British Columbia Mine Reclamation Symposium

Assessment of the Huckleberry Mine site for potential passive or semi-passive acid rock drainage treatment… Haakensen, Monique; Friesen, Vanessa; Martz, Rachel; Wong, Marke; Liang, Jenny; Qualtiere, Elaine 2016

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108  ASSESSMENT OF THE HUCKLEBERRY MINE SITE FOR POTENTIAL PASSIVE OR SEMI-PASSIVE ACID ROCK DRAINAGE TREATMENT OPTIONS   Monique Haakensen, Ph.D., RP.Bio., P.Bio., EP.1 Vanessa Friesen, Ph.D., EPt.1 Rachel Martz, B.Sc.1 Marke Wong, B.Sc., EP.2 Jenny Liang, B.Sc., BIT.1 Elaine Qualtiere, M.Sc.1   1Contango Strategies Limited Saskatoon, Saskatchewan, Canada.  2Huckleberry Mines Ltd. Vancouver, British Columbia, Canada    ABSTRACT   Passive water treatment is often sought as a component of long-term mine closure scenarios, as it promotes relatively self-sustaining beneficial conditions for impacted water management at low maintenance and operational costs. However, owing to the biogeochemical nature of these technologies, a site-specific phased approach is necessary for successful implementation. Huckleberry Mine was evaluated for the viability of passive water treatment technologies to address potential future acid rock drainage (ARD)-impacted waters containing constituents such as aluminum and copper. Natural wetlands, seepage collection ponds, and ARD-impacted areas were assessed using genetic microbial community profiling, paired with traditional growth-based microbial characterization and quantification. This information was evaluated in the context of water chemistry, treatment objectives, and biogeochemical processes to develop a conceptual treatment train to semi-passively treat water. A phased program was then developed to determine if each step of the treatment train could address its goals individually, or if it would be best implemented to reduce costs associated with an equivalent active water treatment step.   1.  KEY WORDS   Passive water treatment, sustainability, biogeochemistry, microbial community profiling, constructed wetland treatment systems, mine closure planning.      109  INTRODUCTION  Huckleberry Mines Ltd. (Huckleberry Mine) is a copper and molybdenum mine located in west central British Columbia, 123 km southwest of Houston. In 2007, a significant portion of the East Zone Pit (EZP) north slope failed into the pit. The EZP slide material is potentially acid generating (PAG), and is predicted to become a source of acid rock drainage (ARD), potentially resulting in elevated levels of copper, and other metals. Contango Strategies Ltd. (Contango) was contracted to perform a site assessment to evaluate the feasibility of improving water quality from the EZP to meet discharge objectives.     Site-specific designs and phased testing are imperative for developing an effective, robust, and predictable water treatment plan. Options for water quality improvement were considered for feasibility and cost, with a focus on passive constructed wetlands, but other passive and semi-passive treatment systems such as in pit treatment and bioreactors were also considered. The existing latent capacity at the site for natural biogeochemical processes that drive passive treatment was also considered in terms of augmenting treatment plans, through customized site-specific design.   Microbes are considered the driving force of many pathways found in passive treatment systems because they utilize biogeochemical cycles for remediation of specific components of concern.  Attentive passive treatment design can create conditions needed to enhance microbial abundance and metabolic activity specially tailored for a particular site and targeted treatment processes.  The natural treatment capacity was therefore evaluated through a site assessment at the Huckleberry Mine, wherein a comprehensive analysis of vegetation, soil, and associated microbes were explored in the context of water chemistry to provide a framework for how existing processes were operating on site. Options for long-term remediation and improvement of water quality were then assessed using the context of the site-specific framework.  SAMPLING LOCATIONS AND METHODS  Seven locations were selected for sample collection at the Huckleberry Mine site to evaluate the natural treatment capacity and assess the feasibility of passive or semi-passive water treatment (Figure 1; Table 1).  Site selection was based on historical information, and in situ measurements and observations made during the site assessment. Soil, water, microbial, and vegetation samples were collected for analytical testing, see (Contango 2015a; Appendix A) for further details on methods.  110   Wetland plant species relevant to passive water treatment were identified during the site assessment. These included the emergent macrophytes Carex lenticularis (commonly known as Kellogg’s sedge), Carex utriculata (commonly known as common beaked sedge), Typha latifolia (commonly known as broad leaf cattail), and aquatic bryophytes (aquatic moss). In situ field measurements included temperature, dissolved oxygen (DO), conductivity (and specific conductivity; SPC), pH, and oxidation-reduction potential (ORP, redox) using a YSI ProPlus meter. Soil redox potential measurements were taken using platinum tip probes and Calomel electrodes to measure the flux of electrons between the sediment/soil/pore water and overlying water column (Faulkner et al., 1989; Huddleston & Rodgers, 2008). Genetic- and growth-based analyses were performed to assess presence, abundance, identity and diversity of bacteria naturally found at the Huckleberry Mine site. Microbial communities were also tested for their ability to reduce sulphur compounds, iron, selenium and molybdenum by the most probable number (MPN) growth-based method (Contango 2015a).     Figure 2 Map of Huckleberry Mine site showing sample locations (star on smaller map denotes mine location in British Columbia, Canada 111   Table 1 Site description and selection rationale for sampling locations during the Huckleberry Mine site assessment Location Site Description Samples Collected  Non-acid generating (NAG) pond  Natural wetland, south of NAG quarry.  Abundance of wetland vegetation including C. utriculata, and  C. aquatilis which were intermixed with mosses. Water, soil, and C. utriculata vegetation was collected for analytical testing, including aboveground biomass and roots.  SC1* Seepage Collection Pond 1, consists of a small cobble channel that opens up into small pool formed behind a flume.  Red staining found along shore. This site hosts a variety of wetland plants including C. lenticularis.   Water samples were collected in the pool before the flume.  Aboveground biomass of C. lenticularis was collected for analytical testing.  SC3-up* Seepage Collection Pond 3, found at toe of tailings dam.  Rock bottom is covered with fluffy periphyton and red precipitates. Site hosts an abundance of C. lenticularis. Roots, soil, and biofilm on underwater leaves of C. lenticularis were collected for microbial analyses, while aboveground plant biomass was collected for analytical testing.   SC8-mid Small seepage-fed creek that flows into the mid-point of Seepage Collection Pond 8.   Stream had an orange tinted biofilm and a small stand of C. lenticularis. C. lenticularis roots and surrounding soil were collected for microbial analysis, while aboveground plant biomass was collected for analytical testing.   SC8-pump* Southeast corner of Seepage Collection Pond 8 near pump.  Bottom of pond had a fine sediment overlying cobble; clear water was present with T. latifolia growing at this location. Water, soil, plant, and microbial samples were collected for analyses.   Pond 9A* Large wetland south of the Tailing Management Facility dominated by C. lenticularis in a range of water depths.  Aquatic moss was also present.  Soils were very fine clay and silt.  The above-ground vegetation from C. lenticularis was taken for analytical testing.  Water and soil samples were also obtained.  A sulphide smell was noted as plants were extracted from the soil for analysis. EZP-edge Collection channel for potentially acidic runoff from the north side of the EZP tailings area.  Surface oxidation observed presently at the EZP edge and is pre-existing prior to the 2007 slide (natural); and provides an opportunity for assessing treatability processes prior to any predicted acid onset. No vegetation present at time of sampling.  Soil and water samples were collected.  *denotes sites which have historical monitoring stations present        112  RESULTS AND DISCUSSION  Analyses and related biogeochemical and stoichiometric interpretations were undertaken to describe water and soil quality parameters across the study site as they pertained to plant and microbial communities of interest.  Water In situ water measurements are summarized for each site in Table 2.  Results show that the natural surface oxidation observed presently at the EZP edge (and is pre-existing prior to the 2007 slide) had the lowest pH of 4.41, relative to the other sites which were typically circumneutral to slightly basic (6.58-8.05).  Water ORP was nearly always oxidizing (i.e., positive ORP), with the exception of Pond 9A which was mildly reducing and had the lowest recorded DO at 4.2 mg/L. Comparisons with historical data indicated that most parameters measured during the site assessment were typically within historical ranges (Contango, 2015a; Appendix C). Treatment of most elements could be improved by enhancing reducing conditions through the construction of an anaerobic Constructed Wetland Treatment System (CWTS) to create improved hydrology, increased vegetation cover, and abundance of sulphate-reducing bacteria (to remineralize dissolved sulphide minerals).  Table 2 Field in-situ measurements for Huckleberry Mine sampling sites  Site Plants Soil Water Dominant Emergent Macrophyte Relative Soil Redox (mV) Temp (°C) DO (mg/L) SPC (µs/cm) pH ORP (mV) NAG Pond C. utriculata -34 6.3 6.55 208 7.51 +113.3 SC1 C. lenticularis -50 6.8 9.75 2070 7.57 +240.2 SC3-up C. lenticularis +138 10.5 7.48 2431 7.43 +238.6 SC8-mid C. lenticularis -31 5.3 13.34 1738 8.09 +208.6 SC8-pump T. latifolia +130 12.2 8.16 1219 7.96 +195.3 Pond 9A C. lenticularis -186 8.8 4.20 1113 6.58 -48.9 EZP-edge None NT 4.8 9.66 2424 4.41 +400.6  Soils Total elemental concentrations found in the soils were consistent among most sites at Huckleberry Mine.  Leachable elements were relatively low with negative soil redox (Table 2) at the majority of sites indicating reducing environments where soils are producing electrons.  Exceptions were SC3-up and SC8-pump which had a positive soil redox, suggesting that these soils are more prone to oxidization.  These areas had large fluctuations in water depth, which may account for the lack of reducing conditions because they are actively pumped down. 2.  Plants Aquatic Carex spp.  (C. lenticularis and C. utriculata) were found at the majority of wetland areas which make them a prime candidate for use in treatment wetland systems (Figure 2). These species can offer a 113  range of functions, such as creating oxidizing or reducing conditions in a wetland system depending upon the design (soils and hydrology) used. Their roots have low radial oxygen loss and can therefore promote reducing zones even in shallow water depths (Haakensen et al., 2015).                    Typha latifolia was found at the SC8-pump site and Pond 9A.  This plant species was of interest because they can typically grow in deeper water than Carex, and can be encouraged to promote either aerobic or anaerobic conditions in their root zones based on differences in CWTS designs and soils.  Aquatic mosses were noted at a variety of sites (Contango 2015a), and are of particular importance, as they are known metal accumulating organisms through sorption and filtration (Aldrich & Feng, 2000; Gstoettner & Fisher, 1997).  Due to their ability to accumulate metals and low decomposition rate, mosses are especially useful in remediation efforts as they can help prevent toxic accumulation of metals in wetlands.  Additional benefits include their abilities to host a range of beneficial microbes (Contango 2015a) and to grow in a range of pH environments, making them an ideal candidate for enhancing treatment of the Huckleberry Mine EZP water. 3.  Microbes When sulphur compounds are reduced by microbes to create sulphides, insoluble metal-sulphide complexes can form, which removes metals and metalloids from the water. Additionally, alkalinity can be created by this process, which is an important aspect of ARD water treatment.  Treatment of selenium is also microbially mediated, where selenate and selenite are reduced to form insoluble elemental selenium.     Abundance of sulphide-producing bacteria at the site are summarized in Figure 3, which shows that some of the highest abundances were associated with C. lenticularis and moss from Pond 9A.  Carex lenticularis is therefore a prime candidate for CWTS based on the desirable traits of forming dense monocultures, and hosting many beneficial microbes.  This location had elevated sulphur concentrations in the soil and in situ measurements indicating reducing conditions with a low DO, ORP, and negative relative soil redox (Table 2).  Selenate-reducing bacteria were found in all samples except the EZP edge Figure 2 Vegetation in Pond 9A.  Left, Picture of aquatic moss colonized around C. lenticularis throughout Pond 9A.  Right, picture of C. lenticularis roots with black l hid  t i i  114  location, while molybdenum-reducing bacteria were associated with all sample locations.  Iron-reducing bacteria can decrease net acidity and raise pH, and were found in all samples with higher abundances typically associated with plant roots and mosses.   CONCEPTUAL TREATMENT DESIGNS AND CONSIDERATIONS  With complex water chemistries such as mining-influenced water, detailed characterization is critical to ascertain overall treatability. Certain components could interfere with CWTS function, while others (e.g., ammonia, iron, sulphate, total organic carbon) may either beneficially or detrimentally affect the treatability of other constituents. It is therefore important to evaluate the treatability of water as a whole, and to not focus solely on the elements requiring treatment.  Models for long-term water quality predictions were produced by SRK Consulting, and included two scenarios; one with a cover to mitigate ARD on the EZP slide, and one without a cover (SRK Consulting, 2015; Appendix G). Stoichiometric calculations based on biogeochemical processes (such as sulphate reduction coupled to sulphide production and alkalinity generation) suggest that the current water quality, and that predicted by models assuming a cover at the EZP, should both be readily treatable by an anaerobic CWTS. However, the predicted water chemistries for a worst-case scenario with no cover estimates up to 640 mg/L of acidity and would require integration of a hybrid treatment system (Table 3).  A hybrid system may include one or more CWTS designs, along with other passive or semi-passive Figure 3 Abundance of sulphide-producing bacteria in samples from Huckleberry Mine.  Number of organisms is provided per gram of sample, as determined by MPN for total heterotrophic organisms, adjusted by the genetically determined percentage of the community that is key sulphide-producing bacteria. In the context of this figure, sulphide-producing organisms are those that can reduce sulphate, sulphite, thiosulphate, or elemental sulphur, to form sulphide. ‘Other’ is EZP-edge soil (with no plants present) or biofilm on underwater C. lenticularis leaves. Organisms are either classified to the genus (g) or family level (f).  115  treatment mechanisms (e.g., bioswales, bioreactors, settling ponds), or active treatment (e.g., lime). These options are evaluated in the following sections.   Based on the comprehensive water chemistry analysis, the key considerations driving treatment requirements at the Huckleberry Mine EZP location are elevated net acidity, associated low pH, and elevated concentrations of aluminum, copper, and sulphate. Additionally, several other metals and metalloids are expected to require treatment. The order in which the constituents and problematic parameters are treated in the EZP water will significantly impact the overall treatability and cost of treatment. Attention must be given to ensuring the correct order of processes is undertaken for water treatment in this case.  Elevated aluminum concentrations are a key aspect of the EZP water chemistry.  Aluminum can be removed from water through oxidative processes, forming insoluble aluminum hydroxide compounds. This oxidation processes consumes alkalinity by using hydroxide ions, and occurs above a pH of 5.5. For this reason, the amount of alkalinity required to neutralize the EZP water in a biological system such as a CWTS will not proceed in a linear function (Figure 4).  Figure 4 conceptually shows the buffering effect produced by the dissolved aluminum, thereby increasing the total amount of alkalinity required to raise the pH of water.  Once the dissolved aluminum has been removed, the water should neutralize with little additional alkalinity input.  Therefore, removal of dissolved aluminum through mechanisms such as sorption should decrease the total alkalinity required to neutralize the water. This may be achieved by mosses even at low pH, however, uptake and sorption are typically more effective if the pH is above 4.5 (Engleman and McDiffett, 1996; Yoshimura et al., 1997; Contango, 2015b). The in situ pH measured at the EZP-edge during the site assessment was 4.41 (Table 2). As such, the ideal conceptual scenario for water treatment at the EZP includes alkalinity generation to bring the pH above 4.5, followed by aluminum removal through mosses, and further alkalinity generation and metals removal through anaerobic CWTSs. Acidity Alkalinity Aluminum Copper Iron Sulfate Scenario 1 1: No Cover, Oxidation is NOT limited by Diffusion (closure, predicted) 640 0 65 16 12 1300 Scenario 2 1: 100% Effective Cover (closure, predicted) 29 5 2.6 0.65 0.49 130 EZP runoff (EZP-edge 2) from this feasibility assessment (actual, September 2015) 155 <1 18.4 1.19 0.84 1570 1 Scenario 1 and 2 are estimated annual average concentrations. All values in mg/L. Aluminum, Copper, and Iron are dissolved concentrations. Data provided by SRK Consulting (September 2015; Appendix G) 2 Surface oxidation observed presently at the EZP edge and is pre-existing prior to the 2007 slide (natural); and provides an opportunity for assessing treatability processes prior to any predicted acid onset. Table 3  Current and predicted EZP water quality for constituents affecting treatment 116  Other metals and metalloids may be stored short-term in a CWTS through sorption to moss and organics, but there needs to either be an annual net production of sulphides sufficient to mineralize them in more stable forms, or microbial dissimilatory reduction (e.g., selenium and uranium). In general terms, sulphide (reduced form of sulphate) is necessary for metals treatment, but in turn, metals (cations) are required to remove sulphide from solution. Furthermore, an addition of organic carbon may be required to produce sufficient sulphate reduction, achieve neutralization, and precipitation of relevant metals as sulphides. In this context, the EZP water contains sufficient sulphate that if reduced, metals and metalloids could be removed from the water as sulphides. However, it is unlikely that the total concentration of sulphate would be significantly decreased as a result of this metals removal action.  Treatment Train Owing to its water chemistry and especially the elevated aluminum concentrations, a three-step treatment train is recommended for water quality improvement at the EZP. This may include passive, semi-passive, or active methods, or a combination thereof. The purpose and example processes to achieve each of these steps are outlined in Table 4.  Although total acidity of the water was tested, because the standard acidity test brings the pH to 8.3, there is an uncertainty regarding the amount of alkalinity that will be required to reach a pH of 4.5 to remove aluminum through sorption, and then above 5.5 in order to remove aluminum through sorption/uptake and as hydroxides (Figure 4). This can be tested in a laboratory, through a specialized titration assay, both with and without interaction with aquatic mosses to assess the impact of putative sorption removal processes on alkalinity demands. Depending on the amount of alkalinity required, it may be necessary to use a semi-passive method (e.g., bioreactor), or active treatment (e.g., lime) to raise the pH to 5.5. Once the pH of the water is above this level (regardless of the process used to produce the alkalinity), the water is expected to be treatable by the CWTS. However, even if active treatment is chosen as a sole means to treat the water, a CWTS may be needed to remove constituents such as selenium and nitrate that are not treated by the liming process.    Figure 4 Conceptual effect of dissolved aluminum and acidity on alkalinity needed for neutralization of low pH water at the Huckleberry Mine 117  Table 4 Conceptual processes for sequential treatment steps for EZP water quality improvement The low pH and high aluminum concentrations in the EZP water add an additional challenge for CWTS operation. Aluminum can be acutely toxic to plant roots when present in elevated concentrations in net acidic soils. Therefore, the soils of the CWTS will require a buildup of neutralization capacity prior to receiving the EZP water in order to operate successfully. This can be achieved by allowing the CWTS to acclimate, mature, and become alkalinity producing (sulphate reducing) prior to introduction of acidic waters (thus serving to protect the plants). This alkalinity production through sulphate reduction is reliant upon availability of organic carbon as an electron source. Over time, and as the CWTS matures, the organic carbon will be produced by the vegetation. However, to initiate this process and decrease the length of time for maturation of the CWTS, organic materials can be incorporated into the initial planting substrates. A conceptual semi-passive water treatment configuration using the 3-step approach outlined in Table 4 is shown in Figure 5, which displays the aerial view of Huckleberry Mine with the treatment design overlaid on the map.  The first step would generate alkalinity and raise pH, starting with an in pit treatment such as an algal bloom or sulphate reduction by addition of organic material.  This water could then be pumped from the pit into an aerobic CWTS created on the EZP tailings to remove aluminum from the system (and decrease total alkalinity demand required for neutralization).  Finally, gravity flow could transfer the waters to a sulphate-reducing CWTS for final neutralization and additional metals removal through sulphide co-precipitation.  Depending on the phasing and commissioning timelines, the function of the sulphate-reducing CWTS could instead be performed by an active water treatment facility.Steps Action and Purpose Example Processes Active Passive or Semi-passive  1) Raise pH to 4.5 Increase pH to above 4.5, enabling aluminum removal through biological sorption Lime • Sulphate-reducing CWTS • In-pit (algal bloom) • Alkalinity containing bioswale • Bioreactor 2) Remove aluminum Remove aluminum, decreasing total alkalinity demand of water Not applicable • Sorption to mosses in CWTS • In-pit (algal bloom) 3) Raise pH to neutral Reduce sulphate, creating alkalinity and producing sulphides (or directly increase pH) Lime • Sulphate-reducing CWTS • Bioreactor 118  Figure 5 Aerial view of Huckleberry Mine site (2014) with conceptual passive/semi-passive water treatment configuration.  This photo is focused on the eastern-most section of the mine site where the East Zone Pit (EZP) is located. 119    PRELIMINARY RECOMMENDATIONS FOR FUTURE WETLAND DEVELOPMENT   When a design has been established for a passive water treatment system such as a CWTS, it needs to be tested and optimized to account for site-specific aspects. A phased series of bench- and pilot-scale tests are recommended to confirm specific treatment mechanisms and address knowledge gaps. Conducting these tests and optimizations at a smaller scale allows for design corrections and adjustments, uncovering unforeseen complications, and may lead to remedies which can be addressed quickly and cost effectively.   Bench-scale testing Bench-scale testing typically involves small-scale experiments that can take place on a laboratory bench/counter in beakers, buckets, or jars. They can be used to test the behavior of water chemistry parameters, contaminant interactions, and reactions with different substrates, wetland plants, potential amendments, and specific treatment mechanisms. The performance of each step in the treatment train (Table 4) affects the subsequent steps, and it may be necessary for a few iterations of testing to be undertaken.  For this reason, recommendations were made for using a bench-scale treatment program to determine the most cost-effective treatment model. The program recommended will determine: 1) the amount of alkalinity needed to raise pH to (and between) specific points, 2) the amount of aluminum removed by aquatic mosses or algae, and 3) amount of alkalinity needed to raise the pH to circumneutral, after exposure to aquatic mosses, algae, or both.  Pilot-scale testing Pilot-scale systems are typically built using large tubs or tanks to represent individual wetland treatment cells.  This type of system enables removal rate coefficients to be developed across a range of concentrations and subsequently, can be used for appropriate sizing of the full-scale system. A simulated version of the water requiring treatment is used in the pilot-scale study, which provides the opportunity to test a range of water chemistries that mimic different scenarios (e.g., worst-case, predicted long-term water quality, etc). Flow rate fluctuations can also be imposed and system upsets triggered purposefully (e.g., drought or flooding) to test the effects on treatment.  For the Huckleberry Mine site, in addition to developing rate coefficients for effective sizing of full-scale systems, other design aspects for the CWTS need to be tested at pilot scale, such as optimal plant selection, and organic amendments for the substrates. Plant-specific attributes are also evaluated, such as suitability for transplanting, effects on water flow (i.e., short circuiting of water), uptake of constituents of potential concern, natural plant density, effects of plant species on soil redox, tolerance to variations in water depth, and biomass production (organic carbon production for following year). A period of three or more months is often necessary for pilot-scale testing.  This allows plant acclimation, and observation of actual treatment within a system beyond that which is attributable to sorption. The loading of constituents of concern into the sediment is also determined at the end of pilot-scale testing.  Owing to their passive to semi-passive operation, CWTS are a preferred option for each of the three Steps in the treatment train (Table 4). Testing is needed to assess the suitability of CWTS not only for each step, but in the context of the chosen technology for any precedent steps. For efficiency in this design 120  evaluation, bench-scale testing should be undertaken before proceeding to pilot-scale testing. During bench-scale testing, the pilot-scale systems can be constructed with plants harvested from Huckleberry Mine and allowed to mature. The exact water chemistry used (i.e., Stage 1, 2, 3 of the treatment train, or combination thereof) will be refined through the bench-scale testing and discussions with Huckleberry Mine.    CONCLUSION  Analysis of Huckleberry Mine EZP waters and associated sites have been successfully analyzed for soil, plants, microbes, and water.  Native plants and beneficial microbial communities were identified at multiple locations at the Huckleberry Mine site for use in a CWTS. Several wetland species are available for considerations for CWTS use, with C. lenticularis being a prime candidate, as it naturally forms dense monocultures, and is host to many beneficial microbes, both desirable traits for CWTS.  Comprehensive water chemistry assessment led to the development of a conceptual three-step treatment design which can achieve closure water treatment for the EZP and may include passive, semi-passive, or active methods, or a combination thereof. Bench- and pilot-scale testing will be necessary to further refine CWTS designs and treatment steps, and to provide recommendations on sizing and outflow predictions. 4.  ACKNOWLEDGEMENTS   Contango would like to acknowledge the assistance of Ainsley Stewart with microbiological laboratory testing and analyses.  REFERENCES  Aldrich C, Feng D. 2000. Removal of heavy metals from wastewater effluents by biosorptive flotation. Minerals Engineering 13:1129-1138.  Contango Strategies Limited (Contango). 2015a.  Huckleberry Mine CWTS Site Assessment Report. Document # 022_1215_01A  Contango Strategies Limited (Contango). 2015b. Confidential Report. Document #008_0115_01B.  Engleman CJ Jr and McDiffett WF. (1996) Accumulation of aluminum and iron by bryophytes in streams affected by acid-mine drainage. Environ. Pollut. 94:67-74.  Faulkner SP, Patrick Jr. WH, Gambrell RP. 1989. Field techniques for measuring wetland soil parameters. Soil Sci. Soc. Am. J. 53:883-890.  Gstoettner EM, Fisher NS. 1997. Accumulation of cadmium, chromium, and zinc by the moss Sphagnum papillosum Lindle. Water Air Soil Pollut. 93:321-330.  121  Haakensen M, Pittet V, Spencer J, Rodgers JH Jr, Castle JW. 2015. Process-driven design and piloting of a site-specific constructed wetland for Copper and Selenium treatment in the Yukon. Mine Closure 2015, Vancouver, Canada.  Huddleston GM, Rodgers JH Jr. 2008. Design of a constructed wetland system for treatment of copper-contaminated wastewater. Environ. Geosci. 15:9-19.  SRK Consulting. September 14, 2015. Source: Kathleen Willman.  Yoshimura E, Satoh N, Kaneko M, Nishizawa N, Satake K, Mori S. 1997. Cellular distribution and chemical forms of aluminum in Scapania undulata in Plant Nutrition for Sustainable Food Production and Environment, 78: 457-458.   

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