mg, Fe, B, Al , Si Li , F, Ga Quartz Si Congruent weathering or dissolution refers to complete dissolution of the reacting mineral phase without precipitation of a new phase and is assumed when using solubility product values. Incongruent solubility occurs when ions go into solution but a residue of the original compound remains or a new phase forms. 26 Ch.2-LiteratureReview 2.5 Acid Rock Drainage Chemistry and Stored Weathering Products The generation of acid rock drainage (ARD) in surface and underground mining operations results from the exposure of reduced sulphur minerals (particularly pyrite), to atmospheric conditions. The drainage waters from many metal and coal mines are frequently contaminated with all or some of the following: elevated levels of acidity, sulphate, total dissolved solids, and metals. The acidic water that results from sulphide oxidation is capable of weathering more minerals and releasing more metals. Sources of contaminated drainage are mine waste (tailings and rock), ore stockpiles and spent ore piles, pit walls (surface mining), and underground workings (underground mines). Most harmful to the environment is the high metals loading in the contaminated drainage (Wassel and Mills, 1983; Warner, 1971; Warnick and Bell, 1969). Sulphide minerals are ubiquitous in the geological environment and are found primarily in areas beneath a covering layer of soil and/or under a water table (Steffan, Robertson and Kirsten, 1989). Sulphides are considered acid-generating minerals. Although the majority of metal sulphides are iron-bearing, not all sulphide minerals are equally reactive (Knapp, 1987). Marcasite and pyrite have the same chemical formula but because they were formed under different conditions, the former is less crystalline than the latter and therefore is less stable and generates acid quickly (Pugh et al, 1984; Lowson, 1982). Other metal (CuS) and semi-metal (FeAsS) sulphides are more stable and thus less susceptible to weathering and acid generation. Fine-grained or amorphous sulphides are more reactive than those that are coarse grained. 27 Ch. 2-Li teratureRe view Acid generation at a particular site is the result of a complex series of reactions involving interactions between sulphide minerals (chalcopyrite and pyrite at the Gibraltar site), air, water, and bacteria. The capability of a particular sample to generate acid is a function of the balance between the quantity of acid-generating and acid-consuming minerals and their rates of reaction at a site. The most common acid consuming minerals are the carbonates (e.g. calcite - CaCC>3; siderite - FeCC>3; dolomite - MgCa(C0 3)2). Other minerals (e.g.; gibbsite - A1(0H)3; albite - NaAlSisOg; kaolinite - FLtA^SiiOg) can neutralize acidity (Broughton et al., 1992; Evangelou, 1983) but may not be effective because of their dissolution kinetics and buffering pH. Generation of acid in the microenvironment does not always result in contaminated drainage in the receiving aquatic environment but depends upon the rate of leaching and reactions along the flowpath which influence acid consumption, accumulation of oxidation or secondary products, solubility of metal species, and on-site treatment. Thus water draining from a site which has active sulphide oxidation could have a neutral pH and be relatively benign. The development of ARD is considered to be a 3-stage process involving both oxidation and hydrolysis reactions (Broughton et al., 1992). The various stages of the reaction can be roughly defined by the pH of the water in the microenvironment and time (Figure 2.1). During the initial stages of ARD generation, when sulphide minerals are initially exposed to the near surface environment, ferrous iron (Fe2+), sulphate and acidity are generated. The primary oxidant is oxygen. 28 Ch.2-LiteratureReview 0) 4 o H o E 1 Reactions in Stage 1 and 2 FeS 2 + 7 / 2 0 2 + H 2 0 -> Fe 2* + 2 S0 4 2" + 2H* Fe 2* + ' / 4 0 2 + H*-> Fe 3 + + ' / 2 H 2 0 Fe 3 + + 3 H 2 0 -> Fe(OH) 3 + 3 H + Stage 1 " ' plateau from mineral buffering at various pH values Stage 2 Stage 3 Reactions in Stage 3 Fe2* + V 4 0 2 + H* -> Fe 3 + + 72 H 2 0 _ FeS 2 + 14 Fe3* + 8 H 2 0 -> 15 Fe2* + 2 S 0 4 2 - + 16 H* Stage 1 chemical oxidation dominates pH > 4.5 , alkalinity present, little acidity elevated S 0 4 2 ' dissolved Fe precipitates Stage 2 increased biological oxidation pH ranges between 3 - 4.5 elevated S 0 4 2 ' increasing Fe3* low Fe3*/Fe2* elevated metals and increasing acidity Stage 3 biological oxidation very rapid p H < 3 elevated S 0 4 2 ' high Fe3* high Fe 3*/Fe 2 + high metals and acidity Figure 2.1 Stages in the formation of acid rock drainage generation. Drainage waters tend to have elevated levels of SO4 " and values of pH > 4.5 due to the buffering capacity of acid consuming minerals such as CaC03. Ferrous iron released into solution is oxidized to ferric iron, and in this pH range is precipitated as Fe(0H)3. Various sulphate minerals may precipitate if saturation is achieved (Ksp exceeded). As weathering proceeds and the availability of carbonate minerals decreases, conditions in the microenvironment decrease towards pH 4.5 (stage 2) and biological oxidation reactions become more important. Each pH plateau on Figure 2.1 represents the 29 Ch.2-LiteratureReview dissolution and buffering of an acid consuming mineral. During stage 2, as the acid consuming minerals or the buffering capacity of the system decreases, pH in the microenvironment drops and precipitated Fe3+-phases solubilize back into solution. Under these conditions and because of its increasing availability, Fe 3 + replaces oxygen in the oxidation of pyrite. At this stage of ARD generation, both chemical and biological oxidation reactions are occurring. During stage 3, Thiobacillus ferrooxidans, an acidiophilic aerobic chemotroph becomes metabolically active and catalyzes the oxidation of Fe 2 + . Bacterial oxidation of Fe 2 + is very rapid from pH 1.5-4 and has been reported to be several orders of magnitude greater than chemical oxidation, under optimal conditions. The dominating oxidation reactions are now controlled by biologically catalyzed oxidation. Elevated levels of iron (predominantly Fe 3 +), metals, sulphate and low pH characterize water in the microenvironment. The metals are dissolved from naturally occurring minerals in the surrounding rock as a result of the acidic conditions. The time scale for each stage may vary from days to years. The main factors that determine the rates of these reactions are: pH, temperature, amount of O2 gas in pore space, amount of O2 in water, degree of water saturation, activity of Fe 3 + (Fe 3 +/Fe 2 + redox couple), activity of bacteria , surface area to volume ratio of exposed sulphide, and activation energy required (Broughton et al, 1992; Pugh et al, 1984). Products of ARD (e.g. Fe 3 + , SO42", metals) formed in the microenvironment may be retained on rock surfaces in pore space or flushed from the reaction site and react elsewhere 30 Ch.2-LiteratureReview along the migration path or appear as contaminated seepage in the environment. Incongruent dissolution leads to the formation of authigenic minerals. Authigenic or secondary minerals will form under the appropriate conditions in the pore space or form as ochres upon entering the environment. For example, Fe 3 + may precipitate as Fe(OH)3 when pH > 4, but if pH < 4 and sufficient SO42" is present, jarosite KFe3(S04)2(OH)6 or schwertmannite FegOgCOFf^SCu may precipitate. Bigham (1994) proposed a biogeochemical model for the precipitation of various ferric iron minerals observed in mine drainage ochres which illustrates the complexity related to secondary mineral formation (Figure 2.2). In the vicinity of exposed sulphide mine waste, sulphate ions are present in abundant quantity as they are the stable end-product of oxidation, thus many secondary weathering products contain sulphate. - oxidation by T.ferrooxidans -pH 1.5-3.0 - [SO,] > 3000 mg/L - IK]. [Na|,... - oxidation by T.ferrooxidans - pH 3.0 - 4.0 - [S04] = 1000 - 3000 mg/L oxidation T.ferrooxidans 4 Fe2* (aq) + S042' (aq) 1 - oxidation by T. ferrooxidans or 02 -pH<6.0, IS04]< 1000 mg/L - pH > 6.0, [ H C O 3 ] 1. oxidation by 02 2. pH > 5.0 3. dissolved silica and/or high organic matter schwertmannite >pH, < S04 dissolution, reprecipitation reprecipitation lepidocrocite dissolution, reprecipitation goethite « ferrihydrite dissolution, reprecipitation Figure 2.2 Biogeochemical model for the precipitation of various ferric iron minerals in mine drainage ochres. 31 Ch. 2-LiteratureReview Secondary minerals are those that form within the waste material, typically from the precipitation of constituents originating from oxidation reactions (Jambor, 1994). Some metals may not form discrete phases and will be retained on the surfaces of other minerals through absorption or adsorption. The term stored weathering product when used here refers to all secondary weathering products retained in the system, regardless of the storage mechanism. The precipitation of weathering products onto rock surfaces influences its chemical and dissolution properties (including kinetics) by reducing the reactive surface area due to acid-generating and/or acid-consuming minerals (Nicholson et al., 1990). Stored weathering products can be considered an attenuation mechanism by storing/retaining metal contaminants in precipitates thus controlling metal concentrations in seepage. The most visually prominent weathering products in waste rock are secondary Fe-oxides (including hydrous oxides and oxyhydroxides) as evidenced by extensive red staining on rock surfaces. In a recent study, several secondary minerals were identified in a 50-year-old waste rock dump from Sweden (Lin and Herbert, 1997). In their samples, these authors identified goethite cc-FeOOH, jarosite KFe3(S04)2(OH)6, lepidocrocite y-FeOOH, sulphur, gypsum CaS04»2H20, and cristobalite Si0 2 . Hydrated Fe sulphates, assumed to be melanterite F e S C W ^ O , acted as an attenuation mechanism for small amounts of Ni, Cu, Zn, and Pb. Nordstrom (1982) observed a variety of hydrated iron minerals on the surface of weathering pyrite, and suggests that soluble hydrated sulphates form during periods of dry weather in the vicinity of oxidizing pyrite in unsaturated systems. Williams (1990) lists a 32 Ch. 2-Li teratureRe vie w variety of secondary metal sulphate minerals observed in association with sulphide oxidation. Many researchers have characterized weathering products from mining activities in a variety of mine water impacted environments, including groundwater (Herbert, 1995), pit lakes (Levy et al., 1997), seepage discharge (Bigham et al., 1996; Murad et al., 1994; Winland et al., 1991), wetlands (Karathanasis and Thompson, 1995); watersheds (Bayless and Olyphant, 1993); and streams (Brady et al., 1986). Investigations suggest precipitation of metals, coprecipitation and adsorption mechanisms are important attenuation mechanisms (Kwong and Van Stempvoort, 1994; Filipek, et al., 1987; Chapman et al., 1983). The most common precipitated weathering products are often identified as iron oxides such as lepidocrocite, goethite, ferrihydrite (Bigham, 1994; Murad et al., 1994), ferrous sulphates (Bayless and Olyphant, 1993), and oxyhydroxysulphates (Bigham, 1994; Murad et al., 1994). Mineralogy of iron precipitates in a constructed wetland was recently described as poorly crystalline ferrihydrite, lepidocrocite, goethite, and possibly schwertmannite (Karathanasis and Thompson, 1995). McSweeney and Madison (1988) identified minerals common to an acid sulphate weathering environment in >60 year old Pb-Zn metallurgical waste. Minerals identified within various horizons were: gypsum, quartz, ferrihydrite, goethite, siderite FeC03, barite BaS04, dolomite MgCa(C0s)2, jarosite, natrojarosite NaFe3(S04)2(0H)6, kalinite KA1(S04)2»11H20, rozenite, melanterite, and a mineral similar to alumino-copiapite MgAlFe(S04)H20. Hydrated Fe-sulphates were concentrated within intra-aggregate pore space and Fe-oxides/hydroxides dominated the inter-aggregate pores. The net result was the 33 Ch. 2-LiteratureRe view formation of a cemented horizon or "hardpan" above the regional water table. In mine tailings, Blowes et al. (1991) identified minerals in two types of hardpans located in tailings deposits at two mine sites in Eastern Canada. Gypsum and Fe(JJ) solids, primarily melanterite, were associated with one type of hardpan and Fe(ffl) minerals, goethite, lepidocrocite, ferrihydrite and jarosite, dominated the second hardpan. Jambor (1994) and Alpers et al. (1994) provide an extensive list of secondary minerals associated with mine tailings and water, many of which will likely occur in waste rock. 2.7 Storage Mechanisms for Weathering Products Materials released during weathering are either removed from the system in leaching water or react in the system to form new products (Birkeland, 1984). The most commonly observed weathering products in soils are clay minerals and hydrous oxides of aluminum and iron (Birkeland, 1984). Table 2.5 lists some trace elements that are coprecipitated with secondary soil minerals (Sposito, 1989). Stored weathering products are the new products formed and can be considered an attenuation mechanism. The most common attenuation mechanisms for weathering products in mine waste are: (1) authigenic or secondary minerals (amorphous and crystalline) formation, (2) co-precipitation, (3) metal retention by adsorption on to surfaces, or (4) pseudomorphic alteration of existing minerals. 34 Ch.2-LiteratureReview Table 2.5 Trace elements coprecipitated with secondary soil minerals (Sposito, 1989). Solid Coprecipitated trace elements Fe and Al oxides B, P, V, Mn, Ni, Cu, Zn, Mo, As, Se Mn oxides P, Fe, Co, Ni, Zn, Mo, As, Se, Pb Ca carbonates P, V, Mn, Fe, Co, Cd Illites B, V, Ni, Co, Cr, Cu, Zn, Mo, As, Se, Pb Smectites B, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pb Vermiculites Ti , Mn, Fe The first group has been discussed in the previous section, and will not be repeated here. Metal attenuation capacity of mine residue and overburden material is dependent on pH, ionic strength, the presence of competing ions, and mineralogy (Levy et ah, 1997). Coprecipitation is the simultaneous precipitation of an element with other elements by any occlusion and solid solution formation. Coprecipitation has been observed for secondary minerals associated with mine drainage waters. From goethite samples in acidic groundwater, researchers estimate that Al substitution into goethite ranges from 5.5 to 30 mole % (Herbert, 1995; Schwertmann and Taylor, 1989). Minerals in the alunite-jarosite group, are capable of incorporating numerous solid-solution elements, such as Pb, Cu, K, Na, and Ca (Alpers et al., 1994; Jambor, 1994). In a column study, Levy et al. (1997) showed jarosite in overburden was able to attenuate large quantities of Cu and Zn, likely through a solid-solution substitution process. 35 Ch.2-LiteratureReview Oxides, hydroxides and oxyhydroxides of iron, amorphous and poorly crystalline aluminosilicates are important adsorbents of metal cations (Rahner et al., 1993; Schultz et al. 1987; Kinniburgh et al., 1976). Adsorption is often described in terms of nonspecific and specific adsorption. Nonspecific adsorption occurs because there are unsatisfied charge requirements (usually negative) in minerals. This involves a diffuse-ion association and outer-sphere complexation. Electrostatic or coulombic forces lead ions in solution to form weak interactions with mineral surfaces. The strength of attraction is dependent on the ionic charge but covalent bonds do not form between ions and surfaces. Specific adsorption occurs when ions are more strongly associated to mineral surfaces through a ligand exchange reaction leading to the formation of a inner-sphere complex with structural O and OH groups. These ions bond covalently to mineral surfaces and are retained more tightly than in nonspecific adsorption. Specific adsorption can occur on a neutral, positive or negatively charged surface and can alter surface charge (Schwertmann and Taylor, 1989; McBride, 1989). Iron and other metal oxidation products from mine waste weathering can retain contaminants through adsorption. Adsorption by metallic oxides (including oxides, oxyhydroxides and hydrated oxides), especially Fe oxides, have been studied extensively in soils (Schwertmann and Taylor, 1989). Most evidence indicates metals are specifically adsorbed. For example, metal adsorption has a very small effect on adsorption of other cations suggesting that metal-bonding is site-specific (Leckie et al, 1980). In contrast, anion adsorption can have major effects on the adsorption of other anions indicating a more general 36 Ch.2-LiteratureReview overlap of site occupancy (Leckie et al, 1980). Adsorption sequences have been produced for various minerals and metals, but it is important to realize these are dependent on the degree of crystallinity and surface morphology of the adsorbent (McBride, 1989). The most studied group of minerals are the oxides of Fe and Al . The order of adsorption is generally shown with increasing pH. Kinniburgh et al. (1976) defined two selectivity sequences for metal cations on hydrous oxide gels of iron and aluminum. They reported relative cation affinity for the two gels using PH50 2 . Adsorption occurred at pH values at which < 1% of the cations would be hydrolysed. The two sequences reported are: most selectively adsorbed least selectively adsorbed on Fe gel Pb 2 + > Cu 2 + > Zn 2 + > Ni 2 + > Cd 2 + > Co 2 + > Sr2 + > Mg 2 + pH 5 0 3.1 4.4 5.4 5.6 5.8 6.0 7.4 7.8 on Al gel Cu 2 + > Pb 2 + > Zn 2 + > Ni 2 + > Co 2 + > Cd 2 + > Mg 2 + > Sr 2 + pH 5 0 4.8 5.2 5.6 6.3 6.5 6.6 8.1 9.2 In a review of existing data, Schwertmann and Taylor (1989) report that similar selectivity sequences have been found for hematite and goethite by numerous authors. 2 Kinniburgh et al. defined pH 5 0 as the pH at which 50% of the original cation is adsorbed. 37 Ch. 2-Li teratureRe vie w They summarized the findings in the following sequences: most selectively adsorbed least selectively adsorbed goethite Cu 2 + > Pb 2 + > Zn 2 + > Cd 2 + > Co 2 + > Ni 2 + > Mn 2 + hematite Pb 2 + > Cu 2 + > Zn 2 + > Cd 2 + > Co 2 + > Ni 2 + > Mn 2 + Investigating the feasibility of using freshly precipitated ferric oxyhydroxides to extract trace elements, Leckie et al. (1980) found that some elements were adsorbed in excess of 90% (by weight of the original). Affinity sequences for silica have been reported to follow the order (Dugger et al, 1964; Schindler et al, 1976): most selectively adsorbed least selectively adsorbed silica Pb2 + > Cu 2 + > Co 2 + > Zn 2 + > Ni 2 + = Cd 2 + > Sr2 + > Mg 2 + The factor most important to determining the extent of adsorption seems to be pH (Schwertmann and Taylor, 1989). Many researchers have reported that selectivity sequences are associated with a metal ions first hydrolysis constant (Schwertmann and Taylor, 1989; McKenzie, 1980), which indicates that the hydrolysed species is most preferred. Desorption studies show that some metals (Mn, Zn, Cu, Al) become more mobile as pH decreases (Davis et al, 1991). These results seem to agree with field observations (Filipek etal, 1987). Pseudomorphism is defined by Klein and Hurlbut (1985) as the process of a crystal or mineral alteration so that the internal structure or chemical composition is changed but the outward crystal form is preserved. Many minerals are known to be altered by pseudomorphic replacement. Blanchard (1968) discusses the importance of pseudomorphic replacement and 38 Ch. 2-LiteratureRe vie w classifies the many varieties associated with outcrops. Pseudomorphic alteration has been reported in soils and saprolites. Pseudomorphs (the external form) are formed by: (1) substitution - removal of the original material and simultaneous replacement by another with no chemical reaction between the two, (2) encrustation - a crust of one mineral coats existing crystals (the original mineral may be removed by solution later leaving the cast), and (3) alteration - a partial removal or addition of existing or new material. 1 Many alteration or secondary products are pseudomorphs of the original mineral (e.g. saprolites). Pseudomorphs of pyrite include pyrrhotite, hematite, chalcopyrite, arsenopyrite, marcasite, fluorite, calcite and baryte (Deer et al., 1992). In an acid sulphate soil of Texas, Carson et al. (1983) reported cubic and octahedral forms of jarosite which were pseudomorphs of pyrite. Eggleton et al. (1987) studying mineralogic and chemical changes related to basalt rock weathering observed iddingsite pseudomorphs after olivine (augite) and halloysite (tubular) and goethite after feldspar. Pseudomorphic replacement of existing minerals was initiated along fractures, cracks, and cleavage planes. 2.8 Factors affecting product formation Formation of secondary weathering products in most natural systems is a complex process due to the variety of different weathering environments and possibility of unique microenvironments in close proximity to one another. It has been difficult for researchers to determine the factors controlling the formation of new minerals because : (1) under natural 39 Ch. 2-Li teratureRe vie w conditions, weathering reactions are slow, (2) it is difficult if not impossible to reproduce natural conditions in a laboratory, and (3) authigenic minerals many not be part of the existing mineral-water equilibrium (i.e. may have formed under different conditions) (Birkeland, 1984). Factors affecting the formation of secondary weathering products often given in the literature include mineralogy (parent and secondary/type and distribution), Eh-pH conditions, the amount of leaching and the presence of organic matter (Birkeland, 1984), and for mine waters, sulphate concentration (Bigham 1994). The main role of parent material mineralogy is that it will control the initial pore water chemistry in a system. In weathered systems (such as mine waste), dissolution of the most soluble secondary weathering products will likely control the initial chemical composition of the aqueous phase, but will be rapidly modified by interactions with the solids (Chesworth, 1992). The composition of the pore waters will be controlled by the dissolution of the most soluble minerals present and the precipitation of the least soluble minerals (Chesworth, 1992). Residence time or leaching frequency will be an important factor to consider in terms of dilution and neutralization of the pore waters. In acidic solutions, the presence of neutralizing minerals at microsites may lead to the formation of precipitates locally. The role of the other factors on the formation of secondary weathering products will be discussed in the context of secondary Fe minerals. In soil environments, the formation of secondary iron minerals is strongly influenced by Eh-pH, leaching frequency, and organic matter (Birkeland, 1984; Schwertmann and Taylor, 1989). Primary minerals containing 40 Ch. 2-LiteratureReview elements with more than one valence state are often more soluble in the reduced state. For example, ferrous iron is released from primary minerals during weathering, and oxidizes to ferric iron. Ferric iron (as well as many other metals - Cu, Ni, Pb, Zn, etc.) is very insoluble in oxygenated waters over pH 6 (normal soil pH) and will precipitate, but solubility increases as pH decreases. If reducing conditions predominate, ferrous iron may travel away from the site and precipitate elsewhere. Leaching of surfaces results in the removal of weakly adsorbed ions and soluble minerals and introduces water with a lower ionic composition. In frequently leached microsites, minerals transformed by leaching (e.g. biotite to vermiculite) may dominate surfaces because the ionic strength of the pore water may not exceed the solubility product of any compound therefore formation of authigenic minerals is unlikely. Organic matter can also have an effect on secondary iron mineral formation. The organic matter content has been implicated because of the widespread occurrence of yellow topsoils over red subsoils (Schwertmann and Taylor, 1989). A variety of sulphate minerals are present in the oxidizing environment. Williams (1990) indicates sulphates range in the amount of water of crystallization and solid-solution. Substitution is common for all the simple divalent metal hydrate phases and just which hydrate forms is a function of temperature, ionic strength, water vapour pressure , and the cations present (Williams, 1990). Frequently, mixtures of hydrated sulphate are observed as efflorescences on mine wastes near oxidizing sulphides (Nordstrom, 1982). The influence of sulphate concentration and pH on ferric iron sulphate species is illustrated for jarosite and schwertmannite in Figure 2.2. 41 Ch. 2-LiteratureReview 2.9 Precipitated Weathering Products in Other Environments 2.9.1 stream precipitates The impacts of stream precipitates due to mining and associated effects decrease the biotic community diversity and biotic abundance (Short et al., 1990). Ochres and iron oxides are commonly reported in natural environments because of their easy to identify red-staining. Numerous authors have investigated the role of Fe precipitates in streams influenced by acidic drainage (Rybicka, 1993; Davis et al., 1991; Karlsson et al., 1988; Filipek et al., 1987; Chapman et al., 1983). Using various techniques (geochemical modelling, XRD and microprobe analyses) suspended and precipitated solids in stream beds have been identified as hydrous Fe and Al oxide phases (FeOOH, Fe(OH) 3 ; AlOOH, A1(0H)3) (Davis et al, 1991; Karlsson et al., 1988; Chapman et al, 1983). Davis et al. (1991) found precipitated gibbsite and ferrihydrite controlling Al and Fe solubilities in surface waters near the Central City and Idaho Springs mining districts. Chapman et al. (1983) found that among the reactions controlling metal solubility were the precipitation of Al(OH)3, Fe(OH)3, and Cu2(0H)2C03. 2.9.2 elemental sulphur stock piles A study of acidification of elemental sulphur stock piles in Alberta has interesting parallels to mine waste weathering (Warren and Dudas, 1992a; Warren and Dudas, 1992b). These authors investigated the mineralogical and trace element redistribution in soils effected by acidity due to oxidation of S° from a 25-year old sulphur pile. Chemical weathering at pH 42 Ch.2-LiteratureReview < 2.1 either partially or completely removed carbonates, Fe-containing primary minerals, chlorite, smectite, and plagioclase feldspars. Clay sized mica and kaolinite were not removed. Gypsum (CaS04«2H 2 0) , identified as discrete nodules and white (10 YR 8/1) coatings 1-2 mm thick, formed in situ. A hardened layer formed in the presence of hematite (2.5YR 5/6 red - 5YR 6/6 reddish yellow) at a depth of 45 - 55 cm. Samples collected within the hardened layer had a pH range 3.8 - 5.5. The metals, As, Co, and Ga were concentrated within this layer. Jarosites were identified in a yellowish (2.5Y) soil sample at pH 2.9, above the hardened layer. Other secondary products suspected in the profile were amorphous Si and amorphous secondary aluminosilicates. Mn, Sc, and Zn were not retained in the indurated layer in contrast to other authors who concluded these same metals were retained by free Fe oxides in weathered soils (Koons et al, 1980). 2.9.3 acid sulphate soils Acid sulphates soils exhibit similar characteristics to mine waste. When sulphide containing soils are drained, subsequent aerobic conditions result in acid sulphates (i.e. H2SO4) being produced from pyrite oxidation. These reactions are mediated by the same bacteria and chemistry that occur in mine waste. In most of these soils, a large fraction of the iron and sulphate from pyrite oxidation is incorporated into jarosite which is later hydrolysed to ferric oxide, releasing acid in the process (Breemen, 1973). In older acid sulphate soils, when the pH begins to recover and S0 4 2" ions are reduced, jarosite hydrolyses to ferric hydroxide which may in turn dehydrate 43 Ch.2-LiteratureReview near pores and channels to goethite and even hematite (van Dam and Pons, 1973). Jarosite formation presents the incomplete hydrolysis of pyrite. FeS 2 + 15/4 0 2 + 5/2 H 2 0 + 1/3 K + — > 1/3 KFe 3(S0 4) 2(OH) 6 + 4/3 S0 4 2" + 3 H + Potassium ions for jarosite formation are provided by the alteration of micas and feldspar (De Kimpe and Miles, 1992). Under acidic conditions, Al-hydroxypolymers can form in the interlayer of weathering micas (De Kimpe and Miles, 1992) leading to interstratified minerals. Jarosite buffers the pH of the system when small amounts of bases are present at a pH of 3.8 (van Dam and Pons, 1973). 3 Fe(OH)3 + 2 S0 4 2" + K + + 3 H + <—> KFe 3(S0 4) 2(OH) 6 + 3H 2 0 The presence of jarosite as pale yellow mottles along root channels and on ped faces in waterlogged soils is also referred to as the cat-clay phenomena. If Ca-carbonates are present, gypsum will form. Gypsum can also be a decomposition product of jarosite (De Kimpe and Miles, 1992). Weathering of clay and silicate minerals at extremely low pH leads to the formation of H4Si0 4 which is precipitated as cryptocrystalline silica (van Dam and Pons, 1973). In Texas, Carson et al. (1982) identified jarosite, barite and gypsum in upland soils showing relict features of acid sulphate weathering. In older acid sulphate soils where FT and S 0 4 " are leached and/or neutralized, jarosite tends to undergo hydrolysis to goethite. 44 Ch. 2-LiteratureRe view KFe 3(S0 4)2(OH) 6 + 3H 2 0 <—> 3 Fe(OH)3 + 2 S0 4 2" + K + + 3 H + 2.9.4 salt effloresecences Evaporite minerals present in salt effloresecences appear as a result of evaporation of water. Studies indicate that evaporites are generally composed of more that one mineral and often sulphate minerals (Kohut and Dudas, 1993; Bayless and Olyphant, 1993; Last, 1989; Keller et al., 1986) therefore secondary products formed in sulfidic minewaste and acid leached dumps may resemble minerals in salt effloresecences. Evaporite minerals are extremely labile, reacting to fluctuations in temperature and moisture which affects their solubility (Kohut and Dudas, 1993). Bayless and Olyphant (1993) examined salts that appeared during summer and autumn in a watershed near a deposit of pyritic coal refuse. Findings indicated that hydrated iron sulphate minerals were the source of observed ground- and surface-water chemistry at the study watershed because of their high solubility (156.5 g/L FeS0 4 x7H 2 0; Weast, 1977). Two salts examined with XRD showed the following minerals: copiapite -Fe 2 +(Fe 3 +) 4(SO 4) 6(OH) 2x20H 2O, melanterite - FeS0 4 x7H 2 0, rozenite - FeS0 4 x4H 2 0 and szomolnokite - FeS0 4 xH 2 0. Each salt had distinct mineral abundances. Dissolution of the salts in deionized water showed measurable levels of Al , Ca, Fe, Mg, Mn, Ni, K, Si, and Zn. Other elements, Ba, Cd, Cu, Na, and Sr occurred irregularly and in much lower concentration. Hydrated iron sulphate minerals could provide a relatively instant source of contamination from surface runoff near mine waste (Bayless and Olyphant, 1993). 45 Ch.2-LiteratureReview Nordstrom (1982) has identified similar efflorescent iron sulphates on the surface of mine wastes, and states they are an important intermediate preceding the precipitation of more common iron minerals such as goethite and jarosite. Kohut and Dudas (1993) examined evaporite mineralogy on salt-affected soils of Alberta and found dominantly sodium and magnesium sulphates. In order of abundance, minerals identified were thenardite, konyaite, bloedite, gypsum, eugsterite, halite, thermonatrite, trona, nahcolite, burkeite, hexahydrite and epsomite. Unlike Bayless and Olyphant (1993), these researchers found no regular associations between mineral species. Some minerals were unstable with respect to others under laboratory conditions making rapid identification essential (e.g. konyaite transformed to bloedite). 2.9.5 saprolites Saprolite is generally defined as thoroughly decomposed rock which has weathered in situ with the preservation of the original rock feature. This means that changes resulted in a material that has retained the texture and structure of the original rock (isomorphic and isovolumetric). Within saprolites, grains can display all stages of alteration. Minerals remaining are often pseudomorphic after other minerals. Velbel (1990) reviews three mechanisms by which products of rock weathering can mimic spatial relationships of the original rock, (1) differential parent-mineral weathering, (2) boxwork / microboxwork formation, and (3) etch-pit formation. Primary elements leached during saprolite formation are Ca, Na, K, Si, Mg, Fe, or Al (Stolt et al., 1992; Graham et al., 1989a,b; Calvert et al., 1980a). Stolt et al. (1992) found 46 Ch.2-LiteratureReview that the ratio citrate bicarbonate dithionite-Fe: total-Fe (CBDFe:totalFe) decreased with depth indicating a decrease in weathering. Reported losses of 73-82% of rock mass are attributed to leaching of Si and Al (Stolt et al.,1992). Calvert et al. (1980b) reported feldspar minerals altering to gibbsite, halloysite and amorphous aluminosilicate minerals in saprolites. Graham et al. (1989a) found that sand-sized grains of biotite altered to interstratified biotite/vermiculite, vermiculite, kaolinite, and gibbsite. Others have also observed kaolinite pseudomorphs of biotite (Rebertus et ah, 1986). This transformation proceeded through a interstratified biotite-vermiculite in which there was a hydroxy-Al interlayer. This requires weathering in an acid environment to supply the Ff" and soluble aluminum needed to replace the K and produce the hydroxy-Al interlayer. Graham et al. (1989a) found that almandine altered to goethite, hematite, and gibbsite. Anand and Gilkes (1984) studying lateritic saprolite from Western Australia found that feldspars altered primarily to halloysite and gibbsite while magnetite grains altered to martite (oriented hematite). Halloysite and gibbsite crystallized along voids and cracks from congruent dissolution of feldspar. Grains of hematite with magnetite cores formed because alteration of magnetite grains occurred at grain boundaries or along intra-grain cracks and proceeded inwards. Ultimately all the magnetite was replaced with hematite leaving a porous structure. Trace elements inherited from original magnetite should be retained in hematite (Kisvarsanyi and Proctor, 1967) and may occur as minerals isostructural with hematite (e.g.Cr203 - eskolaite) (Deer et al, 1962). 47 Ch. 2-Li teratureRe vie w 2.10 Identification and characterization methods Identification and characterization of minerals can be accomplished by a number of common techniques. Crystalline minerals are easily identified and characterized, on the other hand it can be very challenging to do the same for amorphous minerals and adsorbed weathering products. Techniques based on x-ray (XRD) and electron analysis (SEM and electron microprobe) and chemical dissolution are regularly used to identify mineral species and their chemical composition. These techniques are best used in conjunction with each other and with other descriptive features such as colour and environmental setting (surface or in microfracture). A preparatory procedure often used prior to mineralogical analysis is the concentration of minerals to a specific density. Minerals are considered "heavy" if their specific density is greater than 2.85 g/cm3 and light if below this value (Carver 1971). By suspending minerals in solutions with a known density, the specific density of the group of minerals suspended and settled is better defined. Solutions commonly used are tetrabromomethane and bromoform (Carver, 1971) but recent introduction of a new heavy liquid, sodium polytungstate (STP) (Commeau et al, 1987; Callahan, 1987), is an ideal substitute because it is nontoxic. The SPT solution is readily altered in density from 1.0 to 3.1 g/cm3 and in the absence of C a 2 + is chemically inert (Commeau et al, 1987). Identification of minerals is commonly done by petrographic microscopy and X-ray diffraction (XRD). Petrographic microscopy is used for mounted samples such as soils or thin sections 48 Ch. 2-Li teratureRe view and is often used as a teaching tool. Petrographic microscopes can be used to determine (1) identify, size, shape and condition of single grains and minerals, and (2) the abundance and interrelationships of constituents (Cady et al., 1986). The main drawback to this tool is that it is labour intensive and that the user must be familiar with a large number of minerals in using this technique. The development of image analysis procedures should reduce some of these problems. Jongmans et al. (1993) used this technique to quantify minerals in a study investigating the weathering of an alkali basalt pebble. X-ray diffraction on the other hand is used by many researchers for quick identification of minerals in soils and geology. X-ray diffraction analysis involves the bombardment of crystalline minerals with X-rays at a known range of angles and recording diffracted X-rays on a chart scanner. Minerals can be identified by comparison to published XRD manuals. Minerals to be identified must be crystalline and must make up at least 10% of the sample (by weight). Quantification of minerals, crystal size estimation and unit cell dimensions can also be determined through XRD (Whittig and Allardice, 1986; Eggleton, 1988). Interpretation can vary because of the presence of amorphous material, the degree of crystallinity, crystal size, degree of orientation, chemical composition, and density of packing (Whittig and Allardice, 1986). Comparison of ratios of elements in minerals is a useful technique to support identification techniques such as XRD. This can be very valuable to characterize amorphous minerals because XRD will be of limited use. Evangelou (1994) confirmed the presence of FeP04 coatings by the 1:1 ratio of Fe:P04. Tools available for this purpose are energy 49 Ch.2-LiteratureReview dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), electron microprobe, and dissolution analysis (assuming congruent dissolution). Selective dissolution analysis (SDA) is a technique used in geological and soil sciences. Chao (1984) gives a good review on the use of dissolution techniques. The premise is that specific types of compounds or minerals can be targeted for dissolution. The purpose is generally used to: (1) preferentially remove certain phases to carry out analysis of the residue, or (2) to quantify extractable phases that are difficult to estimate due to their crystallinity or low abundance. Results from these analyses must be interpreted with caution because chemical treatments are not completely selective (Gruebel et al., 1988). Two SDA procedures commonly used in pedological studies are 2h acid ammonium oxalate extraction in the dark (AAO), which is used to remove and quantify amorphous Fe products (e.g. ferrihydrite) (Schwertmann et al., 1982), and citrate-bicarbonate-dithionite extraction (CBD), for crystalline and "free" Fe oxides (Mehra and Jackson, 1960). Veiga et al. (1991) used the A A O procedure to show that Cu was intimately associated with an unidentified amorphous hydrous ferric oxide in a weathered copper ore. Karathanasis and Thompson (1995) used A A O and CBD procedures to characterize the poorly crystalline and crystalline Fe fraction of precipitates in a constructed wetland receiving acidic mine drainage. Another technique used involves hydroxylamine. Hydroxylamine HC1 extraction in HC1 (0.25 M NH 2 OH-HCl in 0.25 M HC1 at 60°C, for 30-60 min) is considered selective for amorphous Fe phases and is used frequently in sequential extraction schemes (Hall et al., 1996; Chao and Zhou, 1983). 2M hydroxylamine HC1 extraction in 25% HOAc (acetic acid) 50 Ch.2-LiteratureReview has been used for Fe and Mn oxides (Ribet et ah, 1995). In ARD/mine drainage investigations, A A O and CBD appear to be more commonly used for SDA of precipitated phases. A useful technique which has been developed to identify amorphous weathering products but can also be used for crystalline phases combines SDA and XRD. Schulze (1981) called this technique differential X-ray diffraction (DXRD). This is essentially a 4 step procedure: (1) obtaining a XRD scan of an untreated sample, (2) treatment of the sample with some SDA reagent to remove a specific phase, (3) obtaining a XRD scan of the treated sample, and (4) subtracting the two patterns from one another to obtain the scan of the phase removed by the treatment. Schulze (1981) used this procedure to show the presence of ferrihydrite in a sample. Mineral speciation can also be used to interpret geochemical data from field or laboratory solutions. Geochemical equilibrium calculations do not prove the presence or absence of a solid phase, but provide an indication of the tendency for a reaction to occur. Calculations tend to be quite tedious and complex, thus models have been computer coded. These programs are often able to incorporate many of variables needed for consideration of mineral speciation but inevitably some of the more complex factors are not accounted. In addition, these programs were not designed specifically for rock dumps and can not account for parameters such as surface heterogeneity, high acidity, and leaching frequency. Two programs commonly applied in studies of acidic mine drainage are PHREEQE and MLNTEQA2. PFIREEQE is a geochemical model designed by the US Geological Survey 51 Ch. 2-Li teratureRe view (Parkhurst et al., 1982). It is a FORTRAN based program designed to model geochemical reactions based on an ion-pairing model using the Debye- Htickel expression. NEWPHRQ, an updated version, can simulate many common phenomena such as mixing, rock-water interactions, mineral equilibrium, and ion-exchange reactions. User defined parameters include the reaction path, system composition, temperature conditions, equilibrium conditions, aqueous species, and mineral phases. A good discussion on the use of NEWPHRQ for the characterization of in situ geochemistry is given by Marozas (1989). MTNTEQA2 (Allison et al., 1991) is an equilibrium geochemical thermodynamic model capable of calculating equilibrium, aqueous speciation, adsorption, gas phase, partitioning, solid phase saturation states, and precipitation-dissolution of metals. It contains a program called PRODEFA2 which is used to define problems and generate input data files. Activity coefficients are calculated by using ion pairing and either the Davies or Debye-Huckel equation. An extensive thermodynamic data base is included in the mode. MTNTEQA2 has been used to predict water chemistry and solubility control for metals in natural waters and laboratory solutions (Monterroso et al., 1994; Blowes and Jambor, 1990; Schwab, 1995). Although other models are suitable for equilibrium geochemical modelling ( EQ3, SOLMINEQ, WATEQ4F, etc.), the most common one applied to mine drainage based on the review of the literature is MTNTEQA2. 2.11 Summary A review of the literature suggests that secondary weathering products accumulating 52 Ch.2-LiteratureReview in the mine waste environment can influence metal distribution and loading in seepage. The types and amounts of secondary weathering products accumulating in mine waste can be affected by biological, physical, chemical processes, and primary and secondary minerals. Weathering products produced in soils affect soil colour at the soil surface and along preferred pathways. These neoformed minerals have significantly different thermodynamic properties than the parent material. As new mineral form, contaminating elements can become occluded. New minerals formed can influence pore waters, and thus influence the subsequent neoformed phases. Thus, the history of the site influences the water chemistry, the precipitation of neoformed phases, and the dissolution of existing phases (primary and secondary). Although, secondary weathering products in waste rock have not been extensively studied, the secondary minerals formed may be similar to those found in environments such as soils, sediments impacted by acid sulphate streams, rock outcrops, and saprolites. Techniques used to examine weathering processes and products in these other environments may be successfully applied to mine waste rock materials. 53 Ch.3-Study Area 3. Study Area 3.1 Location and Climate The study area is located in south central British Columbia, a region consisting of several operating and former metal mines. Gibraltar Mines is an open pit copper mine located in central British Columbia approximately 360 km north of Vancouver B.C. (Figure 3.1). It has been in production since March 1972. The Gibraltar property is located at elevations between 914-1230 metres on the western flank of Granite Mountain. The region has been intensely glaciated and the mine is located in an ancient glacial valley. The Cuisson Creek drainage system at the base of the mountain, drains the area northward via a series of creeks, rivers and lakes to the Fraser River. The latitude and longitude of the mine are 52°30' and 122°16', respectively. The region is considered to be humid to sub-humid with light precipitation, being on the lee side of the Coast Mountains. The average precipitation at the mine site is 500 mm (1995 Annual Environmental and Reclamation Report, Gibraltar Mines). The largest amount of precipitation occurs during June, July, and August. The average annual temperature is 3.6°C. Annual evapotranspiration for the mine area is estimated to be 325 mm (based on lake evaporation and ground cover) (Klohn Leonoff, Gibraltar Mine Hydrology Study, Feb 1993). The biogeoclimatic zone of the site is the subboreal spruce zone (Soil Survey No.53, 1988). 54 Ch.3-Study Area Vancouver Figure 3.1 Location of the Gibraltar mine site. The most extensive surface materials in the region are unconsolidated sediments, metasedimentary and intrusive rocks (Soil Survey No. 53, 1988). The soils in the region have developed from glacial fluvial and till deposits consisting mainly of lodgement and ablation morainal till, with minor amounts of fluvial sand and gravel. The two soil associations mapped in the area are the Deserters-Cinema and the Deserters-Dragon units. The dominant soils are Orthic Gray Luvisols and Orthic Humo-Ferric Podzols. 3.2 Site Geology The Gibraltar ore body is a large low-grade porphyritic deposit with copper 55 Ch.3-Study Area disseminated in fine grained igneous intrusions in adjacent host rock (Bysouth and Carpenter, 1984). The host for the. Gibraltar ore bodies, the Granite Mountain batholith, is located within a wedge of Mesozoic and Paleozoic rocks (Bysouth et al., 1993). The Granite Mountain batholith consists of four phases of which Mine Phase tonalite is the main host rock for most of the Gibraltar ore bodies. Mine Phase tonalite has a relatively uniform mineralogical composition of 50% saussuritized andesine plagioclase, 20% chlorite, and 30% quartz (Bysouth and Carpenter, 1984). Plagioclase is altered to albite-epidote-zoisite and muscovite. Chlorite appears to have formed from biotite and minor hornblende. Accessory minerals include magnetite and rutile. The rock is generally equigranular with a grain size of 2 to 4 mm. Generally, the unmineralized rock is weakly foliated. Pyrite and chalcopyrite are the primary sulphide minerals with small concentrations of bornite, molybdenite and sphalerite (Bysouth and Carpenter, 1984). The dominant form of copper mineralization is fine grained chalcopyrite, which makes up to 60% of the copper grade. Much of this chalcopyrite is dispersed within phyllosilicate foliation lamellae. Pyrite shows some degree of segregation from chalcopyrite. Principal alteration minerals of these deposits are chlorite, sericite (fine grained muscovite from hydrothermal activity), epidote, carbonates and quartz. Ore grade mineralization is associated with sericite and chlorite. Supergene enrichment has lead to the presence of native copper, cuprite, chalcocite, digenite, and covellite. Molybdenite is a minor but important associate of chalcopyrite as it is the source of the Mo mined. 56 Ch.3-Study Area 3.3 Waste Rock Dump Construction and Mineralogy Waste rock dumps at the Gibraltar mine site were constructed by end-dumping. Rock dumps were constructed in layers or lifts then topped with a layer of compacted stockpile overburden material which has lead to areas of low permeability in the dump influencing water infiltration and flow. Although there is some degree of segregation, dumps remain heterogeneous with regards to particle size and overall permeability. There are five waste rock dumps at the Gibraltar mines from the mining of four open pits (Figure 3.2). Mineralogy of the waste material is similar to the 50-20-30 ratio (chlorite-plagioclase-quartz) found in the host rock (Bysouth and Carpenter, 1984). Copper concentration in the rock dump varies from 0.11 - 0.27% (Bysouth and Carpenter, 1984). Pyrite concentrations are estimated to be up to 3% in some areas (Bysouth and Carpenter, 1984). 57 Ch.3-Study Area 58 Ch.3-Study Area 3.4 Acid Leaching Commercial acid leaching at the Gibraltar mine was initiated in 1986 after studies in 1983 and 1984 demonstrated that economic recovery of copper was feasible. Copper extraction is achieved by accelerating the weathering process and stimulating biological oxidation. To initiate leaching, dumps are divided into 9000 square meter grids, and acid is delivered through 5 cm pipes drilled at approximately 3 m intervals with 0.3 cm diameter holes. Dumps are sprinkled with sulphuric acid solution in quantities aimed at maintaining a pH of 1.8 to 2.1 for leachate exiting at the dump toe. The solution percolates through the dumps and discharges at the toe into collection ditches. The low pH helps to reduce iron precipitation in voids which can reduce permeability and efficiency of leaching. While travelling through the dumps, the acidic solution contacts various copper minerals releasing solubilized copper in the form of copper sulphate. Additions of fresh acid are required occasionally to account for any acid that is consumed in the dump. The leaching reaction is a combination of acid solubilization and bacterial action. At Gibraltar, a leaching cycle consists of a 14 day leach and 56 day rest cycle to allow bacterial reactions to occur (B. Patterson, personal communication). Dumps at other sites have reportedly been leached periodically for over twenty years (Bartlett, 1992). For bacterial action to occur, conditions in the dump must be near the ideal pH of 2.1 - 2.3 and other favorable factors must be present. Favorable factors include the presence of oxygen, maximized solution contact with ore minerals, and temperatures suitable for bacteria to proliferate. 59 Ch.3-Study Area Generally, heap leach operations utilize designed leach pads to prevent loss of leach liquor, but rock dumps at Gibraltar were constructed on a layer of compacted glacial till and were not engineered for leaching. Leachate collection ditches were added after recovery of copper was shown to be economic. Copper recovered through dump leaching operations make up to 10% of the Gibraltar mine's total copper production (approx.10 tonnes/day) (Klohn Leohnoff Consulting Engineers, 1991). The Gibraltar mine site is the only one in B.C. applying acid-leach technology on waste rock piles. 3.5 Study Trenches The acid leached rock dumps at the Gibraltar mine provide a unique opportunity to compare the weathering products from two different conditions: dump leached (enhanced weathering) and not dump leached (natural weathering). The highly sulphur-charged and oxidizing environment under acid leaching leads to unique conditions for the formation of weathering products. Four trenches were dug at different locations on the surface of waste rock dump 1 for three different treatments or weathering regimes. The three treatments or regimes can be defined by the acid leaching activity at the time of sampling as, (1) post-leach weathering, (2) weathering under active leaching or leach weathering, and (3) natural weathering. Trench A and B were located in an area where leaching had occurred initially for 4 years at which time leaching was ceased, and at the time of sampling had not been acid leached for 2 years (post-leach weathering). Of the two trenches, one was located near the crest of the dump, and the 60 Ch.3-Study Area other approximately 20 m away from the dump face. Trench C was in an area under active acid leach at the time of sampling, and had been leached for 4 years prior to sampling (leach weathering). Trench D was located in an area where the rock dump had never been acid leached, thus weathering activity would not have been altered by sulphuric acid leaching (natural weathering). Trench A and C were located near the crest of the rock pile. Waste rock dump 1 had been irrigated since July 1987. By sampling waste rock from these three treatments or regimes, geochemical properties as influenced by the weathering intensity could be examined since original mineralogy was similar. The material from trench A and B has been in place for approximately 15 years and from trench C and D, approximately 21 years. A back hoe provided by the mine operator was used to excavate the trenches which were approximately 5 m long x 3 m wide x 3 m deep. 61 Ch.4-Chemical and Mineralogical... 4. Chemical and Mineralogical Characterization of Waste Rock Samples Collected based on Morphological Characteristics. 4.1 Introduction Many physical, chemical, and biological processes in rock dumps have yet to be described well enough to be modeled reliably. Water chemistry prediction procedures for waste rock dumps, dams, tailings are still tentative due to their complexity (Morin and Hutt, 1994). Retained secondary weathering products can modify the surface properties of waste rock dumps and control the inorganic composition of pore waters. The formation of insoluble secondary minerals or stored weathering products may lead to significant attenuation of metals in acid mine waters (Levy et al., 1997). One problem when dealing with secondary weathering products in rock dumps is the establishment of a sampling scheme. During sulphide weathering, weathering products are translocated and often precipitated as oxyhydroxides (oxide) and amorphous mineral coatings on soil mineral components (Lee et al., 1990). Iron staining, presumably due to the presence of oxidized Fe on exposed surfaces of rock dumps, is evident at many mine sites (B.Price, pers.comm.). In weathered tailings, sulphide oxidation produces an abundance of ferric-bearing secondary precipitates near the surface (Ribet et al., 1995). Similarly, of the elements released during waste rock weathering, Fe is retained significantly and because of its tendency to oxidize and precipitate, it may be an easy-to-determine indicator of weathering intensity due to the colour (i.e. redness rating) produced by oxidized Fe minerals. Thus, colour may be a useful parameter to include when describing mine waste samples and the environments associated 62 Ch.4-Chemical and Mineralogical... with the form of secondary minerals. In acid-generating or acid-leach rock dumps, precipitation can lead to a variety of phases with different crystallinity. Rapid hydrolysis of Fe 3 + leads to the formation of Fe(III) oxides and oxyhydroxides with amorphous to extremely small particle sizes (< 10 nm) (Schwertmann and Taylor, 1989). There has been some work characterizing and identifying the secondary minerals stored in a older mine rock dump (>50 years) which has shown some of the precipitated weathering products are poorly crystalline, thus standard techniques for mineral identification (i.e. X-ray diffraction and petrographic microscopy) are of limited use (Lin, 1996). An estimation of the amount of element released from the primary minerals in a rock dump may be a useful measure of the weathering intensity occurring near a microsite i.e. a weathering index. Ideally, the weathering index should have a temporal component, but this is unlikely with mine rock weathering products because the secondary minerals at a given location reflect many precipitating events. Although limited, a weathering index can provide an indication of the overall weathering environment which has influenced a site historically. The collection of representative samples from a waste rock dump can be a challenging task because of its heterogeneous nature. Establishment of a sampling scheme depends on the objectives of the study, as well as time and cost-constraints. This is complicated by natural weathering processes which rarely reveal distinct boundaries between two adjacent classification units unless there is a natural or anthropogenic influence. Mine waste rock may be considered proto-soils (i.e. they are beginning to form natural soil material), and use of 63 Ch.4-Chemical and Mineralogical... morphological features, such as colour and grain size, may be a useful sampling tool in a rock dump to estimate degree of pedogenesis. A number of sampling methods are commonly used in environmental assessments. Each method has its advantages and disadvantages. Mine waste rock dumps may pose difficulties for several reasons, including (1) the amount of material in rock dumps (typically in millions of tonnes and 10's of hectares), (2) variable composition and method of dumping, and (3) the lack of knowledge regarding the physical conditions inside a rock dump and how these modify chemical reactions at a microsite. Four commonly used sampling schemes are simple random sampling, stratified random sampling, systematic sampling, and judgment sampling. Simple random sampling is not efficient for spatial analysis and can be very involved and time-consuming for large finite populations and is considerably easier for small populations. A simple random sample can be defined as one which is chosen in such a way that every possible combination of units or samples has the same probability of being selected (Petersen and Calvin, 1986; Walpole, 1982). Local variations such as vegetative or man-made disturbance (including rock dump design) makes simple random sampling ineffective for many sampling areas. Stratified random sampling involves subdividing the population (i.e. area to be sampled) into a number of subpopulations such that the units are fairly homogeneous in each subpopulation. Samples are selected randomly within each "stratified" group or subpopulation. For example, when examining available N supply in a forested region of a 64 Ch.4-Chemical and Mineralogical... mountain slope, the mountain side might be divided into strata according to the height above the toe of the mountain. Sampling in this manner serves two purposes, (1) to make a statement about each of the subpopulations and (2) to reduce the variability within each subpopulation (Petersen and Calvin, 1986). If the process of stratifying the population does in fact reduce the variability of the data, the sampling error decreases, and a greater precision is achieved. Systematic sampling involves selecting units from a population at regular distances from each other, with the starting point determined at random. For example, systematic sampling could be accomplished by setting up a grid pattern, consisting of a two sets of lines equidistant apart and at right angles to each other, and collecting samples at intersecting points. This method offers the advantages of complete coverage and potentially greater efficiency since sampling locations are located at regular intervals. However, a hidden periodicity in the population would result in a systematic bias and an inaccurate assessment of the site (Walpole, 1982). Judgment sampling, or biased sampling occurs when a sampler uses existing knowledge, either from the literature or past experience, to obtain a representative sample from a population determined a priori. Samples selected in this manner are considered biased because the units are selected with different but unknown probabilities (Petersen and Calvin, 1986). There is no way to assess the accuracy of the results from such a sample and in fact, samples may or may not represent the population. For small sample sizes, judgment samples have a lower random error compared to random samples, but as sample size increases, and 65 Ch.4-Chemical and Mineralogical... selection of representative units becomes more difficult, the error with a random sample becomes smaller than with a judgment sample. Judgment sampling may be appropriate if low accuracy and no estimate of precision are acceptable (Petersen and Calvin, 1986). Morphology (particle size, colour, structure, etc.) has been used as a bias when sampling natural bodies such as in soil (von Steiger et al., 1996). Colour as determined by the type, particle size, and distribution of Fe oxides is used to explain soil genesis and the degree of weathering and is also an important criteria for naming and classifying soils (Bigham and Ciolkosz, 1993; Canadian System of Soil Classification, 1978). In surficial weathering environments, iron oxides (goethite and hematite) have a high pigmenting power (e.g. gossans) and determine the colour of many mineral soils, even at concentrations as low as 1% by weight (Schulze, 1994). The aim of this work was to characterize the chemical and mineralogical content of rock samples collected from three different weathering regimes in one rock dump. In order to examine the value of using colour when sampling in a waste rock dump, samples were selected randomly but stratified using morphological features as sampling unit boundaries (i.e. stratified random sampling). 4.2 Methods: field and laboratory procedures Samples were selected based on changes in colour and/or particle size in the 4 trenches described in chapter 3. In some instances, colour changes occurred where there was no notable change in particle size. In trench A (post-leach weathering), pseudo-horizons or 66 Ch.4-Chemical and Mineralogical... layering of differing colour in the profile were observed sloping downward at 30-45° towards the outer edge of the rock dump (Figure 4.1 and Figure 4.2). 67 Ch.4-Chemical and Mineralogical. Ch.4-Chemical and Mineralogical. Ch.4-Chemical and Mineralogical... Eight samples were collected from the profile on one side of the trench and one from the nearby outer exposed face of the rock dump. In trench C (leach weathering), there was layering similar to trench A although colours were not as bright. Ten samples were collected, 9 from the profile on one side of the trench and the 10th sample from the opposite side of the trench. Colour differences with well defined contacts between layers were evident throughout the profiles in both trench A and C. No layering was observed in trench B (post leach weathering) and D (natural weathering). In trench B and D, there were 8 and 7 samples collected. A total of 34 samples were collected from the four trenches. Samples collected from the exposed profile in each trench were stored in sealed plastic bags with a tag for identification inside the bag, and transferred to the laboratory for analysis. Shovels and trowels used for sampling were cleaned between samples. Location of collected samples was logged using depth and trench identification. In the laboratory, sub-samples were air-dried, gently crushed with a wood rolling pin, and sieved through stainless steel sieves to isolate four fractions: >4 mm (stones), 4 - 2 mm (gravel), < 2 - 0.05 mm (sand), and < 0.050 mm (silt-clay) fraction. Sub-samples of whole fine fraction (< 2mm) were retained for particle size analysis using the hydrometer method, in combination with sieving to isolate the sand fraction. All other analyses were performed on both the sand and silt-clay size fractions. In some cases, there was not enough silt-clay size material for analysis. Analysis consisted of paste pH (1:2 soil:water), Munsell colour on the fine (< 2mm) and the silt-clay (< 50 pm) fraction, bulk mineralogy, total major and minor elements, and 70 Ch.4-Chemical and Mineralogical... total sulphur. pH was determined using an Orion 420A meter with Ag/AgCl internal reference and temperature calibration. Total carbon was determined for selected samples using a L E C O carbon analyzer. Bulk mineralogy was determined using XRD analyses conducted on random powder mounts of untreated powders using a diffractometer (Philips, PW 1050/25) emitting Cu-Ka radiation (k = 1.542 A ) . Silt and sand fractions were crushed to a fine powder using an agate mortar and pestle to allow the determination of total major and minor elements by XRF analyses using a computer-controlled Philips 1400 automated X-ray spectrometer. Total sulphur was determined on a LECO-S (model SC132) analyzer. Sample colour was determined using a Munsell colour book and white paper as a background. In order to compare Munsell colour between samples, several authors have suggested schemes to calculate an index value from Munsell colour (Torrent et al., 1983; Hurst, 1977). The method described by Hurst (1977) was selected here because it had the most significant correlation coefficient values with iron, which is known to relate to sample redness (Bigham and Ciolksz, 1993), and is the dominant pigmenting element in these samples. Hurst colour rating (Her) was calculated from Munsell colour notation by using the following relationship: Her = (H* x V)/C where: H * (modified hue) is determined from hue using the conversion below; V and C are equivalent to the numbers from Value and Chroma in the Munsell notation 71 Ch.4-Chemical and Mineralogical... hue OR 5R 10R 5YR 10YR 5Y 10Y H * 0 5 10 15 20 25 30 e.g. a sample with the Munsell colour 10YR 5/6 (H* = 20, V = 5, C = 6) has an Her value of 17 (Her = 20*5/6) Correlation among different properties and elements was determined by the Spearman rank correlation coefficient. The level of significance for all testing was P <0.05 unless otherwise specified. 4.3 Results and Discussion The exposed profiles in the trenches revealed two morphologically different patterns of waste rock material depending on the proximity to the crest or edge of the rock dump. Profiles located in trenches near the crest of the dump showed highly-structured (stratified), steeply-dipping layers defined primarily by changes in colour and, secondly by particle size. Deposition of waste rock by dump trucks near the edge of the rock dump likely led to the presence of the layers sloping downwards at approximately the angle of repose. Profiles in trenches away from the dump crest did not have structured layering, but showed random and irregular patterns of oxidation. At the time of sampling, the four trenches had experienced significantly different acid leaching regimes and were classified as post leach weathering (trench A and B), leach weathering (trench C), and natural weathering (trench D) (Chapter 3). 72 Ch.4-Chemical and Mineralogical... Particle size distributions of the whole sample and the fine fraction, paste pH for the sand and the silt-clay fraction, and Munsell colour of the fine fraction studied are reported in Table 4.1. Sample colour was diverse ranging from strong brown to white with corresponding Hurst colour ratings ranging from 11 to 100. Low Her (Hurst colour rating) values corresponded with samples of low hue and/or high chroma. Prior to any analysis being performed, it was clear that the coarse fragment fraction. (> 2mm) was the dominant fraction by weight and volume in all samples. The mass of the sieved fine earth fraction ranged from 9 - 32% of the total sample mass, with 3 exceptions where the fine earth fraction contributed to 43, 58, and 63% of the mass. A similar range (16 to 25%) is reported for terraced rock dump benches at other porphyry Cu-Mo mines in BC (Murray, 1977). The sand-sized fraction ranges from 51.5 to 71.7%. The soil-sized fraction in the samples were sandy loam, except for one loam (USDA, 1982). The proportions of sand, silt , and clay in the fine earth fraction were in a narrow range with only slight variation. The coarse fraction varied widely. Variations in particle size for material from waste rock dumps have been attributed to difference in the age of the waste rock, methods of blasting and materials handling, variation in the strength and competency of the rock, and weathering (Price and Kwong, 1997). The period of time waste rock was on the surface of the rock dump is an important weathering factor because of traffic, wetting and drying, and insolation. Unfortunately, detailed deposition records of waste rock materials were not kept. As a result, the time at the surface for the various layers could not be determined. 73 Ch.4-Chemical and Mineralogical... OS s CN CN © Tf CN CN M ^ M Is- - OO t Tf cn r- co r- oo o o» < o> < m in —-Z - 2 - - -co co co w y i « w w oo co O N <"*"• ^ - f i n r- o J J j J —] J « M W [/5 C O C O Z* oo Z! ON ^ NO ~ ! ^ ^ 2 ^ ^ _ N O — cn CN cn r- Tf O cn —« eg r-i —i rN o ^ Tt-vo d 6 d ^ ^ CN n ^ o> ^ cN cN -—• cN cn — CN — cn — — rN CN cn — 1-3 | on C S s 12 2 « ^ ^ OO — CN cn NO CN r- n in «o CN o\ in a ^ ts a in s C O \ r t co oo oo ^ co co co oo cn CN m Tf Tf M 'O QO CO cn cn rn NO CN Tf CN <-> •= DC <^  a a N O N O m in in N O in in r- C O 0 0 C O N O in V) N O N O N O N O r» in r- r» N O cn N O cc as a: OS oS "a: "a; OS as aS Ctf OS >- >» >» >- >- >• >• > >» >• >• >• > >- >- >- >- >- > >• "X > >- •x >» >« >- >- >- >« >-in in o o in in o in in o m o in m in m in in in © in o in in o o o m o <n in in o C N C N r-^  < N C N oi C N CN" C N r-^  C N N O N O O N O N O N p C O O N oo N O O N r-» o O N N O m O N C N N O N O Tf m C N Tf Tf C O in N O N O cn m" fN C N C N C N C N cn C N C N C N C N C N C N C N cn" C N Tf" »n in in" Tf" cn Tf cn m" Tf Tf Tf Tf cn oi Tf C N p O O N oo O N O N O 0 oo O N O r- oo O N O O N O oo C N in N O in Tf Tf in in C O in C N O O cn cn" C N C N C N C N C N C N C N cn ( N C N C N C N Tf N O Tf" cn" Tf cn cn Tf Tf Tf Tf* cn Tf* C N q 0 0 in O r-; C N O N C N cn p r- 0 0 in O N N O C N Tf m o oo _ p C N in C N O N N O cn O N N O rn CN C N C N O O d cn ( N C N T—t © d d C N CN* < N C N — d ~* ~* d d d ~* d d < < < < < < < < < CQ ca ca ca ca ca ca ca CJ CJ CJ CJ CJ CJ CJ U a V Q Q Q Q a Q a C N m Tf in N O [— oo O N o — CN cn Tf in NO r~ 74 Ch.4-Chemical and Mineralogical... Paste pH of the fine fraction ranges from 2.7 - 6.2. Average pH values of the samples increase in the trench order: B < A < D < C. Sand and silt+clay fractions from samples taken in trench A, B, C, and D had pH values ranging from 2.6 - 3.6 ( X = 2.9 ), 2.6 - 3.0 ( X = 2.8), 3.3 - 6.2 ( X = 4.4), and 2.6 - 4.8 ( X = 3.9), respectively. Acidity in trench A and B results in lower pH values compared to the other trenches. Paste pH values of the silt and sand fractions were very similar and within 0.3 pH units in all but 3 cases where pH varied by 0.5 pH units. Possible explanations for the observed differences in paste pH are: (1) exhaustion of neutralizing minerals such as carbonates, in trench A and B, but not in trench C and D, (2) reduction in the effective neutralizing potential of rock material from trench A and B because of coatings of oxides and oxysulphates on rock surfaces, (3) the continuous removal of any surface precipitates forming a protective coating due to the leaching acid in trench C, and (4) differences in original rock materials or mineralogy. It seems unlikely that any one mechanism is responsible for these pH differences and in fact a combination of reactions is likely probable. In trench A, B, and D, weathering products have been allowed to accumulate without the intense leaching experienced in trench C. This suggests that acidic secondary phases were accumulating in post-leach and natural weathering areas, but in active leach areas weathering products were not accumulating to the same extent resulting in the higher pH value. Unfortunately, the amount of time each layer or pseudo-horizon was at the surface is indeterminable. Therefore, the time of direct exposure to the atmosphere and effects of physical weathering (e.g. traffic) can not be ascertained. Colour can be a useful indicator for iron oxides formed in pedogenic environments 75 Ch.4-Chemical and Mineralogical... (Schwertmann, 1993; Fanning et al., 1993; Schwertmann et ah, 1982; Hurst, 1977) especially when there is a lack of organic matter, such as in the Gibraltar mine rock dumps. Colour should not be used as the lone identifier of a mineral, but it can be used as an indicator of the types of oxidized Fe minerals present and suggests the pedogenic environment in which formation took place. Based on sample colours (Table 4.1), various Fe-oxides and oxysulphates are possible: goethite (7.5YR-2.5Y), hematite (7.5R-5YR), lepidocrocite (5YR-7.5YR), ferrihydrite (5YR-7.5YR), maghemite (2.5YR-5YR), jarosite (5Y), and schwertmannite (10YR) (Schwertmann, 1993; Bigham et al., 1990). Mixtures of minerals yield intergrades of colour. For example, Hurst (1977) found that with an increasing ratio of ochre:quartz, there was an increase in redness corresponding to increased Fe oxide content. Under the diverse and extreme weathering conditions at Gibraltar mines it is likely a suite of minerals is present. Due to the minute quantities of retained secondary weathering products, the poor crystallinity of the precipitates, and the intense XRD peaks associated with the dominant primary minerals, interpretations made from the XRD scans are qualitative. Although Fe-oxides are implied by the sample colours, a broad background indication of Fe fluorescence in the presence of Cu-Ka radiation was not present in any of these scans. Detrital host rock o minerals were dominant in all the samples. Intense peaks characteristic of quartz (4.26 A, 3.34, 2.46), plagioclase feldspars (4.02 A, 3.67, 3.20), muscovite (10.1 A , 5.05, 2.59, 1.99), and chlorite (14.2 A, 7.1, 4.68, 3.53, 2.46, 1.99) are prominent in all scans. A series of smaller peaks indicative of minor primary minerals are present for epidote (4.02 A , 3.49, 76 Ch.4-Chemical and Mineralogical... 2.90, 2.69, 2.68 ) and zoisite ( 4.0 A, 3.10, 3.07, 2.87, 2.69). Diffraction patterns from the samples show peaks indicative of several secondary minerals: gypsum (7.60 A, 4.27, 3.06), hematite (3.67 A , 2.69, 2.51), goethite (4.18 A, 2.68, 2.44), chalcanthite (4.73 A , 3.99, 3.71), o langite (7.12 A, 3.56, 2.49), and some minor amounts of unresolvable minerals. In acid sulphate soils, unresolvable materials constitute a significant proportion of the clay-sized fraction (Horn and Chapman, 1968). Total elemental analyses reflects the detrital mineralogy indicated from XRD scans. Summarized results from XRF analyses are shown in Table 4.2 and Table 4.3 for sand and silt-clay fractions. (Complete analytical results are included in the Appendix). The abundance of Si, Al , Fe, Ca, K, Na, and S can be attributed to the presence of andesine plagioclase (NaAlSi 30 8 - CaAl 2 Al 2 0 8 ) , muscovite (KAl2(Si3A10io)(OH)2, Fe-Mg chlorite, pyrite, chalcopyrite, and quartz (Si02). S levels in samples from trench C (leach weathering) were lowest compared to the other trenches while Mg levels were highest. Calcium levels were lowest in trench D (natural weathering) but Cu was highest (sand and silt-clay). Comparison of copper levels in trench C and D indicate concentrations that are approximately 2-6X and 10-20X greater than in trench A and B, respectively. Copper levels in areas near trench C (leach weathering) and D (natural weathering) were expected to be highest. 77 Ch.4-Chemical and Mineralogical. 3) 3 CN O © o r H —i CN >n -st- C N o" o ^ r H o 1 o © r-; CO r H CN d ^ d q m (N r H co d ov r~ 6 d m r- o\ d ^ d t-; CN CN d c i N CN CN r-d ^ d I-; co >n H K t>i Ov CN co' ^ ^ in ov in d vd c o X > Ov Q C T3 00 c/3 Oi d d o T j -r - ! d r H CO d d r-J d CN r H d d 00 r-5 d CO CN r-I d >n C N —; d f- vo CN d r- CN d oo -<t d d •<* in co d Ov CO CN ^ co vp oo d Ov co co r-J d p p C O CO CN p ov c o in Q C T3 ca c U ca S C/5 m JS o c o 00 C ca Pi —i C O 1 O "1 O —i O —< —i d o d o r~- C N o m d d —^  d o r H CN Ov —! d d o T J - vo m CN d CN r H •rr m co ^ o r-1 r-I r H OV OO "<t O C O O cc H oo Ov II a c c o x ca 00 S 55 U o c u tl _ ca CZ5 pSi r H ,^ CO "1 O "1 o ° d ° d V O O O V ^ H o o i n 1 ^ CN^CO^-! rH rH CN o _H CN _, _i -1 o ^ 'I © d ° ° CN r- CN d d d d >nco-HCO C N ov in oo d d - n d C N d co d m rH tN H Tf « O ^ ^ ^ rH © rH d 00 T t CN O (N r H rt VO r H r H d CN d - H CN 0O r - ! O r-I O vq r~- ov ov -<t d in co oo ov o r~ r-; C N ov co p v q o o r H r^or^r^ co d cd h VO II c e ca u B O > Q -a S3 •a e ca x ca 4H ^ 2 (Zl C D tl 78 Ch.4-Chemical and Mineralogical. ao 0^ o o d d CN o m co d © CN 00 CN CN VO r-5 O OV CO r-J O Tfr CO C O r H O CN © —i Ov vd H CN 00 t-; © 00 rH 2 '> Ov Q CN CN rH rj-H d rH © rl CN CN r-5 d >n co in d O CO C N d •n- in CN r-i r>; H in C N co vo r^  O oo Ov od co oo co CN rH >n ov vd a .s ^ 00 i3 ca on Pi rHrHCNrH rt g (M r-, ,_ ,_ (V) rt d o d - d © , - ; © © d o d o O O r H O ^ Ol 00 H ^ H ^ f T j O . O CO CN in r H © © © d r-; vO h 1- d »i t<i CO r H OV C N ^ C N r H C o > a T3 C ca 3 .s 00 H 2 « S 55 P< PH O c s © d ° ° ov co in in d d H d CN VO CN d vd CN VO Ov CN CN rH Ov Q e l c -a ca c u ca c o ca ca S 55 oi u o c tl C N rH rH o P © d m C N ov co d d d d rHVOT-fCO Ol H O IO C N V O r H r - -C N - H T t O r H r H T t O rH O CN O coojinp cNrH-rj-CTs © co co vq r H O r H r H r H © r H © r H © r H © C N co vq oo N oo ( N oqr^r^p C N d C N rH ^ O r H r H C N © C O C N ovcoov-^ t; t> C N r~ ov ovr-^OrH N r i Tf H CNrHinrH ^ 0 ( 0 ^ pin>nco —: <"i T t C N i r ^ r _ ; r H O r H © r H © r H r H r H © r H r H C~; © p 't H K C O C O C N in C N C N ^ C N C N OOOrHCN - H O V O V © H in H Ifl ^ © ^  ov cv © ov r~- © ^  ov c o VO II c ca a .5 5 S S 55 oi J3 U c 79 Ch.4-Chemical and Mineralogical... Carbon is present in very small quantities in some samples. Levels tend to be < 0.20 %C (wt), and as paste pH decreases below 3, levels drop below 0.10% (wt). Carbonate minerals were not evident in any of the XRD scans. Weathering indexes are based on an understanding of element mobilities under various weathering conditions and have been used to describe weathering processes and element redistribution (Sturchio et al., 1986; Kronberg and Nesbitt, 1981). The mobility index proposed by Sturchio et al. (1986) was used to compare the mobility of various elements in each trench to those undergoing natural weathering (Figure 4.1; trench D). In this method, Ti is assumed to be the least mobile element and concentrations of various elements from each sample are normalized to the Ti concentration, thus the mobility index is calculated from: » U T . , ( C i / C T i ) sample . Mobihtylndex = l| = — where Cj is the concentration of element I and ( C ; / C T i ) reference CTJ is the concentration of the Ti. Since trench D had not been acid leached, those samples were considered the least weathered, thus the averages from the other trenches were compared to the average from trench D, the reference. The mobility index for many elements is less than 1, indicating that most of the elements studied are removed during the weathering processes due to repeated acid leaching. Two transition elements, Cu and Ni, showed the highest mobility. Several elements, Ca, Na and Cr, had mobility index values greater than 1. 80 Ch.4-Chemical and Mineralogical. 2.5 2 4 X CD T3 C £.1.5 i H 1 1 1 h • A • B i C i i i H — i — i — ^ Cr Cu Mi H h H 1 1-0.5 0 4.5 4 + 3.5 3 + 12.5 c f o 2 2 1.5 1 0.5 | Ca 4 K Mg Mn Na l> £ Ba Oo A 1 I b Ni Rb S silt+clay fraction -I 1 h -I : = (C i / C rJumpie H h 1 t - H 1- H h 11 H i H 1 h Ca Pb K l\jg Nn Na |l Si | a cjo Cr Cu tfp Ni FJj S Sr i i Figure 43 Calculated mobility index using trench D as a reference. The average relative mobility of an element from each trench is expressed as the ratio of the relative concentration (normalized to Ti concentration) in the trench to the concentration of the reference, or least weathered trench (trench D was taken as the reference). 81 Ch.4-Chemical and Mineralogical... Values greater than 1 may result for several reasons, (1) natural heterogeneity in the samples from each trench since the mineralogy was similar but not necessarily identical, (2) there is enrichment or preferential accumulation in the post-leach (trench A and B) and leach weathering (trench C) materials, or (3) negative enrichment may have occurred if the element is more mobile under natural weathering in trench D (i.e. if elements are lost in trench D, the elements in the other trenches appear higher). For example, the apparent higher mobility of Ca in the natural rock in relation to the acid leached rock ( I c a > 1) may be explained by processes mentioned. Numerous sulphate phases precipitate during evaporation (Williams, 1990; Nordstrom, 1982); the least soluble is likely to be gypsum. In the areas of the rock dump which experience acid leaching (trench A , B, C), acid weathering may release more Ca from Ca containing minerals such as anorthite (a component of plagioclase) than from naturally weathered areas (trench D), resulting in greater accumulations of CaSCU. CaAI 2 Si 2 0 8 + 4H 2 S0 4 - » C a 2 + + 2AI 3 + + 2SiO(aq) + 4S0 4 2~ + 4H 20 Other sulphates did not appear to accumulate in post-leach and active leach areas because of higher solubility compared to gypsum (CaS04»2H20=solubility = 0.24 g/100=mL, MgS04» 7H2O=71g/100mL, Na2SO4*7H2O=19.5g/100mL, Fe I I SO 4 »7H 2 O=15.7g/100mL, Z n S 0 4 » 7H2O=96.5g/100mL; Weast, 1975). Thus, the higher mobility of Ca may be due to the formation and accumulation of Ca-S04 in post-leach and active leach areas because of the different leaching regimes. Different mobility of S in the two fractions seems unusual (higher mobility of S in the Ch.4-Chemical and Mineralogical... sand fraction compared to the silt+clay fraction). This could be the result of differential weathering or modal distribution related to the different size fractions. Price and Kwong (1997) showed the < 2mm fraction of samples collected from the Kitsault mine contained much higher sulphide than the < 50 pm fraction (silt+clay). Several trends are notable when comparing elemental sand:silt+clay ratios. The concentration of elements detected in the silt-clay fraction is greater than in the sand fraction for most (ratio values less than 1), suggesting there is greater element mobility from the sand fraction or preferential accumulation in the silt+clay fraction. The exceptions are Si, Na, and S. The Si s a:SiSiCi ratio is greater than 1 in all the samples and is higher in trenches A and B ( -1.3 ) compared to C and D (-1.2). The Na s a:Na sici ratio is near unity for most samples and is slightly greater in trench D. For S, the Ssa:SSici ratio is less than 1 in post-leach and leach trenches, but in the trench not exposed to acid (D), the ratio is greater than 1. Differences may be partly explained by a combination of the weatherability of the primary minerals in the original rock and the accumulation of secondary weathering products. Decreasing quartz content with decreasing particle size likely explains why Si s a:Si s l ci values are greater than 1 (Wilding, 1977). For other elements, factors such as acid-leaching may be an important consideration. The concentration of each element (except for Pb), in the sand fraction was significantly correlated to the amount in the silt-clay fractions (Table 4.4) suggesting that although elemental redistribution between the fractions may have occurred during sulphide weathering, the fractions are quite similar and are dominantly the result of processes of comminution. 83 Ch.4-Chemical and Mineralogical... Table 4.4 Spearman rank correlation coefficients between sand and silt+clay fractions grouped according to the level of significance. Significance Level Element P<0.01 P< 0.001 Al 0.47 Ba 0.76 Ca -0.55 Co 0.83 Cr 0.87 Cu 0.9 Fe 0.74 K 0.85 Mg 0.88 Mn 0.95 Mo 0.92 Na 0.87 Ni 0.87 P 0.83 S 0.79 Si 0.67 Sr 0.85 Ti 0.62 Zn 0.69 Zr 0.63 In order to compare colour among the samples, a comparative scale is required. Table 4.5 lists the significant relationships between the calculated Hurst index value (denoted as Hurst colour rating or Her) and total element concentration. The highest correlation coefficient values are between Her with Al and Fe. 84 Ch.4-Chemical and Mineralogical... Table 4.5 Significant Spearman rank correlations between Hurst colour rating and total elements. Parameters2 rs Significance level Hcrsicl vs. Al, i c l 0.623 0.01 Fesicl -0.591 0.01 Mg s i c l 0.506 0.01 Fesa -0.474 0.01 Na s i c l 0.367 0.05 Ssicl -0.382 0.05 0.408 0.05 Zn s i ci 0.367 0.05 M s a 0.4 0.05 pH s a 0.448 0.05 Hcrf ine Alsicl 0.699 0.01 Fesicl -0.631 0.01 ^ nsicl 0.495 0.01 %sand -0.367 0.05 Fesa -0.377 0.05 1. Colour values were converted from Soil Munsell colour to Hurst colour rating (Her) using the methc described in Hurst (1977). 2. There are three subscripts used: (1) fine indicates whole fine fraction (< 2mm), (2) sa indicates sand size fraction (2-0.05 mm), and (3) sicl indicates silt-clay size fraction (< 0.05mm). These results reflect the relationship between sample colour and various oxidized Fe minerals (e.g. hematite and jarosite) and possibly a diluting effect by Al containing minerals such as Al oxides and aluminosilicate minerals or decreasing redness associated with increased Al substitution in oxidized Fe minerals. The other correlations may be due to coprecipitaton, adsorption, or elemental abundance in primary mineral phases. Figure 4.4 shows the relationship between total Fe and redness rating for the fine (< 85 Ch.4-Chemical and Mineralogical... 2mm) and silt-clay size fractions. Hurst colour rating increases rapidly up to Her = 30 with decreasing Fe content, but subsequent changes do not appear to reflect changes in Fe. This relationship is likely the result of secondary oxidized Fe phases and will become more refined using selective dissolution analyses. In the field, waste rock in trench A between the depths 1 to 2 m appeared to be cemented and was notably more reddish-orange than other materials in the profile. Iron content increases in this zone corresponds well with decreased Her values (Figure 4.5). 86 Ch.4-Chemical and Mineralogical... 6 4-x Silt-clay fraction Fe * Sand fraction Fe 3 + 2 1 + 0 X . A . A 1 A A + •+- + 10 20 30 40 50 60 70 80 Whole fine fraction Hurst colour rating (Hcr-fines) 90 100 3 -2 -1 0 0 Figure 4.4 10 20 A A X A X + + •+-30 40 50 60 70 80 Silt-clay fraction Hurst colour rating (Hcr-sicl) 90 100 Comparison between total Fe and Hurst colour rating for the fine earth and silt-clay fraction. 87 Ch.4-Chemical and Mineralogical... 4.4 Conclusions The particle size characteristics of these materials are largely the result of the mode of waste rock deposition, the competence of the rock material, and physical weathering occurring on waste rock dumps resulting in comminution of fresh geological material. Examination of the fine sized fraction (< 2 mm and < 0.05 mm) reveals that many of these phases can not be definitively identified without further processing of the samples. Based on colour, samples appear to have pigmenting minerals consisting of oxidized iron phases. The fine sized material is mainly of detrital origin and reflects the mineralogy of the rock dump. Elemental analyses reveals some differences between the sand and silt-clay fractions, and the different weathering environments. Calculated elemental ratios may be useful as weathering or mobility indices. Compositional differences between the size fractions may be a result of variations in the strength, cohesion, weatherability and distribution of primary minerals in the original rock, and (2) the preferential removal or accumulation of mineral phases (Price and Kwong, 1997). Some trends are evident when examining the weathering regimes and particle sizes. Copper has been mobilized by acid leaching, which is to be expected in a acid leaching operation. Copper levels in samples collected from "abandoned" leach sites contained levels 2- 20X less than in other samples. Hurst colour rating, a numeric conversion of Munsell colour, is significantly related to several elements suggesting morphology may be a useful first approximation for elemental concentration. Many of the relationships may be coincidental and due to the relationships 89 Ch.4-Chemical and Mineralogical... between Fe and primary mineralogy. Oxidized iron phases, usually credited for the reddening of soils, and implied to be present based on colour, are significantly correlated to Her. Thus collection of samples stratified by morphological features, may reveal important information on the geochemical processes occurring within a rock dump. Relationships related to weathering intensity, mobilization and attenuation of elements, eluviation and illuviation from the fine fraction material, and authigenic mineral phases may be examined by morphological features. 90 Ch.5-Distribution and Characterizaton 5. Distribution and Characterization of Stored Weathering Products in Acid- and Non-Leached Waste Rock 5.1 Introduction The dissolution and precipitation of stored weathering products are important considerations affecting the composition of waters associated with mine sites (Chapter 2). Precipitated weathering products are metastable intermediates and can be considered stored or temporarily retained until subsequent re-dissolution. Several secondary iron-sulphate minerals (e.g. romerite, copiapite, coquimbite, melanterite, szomolnokite, and rozenite) have been identified in mineral suites contributing to groundwater and storm runoff chemistry from mine sites (Cravotta, 1994; Bayless and Olyphant, 1993). Secondary goethite in rock dumps can retain Al , Cu, Zn, Si and S (Lin, 1996) which may contribute to future drainage if geochemical conditions change. The weathering/dissolution of stored secondary weathering products (i.e. secondary minerals) may act as controls over pore water chemistry and metal loading. Site-specific solubilities for primary and secondary minerals are dependent on leaching intensity, pH, the aqueous activities of complexing ligands, and, for redox-sensitive metals, the redox potential (Rai and Kittrick, 1989). Redistribution of elements in a rock dump is similar to that in a soil in that it is a dynamic process and is controlled by chemical and physical conditions. For example, during pyrite oxidation in acid sulphate soils, much of the Fe released by pyrite oxidation remains in the soil profile, but only a small fraction of the sulphate is retained, as jarosite or gypsum (Dent, 1986). During gossan formation, the dominant feature controlling the mobility of many elements is the interaction between the amount of Fe in the sulphides and the pH of the 91 Ch.5-Distribution and Characterizaton reactions (Thornber, 1985). The bulk of the Fe oxide phases in gossans overlying oxidized sulphide ores are hematite and goethite (Williams, 1990). {" In soil science, the differential dissolution behavior of secondary minerals is used widely for chemical and mineral analyses and is called selective dissolution analysis (SDA). These techniques are generally used for several purposes: (1) to remove cementing agents prior to particle size separation of soils or to "clean" the main components of a soil for further analysis, (2) to estimate the amounts of phases which are non-crystalline or present in low concentration, and (3) to assess the trace element and heavy metal status in soils (Ure, 1996; Fallman and Aurell, 1996; Borggard, 1988; Jackson et al, 1986). Ideally, the extractants selected should target specific phases for removal from surfaces while leaving other constituents unchanged, but under naturally occurring conditions, there may be several minerals present with similar dissolution properties. Removed phases are operationally defined and based on the dissolution technique. It is incorrect to state that specific minerals are extracted since dissolution techniques are tested on dissolution properties and not on mineralogy (Borggaard, 1988). Several techniques have been used to characterize Fe (and Al-Si) phases in soils (Borggaard, 1988; Dahlgren, 1994). These techniques generally work by exposing the sample under given pH or redox conditions to a chelating agent at a selected sample:solution mass ratio for a set time. For example, potassium or sodium pyrophosphate (PYRO) solutions are used to determine organically-bound Fe and Al (McKeague, 1967). This method has been the basis for differentiation of Podzolic B horizons in Canada since 1973 (Carter, 1993). Amorphous iron 92 Ch.5-Distribution and Characterizaton oxides may be extracted using either ethylene diamine tetra-acetate (EDTA) or acid ammonium oxalate (AAO) solutions. The nature of the EDTA fraction seems to consist of water-soluble and exchangeable Fe, organically complexed Fe, and poorly crystalline or amorphous Fe oxides (Borggaard, 1988). A A O solutions dissolve organically complexed Fe and amorphous inorganic Fe, Al and Si oxides from soils (McKeague and Day, 1966). The phase removed changes depending on the extraction period (Wang et al., 1993). The more crystalline fraction of pedogenic oxides and hydroxides can be removed using the citrate-bicarbonate-dithionite (CBD) extraction. The CBD method, considered to be less specific and more harsh, is used to determine the free iron oxides (i.e. crystalline goethite and hematite), amorphous coatings, and associated metals such as Si, Al and Mn (Jackson et al., 1986; Mehra and Jackson, 1960). Selective dissolution analyses have been used to analyze sediments and precipitates formed in waters impacted by mine drainage. Mineralogy of iron precipitates from a constructed wetland receiving acidic drainage were characterized by A A O and CBD extractions (Karathanasis and Thompson, 1995). Bigham et al. (1996) analyzed precipitates associated with sediment samples from 28 mine drainage sites using a combination of techniques including A A O solutions. Fonseca et a/.(1992) used A A O solutions in a sequential extraction scheme to characterize Cu minerals. Results from the previous chapter suggest weathering processes lead to metal re-distribution in the Gibraltar rock dumps identified by morphologically different zones. The aim of this study is to characterize the geochemical redistribution of metals stored in the form of secondary weathering products from acid- and non-acid leached waste rock from the 93 Ch.5-Distribution and Characterizaton Gibraltar mine site using SDA techniques. The SDA techniques selected were the A A O and CBD procedures because of their extensive use in the literature and its selectivity for Fe phases. Samples were selected randomly but stratified using morphological features as sampling boundaries (Chapter 4). Relationships will be examined between different sampling zones and locations and possible stored secondary weathering products. 5.2 Methods Sample collection and methodology, preparation prior to analyses, and characterization are described in detail in the previous chapters (Chapters 3 and 4). In summary, four trenches, encompassing three weathering regimes defined by the leaching activity at the time of sampling, were sampled. Two trenches, A and B, were located in an area where acid-leaching had ceased two years prior to sampling (post-leaching). Trench A was located near the crest of the dump, and trench B, away from the dump face. Trench C was located near the crest of the dump in an area where acid leaching was active. Trench D was located in an area where acid leaching had never taken place. Bulk sample characterization from Chapter 4 consisted of paste pH, colour description, total major and minor metals, total sulphur, total carbon (selected samples), and bulk mineralogy. The two SDA reagents/procedures used to study the distribution of metals were: (1) acid ammonium oxalate (AAO) and (2) citrate-bicarbonate-dithionite. (CBD). Two size fractions were obtained: sand (2.0 - 0.05mm) and silt-clay (< 0.05mm) fractions. Sand fractions were crushed, to break-up coatings, in a agate mortar to pass a 100 mesh stainless steel sieve prior to 94 Ch.5-Distribution and Characterizaton extractive analysis. A A O and CBD extraction followed the method of McKeague and Day (1966) and Mehra and Jackson (1960) as modified in Lavkulich (1982). Solution phases from A A O and CBD were isolated by centrifugation at 900g. Solutions were stored in the refrigerator (4°C) for no more than 24 hours prior to analysis. A A O solutions were analyzed for Al, Fe, Mg, Si, Cu, Mo, Zn, Na, K, Mn, and S. Total S was determined (by Leco S) in the residues allowing for the calculation for A A O extractable S by difference. CBD solutions were analyzed for Al, Fe, Mg, Mn, Si, Cu, Mo, and Zn. All elements (except for sulphur) were measured by atomic absorption spectrometry using a Perkin Elmer AAS model 306 instrument with either an air-acetylene or nitrous oxide-acetylene flame. CBD extractable Na and S were not determined because, (1) Na and dithionite are reagents in the procedure, and (2) there is a remote possibility of sulphide precipitation in the procedure. Data for the fine earth fraction (< 2 mm) was recalculated from the sand and silt-clay fractions. Fine earth fraction data was determined by accounting for the mass contribution each size fraction contributed per unit mass of sample. For example to convert to fine earth fraction FCAAO from silt-clay and sand fraction data: FeAAo, fine earth = (FeA o,siit+ciay)x(%silt+clay in fine earth fraction) + (FeAAo,sand)x(%sand in fine earth fraction) Data were examined for normality and homogeneity of variance prior to selection of an appropriate analysis of variance. If data did not meet the requirements of homogeneous 95 Ch.5-Distribution and Characterizaton variances and normal distribution, non-parametric statistical methods were used to test groups. Comparison of two groups of data was performed by either a two-sample t-test or a Mann-Whitney U-test. Three or more groups were compared using either Tukey's multiple comparison test or a non-parametric analogue of Tukey's test (Zar, 1984, p.200). The degree of correlation among different properties was indicated by the Spearman rank correlation coefficient. The level of significance for all testing was P <0.05 unless specified otherwise. 5.3 Results and Discussion Complete raw data from analyses of the extraction of the sand and silt-clay fraction using A A O and CBD techniques are presented in the Appendix. Non-parametric testing methods were utilized for all the data. SDA data summarized according to each trench are shown in Table 5.1 and 5.2. Several general statements can be made regarding the data. Prior to any treatment, sample examination under a microscope showed a variety of weathering products coating the rock surface. For instance, crystalline gypsum and oxidized Fe were clearly evident throughout these samples. After A A O and CBD extraction, grain surfaces appeared clean and the surface of mineral grains were clearly evident. The amount of metals extracted from the various size fractions generally were correlated (P<0.05) with each other (Figure 5.1). The only exception was the poor correlation (rs = +0.17) for NaAAO between the silt+clay and sand fractions. These results suggest the fine earth, sand, and silt+clay fractions generally reflect similar trends in waste rock samples collected from a variety of locations. 96 Ch.5-Distribution and Characterizaton ,ho tN co N I o o o DO ^ O — CS OO lo o o o N O ifl N 1 _ rt — S to a; — — CS o o o OO NO oo co cs NO CO CS NO cS o d d © •sss 2 c7> oi o o o o Tf —• NO CO ON r- oo TT o o © o m — Tf — ro cs r— — H i 2 2 S u S l 2 OO CS Tf NO O o S S N H — NO CS r- Tf rs co d d J d o o o o © © o o Th m Tf Tf NO CO CS CS r- rs o «n d d J d £ .3 s s NO Tf CN ifl N ° H u Q 1 „ o o 2 o wi TT es o o o r- ON ON CO — ' N O o © 2 o TC uo L; o r- — £ cs Tf ro 2 — oo CN J - H ON © © - H O 3 .S s o o o o Tf cs r- CN o o © © m cs oo rs I © © © ©I f~- CN Tf «-H I cs cs r- — I - • 5 2 2 © © © ©I S CO OH 97 Ch.5-Distribution and Characterizaton W K) » to oo 2 2 i 5 to os 2 S S S S 8 § S ° S 3 ? g f l fN vO > 2 1 » i s o o o o — OO 00 - H Tf - VO (N r- o\ \o 2 2 J -l i s 2 to a: 8 8 8 8 fN — Tf — o o — o S .s 2 2 2 to as Q S- 00 E in N oo oi 8 2 8 § - M V D ~ 3 8 S g 2 r- g r-m oo a 3 .= I 5 W 00 ^ ^ CO vo r-a q = » 3 S 2 to 05" - m 2 ^ r- X t-8 R 8 2 ^ tN co M O Q ii O C N O S cn \0 m 2 ^ O O O S w Q; u o o o o oo OO IZl 1 CN — so > 2 2 98 Ch.5-Distribution and Characterizaton Ch.5-Distribution and Characterizaton Correlation between the sand and the silt+clay with the fine earth fraction was expected since the two finer fractions were used to determine the latter. Correlation coefficient values for the fine earth fraction were included for completeness. Correlation coefficient values for the two extractions are summarized for the metal suite analyzed (Figure 5.2). Several pairs of metals were very highly significantly correlated (P<0.001) in all size fractions: A A O extractable metals, SiAAo 3 - AIAAO , ZnAAo - MgAAo, ZnAAO - MnAAo, and for CBD extractable metals, FecBD - MOCBD and MgcBD - MncBD- These metals may be closely associated in secondary weathering products or in their chemical behavior (e.g. similar solubility). From here on, the discussion will focus on the results for silt+clay fraction due to its greater surface area and reactivity, but applies to all the size fractions unless indicated. acid ammonium oxalate extractions Acid ammonium oxalate extraction removed metals from the samples (sand and silt-clay fraction) in the order : Fe » Al > Si > Cu > Mg > Mo > Zn (mass basis). A A O solutions were more effective than CBD solutions for extracting Cu, probably the result of the different extracting conditions. Both A A O and CBD solutions utilize chelating agents, but the former is buffered at a lower pH and consequently, Cu is more soluble and extractable. 3 SiAAO is read as "acid ammonium oxalate extractable silicon". 100 Ch.5-Distribution and Characterizaton Ch.5-Distribution and Characterizaton The quantity of A A O extractable metal was related to pHSiCi (sand fraction not shown): Cu Si ci, rs=+0.76 (P<0.001); Fe s i d , rs=-0.57 (P <0.001); M g s i d , rs=+0.46 (P<0.05); M n s i d , rs=+0.76 (P<0.000); Mo s i c l , rs=-0.52 (P<0.005); S s i d , rs=-0.61 (P<0.001); S i s i d , rs=+0.50 (P<0.005); Zn s i d , rs=+0.67 (P<0.001). The results agree with data indicating base metals have increased solubility under acidic conditions (Baes and Mesmer, 1979). The observed increase in FeAAo with decreasing pH may be the result of the presence of Fe-S04 phases, or sorption of SO4 " onto amorphous Fe phases, which are soluble in the A A O extraction. This is supported by the correlation between FeAAo and SAAO- The greater amount of FCAAO and CUAAO (wt basis) in the silt-clay fraction than in the sand fraction is likely due to the higher surface area of the silt fraction. The data from each trench is generally quite variable but a trend exists for extractable Fe and Cu levels. There is at least 3X more FeAAo in trench A and B than in trench C and D and at least 4X more CUAAO in trench C & D than in trench A and B (in both silt+clay and sand fractions). These observations are likely related to the leaching history of areas in the vicinity of each trench. In post leaching areas (trench A and B), the absence of acid leaching through the rock favors the accumulation of precipitated oxidized Fe phases which are likely to form when there is neutralizing and/or diluting water. The accumulation of oxidized Fe and depletion of acid consuming minerals (due to acid leaching and noted by lower pH values - Chapter 4) suggest post leach areas experience an intense and accelerated weathering environment. The greater amount of CUAAO in trench C and D can be explained by the location and weathering regime of this trench. Trench C and D located in areas where there 102 Ch.5-Distribution and Characterizaton are higher levels of Cu reserves, and have received less (trench C) or no (trench D) acid leaching, than the areas near trench A and B. The dominant copper forms are likely to be hydrated copper sulphates, which are readily formed in the presence of excess SO4 2 " from oxidation during sulphide weathering (Williams, 1990). Literature indicates that A A O soluble Fe phases consist mainly of ferrihydrite and schwertmannite with small amounts of lepidocrocite and goethite (Bigham et al., 1996; Borggaard, 1988; Schwertmann et al., 1982). The molybdate anion reacts strongly (adsorption) with iron hydroxides (Bohn et al., 1985) explaining the correlation observed between FeAAO - MOAAO (for silt-clay, rs=+0.65 P<0.001). In addition, A A O extracts poorly crystalline aluminosilicates such as allophane and imogolite (Jackson et ah, 1986) which explains the strong correlation between SIAAO - A1AAO (Figure 5.3) (silt-clay fraction, rs=+0.81 P<0.001). The observed correlation between ZnAAO and MgAAo may be associated with extracted Cu phases because Zn and Mg are at significantly correlated to CUAAO- Mg, Zn, and Cu have a similar coordination number (6), ionic radius, and charge suggesting these metals may coprecipitate. Williams (1990) indicates substitution is common for all the simple hydrated sulphates of divalent metal ions, especially near oxidizing sulphides. Another contributing factor maybe the correlation that exists between pH and ZnAAO (silt-clay, rs=+0.67 P<0.001) and MgAAo (for silt-clay, rs=+0.46, P<0.05). Ferric iron containing minerals not completely dissolved by A A O are hematite, goethite, and jarosite (Schwertmann and Taylor, 1989). Biotite and chlorite appear to undergo some decomposition in A A O extractions (Jackson etal., 1986). 103 Ch.5-Distribution and Characterizaton < 4 © o o NO o o o o o o T T 1 o t3 O Gj o h ro <u o o o CN o o o o o o C N o o NO o o CN o o 0 0 o o T T IS siqepBipra Q W e o ••a 0> e S 2 o = 4» en e JO 88 1 CO in s WD 104 Ch.5-Distribution and Characterizaton citrate bicarbonate dithionite extractions CBD extractions generally target Fe oxides (including goethite and hematite) and any associated metals such as Si, Al and Mn. Other ferric iron containing minerals such as magnetite and ilmenite are not removed in significant quantities (Jackson et al., 1986). The technique extracts Fe oxides by reductive dissolution of Fe 3 + , but may remove some structural Fe 3 + from vermiculites, smectites (nontronite) and chlorites (Jackson et al., 1986). CBD treatment removed metals in the order (high to low): Fe » Si > Al > Mg > Mn > Mo > Cu > Zn.. CBD solutions are more effective than A A O solutions for extracting Fe, Al , Si, and Zn. There is more FecBD and SJCBD (mass basis) in the silt-clay fraction than in the sand fraction. For both the silt-clay and the sand fraction, FecBD in trench A is at least 2X greater than in the other trenches. Several metals have a relationship with pHSjCi (sand fraction not shown): Fe s i c l , rs=-0.65 (P<0.001); Mg s i c l , rs=+0.56 (P<0.005); M n s i c l , rs=+0.71 (P<0.001); Mo s i c l , rs=-0.68 (P<0.001). The correlation between Fe C B D and M O C B D (for silt-clay, rs=+0.56, P<0.005) is probably the result of sorption of Mo with Fe hydroxides, while the relationship with pH is likely due to increased Mo adsorption to oxidized Fe as pH decreases. The correlation between MncBD and MgcBD maybe due to a correlation with pH. differences between trenches The amount of each metal extracted using A A O and CBD methods was tested for statistically significant differences and results summarized in Figure 5.4. 105 Ch.5-Distribution and Characterizaton Whole fine AAO Sand Silt Silt A B C D A B C D A B C D A B C D A B C D A B C D CBD A B C D A B C D A B C D A B C D A B C D A B C D A B C D A B C D Trench identification is indicated on the top and right side of each triangle. Significantly different (P<0.05) trenches are indicated by shading. Figure 5.4 Comparison of AAO and CBD extractable metals from each trench. 106 Ch.5-Distribution and Characterizaton For many of the metals (e.g. Al , Ca, K, Mg, Na, Zn), there are no statistically significant differences between the four trenches suggesting that for most metals remobilization is occurring but acid leach weathering does not result in statistical differences from post leach and natural weathering areas of the rock dump. Some of the observed trends noted in the previous section have resulted in differences that have lead to statistically significant differences (e.g. Cu). Soluble secondary minerals such as melanterite, coquimbite and gypsum are likely to be ubiquitous throughout the surface of the Gibraltar rock dumps, regardless of the weathering intensity, and can be easily dissolved during wetting events under field conditions in a rock dump, mobilizing Fe, Mg, Ca, and SO4 ". Precipitation of less soluble secondary weathering products will lead to the accumulation of some metals in larger quantities. Many of the differences may be explained by the differences in the acidity in each trench. The highest mean paste pH of the four trenches was from trench C. This may be due to the accumulation of acidic secondary weathering products accumulated in post-leach and natural weathering areas which act as an "acidity reservoir". In areas of active acid leaching, the "acidity reservoir" can not be established because of the leaching frequency (see Chapter 4 Results and Discussion). Another explanation may be that there is a possible difference in sulphide acidity generation. The form of secondary aluminosilicate phases depends on pH and the composition of major cations in the solution (Bohn et al., 1985). Molybdenum in the form of molybdate could be retained by coprecipitation and likely exists as a component in solid solutions of iron, aluminum, and silicon oxyhydroxides and aluminosilicates. 107 Ch.5-Distribution and Characterizaton Molybdate solubility increases with pH (Bohn et al., 1985) explaining the significant negative correlation observed between MOAAO and solution pH for the sand and silt-clay fraction (rs=-0.67, P<0.000; rs=-0.52, P<0.005). The differences noted for C U A A O can be attributed to differences in acidity as well. extractable iron ratios The ratios for FeAAc/FecBD, FeAAo/Fe t ot, and FeAAo/SAAO are presented in Table 5.3. These ratios are useful to examine changes in the forms of Fe in the samples and various zones. Oxalate to dithionite ratio values have been used to indicate the crystallinity of oxidized Fe phases in soils and mine water precipitates (Karathanasis and Thompson, 1995; Schwertmann, 1993; Murad, 1994; Bigham et al., 1990). In the Gibraltar waste rock samples, FeAAc/FecBD range from 0.3 to 1.1, in the silt+clay fraction. As indicated previously, schwertmannite, ferrihydrite, and other amorphous Fe phases are completely soluble in A A O solutions, whereas goethite, hematite, and jarosite are not and are more susceptible to CBD extractions. Thus, as the content of goethite/hematite/jarosite in a sample increases, the values for oxalate soluble to total oxide Fe (FeAAo/FecBD) decreases. The values for oxalate soluble to total Fe (FeAAo/FeToT) are smaller in magnitude due to the presence of Fe-containing primary minerals but mirror the FeAAc/FecBD values. Bigham et al. (1996) indicate that as the amount of oxalate soluble content increases, there is greater amounts of schwertmannite and ferrihydrite. 108 Ch.5-Distribution and Characterizaton •a S 2 u £ o o J= E * i f O O Tf —' © Tf O O cn — CN — m CN •-* © © — I CN n - n c N - ^ o — Ice H T t m o o \ o > o c ? - o o ©> — C O — NOTf — NO cn in d d o cn C O CN d d © in >n cn NO — CN d d N H ON 00 Tf — d d o o o o o o o o © I o o o o o o o o o NO H M (N 00 Tf CN m © d d d d d d d d d l 3 r - i n — — o — d o d d o o o o o o o o I o o o o o o o o o I o o o o o o o o o r - N O T f N o o c N — in c n m o o N O — cnTf © © © © J © © T j - c o i n o t - ^ c n i n o o i n N O O N c o r - c o m m d d d d d d d d o o o o o o o o o o — — © © © © o o i n r - c N O N C N c n cs cs — — o d d \< <<<<<<<< [— — O O in ON NO fN CN CN >—• — d d d C Q C Q C Q C Q C Q C Q C Q C Q oo — o o i n N o i n i n c N O N Tj-TtincncN«ncoTj-inON d d d d d c N O — CNO O O O O O NO NO CN O — CN — in t— fN — oo TT CN CN ON m r- CN NO CN Tf cn NO o d d © © CN — — © o o o o o o o o o o S c n T f c n T f c o m o o o c N O O O O — © — O C N o o o o o o ON Tf oo o NO cn ON t~~- N O cn m o o m r - - T f r - ~ > n N O T f O ddddddddd* c o m c o T t i n m o N O N o o c n o N c n r - T f r - . \ o N O T f o o o o o o cn o in r> in o d d Tf cn — p oo r-. CN CN CN CN — — —< CN i n U U U U U U U U U U o o o cn O O O cn ON Tf ON NO co cn m rn © © — — — ON © — o o © © © © © o o © © © © © © © © © —• oo co CN — in m O NO co oo in o - ; o o o o o © — © o o o © © o © © © © fN ON NO rn — ON N O — d d d — © © Q Q Q Q Q Q Q — CN 1> 109 Ch.5-Distribution and Characterizaton Schwertmann (1993) described two ferrihydrite containing soil samples with FeAAc/FecBD = 0.69 and 0.90. Poorly crystalline weathering products phase would be expected to form in mine waste since crystal size is a reflection of the conditions during crystallization as well as its inhibition by interfering compounds such as organic substances, phosphate, silicate, and Al (Schwertmann and Taylor, 1989). Some research has indicated that aging of oxidized Fe phases leads to decreasing FeAAc/FecBD, suggesting greater crystallinity (Schwertmann, 1993). At this time, the existence of such a relationship in mine wastes is unconfirmed. The oxalate soluble to oxide Fe (FeAAc/FecBD) ratio values appear to be related to sample morphology. Considering the silt+clay fraction, samples with HcrSiCi < 30 have an average FeAAc/FecBD of 0.89 ± 0.19 and samples with HcrSjCi > 30 have an average of 0.47 ± 0.15. Samples with higher oxalate content tend to have lower HcrSici values (for silt+clay fraction data, r = -0.62), suggesting that these zones in the rock dump are typically dominated by poorly crystalline Fe precipitates likely including schwertmannite, ferrihydrite, and/or amorphous Fe phases. These results appear to be consistent with observations by other researchers indicating the presence of high levels of organic matter and SO42" may hinder or retard the formation of goethite and favor the formation of poorly crystalline ferrihydrite or Fe oxyhydroxysulphates (Karathanasis and Thompson, 1995; Schwertmann and Taylor, 1989; Brady et al., 1986). Oxalate extractable S increases with FeAAo/FecBD values, suggesting decreased crystallinity, and decreasing Hurst colour rating Values for F6AAO/SAAO have been shown to be a valuable tool when examining Fe-SO4 mineralogy in precipitates from acidic solutions and waters. Molar FCAAQ/SAAO ratio 110 Ch.5-Distribution and Characterizaton values range from 0.2 - 6.9 for the silt+clay and sand fractions (Table 5.3). Typical Fe/S ratios for Fe oxyhydroxysulphate precipitates ranges from 3.5 - 5.0 (Karathanasis and Thompson, 1995; Lazaroff et ah, 1982). Bigham et al. (1990) reported that for schwertmannite precipitates, typical FexoT/STOT mole ratio values ranged from 4.6 - 8. Molar FeAAo/SAAO values for schwertmannite will also range from 4.6 - 8 since this mineral is oxalate soluble. The Fe/S ratios observed for the Gibraltar samples are generally lower than those noted for schwertmannite and oxyhydroxysulphates. Samples with lower ratios may be attributed to the presence of other sulphate phases (e.g. Ca and Cu sulphates) and jarosite which ideally has a Fe/S = 1.5. Hurst colour rating and extractable iron. Fe is the element with the largest extractable amounts from these samples, regardless of the technique (AAO or CBD) or size fraction. Much of the extractable Fe is likely in an oxidized form and is the most significant contributor to the sample morphology (i.e. colour). Samples exhibiting more intense redness or low Her tended to have FeAAo/FecBD > 0.5, suggesting that the amorphous Fe phases contributed more to the redness rating than the crystalline phases. The amount of FCAAO and FecBD are significantly correlated (P < 0.001) with HcrSi ci (Figure 5.5). Ill Ch.5-Distribution and Characterizaton 8 T 7 -6 --5 --4 3 2 1 + 0 0 7 T 6 -X A X A A " X X X X i x —I— 20 40 60 Silt+clay fraction colour rating (Her) x A A X X A x A A A X * « A + A X X X A A | X A X X * « 20 40 60 Silt+clay fraction colour rating (Her) x 80 * 80 A silt-clay x sand 100 x X X —I 100 Figure 5.5 Extractable Fe concentrations plotted against silt+clay fraction colour rating. 112 Ch.5-Distribution and Characterizaton Although isolation of the whole fine fraction (i.e. less than 2mm) may be simpler in the field, Munsell colour for the silt-clay fraction is more uniform, and thus easier to determine. Regression equations for HcrSiCi and Fes;ci are: (1) FeAAO.sicl = (2.8 x 10 6)Hcr s i cf L 5 7 R 2 = +0.76 (2) FeAAO,sicl = -9350 + 815300/Hcrsicl R 2 = +0.84 (3) FecBD.sicl = (1.1 x 10 6 )Hcr s i c f U 5 R 2 = +0.76 (4) FeCBD,sici = -3080 + 810500/Hcrsici R2 = +0.89 For FeAAO and FecBD the inverse relationships (equation 2 and 4) fit the data best. At the upper and lower range for Hcrs;ci, the inverse relationship appears to overestimate and then underestimate FeAAO- Intuitively, the power relationships are not as favorable because of the room for error due to the large multiplication factor (106). Generally, significant changes in levels of Fe occur as FfcrSiCi decreases below 30, which corresponds to approximately 0.5% FeAAO and 1% FeCBD-As the value of HcrSjCi increases above 30, the amount of Fe A A o and FecBD from the samples remains nearly constant, indicating the lower detection limit has been reached. Lower detection limits may be achieved by using photoelectric tristimulus colourimeters or diffuse reflectance spectrophotometers. Both these instruments have been used successfully to measure soil colour which can be converted to Munsell colour notation (Torrent and Barron, 1993). In areas of sulphide oxidation, as weathering increases in duration and 113 Ch.5-Distribution and Characterizaton intensity, and oxidized Fe precipitates accumulate, Hurst colour rating may be used to obtain an approximation of the amount of secondary Fe retained in the rock dump. Calculated colour ratings can be influenced by several factors. Evidence indicates that as crystal size decreases, minerals become less red (Schwertmann, 1993) and Her rises, thus any factor that might influence crystallinity will affect Her. These factors include the presence of Al , Si, organic matter, or any compounds that interfere with precipitation. The moisture content and thickness of the coating will also affect Her values. Type of mineral phase present will significantly alter the Munsell colour and thus the value of Her. Alpers and Brimhall (1989) indicate naturally occurring hematites, jarosites and synthetic goethites have colours ranging from 10R 4/6 to 10R 5/8, 2.5Y 8/6 to 5Y 8/10, and 10YR 6/8, respectively, which corresponds to Her values 6-7, 20-30, and 15. The presence of gypsum or silica leads to an increase along the value axis in the Munsell notation (Alpers and Brimhall, 1989), which would increase the Her value. comparison of red (HcrSjCi < 30) and non-red (HcrSiCi > 30) samples. Samples with values of Hcr sici < 30 (i.e. red) tend to have accumulated the most secondary weathering products based on extractable Fe content, but through mechanisms like co-precipitation and occlusion, other metals may have accumulated (Chapter 2). Using Hurst colour rating of the silt+clay fraction, extractable metals were compared between two morphologically (colour) different groups of samples , "red" and "non-red", and summarized in Table 5.4. 114 Ch.5-Distribution and Characterizaton IS V o d V 1 l l 60 1 ^ v b S 1 60 V S3 60 CN o\ q ^ ™ s d ° ° ' ^ vo "1 3 d <=> <=> d 3 -t -I - ! o o o o o V * » » 1 d d <N 2^3 co T-H T-H C N o <5 <5 <5 o o o O ^ 1 ^ CJ " " O O ^ j - J O O O R O R « n C N T-H ™ "1 o <~1 ~ 1 o vo O O ^ d O O O r S a\ r-d d <N JT; o o o o d o d r ^ d o j , bo a o c d , _ t*"1 1/H *-< ^ O <N •* ^ ^ 'I ^ ^ O '-' O O O O OO t-H 00 •* o o o <-< © d 0 0 d ° d ° d 0 0 d ^ d O d ' - ' O O O O o ro 00 t> d d f t r i d d d H H o H i—* C O T-H T-H V O co d d d .-< 3 ^ O ^ ^ ^ c S ^ S <=>. t-O O r-I o cn CN Q oo d d ^ ~ M ^ v! n tN H n d ,-; ' - ' d d d d 1 o n " 1 —I d m o O O H H T ~ - f l r t > 6 0 f l O . T H T -8 ff 115 Ch.5-Distribution and Characterizaton Extractable metals that were significantly different ( P < 0 .05) in the two groups were: (1) A A O extractable Al , Cu, Fe, K , S, Si (all size fractions) and Mo (sand fraction only), and (2) for CBD extractable Al , Fe (all size fractions), Mo (fine earth and silt+clay fractions), and Si (silt+clay fraction only). As expected, FeAAO and FecBD are significantly different in the two colour groups. Extractable Mo, Si, S, Al , and Fe are higher in the red samples, and K and Cu are higher in the non-red samples. For Mo, Si and S, adsorption/occlusion of M0O4", soluble Si, and SO42" with oxidized Fe phases tends to increase with decreasing pH in the presence of abundant sesquioxides (Bohn, 1985). Higher S levels in the red samples is likely the result of the presence of sulphate containing Fe oxyhydroxides, which will contribute significantly to the sample pigmentation. The presence of Al-containing Fe oxides (goethite), which are common in surficial weathering environments (Schwertmann and Fitzpatrick, 1992), could explain the higher Al concentrations in the red samples. Dissolution of small amounts of primary minerals like epidote, zoisite, or chlorite could contribute to extractable Al and Fe. Unlike extractable Fe (FCAAO and FecBD), there is more Cu A A o and K A A O in the high Her samples than in the low Her samples. This may be explained by two possibilities: (1) competition between Cu and Fe for sulphate to form divalent metal sulphate phases, and (2) the ability of Fe to form low solubility oxidized Fe phases in the lower pH range, whereas Cu and K tend to be remain soluble and mobile. For example, jarosite has been identified in acid sulphate waters and tends to form in the pH range 1.5 - 3.0 in the presence of [SO42"] > 3 ,000 mg/L (Bigham, 1994). 116 Ch.5-Distribution and Characterizaton comparison of red samples between each trench. The composition and accumulation of secondary weathering products in red samples may differ in each sampling trench due to unique geochemical conditions and secondary mineral assemblages (pH, leaching, aging). Red samples collected from each trench were compared using the Kruskal-Wallis test for non-parametric data but due to the small number of red samples, results must be evaluated with caution (Figure 5.6). Statistically, the red samples from trench D contained more CBD extractable Al than those from trench A. Similarly, trench C contains more CBD extractable Fe than those from trench B. This seems to suggest there is a post-leaching effect possibly related to rearrangement of secondary minerals as they age but this is not apparent in all the trenches. The few differences in the various trenches suggests that the geochemical differences in the trenches are not significant enough to alter the amount and composition of secondary weathering products present or that these zones of accumulation tend to be similar. Although weathering is intense in these rock dumps, weathering is generally considered in terms of geological time thus differences, between trenches and in similar zones from different trenches, may yet develop with time. comparison of trench A and C. These two trenches offer an opportunity to compare samples in similar areas of the rock dump but experienced different leaching activity (Chapter 3 and 4). The profiles in these trenches showed highly-structure stratification unlike the other trenches (Chapter 4). 117 Ch.5-Distribution and Characterizaton A B C D A B C D for cbd Al D A B C cbdFe \ C for \ | D fines and si+cl fractions A B fines and si+cl fractions Trench identification is indicated on the top and right side of eacl Significantly different (P£0.05) trenches are indicated by shading Figure 5.6 Comparison between each trench, of the amount of metal extracted from samples with low HcrSiCi. Figures 5.7 and 5.8 present data for total (Chapter 4), A A O , and CBD extractable Al , Fe, and Cu from trench A and C. In general, extractable metals fluctuate with total elemental analyses. As suggested in previous sections, Al tends to be associated with Fe (Figure 5.7 and 5.8). Zn levels appear to increase with depth, suggesting it is removed from the surface and transferred downwards. Comparing trenches A and C, two extractable metals, Cu and Fe, appear to behave differently. Of the other elements analyzed, the average concentration in trench C tends to be higher than in trench A. Trench A samples have much higher FCAAO and FecBD than those from trench C. Leaching with sulphuric acid in trench C has removed the less stable weathering products before further stabilization could occur with aging. As a result, precipitated weathering products in post-leach areas may become more stable and less soluble with aging, which has 118 Ch.5-Distribution and Characterizaton been observed for Fe3+ as ferric hydroxide ages (Feitknecht and Schindler, 1963). In the post-leach areas of the Gibraltar rock dump, the lack of acid leaching and the presence of reserve acidity may be conducive to mineral rearrangement. A hardened zone was encountered at the depth of 1 - 2 metres in trench A. Samples collected had the lowest HcrSiCi and highest FeAAO and FecBD levels, which would suggest secondary Fe was an important component of the cementing agent. In addition, relative to Fex there was more FCAAO and FecBD in trench A, indicating these samples had more secondary Fe. There was more Fex, FeA O> and FecBD in the silt-clay fractions than the sand and whole fine fraction, due to the greater surface area per unit mass. 119 Ch.5-Distribution and Characterizaton Ch.5-Distribution and Characterizaton rr ci CN »— © * n © »r> © © © © © © (N — — O O o" O O © © O O O O O O £ 5 "< G 121 Ch.5-Distribution and Characterizaton CUCBD and CUAAO are notably higher in trench C compared to trench A. From the standpoint of acid leaching, this is to be expected since there are significant Cu reserves in the active acid leach areas. As mentioned previously, levels of C U A A O are much higher than CUCBD , probably the result of the lower pH in the A A O extraction solutions. Secondary Cu phases are a significant proportion of C u T in trench C compared to trench A, as indicated by high CUAAO- Under active acid leaching, more Cu (from primary phases) is mobilized and redistributed into various CUAAO phases. Aging of oxidized Fe weathering products, in trench A, is likely to lead to reduced levels of associated Cu (and other metals), through mineral rearrangement and reduced adsorption onto Fe oxides (Okazaki et ah, 1986; Shuman, 1977). Unlike Fe, Cu appears to have been leached near the surface and has accumulated at greater depths. This effect appears more pronounced in trench C, likely due to more intense and continuous leaching. 122 Ch.5-Distribution and Characterizaton 5.5 Conclusions Selective dissolution procedures commonly used in soil science have been successfully applied to characterize secondary weathering products stored in samples collected from non-leached and acid leached areas of a waste rock dump at the Gibraltar mine. The most abundant extractable metals, Al , Si, and Fe, were stored most in the silt-clay fraction. Generally, secondary weathering products from the waste rocks were largely due to the acid leaching regime at the location of each trench. Rock material from post-leach areas were characterized by very high levels of extractable Fe, indicative of conditions more conducive for the storage of these phases. In contrast, analysis from areas actively being leached or never leached have lower levels of extractable Fe, but high Cu levels. Metal distribution patterns seem to be largely related to pH, which is a function of the acidity from sulphuric acid additions, sulphide weathering, and active buffering in the system. Many metals, such as Zn, Mg, and Mo may not form discrete phases, but may be stored by a coprecipitation or solid-solution mechanism. The highly charged sulphate waters flowing through the rock dump are conducive to the formation of several phases. Crystalline gypsum was observed throughout these samples but the Fe phases tend to be poorly crystalline. Evidence suggests the presence of amorphous aluminosilicates. Finely divided phases are often very chemically reactive, and may be important in terms of sorption of some transition metals and anions such as sulphate and molybdate. The presence of certain cations or anions in solution may inhibit the formation of crystalline phases, but these phases may become more crystalline with age. 123 Ch.5-Distribution and Characterizaton Regions of greater weathering product accumulation can be identified using colour. The correlation between Hurst colour rating and extractable Fe produced several significant regression equations. Sample colour is generally controlled by the abundance and type of oxidized Fe phases. Red or low HcrSiCi zones tend to have higher levels of Mo, Al , and Fe, while non-red or high Hcrs;ci zones have higher levels of Cu. Thus, morphologically identifiable zones may be useful field indicators for the accumulation of certain metals. 124 Ch.6-Partitioning of Elements... 6. Partitioning of Elements in Secondary Weathering Products 6.1 Introduction Secondary weathering products stored in waste rock dumps are metastable as suggested by the different amounts of A A O and CBD extractable metals. Selective dissolution and total analysis of the Gibraltar waste rock samples indicate metal redistribution has occurred in the rock dump, leading to morphologically distinct areas of enrichment. It is important to measure the distribution of metals according to the affinity and strength with which they are bound to the matrix (waste rock). In order to assess the potential contribution stored secondary products may have on seepage from waste rock, it is necessary to know the chemical form (i.e. speciation) of the metals and their geochemical stability in order to understand their behavior and capacity for mobilization. Sequential extraction procedures are commonly used to measure metal distribution, mobility, and availability in soils, sediments, and mine tailings (Hickey and Kittrick, 1984; Filipek et al, 1981; Ramos et al, 1994 Tessier et al, 1979; Ribet et al, 1995). The technique utilizes several extractants, which successively remove more resistant phases by increasing the reactivity of the reagents used in the dissolution process. Sequential extraction techniques do not rigidly discriminate between metal species in the various phases but rather provide operational definitions of the different pools of metals. However, they do yield a general indication of metal solubility from a pool, and provide a reproducible system of analysis. There is no standard extraction procedure, thus when selecting an extraction technique considerations include the chemical and physical factors influencing metal 125 Ch.6-Partitioning of Elements... partitioning at a site, the choice of reagents, the extraction sequence, contact time with the material, and the solid/extractant ratio. Chao (1984) describes some of the basic requirements when selecting a technique. Commonly, metals in soils and sediments are operationally considered to be present in several forms and selective extractants are selected to target that form or fraction of the metal, accordingly. The different metal fractions are often identified as water-soluble, exchangeable, organically bound, bound with carbonates, associated with Fe and Mn oxides, and in the residues (Keller and Vedy, 1994; Hickey and Kittrick, 1984; Tessier et al, 1979). In Chapter 4, results indicate there is little or no carbon and calcite was not identified by XRD, thus metals bound to the organic and carbonate fractions were not investigated. Additionally, metal partitioning in the Fe oxides is likely to be more important than Mn oxides based on the abundance of secondary Fe, thus retention of metals by Mn oxides is not addressed in this procedure. Water-soluble forms are the first portion to be brought into solution in any extraction scheme. Typically, this portion is considered to be minimal or negligible in amount in materials near the earth surface in non-arid regions, but can not be ignored in areas of strong mineralization or where evaporites may form. Researchers have isolated the water-soluble phases using distilled or deionized water using contact times ranging from 2 minutes to 8 days with solid(g)/extractant(ml) ratios from 1:2 to 1:1000 (Lin, 1996; Bayless and Olyphant, 1993; Blowes and Jambor, 1990; Gatehouse etal, 1977). Exchangeable forms are metals and anions which are held through specific and non-126 Ch.6-Partitioning of Elements... specific adsorption. Many researchers have used a neutral salt to displace adsorbed metals, cations, and sulphate (IM MgCl 2 ; 0.05M CaCl 2 ; Na- or NHU-acetate; 0.01 NaN0 3; 0.1M LiCl; 0.1 M HC1) (Tessier et al, 1979; Ramos et al, 1994; Qiang et al, 1994; Tabatabai, 1982; Shuman, 1979). The efficiency of the metal extraction depends on the pH and ionic strength of the solution. Exchangeable metals only make up a small proportion of the total amount of metals in soils and sediments (Chao, 1983). The partitioning of secondary Fe forms is divided into the amorphous and crystalline or reducible fractions. Typically, there are three methods used for this procedure, (1) hydroxylamine hydrochloride solutions for both amorphous (Chao and Zhou, 1983) and crystalline (Ribet et al, 1995) forms, (2) A A O solutions for amorphous (Schwertmann, 1973), and (3) the CBD extraction for crystalline or reducible Fe forms (Mehra and Jackson, 1960). These methods have been used in mining studies (Herbert, 1997; Bigham et al, 1996), and ratios of A A O - to CBD-extractable Fe have been used extensively to assess the relative crystallinity of secondary Fe oxides produced in surface weathering environments, including mine drainage (Karathanasis and Thompson, 1995; Schwertmann, 1994; Murad, 1994; Bigham etal, 1990). The residual fraction consists of all remaining minerals not solubilized by the previous extraction steps. Researchers have used a variety of aggressive solutions for this purpose (concentrated H N O 3 ; aqua regia) (Herbert, 1997; Ramos et al, 1994). This fraction can also be calculated from difference if total elemental analyses has been performed on the untreated samples. 127 Ch.6-Partitioning of Elements... Use of sequential extraction procedures have been subject to several criticisms, including: the assumption that metals isolated using inorganic reagents are representative of those released by naturally occurring processes, lack of adequate testing of each extraction step, and inadequate testing with standardized material to show selectivity (Nirel and Morel, 1990). In recognizing these problems, it must be emphasized that all extraction techniques are operationally defined and metals isolated only approximate the metal pools in the matrix . Equilibrium geochemical modeling programs have been used recently to examine the saturation indices of water solutions in contact with unknown minerals (Lin, 1996;Schwab, 1995; Reddy and Gloss, 1993). A saturation index (SI) for a mineral phase is the log of the ion-activity product less the log of the equilibrium solubility product (Ksp) for the mineral phase in question. SI values can not be used to prove the presence or absence of specific phases, but can be used to assess the potential for a mineral phase to be present. Geochemical models have been used to examine mine drainage in streams and wetlands (Karathanasis and Thompson, 1995; Winland et ah, 1991), pore water chemistry from mine tailings (Al et ah, 1994; Blowes and Jambor, 1990), and minesoil solutions (Monterroso et al., 1994). The implicit assumption is that minerals present will be at chemical equilibrium. The aim of this study is to characterize the partitioning of stored secondary weathering products in acid- and non-acid leached waste rock samples from three different weathering regimes in one rock dump. Relationships are examined between colour and metal analyses from different extractable fractions, and mineral solubility controls for various metals. 128 Ch.6-Partitioning of Elements... 6.2 Methods Sampling site and rationale have been described in detail in Chapter 3 and 4. In summary, morphologically biased waste rock samples were collected from four excavated trenches defined by three different weathering regimes. The silt-clay (< 0.05 mm) fraction was isolated from each sample by sieving and subjected to the sequential extraction procedure. Duplicate samples were prepared for 14 of 29 samples examined. Five samples could not be tested due to lack of material. For comparison of mine waste samples to known mineral assemblages two groups of composite reference materials were made up to get an indication of how the sequential extraction scheme would affect the minerals and to get an indication of reproducibility from each experiment. One mineral reference set was made up of primary minerals (MRi and MR2) and the other was made up of minerals (primary and synthesized) common to mine waste (ERi, ER2, ER3). Mineral reference 1 (MRi) was composed of equal mass quantities of epidote, andesine plagioclase, albite, chlorite, muscovite, pyrite and quartz. Mineral reference 2 (MR 2) has the same composition as MRi , with the addition of chalcopyrite. The minerals in the mineral references were all crushed (in a titanium grinder) and sieved to isolate the < 53 pm fraction. Composition of the mineral reference is similar to the mineral assemblage in the rock samples taken from the Gibraltar rock dump. Although calcite is an important mineral in mine waste systems, it was not detected in XRD scans and may have been consumed by acid weathering. Mineral references ERi ER 2 , and ER3 were composed of: ERi - gypsum, limonite, quartz; E R 2 -. Fe 2(S04)3»xH 20, hematite, quartz; and E R 3 -129 Ch.6-Partitioning of Elements... synthetic K-jarosite and quartz. Synthetic K-jarosite was prepared using the method of Dutrizac and Kaiman (1976). Reagent grade hydrated ferric sulphate FeatSO^'xrl^O was used. All minerals, except for Fe2(S04)3»xH20 and jarosite, were obtained from either Wards Scientific or the UBC Geology Museum. A sequential extraction scheme was devised with the aim of isolating the metals from the soluble and the metastable pools. The soluble pool includes the water-soluble and exchangeable metals, while the metastable pool includes acid-soluble phases (including secondary Fe phases) (Figure 6.1). The sequential extraction scheme consists of five chemical extraction steps to remove, (1) water-soluble, (2) exchangeable, (3) HCl-soluble forms, (4) amorphous Fe, and (5) crystalline or reducible Fe (Table 6.1). Each extraction step shows decreasing selectivity or increasing harshness. The assignment of the various steps were explained in the introduction, except for step 3 - the HCl-soluble extraction. During method development, larger gypsum crystals (1 - 1.5mm length) were not completely solubilized in the initial two steps of the extraction. Crystals of gypsum were quite slow to dissolve and remained clearly visible to the eye even after 2 weeks of contact with water (1:50), suggesting a third pre-treatment was necessary prior to secondary Fe phase fractionation. Gypsum removal in samples was investigated by adding solutions of HC1 with concentrations ranging from 0.1 to 0.5 M for 30 minutes. Confirmation of the gypsum removal was examined in the residue using XRD. Longer times and concentrations were not investigated in order to minimize attack to the remaining primary and secondary minerals. 130 Ch.6-Partitioning of Elements... 131 Ch.6-Partitioning of Elements. T3 I X ) o u w X w X X o- X X o 00 X X X a N X X X X X o X X X X 3 u X X X X X z X X X X X X X X X ca U X X X X OB X X X X X c X X X X X < X X X X X 00 X X X X X <D X X X X X IS 00 c -fi oo c o ca & t a. on C ca OO loo M l H H H Pi Pi! OH X X X u fe o V B * x ;g 00 o o o a 00 ( N < N ^ ] - H o in o o N M CO Tt u EC V - CN * , * u o co +1 C N OJ 03 VH <D ex 0 D -J—* 6 o o <D 6 - B B T3 a -S o £ 00 S 03 ID T3 (D T3 03 1) B o c o a* s s 03 3 CT 03 <D <= £ O 03 a 2 is3 O T 3 2 U c -4—> o 03 a X 0) s <D 3 CT <D 1 3 fi 03 .e T3 <D B 1) 4) o3 J3 C M VO o CT i-J 1) "3 o o + CN oo .fi u vd II oo -9 T3 03 <D 03 s s 1 ' " H 03 3 fi B o a 03 B •3 t o o T3 B 03 1? <D 3 c x 00 03 > o I o o o <D u '3 C T ID l-i U X m o 132 Ch.6-Partitioning of Elements... Gypsum removal was near complete using the 0.5M HC1 solution, which was then included to the sequential extraction scheme. Details of the method and analyses performed are given in Table 6.1. Extraction vessels used were pre-weighed 250 ml acid washed, high density polypropylene centrifuge bottles with caps. Bottles were re-weighed after the sample was added. Samples and mineral references were subjected to 5-step sequential extraction scheme. Mineral references were treated like samples. Step 1: deionized H2O 30 minutes; 1:20 sample solution removal of water soluble salts (secondary minerals) and easily exchangeable cations and anions Step 2: 1 M LiCl 30 minutes; 1:25 sample:solution removal of adsorbed metals and anions Step 3: 0.5 M HC1 30 minutes; 1:30 sample:solution complete removal of gypsum and slightly soluble phases Step 4: A A O 4 4 hrs in the dark; pH 3; 1:40 sample:solution poorly crystalline Fe and aluminosilicate phases and associated metals Step 5: C B D 1 18 minutes (with 3 additions of dithionite); pH 7.3; 1:22 sample solution free and crystalline Fe phases and associated metals The final 3 steps utilize acids in the extraction. AAO - acid ammonium oxalate , CBD - citrate-bicarbonate-dithionite 133 Ch.6-Partitioning of Elements... For steps 1 to 4, samples were shaken on a flat bed shaker at 22°C. For step 5, samples were stirred during the extraction period (Lavkulich, 1982). After each extraction, solids were settled by centrifugation (lOOOOg) and a 100 ml aliquot removed by pipetting. Disturbance to the solids was minimized by starting with a 10 g sample (e.g. 1:20 sample solution yields 200 ml of solution for step 1). A u-shaped glass siphon was used to remove the remaining solution. Solid residues were washed twice with ethanol then dried at 40°C until constant weight was achieved (usually 36 hrs). Extraction vessels were re-weighed to determine loss-on-extraction and a sub-sample removed for XRD analyses. Aliquots were analyzed for SO42", pH, Eh, and E C on the same day. Metals analyzed the following day were Al , Ca (except for A A O step, Ca-oxalate is insoluble), Cu, Fe, K, Mg, Mn, Mo (except for LiCl step, due to chemical interference), Na (except for LiCl and CBD steps, due to chemical interference), Si, and Zn. All metals were measured by atomic absorption spectrometry using a Perkin Elmer AAS model 306 instrument with either air-acetylene or nitrous oxide-acetylene flame. Sulphate was determined by turbidimetry using a spectrometer (Rhoades, 1982). Standards were prepared for each extraction step using similar matrices to minimize chemical interference. Non-parametric statistical methods were used to analyze the data. The Mann-Whitney U-test was used to compare two groups of data. When there were more than two groups of data, the Kruskal-Wallis test was applied, and if necessary, a non-parametric analogue of Tukey's test (Zar, 1984 p200) was used for multiple comparisons. Correlation among different properties and metals was determined by the Spearman rank correlation 134 Ch.6-Partitioning of Elements... coefficient. The level of significance for all testing was P <0.05 unless otherwise specified. Data from deionized water extracts were entered into MINTEQA2 to calculate activities and saturation indices (SI) in order to examine thermodynamic mineral solubility, and examine possible changes in composition as conditions change. Saturation index (SI) value for various solids was calculated by MINTEQA2 using the equation: SI = log (IAP)/Ksp) where IAP is the ion activity product observed in solution, and K s p is the theoretical solubility. Positive SI values indicate that a solution is oversaturated or supersaturated with respect to a given solid phase, while a negative SI value indicates unsaturation. A condition of oversaturation or supersaturation indicates that precipitation of the respective mineral phase is thermodynamically possible. When SI equals 0, the solution and the solid phase under consideration are in apparent equilibrium. Solutions unsaturated with respect to a given solid phase suggest that phase can dissolve as a reactant. In this study, apparent equilibrium is defined as when the SI value for a solid phase is between -1.0 and +1.0, thus allowing for the inherent uncertainties in the analytical and thermodynamic data. Geochemical calculations performed using computer codes do not prove the presence or absence of a phase, but provide an indication of the tendency for a reaction to occur. Other analytical data used in the program were pH, Eh, and ionic strength (IS). Electrical conductivity was converted to IS according to the following criteria and relationships (Alva et al., 1991): E C < 1. mS«cm"': IS (mM) = 0.012 E C (mS-cm1) - 0.0002 135 Ch.6-Partitioning of Elements... E C > 1 mS-cni 1: IS (mM) = 0.012 E C (mS^cm1) - 0.0006 6.3 Results and Discussion The complete data for the sequential extraction analyses for the samples and the mineral references are reported in the Appendix. The sequential extraction scheme was aimed at removing phases with greater solubility in the first two steps, and lower solubility in the latter steps. Analysis of sample duplicates were generally within 10% level of precision, but tended to increase above this level as analyses approached minimum detection limits and the upper linear range of the instrumentation. Increasing dilution lead to increased variability due to errors introduced by mixing and pipetting. composite reference materials Figure 6.2 and the accompanying L O E 5 data set indicate that the extractable proportion of the mineral references varies according to its mineral composition. The minerals comprising MRi and MR2 were extracted mainly by the more "aggressive" extracting solutions (HC1, A A O , and CBD). Total gravimetric loss from the sequential extraction was much less for MRi and M R 2 than ERi, ER 2 , and ER 3 . L O E data and chemical analyses from the mineral reference elutriates have acceptable reproducibility to demonstrate trends. 5 LOE = gravimetric loss due to extraction 136 Ch.6-Partitioning of Elements.. MR 1 MR 2 ER 1 ER 2 ER 3 - -— — — ^ n m ; , •...,.: I wmmasm - -wmBmmmmwmwmmmmmwmmm i nmtsm - -it 11 i n mm mm , , 1 1 1 0% 20% 40% 60% 80% Proportion of LOE from each step relative to the total LOE. 100% Loss-on-extraction relative to the intial sample mass H 20 LiCI HCI AAO CBD TOTAL% MR 1 0.6 0.4 3.4 1.5 0.5 5.8 MR 2 0.8 0.2 5.6 1.3 1.1 8.2 ER 1 5.0 16.2 11.7 0.4 17.5 50.7 ER 2 33.3 0.6 1.1 0.7 1.4 36.9 ER 3 0.3 1.3 5.2 14.2 31.7 51.9 MR 1 = albite, andesine plagioclase, chlorite, epidote, muscovite, pyrite, quartz MR 2 = MR 1 + chalcopyrite ER 1 = gypsum, limonite, quartz ER 2 = Fe2(S04)3»xH20, hematite, quartz ER 3 = K-jarosite, quartz Figure 6.2 Mass % extracted or loss-on-extraction (LOE) for mineral references from sequential extraction. 137 Ch.6-Partitioning of Elements... Variations in the analyses appear to be random (experimental) between extraction batches and analyzed metals. The mass loss of composite reference materials was quite varied as would be expected with from their mineral composition. MRI and MR2 experienced significant loss of mass during the HC1 extraction step, but little during the initial steps. Literature indicates primary minerals are attacked minimally by A A O and CBD solutions (Jackson et al, 1986), which would seem to support the results from the sequential extraction. Chemical results suggest the sulphide minerals, chlorite, and muscovite are attacked the most, as indicated by the quantities of S042"-S, Fe, Al , Si, K, Mg, Na, and Zn. Mass loss from ERI, ER2, and ER3, is due mostly to the dissolution of gypsum and limonite, hydrous ferric sulphate and hematite, and K-jarosite, respectively. Of the minerals typically identified as precipitated weathering products in mine waste, the mineral solubility sequence from this extraction scheme could be gypsum and hydrous ferric sulphate, followed by K-jarosite, then limonite and hematite. The dissolution behavior of the oxidized Fe phases, agrees with the literature (see Chapter 5; Bigham et al, 1996; Borggaard, 1988; Schwertmann et al, 1982). The data (Figure 6.2) suggests that pulverized primary minerals with no secondary weathering products present, are susceptible to dissolution. This apparent solubility may be due to sample grinding which forms fine particles of high surface area and high reactivity. general characterization of samples Extraction solution quality (EC, Eh, pH) was collected for H 2 0 and LiCl extractions. 138 Ch.6-Partitioning of Elements... The E C results from all samples were relatively high in the H2O solutions likely due to the dissolution of very soluble mineral phases, and ranged from 580 - 2400 umhos/cm. E C values were lowest at the surface. The ionic strength of the LiCl solution masks any changes associated with mineral dissolution. Eh values in the H2O solution ranged from 270 - 523 mV, and in the LiCl solutions ranged from 160-462 mV. pH values taken from the H2O solutions ranged from 2.7 - 6.2, and from the LiCl solutions ranged from 2.8 - 6.5. Solution pH is similar to those determined in the previous chapters. Solution quality between H 2 0 and LiCl solution for all samples was similar. Data from each trench and for each extraction step are summarized in Table 6.2. The data suggests Ca, Mg and SO4 " were mostly extracted using the non-acid solutions; Al and Cu phases were extracted using both the non-acid and acid solutions; Fe, K and Si were dominantly extracted using the acid solutions. The average SO42" content in the samples ranges from 3 - 7% (mg/kg), with decreasing order A (7 %) = B (7 %) >C (4 %) >D (3 %). These values are high compared to typical values reported in literature (0.6%; Choquette et al., 1994), but are within the upper range of values reported (1.5% - 9.7%) in pyritic waste material from coal mining (Renton et ah, 1988; Colbourn, 1980). The sulphate concentrations produced in the extraction solutions (20 - 4,000 mg SO4TL) are similar to those found in acid sulfate waters and laboratory tests (Ghomshei et al., 1997; Yanful et al., 1997) and in the lower range detected for dump 1 seepage (D. Mathias, personal communication). The high SO42" content in trenches A, B, and C likely originate from sulphuric acid additions for the dump leaching process. 139 Ch.6-Partitioning of Elements. u e u CJ o u . S _o u S3 S3 C O "5 « S . * ^ X CJ a S a-E o •fa OJ T 3 "M o S OJ a> <N vo 3 CS O oo PH u cd u c 1) X PJ o o o o m in H >t oo vo vo co r- r - -H o C N C N C N C N Tf VO in VO - a 73 Tf -a C C —i c o ° ° ° 2 £ • a - a T I o o o C N o o o o 00 CO VO O -H ro co CN _i O O C O C N O O ^ . O N O N oo ^ —i O O O 2 O Ov oo J~! CN CN VO £j O O Tf Tf — , C N o o o o o 0 m r- oo §> as -H Tt g co t in ^ co co -H <^> —i CN CO CN 73 -H in C C O CN A d i Q d c c c c cd C3 c c c c CN CO VD CO -H —I I/") rO O O OS OS CN — i Tt m C N in r~- vo -—i — i •n in in a\ o o r- — i co Tf o o o o co co in c\ Tf O OS o o co -H m C N o in o ^ o m co ° o oo —I m I/-) -H CN VO O CO CN - H CN CN 73 TS TS C C C VO in ov VO —I ov o co C N C N in Tf o o o o Tf C O as oo ON VI M h 00 -H C N C N O 00 CN — i CN CN 00 CN O C N C N o O O O o O ro CN o O O Os CO CN OS r- VO 00 oo CO OO ON 00 —H —< CN Tf ro CN CN VD VD — 1 o o o in C N o o o g vo S co —i ~_, ca a c c 73 c cd cd c c o o o o CN VO VO Tf in Tf _H o H^ C O ^ -H t— oo oo 73 CN Tf —I C oo —i r -vo —i as C N in f- ro oo CN ro -H -H o o o o S m ( N S 00 OO VD ~ vo Tf m vo co in Tf as co o o C O C O cd cd C C o o o o O O O vo co as Tf U u in o O < 73 73 73 73 C C C C 73 73 C C o o o o t— in t— C N vo in -H oo 73 73 73 73 C C C C 73 73 73 73 C C C C "C oo in t— vo Tf —I Tf —I 73 £j r- 73 c PJ C N c S o o o RS vo m co ll as as o ^ OS Tf 0O 73 73 73 73 C C C C 73 73 73 73 C C C C 73 —< vo 3 c o\ h ° < fP o Q < P H U Q < m u Q < m u Q < M U Q Q pa u 140 Ch.6-Partitioning of Elements... The high extractable sulphate levels in trench D are likely attributable to the infrequent leaching and proximity to the dump surface which allows sulphate produced from sulphide to be retained as a salt in an efflorescence. Gypsum is known to be present over a wide range of pH values in acid sulphate soils, (van Breeman, 1973a), which suggests it could be a sink for Ca and SO42". Other potential sinks for sulphate are sorption and occlusion in precipitated phases. Based on the different proportions of metals removed, the increasing harshness of each extraction step removes different secondary weathering products. The first two steps remove > 50% of the extractable S (as S042"), Ca , Mg, Mn , and Na in several of the samples. Total sequential extractable (sum for all fractions) metals decreased in the order: Fe » S > Ca > Si >A1 > Mg > Mn > Cu > K > Na > Zn. If one calculates the ratio of total sequential extracted to total (XRF) metal (Table 6.3) the sequence is: S > Cu > Mn > Fe > Ca > Zn > Mg > Na > Si > Al > K. These results suggest most of the sulphur in trench A, B, and C occurs as SO42" and the apparent lack of residual Cu-sulphide. This seems to be different than what has been suggested others (Klohn Leonoff Consulting Engineers, 1991) and will be addressed later in this chapter with the discussion on sulphate. Mo was not placed on either list because the level of Mo was below detection limits for many samples. High correlation coefficient values for total extractable Fe, Ca, and SO42" to mass loss indicate these metals were important components in the removed phases (Fe, rs = +0.68; Ca, rs = +0.89; S as S042", r s = +0.97). Solution p H s i d is significantly correlated (P < 0.001) to total extractable (sum of all fractions) Cu (rs = +0.76), Fe (rs = -0.64), and Mn (+0.71). 141 Ch.6-Partitioning of Elements... 1 13 •a o s s © so H n in h ^ o M ^ ^ M a oo m "* ^ w - ) " o m r - r - . i o ^ T t i r i o CN oo t-; « r t r l o \ i O i f 1 i T i ' t \ o C\ in m o •^•-Hmm^o^rfN<Mm cn CN oo \o CN o ' o o o o ' o — ' o o o o ' o o o ' o o i n ' o o ' ^ o o o o d d H K m o o o o ' o o o o o p r-- Tt —; oo r) CN \q ^ iri Tt d ri -cj H ri ff| Tf IN pj r-- —< in ^- —< r- g - . oo <n t 2 ^ r- Tt O r ^ o C p O C l r ^ r - r - i a ' ; M iri rt rn pi ri rf 1 o<nr--r>r>mrt-H\o d o o d o ' f N ^ - ^ - i <<<<<<<<< o co in o ri a\ f>i ro r o o i i N r i H - i o d o so ^ ^ m m m m m u u u u o u u u u -H i> C; ri ro CN' d d d c4 CN tN —' d H o —> <n so r-cn in as co r— CN r-i -< rn -H m r- r- rj\ fj\ »n Oi — k o o d o o C Q Q Q G C <N C\ ON SO SO cn « © © © © © 142 Ch.6-Partitioning of Elements... Figure 6.3 shows the mass balance associated with each extraction step. Samples showed significant loss of mass on extraction (LOE or loss-on-extraction) with water and HC1 solutions. Generally, the water and HC1 extractions resulted in up to 50% of the mass L O E in most samples. Some samples have sizable L O E U c i values but this is likely due to incomplete dissolution of H 2 0 soluble phase and not from adsorbed metals. LOEuci and LOEH2o are probably associated with two similar fractions since adsorbed metals are not likely to provide a significant mass. Thus, dissolution results for H 2 0 and LiCl extractions; are due to the dissolution of salts (ionic species) and the displacement of sorbed metals. The largest L O E A A O and LOE H c i are found in samples from trench C and trench D, respectively. Samples from the trenches, except trench C, experienced L O E C B D - Only three samples taken from trench C had measurable L O E C B D , suggesting most of the secondary Fe is in amorphous form. During active acid leaching (i.e. in trench C), secondary weathering products undergo (partial or complete) acid dissolution or their formation is inhibited, resulting in small amounts of adsorbed metals and reducible Fe oxides. extractable metals In discussing the results from the sequential extractions, metals are organized into four groups: (1) Fe, Al , Si (oxides, hydroxides, and oxyhydroxides) (2) Na, K, Mg, Ca (alkali and alkaline earth metals), (3) Mn, Cu, Zn (transition metals other than Fe), and (4) molybdenum and S in the form of sulphate. 143 Ch.6-Partitioning of Elements.. Ch.6-Partitioning of Elements... Results for Al , Fe, Cu, and SO42" are summarized in Figure 6.4. In general, Cu and SO42" were most susceptible to the extraction procedure, results suggesting they were present in soluble and metastable forms solubilized by the sequential procedure. The metals least soluble were Al , Si, K, Mn, and Na suggesting they were dominantly present in primary minerals or secondary phases not susceptible to the procedure. The intermediate solubility of the other metals (Ca, Fe, K, Mg, and Mo) suggests they were present in a mixture of soluble, metastable, and primary phases. There is no apparent relationship between metal distribution from the extraction procedure with depth (graphs located in Appendix). Extractable metals significantly correlated (P < 0.001) with solution pHSiCi are summarized in Table 6.4. The results reflect the differential dissolution of secondary minerals and removal of adsorbed ions. Figure 6.5 shows the results from multiple comparison analyses of extractable metals between trenches using a non-parametric Tukey-like test (Zar - p200, 1984), in order to determine the effect of the different locations and leaching regime of each trench location for the analyzed metals. Although there are differences in the distribution of the extractable metals in each trench, there are no consistent patterns. Several factors leading to different metal distributions in each trench are the effect of differential acid leaching, differences in past and present pH, changes in moisture holding capacity, presence of preferred pathways and hydrologically connected profiles, and the location in relation to the dump crest. 145 Ch.6-Partitioning of Elements.. ~ m ,^ <J a m m c ° o c ° O f i s s s is fi is I £ J8 2 2 2 2 2 2 2 2 2 8 8 (B/6m) uonejiusouoo no (6/6LU) uoije4U80uoo tos sst § s E s j " i 2 2 2 2 2 2 2 2 2 s S i 2 2 2 g 8 8 8 8 9 8 (6/6UJ) uojiBjjueouoo iv fe. I (O 15 c c o <P o 2 X cu . E o CO o E s c o v« 2 >•-» c o o c o o o T5 c CO of LL. 3" O c co CD E TJ C ro E E 'c E E 3 E X S 8 (B/6LU) uogejjusouoo CO 3 146 Ch.6-Partitioning of Elements. Table 6.4 Summary of significant correlations for solution pFJicl with metals from the sequential extraction scheme. Sequential Extraction Spearman rank Step Metal correlation coefficient H20 Al -0.84 Ca -0.6 Fe -0.91 K 0.84 LiCI Cu 0.64 Fe -0.82 Mg 0.87 Mn 0.76 HCI Al 0.77 Cu 0.82 K 0.72 Mg 0.86 Mn 0.85 AAO Cu 0.78 K -0.69 Mg 0.64 Na -0.82 CBD Fe -0.76 147 Ch.6-Partitioning of Elements... 148 Ch.6-Partitioning of Elements... Differential leaching rates can result from differences between the acid leaching process, or compaction and particle size variations in the dump leading to zones will lower conductivity and others which are connected hydrologically. Areas near the crest of the dump may be susceptible to gas exchange and thus higher oxidation rates. Another factor to consider is the exposure period of the material to atmospheric conditions prior to burial, but records for this type of data were not available. Trench A and B should be the least different because both have been treated similarly with respect to acid leaching. Surprisingly, metal distributions in trench C and D are statistically quite similar. Total mass of the extractable metals is quite similar in trench C and D. If the average concentration of extractable metals is calculated for each trench (i.e. for each sample, S as SO42" (H 20, LiCl , HC1, A A O , CBD) + Fe (Ff20, LiCl, HC1, A A O , CBD) + the same for all the remaining metals analyzed, then averaged for all samples from the trench), the results would be: A = 77000 , B = 61000, C = 46000, D = 49000. Based on the metals analyzed, trench C and D have similar masses of total extractable weathering products and less total extractable mass than trench A and B. These results indicate that rocks from trench C and D tended to retain lower quantities of metals compared to trench A and B. In trench C, the combination of high leaching flow rates and the low pH of the sulphuric acid leads to the dissolution of metastable weathering products. In trench D, natural weathering processes not accelerated by acid leaching likely to the slower onset of sulphide oxidation, thus weathering was not as advanced as in post leach areas. The pH is lower in trench A and B is the result of a greater accumulation of acidic weathering products. This result suggest the leaching 149 Ch.6-Partitioning of Elements... initiates and accelerates weathering faster than natural weathering, but the high flow rates continually remove secondary weathering products. When leaching is stopped, weathering products begin to accumulate in excess of natural weathering and under leaching conditions. Several metals (Cu, K, Mg, Mn) in the LiCl fraction are positively correlated to solution pH. This may be explained by the pH dependent C E C of sesquioxides (variable charge phases) such as Fe and Al oxides, hydroxides, and oxyhydroxides. The sorptive capacity of sesquioxides for cations increases with pH, thus at higher solution pH, greater quantities of cations are sorbed and can be displaced by the L i + cation. Fe, A l , Si Most of the total extractable Fe, Al , and Si is associated with the HC1, A A O , and CBD extractions (Figure 6.4). In relative terms, the amount of H 2 0 and LiCl extractable Si and Fe is small. In trench A and B, there are significant quantities of A1H20 and Aluci- There is very little CBD extractable Al. Extractable Si is dominantly SicBD 6- No relationship is apparent between any particular pool of metals with depth. Jackson et al. (1986) state CBD has much more effective at solubilizing Si than A A O . The following pairs of metals were strongly correlated (P < 0.001): A1H20 and FeH2o> Al H ci and SiHci, A1 AAO and SIAAO, and FeAAo and SIAAO- Levels of FeH2o and AlH2o decreased to levels near detection limits in samples with pH < 3.5 and pH < 4.4, respectively. Extracted Fe from H 2 0 , LiCl , and CBD solutions were negatively correlated (P < 0.001) to solution pH. A1H20 and Al H ci are also SiCBD and data for other elements written in this format are read as " CBD extractable Si". 150 Ch.6-Partitioning of Elements... correlated (P > 0.001) to solution pH. These results suggest that there are small quantities of soluble secondary Al and Fe minerals, however, extractable Fe and Al phases have low solubility (e.g. jarosite and Al(OH)3) and are likely accumulate at lower pH. Additionally, under typical earth surface conditions, Al and Fe solubility tends to increase with decreasing pH, but in the presence of abundant SO42", several metastable phases are known to form. For example, Bigham et al. (1992) found that jarosite was only present in mine drainage streams with sufficient SO4 " and pH values around 2.6 - 3.3. Dissolution of H 2 0 soluble Fe- and Al -salts such as coquimbite Fe2(S04)3»9H20, which is a common oxidation product of pyrite in oxidizing environments (Alpers et al., 1994), and alunogen Al2(S04)3»17H20, could contribute and control concentrations of Fe and Al in H2O extractions. The correlation between A1AAO and Si A A o suggests the presence of an amorphous aluminosilicate phase. Fhgh concentrations of Al in waters affected by mining have been attributed to the dissolution pH-buffering reactions associated with aluminosilicate or aluminum hydroxide minerals in the drainage (Blowes and Jambor, 1990; Nordstrom and Ball, 1986; van Breeman, 1973b). Ca, Mg, K, Na The alkali and alkali earth metals tend to form soluble salts of carbonate and sulphate under typical surface conditions, but this may not be the case in acid impacted mine rock. There is little similarity in the distribution of the total amount extracted from the sequential extraction for these four metals. There are also differences in their distribution in the four 151 Ch.6-Partitioning of Elements... trenches. Ca is largely extracted in FE-O and LiCI solutions. Only a small proportion of extractable Ca is Canci and no CacBD- CaAAo can not be determined due to the formation of insoluble Ca-oxalate during the extraction procedure. CaH2o is negatively correlated with solution pH (rs = -0.60). The correlation between CaH20 with S042"H20 (rs = +0.94) and Canci with S0 4 2"LJCI (rs = +0.81) can be explained by the dissolution of gypsum, which was observed in these samples under the microscope. A rationalization for these results could be as follows: sulphide oxidation and acid leaching led to decreased pH and increased acid dissolution of Ca containing primary minerals (such as plagioclase and epidote) which resulted in increased SO42" and C a 2 + concentrations promoting the precipitation of CaS04 phases such as gypsum. No trends were observed in any of the trenches with depth. Extractable Mg is dominantly MgH20 and Mguci, with small quantities of MgHci> MgAAO, and MgcBD- Solution pH is correlated (P < 0.001) with Mguci, MgHci, and MgAAo-Most of the extractable Mg is likely present as a soluble form (e.g. MgS04*nH20). The small fractions of Mgnci and MgAAO may be from the dissolution of a brucite layer from ferromagnesium chlorite. No trends were observed in any of the trenches with depth. Generally, the extractable K pool is associated with the latter stages of the extraction sequence (HCI, A A O , CBD). In trench B, extractable K is dominantly in the K C B D pool and in trench A in the K H ci and K A A O fractions with relatively low levels of KH2o and Kyci-Extractable K is positively correlated ( P < 0.001) to solution pH in H 2 0 , LiCI and HCI extractions and negatively correlated with A A O data. These trends are consistent with results 152 Ch.6-Partitioning of Elements... for Fe which suggest the presence of an poorly soluble amorphous phase containing K, such as jarosite or alunite. This suggests that the conditions in the microenvironment were very extreme since jarosite (and alunite) tend to be associated with waters at low pH with high levels of Fe 3 + (and Al for alunite) and SO42" (Chapter 2). The lack of a correlation between K and Fe or Al in the A A O and CBD extracts could be due to the small amounts of these phases relative to other Fe and Al phases. Extractable Na, like K, shows unique behavior depending on the trench. NaLici and NacBD could not be determined due to chemical interference with the analytical technique. NaAAO is correlated to solution pH (rs = -0.82). Samples collected from trench A and B have much larger proportions of NaAAO than in trench C and D. Trench C has large proportions of NaH2o and NaHci • The natural weathering in trench D has resulted in the formation of many H2O soluble Na phases, but in trench C, there are more metal species present in the pore waters and, as indicated by the larger Nanci fraction, less soluble (greater meta-stability) phases form. In trench A and B, although acid leaching had ceased, the low pH from the reserve acidity of the system ensures continued acid decomposition of existing minerals. There is a greater potential for mineral rearrangement in post-leach areas because of the lack of continued leaching. Thus, there is more opportunity for Na to be occluded in a new phase or form a discrete phase with lower solubility as suggested by the presence of NaHci and NaAAO fractions. One possible phase is jarosite, which has been discussed with Fe and K. The Na containing form is natrojarosite. 153 Ch.6-Partitioning of Elements... M n , Cu, Zn These three metals are often included among the heavy metal group (e.g. Pb) of metals and tend to show similarities in terms of their chemical behavior and properties (Miller, 1984). For example, all have a coordination number value of 6. The amount of Mn extracted varies from 3.2 to 100% of the total (XRF) Mn (Table 6.3). Samples from trench C have a small amount of H 2 0 and LiCI extractable Mn, but this was not the case in the other trenches. Samples with a high proportion of Mn H 2 o + Mn L i C i were collected from the red pseudohorizon (i.e. HcrSjCi < 20) in trench A between the depth of 1.2 -2.0 m, all samples from trench B, and samples near the surface of trench D. This fraction consists of phases soluble in unbuffered aqueous solutions. Samples with a high proportion of metastable Mn (MnHci, MnAAO> MncBD) were located beneath the red zone in trench A and in most samples from trench C and trench D. A significant correlation (P < 0.001) was observed between Mn and several other metals: MnH 2 o with ZnH2o/MgH 2o, Mn L i C i with Cu/Fe/K/Mguci, Mn H ci with Al/Cu/K/Mg/Si/ZnHci, and Mn A AO with MgAAO- It appears mobilized Mn is distributed into soluble phases under post-leach conditions and into less soluble phases under conditions of acid leaching. This could be the result of the inclusion of Mn as a contaminant in a coprecipitation process in trench C, but as conditions dry and mineral phases age, occluded Mn is gradually excluded from the mineral structure. Mn may either coprecipitate with efflorescence minerals or form a discrete phase. Mn shares the same coordination number as Al , Cu, Fe, and Mg, suggesting Mn could proxy for these metals in a mineral. The presence of Mn H ci and Mn AAo may result from the dissolution of 154 Ch.6-Partitioning of Elements... Mn-containing primary minerals. Copper is found in significant quantities in the samples and sequential extraction fractions, except the CBD extractable fraction. Although no significant correlation coefficient is noted, Cu and Mn behave similarly with respect to the pattern of distribution by extraction. Cu is distributed mainly in the H 2 0 and the LiCl fractions in trench A and B, and in the HC1 and A A O fractions in trench C and D. Total extractable Cu in trench C and D is 10 - 20 X greater compared to trench A and B, and is approximately the same as total (XRF) Cu (Table 6.3). Extractable Cu is correlated (P < 0.001) to several metals: Cuuci with Fe/K/MnLici, CuHci with Al/K/Mg/Mn/Si/ZnHci, and CUAAO with K/NaAAo- These results suggest mobilized Cu is stored mainly as CUH2O and Cuuci, with relatively small quantities of CUHCI and CUAAO- In trench A and B where there is no leaching with acid, the CUH2O fraction accumulates, but in the other trenches, CUHCI dominates. Zn is extracted the least compared to the other metals, although relative to total (XRF) analysis, Zn is more extractable than Si, Al , K, Na, and Mg (Table 6.3). The distribution of Zn shows that in all samples, Zn H 2 o and Znyci make up a large proportion of the total extractable Zn. Only three samples contained ZncBD- Samples collected from the surface of trench B contained no ZnHci- Extractable Zn is significantly correlated (P < 0.001) to several parameters: ZnH20 with Mg/MnH20, Znyci with Mg/MnLici, Znnci with Al/Cu/Mg/Mn/SiHci-Zn has the same coordination number as Mg, Mn, and Cu. Some of these correlations may be spurious or may be due a common relationship with solution pH. Zn storage is likely attributable to the formation of soluble Zn phases such as Zn-sulphates, occlusion of Zn in 155 Ch.6-Partitioning of Elements... other phases, and adsorption of Zn on sesquioxides. Mo and SO42" Sequential extraction analysis detected molybdenum in only eight samples in trench A, B, and C. At the solution pH of these samples, solution species for Mo are likely to be M0O4 2 ", HMoCV, or H 2 M o 0 4 ° (Lindsay, 1 9 7 9 ) . Mo was detected only in HCI and A A O extracts. Mo could not be analyzed from the LiCI solution because of chemical interference with the matrix solution. One factor contributing to low Mo in these samples is that the Mo oxyanion competes with SO42" for sorption sites. Mo is correlated with several other metals: MOHCI with FeHci (rs = + 0 . 3 9 , P < 0 . 0 5 ) , MOAAO with Fe A A o (rs = + 0 . 4 3 , P < 0 . 0 5 ) ; MOAAO with M g ^ o (rs = - 0 . 3 7 , P < 0 . 0 5 ) . These trends may be due to adsorption of the molybdate oxyanion onto sesquioxide phases or occlusion in a secondary mineral. The former is likely to occur but could not be confirmed using the present sequential extraction scheme because displacement of Mo into solution would have occurred in the LiCI solution. Sulphate was analyzed in the first three steps of the extraction sequence and could not be determined in the A A O and CBD solutions. In all but one sample, the H20+LiCl extractable S asS042" makes up greater than 5 0 % of the extractable S (Figure 6 . 4 ) . The total extractable S as SO42" (H 2 0 to HCI only) to total S ratio is quite high and ranges from 0 . 7 -1.0 indicating that the S in these samples was present as secondary weathering products (Figure 6 . 6 ) . Correlation (P < 0 . 0 5 ) of S with Ca and Fe in the H 2 0 , LiCI, and HCI suggests the presence of Ca-sulphate and Fe-sulphate phases. 156 Ch.6-Partitioning of Elements... 157 Ch.6-Partitioning of Elements... In several cases, total extractable S as SO42" exceeds total-S. This is an artifact from the different analytical methods. Total extractable S as SO42" was calculated from the sum of three separate extractions and analyses, whereas total-S is from one analysis using a different technique. As indicated earlier, duplicates were generally within 10% level of precision. The results indicate that sulphate is the dominant sulphur phase and there is little or no remaining sulphide. This appears to contradict some results from a previous study (Klohn Leonoff Consulting Engineers, 1991). In this report, the authors reviewed data from several column leaching experiments (with sulphuric acid) and make the assumption that Cu extraction is derived from Cu-oxide phases first, and then from the oxidation of Cu-sulphide or FeS2-chalcopyrite. This assumption was based on the high rates of Cu extraction and acid consumption, and the virtual absence of Fe in the leaching liquors. There are several explanations to explain this apparent difference. • Under the acidic and high SO4 " conditions present in the columns, weathering products are likely to have precipitated and accumulated in the column (as noted in the 1991 report). The low solubility and meta-stability of Fe precipitates could lead to the accumulation of Fe on the rock samples, thus explaining the reported virtual absence of Fe. • The report indicates there was virtually no iron in the leach liquors, but based on the results present that was not the case (7-48 g of Fe extracted compared to 9-23 g of Cu from sulphide and 2-17 g of Cu from oxides). • The results from the column experiment may not be representative of the conditions 158 Ch.6-Partitioning of Elements... occurring in the rock dump, and could influence interpretation. The columns used were leached continuously for various periods of time (6 months to 21 months), but rocks in the dump are exposed to repeated cycles of wetting and drying. mineral equilibria An indication of the minerals controlling water concentrations of metals can be obtained using H 2 0 solution chemistry data. These data were input into the geochemical package MINTEQA2 to obtain saturation indices for various minerals and activity coefficients for analyzed metals. Solution quality data, Eh, pH, and IS (determined from electrical conductivity) obtained from the H2O extraction, were included in the model. The oxidation state for Mn and Cu was set as 2+ because these are the most stable oxidation states (Miller, 1984). The Fe 2 + /Fe 3 + redox couple was calculated from Eh readings. It is assumed that the extractions had achieved a quasi-equilibrium at the time solutions were separated from the solids. Mineral phases with saturation index values < 0 indicate the solution is unsaturated with respect to that mineral and it is susceptible to dissolution, if the mineral is present. On the other hand, mineral phases with saturation index values = 0 suggest the mineral may be controlling pore-water concentrations of component metals by precipitation and dissolution reactions. Saturation index calculations indicate that the H2O solutions range from slightly unsaturated to slightly oversaturated with respect to AIOHSO4, gypsum CaS04»2H20, 159 Ch.6-Partitioning of Elements... natrojarosite NaFe3(S04)2(OH)6„ maghemite Y-Fe2C»3, and alunite KAl3(S04)2(OH)6, suggesting that these minerals may be dissolving and contributing the levels of A l 3 + , Ca 2 + , Na + , Fe 3 + , SiCV, and SO42" in H2O extracts. Saturation index values from the H 2 0 solutions are slightly unsaturated with respect to langite Cu4(S04)(OH)6 ,2H 20, anhydrite CaS04, epsomite MgS04»7H20, chalcanthite CuS04,5H20, tenorite CuO, cupric hydroxide Cu(OH)2 , antlerite Cu 3 S0 4 (OH) 4 , brochantite Cu 4(S0 4)(OH) 6, diaspore AIO(OH), gibbsite Al(OH) 3, and ferrihydrite 5Fe203»9H20. Saturation index values from the H2O solutions are slightly unsaturated or at equilibrium with respect to lepidocrocite Y-FeO(OH) and goethite cc-FeO(OH), unsaturated with respect to other ferric iron minerals (cupric ferrite oc-CuFe204 and K- and H30-jarosites XFe3(S04)2(OH)6), and supersaturated with respect to hematite cc-Fe 2 0 3 . Saturation indices for minerals present in trench A and C are summarized in Figure 6.7 and 6.8. Phases in trench A were at equilibrium with respect to AIOHSO4, goethite, lepidocrocite, gypsum and anhydrite, indicating possible solubility controls for Al , Fe, Ca, and SC>4=. Solutions are supersaturated with respect to anhydrite and gypsum near the surface, but under the red "accumulation" zone (Chapter 5) at a depth of 1-2 m, SI values for both phases decrease until they become unsaturated. In trench C, solutions were near equilibrium with alunite, jurbanite, diaspore, anhydrite, and gypsum. 160 Ch.6-Partitioning of Elements.. Ch.6-Partitioning of Elements. Ch.6-Partitioning of Elements... Solutions from samples taken from trench C were near equilibrium with alunite, jurbanite, diaspore, anhydrite, and gypsum; while Cu levels are apparently controlled by chalcanthite CuS0 4 »5H20, tenorite CuO, cupric hydroxide Cu(OH)2 , antlerite Cu3S04(OH)4 , brochantite Cu4(S04)(OH)6. Hcr Si ci is significantly correlated (P < 0.01) to the magnitude of SI for numerous mineral phases: antlerite (rs = + 0.58), brochantite (rs = +0.59), langite (rs = +0.60), tenorite (rs = +0.63), Cu(OH) 2 (rs = +0.62), diaspore (rs = 0.58), Zn(OH) 2E and ZnO active (rs = +0.55). These trends would seem to indicate that as Hcr s;ci decreases, Cu-phases become unsaturated and are more likely to dissolve. No phases were near saturation for Zn, Mn, and Mo in any sample, suggesting other mechanisms are likely limiting their solubility, such as adsorption and coprecipitation reactions. Several authors indicate that Fe- and Al-oxides are effective scavengers of Zn and Mn by coprecipitation (Sposito, 1989) and adsorption (Schwertmann and Taylor, 1989). Under acidic conditions, sesquioxides will have excessive positive charges and should be an effective adsorbant for M0O4". Bohn (1985) states molybdate reacts strongly with iron hydroxides and soluble Mo concentrations may be quite low in acid soils. Secondary mineral phases which have been confirmed by X R D are gypsum, hematite, chalcanthite, and langite (Chapter 4). Other mineral phases may be present but are unresolvable because only minute quantities are present, are poorly crystalline, or their peaks are masked by other more crystalline phases. Stability diagrams are plotted to examine possible mineral species responsible for controlling H2O extractable levels of Fe, Al , Cu, and SO42" with phases reported in mine 163 Ch.6-Partitioning of Elements... drainage systems and other similar weathering environments (acid sulphate soils). The data used to generate the solubility lines was taken from Bigham et al. (1996), Ball and Nordstrom (1991), Lindsay (1979), and Schwertmann and Taylor (1979). This method has been used elsewhere to describe mineral solubility data (Karathanasis and Thompson, 1995). A thermodynamic stability constant has yet to be determined, however, Bigham (1996) reports an IAP (ion activity product) for schwertmannite from selected mine drainage solutions. This IAP was used to calculate the schwertmannite line used in Figure 6.9. 164 Ch.6-Partitioning of Elements... + CD (JH C H 2.75 3.00 3.25 3.50 3.75 4.00 4.25 pH 14 12 + 10 P H &. 8 • • * boundary at pH 3 boundary at pH 3.7 \ cupric ferrite 3.50 3.75 4.00 4.25 4.50 4.75 n 2+ pCu trench A trench B trench C trench D Figure 6.9 Composi t ion o f water extraction solutions relative to the stability o f common Fe minerals from acid mine systems 165 Ch.6-Partitioning of Elements... Lines for jarosite, schwertmannite and cupric ferrite on Figure 6.9, represent the solubility lines at the lowest [S042"] and [Cu2 +] observed in the H 2 0 solution data. Two lines are plotted for cupric ferrite, alunite, jurbanite, and basaluminite (Figure 6.9 and Figure 6.11) representing the mineral stability within the pH range of the H 2 0 solution data. Two lines, based on the maximum and minimum pH and [S042"] values encountered from Ff 20 solution data, are plotted for each Cu-sulphate mineral on Figure 6.10. It is obvious from the diagrams several mineral phases may act as solubility controls in these samples at the pH and the pFe 3 +, pCu 2 + , p A l 3 + and pS0 4 2" levels observed. Solubility controls for Fe are goethite or hematite, , for Cu, brochantite and langite, and for Al; alunite, jurbanite, or basaluminite. Fe levels in all the water solutions appear to be controlled by goethite. The meta-stability of oxidized Fe phases likely results in a mix of phases present, but goethite appears to control the solubility of Fe. Control of Cu levels in the water solutions from trench D may be controlled by brochantite and langite in trench C and D. Lindsay (1979) states that the minerals governing the solubility of C u 2 + in soils are not known, but suggests that soil-Cu may be cupric ferrite. No Cu sulphate minerals appear to control Cu levels in trench A and B. Results seem to indicate that no single phase acts as a solubility control for any of the metals. The brief contact time with water may not have been sufficient to establish an equilibrium. 166 Ch.6-Partitioning of Elements. 167 Ch.6-Partitioning of Elements. fN 168 Ch.6-Partitioning of Elements... relationships with morphology One of the underlying objectives of this research was to investigate the accumulation of metals and weathering products in morphologically identifiable zones. Using Hurst colour rating, correlations were identified between colour (Her) and Fe (and other metals) (Chapter 4 and 5). Figure 6.12 shows plots of extractable Fe correlated (P < 0.05) with Hcr sj ci. Other pools correlated to HcrSiCi were CaH2o (rs = -0.39), CuLici (rs = +0.39), and K H c i (rs = +0.53). Extractable Fe, from all the solutions, correlated to HcrSiCi, as expected based on observations noted in Chapter 4 and 5. Extractable Fe from HC1 and A A O are most strongly correlated to HcrSiCi suggesting secondary Fe phases contributing to pigmentation are soluble in HC1 and A A O . Least squares fit lines for the two relationships are : (1) Fe H C i = (L65xl0 6 ) x Hcr s i c l " 1 7 5 1 r 2 = +0.62 (2) FeAAO = (2.60xl06) x H c W 1 ; 6 9 8 r 2 = + 0.63 If the extractable Fe from the extraction steps prior to FCAAO is summed, then the coefficient of determination for the least squares fit lines improves, and is described by the following relationship: SFe A A o = Fe H 2 o + F e L i a + FeHci + Fe A A o = (4.00xl06) x H c r s i c f 1 6 7 1 r 2 = +0.80 169 Ch.6-Partitioning of Elements. o o o o V PH o o Or O o O o o 2% \4 oo * o o o VO o o CN 00 s 3 o u 3 X o o V PH Tf OO O o 0 o o ,o o o o o o o o o so o VO o T f o cs 3 o > C CD o CD o o o o o o o o o o o o o o o o © o o CN CN ^ H ~ H 3 j qqBpBJjxa JQH © © v PH O o 0 oo O o o o I — I — I — I — I — I — I — I — I — h oo © .S 3 O © Tf © CN o 3 X © © © © © © o o o © © © O O V O T f C N O O O V O T f C N CN —' — —• - H ajqBpEJpra QZH © © © © CN © © © © © © © © © 3J 3]qBPBJ}X3 Q33 © © © © V PH *—' VO © © O-r © OOT °> © v o o o o o o 00 c 3 " o u © c Tf 3 X © CN © © © © © © © © © © © © © o © © © © © © © © © © VO IT) T f CO CN ~ H 3 g ajqupB-nxa o w § .2 -a — 0) I . 8 £ a> o jo "o cs -<-> U H cN 170 VO t H Ch.6-Partitioning of Elements... As suggested in Chapter 5, HcrSiCi values greater than 30 are not sensitive to changes in Fe but as extractable Fe increases and Hcr si ci drops to less than 30, Hcr si c [ becomes very sensitive to changes in extractable Fe. This Her value probably reflects the lowest level of colour discrimination perceived as may be noted by changes in Munsell colour. According to this data, this occurs at 0.2-0.3% extractable FeAAO-This redness criteria (Hcrs;ci<30) roughly coincides with two groups of samples clearly separated when examining total (Leco) S and H 2 0 extractable S as SO42" (Figure 6.13). The group with low total S and low S as S04 2~ (low S group) is made up of samples with HcrSid ranging from 39 to 88 with an average of 58 ± 16. . The other group is made up of samples with Hcr s i ci ranging from 13 - 100 and higher S content (high S group). The high S group has an average of 41 ± 2 8 . bo a o E— 60000 50000 + 40000 + 30000 20000 10000 A A A • + -+-10000 20000 30000 H20 Extractable S (mg/kg) 40000 50000 Figure 6.13 Total S vs. H 2 0 extractable S. 171 Ch.6-Partitioning of Elements... Extractable metals from the all red and all non-red groups were compared using the non-parametric Mann-Whitney U-test. Results are summarized in Table 6.5. Several extractable metals, Al , Ca, Fe, Si and S as SO4 2 ", are significantly greater in the red samples in at least one extracting solution indicating accumulation of these metals.. Only Cu and K are greater in the non-red samples. To determine the potential mobility of a given metal associated with secondary weathering products, the distribution among the 5 extraction steps and the absolute amount of that metal, needs to be considered. Extractable metals from the red samples collected in trench A and C were compared using the non-parametric Mann-Whitney U-test. Results are summarized in Table 6.6. No metal was significantly different at a P < 0.05 level of significance, but several trends were noticed and will be discussed here. Most of the extractable metals were significantly greater in trench C, except for FeH20/Lici/CBD, K A A O and NaAAo, which were greater in trench A suggesting they accumulated preferentially in trench A. Possible explanations for the accumulation of FeH2o/uci/CBD, KAAO and NaAAO include: (1) conditions in trench A, particularly the discontinuation of acid leaching and the accumulation of metastable minerals between moisture events may be more conducive to the precipitation and accumulation of Fe, Na and K-containing phases, (2) these phases may be not be forming in trench C due to some chemical inhibition, or (3) these phases may be removed from trench C due to acid leaching. Phases that could lead to these observations are K-jarosite and natrojarosite. The other two trenches were not compared because of a lack of samples with HcrSiCi < 30. 172 Ch.6-Partitioning of Elements.. N o U ] U ] U ) wl £ X X X X CO CO CO CO + + + t/) CO c/3 CO CO I X co to CO u o < + o < < + < + < + o a. E o m o p o 7J ts c fi a " u o t i " S C O S .£P '^ 00 u g ' S II 'X II CO + w '—--o X > O E S3 u " -S c " ,« 3 II X o T3 O . 6 o u VO V C N U S to CO -—- to "I ^ ^ c l ^ '—to — C O CO col col fi cl cl C "*•« C C C CO CO CO =1 cl cl C cl S| C 3 c l C/3| cl cl cl cl O 2 K (N 1 — 1 T J EC S 9 Q < u ta u Q m < + o < < + 0 < + U + o o •s o as w E £ cu e o V a. c 00 3 X I - c o « o V 8 | a. c t: ts g ^ CO w in it: C -2 C S S.5P ' S o o 00 c c 2 u ^ E a.'S E o £ xi 51 X 173 Ch.6-Partitioning of Elements... 6.4 Conclusions Sequential extractions provide useful information on the solubility and the partitioning of metals among secondary weathering products from waste rock samples from the Gibraltar mine site. Use of a water-extractable step allows the application of a geochemical model to examine mineral solubility relationships. Mineral references were valuable additions to the test in order to evaluate the effectiveness of each extracting solution on mineral assemblages, including secondary phases common to surficial weathering environments. References composed solely with primary mineral phases (MRI and MR2) were only slightly soluble in all steps, and tended to be attacked most by HC1 solutions. Of the other mineral phases, solubility decreased in the order, hydrous ferric sulphate, gypsum, K-jarosite, limonite, and hematite. The oxidized Fe minerals were most soluble in A A O and CBD solution. The elements most extracted were Fe, Ca, and S as SO42". Accumulation of Cu, Fe, and Mn was related to the acidity/pH of the system, which was related to the available buffering capacity. Retention of metals in post leach areas was greater than in areas never leached and under active leaching. Secondary weathering products from the waste rock environment appeared to sorb several metals (Cu, K, Mg, Mn). Sequential analyses and geochemical modeling indicate several different phases may have roles in controlling metals loading by acting as solubility controls. Several metals seemed to be affected by the different weathering regimes dictated by trench location on the dump and in relation to dump leaching; notably Na, K, Mn, and Cu. 174 Ch.6-Partitioning of Elements... Generally, alkali metals (Na and K) were associated with soluble (efflorescence salts) and metastable (e.g. jarosite and alunite) phases. Evidence suggests that Na and K tend to be more soluble or are more mobile prior to and during leaching, but undergo rearrangement in the post leach period to associate with phases with greater meta-stability and less solubility, such as Na- and K-jarosite. Mn and Cu seem to be associated in more soluble phases in the post leach areas, and less soluble phases in the pre-leaching and leaching areas. No Mn phases were indicated, thus other mechanisms are likely important. Cu levels are controlled by Cu-sulphate phases such as chalcanthite and langite. Other metals did not seem influenced by the weathering regime. Alkaline earth metals (Mg and Ca) were likely controlled by phases similar to epsomite and gypsum. Iron is likely to be associated with several more metastable phases, including jarosite minerals, amorphous Fe, Fe oxides and oxyhydroxides, which explains its ubiquity, as each phase forms under different conditions. Like Fe, A l is likely associated with several phases with varying meta-stability, including, jurbanite, alunite, and basaluminite. An amorphous aluminosilicate seems likely to control Si and contribute to Al control. Sulphate phases have been mentioned with Fe, Al , Ca, and Cu as solubility controls. Zn storage is attributable to a combination of soluble Zn phases, occlusion in other soluble phases, or sorption on to sesquioxides. Generally, trench A and B samples accumulated greater amounts of metals (secondary weathering products) than trench C and D. The mechanisms for the differences are likely the result of the different solubility's of secondary phases in the 175 Ch.6-Partitioning of Elements... various trenches, the discontinuation of acid leaching which allows mineral rearrangement and an opportunity for the precipitation of new phases, and the removal of gangue minerals. According to the literature, the accumulation of metals in trench A and B, especially Fe, is most likely attributable to the accelerated weathering and low pH from acid leaching, leading to enhanced sulphide oxidation and the concomitant weathering of other primary mineral phases. Another factor is that there are high leach rates removing weathering products from trench C, and trench D is limited to natural weathering conditions. Several metals and sulphur (Al, Ca, Fe, Si, and S as S042") appear to accumulate in the red samples. Fe is strongly correlated to Hcrsjci. Hcr s;ci may be valuable in the field as an indicator for the accumulation of these other metals, although more data needs to be gathered to refine the relationship. These investigations indicate that acid leaching seems to have an effect on the distribution of several metals and the net accumulation of metals. If we assume trench D is undergoing "natural" weathering, what has happened in trench A and B is that this "natural" weathering has been greatly accelerated by acid leaching, thus gangue and easily weathered mineral have been weathered. The products of this weathering have been partially removed (by acid leaching and atmospheric water), some have been sorbed, some occluded, some pseudomorphed into existing minerals/crystals, and some have recombined resulting in the authigenic formation of secondary minerals. When the leaching was stopped, there began a period of readjustment of chemical equilibrium. 176 Ch.6-Partitioning of Elements... Trench C is the example of continued active acid weathering - its products should be the least in equilibrium and are subject to removal by the high leaching rates. Thus, comparisions can be made between trench D, which reflects natural slow weathering, trench C, active high kinetic weathering (i.e. very acid), and A and B that reflect changing environmental conditions. 177 Ch.7-Dissolution of Stored... 7. Dissolution of Stored Weathering Products from Highly Oxidized Waste Rock 7.1 Introduction Secondary weathering products formed in mine waste weathering environments can serve as a sink for a variety of metals, including Fe, Ni, Cr, Cu (Ribet et al., 1995; Blowes and Jambor, 1990). Dissolution of metastable weathering products (e.g. Fe oxides, oxyhydroxides and oxyhydroxysulphates) with their associated components (Cu, Zn, Al) may result in the transfer of pollutants (i.e. metals) to the environment. A recent study of a Canadian mine estimated up to 40% of the metals in seepage exiting the oxidized waste rock pile originated from stored oxidized products (Choqette et ah, 1994). Stored weathering products may exist in several forms including secondary minerals with different degrees of solubility and mobility. Common secondary minerals in mine waters and their relative solubility are listed in Alpers et al. (1994). In the early stages of mine waste weathering, highly soluble Fe sulphates such as melanterite, Fe n S04»7H 2 0, copiapite, Fe nFe 4 m(SO4)6(OH)2»20H2O, coquimbite, Fe I I I2(S0 4)3'9H 20, and their dehydration products, are commonly found as efflorescent salts (Alpers et al, 1994). Soluble mineral phases are typically formed during drying periods when solutes are concentrated by evaporation. Continued weathering leads to the formation of less soluble Fe phases, such as schwertmannite, Fe 8 0 8 (OH) 6 S04, jarosite, KFe 3(S0 4)2(OH) 6, and goethite, cc-FeOOH (Schwertmann and Taylor, 1989; Bigham, 1994; Nordstrom, 1982). The exact mineralogical form of the secondary minerals is site-specific and depends upon a number of factors, including, solution pH, waste rock mineralogy, water content, degree of oxidation, and time 178 Ch.7-Dissolution of Stored... (Schwertmann and Taylor, 1989; Nordstrom, 1982). Solubility leads to increased mobility in the presence of a transporting medium and a release path. The quantity of metals retained in a dump will depend on the differential rate between the precipitation/formation and dissolution/solubilization of secondary minerals in the rock dump. Mobilization of soluble components will be controlled by parameters influencing the transport medium such as flushing frequency, water migration pathways, moisture retention, dump construction, and geochemical factors such as ionic strength, solution pH, and presence of ligands. One of the dominant pedogenic processes occurring during the early stages of mine soil genesis is the incorporation/decomposition of organic matter (Roberts et al., 1988), which will lead to the presence of ligands entering mine waste. Mine reclamation may include the use of soil (Bell et al., 1994), organic rich material such as sewage sludge (Sopper, 1992; Salahub et al., 1991), composted municipal waste (Pierce et al., 1994), and wood waste (Tasse et al., 1997). Through time, a self-perpetuating vegetative cover will develop and organic material will become incorporated with the mine waste. In natural environments, microorganisms and decomposition of plant and other organic material produce a variety of organic acids. Simple organic acids, including formic, acetic, oxalic, citric, and butyric, appear to be normal constituents of the soil and are important agents in the weathering of rocks and minerals, and the mobilization and transport of metals (Lundstrom and Ohman, 1990; Tan, 1989; McColl and Pohlman, 1986; Stevenson, 1967; Kaurichev et al , 1963). Concentrations of such acids in soils are generally in the range 10"3 to 10"5 M 179 Ch.7-Dissolution of Stored... (Huang and Violante, 1986; Stevenson, 1967; Kaurichev et al., 1963). There has been much research on the influence of organic acids on Al from soils and minerals (Huang and Violante, 1986; McColl and Pohlman, 1986), but little has been done to examine the role organic acids play on the release of metals from mine waste. The objective of this study is to assess the potential for the dissolution of stored secondary weathering products over time when placed in contact with various extraction conditions (infiltration/evaporation cycles, different pH, ionic strength, and chelating capability), under oxic conditions. The purpose is to observe temporal trends for metal release occurring in a rock dump to get a better understanding of the factors controlling dissolution, determine which metals are of greatest concern to metal loading, examine metal solubility under different conditions for morphologically different zones, and examine differences between two dissolution procedures. 7.2 Methods Two experimental procedures were designed to examine the dissolution chemistry of weathering products from oxidized mine waste rock. The procedures address different weathering conditions. The aim of these procedures is to examine the release or dissolution of metals from phases susceptible under different conditions (i.e. leaching solutions) and changes in dissolved metal levels over time. Waste rock near the surface of a dump experiences repeated wetting and drying which is an important process affecting water chemistry in mine waste material (Nordstrom, 1982). 180 Ch.7-Dissolution of Stored... Wet and dry cycling at the surface is due to atmospheric rainfall and infiltration/evaporation. Infiltration events result in the rapid dissolution of soluble sulphate minerals formed during dry periods resulting in striking variations in metal concentrations in runoff (Alpers et al., 1994; Bayless and Olyphant, 1993). Mineral dissolution is affected by several factors, including, solution water pH (proton-promoted dissolution) and the presence/absence of a chelating ligand (ligand-promoted dissolution) (Casey and Ludwig, 1995; Stumm et al., 1985). The two procedures devised to examine metal dissolution were, (1) a simple wetting and drying procedure to examine changes in the mass balance of the waste rock material and metal loading in leaching solutions due to rapid dissolution of secondary minerals, and (2) a series of batch experiments to examine the significance of solution pH and the presence of chelating ligands to metal dissolution. Citric acid was chosen because it is commonly found in soils and has been shown to be an aggressive weathering agent of minerals and soils (Manly and Evans, 1986; Pohlman and McColl, 1986). Sample selection for the experiments was based on colour criteria indicating the abundance of oxidized Fe phases and a range of other metals associated through weathering products (Chapter 5 and 6). Samples were air dried and sieved through a 0.053 mm stainless steel sieve prior the experiments. The < 0.053 mm (silt+clay) fraction was selected for these experiments because of the higher surface area:mass ratio compared to the 2 - 0.05 mm (sand) fraction. General characteristics of the samples and reference materials used in the wet-dry and batch experiments are presented in Table 7.1 and 7.2. 181 Ch.7-Dissolution of Stored... -a o on O < < 3 .a o ,» U SC •a a. o —I T f T f 8 * ^ n ! - n m M is o o o o o o o o <N CN C - i n | _ _ o) co T f - H "5 ov o o o o i / - > o \ o 2 a \ o > o o o * * * * * * * * < < f f l f f l U U P Q 3 -a S ft 60 '—I cl cn *C e •c 10 P. x •a •c T3 o g a. 2 o 'cfl c o QJ vi bol 3 cn S w S o 3 ca 182 Ch.7-Dissolution of Stored... Samples selected are grouped as type 1 (scarce amounts of secondary weathering products, high Her) or type 2 (abundant amounts of secondary weathering products, low Her). Sample classification was based on the amounts of Cu and Fe associated with the oxidized Fe phases and sample morphology. More describing these samples are presented in previous chapters and the Appendix. wet-dry cycling experiment Five samples (2, 9, 16, 27, 33) were selected for the wet-dry cycling experiment. Samples from each trench with varying amounts of secondary weathering products were selected (Chapter 5 and 6). Two samples with low Her (9, 27) and three samples with high Her (2, 16, 33) were selected (Table 7.1). Five samples, one mineral reference (MR2), and blank were subjected to the same treatment in this experiment. Materials (samples and reference) were weighed into a Nalgene™ disposable filter apparatus with a 0.10 pm nylon micropore membrane filter with a tubing adapter for vacuum filtration. The apparatus consisted of an upper and lower compartment with a divider in the center. The upper compartment was not sealed at the top but covered to prevent atmospheric particulates from entering. The bottom of the upper compartment had a threaded collar and acted as a seat for the filter. The bottom compartment was fixed onto the collar and captured solution as it passed through the filter. All materials used in the filter apparatus comply with the Superfund Amendment Reauthorization Act regulations and are free of heavy metals. 183 Ch.7-Dissolution of Stored... Each experiment consisted of the following steps: (1) addition of 2.0 g of sample/reference material to upper compartment of the filter apparatus, (2) oven-dry sample + assembled filter apparatus at 40°C to constant mass, (3) addition of 40 ml of distilled-deionized water (DDW) to sample (20:1 solutiommass ratio), (4) equilibrated for 2 hours on a oscillating shaker for 2 hours, (5) 30 minutes of vacuum applied to extract solution from sample (to the lower compartment) and 30 additional minutes for drying, and (6) oven drying at 40°C until mass was constant. In all cases, drying time in the oven did not exceed 48 hours. Aliquots were collected for pH, Eh, E C measurements immediately after each cycle. The remainder of the solution was transferred to polyethylene bottles and stored in the refrigerator (4°C) prior to further analysis. The wet-dry cycle (3-6) was repeated until metal release achieved apparent equilibrium (17 cycles). batch experiment A total of 8 samples (2, 9 11, 16, 22, 27, 31, 33) were selected for these experiments. Two samples from each trench were selected, one sample with low Her and another with high Her (Table 7.1 and 7.2). In addition three reference materials were included: mineral reference 2 (MR2), extraction reference 3 (ER3), and gypsum powder ground to pass <0.053 mm. Eleven (11) different materials were used for these experiments. The extracting solutions used were three citric acid solutions buffered to pH 2.3 (cit-lowpH), 4.6 (cit-medpH), 6.5 (cit-highpH), acetic acid or HOAc (pH 2.5), nitric acid (pH 2.5) and distilled-deionized water (pH 5.7). All solutions used were prepared in 9L volumes, 184 Ch.7-Dissolution of Stored... spiked with several drops of toluene, and stored in the refrigerator until use. The batch experiment involved shaking 1.0 gram of silt+clay sized material in 30 ml of extractant in a 50 ml screw cap centrifuge tube. Duplicate samples were allowed to react for 153 days with 80% solution exchange/renewal at 1, 2, and 6 hours, and 1, 3, 9, 20, 41, 100, and 153 days on a oscillating shaker in the absence of light. At each sampling time, samples were centrifuged at 2000 g for 20 minutes, 80% (24 ml) of elutriate removed, and fresh extracting solution added. Aliquots were taken from each elutriate for pH, Eh, E C measurement, and the remainder stored in high density polyethylene bottles in a refrigerator (4°C) prior to analysis. The shaker oscillated gently in approximately 0.5 cm diameter circles at a rate of 150-180 oscillations per minute thus minimizing the effects of particle abrasion. Centrifuge tubes were resuspended and uncapped for 2-4 hours daily to maintain oxic conditions in the solutions. analyses All solutions were analyzed for total dissolved S as SO42", A l , Ca, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Pb, Si, Zn. Sulphate was determined by turbidimetry using a spectrometer (Rhoades, 1982). The concentration of all elements, except Na and K, were determined using an ICP-AES. K and Na were determined by atomic absorption spectrometry on a Perkin-Elmer AAS model 306 instrument using an air-acetylene flame. Data from distilled-deionized water analyses (wet-dry cycling and batch experiments) were entered into MFNTEQA2 to identity potential precipitation reactions that may act to 185 Ch.7-Dissolution of Stored... control metal concentrations. Details are provided in Chapter 6. 7.3 Results and Discussion The complete data for the wet-dry cycling and batch dissolution studies are reported in the Appendix. The level of precision, for the analysis of elements was generally within 10% level of precision, but tended to decrease (> 10%) as analyses approached the minimum and maximum detection limits of the instrumentation. Some variation occurred randomly with no apparent pattern. Increasing dilution lead to increased variability and possibly errors introduced by mixing and pipetting. wet-dry cycling experiments Solution conditions (pH, Eh, EC) measured in the leachates suggest some secondary minerals undergo rapid dissolution (Figure 7.1), except in the reference material. Acidity released from all samples , except for 33, and the reference material (MR2) results in values of initial solution pH < 5, which is well below the value for the deionized water used in these experiments (pH 5.5 - 5.8). Values of solution pH for sample 33 ranged from pH 4.5 - 6. Solution pH values for all the samples and the reference ranged from pH 3 - 5.8 and remained relatively uniform for each sample during the experiment. Low pH values were attributed to the release of H + ions from sorption sites and reserve acidity (i.e. Fe 3 + and A l 3 + hydrolysis). Acidity in solutions from MR2 increased with each cycle suggesting sulphide oxidation. 186 Ch.7-Dissolution of Stored.. Ch.7-Dissolution of Stored... Electrical conductivity values were quite high in the initial wetting events (2.3 - 0.55 mmhos/cm) but decreased rapidly and reached a steady-state level in samples 2, 33, and MR2 by cycle 3, and cycle 7 for the rest of the samples. Steady-state E C values were generally < 0.1 mmhos/cm, and exhibited some random variation. Loss-on-extraction % (or LOE%) is the decrease in sample mass after each wetting event, likely due to the dissolution of soluble secondary minerals retained on the sample. Total L O E % values (cumulative L O E %) concur with the changes observed for EC. All samples had measurable L O E levels and reached a plateau at the same cycle E C reached steady-state. Dramatic L O E was experienced by the reference sample (MR2) during cycle 13.This was likely due to a weighing error or loss of solid sample material since a corresponding rise in E C was not evident. Total cumulative L O E % values ranged from 21% to 1.5%. E h values initially ranged from 255 - 469 mV, but began to converge towards 330 - 350 mV with each wet-dry cycle. Leachates collected from MR2 indicate a scarcity of soluble phases and suggest steady-state dissolution is occurring. Differences within and between samples trenches (type 1 and 2) were evident in measurements of E C and LOE. Type 2 samples (9, 27) have higher initial E C values and decrease more rapidly and for a longer duration than type 1 samples. Changes in E C values were limited in type 1 samples by cycle 4 and for type 2 samples by cycle 7. The changes in E C were reflected in the L O E curves by the rapid mass loss experienced by type 2 samples in the first 5 cycles. Differences between the groups were not evident from the pH and E h values. Leachate chemistry for several of the metals analyzed is shown in Figure 7.2. 188 Ch.7-Dissolution of Stored... 1 2 3 4 5 6 7 9 10 11 12 13 14 15 16 17 Cycles 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Cvdcs 2 3 4 5 6 7 9 10 11 12 13 14 15 16 17 Cycles a soo i E 400 ioo H 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Cycles I 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Cycle 140(1 120(1 a 100(1 i SOO 3. 60(1 < 400 Olat 290 0 1 2 3 4 5 6 7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Cycles 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Cycles 5!) 2500 ! 2000 1 1500 i 1000 | 500 0 1 2 3 4 5 6 7 9 10 11 12 13 14 15 16 17 Cycles R T f i I I I I I I s£=i 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Cycles Graphs on the left show the soluble metal in solution from each cycle; graphs on the right show the cumulative metal released. Figure 7.2 Plots of Al , Ca, Cu, Fe, and S04 2" dissolution from the wet-dry cycling experiment. 189 Ch.7-Dissolution of Stored... Two columns of graphs are shown on each figure; in the left column, the y-axis shows dissolved metals from the sample in each cycle, and in the right column, cumulative dissolved metals released. Differences between type 1 and 2 samples can be seen in the results for several of the elements, Ca, Cu, S042", and Si (not shown). During the initial cycles, type 2 samples released greater quantities of these metals compared to type 1 samples. Generally, there was an initial flush of dissolved metal during the initial cycles for all samples, followed by limited release in the remaining cycles. The exception was for dissolved Si levels which indicate dissolution of a constant quantity in each cycle suggesting steady-state dissolution was occurring. Determinations of the other metals (Al, Fe, K, Mg, Mn, Na, Zn) in all samples indicate a general trend of very rapid solubilization and flushing of metals during the first 2-3 cycles, the most significant release occurring during cycle 1, followed by a period of limited metal release. Total levels of dissolved metals from the samples varied but in the following range: Ca, SO42" < 5% (based on sample mass); for Al , Cu, and Fe 0.1 - 1%; and for the others < 0.1%. Type 2 samples released higher cumulative levels of Ca, Si and SO4 ". Sample 33, from trench D, released the greatest amount of Al , Cu, Mn, Na and Zn. batch experiments Solution quality representative of conditions (pH, Eh, EC) during the batch experiments is presented for sample 2 and 27 in Figure 7.3. 190 Ch.7-Dissolution of Stored... PS 9 * 2 ja a s o o o I—I M H J O . O J i . t f t f t f s u c o o o o o o o o o o o o o o © o © o o o o © © © © © © © I so «-i -rr Hd © © © o o © © © © © © m © < / - ) © v - ) © > / - > © © © © © © © b TO E (A«) MH N O OO » T t N O Tto/soqar iu) 3 3 © © & D E *C a> a u S8 X i E o <s -o & « E « im O 83 T 3 88 S s "o m i -S ii. 191 Ch.7-Dissolution of Stored... In most cases, except for water, the conditions observed were determined by the extracting solution and not the waste rock or reference samples. Solution quality observed in water solutions (from samples and references) was controlled by metals and mineral dissolution and exchangeable acidity from the waste rock. Citrate solutions were buffered at pH 2.2 ± 0 . 1 , 4.6 ± 0.2, and 6.5 ± 0.2 and did not fluctuate significantly for the duration of the experiment. Of the other solutions used, pH in the solutions generally decreased in the following order: DDW (pH 4.1 ± 0.9) > H N 0 3 (pH 2.7 ± 0.4) > HO Ac (pH 2.6 ± 0.4) (except solutions from sample 11, where pH in HO Ac was greater than DDW). Solution E h values represent the sum of all the oxidation-reduction activity in the solution including all chemical and biological reactions. Aerobic conditions were maintained in all solutions collected. Generally, Eh values in the various extracting solutions decreased in the following order: HNO3 (500 ± 72 mV), HOAc (464 ± 53 mV), DDW (400 ± 58 mV), cit-lowpH (323 ± 35 mV), cit-medpH (269 ± 60 mV), and cit-highpH (258 ± 43 mV). Lower E h values in citrate solutions may have been the result of biological activity in the solutions from the samples. As expected, Eh values increase with decreasing pH. Electrical conductivity measurements in the solution decreased in the following order: cit-highpH (11.5 ± 0.5 mmhos/cm) > cit-medpH (7.7 ± 0.5) > cit-lowpH (3.4 ± 1.2) > H N 0 3 (1.8 ± 0.8) = HOAc (1.7 ± 0.6) > DDW (0.6 ± 0.8). Leachate chemistry for several metals/elements (Cu, Fe, SO42") analyzed from batch experiments are presented for samples 9 and 27 in Figure 7.4. The figures show cumulative metal concentrations plotted against time. 192 Ch.7-Dissolution of Stored.. 193 Ch.7-Dissolution of Stored... Cumulative dissolved metal levels released up to day 153 (mg element/kg sample), or CDM153, ranges from up to 7%, down to levels not detected for each metal. Generally, for each metal, the shape of the cumulative metal curves are uniform for all the samples although CDM153 levels vary with each sample. CDM153 levels for Cu in trench A and B were lower than for C and D. The shape of cumulative metal curves vary with extracting solution. Citrate solutions showed greater dissolution efficacy resulting in higher CDM153 levels than in solutions of HOAc, HNO3, and water, except for a few cases involving Ni and Pb. The cumulative amount of metals released (CDM]5 3 ) decreased as the buffered pH levels rose in the citrate solutions, except for Si, K, and SO42" (highest C D M 1 5 3 in med-pH for former and high-pH for latter 2 elements). Metals released in greatest quantity were SO42" (16% of the sample mass) or S (5%), Fe (7%), Ca (6%), and Cu (3%). Leachate chemistry for reference materials confirms dissolution is occurring and agrees with results from wet-dry cycling. The only difference is that chalcopyrite oxidation is likely occurring in solutions in contact with MR2 as indicated by the presence of significant quantities of dissolved Cu. The data does not indicate stoichiometric dissolution which may be due to significant re-adsorption onto mineral surfaces, precipitation of new phases during the experiment, or interference from the analytical technique. Cumulative metal release plotted against log-time curves for sample 9 is shown in Figure 7.5. Data plotted on a log-time scale show trends obscured on a linear scale by spreading the data out between each sampling event. 194 Ch.7-Dissolution of Stored.. Ch.7-Dissolution of Stored.. Ch.7-Dissolution of Stored... Trends may be hidden using a linear scale when solutions with significantly different extracting efficacy and C D M i 5 3 , are plotted together. The relationship between curve shape, CDM153 levels, and extracting solution, mentioned above, remains the same. Three different curves seem to be recurrent for all the leachate chemistry data (cumulative metal release) when plotted against log-time, suggesting results can be grouped based on the shape of the curve describing cumulative metal release. Figure 7.6 shows the 3 plots indicating the amount of dissolved metal released and 3 corresponding curves for cumulative metal levels. The plot for cumulative dissolved Al levels against log-time resembles curve C. During the initial sampling events (1-2 hours), a small flush of Al was detected as noted by the positive slope on the curve (Figure 7.5), then the quantity of dissolved Al levels off for sampling events up to day 3-9 (the exact days depending on the extracting solution), and finally rises during the remaining sampling events. Several other elements including, Cu (2, 9, 11, 16), K, Mg, Mn, Na (samples 22, 27, 31, 33), Zn, Mo, Ni, and Pb behave similarly, although the time for the various inflections in the curve varied with the sample and extracting solution. In some samples, an initial flush was not detectable or poorly defined. Data from the citrate solutions produce curves more similar to curve C in Figure 7.6, especially during the latter sampling events. Curves describing cumulative Ca release (Figure 7.5) resemble curve B (Figure 7.6). Ca release occurred very rapidly during the initial sampling events, decreased to a minimum between the 3 r d (6hrs) and 5 t h (3 days) sampling events, then remained constant and very limited for the duration of the experiment. Sulphate, from all samples and solutions, and Cu, released from sample 33, in citrate buffered 197 Ch.7-Dissolution of Stored... solutions behave similar to Ca (curve B). Cumulative release of Fe resembles curve A. The quantity of Fe liberated in the latter sampling events generally, is greater than during the earlier events, thus most of the Fe released is after 1 week. Si behaves in a similar fashion as Fe. The source for each dissolved metal can be inferred based on the shape of the plots for cumulative dissolved metals against log-time. The 3 curves describing metal dissolution and the corresponding of groups of metals are: (1) curve A (group A = Fe, Si, and Al), metal loads are due to the dissolution of either primary minerals or metastable secondary minerals which are not soluble during short contact periods, (2) curve B (group B = Ca, Cu, and SO4 2 " ), metal loads due from the dissolution of easily soluble secondary minerals, and (3) curve C (group C = K, Mg, Mn, Na, and Zn), metal loads due to the dissolution of easily soluble secondary minerals and the dissolution of primary minerals or metastable secondary minerals which require longer contact time with solution. Dissolution of potassium (K) and sodium (Na) appear to follow the trend on curve C, but depending on the sample and the extracting solution may also follow curve A or B. Although the metals can be categorized into these three groups, in all likelihood these classifications are rudimentary and overlapping, and dissolution is from a combination of different phases. The proportion of phases with differing solubility ultimately determines the shape of the curve. The metals are grouped according to their behavior in Table 7.3. The fact that data from the solutions (from the samples) can be grouped using metal dissolution suggests similar phase(s) control metal solubility in each sample. Depending on the shape of the 198 Ch.7-Dissolution of Stored... cumulative dissolved metal curve (Figure 7.6), metal dissolution may not attain a steady state for hours, days, or weeks into the experiment. Table 7.3 Classification of metals based on the cumulative metal release curves described in Figure 7.6. Dissolution Curve A B C Dominant group Fe Ca Al Mn Si S0 4 = Cu Na K Zn Mg Secondary group Al Cu Mo K Ni Mo Pb Metals grouped together under a dissolution curve type, show a strong similarity to that curve if it is in the Dominant group, and shows weak similarity to the curve or only follows the curve in a few samples if in the Secondary group. Metal dissolution or release rate varies with the extracting solution (pH and presence of ligand) and the time elapsed since beginning the extraction. Dissolution was most rapid during the initial day of the batch experiment, and decreased significantly by day 1. The shape of the cumulative metal dissolution curve for all the metals generally f it that of a logarithmic function. The dissolution rates were characterized by three time intervals, (1) rapid release during the initial period, (2) slow or limited release during the latter part of the experiment, and (3) an intermediate rate of metal release separating the two aforementioned intervals. The highest rates of metal dissolution observed for a sample were 80% sample mass loss/day 199 Ch.7-Dissolution of Stored... for Ca, 54% sample mass loss/day for Cu, and 220% sample mass loss/day for SO42". Typically for other metals, maximum dissolution rates were less than 2% sample mass loss/day. Table 7.4 shows the dissolution rate for several metals. These extremely high dissolution rates were sustained for only a brief period during the first several hours of the experiment, and in most cases, decreased by one order of magnitude by day 1. In the case of Ca, Cu, and SO42", release decreased by 2-3 orders of magnitude. These rates appear to indicate more mass loss than is present in the untreated sample, but upon careful examination of the data this is not the case. Table 7.4 Rates of release for Cu, Fe, SO42", and Zn during batch experiments from sample 9 in deionized water and citric acid solution buffered at pH 2.2. Rate of metal release (mg metal per g sample/day) ,L time elapsed Cu Fe SO 2-4 Zn (days) DDW lowpH DDW lowpH DDW lowpH DDW lowpH citric acid citric acid citric acid citric acid 0.04 6.1 4.7 3.3 32 1170 1220 0.05 0.05 0.08 1.3 2.2 0.8 59 1050 1280 0.01 0.02 0.25 0.1 0.2 0.1 18 176 140 0.01 0.02 1 0.01 0.02 0.02 10 10.3 9.6 n.d. n.d. 3 0.002 0.02 0.01 10 1.1 3.3 n.d. n.d. 9 0.001 0.01 n.d. 2.1 0.1 0.6 n.d. n.d. 20 0.001 0.01 n.d. 0.6 0.07 0.2 n.d. n.d. 41 n.d. n.d. n.d. 0.2 0.02 0.02 n.d. n.d. 100 n.d. n.d. n.d. 0.09 0.01 n.d. n.d. 153 n.d. n.d. n.d. 0.05 0.01 n.d. n.d. 1. Rate of metal released was calculated by determining the amount of metal released in the time between the collection of two samples. This gives an approximation of the rate metals were released up to a sampling time, assuming a constant dissolution rate for the period between the collection of the samples. e.g. rate of Fe released at day 3 (in DDW) rate = (amount of Fe released in DDW between day 1 to 3)/2 days 2. n.d. indicates metal released at a neglible rate. 200 Ch.7-Dissolution of Stored... Consider the release of SO4 " in deionized water from sample 9 (Table 7.4) and the following calculation: -calculate the amount of SO42" released for each sampling event then sum for all sampling events to determine the total loss during the experiment or CDM153 (1/24 hours per day)(l 170 mg SO42" loss per g of sample/day) + ((2-l)/24 hours per day)(1050 loss/day) + ((6-2)/24 hours per day)(176 loss/day) + ((24-6)/24 hours per day)(10.3 loss/day) + ((3-l)days)(l.l loss/day) + ((9-3) days)(0.1 loss/day) + ((20-9)days)(0.07 loss/day) + ((41-20) days)(0.02 loss/day) + ((100-41)days)(0.01 loss/day) + ((153-100) days)(0.01 loss/day) = 135 mg SO42" per g of sample or 135 000 mg SO42" per kg of sample or 13.5 % (by weight) released from sample after 153 days, which is the same as the value for CDM153 From this example, only 6 hours were required for dissolution of 90% of the S042"ultimately removed (total quantity of SO42" removed by day 153). Rapid release of metals (e.g. Ca, Cu, and SO42") is from the rapid dissolution of water soluble phases and displacement of exchangeable SO42" from amorphous coating on the mineral grains. These soluble phases may be secondary, tertiary (formed after samples were removed from the environment of the impoundment), or quaternary (formed by surficial oxidation during sample storage) minerals, thus some phases may have formed as a result of sample manipulation. Alpers et al. (1994) lists a variety of water soluble sulphates of Fe (II 201 Ch.7-Dissolution of Stored... and HI), Mg, Zn, Ca, Ni, Al , and Na. Oxidized Fe phases are an important component to the waste rock system because Fe oxides and hydroxides have the potential to scavenge metals from pore waters (Benjamin and Leckie, 1981) and soluble Fe sulphate minerals can be a source of acidity during wetting events (Cravotta, 1994). The following are examples of reactions with metastable phases leading to the generation of acidity, less soluble secondary products, and ionic species considered contaminants in water infiltrating a rock dump. melanterite Fe u(S0 4)'7H 20 + VA 0 2 — F e ( O H ) 3 + H 2 S 0 4 + 4.5 Ff 20 romerite Fe u Fe 2 m (S0 4 ) 4 -14H 2 0 2Fe(0H)3 + Fe 2 + + 4S04 2" + 6H + + 8H 2 0 Removal of highly soluble phases during the initial sampling events leaves phases with lower solubility resulting in a rapid decrease in the rate of metal release during subsequent events. The extremely high dissolution rates are quite striking and suggest that the vast majority of some soluble phases stored in the Gibraltar waste rock dump has the potential to be mobilized very quickly from the surface/near surface environment during infiltration events. The type of extracting solution affects dissolution behavior. Citric acid solutions are particularly effective for the dissolution of group B and C elements. Concentrations of group A elements did not show any difference in the various solutions. Differences between type 1 and type 2 samples are evident based on the batch experiments using distilled-deionized water. Comparing solutions from samples taken from the same trench (e.g. sample 2 vs. 9 or 11 vs. 16) , type 2 samples had greater acidity and 202 Ch.7-Dissolution of Stored... quantities of soluble materials dominantly composed of Ca, Fe, and SO42" as indicated by the lower pH and higher E C values. This trend was not observable when comparing type 1 and 2 samples from different trenches likely because of differences between the trenches. This trend occurred for DDW soluble Cu from samples collected in trench A and B, but not in C and D. An explanation for this may be related to aging of phases in areas of obsolete leaching which lead to preferential Cu retention, and in other areas, preferential Cu losses through leaching. Differences between type 1 and 2 were not as clear or masked in the other extracting solutions by the pH buffering, ionic strength, and greater dissolution due to their acidity. 203 Ch.7-Dissolution of Stored... geochemical modeling Ion activity, species distribution, and saturation index values were calculated using H2O solution chemistry data from wet-dry and batch experiments and are shown in Table 7.5 to Table 7.6 for selected samples. These results show a wide range of variation but some trends are evident in the data. Measured E h values were used to calculate Fe 3 + and Fe 2 + activities in the MINTEQA2 program. In the wet-dry experiment, calculated Fe 3 + and Fe 2 + activities from the samples used in the wet-dry experiment from 8 x 10"17 to 4 x 10"10 and 2 x 10"9 to 4 x 10 3 molal, respectively. In the batch experiment, Fe 3 + activities ranged from 9 x 10"13 to 5 x 10"10 and Fe 2 + activities ranged from 1 x 10"7 to 1 x 10"4. Blowes and Jambor (1990) found similar results for pore water collected from the vadose zone of mine tailings though they determined Fe 2 + analytically. The Fe 3 + concentrations determined using E h measurements were used to calculate the degree of saturation for ferric and ferrous oxyhydroxide and sulphate minerals. Metal species distribution from the wet-dry cycling experiments was dominated by free metal ions species (M n +), then metal-sulphate species (M-SO4 2 ). Generally, metal species were present as mono- and di-sulphate species during the initial cycles in the experiment, but after each leaching event, soluble SO42" levels decreased, and the proportion of M n + species increased. 204 Ch.7-Dissolution of Stored... Table 7.5 Distribution of selected aqueous species and saluration indices from selected samples from the 1st and 17th wet-dry cycle, calculated using MINTEQA2 1st wetting event 17welting event Type 1 Type 2 Type 1 Type 2 Parameter 16 33 9 27 Parameter 16 33 9 27 Distribution of aaueous species Distribution of aqueous species Iron (III) % Fe3* 1 2 2 Iron (III) % Fe3* 2 % FeOH2* 18 - 8 13 % FeOH2* 42 -% Fe(OH)2* 23 3 74 % Fe(OH)2* 55 % FeS04* 49 85 74 10 % FeSO„* 1 -% Fe(S04)2' 9 12 14 2 % Fe(S04)2~ Iron (II) %Fe2* 49 56 50 44 Iron (11) % Fe2* 99 % FeS04 51 44 50 56 % FeSO„ 1 -Aluminium % AI3* 10 14 10 8 Aluminium % Al3* % A1S04* 61 63 61 57 % A1S04* -% A1(S04)2" 29 23 29 34 % A1(S04)2" Calcium % Ca2* 45 52 46 40 Calcium % Ca2* 100 41 99 99 % CaS04° 55 48 54 60 % CaS04° 59 1 Copper %Cu2* 45 52 46 40 Copper % Cu2* 100 38 99 99 % CuSO40 55 48 55 60 % CuSO„° 55 1 -% Cu2(OH)22* - -• •• % Cu2(0H)22* 7 Sulfate % S042" 39 - 38 45 Sulfate % SO,2" 99 1 97 99 % HSCV 1 - 4 - % HS04" 3 -% CaS04° 57 35 55 49 % CaSO40 13 -% MgS04° -• 7 - 3 % MgS04° -% CuS04° 50 2 % CuS04° 82 -% A1S04* 1 1 - % A1S0„* % Al(SO„)2" - - 1 % Al(SO„)2- -% MnS04 -- 6 -• % MnS04 2 -Potassium % K* 96 97 96 95 Potassium % K* 100 95 100 100 % KSO, 4 3 4 5 % KS04" 5 •-Magnesium % Mg2* 48 55 49 43 Magnesium % Mg2* 99 _. % MgS04° 52 45 51 57 % MgS04° 1 •• Manganese % Mn2* 48 55 49 43 Manganese % Mn2* 44 99 99 % MnS04° 52 45 51 57 % MnS04° 56 1 Zinc % Zn2* 40 47 41 35 Zinc % Zn2* 100 36 98 99 % ZnS04° 57 51 56 61 % ZnS04° 60 2 % Zn(S04)22" 3 2 3 4 % Zn(S04)22" 4 -Saturation indices for solid phases Saturation indices for solid phases Al(OH)3 (amorphous) -4.6 -13 -6 -3.6 Al(OH)3 (amorphous) - -AIOHSO4 (jurbanite) -0.07 -0.89 -0.50 -0.21 AlOHSO, (jurbanite) -KA13(S04)2(0H)6 (alunite) -1.4 -10 -4.3 1.0 KA13(S04)2(0H)6 (alunite) . . -CaSCy2H20 (gypsum) 0.50 -6 0.49 0.47 CaS04-2H20 (gypsum) -5 1.3 -3.9 -4.0 CuO (tenorite) -5 -2.0 -6 -3.2 CuO (tenorite) -6 1.7 -7 -4.0 CuSCy5H20 (chalcanthite) -4.0 -23 -3.7 -3.2 CuS04-5H20 (chalcanthite) -9 -0.03 -8 -7 a-CuFe204 (cupric ferrite) -4.5 -8 -5 -2.8 a-CuFe204 (cupric ferrite) -10 --Fe(OH)3 (ferrihydrite) -5 -16 -5 -6 Fe(OH)3 (ferrihydrite) .7 -a-FeOOH (goethite) -1.0 -7 -1.1 -1.2 a-FeOOH (goethite) • -2.8 -g-FeOOH (lepidocrocite) -1.8 -8 -1.9 -2.0 g-FeOOH (lepidocrocite) -3.5 a-Fe203 (hematite) 2.9 -3.8 2.8 2.6 a-Fe^ O;, (hematite) -0.54 -KFe3(S04)2(0H)6 (jarosite) -7 -23 -6 -9 KFe3(S04)2(OH)6 (jarosite) -16 Si02 (amorphous) -1.8 13 -1.5 -1.1 Si02 (amorphous) -2.2 2.4 -1.8 -1.8 205 Ch.7-Dissolution of Stored.. Table 7.6 Distribution of selected aqueous species and saturation indices from experiment, calculated using MINTEQA2. day 0.04 Type 1 Type 2 Parameter 16 33 9 27 Distribution of aqueous species Iron (III) % Fe3* - 5 1 % FeOH2* 19 15 13 10 % Fe(OH)2* 33 3 10 85 % FeS04* 40 73 62 4 % Fe(SO„)2" 8 5 14 --Iron (11) % Fe2* 47 75 46 47 % FeS04 53 25 54 53 Aluminium % Al3* 9 30 8 9 % A1S04* 60 61 59 58 % Al(SO„)2" 31 10 33 31 % AlOH2* - - - 2 Calcium % Ca2* 43 72 42 43 % CaS04° 57 29 58 58 Copper % Cu2* 43 71 42 42 % CuS04° 57 29 59 58 Sulfate % S042" 46 62 44 42 % HS04' -- 10 2 --% CaSO40 50 11 51 53 % MgS04° -- 4 -- 3 % CuS04° - 12 - 2 % AI(S04)2' 1 • • % MnS04 1 Potassium %K* 96 99 96 96 % KS04" 4 1 5 4 Magnesium % Mg2* 46 74 45 46 % MgS04° 54 26 55 54 Manganese % Mn2* 46 74 45 46 % MnS04° 54 26 55 55 Zinc %Zn2* 38 68 37 38 % ZnS04° 58 31 60 59 % Zn(S04)22' 3 - 4 3 Saturation indices for solid phases Al(OH)-, (amorphous) -4.6 -7.8 -5.3 -3.1 A10HS04 (jurbanite) -0.01 -2.2 -0.3 -0.1 KAI3(S04)2(OH)6 (alunite) -0.9 -8.9 -2.5 1.8 CaS04-2H20 (gypsum) 0.4 -0.9 0.5 0.5 CuO (tenorite) -5.0 -5.2 -5.4 -2.8 CuS04-5H20 (chalcanthite) -4.1 -3.1 -3.8 -3.3 a-CuFe204 (cupric ferrite) -2.7 -9.6 -2.6 0.7 Fe(OH)3 (ferrihydrite) -4.6 -7.9 -4.3 -3.9 a-FeOOH (goethite) 0.3 -3.6 0.02 0.4 g-FeOOH (lepidocrocite) -1 -4.4 -0.8 -0.4 a-Fe203 (hematite) 4.4 -2.2 5 5.7 KFej(S04)2(OH)6 (jarosite) -5.4 -13 -3.2 -4.7 Si02 (amorphous) -2.3 -2.5 -2.1 -1.6 . samples from day 0.04 and 153 of the batch day 153 Type 1 Type 2 Parameter 16 33 9 27 Distribution of aqueous species Iron (III) % Fe3* - - 2 -% FeOH2* 18 8 41 16 % Fe(OH)2* 81 92 53 83 % FeS04* - - 3 -% Fe(S04)2' - - - -Iron (11) % Fe2* 100 96 97 99 % FeS04 - 4 3 1 Aluminium % Al3* 89 63 83 85 % A1S04* 2 16 14 5 % AlOH2* 8 16 2 9 AI(OH)2* - 5 - 1 Calcium % Ca2* 100 95 97 99 % CaS04° - 5 3 1 Copper % Cu2* 100 95 97 99 % CuS04° - 5 3 1 Sulfate % S042" 78 81 95 94 % HS04" - - 3 -% CaSO40 - - 2 4 % AIS04* 18 - - -% CuS04° - 18 - -% A1(S04)2" - - -% FeS04 2 - - -% MnS04 - - -Potassium %K* 100 100 100 100 Magnesium %Mg2* 100 95 97 99 % MgS04° 5 3 1 Manganese % Mn2* 100 95 97 99 % MnSO40 - 5 3 1 Zinc %Zn2* 100 95 96 99 % ZnSO„° - 6 4 1 % Zn(S04)22" Saturationjndices for solid phases Al(OH)3 (amorphous) -2.1 -3 -5.7 -3.6 AIOHS04 (jurbanite) -1.1 -1.7 -2.7 -2.2 KA13(S04)2(0H)6 (alunite) 0.5 -1.8 -7.4 -4.0 CaS04'2H20 (gypsum) -4.2 -3.8 -2.8 -3.0 CuO (tenorite) -5.1 -1.7 -5.7 -3.9 CuS04'5H20 (chalcanthite) -7.6 -3.9 -6.1 -5.9 a-CuFe204 (cupric ferrite) 1.4 1.1 -6.9 -1.6 Fe(OH)3 (ferrihydrite) -2.5 -4.3 -6.3 -4.6 a-FeOOH (goethite) 1.8 0.03 -2 -0.3 g-FeOOH (lepidocrocite) 1.1 -0.7 -2.8 -1 a-Fe203 (hematite) 8.7 5.1 1 4.5 KFe,(S04)2(OH)6 (jarosite) -4.5 -9.4 -13 -10.8 Si02 (amorphous) -0.01 -1.2 -0.3 -0.7 206 Ch.7-Dissolution of Stored... Ferric iron behaved somewhat differently than the other elements in that the free ferric ion species (Fe3+) never exceeded more than 5% of the total Fe (HI) concentration for all samples during the experiment, and instead, Fe-OH species increased after each leaching event. At pH > 3.5, the dominant Fe(UI) species was Fe(OH) 2 + , whereas at lower pH values, FeS0 4 + and FeOH2 + complexes became prominent. Metal species distribution in the batch experiment tends to reflect changes in either Eh-pH or S 0 4 " activity in the solutions. Generally, metals were found as monomers bound to mono-sulphate (M-SO4), except when SO42" concentration exceeded 150 mg/L in solution resulting in metal di-sulphate species. Initially high S0 4 2" activity from the dissolution of soluble sulphate phases results in the presence of metal sulphate ( M-(S0 4) n where n = the number of sulphate components ) species in solution. As the elapsed time increased, removal of soluble SO42" phases from the system leads to decreased SO42" activity and an increase in the proportion of uncomplexed free metal (M n +) ion and hydrolyzed species. The predominant species in the most acid solutions were M-(S042")n and the free metal ion species. Initially, the proportion of M-(S04 2")n species for a particular dissolved metal tended to be greater than 50%, and decreased rapidly with each solution sampling event and by day 1, had decreased to < 10% of the speciation in samples of type 1. In type 2 samples, except for sample 31, M-(S042")n speciation remained high (in some cases > 50%) for solutions collected up to day 1, then decreased slowly to less than 10% in solutions collected later. The predominance of AI-SO4, Fe-SC^, A l 3 + and Fe 3 + in mining environments has been shown by others (Monterroso et al., 1994; Alvarez et al, 1993). 207 Ch.7-Dissolution of Stored... As pH increased in the solutions collected from the batch experiment, SO42" and OH" competition increased for free metal ion species, resulting in a rise in the proportion of M -(OH)n and a decrease in M-(S04)n species (Figure 7.7 and Figure 7.8). The different Fe-(OH)n and Al-(OH) n species appear to be highly dependent on pH and the total Fe-(OH)n and Al-(OH) n species increased with acidity. Ferric iron speciation at values of pH > 3.5 is dominated by the di-hydroxylized Fe 3 + species, while at lower pH values the dominant species is the mono-hydroxylized species. Levels of S0 4 2* were unaffected by pH. Saturation data were plotted to examine mineral solubility relationships responsible for the control of metal ion concentrations in the solutions. Solutions supersaturated (SI is +) with respect to a solid phase cannot dissolve the phase but can potentially be precipitated as a product under appropriate conditions. For some minerals, precipitation under surface temperatures and pressures is not likely or very slow because of kinetic constraints, which results in supersaturation with respect to those minerals. Unsaturated solutions can indicate the dissolution of a solid phase if it exists in the system. Data for the different sample types generally indicated similar solubility control processes. A l equilibria in acid mine waters has been studied extensively and a number of mineral phases have been identified as possible solubility controls (Monterroso et al, 1994; Karathanasis et al, 1988; Nordstrom and Ball, 1986; Sullivan et al, 1988; Nordstrom, 1982). Mineral phases which have been considered for the control of Al solubility were: amorphous Al(OH) 3, basaluminite Al 4(OH)ioS04'5H 20, jurbanite AIOHSO4, alunite KA1 3(S04)2(0H) 6, gibbsite Al(OH) 3 , and diaspore AIO(OH). 208 Ch.7-Dissolution of Stored.. Ch.7-Dissolution of Stored.. Ch.7-Dissolution of Stored... Al concentrations in leachates collected from the wet-dry cycling experiments generally were saturated or slightly unsaturated with respect to jurbanite and diaspore and unsaturated with respect to amorphous Al(OH) 3, basaluminite, alunite, and gibbsite. No observable change was obvious with increases in the value of pH 3 5.8. The least stable phase was basaluminite. All leachates collected in cycles 1-4 were at saturation with jurbanite, and leachates collected from sample 27 were at saturation with alunite and diaspore. All leachates collected after cycle 4 were generally unsaturated with respect to all Al phases. As summarized in Figure 7.9, results from the batch experiment show that the more acidic solutions were unsaturated with respect to alunite, basaluminite, amorphous Al(OH)3, gibbsite, but as pH increased these phases approached equilibrium. Solutions were slightly unsaturated or at equilibrium with, alunite, gibbsite, and diaspore from pH 3.7 - 5, and a basic jurbanite-type phase for the entire pH range of the samples. Solutions approached equilibrium with an amorphous form of Al(OH) 3 when the pH value is > 5. The least stable phase was basaluminite which was significantly undersaturated for all pH values < 4.5. Solutions collected during the first 6 hours of the experiment were saturated with respect to jurbanite (except from sample 33). Solutions collected at all equilibration times were at saturation or slightly supersaturated with diaspore, except from samples 9, 11, and 33. Solutions from sample 33 were not at saturation with any Al containing phase. These results suggest A l 3 + activity may be subjected to several possible control mechanisms depending on pH values. 211 Ch.7-Dissolution of Stored.. • jurb-MOHS04 + A14(OH)10SO4 x gibbsite 2.5 3.5 4.5 solution pH 5.5 Saturation indexes were calculated using data from the batch experiments. Mineral phases in equilibrium are located between the two orange lines. Figure 7.9 Saturation indexes vs. pH for different Al mineral phases based on thermodynamic data from the geochemical model MINTEQA2 (1991). 212 Ch.7-Dissolution of Stored... A l 3 + activity seems to be controlled by jurbanite and gibbsite (or diaspore) at pH < 5 which agrees with results from other researches studying acid mine systems (Monterroso et al, 1994; Karathanasis et al, 1988; Nordstrom and Ball, 1986). Winland et al. (1991) indicate activity of Al in acid mine solutions with pH < 6 is consistent with the stoichiometry of jurbanite. Solution saturation with respect to alunite in the same solutions as jurbanite and gibbsite is likely possible as there is some overlap in their stability regions in naturally occurring environments. Nordstrom (1982) suggests alunite is stable between jurbanite and gibbsite (diaspore) in the pH range 3.3 - 5.7 for the range of 10"4 - 10"2 M sulphate. Solutions approached equilibrium with amorphous Al(OFf)3 phase at pH 5 which agrees with other studies that have determined that for pH greater than 4.6 to 5, an amorphous Al(OH)3 phase controls A l 3 + (Monterroso et al, 1994; Nordstrom and Ball, 1986). Karathanasis et al. (1988) suggest the change occurring between pH 4.5 -5 is the boundary for A l 3 + control between basic aluminum sulphates and aluminosilicates. A l 3 + activity in solutions with pH < 5 seems to be controlled by jurbanite, alunite, and gibbsite (diaspore), depending on the SO4 " activity in the solution. In solutions with pH > 5, an amorphous Al(OH)3 controls the Al activity. Studies examining secondary Fe phases in acid mine waters have suggested the presence of the following Fe minerals in the system: FeOHSCu (Sullivan et al, 1988), a-FeOOH [goethite] (Levy et al, 1997), KFe 3(S0 4)2(OH)6 [K-jarosite] (Levy et al, 1997), y-FeOOH [lepidocrocite] (Bigham, 1994), F e 5 O H 8 » 4 H 2 0 ferrihydrite (Bigham, 1994), FeSCWF^O melanterite (Monterroso et al, 1994). Mineral phases that were evaluated for 213 Ch.7-Dissolution of Stored... saturation in these solutions were ferrihydrite, goethite, melanterite, lepidocrocite, K-jarosite, a-Fe 2 0 3 hematite, F e O F e 2 0 3 magnetite; and a-CuFe 2 0 4 cupric ferrite. A newly named mineral, schwertmannite FegOg^Ff^SCM, should also be included in the above list, but there is little thermodynamic data available and thus could not be incorporated into the MTNTEQA2 model. Bigham (1994) indicates this new mineral seems to be the most common mineral associated with ochreous precipitates in acidic mine drainage. Dissolved Fe in leachates collected from wet-dry cycling experiments were at saturation with respect to hematite for the pH range in all the solutions, except in sample 33. Solutions collected with pH > 5 were at equilibrium with ferrihydrite, jarosite, and lepidocrocite . Solutions were slightly unsaturated at pH < 5 and slightly supersaturated at higher pH values with goethite. Solutions collected from sample 33 were consistently supersaturated with respect to hematite. In type 1 samples, solutions at lower pH were saturated with respect to hematite. As pH increased above 5, solutions were saturated to supersaturated with respect to ferrihydrite and hematite. All solutions with pH > 5 were from sample 33. Results indicate possible phases controlling Fe solubility in solutions collected from the batch experiments were goethite, lepidocrocite, cupric ferrite, and magnetite (Figure 7.10). The most stable phase in these solutions tended to be hematite. Solutions collected were generally unsaturated with respect to ferrihydrite, melanterite, K-jarosite, and many other Fe(n)-(S04)n*mH20 phases for all samples. 214 Ch.7-Dissolution of Stored.. 14 12 10 8 JS A 5 I 4 fa z-2 -4 -6 -8 -10 -• ferrihyc A goethiti x hematil - melantt Irite e :rite v X X \ X J* x * * x * X X, 4 J X X X ^ XX*X X f xX x x^ * X X x x x X A X A • — ^ 3 A " * A ' * ' " • s-m ........ 2 u 1) fa 2.5 3.5 solution pH 4.5 5.5 Saturation indexes were calculated using data from the batch experiments. Mineral phases in equilibrium are located between the two orange lines. Figure 7.10 Saturation indexes vs. pH for different Fe mineral phases based on thermodynamic data from the geochemical model MINTEQA2 (1991). 215 Ch.7-Dissolution of Stored... Solutions were saturated and in apparent equilibrium with goethite and lepidocrocite for solution pH values up to 4.7, and with cupric ferrite and magnetite for solutions with values of pH 4 - 4.7. Solutions with pH > 4.7 appear to be at equilibrium with ferrihydrite, although there were few data points. Langmuir and Whittemore (1971) have suggested Fe(OH)3 and poorly crystalline goethite are the first ferric phases to precipitate in streams impacted by acid mine waters, but will transform with time into the more stable phases, crystalline goethite and lepidocrocite. Goethite usually accompanies lepidocrocite (Langmuir and Whittemore, 1971) and has been found in pore waters from mine tailings with saturation indexes between +1 and -1 (Blowes and Jambor, 1990). Lepidocrocite is the major initial product of the oxidation and precipitation of ferrous iron bearing solutions, although the presence of other metal ions plays a role in determining crystallinity and stability towards goethite (Williams, 1990). Transformation from lepidocrocite to goethite in surface environments occurs on a pedogenic time scale (i.e. 103 years) (Schwertmann and Fitzpatrick, 1992). Goethite and hematite have similar solubility (Ksp hematite = 10~43 - 10"42, Ksp goethite = 10"44 - 10"43) and stability, but slow kinetic rates, due to either slow dissolution of the metastable form or hampered nucleation of the stable phase by contaminating compounds, which lead to the formation of poorly crystalline, metastable phases such as ferrihydrite, lepidocrocite and microcrystalline goethite at surficial temperatures (Bigham, 1994; Schwertmann and Fitzpatrick, 1992; Schwertmann and Taylor, 1989). Ferrihydrite is likely to form in slightly acid to alkaline solutions with high levels of dissolved Fe (Bigham, 1994). Bigham et al. (1996) identified mixtures of schwertmannite and goethite in precipitates collected from water with pH 2.8 -216 Ch.7-Dissolution of Stored... 4.5. Evidence supports the notion that Fe oxides and oxyhydroxides control Fe solubility, the same can not be stated for cupric ferrite and magnetite. Cupric ferrite has not been implicated in mine waste materials as a possible control of Fe or Cu levels in mine waters and will be discussed in greater detail in conjunction with Cu. Magnetite in waste rock is likely to be lithogenic rather than pedogenic in origin. Its presence likely explains the magnetic properties observed in the sand fraction of waste rock samples. Although it can be formed easily under ambient conditions, it has never been identified as a secondary mineral in soils (Schwertmann and Taylor, 1989). Dissolved Fe activity in these solutions appears to be controlled by a mixture of goethite, hematite, and lepidocrocite, and at values of pH > 4 with higher C u 2 + activity, possibly cupric ferrite. The coexistence of goethite and hematite is widely observed in many subtropical and tropical soils and reflects their similar thermodynamic stability (Schwertmann and Taylor, 1989). When pH increases above 5, ferrihydrite may play a role. Ferrihydrite is likely formed by rapid oxidation and hydrolysis of Fe 2 + in the presence of silicate and is widespread and characteristic of young Fe-oxide accumulations (Schwertmann and Taylor, 1989). Secondary copper phases in waste rock and Cu equilibria have not been the subject of extensive study like Al or Fe. Secondary Cu phases identified in mining environments and natural bedrock where supergene enrichment has occurred include: CuO [tenorite], Cu 3 S0 4 (OH) 4 [antlerite], Cu 3(C0 3)2(OH)2 [azurite], Cu 4(S0 4)(OH) 6 [brochantite], 217 Ch.7-Dissolution of Stored... Cu 4(S0 4)(OH) 6'2H 20 [langite], C u S 0 4 » 7 H 2 0 [chalcanthite], and C u 4 ( S 0 4 ) ( O H ) 6 » H 2 0 posnjakite (Bigham, 1994; Stromberg etal., 1994; Bowell, 1992; Williams, 1990). Secondary copper phases considered here were: Cu(OH)2, tenorite, chalcanthite, cupric ferrite, brochantite, langite, and antlerite. Results are presented in the bottom portion of Figure 7.11. Data points for brochantite, langite, and antlerite were omitted to prevent clutter, but they fall on or near values for chalcanthite. Chalcanthite has been identified as a post-mine leaching product of the ores at Gibraltar (Bysouth et al., 1993). Cu solubility appears to be controlled by two mineral phases in these solutions depending on solution pH. Solutions from (1) the wet-dry cycling experiment were saturated with respect to chalcanthite for pH > 4.7, and unsaturated to all phases in more acidic solutions, and (2) the batch experiments were in apparent equilibrium with cupric ferrite for values of pH 4 - 4.7, and slightly unsaturated to saturated with tenorite for pH > 4.7. Cu(OH) 2 and all other basic Cu-sulphate phases approached equilibrium as pH increased and Cu solubility decreases. Langite was the least stable phase in these solutions and only approached equilibrium in some solutions collected from sample 33. This sample was collected from an area of the waste rock dump which had never been leached with acid. Using stability constant data, Williams (1990) shows in a stability field diagram that chalcanthite is the most stable phase under acidic pFf's, and as pH increases, the stable phases change from antlerite (metastable), brochantite, and under the least acidic conditions, tenorite. 218 Ch.7-Dissolution of Stored... • Cu(OH)2 A chalcanthite 1 * * A A 2.5 3.5 4.5 5.5 2.5 • tenorite x cupric ferrite 3.5 4.5 solution pH 5.5 Saturation indexes were calculated using data from the batch experiments. Mineral phases in equilibrium are located between the two orange lines. Figure 7.11 Saturation indexes vs. pH for different Cu mineral phases based on thermodynamic data from the geochemical model MINTEQA2 (1991). 219 Ch.7-Dissolution of Stored... This seems to contradict the results shown in Figure 7.11, however in the gossan forming environment, incorporation of Fe(JH) into basic Cu sulphate compounds can lower their solubility (Thornber and Wildman, 1984). Strdmberg et al. (1994) obtained effluents near saturation with respect to a suite of Cu-sulphate and Cu-OH minerals, including tenorite (SI = -0.35 ± 0.22). In their calculations, cupric ferrite was supersaturated (SI = 16 ± 0.52). As mentioned earlier, cupric ferrite has not been suggested as a possible control of Cu or Fe in mine waters in other studies. This may be due to the tendency to model Al and Fe solubility in acid mine waters. Although the intensity and physical nature of mine waste rock and soils are different, similar weathering processes occur and under the appropriate conditions, weathering products in soils may be similar to those in mine waste. Lindsay (1979) states that the minerals governing the solubility of C u 2 + in soils are not know, but suggests that soil-Cu may be cupric ferrite. Cupric ferrite has a solubility product (Ksp = 10" 5 0 1 2 ; Ball and Nordstrom, 1991) much lower than for the Cu phases mentioned above. Figure 7.12 shows the degree of saturation in solutions from the batch experiment with respect to several Si minerals. The solutions are at or near equilibrium with various SiC»2 phases (quartz, amorphous SiC>2, chalcedony-cryptocrystalline SiC»2) for the entire pH range (2.8 - 5.8). The least stable phase was muscovite, but it approached saturation at pH > 4.5. Kaolinite was at equilibrium between pH 3.8 - 4.5, and was unsaturated at lower pH and supersaturated at higher pH. Similar results were observed in the wet-dry cycling experiments. 220 Ch.7-Dissolution of Stored... a " 5 ca -2 --3 • quart ASi02 Z (am,gl) — -• 1 A ' A1 • • mi • " A Si*.-:- m • A m , • A A A I ^ A * A * ^ A * ^ 4 A m A A A 2.5 3.5 4.5 5.5 £ c 1 V) a —• 5 3 1 -1 -3 -5 -7 -9 -11 -13 -15 2.5 -X X X X X x > <_ * y X x X X * X X ; * x x IC * X X x X X **x* x "X" * * * *» • X X • x x X : x = X — <* xx, »?V X* x * * 5 x xx <* V 1 j r r X x X X X X • chal xkao mu: • cedony inite covite 3.5 4.5 5.5 solution pH Saturation indexes were calculated using data from the batch experiments. Mineral phases in equilibrium are located between the two orange lines. Figure 7.12 Saturation indexes vs. pH for different Si mineral phases based on thermodynamic data from the geochemical model MINTEQA2 (1991). 221 Ch.7-Dissolution of Stored... Of the other elements analyzed (Ca, K, Mg, Mn, Mo, Na, Ni, Pb, Zn), solutions were not at equilibrium with any discrete phases likely to control their concentrations in solution. The concentrations of these metals are likely controlled by adsorption or coprecipitation reactions. Research has shown, (1) coprecipitation reactions during Fe(OH)3 precipitation can accumulate metals such as Ni, Co, Cu, Pb, and Zn, from solution (Thornber, 1983) and (2) adsorption/coprecipitation with Fe(OH)3 can be used to remove Cd, Cu, Zn, As, and Se from wastewater streams (Leckie et al., 1980). A recent study characterizing goethite and lepidocrocite precipitates formed from mine leach contaminated groundwater found that metals were retained by either isomorphic substitution for Fe in goethite or adsorption to oxide surfaces (Herbert, 1995). Similar mechanisms probably play an important role in controlling the concentrations of metals in the Gibraltar rock dumps. The variations observed between (trench A to D) and within the different trenches (type 1 vs. type 2) appear to be controlled by the pH in the solutions, which suggests that the retained secondary weathering products control metal solubility. The retained secondary products tended to buffer solution pH during these experiments to values near paste pH values (see Chapter 4), although there were slight fluctuations. Sample type did not appear to influence the variations observed, however, since weathering/leaching history had a strong influence on the amount and type of secondary weathering product, this variable appears to have a greater effect on the phases controlling solubility. This means that samples which generated solutions with similar pH, regardless of sampling location, tended to have similar mineral solubility control. Thus, control of mineral solubility in samples from trench A and 222 Ch.7-Dissolution of Stored... B are more than from trench C and D. Samples from within a trench exhibiting different buffered pH, are likely to have different phases controlling mineral solubility. In this case, phases controlling mineral solubility will be a function of pH and sulphate levels, as described in the previous discussion. differences between wet-dry cycling and batch experiment The two procedures used to evaluate dissolution are preliminary but allowed for an evaluation of the potential for metals to be solubilized under different conditions. Comparisons can only be made between the distilled-deionized water (DDW) solutions. Comparison of total metals dissolved from each sample generally indicates batch experiments removed greater quantities of metals than the wet-dry experiments even though both experiments seemed to be at a steady-state with respect to cumulative metal release (with the exception of Si) (Table 7.7). Longer solution contact times likely lead to greater dissolution of the various phases. Batch experiments were able to show the dissolution of metastable phases, but wet-dry cycling experiments did not show this occurring for the number of allowed cycles. There were a few differences from the geochemical modeling of the two procedures. Controls for Cu and Fe solubility were generally the same except for some wet-dry cycling solutions that were at equilibrium with hematite and chalcanthite. In the case of the former, this was likely due to the higher pH values obtained from wet-dry cycling. 223 Ch.7-Dissolution of Stored. \o o\ c n 8 8 8 8 d o d o \6 ON 11 vq m i n c~ CN - H O ) 8 8 8 8 d o d d I s 00 ( N f N f N O —i O O d d d o » 0 J^- r N o O O ~t d o ' d o " OO CO _ i o -H ( N f N 8 8 o o 8 8 d d •* t> r N c n d d o\ 00 CN - f l-d d f N i 3 ^ d 11 CN vo o o d d O d d CN oi d d v o o o CN c n d d -a 73 —I CN o o d d c~i vn . d 1 - 1 CN CN 8 m f N i n f N m c n ^ 8 8 8 8 8 8 8 8 8 d d o" O d d d d d d —( CN 8 8 d d CN cn o o d d ~-< i n c-~ oo vo o o d d -43* -g 224 Ch.7-Dissolution of Stored... The higher pH values may indicate the wetting time was not sufficient for the dissolution of some "reserve" acidity, thus resulting in less acidic pH values. In the latter case, crystallites of Cu-SO-4 may be forming during the drying phase of the wet-dry cycling experiment. 225 Ch.7-Dissolution of Stored... 7.4 Conclusions Large differences were found with regard to the solution composition from waste rock materials collected from a range of environments and field treatments. Two dissolution procedures were used to evaluate the potential for metal leaching from waste rock samples collected from the Gibraltar mine site. Dissolution in the wet-dry cycling procedure is useful to examine metal leaching from areas of a rock dump where moisture is quick to evaporate (e.g. surfaces exposed to solar energy and convection) or drain, leading to unsaturated conditions. Batch experiments may be related to areas of a rock dump were saturation may occur for longer duration such as in layers of finer material in rock dumps where capillary water may be held strongly, wet seasons when rainfall may occur for longer periods of time resulting in perched water tables and saturated zones, and waste rock material designated for long term aqueous deposition. Morphologically different areas in a dump may indicate areas of preferential accumulation and dissolution of oxidized residual products. Samples with low Her values (i.e. red samples) tended to have higher levels of acidity, total dissolved solids (high EC), and water soluble Ca, Fe, and S042" indicating areas of preferential accumulation and dissolution under certain conditions. Dissolution of Cu was higher in low Her samples collected from abandoned leaching areas . The higher acidity and metals may be a relic of sulphide oxidation or may indicate active sulphide oxidation in this region. Thus zones in the rock dump which are morphologically different (low Her) are potential "hot spots" for metal leaching and the generation of acidity. 226 Ch.7-Dissolution of Stored... Metal dissolution from the waste rock samples was rapid and near complete for many samples in 3-5 wetting events or 3-9 days of saturation, except for Si which entered solution at a constant rate (in both procedures). Dissolution rates were highest in the samples collected from the "hot spots". Metals most susceptible to enter solution were S as SO4 2 ", Ca, Cu, Si, Al , and Mg. Extremely high levels of soluble SO4 2 " suggest most metals were retained in sulphate forms. Metal dissolution was most effective using chelating acid solutions. Generally, the citrate solutions buffered to either pH 2.3 or 4.6 were most effective at dissolving metals and DDW was least effective. This suggests that reclamation using soil covers may be problematic as the biotic component of the soil becomes more significant with time. Geochemical modeling indicates several phases may be controlling metal levels in solutions. Dissolved A l 3 + activity in solutions may have at least three possible control mechanisms, depending on solution acidity and SO42" activity. Control mechanisms when pH is less than 5 seems to be controlled by jurbanite, alunite, and gibbsite (diaspore), depending on the SO42" activity in the solution and an amorphous Al(OH)3 in solutions with pH > 5. Dissolved Fe activity appeared to be controlled by a mixture of goethite, hematite, and lepidocrocite, and at values of pH > 4 with higher C u 2 + activity, possibly cupric ferrite. When pH increases above 5, ferrihydrite may play a role. Cu solubility appeared to be controlled by two mineral phases depending on solution pH. In acidic solutions (pH 4 - 4.7) the only mineral phase in apparent equilibrium was cupric ferrite. As pH increased above pH 4.7, control corresponded with chalcanthite or 227 Ch.7-Dissolution of Stored... tenorite, depending on SO4 2 " activity. Dissolved Si was controlled by various S i 0 2 phases (quartz, amorphous SiO-2, chalcedony-cryptocrystalline Si02). Other metals were not at equilibrium with any discrete phases likely to control their concentrations in solution. 228 Ch.8-Summary and Conclusions 8. Summary and Conclusions This body of work involved the characterization of oxidized residuals or secondary weathering products stored in mine waste rock from the Gibraltar Mine. This project was initiated as a result of the lack of information on the importance of stored weathering products and the re-dissolution of oxidized residuals in the contaminant loading of seepage from waste rock dumps. The research involved three components; (1) general mineralogical and chemical characterization of waste rock samples, (2) characterization and partitioning of oxidized residuals using selective dissolution analyses and sequential dissolution analyses, and (3) investigation of the re-dissolution of metals from stored weathering products using wet-dry cycling and batch studies. Several general conclusions can be drawn from the work. Sample colour has been shown to be a useful tool to identify metal accumulation in waste rock and can be used to stratify waste rock samples for studies of secondary weathering products. In the Gibraltar rock dump, zones of metal accumulation are distinguishable from other areas by using Munsell soil colour. Secondary Fe phases controlled the pigmentation of the oxidized waste rock. Stored weathering products play an important role in the attenuation of metals released by sulphide oxidation and the geochemistry of waste rock dumps leading to metals laden drainage. In some cases, retained weathering products were a significant proportion of the total mass of a metal from a sample. The importance of pH on metal precipitation/retained weathering products is well documented in the literature, but a unique 229 Ch.8-Summary and Conclusions aspect at this site is the role of sulphate. Sulphide oxidation and sulphuric acid leaching leads to the formation of a variety of secondary weathering products, some of which are retained on rock surfaces. At the time of sampling, the products appear to be a mixture of secondary Fe oxides (hematite, goethite, possibly lepidocrocite), oxyhydroxysulphates (jarosites and schwertmannite), sulphates (gypsum, chalcanthite, langite). Several of these phases (and others not identified) are likely to contribute to the control of the solubility of Fe, Al, and Cu. Stored weathering products have different reactivity and solubility leading to groups or "pools" of metals which have similar behavior. Distribution of metals in the various "pools" changes with advanced weathering and time. Some metals tended to accumulate in a soluble form (Cu, Ca, Mg, Na, Zn), while others (Al, Fe, K, Si) formed metastable products. Secondary products tended to increase in meta-stability and decrease in solubility going from areas of natural weathering active acid leach weathering post-leach weathering. The products of weathering are partially removed (by acid leaching and atmospheric water), some have been sorbed, some occluded, some pseudomorphed into existing minerals/crystals, and some have recombined resulting in the authigenic formation of secondary minerals. This research has several implications for the management of the waste rock at the Gibraltar mine and other similar sites. Site management must take into account the potential for the release of stored metals due to environmental changes caused by reclamation activities. Two possible approaches to reduce the impact of accumulated weathering products could focus on, ( 1 ) reducing the flow of water through the rock dump, thus minimizing the dissolution and removal of secondary products, and ( 2 ) intentional re-230 Ch.8-Sumrnary and Conclusions handling of the waste rock with the aim of increasing metal mobilization caused by the mixing of the accumulated weathering products and the alteration of existing water flow patterns, and the collection of the resulting waters. If a drainage collection system is in place, removal of secondary weathering products can be enhanced prior to reclamation, by irrigating the dump surface with excessive amounts of water, or a combination of a weak organic acid (e.g. acetic or citric acid) followed by surplus amounts of water. This may be possible by using existing leaching system or spraying from trucks with attached sprayers. Irrigation with excessive amounts of water and/or weak acid may stimulate the removal of greater quantities of accumulated weathering products through dissolution and metal chelation. In areas along the flow path, soluble products will be rapidly mobilized, while metastable products will undergo dissolution more slowly. Irrigation to remove weathering products may be possible using the existing acid leaching system. Another concern is for the long-term stability of waste rock which has been reclaimed and has a layer of soil at the surface supporting vegetation and biota. The short-term concern is that moisture moving downwards through the soil and entering the waste rock will dissolve soluble weathering products, potentially producing metals laden drainage. The long-term concerns focus on the dissolution of metastable weathering products. The biotic activity in the surface soil layer will eventually lead to the accumulation of organic material and increase the biotic activity. Release of organic acids from organic matter decomposition, microorganisms, and fungi may enhance metal dissolution from metastable weathering 231 Ch.8-Summary and Conclusions products. Thus, dissolution of metals may occur for a long period of time because of the accumulation of metals in metastable phases. Reclamation experts must be made aware of the potential for metal leaching. This research has made the following contributions to the study of metal leaching and weathering of mine waste: (1) The reaction used to describe acid rock drainage indicates the product of Fe 3 + hydrolysis is Fe(OH)3, however, the results of this research clearly indicate there are a variety of ferric iron products formed from incomplete hydrolysis. This is very important when interpreting acid-base accounting data and determining the net acid and neutralization potential for a waste rock sample. (2) The research has highlighted the importance of the fine fraction for kinetic processes in waste rock. The results are more kinetically biased than traditional mine waste testing methods such as humidity cell tests for whole samples. (3) This study has shown that fine earth fraction colour is a valuable sampling tool to stratify waste rock samples collected from mine sites. The method involves a correlation between the presence of oxidized Fe phases, as a pigmenting agent, and colour of the silt+clay fraction. Preliminary results indicate a strong relationship between colour and Fe, however, a correlation may also exist between colour/extractable Fe and other extractable metals. Some recommendations for further research based on this work are: • the relationship between colour and secondary weathering products needs to be verified 232 Ch.8-Summary and Conclusions with waste rock from a wider range of weathering conditions and/or ages • develop the methology to calibrate and use photoelectric colourimeters and spectrophotometers in the field • define a group of reference materials, representative of mined materials, to be made available to researchers studying metal leaching and mining issues 233 Literature Cited 9. Literature Cited Al, T.A., D.W. Blowes and J.L. Jambor. 1994. Chapter 12: A Geochemical Study of the Main Tailings Impoundment at the Falconbridge Limited , Kidd Creek Division Metallurgical Site, Timmons, Ontario. Pp. 333-364. In: J.L. Jambor and D.W. Blowes (eds.) Environmental Geochemistry of Sulphide Mine-Wastes, Short Course Handbook. Vol.22. Mineralogical Association of Canada. Waterloo, Ontario, Canada. Allison, J.D., D.S. Brown and K.J. Novo-Gradac. 1991. MINTEQA2/PRODEFA2, A geochemical assessment model for environmental systems: version 3.0 User's Manual. US EPA, Athens, Georgia. EPA/600/3-91/021. Alpers, C.N., D.W. Blowes, D.K. Nordstrom and J.L. Jambor. 1994. Secondary minerals and acid mine-water chemistry. Pp. 247- 270. In: J.L. Jambor and D.W. Blowes (eds.), Environmental Geochemistry of Sulphide Mine-Wastes, Short Course Handbook, Mineralogical Association of Canada. Vol.22, Waterloo, Ontario Alpers, C.N. and G.H. Brimhall. 1989. Paleohydrologic evolution and geochemical dynamics of cumulative supergene metal enrichment at La Escondida, Atacama Desert, Northern Chile. Economic Geology. 84(2):229-255. Alva, A.K., M.E. Sumner and W.P. Miller. 1991. Relationship between ionic strength and electrical conductivitiy for soil solutions. Soil Science. 152(4):239-242. Alvarez, E. , A. P rez and R. Calvo. 1993. Aluminum speciation in surface waters and soil solutions in areas of sulphide mineralization in Galicia (NW Spain). Science of the Total Environment. 133:17-37. Arand, R.R. and R.J. Gilkes. 1984. Mineralogical and chemical properties of weathered magnetite grains from lateritic saprolite. Journal of Soil Science. 35:559-567. Baes, C.F. Jr. and R.E. Mesmer. 1976. The Hydrolysis of Cations. John Wiley and Sons Inc. Ball, J.W. and D. K. Nordstrom. 1991. User's Manual for WATEQ4F. with Revised Thermodynamic Database and Test Cases for Calculating Speciation of Major, Trace, and Redox Elements in Natural Waters. U.S. Geological Survey. Open-File Report 91-183. Menlo Park, California. Bartlett, R.W. 1992. Leaching and Fluid Recovery of Materials. Gordon and Breach Science Publishers. Philadelphia, Pennsylvania. 234 Literature Cited Bayless, E.R., and G.A. Olyphant. 1993. Acid-generating salts and their relationship to the chemistry of groundwater and storm runoff at an abandoned mine site in southwestern Indiana, U.S.A. Journal of Contaminant Hydrology. 12:313-328. Bell, A.V., Riley, M.D. and Yanful, E.K. 1994. Evaluation of a composite soil cover to control acid waste rock pile drainage. In: International Land Reclamation and Mine Drainage Conference and Third International Conference on the Abatement of Acid Drainage, Vol. 2, April 24-29, 1994, Pittsburgh, pp. 270-278. Bigham, J.M., U. Schwertmann, S.J. Traina, R.L. Winland and M . Wolf. 1996. Schwertmannite and the chemical modeling of iron in acid sulphate waters. Geochimica et Cosmochimica Acta. 60(12):2111-2121. Bigham, J. 1994. Chapter 4: Mineralogy of Ochre Deposits Formed by Sulphide Oxidation. Pp. 103-132. In: J.L. Jambor and D.W. Blowes (eds.), Environmental Geochemistry of Sulphide Mine-Wastes, Short Course Handbook. Vol.22. Mineralogical Association of Canada. Waterloo, Ontario, Canada. Bigham, J.M. and E.J. Ciolksz. 1993. Soil Colour, Proceeding of a symposium sponsored by Divisions S-5 and S-9 of the Soil Science Society of America in San Antonio, Texas. October 21-26, 1990. SSSA Special Publication 31, Soil Science Society of America, Inc., Madison, Wisconsin, USA. Bigham, J.M., U. Schwertmann and L. Carlson. 1992. Mineralogy of precipitates formed by the biogeochemical oxidation of Fe(U) in mine drainage. Pp. 219-232. In: H.C.W. Skinner and R.W. Fitzpatrick (eds.), Biomineralization Processes of Iron and Manganese -Modern and Ancient Environments. Catena Verlag, Germany. Bigham, J.M., U. Schwertmann, L. Carlson and E. Murad. 1990. A poorly crystallized oxyhydroxysulphate of iron formed by bacterial oxidation of Fe(U) in acid mine waters. Geochemica et Cosmochimica Acta. 54:2743-2758. Birkeland, P.W. 1984. Soils and Geomorphology. Oxford University Press. New York. Blanchard, R. 1968. Interpretation of Leached Outcrops. Nevada Bureau of Mines, Bulletin 66. Blowes, D.W., E.J. Reardon, J.L. Jambor and J.A. Cherry. 1991. The formation of potential importance of cemented layers in inactive sulphide mine tailings. Geochimica et Cosmochimica Acta. 55:965-978. Blowes, D.W. and J.L. Jambor. 1990. The pore-water geochemistry and the mineralogy of the vadose zone of sulphide tailings, Waite Amulet, Quebec, Canada. Applied Geochemistry. 5:327-346. 235 Literature Cited Bohn, H., B. McNeal and G. O'Connor. 1985. Soil Chemistry. John Wiley & Sons, Inc. New York. Borggaard, O.K. 1988. Chapter 5: Phase Identification by Selective Dissolution Techniques. Pp. 83-98. In: J.W.Stucki, B.A. Goodman and U. Schwertmann (eds.), Iron in Soils and Clay Minerals. NATO ASI Series, Proceeding of the NATO Advanced Study Institute in Soils and Clay Minerals, West Germany, July 1-3, 1985. Bowell, R.J. 1992. Supergene copper mineral assemblages at Botallack, St Just, Cornwall. Journal of the Russell Society. 4(2):45-53. Brady, N.C. 1990. The Nature and Property of Soils- lO^Ed. MacMillan Publishing Co. New York, New York. Brady, K.S., J.M. Bigham, W.F. Jaynes and T.J. Logan. 1986. Influence of sulphate on Fe-oxide formation: comparisons with a stream receiving acid mine drainage. Clays and Clay Minerals. 34(3):266-274. Breeman, N. van. 1973. Soil forming processes in acid sulphate soils. Pp. 66-130. In: H. Dost (ed.), Acid Sulphate Soils-Proceedings of the International Symposium on Acid Sulphate Soils 13-20 August 1972, Wageningen, The Netherlands. Brodie, M.J., L . M . Broughton and A .M. Robertson. 1991. A conceptual rock classification system for waste management and a laboratory method for ARD prediction from rock piles. In: Second International Conference on the Abatement of Acidic Drainage. Conference Proceedings, Volumes 1-4, September 16-18, 1991, Montreal, Canada. Broughton, L .M. , R.W. Chambers and A . M . Robertson. 1992. Mine Rock Guidelines Design and Control of Drainage Water Quality. Report No. 93301 prepared for Saskatchewan Environment and Public Safety by Steffen, Robertson and Kirsten Inc, Vancouver, BC. Bysouth, G.D., K.V. Campbell, G.E. Barker and G.K. Gagnier. 1993. Gibraltar: Tonalite-Trondhjemite fractionation of peraluminous magma and the formation of syntectonic porphyry copper mineralization. Preprint CEVI, June 1993. Bysouth, G.D. and T.L. Carpenter. 1984. Mineralogy and Copper Inventory of Gibraltar's Waste and Low Grade Dumps. Gibralter Internal Report. Pp. 13. Cady, J.G., L.P. Wilding and L.R. Drees. 1986. Petrographic Microscope Techniques. Pp.185-218. In: A. Klute (ed.). Methods of Soil Analysis: Part 1. Physical and Mineralogical Methods (Second Edition). American Society of Agronomy, Inc. and Soil Science Society of America, Inc. Madison, Wisconsin. 236 Literature Cited Callahan, J. 1987. A nontoxic heavy liquid and inexpensive filters for separation of mineral grains. Journal of Sedimentary Petrology. 57(4):765-766. Calvert, C.S., S.W. Buol and S.B. Weed. 1980a. Mineralogical characteristics and transformations of a vertical rock-saprolite-soil sequence in the North Carolina Piedmont: I. Profile morphology, chemical composition, and mineralogy. Soil Science Society of America Journal. 44:1096-1103. Calvert, C.S., S.W. Buol and S.B. Weed. 1980b. Mineralogical characteristics and transformations of a vertical rock-saprolite-soil sequence in the North Carolina Piedmont: JJ. Feldspar alteration products-their transformations through the profile. Soil Science Society of America Journal. 44:1104-1112. Canadian System of Soil Classification, 1978. Carrol, D. 1970. Rock Weathering. Plenum Press, New York. Carson, C D . , D.S. Fanning and J.B. Dixon. 1982. Alfisols and ultisols with acid sulphate weathering features in Texas. Pp. 127-146. In: J.A. Kittick, D.S. Fanning, L.R. Hossner (eds.). Acid Sulphate Weathering - SSSA Special Publication Number 10, Proceedings of a symposium sponsored by Divisions S-9, S-2, S-5, and S-6 of the Soil Science Society of America in Fort Collins, Colourado, 5-10 Aug. 1979. Carter, M.R. 1993. Soil Sampling and Methods of Analysis, (ed.), Canadian Society of Soil Science, Lewis Publishers. Carver, R.E. 1971. Heavy-mineral separation. Pp.427-452. In: R.E. Carver (ed.). Procedures in Sedimentary Petrology. John Wiley and Sons, Inc. Toronto, Canada. Casey, W.H. and C. Ludwig. 1995. Silicate mineral dissolution as a ligand-exchange reaction. Pp. 87-117. In: A.F. White and S.L. Brantley (eds.) Chemical Weathering Rates of Silicate Minerals. Reviews in Mineralogy Volume 31. Mineralogical Society of America, Washington, D.C. Chao, T.T. 1984. Use of partial dissolution techniques in geochemical exploration. Journal of Geochemical Exploration. 20:101-135. Chao, T.T. and L. Zhou. 1983. Extraction techniques for selective dissolution of amorphous iron oxides from soils and sediments. Soil Science Society of America Journal. 47:225-232. Chapman, B.M., D.R. Jones and R.F. Jung. 1983 Processes controlling metal ion attenuation in acid mine drainage streams. Geochimica et Cosmochimica Acta. 47:1957-1973. 237 Literature Cited Chesworth, W. 1992. Weathering systems. Pp. 19-40 In: I.P. Martini and W. Chesworth (eds.), Weathering, Soils and Paleosoils. Elsevier. Choquette, M . , P. Gelinas and D. Isabel. 1994. Monitoring of Acid Mine Drainage: chemical data from La Mine Doyon - south waste rock dump. Mend Report 1.14.2 Colbourn, P. 1980. Estimation of the potential oxidation rate of pyrite in coal mine spoils. Reclamation Review. 3:121-123. Commeau, J.A., L.J. Poppe and R.F. Commeau. 1987. Separation and Identification of the Silt-Sized Heavy Mineral Fraction in Sediments. Pp. 13. U.S. Geological Survey Circular 1071. Cravotta, C A . 1994. Chapter 23: Secondary Iron-Sulphate Minerals as Sources of Sulphate and Acidity. Pp. 345-364. In: Environmental Geochemistry of Sulphide Oxidation. American Chemical Society. Dahlgren, R.A. 1994. Chapter 14: Quantification of Allophane and Imogolite. Pp. 430-451. In: R.J. Luxmoore (ed.), Quantitative Methods in Soil Mineralogy, Proceedings of a symposium sponsored by Division S-9 of the Soil Science Society of America, San Antonio, Texas, October, 23-24, 1990. Soil Science Society of America, Inc. Madison, Wisconsin. Davis, A., R.L. Olsen and D.R. Walker. 1991. Distribution of metals between water and entrained sediment in streams impacted by acid mine drainage, Clear Creek, Colourado. U.S.A. Applied Geochemistry. 6:333-348. Dawson, R.F., R.L. Martin and D.S. Cavers. 1995. Review of long term geotechnical stability of mine spoil piles. AGRA report prepared for Ministry of Energy, Mines and Petroleum Resources, BC. Deer, W.A., R.A. Howie and J. Zussman. 1992. An Introduction to the Rock-Forming Minerals. Longmans, London. Deer, W.A., R.A. Howie and J. Zussman. 1962. Rock Forming Minerals: Vol. 5. Non-Silicates. Longmans, London. De Kimpe, C. and N. Miles. 1992. Formation of swelling clay minerals by sulphide oxidation in some metamorphic rocks and related soils of Ontario, Canada. Canadian Journal of Soil Science. 72:263-270. Dent, D. 1986. Acid sulphate soils: a baseline for research and development. Publication 39. International Institute for Land Reclamation and Improvement/TLRI, Wageningen, The Netherlands. 238 Literature Cited Dutrizac, J.E. and S. Kaiman. 1976. Synthesis and properties of jarosite-type compounds. Canadian Mineralogist. 14:151-158. Dugger, D.L., J.H. Stanton, B.N. Irby, B.L. McConnell, W.W. Cummings and R.W. Maatman. 1964. The exchange of twenty metal ions with the weakly acidic silanol group of silica gel. Journal of Physical Chemistry. 68:757-760. Earley HI, D., S.E. Paulson and S.E. Brink. 1990. The Effects of Rock Mineralogy, Chemistry, and Texture on In Situ leaching of Oxide Copper Ores from the Santa Cruz Deposit, Arizona. Society of Mining Engineers. AIME Preprint 90-182, Pp.8. Eggleton, R.A. 1988. The Application of Micro-beam Methods to Iron Minerals in Soils. Pp. 165-201. In: J.W. Stucki, B.A. Goodman, U. Schwertmann. (eds.). Iron in Soils and Clay Minerals. Proceedings of the NATO Advanced Study Institute on Iron in Soils and Clay Minerals, Bad Windsheim, F.R.G. July 1-13, 1985. NATO ASI series. Series C, Mathematical and Physical Sciences; Vol 217. Eggleton, R.A., C. Foudoulis and D. Varkevisser. 1987. Weathering of basalt: Changes in rock chemistry and mineralogy. Clays and Clay Minerals. 35(3): 161-169. Evangelou, V.P. 1994. Potential microencapsulation of pyrite by artificial inducement of FeP04 coatings. Pp. 96-103. Paper presented at the International Land Reclamation and Mine Drainage Conference and the Third International Conference on the Abatement of Acidic Drainage, Pittsburg, PA, April 24-29, 1994. Evangelou, V.P. 1983. Pyritic coal spoils: their chemistry and water interactions. Pp. 175-227. In: S.S. Augustithis (ed.), Leaching and Diffusion in Rocks and Their Weathering Products. Theophrastus Publishing and Proprietary Co., Athens, Greece. Evangelou, V.P., J.H. Grove and R.E. Phillips. 1982. Factors controlling water movement in acid spoils. Pp. 5-9. In: Symposium on Surface Mine Hydrology, Sedimentology and Reclamation, University of Kentucky, Lexington, Kentucky December 5-10, 1982. Fallman, A. -M. , and B. Aurell. 1996. Leaching tests for environmental assessment of inorganic substances in wastes, Sweden. The Science of the Total Environment. 178:71-84. Fanning, D.S, M.C. Rabenhorst and J.M. Bigham. 1993. Colours of Acid Sulphate Soils. Pp. 91-108. In: J.M. Bigham and E.J. Ciolkosz (eds.), Soil Colour. Soil Science Society of America Special Publication 31, Madison, Wisconsin, USA. Feasby, G. And R.K. Jones. 1994. Report of results of a workshop on mine reclamation - -Toronto, Ontario, March 10-11, 1994. Hosted by the IGWG-Industry Task Force on Mine Reclamation. 239 Literature Cited Feitknecht, W. And P. Schindler. 1963. Solubility product of metal oxides, metal hydroxides, and metal hydroxide salts in aqueous solutions. Pure and Applied Chemistry. 6:130-199. Filion, M . and K. Ferguson. 1990. Acidic drainage research in Canada. Pp. 185-201. In: Acid Mine Drainage: Design for Closure-Papers presented at the G A C / M A C Joint Annual Meeting, Vancouver, BC. May 16-18,1990. Filipek, L.H. T.T. Chao and R.H. Carpenter. 1981. Factors affecting the partitioning of Cu, Zn, and Pb in boulder coatings and stream sediments in the vicinity of a polymetallic sulphide deposit. Chemical Geology. 33:45-64. Filipek, L.H. , D.K. Nordstrom and W.H. Ficklin. 1987. Interaction of acid mine drainage with waters and sediments of West Squaw Creek in the West Shasta mining district, California. Environmental Science and Technology. 27:388-396. Fonseca, E.C., J.C. Cardoso, M.E. Martins and M . M Vairinho. 1992. Selective chemical extraction of Cu from selected mineral and soil samples: enhancement of Cu geochemical anomalies in Southern Portugal. Journal of Geochemical Exploration. 43:249-263. Gatehouse, S., D.W. Russell and J.C. Van Moort. 1977. Sequential soil analysis in exploration geochemistry. Journal of Geochemical Exploration. 8:483-494. Ghomshei, M . , A. Holmes, E. Denholm, R. Lawrence and T. Carriou. 1997. Acid rock drainage from the Samatosum waste dump, British Columbia, Canada. In: Fourth International Conference on Acid Rock Drainage. Proceedings, Volumes 1, May 31- June 6, 1997, Vancouver, Canada. Goldich, S.S. 1938. A study on rock weathering. Journal of Geology. 46:17-58. Graham, R . C , S.B. Weed, L.H. Bowen and S.W. Buol. 1989a. Weathering of iron-bearing minerals is soils and saprolite of the Northern Carolina Blue Ridge front: I. Sand-sized primary minerals. Clays and Clay Minerals. 37(1): 1-28. Graham, R . C , S.B. Weed, L.H. Bowen and S.W. Buol. 1989b. Weathering of iron-bearing minerals is soils and saprolite of the Northern Carolina Blue Ridge front: II. Clay mineralogy. Clays and Clay Minerals. 37(l):29-40. Gruebel, K.A., J.A. Davis and J.O. Leckie. 1988. The feasibility of using sequential extraction tecniques for arsenic and selenium in soils and sediments. Soil Science Society of America Journal. 52:390-397. Herbert, R.B. 1997. Partitioning of heavy metals in podzol soils contaminated by mine drainage waters, Dalarna, Sweden. Water, Air, and Soil Pollution. 96:39-59. 240 Literature Cited Herbert, R.B. 1995. Precipitation of Fe oxyhydroxides and jarosite from acidic groundwater. GFF. 117:81-85. Hickey, M.G. and J.A. Kittrick. 1984. Chemical partitioning of cadmium, copper, nickel and zinc in soils and sediments containing high levels of heavy metals. Journal of Environmental Quality. 13:372-376. Horn, M.E. and S.L. Chapman. 1968. Clay mineralogy of some acid sulphate soils on the Guinea coast. Int. Congr. Soil Sci., Trans. 9 t h (Adelaide, Aust.) m:31-40. Huang, P.M. and Violante, A. 1986. influence of organic acids on crystallization and surface properties of precipitation products of aluminum. In: P.M. Huang and M . Schnitzer (eds), Interactions of Soil Minerals with Natural Organics and Microbes, SSSA Spec. Pub. 17, pp. 159-221. Soil Science Society of America, Madison, Wisonsin. Hurst, V.J. 1977. Visual estimation of iron saprolite. Geological Society of America Bulletin. 88:174-176. Jackson, M.L., C H . Lim and L.W. Zelazny. 1986. Chapter 6: Oxides, Hydroxides, and Aluminosilicates. Pp. 101-150. In: A. Klute (ed.), Methods of Soil Analysis, Part 1: Physical and Mineralogical Methods 2 n d Edition, American Society of Agronomy, Inc. and Soil Science Society of America, Inc. Madison, Wisconsin Jambor, J.L. 1994. Mineralogy of sulphide-rich tailings and their oxidation products. Pp. 59-102. In: J.L. Jambor and D.W. Blowes (eds.), Environmental Geochemistry of Sulphide Mine-Wastes, Short Course Handbook, Mineralogical Association of Canada. Vol.22, Waterloo, Ontario Jongmans, A.G. , E. Veldkamp, N. van Breeman and I. Staritsky. 1993. Micromorphological characterization and microchemical quantification of weathering in an alkali basalt pebble. Soil Science Society of America Journal. 57:128-134. Karathanasis, A.D. and Y.L. Thompson. 1995. Mineralogy of iron precipitates in a constructed acid mine drainage wetland. Soil Science Society of America Journal. 59:1773-1781. Karathanasis, A.D., V.P. Evangelou and Y.L. Thompson. 1988. Aluminum and iron equilibria in soil solutions and surface waters of acid mine watersheds. Journal of Environmental Quality. 17:534-543. Karlsson, S., B. Allard and K. Hakansson. 1988. Characterization of suspended solids in a stream receiving acid mine effluents, Bersbo, Sweden. Applied Geochemistry. 3:345-356. 241 Literature Cited Katz, M . 1969. The biological and ecological effects of acid mine drainage with particular emphasis to the waters of the Appalachian region. Appalachian Regional Commission, Appendix F, Washington, DC. Kaurichev, IS., Ivanova, T.N. and Nozorunova, Y . M . 1963. Low molecular weight organic acid content of water-soluble organic matter in soils. Soviet Soil Science. 1963:223-229. Keller, C. and J.-C. Vedy. 1994. Distribution of copper and cadmium fractions in two forest soils. Journal of Environmental Quality. 23:987-999. Keller, L.P., G.J. McCarthy and J.L. Richardson. 1986. Mineralogy and stability of soil evaporites in North Dakota. Soil Science Society of America Journal. 50:1069-1071. Kennedy, L.P. and F.C. Hawthorne. 1987. A Mineralogical Study of the Mine Tailings from Farley and Sherridon, northern Manitoba. Phase I report, Manitoba Department of Energy and Mines. Kent, A. and B. Johnson. 1993. Risk based evaluation of mine waste dumps. Pp. 11-21. In: Proceedings of the 17th Annual British Columbia Mine Reclamation Symposium. May 4-7, 1993, Port Hardy, B.C. Kinniburgh, D.G., M.L. Jackson and J.K. Syers. 1976. Adsorption of alkaline earth, transition, and heavy metal cations by hydrous oxide gels of iron and aluminum. Soil Science Society of America Journal. 40:796-799. Kisvarsanyi, G. and P.D. Proctor. 1967. Trace element content of magnetites and hematites, south east Missouri Iron Metallogenic Province, U.S.A. Economic Geology. 62:449-471. Klein, C. and C.S. Hurlbut, Jr. 1985. Manual of Mineralogy (after J.D. Dana) 20th Ed. John Wiley and Sons, New York. Klohn Leonoff Consulting Engineers. 1991. Acid rock drainage project: Review and assessment study. A report prepared for the B.C. Acid Mine Drainage Task Force. Pp. 62. Knapp, R. 1987. The biogeochemistry of acid generation in sulphide tailings and waste rock. Proc. Acid Mine Drainage Seminar/Workshop. Halifax, Nova Scotia, March 23-26. Environment Canada Catalogue En 40-11-7/1987. Kohut, C.K. and M.J. Dudas. 1993. Evaporite mineralogy and trace-element content of salt-affected soils in Alberta. Canadian Journal of Soil Science. 73:399-409. 242 Literature Cited Koons, R.D., P.A. Helmke and M.L. Jackson. 1980. Association of trace elements with iron oxides during rock weathering. Soil Science Society of America, Proceedings. 44:155-159. Koyanagi, V . M . and A. Panteleyev. 1992. Natural acid-drainage in the Mount Mclntosh/Pemberton Hills area, Northern Vancouver Island. Geological Fieldwork 1992:445-450. (Paper 1993-1). Kronberg, B.I. and H.W. Nesbitt. 1981. Quantification of weathering, soil geochemistry and soil fertility. Journal of Soil Science. 32:453-459. Kwong, Y.T.J, and D.R. Van Stempvoort. 1994. Attenuation of acid rock drainage in a natural wetland system. Pp. 382-392. In: C.N. Alpers and D.W. Blowes (eds.), Environmental Geochemistry of Sulphide Oxidation. American Chemical Society, Washington, 1994. Langmuir, D. And D.O. Whittemore. 1971. Variations in the stability of precipitated ferric oxyhydroxides. Pp. 209-234. In: J.D. Hem (ed.), Nonequilibrium Systems in Natural Water Chemistry. Advances in Chemistry Series. No. 106. Last, W.M. 1989. Continental brines and evaporites of the northern Great Plains of Canada. Sedimentary Geology. 64:207-221. Lavkulich, L . M . 1982. Laboratory Methods for the Pedology Laboratory. Department of Soil Science, University of British Columbia. Vancouver, B.C. Canada. Lazaroff, N., W. Sigal and A. Wasserman. 1982. Iron oxidation and precipitation of ferric hydroxysulphates by resting Thiobacillus ferrooxidans cells. Applied Environmental Microbiology. 43:924-938. Leckie, J.O., M . M . Benjamin, K.F. Hayes, G. Kaufman and S. Altmann. 1980. Adsorption-coprecipitation of trace metals from water with iron hydroxide. Final Report EPRI-RP-910-1; Electric Power Research Institute, Palo Alto, California Lee, S.Y., D.H. Phillips, J.T. Amnions and D.A. Lietzke. 1990. A microscopic study of iron and manganese oxide distribution in soils from east Tennessee. Pp. 511-524. In: L.A. Douglas (ed.), Soil Micro-Morphology: A Basic and Applied Science. Proceedings of the VHIth International Working Meeting of Soil Micromorphology, San Antonio, Texas, July 1988. Levy, D.B., K.H. Custis, W.H. Casey and P.A. Rock. 1997. A comparison of metal attenuation in mine residue and overburden material from an abandoned copper mine. Applied Geochemistry. 12:203-211. 243 Literature Cited Lin, Z. and R.B. Herbert Jr. 1997. Heavy metal retention in secondary precipitates from a mine rock dump and underlying soil, Dalarna, Sweden. Environmental Geology. 33(1): 1-12. Lin, Z. 1996. Leachate chemistry and precipitates mineralogy of Rudolfsgruvan mine waste rock dump in central Sweden. Water Science and Technology. 33(6):163-171. Lindsay, W.L. 1979. Chemical Equilibria in Soils. John Wiley & Sons, New York. Lister, D. 1994. An Assessment of Acid Rock Drainage Potential of Waste Rock and Implications for Long Term Weathering of the North Dump at Island Copper Mine, Port Hardy, B.C. M.Sc. Thesis, Pp. 217. Lowson, R.T. 1982. Aqueous oxidation of pyrite by molecular oxygen. Chemical Reviews Vol.82, No.5. October. Lundstrom, U. and Ohman, L-O. 1990. Dissolution of feldspars in the presence of natural organic solutes. Journal of Soil Science. 41:359-369. Manahan, S.E. 1994. Environmental Chemistry - 6 t h Edition. Lewis Publishers, Boca Raton, Florida, USA. Manley, E.P. and Evans, L.J. 1986. Dissolution of feldspars by low-molecular weight aliphatic and aromatic acids. Soil Science. 141(2): 106-112. Marozas, D.C. 1989. Computer modeling applications in the characterization of in situ geochemistry. BuMines Information Circular 9216, US Bureau of Mines. 49-57. McBride, M.B. 1989. Reactions controlling heavy metal solubility in soils. Pp. 1-56. In: B.A. Stewart (ed.), Advances in Soil Science - Volume 10. Springer-Verlag. New York, New York. McColl, J.G. and Pohlman, A.A. 1986. Soluble organic acids and their chelating influence on Al and other metal dissolution from forest soils. Water, Air, and Soil Poll. 31:917-927. McKeague, J.A. 1967. An evaluation of 0.1 M pyrophosphate and pyrophosphate-dithionite in comparison with oxalate as extractants of the accumulation products in podzols and some other soils. Canadian Journal of Soil Science. 47:95-99. McKeague, J.A. and J.H. Day. 1966. Dithionite- and oxalate-extractable iron and aluminum in soils . Canadian Journal of Soil Science. 46:13-22 McKenzie, R.M. 1980. The adsorption of lead and other metals on oxides of manganese and iron. Australian Journal of Soil Research. 18:61-73. 244 Literature Cited McSweeney, K. and F.W. Madison. 1988. Formation of cemented subsurface horizon in sulfidic minewaste. Journal of Environmental Quality. 17:256-262. Mehra, O.P. and M.L. Jackson. 1960. Iron oxide removal from soils and clays by a dithionite-citrate system buffered with sodium bicarbonate. Clays Clay Minerals. 7:317-327. Mehta, A.P. and L.E. Murr. 1983. Fundamental studies of the contribution of galvanic interaction to acid-bacterial leaching of mixed metal sulphides. Hydrometallurgy. 9:235-256. MEND, 1992. Waste rock sampling manual. Prepared for Energy Mines and Resources, CANMET-MSL Division, MEND Project 4.5.1, Phase I, September 1992. Miller, M.B., T.H. Copper and R.H. Rust. 1993. Differentiation of an eluvial fragipan from dense glacial till in Northern Minnesota. Soil Science Society of America Journal. 57:787-796. Miller, F.M. 1984. Chemistry: Structure and Dynamics. McGraw-Hill, Inc. USA. Mining Association of B.C. 1991. The State of the Minerals Industry in British Columbia:Working Toward 2000. September 1991. Monterroso, C , E. Alvarez and F. Macias. 1994. Speciation and solubility controls of Al and Fe in minesoil solutions. The Science of the Total Environment. 158:31-43. Moore, J.N., S.N. Luoma and D. Peters. 1991. Downstream effects of mine effluent on an intermontane riparian system. Canadian Journal of Fisheries and Aquatic Sciences. 48:222-232. Morin, K.A., N.M. Hutt and R. McArthur. 1995. Statistical assessment of past water chemistry to predict future chemistry at Noranda Minerals' Bell Mine. Sudbury '95, Mining and the Environment. Morin, K.A. and N.M. Hutt. 1994. An empirical technique for predicting the chemistry of water seeping from mine-rock piles. Pp. 12-19. In: International Land Reclamation and Mine Drainage Conference and Third International Conference on the Abatement of Acidic Drainage, Vol.LMine Drainage, Proceedings of a conference held in Pittsburgh, PA on April 24-29,1994, Bureau of Mines Special Publication SP 06A-94. Morin, K.A., E . Gerencher, C E . Jones and D.E. Konasewich . 1991. A Critical Literature Review of Acid Drainage from Waste Rock. Mend Report No. 1.11.1 Murad, E. , U. Schwertmann, J.M. Bigham and L. Carlson. 1994. Mineralogical characteristics of poorly crystallized precipitates formed by oxidation of Fe 2 + in acid mine sulphate 245 Literature Cited waters. Pp. 190-200. In: C.N. Alpers and D.W Blowes (eds.), Environmental Geochemistry of Sulphide Oxidation. Am. Chem.Soc.Symposium Series 550. Murray, D.R. 1977. Pit Slope Manual Supplement 10-1. C A N M E T Report 77-31. Department of Energy, Mines and Resources Canada. Ottawa, Ontario. Nichols, R.S. 1987. Rock segregation in waste dumps. Pp. 105-120. In: Flow-Through Rock Drains, Proceedings of the International Symposium convened at Inn of the South, Cranbrook, B.C. Canada. September 8-11,1986. Nicholson, R.V., R.W. Gillham and E.J. Reardon. 1990. Pyrite oxidation in carbonate-buffered solution: 2. Rate control by oxide coatings. Geochimica et Cosmochimica Acta. 54:395-402. Nirel, P.M.V. and F.M.M. Morel. 1990. Pitfalls of sequential extractions. Water Resources. 24(8): 1055-1056. Nordstrom, D.K. and Ball J.W. 1986. The geochemical behaviour of aluminum in acidified surface waters. Science. 232:54-56. Nordstrom, D.K. 1982. Aqueous pyrite oxidation and the consequent formation of secondary iron minerals. Pp. 37-56. In: J.A. Kittick, D.S. Fanning, L.R. Hossner (eds.). Acid Sulphate Weathering - SSSA Special Publication Number 10, Proceedings of a symposium sponsored by Divisions S-9, S-2, S-5, and S-6 of the Soil Science Society of America in Fort Collins, Colourado, 5-10 Aug. 1979. Nortcliff, S. 1988. Soil formation and characteristics of soil profiles. Pp. 168-212. In: A. Wild (ed.), Russell's Soil Conditions and Plant Growth-ll111 Ed., Longman Sientific and Technical, Essex, England. Okazaki, M . , K. Takamidoh and I. Yamane. 1986. Adsorption of heavy metal cations on hydrated oxides and oxides of iron and aluminum with different crystallinities. Soil Science and Plant Nutrient. 32(4):523-533. Oilier, C D . 1975. Weathering. Longman Group Ltd. Paine, P.J. 1987. An historic and geographic overview of acid mine drainage. Pp. 1-45.Proceedings of the Acid Mine Drainage Seminar/Workshop, Halifax, Nova Scotia, March 23-26. Environment Canada Catalogue En 40-11-7/1987. Parkhurst, D.L., D.C. Thorstenson and L.N. Plummer. 1982. PHREEQE - A computer program for geochemical calculations. U.S. Geological Survey WRI 82-14. Pp. 29. Perkins, E.H., H.W. Nesbitt, W.D. Gunter, L . C St-Arnaud and J.R. Mycroft. 1994. Draft -Critical Review of Geochemical Models Adaptable for Prediction of Acidic Drainage 246 Literature Cited from Waste Rock. Report submitted to MEND Program, Predition Committee, November 1994. Petersen, R.G. and L.D. Calvin. 1986. Chapter 2 - Sampling. Pp. 33-52. In: A. Klute (ed.), Methods of Soil Analysis, Part 1 - Physical and Mineralogical Methods, 2 n d Edition. Soil Science Society of America, Inc. Pierce, W.G., Belzile, N., Wiseman, M.E., and Winterhalder, K. 1994. Composted organic wastes as anaerobic reducing covers for long term abandonment of acid-generating tailings. In: International Land Reclamation and Mine Drainage Conference and Third International Conference on the Abatement of Acid Drainage, Vol. 2, April 24-29, 1994, Pittsburgh, pp. 148-157. Pohlman, A.A. and McColl, J.G. 1986. Kinetics of metal dissolution from forest soils by organic acids. Journal of Environmental Quality. 15:86-92. Price, W.A. and Y.T.J. Kwong. 1997. Waste rock weathering:, sampling and analysis: observations from the British Columbia Ministry of Employment and Investment Database. Pp. 31- 45. In: Proceeding from the Fourth International Conference on Acid Rock Drainage, Vol 1, May 31-June 6,1997, Vancouver, B.C. Canada. Price Waterhouse, 1995. The Mining Industry in British Columbia 1994. Price Waterhouse Mining Indusrty Services Group. Pugh, C.E., L.R. Hossner and J.B. Dixon. 1984. Oxidation rate of iron sulphide as affected by surface area, morphology, oxygen concentration, and autotrophic bacteria. Soil Science. 137(5):309-314. Rahner, S., M . Magaritz and A.J. Amiel. 1993. Scavenging effects of Fe-hydroxide coated sand in phreatic aquifers. Applied Geochemistry. 2 (Suppl. Issue): 145-148. Renton, J.J., T.E. Rymer and A.H. Stiller. 1988. A laboratory procedure to evaluate the acid producing potential of coal associated rocks. Mining Science and Technology. 7:227-235. Qiang, T., S. Xiao-quan and N. Zhe-ming. 1994. Evaluation of a sequential extraction procedure for the fractionation of amorphous iron and manganese oxides and organic matter in soil. The Science of the Total Environment. 151:159-165. Rai, D. and J.A. Kittrick. 1989. Chapter 4: Mineral Equilibria and the Soil System. Pp. 161-198. In: J.B. Dixon and S.B. Weed (eds.) Minerals is Soil Environments (2nd Edition) -SSSA Book Series, no.l. Madision, Wisconsin, USA. 247 Literature Cited Ramos, L. , L . M . Hernandex and M J . Gonzalez. 1994. Sequential fractionation of copper, lead, cadmium and zinc in soils from or near Donana National Park. Journal of Environmental Quality. 23:50-57. Rauret, G. R. Rubio, J.F. Lopez-Sanchez and E. Casassas. 1989. Specific procedure for metal solid speciation in heavily polluted river sediments. International Journal of Environmental Analytical Chemistry. 35:89-100. Rebertus, R.A., S.B. Weed and S.W. Buol. 1986. Transformations of biotite to kaolinite during saprolite-soil weathering. Soil Science Society of America Journal. 50:810-819. Reddy, K.J. and S.P. Gloss. 1993. Geochemical speciation as related to the mobility of F, Mo and Se in soil leachates. Applied Geochemistry. Supplemental Issue No.2:159-163. Ribet, I., C.J. Ptacek, D.W. Blowes and J.L. Jambor. 1995. The potential for metal release by reductive dissolution of weathered mine tailings. Journal of Contaminant Hydrology. 17:239-273. Ritchie, A.I.M. 1994. The waste-rock environment. Pp. 133-161. In: D.W. Blowes and J.L. Jambor (eds.), Environmental Geochemistry of Sulphide Mine-Wastes, Short Course Handbook, Mineralogical Association of Canada. Vol.22, Waterloo, Ontario Robert, M . and D. Tessier. 1992. Incipient weathering: some new concepts on weathering, clay formation and organization. Pp. 71- 105. In: I.P. Martini and W. Chesworth (eds.), Weathering, Soils and Paleosoils. Elsevier, 1992. Roberts, J.A., Daniels, W.L., Bell, J . C , and Burger, J.A. 1988. Early stages of mine soil genesis in a southwest Virginia spoil lithosequence. Soil Sci. Soc. Am. J. 52:716-723. Rhoades, J.D. 1982. Chapter 10: Soluble Salts. Pp. 167-179. In: A.L. Page (ed.), Methods of Soil Analysis, Part 2: Chemical and Microbiological Properties. 2 n d Edition, American Society of Agronomy, Inc. and Soil Science Society of America, Inc. Madison, Wisconsin. Rybicka, E.H. 1993. Phase-specific bonding of heavy metals in sediments of the Vistula River, Poland. Applied Geochemistry. 2 (Suppl. Issue):45-48. Salahub, D., Sahlstrom, D., and Wilson S. 1991. Reclamation and revegetation of mine spoils using biosolids - Princeton Trial Projects. In: Mine Reclamation - Building Confidence, Proceedings of the Seventeenth Annual British Columbia Mine Reclamation Symposium, May 4- 7,1991, Port Hardy, BC, pp. 55-63. 248 Literature Cited Schindler, P.W., B. Furst, R.Dick and P.U. Wolf. 1976. Ligand properties of surface silanol groups: I.Surface complex formation with Fe 3 + , C u 2 + , C d 2 + , and Pb 2 + . Journal of Colloid Interface Sciences. 55:469-475. Schoeneberger, P.J., S.B. Weed, A. Amoozegar and S.W. Buol. 1992. Colour zonation associated with fractures in a felsic gneiss saprolite. Soil Science Society of America Journal. 56:1855-1859. Schulze, D.G. 1994. Chapter 13: Differential X-ray Diffraction Analysis of Soil Minerals. Pp. 412- 429. In: R.J. Luxmoore (ed.), Quantitative Methods in Soil Mineralogy, Proceedings of a symposium sponsored by Division S-9 of the Soil Science Society of America, San Antonio, Texas, October, 23-24, 1990. Soil Science Society of America, Inc. Madison, Wisconsin. Schulze, D.G. 1981. Identification of soil iron oxide minerals by differential x-ray diffraction. Soil Science Society of America Journal. Soil Science Society of America Journal. 45:437-440. Schwab, A.P. 1995. Application of chemical equilibrium modeling to leachates from coal ash. Pp. 143-161. In: R.H. Loeppert, A.P. Schwab, and S. Goldberg (eds.), Chemical Equilibrium and Reaction Models. SSSA Special Publication 42. Schwertmann, U. 1993. Relationships Between Iron Oxides, Soil Colour, and Soil Formation. Pp. 51-69. In: J.M. Bigham and E.J. Ciolkosz (eds.), Soil Colour. Soil Science Society of America Special Publication 31, Madison, Wisconsin, USA. Schwertmann, U. 1973. Use of oxalate for Fe extraction from soils. Canadian Journal of Soil Science. 53:244-246. Schwertmann, U. and R.W. Fitzpatrick. 1992. Iron minerals in surface environments. Pp.7-30. In: H.C.W. Skinner and R.W. Fitzpatrick (eds.), Biomineralization Processes of Iron and Manganese - Modern and Ancient Environments. Catena Verlag, Germany. Schwertmann, U. and R.M. Taylor. 1989. Iron oxides. Pp. 370-438. In: J.B. Dixon and S.B. Weed (eds.), Minerals In Soil Environments (2nd Edition)-SSSA Book Series, No. 1. Soil Science Society of America, Madison, WI. Schwertmann, U., D.G. Schulze and E. Murad. 1982. Identification of ferrihydrite is soils by dissolution kinetics, differential x-ray diffraction, and Mossbauer spectroscopy. Soil Science Society of America Journal. 46:869-875. Short, T.M., J.A. Black and W.J. Birge. 1990. Effects of acid-mine drainage on the chemical and biological character of an alkaline headwater stream. Archive of Environmental Contamination and Toxicology. 19:241-248. 249 Literature Cited Shuman, L . M . 1976. Adsorption of Zn by Fe and Al hydrous oxides as influenced by aging and pH. Soil Science Society of America Journal. 41:703-706. Soil Survey No. 53. 1998. Williams Lake and Alexis Creek Area. Sopper, W.E. 1992. Reclamation of mine land using municipal sludge. In: Advances in Soil Science: Soil Restoration (eds R. Lai and B.A. Stewart), Vol. 17, pp. 351-431. Springer-Verlag, New York. Sposito, G. 1989. The Chemistry of Soils. Oxford University Press. New York, New York. Steffan, Robertson, and Kirsten (in association with Norecol Environmental Consultants and Gormely Process Engineering). 1989. Acid Mine Drainage Draft Technical Guide Vol.1 Prepared for the BC Acid Mine Drainage Task Force. Stevenson, F.J. 1967. Organic acids in soils. In: A.D. McLaren and G.H. Petersen (eds), Soil Biochemistry, Vol. I, Academic Press, New York, pp. 110-146. Stolt, M.H., J.C. Baker and T.W. Simpson. 1992. Characterization and gneiss of saprolite derived from gneissic rocks of Virginia. Soil Science Society of America Journal. 56:531-539. Strdmberg, B., S. Banwart, J.W. Bennett and A.I.M. Ritchie. 1994. Mass balance assessment of initial weathering processes derived from oxygen consumption rates in waste sulphide ore. Paper presented at the International Land Reclamation and Mine Drainage Conference and the Third International Conference on the Abatement of Acidic Drainage, Pittsburgh, PA, April 24-29,1994. Sturchio, N.C., K. Muehlenbachs, and M.G. Seitz. 1986. Element redistribution during hydrothermal alteration of rhyolite in active geothermal system: Yellow Stone drill cores Y-7 and Y-8. Geochimica et Cosmochimica Acta. 50:1619-1631. Stumm, W., G. Furrer, E. Wieland and B. Zinder. 1985. The effects of complex-forming ligands on the dissolution of oxides and aluminosilicates. Pp. 55-74. In: J.I. Drever (ed.), The Chemistry of Weathering, D. Reidel Publishing Company. Sullivan, P.J., J.L. Yelton and K.J. Reddy. 1988. Solubility relationships of aluminum and iron minerals associated with acid mine drainage. Environmental Geology and Water Science. ll(3):283-287. Tabatabai, M.A. 1982. Chapter 28: Sulphur. Pp. 501-538. In: A.L. Page (ed.) Methods of Soil Analysis, Part 2, Chemical and Microbiological Properties, Second Edition. Soil Society of America, Inc. Madison, Wisconsin, USA. 250 Literature Cited Tan, K.H. 1989. Role of humic andfulvic acids in mineral weathering. Clay Res. 8(1-2): 11-20. Tasse, N., Germain, D., Dufour, C , and Tremblay, R. 1997. In: Proceedings of the 4 t h International Conference on Acid Rock Drainage, Vol. IV, May 31 - June 6, 1997, Vancouver, pp.1627-1642. Tessier, A., P.G.C. Campbell and M . Bisson. 1979. Sequential extraction procedure for the speciation of particulate trace metals. Analytical Chemistry. 51(7):844-851. Thornber, M.R. 1985. Supergene alteration of sulphides. VII. Distribution of Elements During the Gossan-Forming Process. Chemical Geology. 53:279-301. Thornber, M.R. 1983. The chemical processes of gossan formation. Pp. 67-73. In : R.E. Smith (ed.), Geochemical Exploration in Deeply Weathered Terrrains. CSIRO Division of Mineralogy, Short CourseAVorkshop, Floreat Park, W.A. 15-18 June 1982. Thornber, M.R. and J.E. Wildman. 1984. Supergene alteration of sulphides, VI. The binding of Cu, Ni, Zn, Co and Pb with iron-bearing gossan minerals. Chemical Geology. 44:399-434. Torrent, J. And V. Barron. 1993. Laboratory measurement of soil colour: theory and practice. Pp. 21-34. In: J.M. Bigham and E.J. Ciolkosz (eds.), Soil Colour. Soil Science Society of America Special Publication 31, Madison, Wisconsin, USA. Torrent, J., U. Schwertmann, H. Fechter and F. Alferez. 1983. Quantitative relationships between soil colour and hematite content. Soil Science. 136(6):354-358. Ure, A . M . 1996. Single extraction schemes for soil analysis and related applications. The Science of the Total Environment. 178:3-10. USDA, 1982. van Breeman, N. 1973a. Soil forming processes in acid sulfate soils. Pp. 66-131. In: H. Dost (ed.) Acid Sulphate Soils: Proceedings of the International Symposium 13-20 August 1972, Wageningen, JJ. Research Papers. International Institute for Land Reclamation and Improvement, Wageningen, The Netherlands. van Breeman, N. 1973b. Dissolved aluminum in acid sulphate soils and acid mine waters. Soil Science Society of America, Proceedings. 37:694-697. van Dam, D. and L.J. Pons. 1973. Micropedological observations on pyrite and its pedological reaction products. Pp. 169-196. In: H. Dost (ed.) Acid Sulphate Soils: Proceedings of the International Symposium 13-20 August 1972, Wageningen, n. Research Papers. 251 Literature Cited International Institute for Land Reclamation and Improvement, Wageningen, The Netherlands. von Steiger, B., K. Nowack and R. Schulin. 1996. Spatial variation of urease activity measured in soil monitoring. Journal of Environmental Quality. 25:1285-1290. Veiga, M.M. , H.D. Schorscher and W.S. Fyfe. 1991. Relationship of copper with hydrous ferric oxides: Salobo, Carajas, PA, Brazil. Ore Geology Reviews. 6:245-255. Velbel, M.A. 1990. Mechanisms of saprolization, isovolumetric weathering, and pseudomorphous replacement during rock weathering - A review. Pp. 17-18. In: Geochemistry of Earth's Surface and of Mineral Formation, 2 n d International Symposium, July 2-8, 1990, Aix en Provence, France. Walpole, R.E. 1982. Introduction to Statistics. 3r d Edition. Macmillan Publishing Co., Inc. Wang, H.D., G.N. White, F.T. Turner and J.B. Dixon. 1993. Ferrihydrite, lepidocrocite, and goethite in coatings from east Texas vertic soils. Soil Science Society of America Journal. 57:1381-1386. Warner, R.W. 1971. Distribution of biota in a stream polluted by acid mine-drainage. The Ohio Journal of Science. 71(4):202-215. Warnick, S.L. and H.L. Bell. 1969. The acute toxicity of some heavy metals to different species of aquatic insects. Water Pollution Control Federation Journal. 41(2):280-284. Warren, C.J. and M.J. Dudas. 1992a. Acidification adjacent to an elemental sulphur stockpile: I. Mineral weathering. Canadian Journal of Soil Science. 72:113-126. Warren, C.J. and M.J. Dudas. 1992b. Acidification adjacent to an elemental sulphur stockpile: n. Trace element redistribution. Canadian Journal of Soil Science. 72:127-134. Wassel, R.A. and A.L. Mills. 1983. Changes in water and sediment bacterial community structure in a lake receiving acid mine drainage. Microbial Ecology. 9:155-169. Weast, R.C. (Editor-in-Chief), 1977. Handbook of Chemistry and Physics. Chemical Rubber Publishing Company, Cleveland, Ohio. Whiting, D.L. 1981. Surface and groundwater pollution potential. Pp. 90-98. In: Design of Non-impounding Mine Waste Dumps. Society of Mining Engineers of America, Institute of Mining, Metallurgy and Petroleum Engineers Inc., New York, N.Y. Whittig, L.D. and W.R. Allardice. 1986. X-ray Diffraction Techniques. Pp. 331-362. In: A. Klute (ed.), Methods of Soil Analysis, Part 1: Physical and Mineralogical Methods 2 n d 252 Literature Cited Edition, American Society of Agronomy, Inc. and Soil Science Society of America, Inc. Madison, Wisconsin. Wilding, L.P., N.E. Smeck and L.R. Dress. 1977. Silica in Soils: Quartz, Cristobalite, Tridymite, and Opal. Pp. 471-552. In: J.B. Dixon and S.B. Weed (eds.), Minerals is Soil Environments. Soil Science Society of America, Madison, Wisconsin, USA Wilkes, B. 1987. Consequences of unregulated release of raw acid mine drainage into the Bulkey River, British Columbia, pp. 139-151. In: Proceedings of the Eleventh Annual British Columbia Mine Reclamation Symposium - Acid Mine Drainage: April 8-10, 1987, Campbell River, B.C. Williams, P.A. 1990. Oxide Zone Geochemistry. Ellis Horwood Limited, England. Winland, R.L., S.J. Traina and J.M. Bigham. 1991. Chemical composition of ochreous precipitates from Ohio Coal Mine Drainage. Journal of Environmental Quality. 20:452-460. Yanful, E.K., J. Mycroft, A.R. Pratt and L.C. St-Arnaud. 1997. Factors controlling metal leaching from mine rock: the case of Stratmat and Selbaie waste rock.s. In:- Fourth International Conference on Acid Rock Drainage. Proceedings, Volumes 2, May 31-June 6,1997, Vancouver, Canada. Zar, J.H.1984. Biostatistical Analysis. Prentice-Hall, Inc., Englewood Cliffs, New Jersey. 253 Literature Cited Appendix 254 Appendix XRF Data 255 6 £ w CQ d E ^ u 1 II o TT ON «"> flj Z ^  0 0 — in 2 in o> <N 2 O <N P-\o ^  o\ w « h in « S ^ ?2 ^ -n o r; C h „ N g °° 2 i*- 2 ON p - m © r - r - < i n s o m i n ^ o ^ ' O a r - i a a m m m - H - H - H f N t N m in f N f N fN m p - Os in Os oo O m rN cn SO 5 as o r-\o VO o r- r- p-I-H in <N <n ON TJ- fN T> tN -H -H *o h h 1J m oo i n O © ~ so »0 C\ * * C\ T ) S r- so •= M co h m in fi h ON P- ON OO 2 r- m ON ON oo p -o ON CN m os © Ov M T f m i/l (N N tN (N tN N <N ^ S r - « S S O ^ oo cn U - H W " 1 t C <N 00 2 £ & 8 ^ £ n ON •** ~ in o P» r-» ON Tf m — t N - H O O O ' - i — O o m o o o o o o o O O O W W l O i - t M W ON in o © fN in fN r- ON rN rn fN O LO O O O P-O O O T- O O O CO r- — Tf — cn •n so T t m oo o o - H - H — cn <N o — 8 O O O O O O O © © ir> -H in in Tt in o sO Tf rN — tN — -H ON ON © cn tN NO -H Os P- fN © Tf Tt oo © T t rn O s O s O s o d O N V O O s O s S T f r- - H T t fN tN TJ- oo so p- m os o © o © © © ©"©©©' O © ON 00 © oo i n oo so NO i n oo p Tt r-— T t m m cn oo fN © 0 o in in 01 CO co t— co ro N co fN OO © sO OS T t P- SO © - H © © ©' © O © Tf 00 ON — oo i n oo ON Tt —« SO tN ON - H - H ON Tf OO OO T> T t Tf T t ON SO •n in T t K r ^ s d o o s m m t N f N f N f S f N - H - H t N r N sovOfNOs — r - f N - H T t o o o o i n o \ i n t N T t © o o T t i n v o r n o s q © © - - ; « ri ci r i r i ri so so © r - —• oo i n m r -- H — • oo m oo so -* i n — N N H c i n i n t n T f i n © 0 0 T t t N 0 0 © s O T t 0 0 oo m o o » n o o o N i n i n T t T t T t t N r N ' — i cn cn tN O O O O O O O O © — o o o o o o o o o o o o o o o o o T f r - T t — m s o o N — r-Tt-H©ONln©(NOOTt s o o s i n T t r N o o p i n i n Tt rnTtcop - 'od inTtP- ' O in tN -H m in sp — — ^ m T t tN fN fN H o\ in os cn © fN fN in in in SO sO T t O0 0O © sS 00 © cn so ON — in in in in so cs so Os in ; in sp os 00 CO ON ON Os sO m — cn _ © —i — ON ON sp ON - H T t cn tN Tjj sp ON fN fN fN tN sO — ~- fN in ON — so in oo — Tt in P - so — so SO T t p - — m so os m — Tt tN fN 00 ON p -rn rn fN --^  in ON © T t p-in oo m rN oo © ON so © - H © © Os os m Tt r- © p- rn so © © © © © © so p p^ ON T t SO T t WTi T t SO os ON T t ° 2 m T t i-H oo so "2 -H >n 2 2 2 o" ^ 2 O P- P~ O © © Tt tN r~~ T t p~ cn so so tN Tf cn o T t ON cn m cn tN © © © o © © © © © ' © © ' © T t so — P-© r t cn oo (N in OS Os ini cn Tt so < < < < < < < < < o n f f l n o n o a n M ts H U O U U U C J U U U U Q Q Q Q Q Q Q 256 Appendix Minor rock forming elements (mg/kg) Zr Sr Pb Ni Co Cr Ba Cu Mo Zn m T j - r - o c N O o S 0 0 — f", — — CN — 7 tN i n ^ - c o S S o r - t 2 < * 8 2 : p ! 8 - - : 2 ! - - 2 2 — — ^ v O - t f M - v O V O - a ~ •» s -Major rock forming elements (%) Fe Mn Ti Ca K Si Al Mg P S Na 3.154 0.116 0.324 1.873 0.971 31.701 6.526 0.766 0.044 0.240 1.719 2.518 0.054 0.282 1.701 0.880 33.665 6.637 0.681 0.035 0.160 1.859 3.644 0.062 0.324 1.930 1.146 30.823 7.579 0.874 0.057 0.290 1.680 7.344 0.023 0.252 3.173 1.685 22.325 7.462 1.158 0.144 1.490 0.751 5.575 0.023 0.282 1.015 1.387 28.729 7.896 1.073 0.092 0.795 1.101 6.743 0.016 0.252 3.216 1.320 22.544 7.425 0.742 0.148 3.300 0.656 3.756 0.047 0.324 1.815 1.254 30.827 7.854 0.856 0.031 0.430 1.623 3.917 0.031 0.306 2.251 1.486 29.028 7.902 1.073 0.035 1.180 1.362 5.763 0.031 0.288 1.923 1.478 27.574 7.547 1.122 0.092 1.450 1.133 3.182 0.031 0.282 1.651 1.494 29.687 8.061 1.260 0.048 1.120 1.413 2.994 0.000 0.318 1.615 1.710 29.000 8.934 0.302 0.052 1.540 1.152 7.141 0.016 0.306 1.887 1.553 22.951 8.225 0.422 0.135 2.430 1.063 7.043 0.016 0.306 2.251 1.528 23.157 8.505 0.386 0.140 2.930 1.222 5.882 0.016 0.318 2.058 1.528 25.087 8.685 0.645 0.087 1.970 1.483 3.966 0.008 0.312 1.830 1.553 27.317 8.960 0.519 0.044 2.700 1.178 2.966 0.016 0.300 1.851 1.486 29.299 7.875 0.983 0.044 1.175 1.298 3.987 0.031 0.306 1.437 1.237 30.813 7.722 0.977 0.048 0.550 1.547 3.903 0.070 0.318 2.101 0.980 29.617 7.796 1.465 0.048 0.460 1.311 3.840 0.062 0.282 2.208 0.971 29.514 7.822 1.447 0.044 0.490 1.349 3.994 0.093 0.372 2.437 0.938 29.065 7.399 1.260 0.039 0.540 1.318 3.322 0.093 0.306 2.902 0.805 29.018 7.462 1.387 0.039 0.610 1.171 3.861 0.062 0.378 2.630 0.922 28.757 7.754 1.303 0.039 0.860 1.356 4.616 0.101 0.300 2.087 0.988 29.612 7.277 1.291 0.087 0.500 1.197 3.826 0.077 0.270 1.722 1.038 30.309 7.701 1.411 0.044 0.285 1.216 4.169 0.077 0.288 1.451 1.071 30.673 7.717 1.375 0.066 0.290 1.292 4.113 0.054 0.318 1.608 1.162 30.439 7.939 1.297 0.044 0.450 1.343 4.917 0.047 0.318 2.080 1.054 28.495 7.473 1.321 0.061 1.060 1.248 4.826 0.031 0.312 1.144 1.503 28.116 8.780 1.351 0.066 0.815 1.521 4.211 0.023 0.222 0.872 2.134 28.336 7.642 0.874 0.083 3.000 0.897 4.511 0.070 0.294 1.458 1.503 28.453 8.330 1.272 0.070 2.170 1.553 5.882 0.031 0.294 1.994 1.403 27.153 7.881 1.128 0.048 2.200 1.133 6.015 0.023 0.270 1.279 1.362 27.223 7.849 1.092 0.083 3.300 1.158 3.882 0.031 0.204 0.679 2.233 29.617 7.129 0.808 0.044 3.500 0.656 4.567 0.031 0.306 2.137 1.885 27.551 8.087 1.278 0.022 1.720 0.624 Is S. < < < < < < < < < CQCQfflfflCQCQfflm 3 3 S 5 D ^ - 5 u u u u u u u u u u Q Q Q Q Q a a e l l ^ ^ ^ M o ^ Q - N n ^ l o ^ ^ M O ^ O - f ^ M ' t l f l « ^ l l o o ^ Q « N w t l ' l > o ^ [ S 257 Appendix Acid Ammonium Oxalate and Citrate Bicarbonate Dithionite Extraction Data 258 c o o CO c- .ti -Q I § 1 u (8 -p 3 c T3 — 5 nj * <D J3 o 2 E ° CO o !o Q) 5 I g ^ i g l l g l § i i l | § i g l l l i i g g i l 8 i § g § 8 g l ^ o o o O J O J o ^ ^ S o o g o o ^ o o j ^ o o o d o o o o o o o o o O o J O O i i i ! l ig!Sl i IES8i iSi i i i iS i i i i8 i !8 i i i I s i S i i i i i H S i i i i i i s i s i i i i s i M s i s i i s i l l l l l l l l l l l l II 111 I l H l l I I I I I I | | i f § l s 5 1 1 3 8 S 8 i 3 | g ! 5 i 5 S § i l S S S S 2 S § ^ | 5 2 | a ! l l ! l ! ! I l l ! l l I I l P l ! l i l i l l l l l ! l l l ! l l l < < < < < < < < < C D a 3 C Q C D C Q C D C Q C 0 O O O O O O O O O O Q Q Q Q Q Q Q ^ o j O ' t i n ( D N t D o i ^ r . r r i . ^ ^ ^ ^ r 0 ] n ] O J ( N O J ( N f l ] w a | 0 i n n „ n ( j ) 259 Appendix c o o ro •R dt 0 £ =. c 1 c E ° ( U S D w £ CD o la o aj 5 Si i i i i i l l i i i i i g i i i i i l i l i i l l i i l iS i i i T3 c co C/J < it 3 OJ X ° = = = » E o w re CO ^ X B c 0) CL CL < 1 § ^ S S § ™ § § 8 J 8 8 8 ^ 8 ^ 8 § § 8 ^ 8 ^ | 3 ? l S a S s l 8 | g i S S 8 s s | | S 5 ? § ! g R R g | a | | 8 a 8 i l l l l l l l l l l l l l l l l l l l l i l l l l l l l l l l l ! ! < < < < < < < < < C D C Q C D C D m c D m [ D O U Q U U O O U U O Q Q Q Q Q Q D 260 Appendix Sequential Extraction Data 261 Appendix O O O O O O O O O O O O O O T T d d o d d o o d d d o d d d d i o o o o o ,5 o o o o o o o o o o o o o o o o o o o 2 o o o o o o o o o o o o o o o o o o o I l l l l l l l l l l l l l l l l l l l l g CO m r- CO C4 r- r- CO O) CO JJ O O O O O O ^ q C ^ M C ^ J O . O r O O O O O J- o o o o c o o o T - m o o o o r * - < O i - T f O ' -" — ^ §ig§i i i ! i i l i§! l i ! i i ! c o < o « ^ c » 2 c o c o a , . 0 c o c o < o c 0 u , ^ o c o S S c ^ ' S ' S S ^ ^ ^ S S S S S d 0 ^ 0 r f ) o o r > o o co o ( o o o o o o o o o o * row*r-o)noiifiintDioinc3)(j)inT-»-nt\io Q O t O l O O C M C M C M C O ' > - C O C M < N ' i - C O i - C O O c ; T - d d d d d d d d d d d d d d d d 2 I O O CO O O O I M C M W C M W O O C M O I O O O J O O C J O O O S i S S S S i i l i i i i H S S i l ' i J3331IIlIIIlia3133i? i t o 111 r o o o o o o o o o o o o o o o o o c n o i t u i r o N o o o K K o o N i n o i S N g o n n | ( D l O m O > 0 1 0 C O ( M ( \ | T - i - O T t t t O O co J i-CNJCNJCSJCNJCVJCMCVJCNJ OJIO -C LU > ? o I ZL o 111 LU q^cvjmtnaaoooaaoOTOTOT^i-ooaoa^r^oji- ^ m i o r o i D o n o N S ^ ' t t o v T- o O ^ ^ i - d T - c i i r i i n L n ^ L O T t ' i n i r i o d i f i n b c i d o d d T - d o a r i ' t V r o r - c J c i d ^ _J CO T- r - r- r- r-W _ 3 ^ : : O C 0 C l ) N N ' j T ^ ( M 5 - 0 ) C M W n ^ ' - ' - ^ Q a i i — Q Q O Q O O O O O O O T — T - O C D O C O O O Q r o r o o i w m c n o i t i & m f i o i o o o c i o o ) o o o o i o m i n m m c o o o o a c D O c n o o N in ~ o m m o m m i n c o c o c M c o o ) w c o c O ' j c o i - ' - i - i - > - - * m > -co 2 3 m i o t O L n L O i j O i n i n m i o i o m i o r ^ r ^ ^ t r ^ ' - ' i - ' - C M C M r ^ r t i r ^ r * -co co co T - : T _ : a > L o o d ( D CT) O O CO CO ^ T— T— CO CO CO *- T - CM CO — cn CM CM O O O O O O I LL — i r i t b *^ T— CM co TJ LO to "~ i r i t d ^ ^ w o ^ w (D QC 3 T- CM CO 3 3 O H CC CC U + LU LU LU _ + T- OJ CO £ cc oc cc cc 3 5 5 LU LU LU O 262 l O W N C D C O l D N N S N n L n ^ i - c D L n O O ^ o o o o o o o o o o o o o o o c o r o o o T - T - T - O O O O O O O O O O t D f ^ n (jj Q Q c d o o b b d d d d d d d d d d «-N N O O O O f M O O O O O O C M C M O O O O O O O O O O O C I I I s f I r ^ * P ) O O O O O O O W N P I ' - « « O ! 0 U O D t O O O T - O O O O O t O n t D i n O O t D ^ C O ' T ^ ^ O O oocjcjcboj c T - T - c \ i c j d d d 6 -^ o c o u c T-^1-1-»-,-,-T-»-T- »~ T- »~ O T~ in in T-i - W N S 0 ) O 0 ) ( 0 N f N n O r ( 0 0 ) O O O T - T - i- w > - I D n i- i-i-T- i-coco < ^ T- CO CM _1 t l O N f f l O O O O O v M l M O O N N ^ O C M O CD t t Tt -^ in m ^ tt to i i i i i i i l i i l l i l i l l l l § § l i § i § i § i i § l § § § § l § * £ lIIIIIIIlIIIIIIIIIll £ I B1 ,1 tl. tl. IPsiHPI! IH81IlIgiIS . r n « r r K c S g g g g g g ^ . r B „ r r „ » S g g g g g g : CM co 3 o J E in tc cc D J 5 5 LU LU LU O 5 5 L U L U U J O 263 Appendix o o c M i o o o o o o o o c o m o o c o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o z z o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o CM CM O O CD o o o o o o o o o o o m o o o o o o o o o o o o o o o o o o o o o o CM i-S t 8 8 8 8 8 i r i ^ u i i ^ ^ ^ W c M C M r ^ i ^ ^ ^ i r i ^ ' i r i ' ^ ' i r i i r i E | w 5 3 m m m m m m m m m m w m m i ^ i ^ T r i ^ T - T - T - c M C M r ^ f v i r ^ r -n n « T _ T ~ Q O i n c d Q d m i n m o m m m m m m m m m C M C M N O T - S N | v . S N S r v S co cb S enej>enen"£cnen CM CM O O O O O O • CM CO TT l/) CD O „ . + CM cn £ £ rr rr rr =i 2 2 LU UJ LU O 264 Appendix rtoooNnri00*Nr\jnnoifloc\iooo c \ j o o o ^ o o ^ 0 o 0 T - ^ O T r o o o o o c d d d d d d d d d d d d d d d d d d tziodo<zi<zi<zi<zi d d d d d d o o d d N f5 o o o o o o o o o o o o o o o o o o o o * |l|llll!llllplls5is * « i » s 8 E g ^ * ? r s r o " " S 5 s 8 S 3 3 S S 5 S 3 5 - S S S r i ° 1 1 1 1 ^ ^ * 3 S S 1 5 S 1 1 ! | S 5 5 " 2 S 5 S 5 S 5 " S c d " " 0 " 0 0 0 " *" 2 " " : " S " 5 S " " S S ° S ° " ° c 5 o o o o N n n o m w t N w o o o w o n o < O O O O W N t M O O O O C O O O O O v N O m O O) I c «J °3 c •g < "6 i f s l S3S83S5SSS335355S333 SSSSjiSSSSSSIS'SSSSi iigiiiiPiiiiiiiiii^* mmmmmmm fit £ I a s a s ll. Ii. I ls|iaaa-gg-55 ^ | 5 J j s a a - y - 5 5 I I 5 5 5 I I 5 5 5 5 5 8 g a a S S 8 S 8 i 5 g 8 g g g g g g ? ? 8 | 3 8 S S 8 £ 8 ft £ g g g S g g g 9 9 i »- CN co CC DC r£ tr DC 2 S LU LU LU 265 o CO > <y .c > co g o o 8 B H "o „ + -^ CM n in 13 = o . LT r r r r r r LT 3 a . 2 LU 5 2 LU LU LU 2 LU Appendix O *~ T-o o o o o o o o O O O O O O O O O i - O O o o o o o o o o o o o o o o o o o o o o o o o O O O O O O O C M C M C M O O O O O O O O O O •CDCOCMCO-^CMOOCM • O O O O O O O O O O . CO CO . CM « cO ^ *- •* o o o o o o o o o o o o o o CM CM l — l — . ) ( O i O i - c O C O r ^ i O C M i m c o ^ o c o o j t c o ^ O O r 0 0 d o o o o o o o o o ' W t T ) ^ w c \ i c o t N i n N c o w o j O ) N < a c o { v j c \ i ( \ j o i O t D ( D r ^ 0 ^ c o c M C O ^ ^ ^ c q q 0 c M i - O O i - O O ' - ' - o o o m c o o i O T - c y r ^ r ^ o o c o c \ j r ^ r ^ c D « > c M c O ' * ( - r~- o o co - 9 « JL y c D ^ ^ ^ L i O T + m ^ r ^ a ) T f c y ^ r ^ ^ r - ~ h - c o c D c o -2 g ^ ^ ^ ^ " ^ « T f f ^ i < i r i ! 2 S o c & c o " c \ j ' - ' - - * a ui i f in inojNif lc j i -co i i iof f lc j i f l io i f ios io t o ER • <D O O r - CM l "ci E S i - O O Q O O Q O Q O O O O O O O O O g 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 o o o o o o o i n i n i o o o o o o c o r ^ o o i n j c o c o m m m i n i n i n m m m ^fs^'rtcor^r^r^i^r^r^f^f^-r--c o o o " " o d ^ ^ a D c o c o i n ^ ^ " " ^ C M C M ^ ^ CO CO ad ad in m M n N M n m i n i n i n w i f i i n i n CDpv.lOlOS^tyjCMCUCMClNN CO C O C O 1 - 1 irtirt CO (O (O i n i n c o c o i n i o m m m i n i n m i n ^ r o " " o 3 ^ ^ m c o c o i o c ? c ? § S W W CM CM r ^ m r ^ r ^ m L O L n m m i n m L n m > 00 <g <g CO CM CM CD <D CD CD eq eo ™ ™ CM CM CM -^CMCO^LOCOh-_ + T- CM CO W "D fC CC cc cc cc 3 Q_ 2 2 LU LU LU 2 LU _ + T - CM CO (ft "D £ cc cc LX CC ^ D. 2 2 LU LU UJ 2 LU 266 O O O O O O O O O O O O O O O C O O O O O c N o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o c 3 o o o < CO z i n m c A j m o m t n o c A j o i n o o t o c D o m o c M t d « d ^ «? P d CM CM CM «N Sg iri O O O CM o o o o o o o o o o o o o o o m o o o i o d ^ CO O N o ' r : r - ' o i n 6 i n i r ) i n 6 a " n r : ' : c d i- i- d o d d d o a> 2 o o * - * - o o o o o o o o o o o w o o o o CO > o o in o > CM CM Tt-Q CQ t o m m o m m m m o m m i n i n m i n o m m c o m cM r^^ mr^ ^cMcym«^cMrv:^ cM°CME5 CM CJ) CO CO CJ> CM CO CD CM ^ U"> ~ •r- ^ CM s I > iS £ •l a LU 3 o w u i t - i / i c f i i n i t i c n o c D O T ^ w c n c o i n ' - O ) > • 1 • >- • CM co 1 Y LU _ O 59 S 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 - 0 0 i n i n u i i n i n i n o o o i n i n i n i n i n i n i n o i i n ^ a> £ g « 2 3 CDC0f^ C^0"OC0C0C0l0C0C? $ g CM CM CM CM ~ CO CO = r*LOr*t*-miommmi/)iOLnLn C D ^ C D C O r ^ r y n J C M C M C M C O h - h -- - C M o C M W r i C M C M ^ C M C M ^ ^ l 0 K t n K j n K CM CM CM C M i - C M C O ^ t L D C O r -„ , ± T - CM CO cc cc rr rr rr 5 5 LU LU LU 267 0 " -g 2 LU Appendix Appendix Wet-Dry Experiment Data 268 mg/L mg/kg (g) Cycle Sample [S04] [S04] Jo L O E pH 1 A 302 6048 0.00 3.80 2 A 41 823 0.00 3.96 3 A 30 606 1.02 3.86 4 A 32 648 0.51 3.79 5 A 32 636 1.02 3.76 6 A 33 667 1.02 3.75 7 A 36 720 1.52 3.53 8 A 42 832 1.52 3.49 9 A 36 719 1.02 3.49 10 A 32 637 1.52 3.57 11 A 34 681 1.52 3.59 12 A 32 638 2.54 3.61 13 A 27 533 11.68 3.59 14 A 26 520 12.69 3.58 15 A 24 489 12.69 3.60 16 A 25 499 14.21 3.58 17 A 24 490 13.20 3.60 1 B 260 5195 0.00 3.35 2 B 24 485 0.51 3.48 3 B 12 238 0.00 3.77 4 B 8 155 0.00 3.94 5 B 4 79 0.51 4.09 6 B 4 78 0.51 3.98 7 B 4 70 1.54 3.92 8 B 3 63 2.05 3.78 9 B 3 62 1.54 3.87 10 B 3 64 2.05 3.98 11 B 2 47 1.54 4.02 12 B 2 47 3.08 4.07 13 B 2 32 3.08 4.07 14 B 2 44 2.56 4.04 15 B 2 42 1.54 4.07 16 B 2 43 2.56 3.98 17 B 1 21 1.54 4.03 1 C 1523 30454 0.00 2.97 2 C 1532 30637 3.02 3.08 3 C 1452 29044 8.54 3.15 4 C 540 10803 14.57 3.36 5 C 65 1308 17.09 3.36 6 C 36 711 18.09 3.44 7 C 23 466 18.59 3.32 8 C 19 371 18.59 3.28 9 C 17 344 18.09 3.35 10 C 15 298 18.59 3.47 11 C 11 227 19.10 3.47 12 C 12 246 19.60 3.55 13 C 10 202 19.10 3.55 14 C 9 175 19.60 3.53 15 C 8 168 19.10 3.54 16 C 9 187 20.10 3.48 17 C 8 150 19.10 3.52 1 D 1499 29983 0.00 3.51 2 D 1169 23382 4.00 3.52 3 D 104 2082 9.00 3.81 4 D 14 272 8.50 4.28 5 D 7 142 9.00 4.11 6 D 5 99 8.50 4.11 7 D 7 145 9.50 3.94 8 D 4 77 10.00 3.83 9 D 4 87 9.50 3.85 Appendix (|imhos/cm) E C 255 560 266 110 303 80 304 90 306 89 311 . 81 306 102 297 114 318 100 324 88 320 102 324 90 325 85 312 79 320 80 327 73 322 70 469 550 410 100 408 50 383 36 363 27 374 27 352 25 332 22 361 21 360 20 357 19 366 16 351 18 352 15 351 15 351 15 337 13 458 2300 467 2150 463 2000 445 1000 425 220 416 161 394 125 369 105 388 92 387 82 384 78 357 80 376 68 379 64 376 62 380 64 367 55 399 2100 405 1700 393 230 374 42 369 31 361 28 347 25 331 24 354 22 269 Appendix mg/L mg/kg (g) ((imhos/cm) Cycle Sample [S04] [S04] % L O E pH Eh EC 10 D 3 67 10.00 4.05 354 19 11 D 2 44 10.50 3.99 355 19 12 D 2 47 11.00 4.07 348 18 13 D 2 48 9.50 4.06 349 17 14 D 2 49 10.50 4.13 347 16 15 D 2 39 10.00 4.09 345 15 16 D 2 33 11.00 4.06 350 15 17 D 1 24 10.50 4.09 339 13 1 E 1611 32219 0.00 4.15 386 2150 2 E 1512 30242 4.06 4.06 378 2000 3 E 1308 26165 10.15 4.05 389 1900 4 E 1054 21085 15.23 4.50 373 1550 5 E 167 3344 19.29 4.22 374 340 6 E 43 855 20.30 4.24 362 111 7 E 21 411 20.81 4.04 351 63 8 E 15 302 20.81 4.08 337 46 9 E 15 299 20.30 4.13 355 40 10 E 11 212 20.81 4.25 352 34 11 E 7 147 20.81 4.38 350 29 12 E 8 161 22.34 4.33 350 29 13 E 5 106 20.81 4.49 338 23 14 E 5 101 21.32 4.41 343 20 15 E 4 88 21.32 4.47 339 24 16 E 5 98 21.83 4.40 347 21 17 E 4 73 21.32 4.49 331 18 1 F 78 1550 0.00 4.61 374 650 2 F 31 621 0.00 4.73 352 800 3 F 12 245 2.02 5.49 343 28 4 F 5 102 1.01 5.78 322 19 5 F 3 67 1.01 5.24 340 14 6 F 3 57 2.02 5.43 320 14 7 F 2 47 2.53 5.18 321 12 8 F 2 37 2.53 4.72 314 9 9 F 2 49 2.02 5.31 317 11 10 F 2 49 2.02 4.98 325 9 11 F 2 39 2.02 5.25 326 9 12 F 2 35 3.03 5.18 325 8 13 F 2 35 2.02 5.21 320 7 14 F 2 37 2.02 5.09 332 7 15 F 1 26 2.02 5.10 323 7 16 F 2 33 2.53 5.14 329 7 17 F 1 23 2.53 4.97 329 6 1 Z 0 0 4.84 320 3 2 Z 0 -6 4.70 298 2 3 Z 0 -6 4.98 386 2 4 Z 0 -6 5.01 390 1 5 Z 0 0 5.20 375 2 6 Z 2 32 4.68 372 1 7 Z 1 28 5.23 354 1 8 Z 1 29 4.42 298 2 9 Z 1 27 4.69 397 2 10 Z 1 22 4.53 410 2 11 Z 1 11 4.41 412 1 12 Z 1 18 4.30 394 2 13 Z 1 17 4.49 376 2 14 Z 1 20 4.40 385 2 15 Z 1 18 4.40 377 3 16 Z 1 17 4.36 403 2 17 Z 1 11 4.23 412 2 270 Appendix Al Cycle MR (A) 2(B) 9(C) 16(D) 27(E) 33(F) 1.00 236.80 99.42 178.72 139.36 24.52 490.40 2.00 38.74 3.87 72.72 22.38 16.87 337.32 3.00 49.71 1.36 34.49 0.60 10.31 206.20 4.00 62.34 0.74 8.62 0.05 5.80 115.99 5.00 67.30 0.00 0.11 0.00 1.34 26.89 6.00 69.09 0.00 0.00 0.00 0.00 0.00 7.00 79.17 0.00 0.00 0.00 0.00 0.00 8.00 95.26 0.00 0.00 0.00 0.00 0.00 9.00 79.62 0.00 0.00 0.00 0.00 0.00 10.00 66.38 0.00 0.00 0.00 0.00 0.00 11.00 71.91 0.00 0.00 0.00 0.00 0.00 12.00 68.36 0.00 0.00 0.00 0.00 0.00 13.00 53.93 0.00 0.00 0.00 0.00 0.00 14.00 47.25 0.00 0.00 0.00 0.00 0.00 15.00 47.59 0.00 0.00 0.00 0.00 0.00 16.00 48.84 1.31 0.82 0.80 0.60 12.08 17.00 45.66 0.27 0.00 0.00 0.00 0.00 Ca Cycle MR (A) 2(B) 9(C) 16(D) 27 (E) 33 (F) 1.00 1130.60 1523.8 12790.00 12882 11004.00 1138.6 2.00 118.72 92.72 10710.00 6526 11892.00 90.46 3.00 50.84 28.1776 11467.07 864.625 6913.02 12.8636 4.00 29.10 14.7012 5152.53 86.3704 5676.57 10.4134 5.00 24.43 11.5061 462.44 38.6555 1504.46 12.1526 6.00 14.32 8.18045 189.95 23.5789 351.52 7.09774 7.00 10.35 6.85714 106.35 19.1278 162.05 6.37594 8.00 11.43 7.21805 72.18 17.9248 115.25 5.41353 9.00 9.38 6.85714 56.54 15.8797 95.52 6.49624 10.00 6.50 7.33835 46.08 14.3158 79.40 5.05263 11.00 8.54 6.73684 41.74 14.4361 69.89 5.05263 12.00 7.94 6.01504 36.93 10.7068 64.24 3.24812 13.00 3.85 4.81203 27.07 8.54135 52.21 4.21053 14.00 5.29 6.49624 28.63 12.0281 42.47 4.21053 15.00 43.11 5.81771 25.73 10.2133 43.31 3.61991 16.00 5.24 5.594 25.52 10.14 42.66 3.846 17.00 5.65 5.338 21.66 9.106 35.80 2.512 Cu Cycle MR (A) 2(B) 9(C) 16(D) 27 (E) 33 (F) 1.00 1.38 135.44 200.60 103.26 531.00 1614.8 2.00 1.83 10.27 24.02 9.72 205.80 155.62 3.00 0.00 5.478 10.85 2.4002 109.08 50.5906 4.00 0.08 3.3118 5.13 0.3846 53.32 34.9508 5.00 0.15 2.00371 1.90 0.20037 27.20 30.9072 6.00 0.00 1.42892 0.64 0 19.71 23.8975 7.00 0.00 1.52747 1.68 0 13.30 24.5873 8.00 0.00 0.54201 0.25 0 11.97 23.2077 9.00 0.00 1.86837 0.59 0 12.86 23.0106 10.00 0.00 0.39419 0.00 0 10.15 21.3846 11.00 0.00 0.24637 0.59 0 9.76 20.744 12.00 0.20 0.39419 0.84 0 11.63 20.9904 13.00 0.00 0.19709 0.74 0 8.62 19.2166 14.00 0.00 0.04927 1.03 0 6.95 18.7238 15.00 0.00 0.95176 1.35 0.40074 8.17 18.935 16.00 0.12 0.936 1.37 0.188 9.05 17.922 17.00 0.43 1.55 0.93 0.248 8.12 17.606 271 Appendix Fe Cycle 1.00 MR (A) 516.80 2(B) 15.744 9(C) 175.34 16(D) 49.36 27(E) 0.76 33 (F) 0.046 2.00 38.10 1.466 38.30 4.02 0.22 0.244 3.00 59.16 0.9782 22.39 0.7836 0.08 0 4.00 94.15 0.6986 9.80 0.3922 0.19 0.2896 5.00 122.42 0 3.83 0.00182 0.13 0.1294 6.00 121.48 0.36392 2.66 0.00429 0.12 0.00177 7.00 142.44 0.00272 2.17 0.12497 0.00 0.00195 8.00 138.82 0.24396 1.81 0.00351 0.00 0 9.00 133.89 0.12338 1.45 0.12501 0.00 0.3611 10.00 119.07 0.12384 1.69 0.12496 0.24 0.00217 11.00 139.31 0.24455 1.45 0.00437 0.00 0.00232 12.00 116.90 0.36212 2.05 •• 0.2447 0.00 0.12295 13.00 98.46 0.12386 1.33 0.36201 0.12 0.00235 14.00 92.44 0.36449 1.81 0.00368 0.12 0.2436 15.00 95.91 0.26343 1.32 0.26522 0.00 0.13176 16.00 81.02 0.69 1.85 0.692 0.00 0 17.00 92.70 0 1.48 0 0.00 0 Cycle 1.00 K MR (A) 600.00 2(B) 4 9(C) 2.00 16(D) 2 27(E) 20.00 33(F) 14.00 2.00 78.00 2 2.00 2 8.00 6.00 3.00 38.00 2 2.00 2 10.00 4.00 4.00 16.00 2 2.00 2 8.00 4.00 5.00 10.00 4 2.00 2 6.00 4.00 6.00 14.00 4 2.00 4 6.00 2.00 7.00 8.00 4 2.00 0 2.00 2.00 8.00 6.00 2 2.00 4 0.00 2.00 9.00 6.00 4 4.00 4 2.00 2.00 10.00 4.00 4 2.00 2 2.00 2.00 11.00 6.00 2 4.00 2 2.00 2.00 12.00 8.00 4 4.00 2 2.00 2.00 13.00 4.00 2 4.00 2 2.00 2.00 14.00 8.00 2 4.00 2 2.00 2.00 15.00 8.00 2 10.00 2 2.00 2.00 16.00 8.00 2 4.00 2 2.00 2.00 17.00 6.00 2 4.00 2 2.00 2.00 Cycle 1.00 Mg MR (A) 203.80 2(B) 264.8 9(C) 71.40 16(D) 97.04 27 (E) 410.60 33 (F) 237.8 2.00 36.14 17.074 10.14 5.414 72.76 18.442 3.00 22.54 6.5692 1.84 1.4566 10.51 4.8214 4.00 . 19.37 3.7072 1.12 1.9428 3.30 2.5212 5.00 15.64 5.52543 5.88 4.54115 4.03 5.13763 6.00 7.81 0.45907 0.00 0 0.00 0 7.00 7.91 0 0.00 0 0.00 1.79365 8.00 8.66 1.38408 0.10 0 0.32 0.26348 9.00 7.78 2.0413 2.06 0.41533 1.73 3.56703 10.00 6.34 2.38157 1.02 0.9014 1.27 1.11487 11.00 6.97 1.48204 1.94 1.67954 2.34 2.47674 12.00 6.51 0.79975 0.00 0 0.00 0 13.00 0.67 0 0.00 0 1.12 2.35619 14.00 4.52 2.52745 2.33 1.40605 1.82 2.89089 15.00 3.47 0.80931 1.75 0.7606 1.98 2.98961 16.00 4.07 2.202 1.26 1.346 1.14 1.874 17.00 4.19 Mn 0.954 0.36 0 0.00 0 Cycle MR (A) 2(B) 9(C) 16(D) 27(E) 33(F) 272 Appendix 1.00 39.92 69.66 21.62 17.26 161.84 209.4 2.00 6.29 5.458 4.57 0.956 26.76 15.31 3.00 3.11 1.8866 1.08 0.1582 3.47 2.7872 4.00 2.46 1.154 0.62 0 1.48 1.5698 5.00 2.90 0.73218 0.15 0 0.57 1.81281 6.00 3.14 0.32247 0.00 0 0.00 1.01899 7.00 2.87 0.23718 0.00 0 0.00 0.81491 8.00 4.96 0.16997 0.00 0 0.00 0.67784 9.00 3.55 0.07757 0.00 0 0.00 0.89817 10.00 1.55 0.08854 0.00 0 0.00 0.52148 11.00 2.67 0.0595 0.00 0 0.00 0.4439 12.00 2.12 0.27069 0.00 0 0.00 0.36126 13.00 0.98 0 0.00 0 0.00 0.29079 14.00 1.15 0.01097 0.12 0 0.00 0.23454 15.00 1.80 0.29799 0.07 0 0.04 0.5428 16.00 1.74 0.33 0.14 0.008 0.10 0.542 17.00 1.17 0.262 0.04 0 0.01 0.408 Na Cycle MR (A) 2(B) 9(C) 16(D) 27 (E) 33(F) 1.00 152.00 0.4 4.00 2.2 8.40 197.4 2.00 17.20 0 1.40 1.6 2.80 19 3.00 8.40 0 1.20 1.2 3.00 2.8 4.00 4.40 0.4 0.40 0.6 2.00 0.6 5.00 2.60 0 0.00 2 1.00 0 6.00 3.80 0.6 0.00 2.4 0.40 0 7.00 1.80 0.6 0.00 2.2 0.00 0 8.00 1.40 1 0.20 2.6 0.00 0 9.00 1.80 0.8 0.60 1.8 0.00 0 10.00 0.80 0.6 0.60 1.4 0.00 0 11.00 1.40 1 1.20 1.6 0.00 0 12.00 1.80 1.2 1.60 1.4 0.00 0 13.00 0.40 0.4 1.20 0.6 0.00 0 14.00 0.20 0.4 1.60 1.8 0.00 0 15.00 0.20 0.4 1.60 1 0.00 0 16.00 1.40 1.2 2.20 0.8 0.00 0 17.00 0.00 0.4 0.80 1.6 0.00 0 Ni Cycle MR (A) 2(B) 9(C) 16(D) 27(E) 33 (F) 1.00 2.25 0.638 0.20 . 0.446 0.17 0.77 2.00 0.37 0.048 0.55 0 0.01 0.054 3.00 0.70 0 0.39 0.0746 0.12 0.0044 4.00 0.73 0.0746 0.01 0 0.16 0 5.00 0.73 0.07164 0.07 0 0.03 0 6.00 0.37 0 0.00 0 0.00 0 7.00 0.68 0 0.00 0 0.00 0 8.00 0.70 0 0.00 0 0.00 0 9.00 0.55 0 0.00 0 0.00 0.07516 10.00 0.45 0 0.00 0 0.00 0 11.00 0.57 0 0.00 0 0.00 0 12.00 0.41 0 0.00 0 0.00 0 13.00 0.32 0 0.00 0 0.00 0 14.00 0.29 0 0.12 0.2051 0.00 0 15.00 0.34 0.04953 0.00 0.06876 0.01 0.11828 16.00 0.41 0.112 0.05 0.06 0.00 0.034 17.00 0.42 0 0.00 0 0.00 0.034 Si Cycle MR (A) 2(B) 9(C) 16(D) 27(E) 33(F) 273 1.00 20.24 8.614 17.27 7.34 38.64 5.448 2.00 16.81 9.438 18.49 6.932 42.18 6.344 3.00 12.99 0.5106 16.81 9.7306 27.04 4.137 4.00 15.71 13.0478 23.52 11.9696 30.64 3.7396 5.00 16.19 12.9405 22.56 11.6603 35.67 5.57071 6.00 10.88 13.1313 20.76 10.3461 31.50 5.43883 7.00 12.07 12.5675 22.88 11.0092 30.21 5.23991 8.00 12.00 12.7334 24.27 10.4124 30.54 4.64305 9.00 9.22 12.3687 24.14 9.68295 29.84 5.13964 10.00 13.13 13.496 29.41 11.2745 32.66 4.44412 11.00 13.86 14.5571 30.41 11.8382 30.47 4.842 12.00 12.40 13.7273 28.09 10.0476 29.08 4.57672 13.00 12.20 13.0981 29.01 10.4124 30.97 4.11253 14.00 14.33 13.3966 31.27 11.8049 27.36 3.78095 15.00 14.43 12.8367 32.66 11.2797 27.71 4.25593 16.00 9.99 11.512 24.54 9.992 21.94 3.91 17.00 12.03 11.676 28.98 10.344 25.20 3.738 Zn Cycle MR (A) 2(B) 9(C) 16(D) 27(E) 33 (F) 1.00 3.21 4.956 3.06 2.67 8.55 20.14 2.00 0.55 0.592 0.59 0.266 1.99 1.426 3.00 0.59 0.2906 0.44 0.0748 0.80 0.3976 4.00 0.86 0.2302 0.13 0.0528 0.50 0.2932 5.00 0.77 0.04537 0.00 0 0.09 0.12707 6.00 0.71 0 0.00 0 0.00 0 7.00 0.85 0 0.00 0 0.00 0 8.00 1.14 0 0.00 0 0.00 0 9.00 0.86 0 0.00 0 0.00 0.02361 10.00 0.49 0 0.00 0 0.00 0 11.00 0.68 0 0.00 0 0.00 0 12.00 0.57 0 0.00 0 0.00 0 13.00 0.26 0.16692 0.00 0 0.00 0 14.00 0.27 0 0.00 0 0.00 0 15.00 0.39 0.02245 0.00 0 0.00 0.0092 16.00 0.49 0.102 0.07 0.064 0.22 0.186 17.00 0.45 0.08 0.04 0.006 0.05 0.118 /kg) (blank corrected) Cycle MR (A) 2(B) 9(C) 16(D) 27 (E) 33(F) 1.00 6048.31 5195.27 30454.46 29983 32218.79 1550.1 2.00 829.14 491.48 30643.04 23388 30247.59 626.846 3.00 611.64 243.561 29049.97 2088.5 26171.38 251.166 4.00 654.22 160.606 10809.54 278.543 21091.32 108.081 5.00 636.00 78.7879 1308.27 142.424 3344.01 66.6667 6.00 635.10 46.25 679.75 67.5 823.50 25 7.00 692.27 42.5 437.93 117.5 382.92 18.75 8.00 802.64 33.75 341.81 47.5 272.44 7.5 9.00 691.93 35 317.20 60 272.55 22.5 10.00 615.60 42.5 276.75 45 190.00 27.5 11.00 670.66 35.7742 215.84 33.3892 135.94 28.6193 12.00 619.81 28.6193 227.76 28.6193 143.10 16.6946 13.00 516.74 15.5021 184.83 31.0043 89.44 17.8871 14.00 499.36 23.8494 155.02136 28.6193 81.0881 16.6946 15.00 471.079 23.8494 150.251472 21.4645 70.3558 8.3473 16.00 482.238 26.2344 170.523496 16.6946 81.0881 16.6946 17 479.001 10.7322 139.519224 13.1172 62.0085 11.9247 274 Appendix Batch Experiment Data 275 Appendix (mg/L) A B C A B C ID Element Day DDW HOAc HN03 Cit-lowpH cit-medpH cit-highpH 2 Al 0.04 2.95 5.2 5.8 4.588055 7.667335 8.25569 2 Al 0.08 0.38 1.98 2.31 5.609365 6.71465 8.93862 2 Al 0.25 0.14 2.28 2.18 3.696 9.4253 7.079528 2 Al 1 0.03 3.56 2.77 6.199483 7.96077 12.07248 2 Al 3 0.05 2.5 2.39 12.65593 37.08931 51.142995 2 Al 9 0.15 4.5 3.39 18.22644 33.417155 26.6454633 2 Al 20 0.16 5.95 3.98 31.41721 23.92942 16.170645 2 Al 41 0.12 6.56 4.38 47.24875 29.04603 10.588055 2 Al 100 0.35 11.56 6.89 74.44054 38.85057 12.516155 2 Al 153 0.29 11.28 6.89 46.77052 17.23554 6.43493 9 Al 0.04 6.86 7.81 8.47 5.590785 6.91529 5.90351333 9 Al 0.08 2.64 4.59 3.36 6.39371 4.32476 6.23896 9 Al 0.25 1.27 3.26 1.83 2.950005 3.00279 2.3941925 9 Al 1 0.3 3.16 1.24 1.642385 3.9989233 3.390295 9 Al 3 0.14 1.81 1.37 7.189843 25.43289 29.36164 9 Al 9 0 2.24 1.64 14.81654 57.9328 37.278995 9 Al 20 0.03 2.42 1.82 31.47129 52.105485 34.10627 9 Al 41 0.01 2.89 1.94 50.61513 42.284105 26.163305 9 Al 100 0.05 7.76 2.83 77.05205 46.50018 20.643755 9 Al 153 0.07 10 3.16 44.60668 27.28335 13.628605 11 Al 0.04 15.4 14.22 16.62 10.71107 9.61013 11.44535 11 Al 0.08 3.49 5.35 3.46 8.512097 8.190315 8.32104 11 Al 0.25 1.43 2.83 2.14 2.794915 3.264255 4.13716 11 Al 1 0.54 2.54 1.22 2.16882 3.5883267 5.07472 11 Al 3 0.25 1.49 1.13 4.73011 14.19131 23.1195667 11 Al 9 0.19 2.17 1.57 6.40068 25.272635 27.1072 11 Al 20 0.27 2.26 1.8 11.96976 19.376725 19.72734 11 Al 41 0.25 1.4 2.32 20.29758 25.51652 8.82426 11 Al 100 0.79 5.52 2.9 37.68425 25.60384 7.9526 11 Al 153 0.55 5.92 2.97 26.38156 19.382265 7.41557 16 Al 0.04 5.91 5.43 7.02 3.235485 4.385075 5.135255 16 Al 0.08 1.08 2.48 1.99 5.342895 5.00603 4.554365 16 Al 0.25 0.25 1.09 0.67 1.79371 3.212286 4.55372 16 Al 1 0.08 1.64 1 1.813715 4.3455433 4.80414 16 Al 3 0 0.78 0.51 6.53001 11.993165 27.385065 16 Al 9 0.01 1.04 1.08 12.23535 20.45073 19.425865 16 Al 20 0.06 1.95 1.52 27.27456 20.47731 10.517955 16 Al 41 0.09 3.42 2.22 45.71238 27.353725 6.775935 16 Al 100 0.21 9.26 4.1 80.96822 33.04613 9.454245 16 Al 153 6.9 10.64 4.54 52.22444 25.25054 8.95003 22 Al 0.04 4.93 47.76 31.61 27.41796 20.414745 19.95128 22 Al 0.08 1.13 45.26 23.84 64.08879 35.79137 28.355225 22 Al 0.25 0.33 40.69 27.12 45.01966 32.480947 29.701535 22 Al 1 0.07 49.58 33.22 48.08122 47.310385 27.590625 22 Al 3 0.02 26.69 36.24 60.47048 69.40947 82.85798 22 Al 9 0.02 25.96 35.89 53.74 64.92715 44.606895 22 Al 20 0.18 26.19 27.72 64.56909 58.152765 33.5019 22 Al 41 0.19 22.56 25.07 77.27936 71.330135 27.192985 22 Al 100 1.15 31.91 23.88 112.6998 93.362405 34.51674 22 Al 153 0.74 24.87 20.43 69.1512 61.56371 23.34748 27 Al 0.04 0.96 6.19 4.52 3.77846 2.94107 2.626195 27 Al 0.08 0.36 7.44 4.87 9.774915 4.72447 3.96443 27 Al 0.25 0.2 11 5.04 7.93863 4.45449 4.012295 27 Al 1 0.36 21.39 3.79 14.6137 10.855763 6.49178 27 Al 3 0.0383 15.62 4.46 45.30698 46.18448 24.693995 27 Al 9 0.1229 13.98 7.85 35.68898 87.948705 39.003815 27 Al 20 0.1 11.28 9.64 52.48107 53.11634 57.7405467 27 Al 41 0.01 10.45 8.54 68.66669 59.80021 53.74543 27 Al 100 0.17 18.36 12.57 103.4709 65.71815 31.903085 27 Al 153 0.15 14.26 10.89 63.834 40.473215 24.382225 31 Al 0.04 5.8 11.14 7.83 5.24134 9.441905 5.45239 31 Al 0.08 0.51 6.38 2.67 11.43996 9.659275 8.8079 31 Al 0.25 0.21 6.14 2.94 4.10445 13.18536 8.39864 31 Al 1 0.14 17.76 5.85 8.045233 10.449885 10.767285 31 Al 3 0.09 15.72 7.7 29.01025 48.183505 39.005365 31 Al 9 0.43 16 11.15 32.66276 52.94523 31.65226 31 Al 20 0.57 13.63 11.35 43.59015 49.598037 34.502765 31 Al 41 0.58 11.4 9.99 53.12263 34.609475 26.82497 31 Al 100 1.5 18.57 18.49 84.85811 42.77723 29.53314 31 Al 153 1.06 16.13 9.87 57.71907 26.95338 14.706925 33 Al 0.04 0.28 3.12 0.66 3.1785 3.9741933 2.095175 33 Al 0.08 0 1.37 0 4.408555 6.769955 5.93896667 33 Al 0.25 0 1.06 0.22 1.6774 11.84096 9.63075 33 Al 1 0.62 1.93 0.99 4.251175 13.031115 8.06662 33 Al 3 0.06 2.46 2.52 7.331375 33.578325 28.293795 33 Al 9 0.16 3.97 3.45 10.46027 14.1624 12.09305 33 Al 20 0 4.62 3.75 19.9492 13.96912 8.302505 33 Al 41 0 4.74 4.38 26.19114 confused!!! i 5.52026 33 Al 100 0.09 11.98 11.16 47.1949 18.74692 8.022495 276 Appendix (mg/L) A B C A B C ID Element Day DDW HOAc HN03 cit-lowpH cit-medpH cit-highpH 33 Al 153 0.06 9.7 7.79 32.14439 14.01084 5.67494 er Al 0.04 0 0.43 0.44 0.607615 0.47656 0.349755 er Al 0.08 0 0.23 0 0.48183 0.29245 0.12318 er Al 0.25 0 0.11 0 0.068145 0.20522 0.14094 er Al 1 0.01 0.13 0.09 0.16699 0.121645 0.061925 er Al 3 0.05 0.14 0.14 0.14934 0.11517 0.173735 er Al 9 0.29 0.12 0.12 0.163743 0.178175 0.36885 er Al 20 0.2 0.14 0.07 0.249613 0.26073 0.489765 er Al 41 0.16 0.11 0.04 0.29076 0.175605 0.22455 er Al 100 0.31 0.15 0.21 0.42055 0.111025 0.19901 er Al 153 0.29 0.06 0.18 0.580835 0.093365 0.044155 gyp Al 0.04 0.06 1.41 0.86 1.286715 0.82632 0.71314 oyp Al 0.08 0 1.03 0 1.313095 0.6511 ppte gyp Al 0.25 0 1.14 0.82 1.330944 0.87969 0.84777 gyp Al 1 0.17 1.82 0 3.999995 1.22791 1.166415 gyp Al 3 0 2.79 2.44 7.262075 2.46754 2.48999 gyp Al 9 0.03 5.41 4.44 6.95991 5.32547 4.24583 gyp Al 20 0 5.64 4.5 5.91599 7.302205 6.87858 GYP Al 41 0.23 3.8 3.82 5.244043 12.944905 6.67574 gyp Al 100 0.22 4.64 3.59 7.081875 7.871135 5.53687 gyp Al 153 0.79 2.92 2.97 3.14562 1.9995 2.36836 mr Al 0.04 4.55 20.04 16.47 19.31017 14.82367 4.26792 mr Al 0.08 0.74 21.69 13.72 36.58577 20.581375 7.960715 mr Al 0.25 1.22 28.89 21.19 27.55805 14.494215 5.1131375 mr Al 1 2.09 34.24 25.73 45.66423 43.789165 8.458755 mr Al 3 2.22 38.55 27.74 75.54306 45.51388 22.955515 mr Al 9 2.95 48.91 21.83 102.6469 51.09823 26.825525 mr Al 20 3.55 49.38 24.78 127.7009 64.82725 51.48332 MR Al 41 5.26 45.04 24.22 124.0493 60.81357 58.56996 mr Al 100 21.77 56.6 31.58 169.7959 86.79675 42.019915 mr Al 153 15.69 46.45 28.05 89.99461 56.59099 18.39428 2 Ca 0.04 51.05 50.55 48.67 25.2339 34.00503 43.450875 2 Ca 0.08 10.09 14.25 11.94 31.93693 25.540535 14.414405 2 Ca 0.25 2.9 14.33 15.12 18.25706 7.91139 3.12082 2 Ca 1 1.37 18.58 13.92 14.09858 4.32948 1.22113 2 Ca 3 1.02 5.79 4.16 10.19481 13.50649 4.02597 2 Ca 9 1.43 2.18 1.58 4.26894 10.60565 5.38064 2 Ca 20 1.45 1.04 0.65 2.724085 2.488835 7.26905 2 Ca 41 1.68 0.92 0.6 4.942165 1.49355 7.81114 2 Ca 100 3.13 1.85 1.38 10.43576 2.82976 6.51956 2 Ca 153 2.67 2.38 1.33 8.81182 2.23324 1.16078 9 Ca 0.04 569.88 467.68 618.2 629.0482 1041.6967 895.01623 9 Ca 0.08 506.94 457.81 491.84 620.5405 480.13513 339.54955 9 Ca 0.25 354.07 424.92 305.02 344.4348 118.65218 99.4565225 9 Ca 1 103.66 296.63 77.2 73.49023 23.16459 18.37255 9 Ca 3 23.99 63.62 20.86 39.09091 14.54545 5.58441 9 Ca 9 12.52 22.15 7.41 14.40768 9.73852 3.2017 9 Ca 20 6.76 10.59 2.51 5.379225 3.47993 4.249745 9 Ca 41 5.49 8.74 1.96 2.858585 0.968435 3.30321 9 Ca 100 5.72 4.79 3.17 3.7833 1.11491 3.32717 9 Ca 153 5.25 2.56 3.3 2.75962 0.82955 3.10517 11 Ca 0.04 568.49 400.94 611.96 607.3453 639.34869 1067.51532 11 Ca 0.08 483.84 442.17 403.42 634.5646 861.98193 595.27026 11 Ca 0.25 471.77 455.74 475.34 402.4783 228.43478 99.5652175 11 Ca 1 259.73 509.07 184.65 156.694 56.246293 25.1014167 11 Ca 3 54.74 177.07 47.98 56.62338 21.16883 5.97402 11 Ca 9 22.95 53.28 20.22 15.11561 12.09268 2.96886 11 Ca 20 11.26 18.16 7.92 5.634775 4.4769 4.65042 11 Ca 41 8.66 7.74 4.72 1.669455 0.962595 4.270355 11 Ca 100 7.7 1.09 1.23 0.66306 0.294745 4.460125 11 Ca 153 3.96 0.46 0.22 0.26498 0.127115 0.750775 16 Ca 0.04 509.03 343.04 497.19 179.7409 303.84131 453.22059 16 Ca 0.08 217.35 284.73 266.01 364.955 352.61261 197.2072 16 Ca 0.25 113.65 167.41 92.03 190.7391 125.83851 190.43478 16 Ca 1 24.97 91.9 31.6 84.36865 30.214667 52.99188 16 Ca 3 8.17 23.49 13.89 36.55844 14.80519 8.051945 16 Ca 9 5.78 11.62 7.83 12.45474 8.906585 2.824035 16 Ca 20 3.93 5.37 2.83 4.981695 5.34452 5.770435 16 Ca 41 2.69 2.16 1.18 1.65777 1.03529 5.349145 16 Ca 100 3.12 0.75 0.48 1.887615 0.591385 5.897315 16 Ca 153 2.14 0.69 0.41 1.105875 0.32346 1.2127 22 Ca 0.04 457.91 360.96 468.61 166.6517 346.25766 452.326885 22 Ca 0.08 161.64 198.39 181 320.9459 261.75675 159.32431 22 Ca 0.25 46.29 81.41 51.24 119.3328 61.463043 84.38913 22 Ca 1 13.79 38.91 14.09 55.71754 19.58671 14.008615 22 Ca 3 7.67 17.29 7.36 33.57143 16.85676 5.2795 22 Ca 9 5.71 9.73 9.71 9.92034 11.006515 5.06879 22 Ca 20 6.06 5.53 12.23 8.22501 8.433235 8.0641 22 Ca 41 6.74 2.82 13.49 6.085855 3.069535 6.964725 277 Appendix (mg/L) A B C A B C ID Element Day DDW HOAc HN03 cit-lowpH cit-medpH cit-highpH 22 Ca 100 7.89 3.45 3.93 10.48987 3.989285 8.64259 22 Ca 153 3.84 2.83 2.39 7.47637 2.514135 3.05841 27 Ca 0.04 593.81 474.06 575.01 633.4532 802.39367 868.555385 27 Ca 0.08 492.28 469.64 583.55 579.1892 506.66663 530.360345 27 Ca 0.25 445.84 463.54 405.11 386.6516 145.24886 201.055795 27 Ca 1 183.88 436.16 132.18 155.6795 38.539545 66.493395 27 Ca 3 53.31 108.94 48.03 57.40165 18.064175 15.165625 27 Ca 9 29.1 33.95 17.89 15.78566 12.816795 6.154955 27 Ca 20 13.29 12.19 6.52 8.60676 7.975765 5.26366333 27 Ca 41 9.99 8.05 3.28 4.16715 2.03749 3.742645 27 Ca 100 12.82 5.46 3.98 6.37954 2.18758 6.859395 27 Ca 153 8.74 4.12 3.76 4.579645 1.47265 4.737535 31 Ca 0.04 340.26 314.52 312.2 182.7084 294.31703 188.943745 31 Ca 0.08 106.39 131.44 97.7 138.018 69.63963 118.46847 31 Ca 0.25 28.7 46.88 28.89 50.5656 23.265455 66.51583 31 Ca 1 11.39 25.35 13.89 25.60851 5.578085 18.3823475 31 Ca 3 7.62 10.1 8.21 18.73705 11.38716 4.03726 31 Ca 9 6.23 8.83 4.48 5.575665 11.420817 4.23627 31 Ca 20 5.39 9.69 2.95 2.099605 3.8959667 5.289235 31 Ca 41 4.59 4.41 5.81 1.283895 0.90872 5.3764 31 Ca 100 6.85 1.61 5.34 2.50463 1.28909 6.1394 31 Ca 153 5.52 1.07 1.14 2.169505 0.942035 4.37165 33 Ca 0.04 48.17 47.53 45.22 29.87948 36.742547 32.85068 33 Ca 0.08 10.23 12.22 11.36 16.66666 10.630625 16.75675 33 Ca 0.25 2.66 5.65 3.5 7.42835 4.638 4.939665 33 Ca 1 1.4 7.31 1.62 7.28955 2.34533 1.26774 33 Ca 3 1.11 4.88 8.82 4.91718 6.366455 1.60455 33 Ca 9 1.34 1.91 5.73 2.147965 5.25059 3.221955 33 Ca 20 1.63 0.66 1.87 1.234245 0.965205 3.641725 33 Ca 41 1.29 0.34 0.69 1.181985 mixed 3.455745 33 Ca 100 1.44 0.72 0.64 2.750395 0.98085 2.91018 33 Ca 153 0.41 0.75 0.46 2.086765 0.70368 0.34766333 er Ca 0.04 0.04 0.48 0.33 0.54402 0.669565 0.54402 er Ca 0.08 0 0.17 0 0 0.09009 0 er Ca 0.25 0 0 0.01 0 0.23 0.150825 er Ca 1 0 0.04 0 0.31693 0 0.253545 er Ca 3 0.05 0.03 0 0 0 0 er Ca 9 0.31 0.02 0.07 0.23866 0.059665 0 er Ca 20 0.06 0.05 0.06 0.038825 0 0.04992 er Ca 41 0.05 0.03 0.09 0.015575 0 0.00973 er Ca 100 0.16 0.11 0.03 0.147365 0.068555 0.14737 er Ca 153 0.08 0 0.11 0.1131 0.048575 0.085015 gyp Ca 0.04 621.51 509.98 708.52 734.307 1827.5862 1735.68798 gyp Ca 0.08 611.72 510.38 632.31 537.6126 1430.6306 ppte gyp Ca 0.25 596.35 527.2 610.14 678.552 1648.5939 815.9447 gyp Ca 1 479.91 476.84 0 707.0131 1411.8183 450.974055 gyp Ca 3 661.43 484.6 797.31 759.7826 661.59418 90.942015 gyp Ca 9 601.36 481.51 672.14 939.0811 174.76132 28.95783 gyp Ca 20 638.63 512.84 618.23 683.2022 17.168525 6.33765 gyp Ca 41 668.97 497.8 645.38 689.5753 2.26467 1.203125 gyp Ca 100 664.12 429.1 602.63 742.1208 0.401085 0.307695 gyp Ca 153 598.28 505.89 642.91 678.6693 0.24063 0.08577 mr Ca 0.04 56.8 62.28 59.03 49.46434 52.85403 43.9726275 mr Ca 0.08 13.59 17.4 15.16 19.9099 16.21621 16.441435 mr Ca 0.25 3.89 7.99 6.23 10.57123 4.9164125 4.90558 mr Ca 1 1.76 6.7 5.37 5.97402 3.571425 1.68831 mr Ca 3 1.43 5.68 5.19 12.33333 6.66666 3.26666 mr Ca 9 1.92 6.41 3.07 15.33412 9.66587 5.01193 mr Ca 20 1.33 6.72 3.7 15.69853 5.87446 4.16593 MR Ca 41 0.99 7.03 4.1 19.47852 5.54841 4.18143 mr Ca 100 2.52 9.17 6.42 36.98433 9.46201 6.53995 mr Ca 153 2.97 9.77 6.77 25.69856 5.95893 3.52981 2 Cu 0.04 4.65 4.75 5.09 2.82067 3.272815 4.14927 2 Cu 0.08 0.94 1.12 1.11 2.21606 1.881345 1.43409 2 Cu 0.25 0.28 0.42 0.37 0.93228 0.8553 1.508068 2 Cu 1 0.15 0.41 0.31 0.845553 0.7557 0.826405 2 Cu 3 0.11 0.36 0.33 1.72173 2.201865 3.034595 2 Cu 9 0.19 0.64 0.46 1.82922 1.97149 1.72856667 2 Cu 20 0.18 0.67 0.49 1.920745 1.316025 0.930405 2 Cu 41 0.19 0.58 0.41 2.43347 1.69013 0.66074 2 Cu 100 0.25 0.69 0.58 2.32666 1.55572 0.69834 2 Cu 153 0.16 0.5 0.37 0.883405 0.50272 0.35336 9 Cu 0.04 8.16 8.05- 8.75 6.263905 6.26391 5.53700333 9 Cu 0.08 1.7 2.03 1.5 2.946095 2.308395 1.92751333 9 Cu 0.25 0.59 0.61 0.53 1.0584 0.7989 0.95538 9 Cu 1 0.28 0.44 0.25 0.450765 0.3947867 0.4817 9 Cu 3 0.14 0.29 0.27 1.205333 1.15157 1.15157 9 Cu 9 0.14 0.43 0.37 1.45757 1.620165 1.33562 9 Cu 20 0.22 0.41 0.93 1.9126 1.51576 0.99567 278 Appendix (mg/L) A B C A B C ID Element Day DDW HOAc HN03 Cit-lowpH cit-medpH cit-highpH 9 Cu 41 0.16 0.37 0.95 2.300515 1.476595 0.78362 9 Cu 100 0.66 0.65 2.2 1.9965 1.51077 0.72427 9 Cu 153 0.67 0.44 1.71 0.899795 0.61747 0.43168 11 Cu 0.04 12.75 11 13.15 9.373258 7.2621 8.7646 11 Cu 0.08 2.38 2.89 1.91 4.91497 4.850525 3.953135 11 Cu 0.25 0.83 0.93 0.82 1.335395 1.807745 1.233345 11 Cu 1 0.44 0.58 0.42 0.583345 0.85145 0.664685 11 Cu 3 0.34 0.35 0.38 0.810225 1.001525 0.862735 11 Cu 9 0.44 0.5 0.51 0.804835 0.839175 0.56693 11 Cu 20 0.96 0.46 0.64 1.06475 0.838175 0.532255 11 Cu 41 1.57 1.03 0.72 1.20666 1.011255 0.437135 11 Cu 100 3.18 0.65 2.33 1.03887 0.627465 0.503015 11 Cu 153 1.78 0.51 2.05 0.459 0.24225 0.340605 16 Cu 0.04 4.35 3.36 4.6 2.500695 2.479825 2.952835 16 Cu 0.08 0.78 1 0.96 2.13238 1.78612 1.17151 16 Cu 0.25 0.25 0.32 0.28 0.591885 0.6254175 0.8164 16 Cu 1 0.07 0.19 0.12 0.237085 0.2963533 0.38103 16 Cu 3 0.08 0.16 0.16 0.573905 0.393855 0.607665 16 Cu 9 0.11 0.15 0.25 0.80269 0.342405 0.513605 16 Cu 20 0.12 0.24 0.46 1.1509 0.542635 0.330015 16 Cu 41 0.15 0.19 0.61 1.214715 0.76549 0.25583 16 Cu 100 0.33 0.35 1.78 0.999115 0.846995 0.29558 16 Cu 153 0.23 0.26 1.5 0.49179 0.48815 0.22039 22 Cu 0.04 55.14 68.64 75.32 46.57067 48.135775 51.865285 22 Cu 0.08 13.07 34.04 24.73 59.82225 40.03924 24.02758 22 Cu 0.25 4.16 22.57 17.87 28.77121 21.95494 15.510725 22 Cu 1 1.66 22.24 18.12 21.37595 21.469085 11.06689 22 Cu 3 1.4 12.61 16.81 20.7358 20.43306 20.83063 22 Cu 9 1.66 9.52 16.16 9.640745 12.5007 16.44962 22 Cu 20 2.75 5.65 12.92 5.272605 6.28737 10.91509 22 Cu 41 4.04 3.39 10.02 3.82345 3.96446 7.88058 22 Cu 100 11.22 3.48 6.71 3.128725 2.855605 6.513275 22 Cu 153 6.04 1.73 3.56 1.497575 0.97401 2.34289 27 Cu 0.04 26.18 38.85 38.52 24.58071 20.20791 19.39537 27 Cu 0.08 7.06 11.44 10.43 22.58771 12.53462 11.4641 27 Cu 0.25 3.8 6.04 4.78 9.31524 6.03577 6.66633 27 Cu 1 2.26 7.37 3.74 8.306517 5.8368567 5.732425 27 Cu 3 1.53 5.78 4.17 9.64477 10.84915 8.47276 27 Cu 9 3.53 6.35 5.53 6.067915 10.99354 7.65085 27 Cu 20 1.31 4.68 5.38 4.224315 5.291335 6.37529667 27 Cu 41 1.26 2.77 3.89 2.74168 3.154645 4.91126 27 Cu 100 3.82 2.33 5.31 1.71302 1.877235 3.59371 27 Cu 153 2.75 0.9 3.04 0.595225 0.525025 1.579475 31 Cu 0.04 40.75 44.45 41.14 25.2816 35.21498 21.008035 31 Cu 0.08 9.02 12.04 9.93 16.48488 8.518 13.936975 31 Cu 0.25 3.08 4.59 4.33 5.13536 4.23495 7.71819 31 Cu 1 1.94 4.51 3.22 2.876795 2.55715 4.0114225 31 Cu 3 1.78 3.17 2.71 5.555695 4.668595 3.609905 31 Cu 9 2.23 3.37 3.18 5.05753 5.8584 3.134045 31 Cu 20 2.56 2.51 3.11 4.894615 5.4836833 3.206715 31 Cu 41 1.86 1.92 2.28 4.723915 3.930215 3.01766 31 Cu 100 2.82 2.53 4.6 4.40787 3.24661 3.45954 31 Cu 153 1.65 1.51 2.36 1.863195 1.21678 1.637975 33 Cu 0.04 87.51 718.42 292.36 450.9751 371.67545 141.768615 33 Cu 0.08 17.98 166.35 197.46 306.8588 274.55275 218.851943 33 Cu 0.25 6.36 40.89 201.21 81.10847 127.1285 193.61288 33 Cu 1 4 14.49 163.53 23.31922 24.961895 150.69855 33 Cu 3 4.59 6.16 65.23 8.74148 6.82483 75.41635 33 Cu 9 8 6.08 23.16 5.350445 2.9348667 15.73427 33 Cu 20 19.94 5.72 12.63 5.090385 2.062465 4.747645 33 Cu 41 21.69 5.34 7.21 5.44509 mixed 2.675205 33 Cu 100 90.67 10.73 16.58 7.78133 2.144025 3.58814 33 Cu 153 73.54 7.43 11.2 5.8543 1.25334 2.53886333 er Cu 0.04 0.03 0.28 0.02 0 0.018605 0.018605 er Cu 0.08 0.03 0.03 0.01 0.04905 0 0.02308 er Cu 0.25 0.16 0.03 0.05 0 0 0 er Cu 1 1.08 0.04 0.22 0.15664 0.025395 0.033865 er Cu 3 0.08 0.05 0.05 0.01942 0.019425 0.029135 er Cu 9 0.03 0.01 0.05 0.039625 0.021335 0.054875 er Cu 20 0.03 0.06 0 0.059557 0.11346 0.04578 er Cu 41 0.08 0.03 0.05 0.096685 0.02417 0.06043 er Cu 100 0 0.03 0 0.067455 0.012645 0.08432 er Cu 153 0.04 0 0.04 0.040945 0.020465 0.03363 gyp Cu 0.04 0.01 0.07 0.06 0.05582 0.0124 0 gyp Cu 0.08 0.06 0.06 0.03 0.01154 0 ppte gyp Cu 0.25 0.01 0.03 0.03 0.012954 0 0.02019 gyp Cu 1 0.06 0 0 0.01125 0 0 gyp Cu 3 0 0.05 0.05 0.025895 0.019425 0.0259 gyp Cu 9 0.02 0.03 0.05 0.03658 0.03963 0.04064 279 Appendix (mg/L) A B C A B C ID Element Day DDW HOAc HN03 Cit-lowpH cit-medpH cit-highpH gyp Cu 20 0 0.06 0 0.009935 0.013735 0.03205 GYP Cu 41 0.12 0.02 0.09 0.047 0.088635 0.0931 gyp Cu 100 0 0.04 0 0.010535 0.01054 0.04216 gyp Cu 153 0.03 0.02 0.06 0.00731 0.00585 0.01754 mr Cu 0.04 6.82 28.94 23.22 8.25869 4.24254 4.31897 mr Cu 0.08 2.63 21.57 12.82 12.6183 2.01408 2.12084 mr Cu 0.25 3.8 24.74 17.32 12.41141 4.6939175 5.8255275 mr Cu 1 8.94 42.76 33.88 15.58186 5.183945 9.63644 mr Cu 3 15.02 64.39 54.8 64.93521 66.21232 77.537955 mr Cu 9 30.23 83.36 53.54 63.66879 89.6558 109.60946 mr Cu 20 39.38 75.27 48.5 53.49598 99.48609 141.7456 MR Cu 41 35.25 56.46 32.47 39.30622 85.56637 116.15601 mr Cu 100 111.93 99.55 64.64 45.3704 92.94598 129.16472 mr Cu 153 101.79 123.94 53.23 22.49587 39.88475 64.831735 2 Fe 0.04 0.31 18.78 6.89 16.23711 18.38487 15.406635 2 Fe 0.08 0.11 9.51 3.12 25.30505 24.89831 23.619985 2 Fe 0.25 0.11 5.09 1.06 23.62414 28.583615 17.250442 2 Fe 1 0 5.92 0.65 41.69005 44.48082 30.308695 2 Fe 3 0.04 9.71 1.46 88.13302 72.39657 97.5838 2 Fe 9 0.07 24.84 2.62 99.17969 62.8125 53.02083 2 Fe 20 0.02 30.42 3.08 93.41122 58.64819 29.252015 2 Fe 41 0.02 31.76 4.54 94.55809 66.060615 19.05756 2 Fe 100 0.09 40.44 6.29 117.8541 81.06521 25.42922 2 Fe 153 0.03 27.01 5.55 61.46127 32.38229 13.880445 9 Fe 0.04 4.41 52.91 23.68 42.5544 20.332185 14.68117 9 Fe 0.08 1.05 68.31 15.8 78.06508 42.620565 27.3871733 9 Fe 0.25 0.66 113.58 20 103.2431 46.652275 21.4953525 9 Fe 1 0.43 306.99 24.47 249.9532 142.8126 45.04209 9 Fe 3 0.36 336.12 25.79 673.5022 451.94366 160.351275 9 Fe 9 0.12 306.12 25.63 423.9453 497.77347 231.91408 9 Fe 20 0.13 171.81 18.7 231.9169 320.24821 273.69706 9 Fe 41 0.04 87.67 21.31 163.3132 162.89215 268.976465 9 Fe 100 0.12 67.66 14.94 168.9572 131.03666 331.063165 9 Fe 153 0.03 45.43 12.55 84.8286 52.649705 116.616945 11 Fe 0.04 1.7 23.6 16.39 21.60652 18.04123 19.387165 11 Fe 0.08 0.22 13.38 5.2 26.07011 25.944215 25.276 11 Fe 0.25 0.38 17.1 6.74 20.92323 16.01935 16.08473 11 Fe 1 0.03 36.65 8.58 50.74836 35.890233 27.4590867 11 Fe 3 0.2 23.79 5.86 140.0678 120.31918 86.3944367 11 Fe 9 0.11 32.45 8.42 166.5625 180.15627 88.164065 11 Fe 20 0.04 43.81 8.35 182.7516 186.28836 90.887735 11 Fe 41 0.02 21.58 26.98 217.0336 227.05356 65.6209 11 Fe 100 0.03 41.59 7.22 217.9499 124.03859 81.958315 11 Fe 153 0.03 31.32 7.11 67.25428 29.56715 56.172705 16 Fe 0.04 1.53 7.75 6.99 9.22107 7.50286 7.187855 16 Fe 0.08 0.27 5.29 3.19 12.2022 11.6502 8.773965 16 Fe 0.25 0.13 4.51 1.48 7.813515 6.9144725 8.56545 16 Fe 1 0.12 3.48 0.63 18.33741 11.12782 9.40379 16 Fe 3 0.12 4.26 1.31 68.65192 28.307765 35.84165 16 Fe 9 0.43 16.33 5.15 106.4453 43.78906 29.10156 16 Fe 20 0.05 24.8 6.03 106.1178 61.303465 18.791525 16 Fe 41 0.04 26.77 6.2 98.74945 74.58366 13.780945 16 Fe 100 0.14 36.47 7.41 149.0824 93.34245 23.728635 16 Fe 153 6.81 34.11 6.6 89.49881 45.46539 19.49446 22 Fe 0.04 0.07 5.07 1.15 3.86597 3.121415 3.18923 22 Fe 0.08 0 7.34 0.93 9.44218 8.25101 10.604295 22 Fe 0.25 0.03 11.75 0.72 10.00615 10.49533 12.45432 22 Fe 1 0 18.17 0.96 29.10475 21.816805 10.626285 22 Fe 3 0 10.39 0.97 82.02568 52.870895 55.54564 22 Fe 9 0.03 17.17 2.49 97.77344 63.4375 33.59375 22 Fe 20 0 23.41 3.75 117.3486 63.327195 34.539235 22 Fe 41 0.05 23.59 7.1 129.4549 83.443515 27.197025 22 Fe 100 0.03 44.4 4.02 175.8513 125.40884 35.47979 22 Fe 153 0.08 30.43 3.99 99.28672 69.198845 22.130605 27 Fe 0.04 0.07 25.21 5.43 18.80809 8.31055 5.494805 27 Fe 0.08 0.05 39.62 7.62 41.10982 17.78036 11.12725 27 Fe 0.25 0 79.96 11.4 67.08283 22.289885 13.428745 27 Fe 1 0 236.83 12.61 221.0833 86.232823 30.09215 27 Fe 3 0.03 275.88 13.12 681.5264 347.09344 102.04172 27 Fe 9 0.0408 231.46 19.67 190.3906 480.85941 178.750005 27 Fe 20 0.01 118.76 22.6 135.8504 157.99328 311.576087 27 Fe 41 0.15 60.3 23.07 130.3343 101.24742 327.0099 27 Fe 100 0.67 62.94 13.44 177.9801 106.4455 114.703725 27 Fe 153 0.46 32.23 10.36 100.9221 56.205245 35.498475 31 Fe 0.04 0.23 11.68 2.94 7.7638 9.8141 5.11208 31 Fe 0.08 0 17.8 2.64 25.276 20.104585 14.29401 31 Fe 0.25 0.04 38.41 3.6 21.22411 34.531055 16.1084 31 Fe 1 0.05 156.13 9.88 59.62008 44.385925 24.520395 31 Fe 3 0.01 148.03 14.88 325.0713 175.64193 79.70755 280 Appendix (mg/L) A B C A B C ID Element Day DDW HOAc HN03 cit-lowpH cit-medpH cit-highpH 31 Fe 9 0.03 135.24 31.12 275.5078 307.1734 84.263865 31 Fe 20 0.02 85.42 39.44 232.8534 282.72917 125.66526 31 Fe 41 0.06 60.76 38.51 236.9987 206.39618 143.86264 31 Fe 100 0.19 77.33 22.94 310.8886 182.12619 210.493825 31 Fe 153 0.15 50.98 17.34 142.9052 70.78541 77.758185 33 Fe 0.04 0.01 8.14 0.15 10.93494 10.351733 3.799885 33 Fe 0.08 0 8.71 0 21.41197 13.91632 10.9432433 33 Fe 0.25 0 8.55 0.17 18.42265 32.0341 15.59074 33 Fe 1 0.57 9.33 2.57 32.11397 33.524535 18.290385 33 Fe 3 0.04 11.94 6.79 34.4597 44.802065 54.921535 33 Fe 9 0.14 18.08 11.96 26.1781 17.649637 26.935455 33 Fe 20 0 18.72 15.43 35.2889 14.28189 15.7943 33 Fe 41 0 16.47 17.21 41.20251 mixed 7.60618 33 Fe 100 0 26.16 25.61 68.31961 22.242795 9.293545 33 Fe 153 0.02 16.38 9.81 39.68865 15.467015 5.76046333 er Fe 0.04 0.17 1.03 1.57 1.3942 3.06178 0.300705 er Fe 0.08 0 1.45 1.7 17.08309 39.773385 5.49099 er Fe 0.25 0.44 3.63 3.78 14.49452 80.32887 1.85749 er Fe 1 1.27 15.87 11.12 84.02294 93.70884 32.631175 er Fe 3 2.55 55.43 20.9 702.434 357.65872 51.266045 er Fe 9 5.64 129.92 32.06 1093.927 1238.4385 106.95156 er Fe 20 6.85 165.56 29.52 1368.041 2547.4226 538.25183 er Fe 41 8.04 169.48 26.16 1265.443 519.3538 871.034695 er Fe 100 17.53 139.07 33.95 1009.65 94.86968 1203.95745 er Fe 153 10.97 131 23.18 17.47667 2.823275 592.78314 oyp Fe 0.04 0.02 0.59 0.19 0.68343 0.35538 0.32804 gyp Fe 0.08 0 0.6 0 1.16211 0.46484 ppte gyp Fe 0.25 0 0.98 0.52 1.29996 0.6196033 1.15572 gyp Fe 1 0.02 1.47 0 3.70007 1.114475 1.114475 gyp Fe 3 0.01 2.39 2.5 7.13266 2.36269 2.58559 gyp Fe 9 0 4.89 3.83 8.42967 4.807545 4.148975 gyp Fe 20 0 5.58 4.04 7.870235 7.532505 7.375245 GYP Fe 41 0.01 4.31 4.05 5.51986 13.097975 7.60476 gyp Fe 100 0 6.14 3.64 6.392315 8.7037 7.249655 gyp Fe 153 0.15 3.89 2.8 2.05847 2.18865 2.546645 mr Fe 0.04 81.3 138.95 117.84 51.53089 74.849635 28.9900775 mr Fe 0.08 15.66 54.35 37.81 114.5555 129.48867 118.76816 mr Fe 0.25 3.93 42.42 27.63 70.26295 37.820343 29.46504 mr Fe 1 2.07 53.36 34.31 146.2643 120.09629 18.67867 mr Fe 3 1.98 97.89 42.85 223.7891 86.64063 47.57812 mr Fe 9 1.65 164.63 38.36 245.5144 118.93751 103.559925 mr Fe 20 1.95 166.3 49.47 279.3951 191.66363 173.590665 MR Fe 41 3.64 140.2 53.75 249.7505 197.57373 177.646085 mr Fe 100 14.71 222.41 114.01 351.8793 307.42114 281.93417 mr Fe 153 12.83 218.28 107.93 167.6719 168.0625 169.02256 2 K 0.04 0.09 0.2 0.15 0.2 1.15 1.9 2 K 0.08 0.04 0.14 0.04 0.15 1.6 3.3 2 K 0.25 0.12 0.18 0.06 0.25 1.9 3.1 2 K 1 0.07 0.25 0.15 0.5 2.05 3.7 2 K 3 0.14 0.46 0.23 1.95 6.1 5.95 2 K 9 0.23 0.71 0.31 3.95 6.1 5.1 2 K 20 0.19 0.63 0.24 3.55 4.25 3.7 2 K 41 0.17 0.65 0.22 1.9 5.05 3.6 2 K 100 0.44 1 0.19 1.8 4.85 3.525 2 K 153 0.15 0.95 0.3 0.96 2.2 3.45 9 K 0.04 0.18 0.25 0.18 0.25 1.1 2.1 9 K 0.08 0.04 0.12 0.03 0.15 1.2 2.25 9 K 0.25 0.07 0.13 0.06 0.1 1.15 2.3 9 K 1 0 0.06 0.04 0.1 1.35 2.45 9 K 3 0.03 0.08 0.04 1 2.4 4.9 9 K 9 0.1 0.15 0.05 3.15 5.55 4.3 9 K 20 0.18 0.2 0.08 5.55 4.45 4.25 9 K 41 0.27 0.22 0.12 2.15 5.55 3.75 9 K 100 0.49 0.57 0.31 1.01 5.885 3.42 9 K 153 0.2 0.45 0.15 0.53 2.37 2.915 11 K 0.04 0.03 0.05 0.03 0.3 1 1.9 11 K 0.08 0.02 0.04 0.02 0.2 1.15 2.25 11 K 0.25 0.03 0.09 0.03 0.1 1.1 2.25 11 K 1 0.06 0.09 0.06 0.4 1.35 2.35 11 K 3 0.27 0.25 0.13 2 2.1 3.05 11 K 9 0.58 0.69 0.23 4.45 3.65 2.8 11 K 20 0.81 0.92 0.22 3.7 3.65 2.7 11 K 41 1.05 1.22 0.33 1.2 4.95 2.8 11 K 100 1.73 2.59 0.26 0.5 4.92 2.5 11 K 153 1.4 2.05 0.6 0.115 2.085 2.715 16 K 0.04 0.09 0.19 0.09 0.15 1.2 2.15 16 K 0.08 0.03 0.09 0.03 0.1 1.35 2.5 16 K 0.25 0.09 0.13 0.05 0.1 1.15 2.3 16 K 1 0.08 0.15 0.11 0.3 1.4 2.55 281 Appendix (mg/L) A B C A B C ID Element Day DDW HOAc HN03 cit-lowpH cit-medpH cit-highpH 16 K 3 0.26 0.3 0.22 1.85 2.25 5.15 16 K 9 0.53 0.66 0.25 4.7 4.2 3.5 16 K 20 0.66 0.76 0.2 3.55 3.35 2.95 16 K 41 0.71 0.95 0.21 0.85 5.05 2.85 16 K 100 0.77 2 0.53 0.325 6.02 2.96 16 K 153 0.75 1.8 0.2 0.21 2.545 2.745 22 K 0.04 0.88 1.23 0.71 0.5 1.6 2.6 22 K 0.08 0.28 0.56 0.19 0.65 1.5 1.8 22 K 0.25 0.22 0.48 0.17 0.3 1.45 2.7 22 K 1 0.09 0.38 0.22 0.3 1.65 2.65 22 K 3 0.07 0.38 0.19 0.5 2.5 4.7 22 K 9 0.14 0.41 0.3 1.7 3.6 3.6 22 K 20 0.07 0.32 0.36 2.6 2.95 3.3 22 K 41 0.09 0.3 0.26 2.1 3.9 3.15 22 K 100 0.44 0 0.32 1.915 4.6 3.47 22 K 153 0.1 0.7 0.35 1.155 3.38 2.935 27 K 0.04 0.74 1 0.56 0.55 1.6 2.4 27 K 0.08 0.26 0.47 0.21 0.4 1.35 2.4 27 K 0.25 0.19 0.31 0.11 0.2 1.2 2.3 27 K 1 0.1 0.22 0.11 0.45 1.35 2.5 27 K 3 0.12 0.2 0.11 0.3 1.95 2.9 27 K 9 0.1 0.24 0.13 0.85 4.4 3.3 27 K 20 0.08 0.19 0.14 1.3 3.7 4 27 K 41 0.08 0.18 0.25 1.1 3.45 4.1 27 K 100 0.21 0.62 0.28 1.095 3.01 3.52 27 K 153 0.1 0.4 0.25 0.74 2.005 3.23 31 K 0.04 0.28 0.43 0.28 0.35 1.3 2.1 31 K 0.08 0.11 0.17 0.11 0.4 1.55 2.25 31 K 0.25 0.1 0.16 0.09 0.1 1.55 2.4 31 K 1 0.09 0.11 0.12 0.2 1.55 2.9 31 K 3 0.43 0.23 0.15 0.95 3.05 5 31 K 9 0.6 0.33 0.12 2.8 3.5 3.85 31 K 20 0.67 0.44 0.1 4.5 3.75 3.45 31 K 41 0.64 0.58 0.14 2.4 4.35 3.2 31 K 100 • 0.73 1.43 0.21 0.88 5.475 3.05 31 K 153 0.25 1.35 0.1 0.47 2.615 2.75 33 K 0.04 0.52 0.84 0.44 0.6 1.65 2.5 33 K 0.08 0.19 0.36 0.17 0.4 1.5 2.75 33 K • 0.25 0.23 0.43 0.18 0.2 1.65 2.7 33 K 1 0.16 0.38 0.2 0.45 1.9 3.05 33 K 3 0.13 0.26 0.22 0.3 3.2 3.85 33 K 9 0.17 0.3 0.21 0.3 1.9 2.9 33 K 20 0.12 0.19 0.18 0.3 1.7 2.7 33 K 41 0.14 0.16 0.2 0.4 0 2.7 33 K 100 0.25 0.38 0.27 0.515 1.705 2.845 33 K 153 0.2 0.3 0.3 0.325 1.465 2.615 er K 0.04 0.4 1.27 0.86 0.55 1.75 2.15 er K 0.08 0.51 0.96 0.78 4.5 8.7 3.05 er K 0.25 0.75 1.2 0.92 2.8 18 2.8 er K 1 1.19 3.92 2 17.25 24 9.75 er K 3 2.03 12.36 3.32 119.25 65.25 15.75 er K 9 4.4 30.87 4.66 205.5 227.25 41.25 er K 20 5.75 29.25 6.25 236.25 524.25 127.5 er K 41 6.48 32 6.08 207 129 192 er K 100 9.4 26 5.2 267.2 27.52 466.88 er K 153 7.85 21.5 5.5 3.62 2.095 72.985 gyp K 0.04 1.08 1.47 0.96 0.9 2 2.6 gyp K 0.08 0.28 0.43 0.27 0.5 1.45 2.5 gyp K 0.25 0.16 0.25 0.13 0.2 1.25 2.5 gyp K 1 0.09 0.19 0.11 0.2 1.25 2.5 gyp K 3 0.09 0.17 0.1 0.3 1.3 2.65 gyp K 9 0.1 0.24 0.08 0.6 1.45 2.85 gyp K 20 0.04 0.23 0.09 0.95 1.75 3.05 GYP K 41 0.07 0.2 0.14 1.3 3.1 3.2 gyp K 100 0.2 0.72 0.31 2.475 2.655 3.345 gyp K 153 0.15 0.6 0.35 1.625 1.475 2.66 mr K 0.04 1.21 3.29 2.17 2.8 4.15 15.85 mr K 0.08 0.91 4.59 2.79 6.3 7.35 6.2 mr K 0.25 1.36 7.2 3.97 6.55 5.6 4.75 mr K 1 2.25 10.16 5.83 11.25 16.5 4.75 mr K 3 2.39 9.43 5.81 21 21 9 mr K 9 2.81 5.99 4.75 19.5 15 11.25 mr K 20 2.5 7.55 5 13.5 15 18.75 MR K 41 2.52 6.95 4.06 7.15 9.6 4.9 mr K 100 4.45 7.4 2.84 6.28 11.6 23 mr K 153 2.65 5 2.6 2.705 7.47 8.55 2 Mg 0.04 9.14 8.76 9.38 4.990775 5.694765 7.525975 2 Mg 0.08 1.9 2.11 2.05 4.611645 4.75323 3.98943667 2 Mg 0.25 0.52 0.66 0.49 1.523405 2.36198 1.3878575 282 Appendix (mg/L) A B C A B C ID Element Day DDW HOAc HN03 Cit-lowpH cit-medpH cit-highpH 2 Mg 1 0.23 0.66 0.26 3.50471 1.39292 2.045505 2 Mg 3 0.24 1.11 0.54 8.72045 6.02483 7.791035 2 Mg 9 0.3 4.11 1.27 13.14268 7.772655 4.60676 2 Mg 20 0.11 5.05 1.6 18.43466 7.75157 3.10447 2 Mg 41 0.08 4.45 1.91 25.73009 9.66627 2.72385 2 Mg 100 0.21 6.85 2.84 19.47679 15.62788 5.162815 2 Mg 153 0.22 5.66 2.25 23.24605 9.37284 2.960135 9 Mg 0.04 2.65 2.63 2.81 2.166435 2.426245 2.22929333 9 Mg 0.08 0.61 0.64 0.59 1.48058 1.44012 1.95253333 9 Mg 0.25 0.13 0.19 0.1 0.793413 0.703755 0.46794 9 Mg 1 0 0.12 0 0.56744 0.25335 0.404425 9 Mg 3 0.11 0.09 0.11 2.999303 2.16384 2.864495 9 Mg 9 0 0.55 0.02 7.91194 6.650385 3.65979 9 Mg 20 0.04 1.51 0.15 15.22711 8.100975 3.28092 9 Mg 41 0.02 2.15 0.15 24.80901 9.370955 2.36445 9 Mg 100 0.02 5.32 0.62 43.79106 25.196467 2.39819 9 Mg 153 0.13 5.94 0.83 26.95444 10.6472 2.224515 11 Mg 0.04 15.93 13.73 15.87 10.78193 8.79148 11.20935 11 Mg 0.08 2.82 3.15 2.23 6.77993 7.41909 6.019415 11 Mg 0.25 0.71 0.69 0.63 1.56595 1.8644 1.20486 11 Mg 1 0.17 0.22 0.07 0.31669 0.491645 0.30358 11 Mg 3 0.08 0.01 0.12 0.66951 0.394835 0.515005 11 Mg 9 0 0.17 0.05 1.429255 0.6716 0.37942 11 Mg 20 0.04 0.53 0.13 2.5262 0.754715 0.2935 11 Mg 41 0 0.26 0.35 4.38186 1.32332 0.147075 11 Mg 100 0.09 1.22 0.45 9.02542 2.82654 0.38799 11 Mg 153 0.16 1.29 0.51 5.987645 2.06492 0.51447 16 Mg 0.04 4.15 3.05 3.74 1.95273 1.801875 2.610625 16 Mg 0.08 0.82 0.85 0.81 2.390775 2.21682 1.69093 16 Mg 0.25 0.19 0.2 0.18 0.674275 0.8548233 1.03537 16 Mg 1 0.11 0.22 0.15 0.6086 0.483425 0.56783 16 Mg 3 0.02 0.35 0.3 3.23019 1.23203 2.312755 16 Mg 9 0 1.38 0.72 8.678 3.114665 1.675 16 Mg 20 0.04 2.3 0.9 17.33403 4.83228 0.91369 16 Mg 41 0.04 2.84 •1.08 29.15845 7.846895 0.976275 16 Mg 100 0.04 5.99 2 57.95498 16.14016 2.87404 16 Mg 153 0.67 6.97 2.01 35.67086 11.15947 2.466315 22 Mg 0.04 13.79 11.53 14.16 7.09017 8.17549 10.4907 22 Mg 0.08 3.05 3.35 3.24 8.71359 7.33818 5.509705 22 Mg 0.25 0.74 1.21 1.1 2.32613 2.499995 2.883795 22 Mg 1 0.25 1.08 0.56 2.630085 1.86609 1.194185 22 Mg 3 0.2 1.26 0.47 14.5792 4.141245 5.66672 22 Mg 9 0.12 5.57 0.76 22.72203 6.966175 3.253145 22 Mg 20 0.21 9.93 1.17 29.02865 11.34695 2.81446 22 Mg 41 0.17 9.93 2.93 35.91249 19.927425 2.74469 22 Mg 100 0.47 15.36 5.89 57.0904 35.20419 5.45377 22 Mg 153 0.34 11.66 5.72 34.04469 19.282635 3.97242 27 Mg 0.04 18.94 17.52 18.4 5.826515 11.31717 11.371925 27 Mg 0.08 4.16 4.54 4.27 9.69255 7.38268 7.65372 27 Mg 0.25 1.25 1.31 1.11 2.73591 1.961265 2.711265 27 Mg 1 0.33 0.62 0.37 2.566777 0.79676 0.98556 27 Mg 3 0.12 0.7 0.29 7.511975 2.951125 2.24169 27 Mg 9 1.09 2.6 0.48 13.78827 8.364615 3.42805 27 Mg 20 0.05 4.76 0.59 24.11425 10.41928 4.68373 27 Mg 41 0.02 5.32 0.64 32.99793 16.908835 4.123215 27 Mg 100 0.04 10.12 1.82 57.81583 28.03132 4.811975 27 Mg 153 0.12 7.58 1.81 34.60499 16.40143 4.520385 31 Mg 0.04 5.5 5.06 4.95 6.706335 4.54512 4.366235 31 Mg 0.08 1.26 1.23 1.18 2.370545 1.913425 2.76294 31 Mg 0.25 0.27 0.32 0.32 0.69366 1.563375 1.598585 31 Mg 1 0.16 0.34 0.21 0.84344 0.75056 1.17572 31 Mg 3 0.09 0.3 0.21 3.44458 4.43907 3.89372 31 Mg 9 0.16 0.95 0.41 8.66679 4.6869933 3.174895 31 Mg 20 0.12 1.88 0.6 17.44568 6.51138 2.80287 31 Mg 41 0.08 2.7 0.73 25.89434 8.829735 1.76301 31 Mg 100 0.21 7.17 1.79 52.97224 17.84263 2.285595 31 Mg 153 0.18 7.35 1.15 34.58169 12.648005 1.918195 33 Mg 0.04 11.61 10.11 11.21 5.775405 9.3877725 7.30505 33 Mg 0.08 2.33 2.47 2.54 3.640775 2.932845 4.87863667 33 Mg 0.25 0.51 0.75 0.74 1.021125 1.348585 1.499995 33 Mg 1 0.36 0.42 0.33 0.846475 0.73233 0.54913 33 Mg 3 0.2 0.53 0.36 1.939475 1.36657 1.057965 33 Mg 9 0.29 0.98 0.71 4.685845 1.1064467 0.45705 33 Mg 20 0.34 1.37 1.08 9.49507 1.813345 0.511175 33 Mg 41 0.06 1.62 1.05 13.22473 mixed 0.467675 33 Mg 100 0.28 5.64 3.48 26.07539 6.96164 1.3062 33 Mg 153 0.12 4.95 1.55 16.9772 4.97365 0.93327 er Mg 0.04 0 0.08 0.02 0.37967 0.50379 0.50379 er Mg 0.08 0.09 0.05 0.04 0.18203 0.34789 0.07281 283 Appendix (mg/L) A B C A B C ID Element Day DDW HOAc HN03 Cit-lowpH cit-medpH cit-highpH er Mg 0.25 0 0.02 0 0 0.221825 0.186615 er Mg 1 0.02 0 0 0 0 0 er Mg 3 0 0 0.06 0 0 0.023155 er Mg 9 0.04 0 0.02 0 0 0.020965 er Mg 20 0.12 0.04 0.07 0 0 0 er Mg 41 0 0.02 0 0 0 0 er Mg 100 0.07 0.16 0.12 0 0.039625 0 er Mg 153 0.03 0.02 0.05 0.41349 0.089955 0 gyp Mg 0.04 2.47 7.88 6.06 2.321845 3.844185 2.6139 gyp Mg 0.08 0.72 5.72 5.08 7.508085 2.386725 ppte gyp Mg 0.25 0.24 4.33 4.12 6.262018 2.901312 1.95517667 gyp Mg 1 0.45 5.57 0 14.80557 5.5705 2.98107 gyp Mg 3 0.14 8.87 8.18 24.96487 12.067625 7.82936 gyp Mg 9 0.44 18.41 15.48 21.30786 22.400585 15.99513 gyp Mg 20 0.71 17.78 15.33 9.45599 20.012505 19.70767 GYP Mg 41 1.26 10.24 11.67 4.115497 12.69007 12.9608225 gyp Mg 100 9.96 7.02 8.24 2.83539 6.14338 7.8343 gyp Mg 153 5.39 3.08 4 0.810985 1.467525 1.92236 mr Mg 0.04 10.61 10.57 10.83 9.43706 9.893395 8.1146025 mr Mg 0.08 2.5 3.4 2.99 6.53317 5.01213 3.7864 mr Mg 0.25 0.81 2.55 1.52 4.198723 2.2382825 1.537325 mr Mg 1 0.56 3.75 1.92 8.96079 3.984745 0.92382 mr Mg 3 0.42 6.05 2.81 19.04516 7.04476 3.185045 mr Mg 9 0.45 9.68 3.03 28.5803 10.85274 2.342725 mr Mg 20 0.35 9.89 3.33 35.15867 15.81991 2.20728 MR Mg 41 0.07 9.13 3.32 30.12179 16.1331 1.70337 mr Mg 100 0.53 12.08 4.33 39.91343 25.23534 2.51648 mr Mg 153 0.85 10.69 4.15 16.66667 13.21824 2.016485 2 Mn 0.04 2.28 2.33 2.31 1.316105 1.497635 1.903055 2 Mn 0.08 0.47 0.62 0.57 1.246435 1.14648 0.728475 2 Mn 0.25 0.14 0.26 0.21 0.50907 0.4169 0.255784 2 Mn 1 0.07 0.21 0.13 0.76116 1.2551 0.24816 2 Mn 3 0.05 0.17 0.11 2.644655 2.209505 0.88624 2 Mn 9 0.08 0.38 0.19 2.097145 1.206965 2.22456333 2 Mn 20 0.08 0.57 0.22 1.250995 0.630555 1.32228 2 Mn 41 0.12 0.91 0.28 1.238135 0.604905 0.454645 2 Mn 100 0.44 2.15 0.53 1.61608 0.76594 0.319555 2 Mn 153 0.37 0.69 0.25 0.88141 0.37739 0.142695 9 Mn 0.04 0.67 0.74 0.73 0.534005 0.511315 0.45987667 9 Mn 0.08 0.17 0.28 0.18 0.507355 0.27261 0.34732667 9 Mn 0.25 0.06 0.15 0.1 0.213065 0.099425 0.08049 9 Mn 1 0.04 0.18 0.1 0.1685 0.0708 0.034715 9 Mn 3 0.04 0.17 0.15 0.211005 0.37981 0.107845 9 Mn 9 0.04 0.22 0.15 0.32312 0.384365 0.19746 9 Mn 20 0.01 0.12 0.05 0.51583 0.321815 0.320125 9 Mn 41 0.04 0.09 0.04 0.80059 0.336195 0.275135 9 Mn 100 0.04 0.18 0.04 1.14522 0.4536 0.17651 9 Mn 153 0.03 0.15 0.03 0.66454 0.279905 0.12062 11 Mn 0.04 2.6 2.36 2.59 1.775983 1.549065 1.87129 11 Mn 0.08 0.5 0.58 0.35 1.119723 1.222205 0.970795 11 Mn 0.25 0.16 0.15 0.11 0.248575 0.31072 0.216615 11 Mn 1 0.04 0.05 0.03 0.058205 0.082715 0.0583 11 Mn 3 0.01 0.02 0.02 0.0075 0.013125 0.015 11 Mn 9 0.01 0.03 0.02 0 0 0 11 Mn 20 0 0.01 0 0.01729 0 0 11 Mn 41 0.03 0.03 0.02 0.09011 0.045425 0.009005 11 Mn 100 0.01 0.02 0.01 0.14584 0.08538 0.014745 11 Mn 153 0.01 0 0.01 0.098845 0.043615 0.01344 16 Mn 0.04 0.56 0.45 0.54 0.31314 0.28742 0.378185 16 Mn 0.08 0.1 0.13 0.12 0.32107 0.281695 0.18628 16 Mn 0.25 0.03 0.04 0.03 0.079895 0.0958767 0.113635 16 Mn 1 0.01 0.03 0.02 0.02483 0.02591 0.02375 16 Mn 3 0 0.01 0.01 0.076895 0.03001 0.050635 16 Mn 9 0 0.04 0.02 0.211185 0.067575 0.026395 16 Mn 20 0 0.05 0.02 0.4513 0.115565 0.01349 16 Mn 41 0.01 0.06 0.05 0.774655 0.22732 0.029055 16 Mn 100 0.01 0.12 0.04 1.256705 0.44726 0.073285 16 Mn 153 0.01 0.11 0.03 0.699205 0.27613 0.061795 22 Mn 0.04 5.65 5.37 5.98 3.37044 3.727455 4.59932 22 Mn 0.08 1.3 1.79 1.52 4.077055 3.35009 2.11122 22 Mn 0.25 0.34 0.88 0.73 1.38875 1.18469 0.935765 22 Mn 1 0.12 0.91 0.56 1.05808 0.82379 0.48693 22 Mn 3 0.08 0.64 0.49 1.09162 0.804645 0.89655 22 Mn 9 0.09 0.52 0.51 1.193235 0.827875 0.66103 22 Mn 20 0.14 0.43 0.4 1.122355 0.646585 0.49685 22 Mn 41 0.22 0.36 0.37 1.288895 0.802245 0.41013 22 Mn 100 0.57 0.61 0.3 1.785225 1.11927 0.45876 22 Mn 153 0.3 0.36 0.17 1.04217 0.598035 0.21315 27 Mn 0.04 6.15 6.43 5.88 3.884395 3.70529 3.82708 284 Appendix (mg/L) A B C A B C ID Element Day DDW HOAo HN03 cit-lowpH cit-medpH cit-highpH 27 Mn 0.08 1.35 1.73 1.47 3.28951 2.44138 2.47622 27 Mn 0.25 0.47 0.52 0.44 0.901965 0.61155 0.909645 27 Mn 1 0.14 0.28 0.17 0.39408 0.1885833 0.34981 27 Mn 3 0.05 0.16 0.1 0.331985 0.211945 0.19131 27 Mn 9 0.1 0.16 0.08 0.541705 0.367475 0.149945 27 Mn 20 0.03 0.16 0.06 0.741485 0.38297 0.132305 27 Mn 41 0.01 0.18 0.04 0.937795 0.514235 0.23523 27 Mn 100 0.06 0.34 0.09 1.41995 0.71049 0.25924 27 Mn 153 0.04 0.19 0.06 0.847955 0.413875 0.17431 31 Mn 0.04 1.89 2.07 1.86 1.194975 1.73372 1.10614 31 Mn 0.08 0.49 0.68 0.61 0.973825 0.474035 0.778455 31 Mn 0.25 0.15 0.38 0.32 0.328825 0.305775 0.39182 31 Mn 1 0.1 0.42 0.23 0.340095 0.15655 0.207295 31 Mn 3 0.09 0.21 0.13 0.395755 0.315105 0.261645 31 Mn 9 0.15 0.18 0.13 0.37592 0.36932 0.19756 31 Mn 20 0.16 0.13 0.08 0.508925 0.3371833 0.172025 31 Mn 41 0.1 0.12 0.05 0.715255 0.327735 0.17674 31 Mn 100 0.11 0.25 0.08 1.2511 0.45625 0.2123 31 Mn 153 0.05 0.18 0.03 0.833085 0.32354 0.138795 33 Mn 0.04 8.49 8.52 8.34 7.338945 7.4755433 5.64534 33 Mn 0.08 1.77 2.06 1.98 2.80335 2.247525 3.79434333 33 Mn 0.25 0.46 0.55 0.59 0.74062 0.64382 0.995695 33 Mn 1 0.29 0.21 0.26 0.301225 0.14683 0.269915 33 Mn 3 0.2 0.1 0.13 0.166925 0.076895 0.153795 33 Mn 9 0.26 0.06 0.07 0.170655 0.05548 0.05716 33 Mn 20 0.3 0.05 0.05 0.227555 0.05295 0.035775 33 Mn 41 0.18 0.04 0.04 0.310265 mixed 0.029425 33 Mn 100 0.21 0.16 0.09 0.55828 0.163675 0.04351 33 Mn 153 0.08 0.1 0.03 0.378755 0.118115 0.02475667 er Mn 0.04 0.01 0.03 0.03 0.03152 0.034385 0.02292 er Mn 0.08 0.01 0.01 0.01 0.01211 0.016655 0 er Mn 0.25 0 0.02 0.01 0.004605 0.02151 0.00921 er Mn 1 0.01 0.01 0.01 0.001075 0 0 er Mn 3 0 0.01 0 0 0 0.00281 er Mn 9 0.01 0.02 0 0 0 0 er Mn 20 0.01 0 0.01 0 0 0 er Mn 41 0.01 0 0 0 0 0 er Mn 100 0.01 0 0 0 0 0 er Mn 153 0 0 0 0.00588 0.000125 0 gyp Mn 0.04 0.09 1.89 1.61 1.56751 0.85969 0.22065 gyp Mn 0.08 0.03 1.36 1.08 2.58829 1.205545 ppte gyp Mn 0.25 0.02 1.05 1.15 1.04458 1.16011 0.29938 gyp Mn 1 0.01 1.02 0 0.556125 0.72212 1.04754 gyp Mn 3 0.02 0.85 0.92 0.175365 0.862795 1.587725 gyp Mn 9 0.06 0.35 0.31 0.08154 0.61874 1.07832 gyp Mn 20 0.18 0.12 0.12 0.04522 0.169735 0.705285 GYP Mn 41 0.36 0.06 0.06 0.037147 0.086435 0.25684 gyp Mn 100 3.27 0.06 0.05 0.048785 0.06362 0.111915 gyp Mn 153 1.53 0.02 0.03 0.01609 0.02199 0.021445 mr Mn 0.04 1.59 1.86 1.78 1.57181 1.606195 1.11094 mr Mn 0.08 0.45 0.75 0.6 1.199485 0.85266 0.854175 mr Mn 0.25 0.24 0.62 0.45 0.62083 0.333405 0.2551225 mr Mn 1 0.22 0.55 0.49 0.53737 0.69211 0.139735 mr Mn 3 0.18 0.44 0.46 0.66835 0.63773 0.313585 mr Mn 9 0.17 0.42 0.25 0.70533 0.53131 0.37074 mr Mn 20 0.16 0.35 0.21 0.76282 0.53698 0.83409 MR Mn 41 0.16 0.29 0.15 0.75277 0.52269 1.08787 mr Mn 100 0.5 0.38 0.17 0.960635 0.72196 0.603605 mr Mn 153 0.22 0.19 0.09 0.45629 0.64427 0.20757 2 Mo 0.04 0 0 0.02 0.000605 0.006065 0.006675 2 Mo 0.08 0 0 0 0.009205 0.00921 0.00859 2 Mo 0.25 0 0 0 0.014765 0.01604 0.11 2 Mo 1 0 0 0 0.01161 0.024775 0.015485 2 Mo 3 0 0 0 0.038265 0.032695 0.02365 2 Mo 9 0 0 0 0.030435 0.030435 0.02587 2 Mo 20 0 0.02 0 0 0 0 2 Mo 41 0 0 0 0.031955 0.02025 0.010915 2 Mo 100 0 0 0.01 0.044025 0.024895 0.01128 2 Mo 153 0 0 0 0.02477 0.02636 0.01127 9 Mo 0.04 0 0.01 0 0.085615 0.06315 0.056465 9 Mo 0.08 0 0.01 0 0.165845 0.11056 0.08292 9 Mo 0.25 0 0.01 0 0:199345 0.14667 0.092335 9 Mo 1 0 0.03 0 0.31287 0.2710433 0.130875 9 Mo 3 0 0.05 0 1.011683 0.701355 0.36529 9 Mo 9 0 0.07 0 0.8143 0.984015 0.455095 9 Mo 20 0 0.06 0 0.36156 0.374665 0.173125 9 Mo 41 0 0.02 0 0.548725 0.454745 0.487335 9 Mo 100 0 0.02 0 0.471595 0.435535 0.557085 9 Mo 153 0.01 0 0 0.15293 0.121805 0.202325 285 Appendix (mg/L) A B c A B C ID Element Day DDW HOAc HN03 Cit-lowpH cit-medpH cit-highpH 11 Mo 0.04 0 0 0 0.022663 0.02732 0.047965 11 Mo 0.08 0 0 0 0.050365 0.05958 0.07923 11 Mo 0.25 0.03 0 0 0.068 0.078665 0.08444333 11 Mo 1 . 0 0 0 0.118485 0.2018633 0.16957667 11 Mo 3 0 0 0 0.384075 0.494015 0.44252333 11 Mo 9 0 0 0 0.632415 0.74505 0.48934 11 Mo 20 0 0 0 0.58348 0.45708 0.26955 11 Mo 41 0 0 0 0.83686 0.64098 0.26123 11 Mo 100 0 0 0 0.486315 0.234755 0.306135 11 Mo 153 0 0 0 0.08115 0.037 0.1604 16 Mo 0.04 0 0 0 0.022465 0.017 0.023675 16 Mo 0.08 0 0 0 0.03378 0.04054 0.03255 16 Mo 0.25 0 0 0 0.045995 0.04466 0.049995 16 Mo 1 0 0 0.01 0.09445 0.07208 0.07291 16 Mo 3 0 0 0 0.243525 0.15377 0.13498 16 Mo 9 0 0 0 0.42313 0.221455 0.12937 16 Mo 20 0 0 0 0.204135 0.233985 0.076175 16 Mo 41 0.01 0 0 0.16202 0.20379 0.081955 16 Mo 100 0.01 0 0 0.127675 0.168765 0.142025 16 Mo 153 0 0 0 0.045575 0.04859 0.071305 22 Mo 0.04 0 0 0 0.010925 0.003035 0.00872 22 Mo 0.08 0 0 0 0.03562 0.02272 0.019035 22 Mo 0.25 0 0 0 0.033457 0.02806 0.028055 22 Mo 1 0 0 0 0.069595 0.051365 0.02651 22 Mo 3 0 0.01 0 0.09323 0.06679 0.06262 22 Mo 9 0 0 0 0.060875 0.08066 0.04566 22 Mo 20 0 0 0 0 0 0.00156 22 Mo 41 0 0 0 0.02642 0.026735 0.035915 22 Mo 100 0 0.02 0 0.029675 0.029435 0.035565 22 Mo 153 0 0 0 0.012865 0.01705 0.020055 27 Mo 0.04 0 0 0 0.036225 0.02415 0.020125 27 Mo 0.08 0 0.01 0 0.065105 0.03255 0.021495 27 Mo 0.25 0 0 0.01 0.06507 0.039995 0.03761 27 Mo 1 0 0.01 0 0.148033 0.10053 0.044735 27 Mo 3 0 0.02 0 0.54411 0.27205 0.13915 27 Mo 9 0 0.03 0 0.15905 0.40715 0.18797 27 Mo 20 0 0.02 0 0 0 0.02113 27 Mo 41 0 0 0 0.036545 0.048575 0.224835 27 Mo 100 0 0.04 0 0.03078 0.03618 0.087695 27 Mo 153 0 0 0 0.013705 0.00969 0.02357 31 Mo 0.04 0 0 0 0.007475 0.0138 0.008625 31 Mo 0.08 0 0 0 0.014735 0.01597 0.00798 31 Mo 0.25 0 0 0 0.01432 0.026265 0.018505 31 Mo 1 0 0 0 0.02485 0.039765 0.023195 31 Mo 3 0 0 0 0.099495 0.099495 0.074445 31 Mo 9 0 0 0 0.13622 0.2027267 0.06482 31 Mo 20 0 0.01 0 0.062885 0.0839333 0.01987 31 Mo 41 0 0 0 0.21677 0.14968 0.08053 31 Mo 100 0 0 0 0.21243 0.09377 0.115195 31 Mo 153 0 0 0 0.059345 0.03641 0.06069 33 Mo 0.04 0 0.02 0 0.084535 0.0697767 0.024725 33 Mo 0.08 0 0 0 0.08415 0.055275 0.05445667 33 Mo 0.25 0 0 0 0.040595 0.06388 0.05791 33 Mo 1 0.06 0.03 0 0.04059 0.047225 0.041425 33 Mo 3 0.01 0 0 0.037565 0.0327 0.044525 33 Mo 9 0.03 0.01 0 0.03337 0.02631 0.03465 33 Mo 20 0 0 0 0.008175 0.009805 0.011695 33 Mo 41 0.01 0 0.02 0.01566 mixed 0.010755 33 Mo 100 0 0 0.01 0.025595 0.02371 0.01347 33 Mo 153 0 0 0 0.01521 0.013965 0.01030667 er Mo 0.04 0 0.03 0 0.064985 0.07361 0.059235 er Mo 0.08 0 0.01 0.02 0.03562 0.023955 0.02211 er Mo 0.25 0 0 0.01 0.00597 0.00716 0.00895 er Mo 1 0 0.01 0.01 0.007455 0.004965 0.006625 er Mo 3 0 0 0.01 0.015995 0.01252 0 er Mo 9 0 0.01 0 0.042355 0.04877 0.009625 er Mo 20 0 0 0 0 0 0 er Mo 41 0.01 0 0.02 0.01202 0.004105 0.009805 er Mo 100 0 0 0 0.01333 0.003225 0.01845 er Mo 153 0 0 0 0.01297 0.005485 0.024885 gyp Mo 0.04 0.01 0.01 0.01 0.01035 0.005175 0.00115 gyp Mo 0.08 0 0 0 0.00123 0 ppte gyp Mo 0.25 0 0 0 0.004506 0.002598 0.00333 gyp Mo 1 0.01 0 0 0 0 0.00278 gyp Mo 3 0 0 0 0 0 0 gyp Mo 9 0 0 0 0.006415 0.0077 0.00769667 gyp Mo 20 0 0 0 0.000755 0.00402 0 GYP Mo 41 0.02 0 0.02 0.00337 0.00237 0 gyp Mo 100 0 0 0 0.00472 0.00269 0.00202 286 Appendix (mg/L) A B C A B C ID Element Day DDW HOAc HN03 cit-lowpH cit-medpH cit-highpH gyp Mo 153 0 0 0 0.00528 0.010735 0.006985 mr Mo 0.04 0 0 0 0.007475 0.00805 0.0014525 mr Mo 0.08 0 0 0 0.00368 0.000615 0 mr Mo 0.25 0 0 0 0 0.003205 0 mr Mo 1 0 0 0 0 0 0.00139 mr Mo 3 0 0 0 0.02129 0.0076 0.015965 mr Mo 9 0 0 0 0.00834 0.01155 0.0154 mr Mo 20 0 0 0 0 0 0 MR Mo 41 0.02 0 0.02 0.000635 0.00158 0.009805 mr Mo 100 0 0 0 0.00188 0 0 mr Mo 153 0 0 0 0.007325 0.00784 0.007665 2 Na 0.04 0.02 0.04 0.05 0.085 0.105 0.085 2 Na 0.08 0.01 0.04 0.03 0.095 0.225 0.28 2 Na 0.25 0.07 0.05 0.04 0.13 0.31 0.18 2 Na 1 0.01 0.06 0.1 0.34 0.27 0.345 2 Na 3 0.11 0.15 0.13 1.345 1.405 0.485 2 Na 9 0.17 0.34 0.29 2.135 1.085 0.51 2 Na 20 0.2 0.57 0.44 1.51 1.195 0.345 2 Na 41 0.15 0.82 0.46 1.86 1.425 0.315 2 Na 100 0.33 1.72 1.64 4.275 1.2 0.44 2 Na 153 0.3 1.6 1.6 3.865 0.4 0.46 9 Na 0.04 0.17 0.19 0.23 0.165 0.215 0.215 9 Na 0.08 0.08 0.07 0.11 0.15 0.165 0.165 9 Na 0.25 0.07 0.07 0.05 0.1 0.11 0.115 9 Na 1 0 0.03 0.04 0.145 0.175 0.13 9 Na 3 0.05 0.07 0 0.625 0.54 0.295 9 Na 9 0.14 0.14 0.1 1.34 1.52 0.72 9 Na 20 0.3 0.27 0.23 1.52 1.31 0.605 9 Na 41 0.25 0.44 0.23 1.31 1.885 0.915 9 Na 100 0.45 1.07 0.96 2.54 1.57 0.79 9 Na 153 0.4 0.9 1 2.4 0.555 0.455 11 Na 0.04 0.04 0.06 0.07 0.095 0.1 0.085 11 Na 0.08 0.03 0.04 0.05 0.12 0.14 0.18 11 Na 0.25 0.03 0.05 0.05 0.19 0.135 0.155 11 Na 1 0.08 0.08 0.11 0.775 0.31 0.23 11 Na 3 0.39 0.26 0.25 2.705 0.875 0.295 11 Na 9 1.38 0.99 0.78 2.765 1.825 0.335 11 Na 20 1.74 1.56 0.97 1.4 2.13 0.3 11 Na 41 1.26 1.55 0.87 0.69 2.215 0.325 11 Na 100 1.35 1.95 1.16 1.205 1.49 0.55 11 Na 153 0.9 1.1 0.9 1.16 0.375 0.525 16 Na 0.04 0.09 0.1 0.15 0.08 0.11 0.115 16 Na 0.08 0.04 0.05 0.08 0.115 0.175 0.17 16 Na 0.25 0.02 0.03 0.04 0.115 0.145 0.23 16 Na 1 0.04 0.06 0.11 0.445 0.215 0.23 16 Na 3 0.42 0.25 0.28 1.495 0.555 0.5 16 Na 9 0.8 0.69 0.54 1.965 1.04 0.525 16 Na 20 0.85 0.79 0.52 1.16 1.21 0.37 16 Na 41 0.54 0.84 0.37 0.805 1.82 0.335 16 Na 100 0.53 1.38 0.79 1.79 1.565 0.38 16 Na 153 0.5 1.05 0.85 1.635 0.465 0.295 22 Na 0.04 0.42 0.48 0.68 0.34 0.395 0.46 22 Na 0.08 0.14 0.21 0.23 0.35 0.35 0.385 22 Na 0.25 0.06 0.13 0.13 0.225 0.245 0.275 22 Na 1 0.03 0.14 0.2 0.26 0.325 0.225 22 Na 3 0.06 0.18 0.12 0.43 0.445 0.705 22 Na 9 0.09 0.31 0.24 0.77 0.62 0.31 22 Na 20 0.13 0.43 0.42 1.245 0.47 0.25 22 Na 41 0.06 0.6 0.48 1.865 0.61 0.255 22 Na 100 0.17 0 1.32 3.52 0.65 0.365 22 Na 153 0.15 1.25 1.45 2.62 0.47 0.245 27 Na 0.04 0.33 0.32 0.46 0.31 0.395 0.355 27 Na 0.08 0.13 0.13 0.22 0.24 0.245 0.245 27 Na 0.25 0.08 0.09 0.12 0.15 0.12 0.145 27 Na 1 0.03 0.1 0.09 0.15 0.12 0.105 27 Na 3 0.05 0.11 0.09 0.275 0.295 0.18 27 Na 9 0.04 0.21 0.21 0.51 0.7 0.18 27 Na 20 0.11 0.32 0.36 0.895 0.405 0.335 27 Na 41 0.05 0.5 0.36 1.355 0.53 0.5 27 Na 100 0.17 1.23 1.3 2.715 0.475 0.38 27 Na 153 0.15 0.75 1.2 2.25 0.295 0.27 31 Na 0.04 3.88 3.63 22.5 1.04 0.91 0.635 31 Na 0.08 0.98 0.9 5.16 0.575 0.305 0.355 31 Na 0.25 0.24 0.21 1.2 1.945 1.905 2.145 31 Na 1 0.04 0.09 0.45 0.63 0.605 0.575 31 Na 3 0.29 0.11 0.23 0.765 0.705 0.555 31 Na 9 0.53 0.2 0.23 1.295 0.835 0.47 31 Na 20 0.46 0.34 0.19 1.525 1.05 0.395 31 Na 41 0.36 0.52 0.22 1.14 1.145 0.36 287 Appendix (mg/L) A B c A B C ID Element Day DDW HOAc HN03 cit-lowpH cit-medpH cit-highpH 31 Na 100 0.37 1.1 0.83 2.17 1.285 0.45 31 Na 153 0.2 0.9 0.75 1.91 0.375 0.25 33 Na 0.04 1.8 5.03 4.34 0.765 0.75 2.025 33 Na 0.08 0.42 1.21 1.06 1.7 1.435 0.525 33 Na 0.25 0.11 0.27 0.26 0.435 0.425 0.255 33 Na 1 0.03 0.1 0.12 0.18 0.25 0.28 33 Na 3 0.05 0.08 0.1 0.18 0.445 0.145 33 Na 9 0.06 0.13 0.17 0.34 0.175 0.1 33 Na 20 0.06 0.18 0.2 0.73 0.145 0.1 33 Na 41 0.03 0.25 0.24 1.095 0.165 0 33 Na 100 0.15 0.63 0.66 2.255 0.14 0.14 33 Na 153 0.1 0.5 0.75 1.815 0.545 0.12 er Na 0.04 0 0.01 0.02 0.055 0.06 0.06 er Na 0.08 0 0.02 0.04 0.06 0.07 0.045 er Na 0.25 0 0 0 0.045 0.07 0.04 er Na 1 0 0.01 0 0.09 0.07 0.055 er Na 3 0 0.05 0 0.175 0.09 0.065 er Na 9 0 0.07 0.03 0.165 0.145 0.08 er Na 20 0.04 0.05 0.05 0.095 0.235 0.13 er Na 41 0.04 0.07 0.05 0.05 0.04 0.11 er Na 100 0.1 0.09 0.09 0.14 0.1 0.14 er Na 153 0.1 0 0.1 0.145 0.1 0.085 gyp Na 0.04 0.87 0.95 1.35 0 0 0 gyp Na 0.08 0.24 0.26 0.46 0 0 0 gyp Na 0.25 0.05 0.07 0.14 0 0 0 gyp Na 1 0 0.03 0.07 0.11 0 0.11 gyp Na 3 0.04 0.05 0.03 0.085 0.15 0.13 gyp Na 9 0.03 0.04 0.05 0.06 0.115 0.085 gyp Na 20 0.04 0.04 0.05 0.11 0.065 0.055 GYP Na 41 0.05 0.06 0.07 0.135 0.065 0.03 gyp Na 100 0.15 0.18 0.13 0.5 0.105 0.06 gyp Na 153 0.1 0.1 0.1 0.37 0.08 0.06 mr Na 0.04 1.56 1.55 2.51 2.155 2.635 2.205 mr Na 0.08 0.48 0.72 0.98 1.545 1.305 1.32 mr Na 0.25 0.23 0.5 0.77 1.115 0.62 0.49 mr Na 1 0.22 0.82 0.95 1.915 1.78 0.325 mr Na 3 0.26 1.28 0.92 3.42 1.61 0.64 mr Na 9 0.27 2.06 1.15 4.375 1.33 0.63 mr Na 20 0.27 3.32 0.95 5.99 1.67 1.035 MR Na 41 0.28 2.87 1.5 7.625 1.63 1.615 mr Na 100 1.04 4.95 2.9 13.82 2.8 0.825 mr Na 153 1.15 4.4 3.1 6.9 1.19 1.7 2 Ni 0.04 0.03 0.03 0.03 0.01808 0.019585 0.013555 2 Ni 0.08 0.01 0 0 0.03323 0.04229 0.03927 2 Ni 0.25 0.02 0.01 0 0.00534 0.0115633 0.14126333 2 Ni 1 0 0 0.01 0.0063 0.01445 0 2 Ni 3 0.01 0.01 0.01 0.039675 0.02222 0.035055 2 Ni 9 0 0.02 0.01 0.03578 0.017265 0.01083 2 Ni 20 0 0.04 0.01 0.044405 0.036785 0.02726 2 Ni 41 0 0.02 0.01 0.039195 0.0404 0.0146 2 Ni 100 0.01 0.03 0.01 0.03836 0.017725 0.013215 2 Ni 153 0 0 0.02 0.02494 0.01479 0.01248 9 Ni 0.04 0 0.01 0.01 0.009035 0 0.00301 9 Ni 0.08 0 0 0 0.02719 0.03172 0.018125 9 Ni 0.25 0 0.01 0.01 0.00331 0.00993 0.014895 9 Ni 1 0 0 0 0 0.01007 0 9 Ni 3 0 0.01 0 0.00693 0 0.00965 9 Ni 9 0 0 0 0 0 0.00299 9 Ni 20 0 0.01 0.01 0.01497 0.027225 0.017275 9 Ni 41 0 0 0 0.023265 0.011085 0.00967 9 Ni 100 0 0 0 0.039335 0.01574 0.00537 9 Ni 153 0.01 0 0.01 0.02073 0.006735 0.00587 11 Ni 0.04 0.01 0.01 0.02 0 0 0.00452 11 Ni 0.08 0 0.01 0 0.031213 0.022655 0.030205 11 Ni 0.25 0.04 0.01 0.01 0.00331 0.00662 0.01324 11 Ni 1 0 0 0 0.010725 0.00489 0.00879333 11 Ni 3 0 0 0 0.007695 0.001535 0.01704 11 Ni 9 0 0.01 0 0 0.006375 0 11 Ni 20 0 0.01 0 0.01192 0.008755 0.01161 11 Ni 41 0 0 0 0.00137 0.00212 0.00124 11 Ni 100 0 0.01 0.01 0.016215 0.011535 0 11 Ni 153 0 0 0 0.012725 0.01474 0.006725 16 Ni 0.04 0.01 0 0 0.01959 0.00301 0 16 Ni 0.08 0 0 0 0.022655 0.0151 0.021145 16 Ni 0.25 0.01 0 0.01 0.00331 0.0107575 0.01655 16 Ni 1 0.01 0.02 0.01 0.002715 0.007155 0.00851 16 Ni 3 0.01 0.01 0.01 0.012525 0.006155 0 16 Ni 9 0 0 0 0.003385 0 0 16 Ni 20 0.01 0.01 0.01 0.02298 0.024 0.012285 288 Appendix (mg/L) A B C A B C ID Element Day DDW HOAc HN03 Cit-lowpH cit-medpH cit-highpH 16 Ni 41 0 0 0 0.015155 0.004025 0.00311 16 Ni 100 0 0.01 0 0.027105 0.01078 0.007445 16 Ni 153 0.01 0 0 0.010485 0.00492 0.0033 22 Ni 0.04 0.01 0.01 0.01 0.00753 0.009035 0.016125 22 Ni 0.08 0 0.01 0 0.03474 0.049845 0.04078 22 Ni 0.25 0.01 0.02 0.01 0.017653 0.020735 0.01777 22 Ni 1 0 0.03 0.03 0.033055 0.03152 0.0246 22 Ni 3 0.01 0.02 0.02 0.07771 0.03721 0.02946 22 Ni 9 0 0.04 0.02 0.09763 0.03047 0.01083 22 Ni 20 0 0.05 0.02 0.087365 0.063345 0.030355 22 Ni 41 0 0.04 0.03 0.058875 0.07241 0.021655 22 Ni 100 0.01 0.05 0.04 0.071585 0.103495 0.03445 22 NI 153 0.01 0 0.02 0.037865 0.04009 0.022645 27 Ni 0.04 0.04 0.04 0.05 0.033195 0.04041 0.02886 27 • Ni 0.08 0 0.02 0 0.03776 0.027185 0.036245 27 Ni 0.25 0 0.01 0.01 0.01925 0.01777 0.010365 27 Ni 1 0.01 0 0.01 0.023103 0.02259 0.01277 27 Ni 3 0.01 0.01 0.01 0.03254 0.002105 0.01175 27 Ni 9 0.01 0.01 0 0.02172 0.0079 0.00254 27 Ni 20 0.01 0.03 0.01 0.0503 0.042645 0.01858333 27 Ni 41 0 0.02 0 0.026825 0.04082 0.012275 27 Ni 100 0 0.02 0 0.049785 0.04631 0.01268 27 Ni 153 0 0 0.01 0.01967 0.01584 0.018525 31 Ni 0.04 0.03 0.02 0.02 0.02309 0.030305 0.02742 31 Ni 0.08 0.01 0.01 0.01 0.021145 0.025675 0.03021 31 Ni 0.25 0 0.01 0 0.01333 0.017775 0.011845 31 Ni 1 0.01 0 0.01 0.02795 0.00491 0.013005 31 Ni 3 0.01 0 0.01 0.01216 0.001485 0 31 Ni 9 0.01 0 0.02 0.00699 0.00853 0.004335 31 Ni 20 0.01 0.02 0 0.02873 0.0209867 0.009505 31 Ni 41 0 0 0 0.020265 0.010055 0.00245 31 Ni 100 0.01 0.01 0 0.02816 0.05056 0.004945 31 Ni 153 0.01 0 0.01 0.0217 0.018675 0.012205 33 Ni 0.04 0.03 0.04 0.02 0.03608 0.03608 0.03031 33 Ni 0.08 0.01 0.01 0.01 0.03172 0.03021 0.03826333 33 Ni 0.25 0.01 0.01 0.01 0.00444 0.00592 0.01629 33 Ni 1 0.06 0.01 0.01 0.012535 0.010345 0.014545 33 Ni 3 0.01 0.01 0.01 0.005385 0 0.00734 33 Ni 9 0.04 0 0.02 0.01443 0 0.015675 33 Ni 20 0 0.01 0 0.01558 0.009635 0.0089 33 Ni 41 0.01 0 0.02 0.002955 mixed 0.000275 33 Ni 100 0 0.01 0 0.012765 0.004895 0.011745 33 Ni 153 0 0 0 0.00891 0.00691 0.00582 er Ni 0.04 0.01 0.01 0.01 0.033195 0.02309 0.015875 er Ni 0.08 0.01 0.01 0.01 0.03625 0.027185 0.030205 er Ni 0.25 0 0 0.01 0.010365 0.01333 0.00296 er Ni 1 0.01 0.01 0.01 0.01141 0 0.009635 er Ni 3 0.01 0 0.01 0.009085 0 0.002455 er Ni 9 0.01 0 0 0.001565 0 0.016135 er Ni 20 0 0.02 0 0.00971 0.004865 0.00858 er Ni 41 0.02 0 0.02 0 0 0 er Ni 100 0 0 0 0.027355 0.00407 0 er Ni 153 0.01 0 0 0.003395 0.003145 0.01055 gyp Ni 0.04 0.01 0.01 0.01 0.01154 0.00577 0 gyp Ni 0.08 0.01 0 0 0.02265 0.027185 ppte gyp Ni 0.25 0 0 0 0.012824 0.013006 0.03889667 gyp Ni 1 0.03 0.01 0 0.002045 0.0058 0.000715 gyp Ni 3 0 0 0 0.00636 0.003995 0.007285 gyp Ni 9 0 0.01 0.02 0.02434 0.017195 0.01146333 gyp Ni 20 0 0.02 0.02 0.005565 0.018205 0.00828 GYP Ni 41 0.03 0 0.02 0 0.01259 0.003745 gyp Ni 100 0.01 0.01 0.01 0.00237 0.000355 0.000915 gyp Ni 153 0.01 0 0.01 0.00525 0.008515 0.007835 mr Ni 0.04 0.31 0.34 0.32 0.15877 0.193415 0.1151675 mr Ni 0.08 0.07 0.08 0.08 0.22507 0.22507 0.240175 mr Ni 0.25 0.02 0.03 0.03 0.075878 0.0296425 0.05477 mr Ni 1 0.02 0.02 0.02 0.03254 0.031925 0.01699 mr Ni 3 0.03 0.02 0.03 0.06025 0.03449 0.04875 mr Ni 9 0.05 0.03 0.03 0.03568 0.032 0.082715 mr Ni 20 0.07 0.05 0.06 0.051995 0.07735 0.1308 MR Ni 41 0.06 0.07 0.08 0.041 0.04585 0.115605 mr Ni 100 0.12 0.12 0.15 0.12817 0.1753 0.33311 mr Ni 153 0.14 0.02 0.13 0.09122 0.11753 0.215065 2 Pb 0.04 0 0.02 0 0 0 0 2 Pb 0.08 0 0 0 0 0 0 2 Pb 0.25 0.03 0 0 0 0 0.036944 2 Pb 1 0.02 0.02 0.01 0.072043 0.08334 0.01889 2 Pb 3 0 0 0.01 0 0 0 2 Pb 9 0 0 0 0 0 0 289 Appendix (mg/L) A B c A B C ID Element Day DDW HOAc HN03 cit-lowpH cit-medpH cit-highpH 2 Pb 20 0.02 0.01 0.08 0 0 0 2 Pb 41 0 0.01 0 0 0 0 2 Pb 100 0 0 0 0 0 0 2 Pb 153 0.01 0 0.01 0.047865 0.03995 0.04682 9 Pb 0.04 0 0 0 0 0 0 9 Pb 0.08 0 0.01 0 0 0 0 9 Pb 0.25 0.01 0 0 0 0 0 9 Pb 1 0.03 0 0.02 0.12043 0.0693567 0.060145 9 Pb 3 0.01 0 0.01 0.126433 0.013875 0 9 Pb 9 0.01 0 0 0.043875 0 0 9 Pb 20 0.02 0 0.04 0.00217 0 0 9 Pb 41 0 0 0 0 0 0 9 Pb 100 0 0 0 0 0 0 9 Pb 153 0.02 0 0.02 0.04973 0.032365 0.061635 11 Pb 0.04 0 0 0 0 0 0 11 Pb 0.08 0 0 0 0 0 0 11 Pb 0.25 0.02 0.02 0.03 0 0 0 11 Pb 1 0.02 0.03 0.02 0.07584 0.04435 0 11 Pb 3 0.01 0 0.02 0.01665 0 0 11 Pb 9 0 0.06 0 0.03055 0 0 11 Pb 20 0.03 0.01 0.02 0.04602 0.04777 0 11 Pb 41 0 0 0 0 0 0 11 Pb 100 0 0 0.04 0 0 0 11 Pb 153 0.02 0 0.04 0.057195 0.05825 0 16 Pb 0.04 0 0.01 0 0 0 0 16 Pb 0.08 0 0.01 0 0 0 0 16 Pb 0.25 0.01 0 0 0 0 0 16 Pb 1 0.02 0.04 0.02 0.02531 0 0 16 Pb 3 0.01 0 0 0.00409 0 0 16 Pb 9 0 0 0.01 0.03996 0 0 16 Pb 20 0.02 0.02 0.03 0.04571 0 0 16 Pb 41 0.04 0.02 0 0 0 0 16 Pb 100 0 0 0.02 0 0 0 16 Pb 153 0.01 0 0.01 0.042055 0.00606 0.012465 22 Pb 0.04 0 0.05 0 0 0 0 22 Pb 0.08 0 0.01 0 0 0 0 22 Pb 0.25 0 0 0 0 0 0 22 Pb 1 0.02 0.03 0.01 0 0 0 22 Pb 3 0.02 0 0.01 0 0 0 22 Pb 9 0.01 0 0.01 0 0 0 22 Pb 20 0.03 0 0.02 0 0 0 22 Pb 41 0 0.01 0 0 0 0 22 Pb 100 0 0 0.07 0 0 0 22 Pb 153 0.02 0 0 0.024545 0 0.006185 27 Pb 0.04 0 0 0 0 0 0 27 Pb 0.08 0 0 0 0 0 0 27 Pb 0.25 0.04 0 0.04 0 0 0 27 Pb 1 0.01 0 0.02 0 0 0 27 Pb 3 0.01 0 0.02 0 0 0 27 Pb 9 0.01 0 0.01 0 0 0 27 Pb 20 0.02 0.01 0.04 0 0 0 27 Pb 41 0 0 0 0 0 0 27 Pb 100 0.02 0 0 0 0 0 27 Pb 153 0.02 0 0 0 0.006475 0.04937 31 Pb 0.04 0 0 0 0 0 0 31 Pb 0.08 0 0 0.01 0 0 0 31 Pb 0.25 0.01 0 0.03 0 0 0 31 Pb 1 0.02 0.02 0.02 0.011985 0 0 31 Pb 3 0.01 0 0.01 0 0 0 31 Pb 9 0.02 0 0.01 0 0 0 31 Pb 20 0 0 0 0 0 0 31 Pb 41 0 0.01 0 0 0 0 31 Pb 100 0 0 0.06 0 0 0 31 Pb 153 0.01 0 0 0.066495 0.04062 0 33 Pb 0.04 0 0 0 0 0 0 33 Pb 0.08 0.02 0 0 0 0 0 33 Pb 0.25 0.03 0.01 0.02 0 0 0 33 Pb 1 0.06 0 0 0.012125 0 0 33 Pb 3 0.01 0.01 0 0 0 0 33 Pb 9 0.05 0 0.02 0 0 0 33 Pb 20 0.01 0.02 0.02 0 0 0 33 Pb 41 0 0 0 0 mixed 0 33 Pb 100 0 0.1 0.03 0 0 0 33 Pb 153 0 0 0.01 0.01307 0.03307 0.02969 er Pb 0.04 0 0 0 0.0287 0.13569 0.09916 er Pb 0.08 0 0.01 0 0 0 0 er Pb 0.25 0.01 0.04 0 0 0 0.07439 er Pb 1 0 0 0 0.01378 0.02381 0 er Pb 3 0 0 0 0.062825 0.069985 0 290 Appendix (mg/L) A B C A B C ID Element Day DDW HOAc HN03 cit-lowpH cit-medpH oit-highpH er Pb 9 0.02 0 0 0.069973 0.206925 0 er Pb 20 0 0 0 0 0.41614 0.01496 er Pb 41 0 0 0 0 0.04627 0.01166 er Pb 100 0 0 0 0 0 0 er Pb 153 0.02 0 0 0.026125 0 0.0419 gyp Pb 0.04 0 0.03 0.04 0 0 0 gyp Pb 0.08 0.04 0.01 0 0 0 ppte gyp Pb 0.25 0 0.05 0.01 0 0 • 0 gyp Pb 1 0.0524 0.02 0 0.0057 0 0.004675 gyp Pb 3 0 0.01 0 0.00205 0 0.02118 gyp Pb 9 0.02 0.02 0.05 0 0.00821 0 gyp Pb 20 0 0.03 0.02 0 0 0 GYP Pb 41 0.07 0.02 0 0 0 0 gyp Pb 100 0 0 0 0 0 0 gyp Pb 153 0.03 0 0.01 0.04264 0.02847 0.016035 mr Pb 0.04 0 0.03 0 0 0 0 mr Pb 0.08 0 0 0 0 0 0 mr Pb 0.25 0.01 0.04 0.04 0 0 0 mr Pb 1 0.01 0 0.01 0 0 0 mr Pb 3 0 0 0.02 0 0 0 mr Pb 9 0.02 0 0.02 0 0 0 mr Pb 20 0 0 0 0 0 0 MR Pb 41 0 0 0 0 0 0 mr Pb 100 0.01 0 0.06 0 0 0 mr Pb 153 0 0 0 0 0 0 2 Si 0.04 0.16 0.24 0.21 0.57568 1.34491 2.01985 2 Si 0.08 0.27 0.41 0.31 0.89019 4.565345 13.720905 2 Si 0.25 0.74 0.73 0.6 2.134115 16.141563 13.591028 2 Si 1 0.87 2.4 1.63 9.395573 16.44645 27.639355 2 Si 3 1.05 3.87 2.71 30.1545 79.239155 117.209815 2 Si 9 2.97 10.36 6.38 48.753 76.40704 66.5821967 2 Si 20 3.03 14.04 7.66 83.4552 63.43726 47.378765 2 Si 41 3.26 15.21 8.82 99.90287 69.65359 30.34409 2 Si 100 6.96 25.2 18.71 121.913 42.85088 36.23498 2 Si 153 6.09 24.44 16.87 78.79915 32.09849 17.71895 9 Si 0.04 0.22 0.42 0.34 0.674935 0.337465 0.56575333 9 Si 0.08 0.24 0.71 0.33 0.90511 1.13387 7.16132667 9 Si 0.25 0.42 1.19 0.65 1.80695 3.43831 3.31086 9 Si 1 1.07 3.37 1.36 5.62476 6.6482067 8.73285 9 Si 3 1.71 4.48 2.21 23.27534 51.980005 77.583745 9 Si 9 4.7 7.12 4.94 38.99707 119.89864 92.30461 9 Si 20 5.55 9.58 5.61 68.98669 121.44581 91.69828 9 Si 41 6.57 11.83 6.5 89.21469 90.939775 62.27453 9 Si 100 14.03 22.5 16.02 114.7566 93.771225 50.41817 9 Si 153 12.53 22.2 16.02 71.93998 49.643795 33.082505 11 Si 0.04 0.1 0.13 0.15 0.45161 0.51116 1.702225 11 Si 0.08 0.08 0.27 0.14 0.431 1.661025 5.042765 11 Si 0.25 0.31 0.5 0.4 0.917635 1.77296 6.134585 11 Si 1 0.7 1.19 0.8 3.177295 4.6097 14.0992133 11 Si 3 1.13 1.88 1.55 10.71799 24.79226 59.38717 11 Si 9 2.91 5.64 3.74 18.91838 46.785805 73.250685 11 Si 20 3.51 7.99 4.16 29.43368 44.888595 50.034485 11 Si 41 4.28 6.41 6.59 40.17667 55.311715 18.89741 11 Si 100 9.49 11.46 10.21 68.23893 59.72024 15.85588 11 Si 153 8.57 12.16 10.15 47.09693 40.273385 14.10125 16 Si 0.04 0.12 0.14 0.15 0.233245 0.789075 1.42431 16 Si 0.08 0.18 0.32 0.27 0.56196 3.322055 6.00258 16 Si 0.25 0.3 0.47 0.48 1.16687 4.9195575 8.836515 16 Si 1 0.72 2.08 1.78 5.26315 8.911635 17.67211 16 Si 3 1.22 3.55 2.84 18.06674 27.239675 81.04388 16 Si 9 3.16 6.96 5.37 28.54683 47.76859 76.57713 16 Si 20 4.06 9.05 5.62 50.44492 55.777055 41.718975 16 Si 41 4.52 10.15 6.5 67.51688 67.61862 20.800565 16 Si 100 11.41 15.46 13.92 104.0557 77.794815 23.054305 16 Si 153 25.49 18.19 12.72 70.10553 54.214345 20.748915 22 Si 0.04 0.64 7.5 4.17 4.977665 4.997515 7.13681 22 ' Si 0.08 0.57 10.92 5.57 12.82077 13.696035 22.503475 22 Si 0.25 0.76 15.12 8.85 16.11185 18.53007 25.247005 22 Si 1 1.07 24.57 14.1 26.5975 35.371715 21.032015 22 Si 3 1.68 14.23 16.78 52.33705 69.9169 106.51779 22 Si 9 3.56 21.84 18.9 85.02755 86.18457 58.05096 22 Si 20 3.95 29.03 15.32 123.2358 103.51796 51.983165 22 Si 41 4.58 28.95 18.26 129.988 131.69456 38.687435 22 Si 100 6.27 53.28 24.59 154.3022 179.56065 56.296335 22 Si 153 5.05 36.16 23.06 102.1372 108.66913 41.81174 27 Si 0.04 0.66 1.6 1.26 1.499205 1.19937 1.70566 27 Si 0.08 0.48 2.26 1.35 3.07837 3.157945 4.237115 27 Si 0.25 0.8 3.82 2.08 5.267805 4.300565 5.29901 27 Si 1 1.41 9.59 4.21 15.8536 12.08831 10.395765 291 Appendix (mg/L) A B C A B C ID Element Day DDW HOAc HN03 Cit-lowpH cit-medpH cit-highpH 27 Si 3 1.89 11.39 5.74 43.06674 63.69125 46.507395 27 Si 9 9.78 17.12 10.43 61.78374 145.48209 72.74793 27 Si 20 4.13 20.03 10.81 100.983 114.28226 109.58304 27 Si 41 3.88 20.51 10.04 105.395 121.73249 91.21496 27 Si 100 7.59 37.77 18.27 136.5819 123.47248 71.25743 27 Si 153 5.82 21.99 15.07 85.24199 67.08224 55.14493 31 Si 0.04 0.24 0.5 0.49 0.525945 2.6101 1.46972 31 Si 0.08 0.34 0.84 0.83 4.32663 10.86632 8.837275 31 Si 0.25 0.42 1.59 1.15 2.272485 17.758705 10.743625 31 Si 1 0.99 4.7 2.3 8.16957 11.92799 16.97471 31 Si 3 1.6 6.33 3.52 23.05894 70.715395 67.96936 31 Si 9 3.89 11.27 8.57 35.00689 68.046743 53.89459 31 Si 20 4.58 14.81 9.76 55.97244 72.69024 62.30096 31 Si 41 4.29 16.24 9.31 64.63093 53.632865 40.48885 31 Si 100 8.74 32.02 19 101.2582 68.90792 40.80862 31 Si 153 6.79 23.16 11.42 66.49672 43.67069 25.775855 33 Si 0.04 0.08 1.29 0.38 1.23869 2.89356 1.543445 33 Si 0.08 0.13 1.08 0.46 4.15257 8.514015 8.97155 33 Si 0.25 0.21 1.23 0.62 2.002075 17.15028 16.16744 33 Si 1 0.79 2.14 1.05 5.297505 19.0944 14.497725 33 Si 3 0.46 3.11 3.01 10.22461 50.025965 46.416515 33 Si 9 0.9 5.36 5.22 17.63905 21.11379 18.41999 33 Si 20 0.96 6.51 5.8 35.27589 24.057665 15.685245 33 Si 41 0.9 7.05 5.92 44.51253 mixed 9.24752 33 Si 100 1.89 18.2 14.04 76.44366 29.06314 14.25739 33 Si 153 1.54 14.42 7.91 44.83949 21.276545 10.08504 er Si 0.04 1.2 0.37 0.17 1.22886 0.560355 0.756975 er Si 0.08 3.49 0.16 0.2 46.31987 0.835485 34.712545 er Si 0.25 1.84 0.2 0.18 2.84971 19.31877 1.424855 er Si 1 1.01 0.36 0.34 0.68022 0.7558 2.04754 er Si 3 0.75 0.69 0.58 1.29187 4.278105 7.80316 er Si 9 1.21 1.13 1.41 1.71973 1.743245 10.65094 er Si 20 1.71 1.55 1.76 4.02022 3.63036 18.574485 er Si 41 1.85 2.5 1.7 4.437605 7.564045 20.05364 er Si 100 4.92 3.36 4.36 7.72345 15.505965 32.34276 er Si 153 10.09 2.59 6.85 4.557185 7.734085 8.98303 gyp Si 0.04 0.5 0.44 0.45 0.604595 0.452215 1.12072 gyp Si 0.08 0.5 0.57 0.64 1.521775 0.711155 ppte gyp Si 0.25 0.85 0.87 0.83 2.360278 1.316934 3.47066 gyp Si 1 0.76 2.01 0 9.990905 3.648395 5.959485 gyp Si 3 1.01 4.37 4.04 25.42197 9.36769 11.78265 gyp Si 9 1.17 10.97 10 34.67351 25.53405 18.85328 gyp Si 20 1.1 15.74 12.97 37.17793 41.96051 35.2122 GYP Si 41 1.05 14.35 13.2 25.38772 51.95865 30.6893125 gyp Si 100 3.41 25.62 19.27 24.88505 28.090855 23.628035 gyp Si 153 3.93 17.26 14.95 9.016425 5.612445 8.40197 mr Si 0.04 0.2 3.9 3 5.343095 4.98918 1.7273825 mr Si 0.08 0.34 5.93 3.58 17.76407 11.34374 3.58563 mr Si 0.25 0.63 8.49 5.21 12.33343 7.993705 4.4582975 mr Si 1 1.43 13.51 9.06 24.30537 18.0927 6.70605 mr Si 3 2.79 22.71 14.9 59.64304 36.7741 32.911555 mr Si 9 6.49 36.14 20.36 84.75917 53.54695 39.802495 mr Si 20 9.15 43.79 29.32 126.1044 88.91204 85.695665 MR Si 41 11.77 45.18 31.31 117.2509 85.85237 86.520665 mr Si 100 42.95 59.32 59.37 138.0394 109.94642 62.553245 mr Si 153 36.21 51.5 49.27 93.3078 88.40999 29.80319 2 Zn 0.04 0.14 0.15 0.16 0.097265 0.119235 0.14343 2 Zn 0.08 0.04 0.06 0.04 0.076965 0.073395 0.070235 2 Zn 0.25 0.02 0.03 0.02 0.03899 0.05603 0.135692 2 Zn 1 0.01 0.04 0.04 0.077617 0.06763 0.079305 2 Zn 3 0.01 0.04 0.03 0.201085 0.21236 0.2936 2 Zn 9 0.01 0.09 0.05 0.2948 0.23207 0.18735333 2 Zn 20 0.01 0.1 0.05 0.33385 0.17772 0.10933 2 Zn 41 0.01 0.1 0.04 0.385815 0.215785 0.07179 2 Zn 100 0.03 0.13 0.07 0.49583 0.14581 0.094295 2 Zn 153 0.03 0.1 0.05 0.24075 0.1277 0.048805 9 Zn 0.04 0.07 0.09 0.08 0.07126 0.08145 0.07678 9 Zn 0.08 0.01 0.04 0.02 0.025015 0.024175 0.03824333 9 Zn 0.25 0.01 0.02 0.01 0.028295 0.02993 0.02879 9 Zn 1 0 0.05 0.01 0.031045 0.0244433 0.0215 9 Zn 3 0 0.05 0 0.11996 0.096045 0.071005 9 Zn 9 0 0.05 0.01 0.15039 0.191305 0.11263 9 Zn 20 0.01 0.04 0.02 0.151925 0.129455 0.08226 9 Zn 41 0 0.04 0.02 0.21042 0.10752 0.06045 9 Zn 100 0.01 0.1 0.03 0.31908 0.156395 0.062865 9 Zn 153 0.01 0.07 0.04 0.16625 0.08757 0.04232 11 Zn 0.04 0.22 0.23 0.23 0.171905 0.15426 0.189005 11 Zn 0.08 0.04 0.06 0.03 0.094523 0.10633 0.09166 11 Zn 0.25 0.04 0.02 0.02 0.030265 0.045515 0.04709 292 Appendix (mg/L) A B C A B C ID Element Day DDW HOAc HN03 cit-lowpH cit-medpH cit-highpH 11 Zn 1 0.01 0.02 0.01 0.012095 0.0208733 0.03267333 11 Zn 3 0 0.01 0.01 0.03423 0.050565 0.08694667 11 Zn 9 0.01 0.07 0.02 0.07051 0.105595 0.122295 11 Zn 20 0.01 0.02 0.02 0.093595 0.0805 0.083725 11 Zn 41 0.01 0.02 0.03 0.14329 0.10699 0.0406 11 Zn 100 0.03 0.04 0.05 0.275435 0.133345 0.05034 11 Zn 153 0.03 0.03 0.05 0.15799 0.084835 0.03616 16 Zn 0.04 0.06 0.06 0.06 0.041115 0.043605 0.059745 16 Zn 0.08 0.01 0.02 0.02 0.015805 0.020065 0.019165 16 Zn 0.25 0 0 0.01 0.01272 0.0230525 0.034275 16 Zn 1 0.01 0.02 0 0.0061 0.01426 0.02291 16 Zn 3 0 0.01 0.01 0.034845 0.025405 0.05687 16 Zn 9 0 0.02 0.01 0.0895 0.04731 0.055615 16 Zn 20 0.01 0.02 0.01 0.155345 0.068095 0.039075 16 Zn 41 0.01 0.03 0.02 0.2305 0.09002 0.031515 16 Zn 100 0.01 0.05 0.03 0.40424 0.15049 0.0565 16 Zn 153 0.02 0.05 0.03 0.21013 0.08799 0.035225 22 Zn 0.04 0.33 0.41 0.4 0.316845 0.343895 0.40342 22 Zn 0.08 0.08 0.22 0.12 0.4712 0.33918 0.210665 22 Zn 0.25 0.03 0.09 0.08 0.26487 0.1960167 0.168815 22 Zn 1 0.01 0.1 0.11 0.17481 0.15568 0.089825 22 Zn 3 0.01 0.07 0.09 0.286115 0.191445 0.21878 22 Zn 9 0.02 0.09 0.07 0.295405 0.205145 0.19721 22 Zn 20 0.02 0.1 0.06 0.252465 0.13639 0.082165 22 Zn 41 0.02 0.09 0.06 0.26878 0.181365 0.056305 22 Zn 100 0.07 0.15 0.11 0.393375 0.279815 0.091325 22 Zn 153 0.06 0.09 0.08 0.213195 0.14436 0.04835 27 Zn 0.04 0.24 0.32 0.27 0.252405 0.22607 0.223335 27 Zn 0.08 0.06 0.11 0.08 0.23297 0.13879 0.130725 27 Zn 0.25 0.03 0.05 0.05 0.11716 0.068855 0.08972 27 Zn 1 0.02 0.08 0.04 0.122063 0.0613767 0.06456 27 Zn 3 0.02 0.08 0.03 0.228475 0.16134 0.105515 27 Zn 9 0.05 0.09 0.04 0.1719 0.26746 0.144635 27 Zn 20 0.02 0.07 0.04 0.16541 0.11421 0.09620333 27 Zn 41 0.01 0.06 0.02 0.17877 0.12331 0.076845 27 Zn 100 0.03 0.11 0.05 0.281125 0.166065 0.06349 27 Zn 153 0.03 0.05 0.05 0.14533 0.08662 0.040965 31 Zn 0.04 0.28 0.32 0.26 0.230085 0.34114 0.210695 31 Zn 0.08 0.07 0.07 0.08 0.153655 0.071305 0.136125 31 Zn 0.25 0.02 0.03 0.03 0.058995 0.06106 0.099505 31 Zn 1 0.02 0.07 0.04 0.05019 0.02929 0.0536925 31 Zn 3 0.01 0.05 0.03 0.13347 0.098845 0.08115 31 Zn 9 0.02 0.05 0.04 0.187165 0.17393 0.085205 31 Zn 20 0.02 0.05 0.03 0.19988 0.1373433 0.064545 31 Zn 41 0.01 0.05 0.02 0.264475 0.135445 0.052645 31 Zn 100 0.03 0.1 0.05 0.495465 0.21665 0.060145 31 Zn 153 0.02 0.07 0.04 0.298055 0.14307 0.04716 33 Zn 0.04 0.68 2.84 1.27 2.731395 2.3290033 1.03176 33 Zn 0.08 0.16 0.36 0.73 1.90123 1.6798 1.44860333 33 Zn 0.25 0.05 0.17 0.58 0.616385 0.95191 1.42483 33 Zn 1 0.09 0.09 0.58 0.15624 0.16338 0.860905 33 Zn 3 0.03 0.03 0.14 0.088245 0.083835 0.57353 33 Zn 9 0.06 0.03 0.07 0.082825 0.05119 0.13833 33 Zn 20 0.06 0.03 0.05 0.07427 0.03208 0.036515 33 Zn 41 0.04 0.03 0.03 0.090635 mixed 0.02448 33 Zn 100 0.25 0.09 0.08 0.14984 0.06189 0.03315 33 Zn 153 0.51 0.06 0.09 0.094635 0.037445 0.02059 er Zn 0.04 0 0.01 0.01 0 0 0.00572667 er Zn 0.08 0 0.01 0.01 0 0 0 er Zn 0.25 0.01 0.01 0 0 0.016865 0.008145 er Zn 1 0.01 0.02 0.01 0.010135 0.012205 0.006355 er Zn 3 0 0.01 0.01 0.074165 0.043555 0.00992 er Zn 9 0 0.02 0 0.13566 0.19572 0.028845 er Zn 20 0.01 0.08 0.01 0.103363 0.260375 0.049355 er Zn 41 0.01 0.03 0.01 0.04942 0.029025 0.046525 er Zn 100 0.01 0.03 0.01 0.23709 0.012455 0.040375 er Zn 153 0.01 0.01 0.01 0 0.000365 0.059465 gyp Zn 0.04 0 0.14 0.1 0.102705 0.068415 0.02885 gyp Zn 0.08 0 0.09 0.07 0.118805 0.052595 ppte gyp Zn 0.25 0 0.09 0.08 0.082328 0.074974 0.06823 gyp Zn 1 0 0.12 0 0.151225 0.078835 0.071145 gyp Zn 3 0 0.17 0.18 0.184435 0.097855 0.137315 gyp Zn 9 0 0.22 0.21 0.19298 0.17446 0.15167 gyp Zn 20 0 0.16 0.16 0.116075 0.15307 0.17638 GYP Zn 41 0.01 0.09 0.12 0.081463 0.17013 0.1399625 gyp Zn 100 0.06 0.09 0.09 0.07759 0.0783333 0.109315 gyp Zn 153 0.14 0.04 0.04 0.011745 0.011655 0.040615 mr Zn 0.04 4.22 4.34 4.2 3.477795 3.98242 2.6964875 mr Zn 0.08 0.96 1.3 1.08 2.306285 2.076315 2.083845 293 A p p e n d i x (mg/L) A B C A B C ID Element Day DDW HOAc HN03 cit-lowpH cit-medpH cit-highpH mr Zn 0.25 0.39 0.74 0.57 0.959405 0.56913 0.7284125 mr Zn 1 0.49 1.02 0.76 0.8984 0.768485 0.423345 mr Zn 3 1.06 2.07 1.49 2.03059 1.81591 2.00851 mr Zn 9 2.54 4.12 2.33 2.52921 2.97159 3.11497 mr Zn 20 3.18 4.39 2.94 3.825555 3.0766 3.547245 MR Zn 41 3.01 3.55 2.61 5.156145 3.09193 3.644635 mr Zn 100 8 4.1 7.84 6.716755 3.25937 4.15086 mr Zn 153 4.69 3.5 4.7 2.57297 1.55769 1.980045 2 S04 0.04 223 183 221 143 195 218 2 S04 0.08 45 49 44 112 4 5 2 S04 0.25 10 11 17 33 3 2 S04 1 7 6 8 16 4 2 S04 3 3 4 4 31 10 9 2 S04 9 2 4 2 50 14 498 2 S04 20 3 7 2 21 16 535 2 S04 41 4 11 3 15 186 2 S04 100 4 11 4 2 S04 153 0 5 2 9 S04 0.04 1554 1309 1649 1626 2690 2606 9 S04 0.08 1394 1260 1549 1708 1335 1417 9 S04 0.25 998 1109 772 784 311 341 9 S04 1 258 694 161 239 119 111 9 S04 3 77 247 57 221 104 16 9 S04 9 27 54 19 126 81 15 9 S04 20 24 48 18 70 31 454 9 S04 41 14 15 18 15 15 209 9 S04 100 23 11 15 9 S04 153 17 4 10 11 S04 0.04 1605 1347 1689 1739 1712 2926 11 S04 0.08 1428 1160 1515 1827 2520 1753 11 S04 0.25 1188 1130 1209 1101 649 318 11 S04 1 675 891 516 433 160 70 11 S04 3 164 365 115 195 53 23 11 S04 9 55 127 32 79 55 23 11 S04 20 48 63 14 49 47 492 11 S04 41 37 39 7 12 48 237 11 S04 100 47 48 10 11 S04 153 27 28 8 16 S04 0.04 1386 1128 1405 459 818 1204 16 S04 0.08 698 764 745 957 1039 545 16 S04 0.25 210 326 155 466 332 403 16 S04 1 64 134 46 175 82 10 16 S04 3 21 28 11 67 5 7 16 S04 9 12 13 4 47 10 1312 16 S04 20 14 14 5 33 12 11 16 S04 41 12 16 6 1 11 2 16 S04 100 10 24 8 16 S04 153 2 16 4 22 S04 0.04 1373 1232 1373 462 942 1280 22 S04 0.08 439 568 508 1086 889 496 22 S04 0.25 128 173 129 361 189 51 22 S04 1 40 54 43 91 42 9 22 S04 3 17 14 18 15 6 1166 22 S04 9 10 4 10 1 15 281 22 S04 20 3 1 5 13 257 22 S04 41 5 3 5 16 244 22 S04 100 3 3 5 22 S04 153 3 1 2 27 S04 0.04 1549 1285 1607 1686 2681 2444 27 S04 0.08 1464 1252 1580 1718 1642 1107 27 S04 0.25 1125 1146 1042 977 382 573 27 S04 1 517 839 289 372 82 188 27 S04 3 131 300 66 163 28 8 27 S04 9 45 108 25 17 16 13 27 S04 20 21 28 16 2 18 194 27 S04 41 14 10 15 14 200 27 S04 100 11 4 14 27 S04 153 6 1 7 31 S04 0.04 1070 965 965 541 1021 710 31 S04 0.08 301 355 254 224 104 211 31 S04 0.25 54 92 26 123 78 90 31 S04 1 33 73 32 54 5 6 31 S04 3 18 56 16 85 15 13 31 S04 9 11 33 16 67 27 483 31 S04 20 19 35 24 60 35 487 31 S04 41 17 17 24 25 28 221 31 S04 100 25 30 123 31 S04 153 15 19 68 33 S04 0.04 311 549 397 389 413 277 294 Appendix (mg/L) A B C A B C ID Element Day DDW HOAc HN03 cit-lowpH cit-medpH cit-highpH 33 S04 0.08 69 118 84 81 73 81 33 S04 0.25 14 18 95 46 6 7 33 S04 1 8 6 61 13 6 472 33 S04 3 4 2 15 3 8 7 33 S04 9 3 1 6 1 5 6 33 S04 20 5 1 4 0 4 261 33 S04 41 10 3 7 0 33 S04 100 35 3 32 33 S04 153 30 2 42 ER S04 0.04 8 9 2 4 5 4 ER S04 0.08 3 4 2 0 2 1 ER S04 0.25 1 1 1 19 14 ER S04 1 4 14 11 118 124 324 ER S04 3 4 51 15 260 439 1 ER S04 9 8 169 30 231 368 226 ER S04 20 35 182 42 789 412 447 ER S04 41 37 2996 36 147 394 384 ER S04 100 74 178 48 ER S04 153 55 174 37 GYP S04 0.04 1666 1221 1736 1838 5079 4484 GYP S04 0.08 1568 1203 1665 3056 7325 9214 GYP S04 0.25 1535 1115 1632 1869 4014 3688 GYP S04 1 1568 1152 1682 1922 2600 1131 GYP S04 3 1337 1057 1567 1825 1876 182 GYP S04 9 1557 1156 1660 1999 248 41 GYP S04 20 1515 1238 1623 1838 20 13 GYP S04 41 3604 3851 3694 2628 21 2672 GYP S04 100 243 237 242 GYP S04 153 250 247 253 MR S04 0.04 404 457 421 239 343 249 MR S04 0.08 90 109 108 26 43 56 MR S04 0.25 34 41 46 89 4 3 MR S04 1 31 56 50 125 205 297 MR S04 3 25 79 39 177 4 455 MR S04 9 47 103 44 106 7 502 MR S04 20 75 106 67 74 11 16 MR S04 41 93 107 90 55 21 485 MR S04 100 202 183 203 MR S04 153 197 161 191 295 

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