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Dynamics of temporal and spatial mercury contamination in an urban watershed Muraro, Matthew Robert 2005

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DYNAMICS OF TEMPORAL AND SPATIAL MERCURY CONTAMINATION IN AN URBAN WATERSHED by MATTHEW ROBERT MURARO B.A., University of North Carolina at Wilmington, 1996 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES Resource Management and Environmental Studies THE UNIVERSITY OF BRITISH COLUMBIA March 2005 © Matthew Robert Muraro, 2005 Abstract Mercury is a concern in aquatic environments because it can lead to accumulations of methylmercury in fish, which is the primary source of mercury exposure to humans. The Brunette Watershed is a highly urbanized watershed in metropolitan Vancouver with a rich record of monitoring (1973-2003) trace metal distribution and dynamics. This study was conducted to investigate the 294% increase in Brunette Watershed stream sediment mercury concentrations from 1973-1996. The project conducted analysis of field samples, laboratory experiments and examined previous data to determine if methylcyclopentadienyl manganese tricarbonyl (MMT) may play a role in the increase of mercury in the watershed. Little evidence compiled in this study supported the hypothesis that manganese, iron, sulfur or DOC is associated with mercury throughout the watershed. Thus, it is difficult to conclude or rule out that MMT or manganese oxides play a major role in the transport of total mercury. Laboratory experiments creating summer anoxic conditions released a significant amount of mercury from lake sediment into overlying waters. It seems that this release of mercury may be controlled by sulfate reducing bacteria. The study also found an analysis method used in the study caused 66.8% mean loss of mercury in stream sediment samples when the samples were dried. Temporal and spatial analysis of sediment data revealed that mercury concentrations have started to decrease since 1993. When sediment concentrations were adjusted for the 66.8% loss in stream sediment, 1993 mercury concentrations exceeded the Federal Interm Sediment Quality Guidelines at 12 locations; but in 2003, only 1 site exceeded the same guideline. The decrease in mercury concentrations may be linked to the increased public awareness and a large reduction of emissions from a nearby refuse incinerator. Effective imperviousness and mercury levels in stream sediment are significantly correlated throughout the period of high mercury releases from the incinerator. This may indicate that atmospheric mercury deposited on impervious surfaces connected to waterways may contribute to increases in stream sediment concentrations. ii TABLE OF CONTENTS Abstract ii Table of Contents iiList of Tables vList of Figures ; x Acknowledgments xii 1. INTRODUCTION 1 1.1 STUDY GOAL 2 1.2 OBJECTIVES 5 1.3 MERCURY SOURCES AND ENVIRONMENTAL CONTAMINATION 5 1.4 ATMOSPHERIC PROCESSES AND TRANSPORT 9 1.5 AQUATIC PROCESSES AND TRANSPORT 10 1.6 GEOCHEMICAL PROCESSES OF MERCURY IN AQUATIC SEDIMENT 12 1.7 MERCURY AND METHYLMERCURY IN AQUATIC SYSTEMS 13 2. CHARACTERISTICS OF THE BRUNETTE WATERSHED 16 2.1 SITE DESCRIPTION 12.2 HISTORIC CONTAMINATION IN THE BRUNETTE WATERSHED 22 2.2.1 Trace Metal Contaminants 22 2.2.2 Organic contaminants 23 2.2.3 Microbial Contaminants 24 3. METHODS 25 3.1 STREAMBED SEDIMENT SAMPLING AND ANALYSIS 23.1.1 Streambed sediment locations 27 3.1.2 Sediment sample collection3.1.3 Sediment sample preparation and analysis 28 3.2 LAKE SEDIMENT MICROCOSM EXPERIMENT 28 3.2.1 Microcosm sample collection 28 3.2.2 Microcosm Laboratory Experiment3.2.3 Microcosm sampling 33 iii 3.2.4 Microcosm analysis methods 33 3.3 LABORATORY ANALYSIS 33 3.3.1 Aqua-Regia digest 33 3.3.2 Trace Metals3.3.3 Mercury in Waters 34 3.3.4 Mercury in sediments3.3.5 Percent Total Carbon in sediment 35 3.3.6 Total Sediment Solids 35 3.3.7 Water Quality Measurements ...35 3.4 STATISTICAL ANALYSIS 35 4. RESULTS AND DISCUSSION 38 4.1 DATA QUALITY4.1.1 Variability between sample and methods: Determining the effects of drying samples 40 4.2 MICROCOSM EXPERIMENTS 41 4.3 SUSPENDED SEDIMENTS IN STILL CREEK AND THE BRUNETTE RIVER 48 4.4 BURNABY LAKE SEDIMENT 53 4.5 STREAM SEDIMENT...., -. 56 4.6 COMPARISON OF MERCURY IN STREAM SEDIMENT AND CATCHMENTS IMPERVIOUSNESS 63 4.7 COMPARISON OF VARIOUS ANALYSIS 69 4.8 POSSIBLE SOURCES 73 5. SUMMARY AND CONCLUSIONS 78 5.1 MERCURY'S CORRELATIONS WITH ORGANIC CARBON, IRON OXYHYDROXIDES, MANGANESE OXYHYDROXIDES, SULFUR AND OTHER TRACE METALS IN STREAM SEDIMENT, LAKE SEDIMENT, STORMWATER AND LABORATORY CONTROLLED REDOX CONDITIONS 79 5.2 LEVELS OF MERCURY, IRON, MANGANESE AND ORGANIC CARBON RELEASED FROM LAKE SEDIMENT TO OVERLYING WATER DUE TO SEDIMENT ANOXIA 79 5.3 TEMPORAL AND SPATIAL CHANGES IN MERCURY AND TRACE METAL CONTAMINATION SINCE 1973 78 iv 5.4 MMT'S RESPONSIBILITY FOR THE INCREASE OF MERCURY CONCENTRATIONS IN THE BRUNETTE WATERSHED STREAM SEDIMENT 80 6. RECOMMENDATIONS 81 6.1 IMPLICATIONS FOR FURTHER RESEARCH 86.2 MANAGEMENT IMPLICATIONS 82 7. LITERATURE CITED 3 APPENDIX A Stream Sediment Sampling Locations 90 APPENDIX B Concentration of trace metals in Brunette Watershed stream sediment from 1973-2003 92 APPENDIX C Metal concentrations in sediment cores from Burnaby Lake 96 APPENDIX D Total metal concentrations within a Brunette Watershed stormwater event 97 APPENDIX E Microcosm data from Experiment 1, November 17 to December 9, 2002 ...98 APPENDIX F Correlations for 1973-2003 stream sediment in the Brunette Watershed ...100 APPENDIX G Correlations for Burnaby Lake composite core sediments 104 APPENDIX H Correlations for Microcosm #1 data 105 APPENDIX I Correlations for the February 28, 1997 stormwater event in the Brunette Watershed 106 APPENDIX J Quality control data for mercury in sediment 108 APPENDIX K Wilcoxon Paired Sample Signed Rank Test for mercury stream sediment data in the Brunette Watershed 109 APPENDIX L Mercury concentrations in stream sediment adjusted for a 66.8% loss caused by drying the sediment .111 LIST OF TABLES Table 1.1 Estimate of annual releases of mercury from purposeful uses in Milwaukee, Wisconsin. The area is 420 square miles with population just over 2 million 7 Table 1.2 Estimate of annual releases of mercury from processes that release trace impurities in Milwaukee, Wisconsin. The area is 420 square miles with population just over 2 million 8 Table 2.1 Catchment name, number and imperviousness from Figure 2.1 18 Table 2.2 Average slope of catchments within the watershed 18 Table 2.3 Land use in the Brunette Watershed in proportion to the total area in 1973 and 1993 19 Table 2.4 Land cover in the Brunette Watershed in 1973 and 1993. 20 Table 3.1 Locations excluded due to urban development 27 Table 3.2 The following parameters were analyzed in the UBC Civil Engineering Laboratory 35 Figure 3.5 Box-whisker diagram. Adapted from 37 Table 4.1 Comparison of methods used in stream and lake sediment analysis in 1973, 1989, 1993 and 2003 8 Table 4.2 Quality control data for sediment metals analysis. Results in ug/kg, dry weight. 39 Table 4.3 Percent increase of mercury and iron in four microcosms over four weeks in experiment 1 .Manganese concentrations were all below the 50 wg/L detection limit. ..45 Table 4.4 Total metal concentrations in suspended solids collected with a continuous flow centrifuge during a February stormwater event on the Brunette River system, concentrations in mg/kg, dry weight 49 Table 4.5 Comparison of mercury concentrations in sediment from various locations. The Environment Canada guideline ISQC is 174 wg/kg. All concentrations in dry weight. 55 Table 4.6 Various federal guidelines, regulations and objectives for mercury for different water uses 58 Table 4.7 Adjusted mercury concentrations in stream sediment for a loss caused by drying that exceeded federal guidelines within the Brunette Watershed from 1973-2003 (Appendix L) [Concentrations in wg/kg, dry weight] 59 vi Table 4.8 Ratio of mercury concentrations in the Still Creek sub-basin and the Brunette River sub-basin in sediments and stormwater over a thirty-year period 61 Table 4.9 Comparison of sampling locations, matrix and methods for mercury determination in the Brunette Watershed 70 Table 4.10 Mercury median or mean concentration in various media throughout the watershed. (Water concentrations in wg/L and soil in wg/kg) 71 Table A-l Stream sediment sampling locations 90 Table B-l Streambed sediment, <180um fraction in the Brunette Watershed, total concentration in 1973. Values in dry weight. Nitric acid digest for all metals except Hg. Mercury analyzed with potassium permanganate digestion and cold vapor analysis 92 Table B-2 Streambed sediment, <180um fraction in the Brunette Watershed, total concentration in 1989. Values in dry weight. Nitric acid digest for all metals except Hg. Mercury analyzed with potassium permanganate digestion and cold vapor analysis 93 Table B-3 Streambed sediment, <1 SOum fraction in the Brunette Watershed, total concentration in 1993. Values in dry weight. Nitric acid digest for all metals except Hg. Mercury analyzed with potassium permanganate digestion and cold vapor analysis 94 Table B-4 Streambed sediment, <180wm fraction, in the Brunette Watershed, total concentration in 2003. Values in dry weight. Nitric acid digest for all metals except Hg. Mercury analyzed with pyrolysis digestion and AA detection 95 Table C-l Metal concentrations in sediment cores (depth < 2.0 cm) from Burnaby Lake [mg/kg dry weight]. Refer to Figure C-l for site locations. (C) indicates composite sample was analyzed 96 Table D-l Total metals within a stormwater event on the Brunette River, February 28, 1997 97 Table D-2 Total metals within a stormwater event on Still Creek, February 28, 1997 97 Table E-l Microcosm pH data from Experiment 1, November 17 to December 9, 2002. Note: Microcosm variables (1. Control, 2. DI water, 3. Oxic and 4. Molybdate ions).. 98 Table E-2 Microcosm conductivity data (uS/cm) data from Experiment 1, November 17 to December 9, 2002. Note: Microcosm variables (1. Control, 2. DI water, 3. Oxic and 4. Molybdate ions) 19vii Table E-3 Microcosm dissolved oxygen data (mg/L) data from Experiment 1, November 17 to December 9, 2002. Note: Microcosm variables (1. Control, 2. DI water, 3. Oxic and 4. Molybdate ions).. ; 98 Table E-4 Microcosm dissolved organic carbon data (mg/L) data from Experiment 1, November 17 to December 9, 2002. Note: Microcosm variables (1. Control, 2. DI water, 3. Oxic and 4. Molybdate ions) J 99 Table E-5 Microcosm mercury data (wg/L) data from Experiment 1, November 17 to December 9, 2002. Note: Microcosm variables (1. Control, 2. DI water, 3. Oxic and 4. Molybdate ions)Table E-6 Microcosm Iron data (ppm) data from Experiment 1, November 17 to December 9, 2002. Note: Microcosm variables (1. Control, 2. DI water, 3. Oxic and 4. Molybdate ions) 99 Table E-7 Mercury concentrations of Burnaby lake sediment used in Microcosm #1 analysis, November 1, 2002 9Table F-l Spearman's rho Correlations with Bonferroni Correction- 1973 Stream Sediment in the Brunette Watershed 100 Table F-2 Spearman's rho Correlations with Bonferroni Correction- 1989 stream sediment data in the Brunette Watershed 101 Table F-3 Spearman's rho Correlations with Bonferroni Correction- 1993 stream sediment in the Brunette Watershed 102 Table F-4 Spearman's rho Correlations with Bonferroni Correction- 2003 Stream Sediment in the Brunette Watershed 103 Table G-l Spearman's rho Correlations with Bonferroni Correction- Burnaby Lake composite core sediments 104 Table H-l Spearman's rho Correlations with Bonferroni Correction for Microcosm #1 data 105 Table 1-1 Spearman's rho Correlations with Bonferroni Correction for the February 28, 1997 on Still Creek stormwater event 106 Table 1-2 Spearman's rho Correlations with Bonferroni Correction for the February 28, 1997 on the Brunette River stormwater event 10Table J-l Quality control data for mercury in sediment, analyzed on a Lumex AA. Results in ug/kg, dry weight. Environmental Resource Associates: Reference Sample Catalog #540 Lot # D035-540 108 viii Table K-l Wilcoxon Paired Sample Signed Rank Test for 1973,1989, 1996 and 2003 mercury stream sediment data in the Brunette Watershed ....109 Table K-2 Test Statistics for data from 1973-2003 110 Table L-l Mercury concentrations in stream sediment adjusted for a 66.8% loss caused by drying the sediment (ug/kg, dry weight) Ill ix LIST OF FIGURES Figure 1.1 Location of the Brunette Watershed in Lower British Columbia 2 Figure 1.2 Map of Brunette Watershed (McCallum 1995) 3 Figure 1.3 Conceptual model of mercury cycling and pathways for a typical freshwater lake (Krabbenhofte/a/. 1997) ; 14 Figure 2.1 Map of the Brunette Watershed and tributaries and catchments (GVRD 2000a). 17 Figure 2.2 Cross section view of Brunette Watershed indicating slope (McCallum 1995). ..21 Figure 3.1 Brunette Basin stream sediment sampling sites. Adapted from Hall et al. (1976) 26 Figure 3.2 Diagram of a single microcosm with traps 29 Figure 3.3 Experiment I, four different microcosms were set-up for the initial three-week trial run 31 Figure 3.4 Experiment II, six microcosms were set-up with the same parameters as the first run for the six week analysis. Each contained 100 g of sediment and 1.2 L lake water. The following variables were in each microcosm: 32 Figure 4.1 Box-whisker plots comparing mercury concentrations in 2 mm wet vs dried stream sediment at 105°C (n=27) 41 Figure 4.2 Microcosm 1 containing lake sediment, lake water under anoxic conditions, for Experiment 1 42 Figure 4.3 Microcosm 2 containing lake sediment, de-ionized water and under anoxic conditions, for Experiment 1 : 42 Figure 4.4 Microcosm 3 containing lake sediment, lake water under oxic conditions, for Experiment 1 43 Figure 4.5 Microcosm 4 containing lake sediment, lake water with molybdate ions added under anoxic conditions, for Experiment 1 43 Figure 4.6 Diagram of Eh-pH for mercury in aquatic systems. Adapted from (Veiga and Meech 1998) 7 Figure 4.7 A Box-whisker plot of total mercury concentrations in stormwater over a stormwater event, units in ng/L [Data from Sekela et al (1998)] 49 Figure 4.8 Mercury concentrations in stormwater grab samples collected by Environment Canada in Still Creek on February 28, 1997 (Sekela et al. 1998). Bars indicate mercury concentrations and squares indicate flow 52 Figure 4.9 Mercury concentrations in stormwater grab samples collected by Environment Canada in the Brunette River on February 28, 1997 (Sekela et al. 1998) Bars indicate mercury concentrations and squares indicate flow 52 Figure 4.10 Box-whisker plot of mercury concentrations in Burnaby Lake core samples, concentrations in mg/kg dry weight [n=18] (Enkon 2002) [Environment Canada's ISQG guideline is 0.174 mg/kg] 54 Figure 4.11 Box-whisker plot of mercury concentrations (wg/kg dry weight) in Brunette Watershed stream sediment from 1973-2003. One outlier excluded from 1993 at 870 wg/kg 57 Figure 4.12 Box-whisker plot of mercury concentrations in the Still Creek sub-basin stream sediment from 1973 to 2003 60 Figure 4.13 Box-whisker plot of mercury concentrations in the Brunette River sub-basin stream sediment from 1973 to 2003 1 Figure 4.14 Spearman's correlation coefficients for mercury in 180 «m stream sediment from 1973-2003. Data located in Appendix F 62 Figure 4.15 Box-whisker plot of mercury streambed sediment concentrations (ug/kg) from six catchments in 1993. One outlier was excluded from Still Creek with a value of 2115 wg/kg. In 1993, three independent samples were analyzed at each site 65 Figure 4.16 Scatter-plot of 1973 stream sediment mercury concentrations (wg/kg) vs effective impervious area (hectares) from 1973. Line indicates the linear regression of the six area's 66 Figure 4.17 Scatter-plot of 1993 stream sediment mercury concentrations (wg/kg) vs effective impervious area (hectares) Line indicates the linear regression of the six area's 67 Figure 4.18 Scatter-plot of 2003 stream sediment mercury concentrations (wg/kg) vs total impervious area (hectares) from 1996. Effective impervious area data was unavailable for the period of 1994-2003. Line indicates the linear regression of the six area's 69 Figure 4.19 Metal median concentrations in <180 wm stream sediment from 1973-2003. Mercury in wg/kg. Iron in mg/kg. Manganese in wg/kg xO.l 76 Figure 4.20 Metal median concentrations in <180 wm stream sediment from 1973-2003. (All metals in wg/kg) 77 Figure C-l Location of Burnaby Lake sediment core sampling stations. Photo adapted from (Enkon 2002) 96 xi Acknowledgments This project was made possible by the labor, direction and funding of Dr. Ken Hall. His experience and knowledge of the Brunette Watershed over the last thirty years was invaluable. This project would not have been possible without the various laboratory support and guidance. Dr. Marcello Vegia provided equipment and technical assistance with the mercury analysis. Dr. Leah Bendell-Young provided more needed direction and statistical advice. I would also like to thank Paula for her advice on the microcosm setup from the Environmental Engineering and Susan Harper for the metals analysis. Carol and Karen, from the Soils Laboratory, also provided metals analysis. UBC-CERM3 provided funding for the mercury laboratory instrumentation and related supplies. xu 1. INTRODUCTION Mercury is intriguing to study because its toxicology, transformation and transport mechanisms are complex and not currently well understood. The U.S. Environmental Protection Agency is allocating 40-50% of its mercury budget over the next 5 years to be spent on transport, fate, and transformation, because it considers it a high priority for research (EPA 2003). Mercury is the most common contaminant in aquatic ecosystems worldwide, however, its sources and pathways and toxicity controlling processes are very complex (Krabbenhoft 1997). It's behavior in the environment is considerably different than other metals. Physically, it is unique because it is a liquid at room temperature and pressure. It and some of its compounds, have a high vapor pressure compared with other metals. Various complex processes affect mercury in atmospheric and aquatic systems that are not fully understood. Generally, it is very reactive in the environment and readily undergoes phase and reduction-oxidation (redox) changes. It will undergo many environmental processes, photochemical reactions, chemical oxidation and redox reactions, microbial transformations, and physiological fractionation. Mercury pollution is a complex problem in the world today and an incident in the 1950's mercury poisoning drew worldwide attention when approximately 200 people died in the Japanese Fishing village of Minamata. Later in the 1980's, researchers found elevated levels of mercury in remote, isolated lakes where no sources could immediately be identified. This lead to the discovery that mercury contamination of aquatic systems is generally caused by atmospheric transport and deposition. Once in an aquatic system it bioaccumulates in organisms to levels much higher then the surrounding atmosphere, water or lake sediment. In the past, analytical instrument technology was not able to reach a low enough mercury detection limit to study it effectively. Fish in the remote lakes would have levels of detectable mercury but a source could not be detected in water or air. Over the last fifteen years, improvements in analytical techniques and technology have increased the capability of researchers. Recently, advances in technology have made it possible to study levels as low as 0.005 ng/m3 of mercury, which is low enough for ambient atmospheric testing (Meyers 1998). 1 Mercury is a concern in aquatic environments because it can lead to accumulations of methylmercury in fish. Seafood consumption is the only significant bio-accumulation pathway for humans and animals to become contaminated (EPA 2003; UNEP 2003). Interestingly, due to the complex processes that control mercury cycling, total mercury concentrations in air, water or soil can not be an indicator of methylmercury concentrations in water, sediment or biota. Thus, it is necessary to understand the cycling of mercury in aquatic systems. 1.1 Study goal The Brunette Watershed, a highly urbanized watershed in metropolitan Vancouver, British Columbia which has been intensely studied over the last thirty years (Figure 1.1 and 1.2). A wealth of information regarding the watershed has been created in this time span and knowledge of watershed conditions and its processes has increased with each study. McCallum (1996) noted a 294% increase in mercury and a 131% increase in manganese Figure 1.1 Location of the Brunette Watershed in Lower British Columbia 2 concentrations in stream sediment from 1973-1996 throughout the watershed. It was presumed by McCallum (1995) the increase in manganese concentrations was due to the addition of methylcyclopentadienyl manganese tricarbonyl (MMT) in gasoline after 1986, as a replacement for lead additives. This concept was reinforced by a 2600% increase in dilute acid extractable manganese from stream sediment, which is thought to be representative of the manganese oxide fraction (Bendell-Young and Harvey 1991). One possible explanation used by McCallum (1995) for the increase in mercury concentrations was its adsorption by manganese oxides (Thabalasingam and Pickering 1985). Manganese, released from the exhaust of an automobile will oxidize and then absorb or bind with various materials, including mercury. Mercury and manganese could then be flushed into aquatic systems by stormwater events. 2Mn+2+02 = (Mn02)"2 (Mn02)-2 + Hg +2= Hg (MnO) 2 The geochemical processes for controlling mercury's associations in an aquatic environment are different than other metals, due to its unique physical and chemical properties. Mercury forms strong bonds with complexing agents or ligands. Ligands are molecules or ions that surround a metal ion in a complex. This project is intended to investigate the possibility that manganese oxides could be leaching mercury out of the soil and transporting it through the watershed; with the hope of expanding the current knowledge of mercury dynamics in the Brunette Watershed. It is suspected that these complexes transport mercury in the "flashy" Still Creek system as particulate matter. Particulates eventually reach Burnaby Lake and settle out. In the summer, Burnaby Lake becomes anoxic. Reducing conditions may release mercury and methylmercury bound to iron and manganese oxides back into interstitial porewater and the overlying water column. This project was intended to determine if metals, including mercury, bound to these iron oxides (FeOx) and manganese oxides (MnOx) are released under anoxic conditions in sediment, interstitial water and overlying water. On a larger scale, it will investigate various processes to improve the understanding of mercury transport in the Brunette Watershed. 4 1.2 Objectives 1. Quantify current levels of mercury and other trace metal contamination in Brunette Watershed stream sediment to identify temporal and spatial changes in mercury contamination since 1973. 2. Identify if mercury correlates with organic carbon, iron oxyhydroxides, manganese oxyhydroxides, sulfur and other trace metals in stream sediment, lake sediment, stormwater and laboratory controlled redox conditions. 3. Identify if mercury, iron, manganese and organic carbon are released from lake sediment to overlying water under anoxic conditions. 4. Investigate if MMT could be responsible for the increase of mercury concentrations in the Brunette Watershed stream sediment by examining correlation's between manganese and mercury. This project used a combination of field and laboratory data along with historical data. Laboratory microcosm experiments was designed to identify mercury's reactions to various environmental conditions in an effort to identify geochemical associations. Stream and lake sediment throughout the watershed was analyzed to determine temporal and spatial trends over the last thirty years in an attempt to locate sources and transport mechanisms. Stormwater was studied to identify features involved in contaminant transport. 1.3 Mercury sources and environmental contamination Total releases of mercury to the environment in Canada is estimated at 20 tonnes per year (Hagreen et al. 2004). Releases of mercury are classified into two broad categories, natural and anthropocentric. According to EPA documents, the amount of mercury in the atmosphere is estimated to have increased by 200 % to 500 % since the beginning of the industrial revolution (Obenauf and Skavroneck 1997). Recent estimates calculated that anthropocentric emissions have tripled the concentration of mercury in the ocean over the 5 last century (Mason et al. 1994). Other reports indicate that there is 3 to 6 times more mercury today vs. pre-industrial times in Atlantic Ocean water, Atlantic bird feathers, peat bogs, soils and lake sediments (Obenauf and Skavroneck 1997). Currently, atmospheric mercury originates from 25-40% natural sources and 60-75% anthropocentric (Mason et al. 1994). Natural sources of atmospheric mercury are mainly in the gaseous elemental form (Porcella et al. 1996). These sources include volcanoes, forest fires and off gassing of soils, vegetation and the ocean. Mercury is mined and used because its unique physical and chemical properties make it very useful for industrial processes. Its release into the environment is often unintended, accidental or a by-product of industrial processes. Anthropocentric sources to the atmosphere include incineration, chloro-alkali plants, metal extraction processes, cement production, coal, oil and gas incineration, (Table 1.1 and 1.2). Incineration of refuse is considered the second largest global source of atmospheric mercury, [Table 1.1] (Pacyna 1996). A recent report indicated that 1 in 12 or 5 million people in the United States contain levels of mercury above levels considered safe by the U. S. Environmental Protection Agency [EPA] (UNEP 2003). The United States Research Council estimated that about 60,000 6 Table 1.1 Estimate of annual releases of mercury from purposeful uses in Milwaukee, Wisconsin. The area is 420 square miles with population just over 2 million. [Adapted from (Obenauf et al. 1997). Releases to Media Sector Amount (kg/yr) Percent of Total Air (kg/yr) Solid Waste (kg/yr) Wastewater (kg/yr) Refuse Incinerators 149 35% 149 0 0 Fluorescent Lamps 57 13% 0 57 0 General Industry 46 11% 0 0 46 Dental Facilities 45 11% 0 18 27 Switches -Automotive 32 8% 3 23 6 Thermostats 32 8% 0 32 0 Batteries 23 6% 0 24 0 Households 18 4% 0 0 18 Switches -Lighting 7 2% 0 7 0 Hospitals and Medical Facilities 3 1% 0 0 3 Switches -Appliances 2 <1% 0 1 <1 Crematories 1 <1% 1 0 0 Landfills 1 <1% 0 0 <1 Veterinary Facilities 1 <1% 0 <1 0 Septic 0 0% 0 0 0 Total for Purposeful Uses (lb/yr) 418 ' 0 152 163 102 Total for Purposeful Uses (percent) 0 100% 37% 39% 24% 7 Table 1.2 Estimate of annual releases of mercury from processes that release trace impurities in Milwaukee, Wisconsin. The area is 420 square miles with population just over 2 million. [Adapted from (Obenauf et al. 1997).] Releases to Media Sector Amount (kg/yr) Percent of Total Air (kg/yr) Solid Waste (kg/yr) Wastewater (kg/yr) Coal Combustion Utilities 157 65% 125 31 0 Secondary Metal Smelting 31 13% 31 0 0 Motor Vehicle Combustion 22 9% 22 0 0 Oil Combustion Industry 16 7% 16 0 0 Oil Combustion Residential 14 6% 14 0 0 Coal Combustion Industry 0 0% 0 0 0 Lime Production 0 0% 0 0 0 Total for Trace Impurities (pounds) 329 0 207 31 0 Total for Trace Impurities (percent) 0 100% 87% 13% 0% babies born each year in the U.S. could be at risk of brain damage with possible impacts ranging from learning difficulties to impaired nervous systems (UNEP 2003). Human mercury contamination has also been linked to cardiovascular problems including raised blood pressure, palpitations and heart disease (UNEP 2003). Effects on the brain can include irritability, tremors, disturbances to vision, memory loss, impaired coordination and other adverse effects (UNEP 2003). Fetuses, the newborn and young children are particularly vulnerable because of the sensitivity of their developing nervous system 8 (UNEP 2003). Other effects have been found on the thyroid gland, which regulates growth, the digestive system, the liver and the skin including peeling on hands and feet, itching and rashes (UNEP 2003). As of December 2000, mercury was the contaminant responsible, at least in part, for the issuance of 2,242 fish consumption advisories by 41 US states (Bigler 2003). Furthermore, 79% of all fish and wildlife advisories issued in the United States are at least partly due to mercury contamination in fish and shellfish (Bigler 2003). EPA advisories for mercury have increased 149% in 7 years, from 899 advisories in 1993 to 2,242 advisories in 2000 (Bigler 2003). On January 12, 2001, the EPA and U.S. Federal Drug Administration (FDA) jointly issued a press release notifying the public of a national fish consumption advisory due to mercury contamination (Bigler 2003). EPA's guideline recommends if a person is pregnant, could become pregnant, nursing a baby, or feeding a young child; consumption of freshwater fish caught by family and friends should be limited to one meal per week (Bigler 2003). For adults, one meal is six ounces of cooked fish or eight ounces of uncooked fish; for a young child, one meal is two ounces of cooked fish or three ounces uncooked fish (Bigler 2003). The FDA has also released a consumer advisory recommending children and women, with or planning to have children, should avoid eating shark, swordfish, king mackerel, tuna steaks and tile fish. Safeway, Kroegers, Trader Joe's and Whole Foods, (large grocery store chains in California) have voluntarily agreed to post FDA warnings about mercury contamination of the previously listed fish at seafood counters. 1.4 Atmospheric processes and transport Atmospheric deposition is considered the dominant pathway for mercury contamination of aquatic systems, without a point source (Fitzgerald et al. 1991; Watras et al. 1996; EPA 1999). Forms of deposition include direct wet/dry deposition and indirect sources like terrestrial runoff. Uncertainty exists about how the cycling of atmospheric mercury has changed with the addition of anthropocentric sources. The majority of uncertainty lies in assessing historic levels and processes (Fitzgerald et al. 1991; Guentzel 2001). 9 Currently in the atmosphere, 97-99% of mercury is in the zero oxidation state as gaseous elemental Hg (Hg°) (Fitzgerald et al. 1991; Lindqvist et al. 1991; Nater et al. 1992). The remaining 1-3% is comprised of particulate Hg (Hgp) or reactive gaseous Hg(ll)) (Lindqvist et al. 1991; Natef et al. 1992). Gaseous elemental Hg has a residence time in the atmosphere of up to 1 year (Fitzgerald et al. 1991; Lindqvist et al. 1991; Nater et al. 1992). Hg(ll) and Hgp can reside for days or weeks in the atmosphere (Lindqvist et al. 1991; Nater et al. 1992). Hg° can enter the global mercury cycle and travel up to 10,000 km (Porcella et al. 1996). Hgp or Hg(ll) are deposited near the emission source (50 km) (Porcella et al. 1996). When deposited mercury is almost exclusively in the Hgp form (Porcella et al. 1996). It is difficult to predict residence time and distance transported due to local variability in weather and the atmosphere (Porcella et al. 1996). Of the estimated 158 tons of mercury emitted annually into the atmosphere by human activities in the United States, approximately 87 percent is from combustion point sources, 10 percent from manufacturing, and 3 percent is from all other sources (Obenauf et al. 1997). Speciation, climate and meteorology of anthropocentric mercury determine the distance traveled (Guentzel 2001). 1.5 Aquatic processes and transport The intent of this study is to analyze mercury transport in an aquatic, urban environment^abirz et al. 1998). Urban watersheds have shown higher yields of mercury than forested and rural areas (Hurley et al. 1995; Mason et al. 1997). This is due to a lack of soil for binding, high stormwater fluxes and runoff due to impervious surfaces. Stormwater has been implicated in the movement of particulate mercury in aquatic systems due to the resuspension of sediment, increased runoff and disturbance of lake's hypolimnion (Jackson 1982; Mason et al. 1997; Benoit et al. 1998a). Inorganic mercury will typically enter a freshwater system bound to various inorganic and organic particles. There is some uncertainty as to what conditions govern binding distribution. These particulates are predominately moved under high-flow or stormwater conditions until particulates settle to the bottom of the system. Studies have concluded that high-flow events lead to increased mercury transport (Hurley et al. 1995; Masoned al. 1997; Babirz et al. 1998; Benoit et al. 1998b). Aquatic mercury transport 10 generally occurs through a combination of two separate processes; mercury bound to suspended particulate matter (SPM) or bound to dissolved organic carbon (DOC). A large body of research exists suggesting mercury in an aquatic environment predominately bonds to organic carbon (Watras et al. 1994; Mason et al. 1997; Benoit et al. 1998a; Meyers 1998). Organic matter has a strong affinity for mercury so it typically correlates well in transport and sediment (Meili 1997). Inorganic ligands, (iron and manganese oxyhydroxides, reduced sulfur compounds and clay minerals) generally correlate in systems with low levels of organic matter (Meili 1997). Furthermore, some research indicates that in eutrophic, circumneutral waters, mercury will predominately bind with iron and manganese oxides (Jackson 1982; Jacobs et al. 1995; Quemerais et al. 1998; Reggnell et al. 2001). The role of these different inorganic ligands in dissolved and particulate mercury transport is important but not well understood. Hurley et al. (1995) monitored river sites in Wisconsin which exhibited strong seasonal variations. They observed a strong correlation between filtered Hgt and DOC (r2= 0.61) during fall base flow but the relationship was reduced in the spring (r2= 0.14). This reduced relationship is most likely due to higher spring flows and increased SPM in the spring. Hurley et al. (1995) also compared land-use to mercury concentrations in 39 Wisconsin rivers and found urban areas had the highest spring and overall concentrations. Mercury bound to DOC is derived from porewater in "marsh like" areas (Hurley et al. 1995; Babirz etal. 1998; Benoit et al. 1998b). In urban watersheds, it seems that mercury transport is typically associated with SPM (Gill et al. 1990; Mason et al. 1997). SPM originates from run-off, suspended sediments and bank erosion (Hurley et al. 1995; Babirz et al. 1998). Spring flows are generally higher, which would increase the amount of suspended particulate matter. Vasiliev et al. (1996), analyzed mercury transport by different fractions of suspended sediments in the spring and summer. They found that particles in the <0.45 «m fraction had the highest concentration of mercury while the >50 um had the highest overall contribution to transport. The middle fractions mimicked these overall relative trends. It is difficult to deduce the mobilization of mercury by examining the Brunette Watershed as a whole. This is due to the various mechanisms that can control transport. The upper catchments of the Brunette Watershed can be characterized by having a short 11 residence time. In these areas, it is likely that mercury transport is typical of other urban waters. 1.6 Geochemical processes of mercury in aquatic sediment Sediment plays an important role in mercury transport and biogeochemical cycling. The biogeochemical cycling of mercury in sediment can be controlled by ligands. Ligands are polar molecules or anions that surround a metal ion in a complex (Brown et al. 1991). It is important to differentiate between mercury bound to ligands and other forms because ligands can determine sedimentation rates and bioaccumulation rates in animals. Metal oxides, including hydroxides and oxyhydroxides are ligands that may directly or indirectly control the mobility and transport of mercury in oxic and anoxic environments. Iron and manganese oxides form labile complexes in particulate, colloidal and dissolved forms. The stability of these oxides are highly dependent on pH and redox potential (Meili 1997). Reducing conditions can create an increase of mercury (Hg) and possibly methylmercury (MHg) in anoxic waters (Regnell et al. 1996). Released ionic iron and manganese may also compete with mercury for sulfur binding sites, increasing the quantity of dissolved mercury available for methylation. Therefore, under oxic conditions sediment acts as a sink for mercury and methylmercury. While under anoxic conditions, mercury could be released from the sediment or converted to HgS. In an oxic environment, MnOx and FeOx form strong bonds with Hg and organic matter. Porcella et al, (1995) suggest that FeOx have a mass related affinity for Hg ten times higher than organic matter alone. Quemerais et al, (1998) research indicates that organic carbon only attracts mercury when metal hydroxides are present, when they are removed, no relationship can be found. Also, FeOx and MnOx can be the main mercury complexing agent when their relative abundance is high (Meili 1997). This is indicated by coenrichment in dissolved and anoxic waters and as solid precipitates in a variety of boreal, temperate and tropical sediments. Iron and manganese oxides may also regulate the potential for methylation by scavenging organic and sulfur binding sites (Reggnell et al. 2001). Regnell etal (2001) have identified a correlation between Fe, Mn and MHg in water of seasonally stratified lakes. Jacobs et al, (1995) studied an urban, eutrophic lake near Syracuse, New York, that experiences summer stratification, similar conditions to Burnaby Lake and found a strong 12 relationship between MHg and manganese. This is explained by "The reduction of Fe (III) requires a lower redox potential (or pe) than Mn. In addition, the oxidation of Fe (II) in the presence of oxygen is typically very rapid; thus, Fe diffusing across the redoxocline is rapidly converted to the particulate form [Fe (III)]. Mn oxidation kinetics are slower, and Mn oxidation has been attributed to Mn-oxidizing bacteria that are present at the redoxocline" (Jacobs et al. 1995). 1.7 Mercury and methylmercury in aquatic systems Aquatic cycling of mercury is a complicated process that involves many pathways (Figure 1.2). Inorganic mercury and organic mercury (forms of methylmercury) are distributed and behave very differently in various aquatic systems (discussed in section 1.5). Inorganic mercury in a freshwater lake will also bond with a variety of substances and take many forms. The majority of inorganic mercury in a freshwater system is bound to sediment. Within a lake system, it is possible for the top 3 millimeters of sediment to hold the equivalent mass of mercury as the entire overlying body of water (Meili 1997). Within water, mercury is bound by sulfur, dissolved organic carbon (DOC) and inorganic complexes, such as MnOx and FeOx. Only a small fraction of mercury is found in biota (typically around 1%), relative to the rest of an aquatic system (Porcella 1994; Meili 1997). Conversely, methylmercury does bioaccumulate in biota by biomagnification and bioconcentration (Meili 1997). This can create up to a 104 fold increase in concentrations between upper and lower biota in the food chain (Meili 1997). Methylmercury (MHg) is generally a high percentage (95-99%) of the total''mercury found in fish (Porcella 1994; Meili 1997). Fish accumulate MHg through gills and food; therefore, foraging habits and proximity to sediment regulates uptake (Porcella 1994). It is eliminated very slowly from the liver, kidney and spleen (Meili 1997). The concentration of mefhymercury in biota is thought to depend on the rate of methylation and demethylation within the system and the substrate to which the ingested mercury is bound (Meili 1997). Mercury methylation rates are the highest in the presence of steep redox gradients and high microbial activity (Krabbenhoft 1996). The combination of steep redox gradients and high 13 Figure 1.3 Conceptual model of mercury cycling and pathways for a typical freshwater lake (Krabbenhoft et al. 1997). DEPOSITION u Hfflt) DEPOSITION IJ/ AND RUNOFF ifl: ii AQUATIC MERCURY CYCLE DEPOSITION VOLATILIZATION AND DEPOSITION VOLATILIZATION AND OEPOSSTIGM CH3HQ0ePOSmON AND RUNOFF J METrfMTlPK-SEDIMENTATION BIOMAGNIf (CATION- t • Uti I USIOt, SEDIMENT RESUBPENStON SEDIMENTATION m / M microbial activity are generally located at the hypolimnion or in sediment with anoxic and oxic layers (Krabbenhoft 1996; Meili 1997). Methylation seems to be a fairly consistent process while demethylation is variable (Meili 1997). Demethylation tends to be highest in oxic waters (Watras et al. 1994). It has two pathways, irradiation from sunlight and breakdown by microorganisms (Krabbenhoft 1996). Although, it is theorized that methylmercury production in the oxic zone is important to mercury cycling because overall levels may be masked by demethylation, the location of production may increase bioavailability. This could lead to an increase of MHg bioavailability in the oxic zone. 14 The current paradigm of aquatic contamination is the location and level of MHg in the water governs the level of biota contamination, not inorganic mercury. Therefore, lakes with the highest net production of MHg have higher contamination in piscivorous fish. Typical water quality characteristics of these lakes include low pH, alkalinity, hardness and low overall biota productivity. High productivity, eutrophic lakes typically have low levels of contamination in biota because mercury binds to organic matter and sediments out of the system. Overall, eutrophic lakes generally contain more mercury in sediments than oligotrophic. In eutrophic lakes, organic matter binds mercury and sediments it out of the system. Large quantities of plankton and algae biomass also dilute mercury concentrations. 15 2. CHARACTERISTICS OF THE BRUNETTE WATERSHED 2.1 Site Description The Brunette Watershed is a 73 square kilometer urban area that flows into the Fraser River in New Westminster (GVRD 2001). At least a portion of the watershed is within the municipalities of Vancouver, Burnaby, New Westminster, Coquitlam, and Port Moody. Centralized in the watershed is Burnaby Lake, a receiving area for the upper catchments. Five main streams Still Creek, Eagle Creek, Deer Lake Brook, Ramsay Creek and Stoney Creek feed the lake (Figure 2.1 and Table 2.1). Sub-basins were delineated for Still Creek and the Brunette River with the Brunette Watershed. The Still Creek sub-basin includes catchments 1,2,3 and 7 in Figure 2.1. Brunette River sub-basin includes catchments 5, 6 and 10 in Figure 2.1. Still Creek carries approximately 58% of the flow to Burnaby Lake (Hall et al. 1976). The upper reaches of Still Creek and most other streams have a steep slope, along with its channelized banks and culverted stretches and produces quick stream velocities (Table 2.2). The lower portion of Still Creek (below Gilmore Street) has a decreased slope, increased channel width and backwater effects from the lake that contribute to low stream velocities. Stormwater drainage systems and groundwater contribute to the bulk of the watershed flow. The stormwater flow is considered flashy and carries a large particulate load in stormwater events. 16 re 2.1 Map of the Brunette Watershed and tributaries and catchments (GVRD 2000a). Table 2.1 Catchment name, number and imperviousness from Figure 2.1 (GVRD 2000a) Catchment Catchment number Imperviousness (%) Upper Still Creek 1 68 Middle Still Creek 2 58 Lower Still Creek 3 52 North Burnaby Lake 4 0 Upper Brunette River 5 37 Lower Brunette River 6 54 Beecher Creek 7 55 Eagle Creek 8 36 Deer Brook Lake 9 38 Stoney Creek 10 33 Ramsey Creek 11 33 Table 2.2 Average slope of catchments within the watershed (Hall et al. 1976) Upper Still Creek Still Creek to Gilmore St. 15 m/km slope Burnaby Lake Gilmore St. to Cariboo Dam 0.5 m/km slope Brunette River Cariboo Dam to Fraser River 2.5 m/km slope Burnaby Lake is 140 hectare in area, shallow and eutrophic, with a large amount of surrounding marsh (Fitzgerald et al. 1991). Bottom waters and sediments turn anoxic in the summer, which has resulted in fish kills (GVRD 2001). Mean water depth in 2001 was 0.97 meters (Enkon 2002). The sediments are a mix of silt, clay and amorphous peat in marsh areas (Enkon 2002). Four but of five of the larger catchments within the watershed flow into 18 Bumaby Lake. The water level in the lake and flow in the Brunette River are controlled by the Greater Vancouver Regional District (GVRD) lake outlet at Caribou Dam. Water leaving Caribou Dam flows into the Brunette River, then into the Fraser River. The Brunette River slope and flow is initially moderate, but decreases as it nears the Fraser River (Figure 2.2). This is due to a decrease in slope and tidal effects from the Fraser River. Surrounding Burnaby Lake is a small "green space" called the Burnaby Regional Nature Park. A medium density residential and commercial/industrial land-use encompass the park. The watershed has a history of trace metals contamination (Hall et al. 1976; Duynstee 1990; Macdonald et al. 1996a). This is attributed to large sediment loads, stormwater runoff and a high percentage of impervious surfaces within the watershed. Land-use and imperviousness can be useful indicators of pollution sources. Land-use changes over the last thirty years have been moderately increasing (Table 2.3). Impermeable cover has increased 7% from 1973-1993 (Table 2.4). Since 1993, the density of development has undoubtedly increased, but it has not been quanitfied. Table 2.3 Land use in the Brunette Watershed in proportion to the total area in 1973 and 1993 (McCallum 1995). Land Use % 1973 % 1993 % Change Residential 40.8 45.7 + 4.9 Industrial 11.9 13.2 .+ 1.3 Commercial 3.6 4.1 + 0.5 Institutional 6.6 6.4 -0.3 Agricultural 1.4 0 - 1.4 Open Space 32.9 28 -5 19 Table 2.4 Land cover in the Brunette Watershed in 1973 and 1993. (McCallum 1995) Land Cover % 1973 % 1993 Permeable 66 59 Impermeable 34 41 20 2.2 Historic contamination in the Brunette Watershed The Brunette Watershed has become highly contaminated with a wide range of pollutants due to its urban environment. Stormwater loading calculations for nutrients, organic matter and a few trace metals (Cu and Zn) were the highest when compared to 22 other extensively studied locations in the United States (Hall et al. 1998). A variety of organizations have collected information about the microbial, organic and trace metal contamination over the last 35 years. The University of British Columbia (UBC), Simon Fraser University (SFU) and the British Columbia Institute of Technology (BCIT) have compiled valuable research about the watershed. These groups have worked together to share information and find solutions to various environmental problems. Federal, provincial, regional and city government agencies have also monitored the area and provided funding. These studies indicate the high levels of contaminants have negatively impacted the watershed ecology. Toxicity bioassays demonstrated that stormwater runoff were periodically toxic to Daphnia (Hall et al. 1988). Later, chironomid (Chironomus tentans) bioassays indicated that elevated contaminants in Still Creek impacted their survival rate and weight, relative to an unimpacted site (Smith 1994). ( 2.2.1 Trace Metal Contaminants Baseline trace metal contamination throughout the watershed was first quantified by Hall et al. (1976). McCallum (1995) analyzed Burnaby Lake and Deer Lake core samples for trace metals and found a steady increase in Cu, Cr, Cd, and Ni from 1950-1970. This increase is attributed to land-use changes and industrial discharges throughout that time frame. Since monitoring began, surface water and sediment criteria intended to protect aquatic life have often been exceeded for Pb, Cu, Zn and Cr (Swain 1989; McCallum 1995). Comparison studies by Duynstee (1990) and McCallum (1995) identified many variables that contribute to the increase in stream sediment concentrations. These variables include land-use, automotive traffic and imperviousness. Spatial analysis of stream and street sediment indicates traffic contributes a large proportion of the Pb, Cu, Mn and Zn to the watershed. Also, impervious surfaces create a pathway for trace metals and other contaminants to be transported into waterways. 22 Hall et al. (1976), Duynstee (1990) and McCallum (1995) all indicated that Still Creek is the largest source of contaminants into Burnaby Lake. Duynstee (1990) and McCallum (1995) attributed contamination levels to high levels of industry, automotive traffic and impervious surfaces. UBC conducted mesocosm flow-through experiments with benthic invertebrates in the Brunette River (Richardson et al. 1998). This study found that benthic invertebrates most sensitive to heavy metals exposure were largely absent from the Brunette River watershed and concluded that heavy metal contamination throughout the watershed contributes to the degradation of the watersheds aquatic ecosystems. Mercury contamination data in the Brunette Watershed dates back to Hall et al. (1976), when the first comprehensive survey of stream sediments was conducted. Concentrations of mercury increased 294 percent from 1973-1993 in streambed sediments (McCallum 1995). Correspondingly, Mn increased 131% in total and 2600% in extractable forms respectively. McCallum (1995) suspects this large increase in manganese oxides is a result of automobile combustion of the gasoline additive methylcyclopentadienyl manganese tricarbonyl (MMT). In 1992, analysis of mercury in three carp livers from Burnaby Lake resulted in the following concentrations 114, 99 and 128 wg/kg dry weight (BCIT 1992). 2.2.2 Organic contaminants Organic compounds can have a strong effect on mercury transport and distribution due to there large size and binding strength. High levels of polychlorinated biphenyls (PCB's), 1,1-bis (4-chlorophenyl)-2,2,2-trichloroethane (DDT) and chlorinate phenols have been found in Still Creek and detected throughout the watershed (Hall et al. 1974; Hall et al. 1976). These are a group of synthetic chemicals that are highly stable and were commonly used in industrial and commercial processes. These chemical compounds have been proven to cause negative effects on animals and humans, including cancer, immune system, reproductive system, nervous system, endocrine system and other health effects. Chlorinated hydrocarbon (DDE, DDT and PCB's) levels in stream sediment have been decreasing from peak concentrations between 1940 -1970 (McCallum 1995). This indicates that increased regulation has been effective in reducing chlorinated hydrocarbon levels in the aquatic environment. 23 Polycyclic aromatic hydrocarbons (PAH's) are known carcinogens which can be derived from coal, tar and petroleum and are emitted by combustion related activities. Morton (1983) presented evidence of PAH bio-accumulation in fish and attributes the stream contamination to automotive sources, street deposition and runoff. Larkin (1995) used core samples to determine that total petroleum hydrocarbon (TPH) concentrations have increased tenfold over the last 200 years. Analysis of streambed sediments indicated industrialized regions had the highest hydrocarbon levels. Transport mechanisms were also identified from catchment land-use (automotive activities), dilution of street runoff by stream volume and traffic intensity on mean hydrocarbon concentration in stormwater. Overall, public awareness and pollution prevention practices have been implemented to reduce the overall levels of trace metals and hydrocarbons. Although, PAH's are likely still increasing due to rising automotive use. 2.2.3 Microbial Contaminants Fecal coliform is a classification of bacteria used to identify the presence of human waste contamination. High levels of fecal coliform have been detected in the watershed for sometime. This is due to a combination of urban runoff and leaking or illegal stormwater cross-connections to sewer lines. Monitoring has identified high levels in Still Creek and contamination throughout the watershed. This has caused the closure of waterways throughout the watershed to primary contact recreational activities for sometime (Hall et al. 1998). 24 3. METHODS Laboratory analysis methods will be described in sub-section 3.3 (Laboratory analysis). 3.1 Streambed sediment sampling and analysis Aquatic sediments bind trace metals, govern aquatic toxicity and affect transport processes. The historic variation of trace metal contamination in streambed sediment's were determined in this urbanized watershed through streambed sampling, analysis and then comparison to historic data (1973-1993). Thirty streambed sediment samples were collected and analyzed for a comparison with historic data collected over the last 30 years. Sampling locations and analytical methods used in Hall et al. (1976) were also used in this study for data compatability (Figure 3.1). Statistical analysis was then used to look for historic trends and associations. Statistical analysis was also used to identify correlations between metals and sediment quality. These correlations could improve knowledge of aquatic geochemistry within the watershed. 25 3.1.1 Streambed sediment locations Thirty sampling locations were used to replicate previous work by (Hall et al. 1976; Duynstee 1990; McCallum 1995) by using the same site locations and identification numbers. Some sites had to be excluded due to urban development (Table 3.1). Table 3.1 Locations excluded due to urban development Site number Description of location #5 Small stream north of Trans-Canada Highway. West of Hart St. between Roderick and Henderson St. Feeds Brunette River directly above site #4. Appears to have been culverted for new housing. #23 Still Creek at Sperling Avenue. Located after the confluence of Beecher Creek and Still Creek. Inaccessible from the road. #28 Beecher Cr at Westlawn Dr. Appears to have been culverted for new housing. #12, 18, 22 and 36 Excluded from (McCallum 1995) due to culverting between 1973 and 1994. J 3.1.2 Sediment sample collection Sediment samples were collected with an aluminum pot attached to a three meter wooden pole from a minimum of five composite locations within the site, (Hall et al. 1976). Except for site #1, in which replicate samples were obtained with an Ekman Dredge. Samples were screened with a 2 mm plastic sieve to remove larger material and sealed in double layer, high-strength plastic bags for storage. Samples were stored in <4° C refrigerator prior to sample preparation. Sampling occurred on April 26, 27 and 30, 2003. 27 3.1.3 Sediment sample preparation and analysis Sediment samples were removed from the refrigerator and allowed to warm to room temperature before analysis preparation. Then, the samples were sub-divided, with a portion of sediment removed for a wet vs dry comparison. The other portion was used in the metals analysis. Samples were analyzed wet, then dried at 105 ° C for 24 hours and reanalyzed to determine the percentage of mercury lost in the drying process. Sample preparation for metals analysis was the same as previous studies (Hall et al. 1976; McCallum 1995) to allow for a consistent comparison of data. This portion was wet-sieved with a stainless steel 180 wm sieve; distilled water was used to increase particulate recovery. Sieving was intended to reduce spatial bias created by varying particle sizes at different locations when a composite sample is taken. The <180 um sediment fraction was dried in a 105° C oven for a minimum of 24 hours. Sub-samples of the dried sediment were prepared for various analyses. 3.2 Lake sediment microcosm experiment 3.2.1 Microcosm sample collection Sediment and water samples were collected from the Burnaby Lake rowing center on November 17, 2002. Water samples were taken with a large, acid-washed plastic container. Sediment samples were taken off the northwest corner of the Burnaby Lake Rowing Center's floating dock with an aluminum pot on the end of a 3-meter wooden pole. Sediment was then placed into double plastic bags and frozen within 6 hours of sampling. 3.2.2 Microcosm Laboratory Experiment Laboratory experimentation was intended to replicate seasonal redox conditions within the lake. It allowed for a controlled, contained setting with limited variables. The experiment attempted to identify the reactions of metal hydroxides by comparing releases in anoxic and oxic conditions within sediment and the overlying water. There was a three-week trial experiment from November 17 to December 9, 2002 with 4 separate microcosms (Experiment 1), followed by a 6 microcosm study from February 9 to March 25, 2003 (Experiment 2), [Figure 3.2]. 28 Figure 3.2 Diagram of a single microcosm with traps. gas flow intake to microsom 0 o o o I gas flow from microcosm to mercury traps water sediment gas flow exhaust mercury trap 29 The microcosm setup process was similar for both Experiment 1 and Experiment 2. The glass microcosms and traps had a respective 1.5 and 0.1 liter volume. The soil was sieved with a 2 mm plastic screen to remove large particulates, then centrifuged at 4000 rpm for 30 minutes to remove most of the interstitial porewater. A 100 grams of wet sediment was placed in each microcosm. The average concentration of mercury in the sediment was 550.7 ppb. 1.2 L of 20 um filtered lake water was gently poured into microcosms 1, 3 and 4. De-ionized water was added to #2. Mercury traps were filled with 90 mL of potassium permanganate solution (0.5M KMn04 in 10% nitric acid) to capture any volatilized mercury. Microcosm 4 had 20 mmol/L molybdate ions (4.84g @ 241.95 g/mol) added to inhibit mercury methylating bacteria (Regnell 1994). The glass containers were wrapped in black plastic to prevent light induced volatilization of mercury. The microcosms were allowed to settle for one day before sampling and the gas flows were started. Air was pumped at a slow rate into the aerobic microcosm 1. Nitrogen gas was bled into microcosms 2, 3, and 4 at a similar rate to create anoxic conditions in the microcosm. The microcosms were operated at ambient laboratory temperature («20°C). Individual microcosm conditions for Experiment One and Two displayed respectively in Figure 3.3 and Figure 3.4. 30 Figure 3.3 Experiment I, four different microcosms were set-up for the initial three-week trial run. 100 grams of homogenized sediment and 1.2 liters of water was placed in each microcosm. / 1 (1) (2) -Lake sediment -Lake sediment v -Lake water -D.I. water -Anoxic (N2 gas) -Anoxic (N2 gas) 1 ^ (3) (4) -Lake sediment -Lake sediment -Lake water -Lake water -Oxic (air gas) -Anoxic (N2 gas) -Molybdate ions added. 31 Figure 3.4 Experiment II, six microcosms were set-up with the same parameters as the first run for the six week analysis. Each contained 100 g of sediment and 1.2 L lake water. The following variables were in each microcosm: 2) Burnaby Lake sediment Burnaby Lake water Anoxic (N2 gas) 4) Still Creek Sediment Still Creek Water Oxic (Air gas) 6) Burnaby Lake sediment Burnaby Lake water Anoxic (N2 gas) Molybdate ions added 1) Still Creek Sediment Still Creek Water Anoxic (N2 gas) 3) Still Creek Sediment Still Creek Water Molybdate ions added Anoxic (N2 gas) 5) Burnaby Lake sediment Burnaby Lake water Oxic (Air gas) 32 3.2.3 Microcosm sampling Sampling was performed weekly by using acid washed plastic syringe and tubing to withdraw 120 mL of water from the middle of each microcosm. Half of each sample was filtered with a 0.45 wm hydrophobic filter and then subdivided for metals, mercury and DOC analyses. Each mercury sample was preserved with 2 mL/L HCI in acid washed bottles, metals with 2 mL/L HN03 and DOC with 2 mL/L H3PO4 (Phosphoric Acid). Water quality measurements were performed on the DOC sample to avoid contamination of the metals or mercury sample. Although the U.S. Environmental Protection Agency (1999) requires "ultra-clean" procedures for sampling and storage of mercury samples in water; recent studies have indicated that storage in PET and HDPE plastic bottles is acceptable for mercury samples at or above 0.5 ng/1 (Fadini et al. 2000; Hall etal. 2002). Therefore, PET and HDPE plastic bottles were used in this study. 3.2.4 Microcosm analysis methods Specific conductance, pH, dissolved oxygen and DOC were analyzed according to methods in section 3.3.7, mercury in waters 3.3.3 and mercury in soil 3.3.4. All samples were analyzed within 7 days of the microcosm completion. 3.3 Laboratory Analysis 3.3.1 Aqua-Regia digest To prepare stream sediment for trace metal analysis, a 1.0 + 0.01 gram, homogeneous dry weight sample was digested with and 4 mL of (1+1) nitric acid and 10 mL of (1+1) hydrochloric acid. The sample was refluxed on an 85° C hot plate for 30 minutes. After cooling, the sample was brought to volume in a 100 mL volumetric flask. The sample was given time to settle before analysis on the ICP (refer to 3.3.2). 3.3.2 Trace Metals Soil samples were aqua regia digested and analyzed with an ICP-AES (UBC Soil Science Lab). Iron and manganese concentrations were determined by analyzing undigested microcosm water samples with a Varian SpectrAA 220 flame AA (UBC Civil Engineering 33 Laboratory). A four-point curve was used for calibration. The detection level for iron and manganese was 50 ppb. 3.3.3 Mercury in Waters Cold BrCl digestions of water samples were analyzed with a Millennium Merlin PSA 10.025 by cold vapor atomic fluorescence spectroscopy (CVAFS) (Analytical 2001). The method detection limit of the instrument (4.1 ng/L) was calculated as (n-1 @ 99% confidence) multiplied by the standard deviation of 10 samples. A 30 mL sample was digested by adding 7.5 mL of 33% HC1 and 1 mL of 0. IN potassium bromate/potassuim bromide then brought to a 50 mL total volume with deionized water. This solution was capped and allowed to stand for no less than 30 minutes. Immediately prior to analysis, 30 uL of 45% hydroxylamine hydrochloride was added to remove any remaining bromine. The instrument was calibrated with a five point curve with a minimum linear regression of 0.995. A blank and check sample, of known concentration, was run after every 20 samples to ensure data quality and reduce instrument drift. 3.3.4 Mercury in sediments Sediment samples were analyzed with a Lumex RA-915 Mercury Analyzer with a Zeeman processor used for interference and background correction (Lumex 2001). A 900° C pyrolysis oven ionizes the undigested sediment sample before it was vacuum pumped into the AA cell. The instrument was calibrated with various concentrations of Hg+2 mercury standard in methyl alcohol. The methyl alcohol solution was allowed to evaporate at room temperature, leaving a mercury residue on the sample boat, which was then inserted into the instrument. A four-point curve was used for calibration with a minimum linear regression of 0.995. Instrument accuracy was measured by the analysis of certified reference soils and surrogate check samples. Precision was measured by relative percent deviation (RPD) of replicate samples. After calibration, 0.050-0.200 grams of dry sediment was analyzed. A blank and check sample (of known concentration) were analyzed after every 20 samples to ensure data quality. 34 3.3.5 Percent Total Carbon in sediment A Leco induction furnace analyzer (model no. 572-200) in the UBC Soils Laboratory was used to measure total organic carbon, using a sample size range of 0.1-0.5 grams (APHA 1989). 3.3.6 Total Sediment Solids One gram of wet sediment was weighed and dried for a minimum of 24 hours at 105°C (APHA 1989). The sample was then re-weighted to calculate the loss of moisture. 3.3.7 Water Quality Measurements Table 3.2 The following parameters were analyzed in the UBC Civil Engineering Laboratory pH Measured with a Beckman 44 pH meter using "Standard Methods" (APHA 1989) Dissolved Oxygen. Measured with a YSI model 54A using "Standard Methods" (APHA 1989) Specific Conductivity Measured with a Radiometer CDM3 using "Standard Methods" (APHA 1989) Dissolved Organic Carbon Samples were filtered with a 0.45 wm hydrophilic Millipore filter membrane and analyzed with a Shimadzu model TOC-500 using "Standard Methods" 1030 (APHA 1989). 3.4 Statistical analysis Non-parametric statistical methods of analysis were used in this project because the majority of sample sets were not normally distributed. Also in the case of sediments, the interaction between metals is very complex therefore sediments cannot be considered independent variables. Summary statistics (mean, median, etc.) Kruskal-Wallis rank test and Mann-Whitney U test determined with S-Plus 6.1 Student Edition. Normality tests were performed on 35 JMPIN version 3.2.6. Box-whisker plots and Spearman rank correlation coefficients were determined with SPSS version 11.5. Box-Whisker plots were used to display distributions of analytical values (Figure 3.5). The box contains 50 percent of the values with a line in the box representing the median. The absolute difference of the box ends are labeled Hspreads. The "whiskers" extend 1.5 Hspreads from either direction of the box. An asterisk designates samples between 1.5 and 3 Hspreads, with values greater than 3 Hspreads plotted with an open circle. The Mann-Whitney U test compares two non-parametric samples to determine if they are from the same population. The Kruskal-Wallis test is a non-parametric method of comparing means/medians of more than two populations. Spearman rank correlation coefficients aid in the identification of relationships between variables. Bonferroni's Correction was used to calculate the significance of more than two correlations for Spearman's rank correlation coefficients. Any data point below the detection limit of the instrument was given a value of half the instrument detection limit. Although there are more sophisticated and time-consuming methods that provide a better estimate of the true value (El-Shaarawi 1989, Gilbert 1987), this is also a standard method for addressing censored ("less-than" or "below detection limit") data. The mean was used for small populations (n<20) and the median was used for large populations (n>20) to limit the influence of outlying data points (Zar 1996). 36 Figure 3.5 Box-whisker diagram. Adapted from McCallum (1995) — whiskers K- hspread -^1 median 37 4. RESULTS AND DISCUSSION 4.1 Data quality An attempt was made to avoid deviations in previous methods to allow for valid comparisons between data sets. In some cases, newer methods, instruments or technology were used to improve data quality (Table 4.1). Depending on the method or analyst, various data quality control methods were used to ensure accuracy and precision. Blanks, sample spikes and check samples (of known concentration) were used every 20 samples to ensure data quality for mercury, water and soil samples (Appendix J). Sample spikes were used to check accuracy and determine the amount of matrix interference within mercury samples. If mercury data quality objectives were not met, the instrument was re calibrated and the samples were reanalyzed, (i.e. <20% relative percent difference (RPD) or between 75-125% surrogate spike recovery). Certified reference sediments were analyzed for trace metals sediment analysis (Table 4.2). Antimony and potassium were out of range for sediment QC reference samples but these are not elements of primary concern in this study. It should be noted that potassium is known to be a difficult metal to analyze on an ICP. Checks and blanks were used to minimize instrument drift and maximize precision for all samples. Table 4.1 Comparison of methods used in stream and lake sediment analysis in 1973, 1989, 1993 and 2003 (Hall, 1976; McCallum, 1995) Measurement Digest and Analysis Technique 1973 1989 1993 2003 Fe, Mn, Mg, Cd, Pb, Cu, Zn, Ni HNO3-HCIO4/ Flame AA HNO3-HCIO4/ ICP HNO3 / Flame AA Aqua-Regia digest / ICP Cr Direct analysis / DC-arc Spectrography HNO3-HCIO4/ ICP HNO3 / Flame AA Aqua-Regia digest / ICP Hg H2S04-H202-KMn04 Hydroxylamine / Cold vapour H2S04-H202-KMn04 Hydroxylamine / Cold vapour H2S04-HN03-KMn04 Hydroxylamine / Cold vapour Lumex AA with Zeeman processor and pyrolysis attachment 38 Table 4.2 Quality control data for sediment metals analysis. Results in ug/kg, dry wieght. Environmental Resource Associates: Reference Sample Catalog #540 Lot # D035-540. Element/ Method Limits mg/kg (from website) 5-Aug-03 7-Aug-03 10-Aug-03 Ave Within limits Al1 1000-50000 2614 3322 3593 3176 Y As1 50-400 174.8 190.3 167.3 178 Y B' 80-200 127.3 140.5 128.2 132 Y Ba1 80-3000 361.9 414.5 371.1 383 Y Ca1 1500-25000 3036 3334 2986 3119 Y Cd1 40-300 125.3 136.1 119.8 127 Y Co1 30-200 53.11 57.75 52.46 54 Y Cr1 40-300 117.7 129.6 118.2 122 Y Cu1 40-200 85.53 93.88 85.18 88 Y Fe' 1000-22000 5069 6378 7292 6246 Y K1 1400-25000 1070 1387 1469 1308 N Mg1 1200-25000 1260 1501 1509 1423 Y Mn1 150-2000 282.9 314.9 287.3 295 Y Mo1 5-250 56.70 62.19 57.89 59 Y Na1 150-15000 248.8 282.1 296.0 276 Y Ni' 40-250 168.1 183.7 161.3 171 Y P1 N/A 391.6 424.9 411.1 409 Y Pb' 50-250 155.6 170.1 153.9 160 Y Se1 50-250 86.95 96.99 89.33 91 Y Si1 N/A 560.9 594.8 884.8 680 Y Sb1 200-2000 144.0 161.3 144.7 150 N s1 N/A 1.7 N/A N/A 1-7 N/A Zn1 70-1500 223.1 245.6 220.1 230 Y Hg' 21.6-26.5 23.5 N/A N/A 23.5 Y Methods: 1. Aqua-Regia digestion analyzed with ICP 2. Lumex AA with pyrolysis oven 39 4.1.1 Variability between sample and methods: Determining the effects of drying samples Mercury and some of its complexes are volatile at room temperature and pressure. Therefore, a portion of mercury would be lost when dried in a 105° C oven, as described in Section 3.1.3. The effects of drying 2 mm sieved sediment samples were determined in a small experiment with 27 samples. Wet samples were analyzed before drying then there concentrations were adjusted based the percent of moisture in the soil. This was performed to estimate the amount mercury lost by drying the <180 um samples. The Wilcoxon Paired Sample Signed Rank Test was used to determine that wet and dry sample sets are significantly independent. The wet samples lost a mean 66.8% of their mercury content when dried (Figure 4.1). The high variability in the wet samples is not seen in the dry samples. Drying samples seems to normalize the distribution by lowering the highest wet levels considerably. A comparison of <180 win and 2 mm fractions is difficult because of the high variability of the wet samples relative to the dry. Using smaller fractions of sediment samples typically increases the metal concentration of the sediment (Wilber and Hunter 1979). It is not logical to assume the <180 um sediment fraction would have lost at least an equal percentage of mercury as the 2 mm fraction. Due to its higher concentrations, the <180 wm fraction is likely to have a higher bonding strength than the larger fraction. Smaller particles have a higher surface area, therefore a higher bonding strength. 40 Figure 4.1 Box-whisker plots comparing mercury concentrations in 2 mm wet vs dried stream sediment at 105°C (n=27) 140 120 100 Hg 80 (wg/kg) 4.2 Microcosm Experiments The intent of the microcosm experiments was to create controlled reduction and oxidation (redox) conditions to mimic seasonal changes within Burnaby Lake. Oxygen levels, bacterial activity and water chemistry were controlled throughout the experiment. The dissolved oxygen (DO)in the oxic microcosm was never recorded below 5.35 mg/L. In the microcosms filled with nitrogen gas, the DO was never recorded above 0.50 mg/L after the first week. Regardless of the type of water or gas in the microcosm, mercury was released from the sediment into the water Figure (4.2-4.5). 41 Figure 4.2 Microcosm 1 containing lake sediment, lake water under, anoxic conditions, for Experiment 1 11/18/02 11/25/02 12/2/02 12/9/02 Figure 4.3 Microcosm 2 containing lake sediment, de-ionized water and under anoxic conditions, for Experiment 1 0.0 -I r , , r-l 11/18/02 11/25/02 12/2/02 12/9/02 42 Figure 4.4 Microcosm 3 containing lake sediment, lake water under oxic conditions, for Experiment 1 2.5 ^ 2.0 o) 1.5 11/18/02 11/25/02 12/2/02 12/9/02 Figure 4.5 Microcosm 4 containing lake sediment, lake water with molybdate ions added under anoxic conditions, for Experiment 1 2.5 2.0 O) 1.5 1.0 G) X 0.5 0.0 11/18/02 11/25/02 12/2/02 12/9/02 43 Levels of mercury within the microcosms were quite high (Table 4.3). They ranged from 0.100-2.092 ug/L. The highest release of mercury and iron was in Microcosm 1. The second chamber released less mercury than microcosm 1 indicating the deionized water may have slightly inhibited the release of mercury possibly due to the lack of complexing substrate indicated by is slightly lower DOC concentrations (Appendix E-4). The oxic microcosm (3) increased 229% over four weeks. It is difficult to determine the sediments remained oxic or anoxic throughout because only the water was tested. Respiration of bacteria in the sediment may have lowered the oxygen content inducing the release of the metals. The anoxic microcosm (4) with molybdate ions added had an increase of 16%. Molybdate ions inhibit bacterial growth and have been shown to eliminate production of methylmercury by sulfate reducing bacteria (Regnell et al. 2001). Therefore, only geochemical releases of mercury would be observed in the microcosm. This could indicate the increases in the other microcosms were due to reduction of mercury bound to sulfate by methylmercury producing bacteria. 44 Table 4.3 Percent increase of mercury and iron in four microcosms over four weeks in experiment 1. Manganese concentrations were all below the 50 wg/L detection limit. Microcosm Hg increase over 4 weeks (%) Hg increase over 4 weeks (t/g/L) Fe increase over 4 weeks (%) Fe increase over 4 weeks ML) 1. Anoxic with lake water 1912% 1.99 1974% 2.13 2. Anoxic w/ DI water 444% 1.33 29% 0.18 3. Oxic 229% 0.40 59% 0.27 4. Anoxic with bacteria inhibited 16% 0.03 8% 0.13 45 Data analysis reveals that iron and mercury had a correlation coefficient of 0.599 but it was not statistically significant due to the small sample size. DOC and pH had a statistically insignificant positive correlation coefficient of 0.745, a= 0.031. DO and pH had a statically significant inverse correlation of -0.649, ct=0.006. The data for the microcosm experiments is located in Appendix E. Refer to Appendix E for microcosm data. In all of the microcosms, mercury was predominately associated with the dissolved phase. Particulate concentrations ranged from 6.6%-14.2%. Iron was associated with the particulate phase from 54.2%- 96.3%. This does not exclude mercury from binding with iron because dissolved iron concentrations are still around 100 times greater than the dissolved mercury concentration. Manganese concentrations were all below the detection limit of 50 ug/L, indicating that very little, if any was released into the overlying water. Either manganese oxides were not at high concentrations in the sediment or they released then re-sorbed by sulfur before they could be dispersed into the water column. Manganese has a higher reduction potential than iron, therefore it would reduce first, allowing it to fill up any of the available complexing sites in the soil, probably with sulfur (Jacobs et al. 1995). In addition, the oxidation of iron is typically very rapid (Laima et al. 1998). Therefore, iron diffusing across the redoxcline is rapidly converted to the particulate form. Manganese oxidation kinetics are slower compared to iron, and manganese oxidation has been attributed to Mn-oxidizing bacteria that are present at the redoxcline (Jacobs et al. 1995; Laima et al. 1998). Regnell et al. performed similar microcosm studies but also added radiolabeled 203HgCl (Regnell et al. 1991; Regnell 1994; Regnell et al. 1996; Regnell et al. 2001). In 1991, they found significantly more mercury in the water for the anaerobic columns. On average, 69% of mercury was in the dissolved form. They concluded that the oxic sediment was able to bind four times more mercury than anoxic sediment, most likely due to the presence of hydrous ferric oxides. In 1996, they found an average 43% increase in mercury in the anoxic water over the oxic, compared to an average 69.4% increase in this experiment. Radiolabled 203Hg was found to constitute 80-90% of the total methylmercury in anoxic water, but only 40-60% of the extractable. This may indicate that the production of methylmercury was occurring within the microcosms 1-3 in this experiment. 46 Methylmercury analysis was planned for Microcosm Experiment 2 samples but was not performed due to contamination problems in the experiment. Figure 4.6 indicates that mercury in the microcosms under slightly acidic or neutral and oxic conditions associate predominantly with oxide/hydroxides. Under reducing conditions, conversion to metallic mercury increases as pH decreases. Therefore, it seems j that in the oxic microcosms, mercury may have been converted from oxide/hydroxide to mercury (II) as the pH dropped on December 2, 2002. In the anoxic microcosms, mercury was probably converted from oxide/hydroxide to metallic mercury. Figure 4.6 Diagram of Eh-pH for mercury in aquatic systems. Adapted from (Veiga and Meech 1998). 2 r—i—I II i—III—i—i—r—i i—T pH : results fromPocone after Silva et al. (1991) 47 Mercury was volatilized in all of the anoxic systems. The first two traps contained 242 and Ml ug/L respectively. The fourth contained 104 wg/L, indicating that bacteria inhibited by molybdate may have reduced mercury volatilization. The oxic trap became clogged and overflowed which may have resulted in contamination of the trap. In microcosm experiment two, the six-week microcosm was completed. However the mercury samples were randomly contaminated before analysis. The mostly likely source of contamination was leaching from reused plastic bottles. It is likely that although the HDPE bottles were acid washed and rinsed thoroughly, contamination still leached from or permeated into the plastic bottles. 4.3 Suspended sediments in Still Creek and the Brunette River Historical information from a February 28, 1997 stormwater event was used in this analysis. Six stormwater samples were taken every two hours, along with sediment collected by a Westfalia Separator model KA-2-06-175 continuous flow centrifuge. An attempt was made to collect stormwater samples for this study to compare with historical data but was unsuccessful. In January 2003, stormwater samples were collected from Still Creek and the Brunette River. The samples were not analyzed due to an in-operational flow meter and contamination problems within the trace mercury laboratory. Other stormwater sampling events were planned but never occurred due to insufficient precipitation throughout the 2003 summer. Sekela et al (1998) results of the stormwater event indicated that the Brunette River had higher mercury concentrations in suspended sediments than Still Creek (Table 4.4). This trend is not seen in any of the other metals tested except for manganese. This is unusual because Still Creek is known to have higher levels of sediment contamination than the Brunette River (Hall et al. 1976; McCallum 1995). It is also unusual because Burnaby Lake is thought to act as a sediment and contaminant sink for the watershed, as shown in lower turbidity levels in the Brunette River. Furthermore, in the same storm event, Still Creek's total mercury concentrations in water were higher than the Brunette River's (Figure 4.7). 48 Table 4.4 Total metal concentrations in suspended solids collected with a continuous flow centrifuge during a February stormwater event on the Brunette River system, concentrations in mg/kg, dry weight. [Data from Sekela et al. (1998)] Parameter Brunette River Still Creek Suspended solids 34.3 47.6 Hg 0.615 0.146 Fe 54800 80800 Mn 2900 1260 Pb 175 254 Zn 557 772 Figure 4.7 A Box-whisker plot of total mercury concentrations in stormwater over a stormwater event, units in ng/L [Data from Sekela et al (1998)] 50 40 30 Hg 20 10 0 Brunette River Still Creek There are a few possible explanations for this anomaly. Burnaby Lake acts as a settling basin as indicated by the lower concentration of suspended sediments in the Brunette I o 49 River (Table 4.4). The first possible explanation is a natural or anthropocentric source of mercury either in the Brunette River or Stoney Creek. The second possibility could be contamination samples, which is always a possibility when working with trace metals analysis. Clean methods were not specified in the report. Finally, it is also possible that the sediment is desorbing mercury and manganese into the overlying water when anoxic conditions exist. This would explain the increase in mercury and manganese concentrations in Brunette River suspended sediments. The oxides that bond manganese and mercury in the sediment would breakdown under anoxic conditions, thus releasing oxidized metals into the interstitial pore water and overlying water where they would re-associate with suspended particulate matter or DOC (Regnell et al. 2001). Increased flow through the lake could mobilize mercury reduced in the lake's water, similar to the releases seen in the microcosm experiments. Studies have shown that lakes with marshes have higher mercury concentrations then those without (Hurley et al. 1995; Babirz et al. 1998; Sonesten 2002). The mean mercury concentration of stream sediments in the Still Creek sub-basin is 61.3 wg/kg. Burnaby Lake has an average concentration of 142 wg/kg (Enkon 2002). Although the lake sediment is less likely to be suspended in a stormwater event, it would likely have an impact on downstream concentrations. The higher lake concentrations may be due to vertical movement of reduced ionic mercury. It seems that Still Creek is behaving like a typical urban stream while the Brunette River may be showing the downstream effects of a wetland environment in Burnaby Lake. The lake is very shallow, eutrophic and surrounded by marsh. The Brunette River had 72% less suspended solids and 109% more total organic carbon than Still Creek (Sekela et al. 1998). It is possible that mercury deposited in the lake may alter bonding associations under the lake's anoxic conditions. Mercury transported into the lake bound to oxides would be released under anoxic conditions. Then, it could associate with dissolved organic carbon (DOC) in the sediment pore water or the overlying water, were it would be resuspended under high flow conditions. Regnell et al. (2001) found an increase of total mercury, methylmercury, iron and manganese simultaneously during a lake's summer stratification. They believe that these processes may be mediated by biological processes, due to the positive relationship of the metal oxides and methylmercury. 50 Data for each stormwater sampling site is located in Appendix D. Spearman Rank correlation was performed on the data from each stormwater sampling site but the small sample size (n=8) limits detailed statistical analysis (Appendix I). Iron and mercury in stormwater were significant at 95% with a coefficient of 0.829, a=0.042 for Still Creek, but was not significantly correlated in the Brunette River. Contrary to the total values, mercury was not significantly related to manganese at Still Creek and negatively correlated with 95% significance in the Brunette River. Iron, lead and manganese are correlated with 95% significance in the Brunette River. It is difficult to explain why mercury has an inverse relationship to all other metals at the Brunette River site but it may be due to lake sediments releasing mercury from disturbed, anoxic porewater (Benoit et al. 1998b; Hall et al. 1998). Flow for both systems increased over the eight-hour sampling period. Still Creek had consistent concentrations, except for one spike at 4:33 (Figure 4.8). Brunette River exhibits a first flush of high contaminants at the onset of increased flow (Figure 4.9). The Brunette River had little variability in concentrations except for a drop of 50% after the first hour. It is possible that the first hour concentrations are from the first flush of Stoney Creek and storm sewers below the dam, while the increase in flow and mercury is a result of higher flow from the lake. 51 Figure 4.8 Mercury concentrations in stormwater grab samples collected by Environment Canada in Still Creek on February 28, 1997 (Sekela et al. 1998). Bars indicate mercury concentrations and squares indicate flow. Figure 4.9 Mercury concentrations in stormwater grab samples collected by Environment Canada in the Brunette River on February 28, 1997 (Sekela et al. 1998) Bars indicate mercury concentrations and squares indicate flow. 52 4.4 Burnaby Lake sediment Recent studies have been performed examining sediment quality or contamination levels in Burnaby Lake. Lake coring has been used extensively as an effective method of sampling for temporal and spatial trends. Historical data was analyzed to examine trends within the lake sediment. McCullum (1995) collected three cores in the lake, two at the mouth of Still Creek and one on the north shore of the lake to determine the impacts of urbanization. As a follow up, Hall and Mattu (1998) collected 7 sediment cores around the mouth of Still Creek and Eagle Creek and on the north side of Burnaby Lake. These cores were analyzed for lead, copper, nickel, manganese, zinc and iron to determine temporal trends although both studies did not determine mercury concentrations. In 1999, Enkon collected and analyzed eighteen sediment cores from Burnaby Lake for trace metal concentrations as part of a pilot dredging program (Appendix C). The core sediments had a maximum depth of < 1.2 cm and were a composite samples. Cores had a mean mercury concentration of 0.15 mg/kg (Figure 4.10) and most of the cores at the mouth of Still Creek had a metal concentration that exceeded Environment Canada's ISQG guideline (0.174 mg/kg) (Enkon 2002). 53 Figure 4.10 Box-whisker plot of mercury concentrations in Burnaby Lake core samples, concentrations in mg/kg dry weight [n=18] (Enkon 2002) [Environment Canada's ISQG guideline is 0.174 mg/kg] In general, studies have found that lake sediment is made up of clay-silt material mixed with amorphous peat in wetland areas (McCallum 1995; Enkon 2002). Sediment levels of total organic carbon (TOC) ranges from 7-14% throughout lake sediment (Enkon 2002). High TOC levels is thought to be a combination of anthropocentric loading and naturally occurring peat and plant material. Historic sampling has shown that most metal concentrations typically decrease with depth. The exception was lead, which is expected to decrease since it was phased-out from gasoline in 1974. Gwendoline Lake is unimpacted by development and was used as a reference site in the McCullum (1995) study. The mean mercury concentration of two cores taken by (McCallum 1995) in 1993 at Gwendoline Lake were 0.191 mg/kg and 0.231 mg/kg. This is 0.084 mg/kg higher than the mean concentration found in Burnaby Lake. Therefore, its level of mercury contamination should not be above background (Table 4.5). The mean concentration in two cores from Deer Creek Lake's was 0.233 mg/kg and 0.219 mg/kg. All samples are composite core data; similar to the method used in the Enkon study for Burnaby Lake. Cores all exhibited little variation with depth. Both Gwendoline and Deer Creek Lake 54 average concentrations are over Environment Canada's Interna Sediment Quality Guideline (ISQG) of 0.174 mg/kg. This may be due to inputs of atmospheric mercury without the Table 4.5 Comparison of mercury concentrations in sediment from various locations. The Environment Canada guideline ISQC is 174 wg/kg. All concentrations in dry weight. Location Description of area Range of mercury concentrations (ug/kg) Gwendoline Lake Unimpacted, forested 181-224 Deer Lake Urban 221-238 Burnaby Lake Urban 60-440 Sweden * Remote lakes 13-300 Finland* Stratified, forest 134-277 Wisconsin* Pristine, seepage lakes 1-140 Wabigoon River, Canada * Wood treatment plant 1500-3000 * (Suchanek et al. 1996) dilution of sediment found in Burnaby Lake due to its high sedimentation rates (McCallum 1995). Mercury was detected in all of the fifteen lake core sites from Enkon (2002), with the exception of two. The highest observed concentration was 0.44 mg/kg, which is more than double the ISQG of 0.174 mg/kg. High mercury levels appear to be due to stormwater flow into the lake from Still Creek, due to spatial distribution. Statistical analysis indicated that mercury, manganese, iron and lead were all correlated with each other at 95% significance in Burnaby Lake sediments (Appendix G). Mercury was significantly correlated with all of the parameters. Sulfur and TOC also had a significant, positive relationship with each other. Mercury's correlation was positive and significant with TOC but not sulfur. The positive relationship of mercury and lead is most likely due to loading from streets and drainage systems. High lead and mercury concentrations are assumed to be from anthropocentric sources. Although lead concentrations have been decreasing over the last 30 years throughout the watershed, it has 55 been linked to deposition of automotive exhaust (McCallum 1995). Mercury's strongest correlation is with lead, (r =0.876). Similar transport processes from impervious surfaces are a likely explanation for this relationship. 4.5 Stream sediment Historic data from Hall (1975) Duynstee (1990) and McCallum (1995) was compared to current data from this study for this analysis of trace metal concentrations in stream sediment (Appendix A and B). The methods from previous studies were replicated to ensure data compatibility. The median mercury stream sediment value in 1973, 1989, 1993 and 2003 was 22.0, 90.0, 93.0 and 57.6 mg/kg respectively (Figure 4.11). Mann-Whitney U tests were run to determine that the levels each year were significantly different from the previous, except for 1989 and 1993 (Appendix K). Therefore, the mercury sediment increased significantly from 1973-1989, then levels remained statistically unchanged from 1989-1993. Mercury levels from 1993-2003 have significantly decreased by 35.4 mg/kg. A comparison of stream sediment mercury concentrations and Canadian Guidelines and U.S. regulations was made to determine if contaminant levels in stream sediment exceeded guidelines (Table 4.6). It should be noted that these concentrations do not accurately represent environmental conditions for two reasons and therefore can not accurately be compared to any guidelines or regulations. First, only the <180wm sediment fraction was analyzed and this is not representative of environmental conditions. Second, as part of the method used in this study, sediments were dried which has been shown to volitalize some metals like mercury. However, since a mean of 67% of mercury was lost from dried samples in this study, these data can be considered "minimum" values (refer to section 4.1.1). There were three samples above the Interm Sediment Quality Guideline (ISQG) level of 174 wg/kg, all measured in 1993 (Table 4.6). The highest overall site was 870.0 wg/kg in 1993, was the only sample tested over Environments Canada's probable effects level (PEL) of 486 wg/kg (Table 4.6). Even if the 2003 screened sediment was adjusted for the estimated 66.8% loss from drying the screened sediment, the lake mean concentrations are still 155% more than Still Creeks concentration. 56 Figure 4.11 Box-whisker plot of mercury concentrations (wg/kg dry weight) in Brunette Watershed stream sediment from 1973-2003. One outlier excluded from 1993 at 870 wg/kg. 60 60 o 1-4 -4—» o C o o 3 o 500 400 300 200 100 1973 1989 1993 2003 57 Table 4.6 Various federal guidelines, regulations and objectives for mercury for different water uses Organization Criteria Fresh water Sediment/Solids US EPA Regulations (U.S. E.P.A. 2003) Ambient water 0.144 ug/L Freshwater- acute exposure 2.4 ug/L pish consumption (FDA) 1 ng/L methyl mercury (wet weight) . Sludge/ public lands 17 ppm Environment Canada Guidelines (Canada 2002) Aquatic life 0.1 ug/L ISQG 174 ug/L PEL 486 ug/L Fish Contamination 33 ug/L methyl mercury ' (wet weight) BC Guidelines (Nagpal 2001) Drinking water 0.1 ug/L Aquatic Life (30 day Ave.) 20 ng/L w/ MeHg <0.5% THg 10 ng/L w/ MeHg <1.0%THg 4 ng/L w/ MeHg <2.5% THg 2 ng/L w/ MeHg <5.0% THg ISQG- Interm Sediment Quality Guideline PEL- Probable Effect Level When the 1989 sediment concentrations are adjusted for the loss of mercury associated with drying, concentrations were over Environment Canada Interm Sediment Quality Guidelines (174 wg/kg) at 9 sites, and Environment Canada Probable Effect Level 58 (486 wg/kg) at 3 sites (Table 4.7). The 1993 sediment concentrations adjusted for the loss of mercury associated with drying had concentrations in had 10 sites over Environment Canada's Interm Sediment Quality Guidelines (174 wg/kg) and 2 sites over Environment Canada's Probable Effect Level (486 wg/kg) (Table 4.7). Sediment from 1973 did not exceed any of Environment Canada's guidelines while 2003 had only one that exceeded the Interm Sediment Quality Guidelines (174 wg/kg) [Table 4.7]. Table 4.7 Adjusted mercury concentrations in stream sediment for a loss caused by drying that exceeded federal guidelines within the Brunette Watershed from 1973-2003 (Appendix L) [Concentrations in wg/kg, dry weight]. Year of sediment sampling Environment Canada Interm Sediment Quality Guidelines (174 wg/kg) Environment Canada Probable Effect Level (486 wg/kg) 1973(n=26) 0 0 1989(n=29) 9 • 3 1993(n=29) 10 2 2003 (n=30) 1 0 Figure 4.12 and 4.13 are box-whisker plots of surface sediments mercury concentrations in Still Creek sub-basins and the Brunette River sub-basins; Table 4.8 is a ratio of mercury concentrations in Still Creek sub-basins and the Brunette River sub-basins. In 1973 and 1989 the levels of mercury in the Still Creek were double in the lower Brunette River sub-basin. This study seems to indicate that mercury levels have normalized throughout the sub-basins. This may be due to a decrease in point sources along Still Creek and/or the distribution of mercury from the upper to the lower basin. The latter is reinforced by the increased levels of mercury in Brunette River suspended sediment relative to Still Creek (Refer to section 4.63, Table 4.9). 59 Figure 4.12 Box-whisker plot of mercury concentrations in the Still Creek sub-basin stream sediment from 1973 to 2003. 1000 DO 800i (30 a e o 1 "S D O a o o o <D 200 J 600 ^ 400-10 1973 12 1989 12 1993 12 2003 60 Figure 4.13 Box-whisker plot of mercury concentrations in the Brunette River sub-basin stream sediment from 1973 to 2003. 160 00 20 bfl a o "ia +-» c o cs o o 3 Table 4.8 Ratio of mercury concentrations in the Still Creek sub-basin and the Brunette River sub-basin in sediments and stormwater over a thirty-year period Media and year sampled * Still Creek / Brunette River Sub basins Stream sediment 1973 1.97 Stream sediment 1989 2.44 Stream sediment 1993 2.18 Stream sediment 2003 1.05 A Spearman rank correlation test with Bonferroni's correction was performed on trace metal data in stream sediment from each year to determine the extent of significant statistical correlation (Appendix F). Iron and manganese were significantly related with 95% confidence from 1974-2003. The highest mercury correlation was with percent sediment organic matter (0.208). Mercury exhibited a few trends over time. Mercury was correlated 61 to lead, copper, nickel and zinc with 99% significance from 1973-1993. It was correlated to chromium with 95% significance from 1989-1993. Figure 4.14 presents temporal relationships (1973-2003) of mercury to other trace metals found in stream surface sediments. Figure 4.14 Spearman's correlation coefficients for mercury in 180 wm stream sediment from 1973-2003. Data located in Appendix F. Lead, copper, nickel, zinc and chromium were all significantly related to each other from 1973-2003. McCallum (1995) found that Pb and Cr had a direct relationship with traffic volume in street sediment in 1993. A contaminant identification study identified vehicle exhaust emissions, tire wear and brake wear as the most significant non-point source of Pb, Cu and Zn in their study (Woodward-Clyde 1992; Armstrong 1994). McCallum (1995) also linked impervious area or traffic volume to Pb, Cu, Cr, Ni and Zn enrichment in 1993 stream sediment. Consistently high correlations over time indicates that some type of relationship exists, possibly due to similar transport mechanisms. From 1974-1993 the levels of mercury 62 in sediments increased throughout the watershed. This coincides with mercury's correlation with Pb, Cu, Ni and Zn (Appendix F). Concentrations of mercury decreased from 1993-2003 along with its correlation to other metals. It seems that the processes that contributed to the increase of mercury in the watershed between 1993-2003, reduced the relationship to other trace metals. Although, the process that contributes these other metals to the watershed are still present. 4.6 Comparison of mercury in stream sediment and catchments imperviousness Atmospheric transport is mercury's dominant pathway for non-point source contamination (Refer to section 1.3). Studies have shown that the catchment to lake ratio can be an indicator of mercury levels in fish and sediment. Swedish studies have discovered a significant correlation between the catchment to lake area ratio and the levels of mercury in fish (Bishop et al. 1997). A Canadian study used the same catchment/lake area ratio to significantly correlate mercury concentrations in sediment (French et al. 1999). Both of these studies examined remote lakes, and their watersheds where the only source of anthropocentric mercury was from the atmosphere. Urban watersheds have been shown to have higher stormwater yields of mercury than other land-uses (Hurley et al. 1995; Mason et al. 1997; Babirz et al. 1998). Urban development has created impervious areas where precipitation is unable to penetrate ground cover and infiltrate into the soil. Examples of impervious areas include buildings, roads, compacted soil and parking lots. Impervious area (IA) has a negative affect on water and sediment quality due to the run off of trace metals and other contaminants (Zandbergen et al. 1997; Zandbergen et al. 2000). Mercury distribution in a watershed is affected by imperviousness due to its transport mechanisms. Mercury resides and is transported in the atmosphere before it is deposited on land. When mercury reaches the ground or a waterway by either dry deposition or rainwater, it is almost always in the particulate form (Pacyna 1996). Mercury has a strong affinity for metal-oxides and organic carbon. If mercury is deposited on a pervious surface, it is likely that it will bond with organic material in soil (Bishop et al. 1997). Impervious areas increase the amount of runoff and mercury carried by the runoff. 63 Catchments and there impervious area were delineated by the GVRD in 2001 using GIS and GPS systems. All of the streams in the catchments used in this analysis are first order; except for the Brunette River, which has the lake as a source. Imperviousness decreases the likelihood of mercury binding to soil and contributes mercury run-off into a streams or lakes. Therefore, impervious areas create a pathway for mercury to reach streams. Effective imperviousness area (EIA) is assessed by quantifying the impermeable area connected to or discharging into a catchment. For example, a roof is only considered EIA unless the gutter is connected to the stormdrain but if the gutter runs onto the lawn it is not considered EIA. Impervious area and effective impervious area per catchment was calculated by McCallum (1995) in 1973 and 1993. The GVRD (2000a) calculated impervious area in 1996 (refer to Table 2.1). Average catchment concentrations was calculated with data from Appendix B and follow the trends of the overall watershed (Figure 4.15). McCallum (1995) divided up the watershed into two sub-basins, Still Creek and Brunette River, with respective impervious levels at 52% and 35%. The same sub-basins were also used in this study for comparison. The sample range was at least three times larger for 1993 concentrations than 1973 and 2003. There are three times the number of samples per catchment in 1993 as the 1973, 1989 and 2003 since the samples were taken in triplicate. The large number of samples in 1993 allows for a more detailed statistical analysis. Individual mercury catchment concentrations are shown in Figure 4.15. 64 Figure 4.15 Box-whisker plot of mercury streambed sediment concentrations (ug/kg) from six catchments in 1993. One outlier was excluded from Still Creek with a value of 2115 wg/kg. In 1993, three independent samples were analyzed at each site. 700 600 500 X3 Q. Q_ C o ro 400 c <D O C o o o \ CD 300 200 100 Brunette Still Stoney Eagle Deer Beecher Sediment concentrations from 1973, 1993 and 2003 were compared with corresponding imperviousness and EIA data. The Kruskal-Wallis Test provided sufficient evidence to conclude that catchment means were statistically different in 1973, 1993 and 2003. The linear regression for the 1973 study year did not have a good fit with EIA data due to the scattered data points and relatively low mercury concentrations (Figure 4.16). This may indicate scattered point sources or natural background sources. 65 Figure 4.16 Scatter-plot of 1973 stream sediment mercury concentrations (wg/kg) vs effective impervious area (hectares) from 1973. Line indicates the linear regression of the six area's 1000 800 600 400 co CD CD CO o '£ cu Q. .i 200 CD > LU 0 s Still • Dee? • D 3ruTrett» • Stoney • Eagle • Beecher • 25 50 75 100 Hg concentration 1973 The average mercury content increased 294% in stream sediment and all catchment concentrations increased substantially, between 1973-1993. A positive correlation was found between the effective imperious area within catchments and mercury in 1993 stream sediment (Figure 4.17). Spearman's correlation coefficient is 0.371 and 0.257 for EIA and IA respectively. This seems to indicate that EIA is a better fit than IA, which is logical considering mercury's run-off transport processes. Beecher Creek has the worst fit of all the catchments in the watershed, due to its high historic mercury content in a low impervious area. Beecher Creek is the most industrialized catchment and it is likely impacted by a combination of atmospheric sources and point-source spills/releases. Spearman's correlation coefficient is 0.900 (a=0.037) with the Beecher Creek point excluded. This seems to suggest that the watershed is affected by a combination of point source releases and runoff from impervious surfaces for a period before 1993. Atmospheric mercury could disperse relatively evenly over a 7200-hectare watershed. A possible high volume, localized source that fits into the 1973 to 1993 time 66 frame is the Burnaby Incinerator, which is located only four kilometers south of Burnaby Lake. Generally, westerly airflow from the Pacific Ocean prevents the watershed from having any high mercury concentration, long distance sources. High rainfall, typical in the coastal area would increase deposition of mercury released in the area, while atmospheric and'particulate deposits of mercury should decrease in concentration away from the source (Nater et al. 1992). Figure 4.17 Scatter-plot of 1993 stream sediment mercury concentrations (wg/kg) vs effective impervious area (hectares) Line indicates the linear regression of the six area's 1600-1 : : 1400-1200-1 Hg concentration 1993 The Burnaby incinerator was fully operational on March 1, 1988 and mercury releases peaked in 1989 at 1.8 kg/day . Vegetation and soil samples monitored for mercury near the incinerator from 1987-1989 displayed an increasing trend over time (McCallum 1995). Mercury releases from the incinerator have significantly decreased since 1993 due to the installation of an activated carbon injection system (McCallum 1995). The average mercury discharge in 1993 was 0.079 ng/m3 (Allen 2003). Estimates by Horvate (1996) of 67 global atmospheric concentrations of mercury are from 0.5-10 ng/m3. Which is significantly more than currently discharged from the Burnaby Incinerator and since the system was installed, discharges have averaged 0.031 ng/m (Allen 2003). This is over a 6 order of magnitude decrease in emissions since 1996. This state of the art system was the first to be installed in the North America and discharges are three times less than permits allow (Holt 2003). An attempt was made to draw inferences from the best available data but due to insufficient data, the 2003 sediment data was compared to 1996 imperviousness. Although densification probably has occurred in the area, it is assumed for this study that impervious areas and land-use has not significantly changed over the last 10 years. McCallum (1995) noted that imperviousness in the area had only increased 7% from 1973-1993. It is even more difficult to assume that impervious levels have increased proportionately within each catchment but the correlation is worth noting for the purpose of making comparisons. The 2003 sediment concentrations compared to the 1996 impervious area had a Spearman's correlation coefficient of 0.429, a=0.397 (Figure 4.18). Still Creek is an outlier with a high imperviousness relative to its mercury concentration. This could be due to a combination of factors like source abatement or effective use of Best Management Practices (BMP's) storm-sediment containment systems. 68 Figure 4.18 Scatter-plot of 2003 stream sediment mercury concentrations (wg/kg) vs total impervious area (hectares) from 1996. Effective impervious area data was unavailable for the period of 1994-2003. Line indicates the linear regression of the six area's 1600 Hg concentration 2003 4.7 Comparison of various analysis This project was an attempt to determine how the majority of inorganic mercury is being transported through the watershed, which includes ascertaining its forms and associations. This project examined various segments of the watershed independently, including suspended sediments, stream sediments, lake sediments and redox changes of Burnaby Lake sediment. The intent of this section is to compare and examine these segments together to determine if any significant trends exist. Suspended sediment, Burnaby Lake sediment and stream sediment data was analyzed from the watershed with Spearman's Rank Correlation Test and Bonferroni's Correction to ascertain if statically significant relationships exist between variables. It is difficult to compare concentrations due to the various methods used in analysis, but it is 69 possible to discuss their relationships (Table 4.9 and 4.10). These relationships will be characterized as changes of transport mechanisms, geochemical associations or similar source locations. Characteristics will be differentiated by evaluating literature, chemical properties and watershed attributes. Table 4.9 Comparison of sampling locations, matrix and methods for mercury determination in the Brunette Watershed. Location Matrix Method Lake Sediment Maximum depth of cores 1.2 cm Stream Sediment <180 wm surface stream sediment Suspended Sediments Sediment Centrifuge of suspended stormwater sediments Suspended Sediments Water Stormwater 70 Table 4.10 Mercury median or mean concentration in various media throughout the watershed. (Water concentrations in ug/L and sediment in wg/kg) Median / Mean Source Still Creek Sub-basin Burnaby Lake Brunette River Sub-basin Watershed Average Suspended Sediment '98 (Mean, n=l) (Sekela et al. 1998) 146 -615 -Stormwater '98 (Mean, n=12) (Sekela et al. 1998) 18.8 -28.0 • -Stream sediment '73 (<180um) (Median, n=27) (Hall et al. 1976) 46.0 -23.3 30.2 Stream sediment '89 (<180 um) (Median, n=29) (Duynstee 1990) 186.0 -76.1 133.0 Stream sediment '93 (<180 um) (Median, n=30) (McCallum 1995) 205.6 -94.2 132.9 Stream sediment '03 (<180 wm) (Median, n=30) Current study 61.3 -58.4 56.8 Enkon'02 Composite core (Median, n=15) (Enkon 2002) -142.0 - -Iron and manganese did not have a statistically significant relationship to mercury in Burnaby Lake sediment. Also the relationship was not found in stream sediment throughout the watershed. Iron was correlated to mercury in Still Creek stormwater but was inversely 71 related in the Brunette River stormwater (Spearman correlation coefficient 0.829 and -0.725 respectively). Manganese was inversely correlated with mercury in Brunette and Still Creek stormwater, (Spearman correlation coefficient -0.870 and -0.143 respectively). Iron and manganese were correlated with each other in lake sediment and every year of stream sediment, the lowest significance of 0.041 occurred in 1973. Iron and manganese have similar physical properties due to their similar atomic weight and atomic charges, yet behave differently under redox conditions. This may indicate that correlation comparison of metals in various segments can be representative of geochemical associations due to similar transport mechanisms, even though kinetic redox rates differ. Two elements that mercury typically has a high degree of correlation with are sulfur and dissolved organic carbon (Shafer et al. 1997; Benoit et al. 1998b; Regnell et al. 2001). In this study, different methods were used to quantify organic matter making it difficult to make comparisons between methods. The microcosm experiment with Burnaby Lake sediment resulted in a Spearman correlation coefficient of 0.651 and oc= 0.081 for DOC and mercury (Appendix K). Burnaby Lake cores were analyzed for total organic carbon and correlation confidence to mercury, (Spearman correlation coefficient 0.634, a=0.011) [Appendix G]. In stream sediment, total carbon was used as an approximate indicator of total organic matter and the relationship with mercury was found to be very low. Organic matter was not analyzed in stormwater. Total sulfur was only quantified in lake and 2003 stream sediments. No statically significant correlation was found between mercury and sulfur concentrations. Two separate environments exist within the Brunette Watershed. The western portion of the basin is highly urbanized with a steep elevation gradient. In these systems, mercury generally associates with suspended particulate matter (SPM). This section feeds Burnaby Lake, which is characterized as shallow and dystrophic, more comparable to a marsh. In these systems, mercury is typically found in the dissolved form or associated with colloidal particles (<0.45 um) (Hurley et al. 1995; Babirz et al. 1998; Benoit et al. 1998b). Lead generally had the strongest relationship with mercury throughout the various segments of data. They both were significantly correlated with 99% confidence in Burnaby Lake sediment and every year of stream sediment except 2003 (cc=0.071) [Appendix G and 72 F]. It has the strongest relationship with mercury out of all the Burnaby Lake core samples (Spearman correlation coefficient 0.876) [Appendix G]. No significant correlation was found in the stormwater event (Appendix I). This, combined with a decreasing relationship in 2003, could indicate that sources or transport mechanisms are changing. Lead will not form any strong chemical association with mercury but may associate with similar particles. Lead has a higher partitioning coefficient (Kd) for SPM / DOC in a variety of watersheds than Zn, Cd, Cr and Cu, but mercury's Kd will depend on the type environmental conditions (Shafer et al. 1997). From 1993-2003, it should be noted that concentrations of lead and mercury decline throughout the watershed. Lead concentrations in the environment have been steadily declining in North America since their phase out from gasoline in 1986. Copper, chromium, nickel and zinc appear to have the same temporal trend in all media except for the stormwater study. It is possible that correlations in stormwater were not observed due to a low number of samples (n=8). In the watershed, copper, chromium, nickel and zinc all had a positive, significant statistical relationship to each other. Copper is significant with mercury at 0.001 in lake sediment and stream sediment in 1973 and 1989. Copper, chrome, nickel and zinc all have a significant relationship with iron in 2003. Overall, mercury in sediments had the strongest relationships with Pb, Cu, Ni and Zn in relative order. Due to their varying chemistries and sources, it seems that this relationship is primarily due to similar sources and/or transport processes, in which all of these metals have been linked to automotive sources. It is difficult to explain why the mercury's relationship to other metals decreased in 2003 but the large reduction in point source mercury concentrations from the incinerator may be one explanation. It seems very little can be determined about the geochemistry within the watershed with the current data. Mercury has only weak relationships that can be identified for iron, manganese, sulfur and organic carbon. These three parameters, based on literature, are typically found to geochemically associate with mercury. 4.8 Possible Sources Mercury is found extensively throughout the world. Global studies analyzing sediment cores concluded that mercury concentrations have increased around 3-5 time's since pre-industrial times (Krabbenhoft et al. 1997). The intent of this section is to account 73 for the mercury source that led to an average 102.9 wg/kg increase in stream sediment over twenty years (Hagreen et al. 2004). Overall, concentrations in the Brunette Watershed range from low to moderately contaminated. Gwendoline Lake is an undisturbed, forested site and mercury sediment concentrations there are higher there than in Burnaby Lake. Although increased lead concentrations in core samples taken from Gwendoline Lake indicate that atmospheric processes have transported lead, the same scenario is possible for mercury. Point-sources may have also increased the mercury concentration in localized areas. Mercury is commonly used in fluorescent lights, electrical switches, batteries, laboratory, medical facilities and general industry processes. Data from 1989 and 1993 studies indicates that Still Creek has the highest concentrations in the watershed and sediment cores at the mouth of the stream are also relatively high. Burnaby Lake core and stream sediment samples taken from the watershed strongly correlate high levels of Hg, Cu, Fe, Pb and Zn. Mercury is presumably released from a variety of industries along with Cu, Fe, Pb and Zn metals, although the 2003 distribution does not indicates any detectable point sources. It is possible that a pulse of mercury was released in Still Creek and/or Beecher Creek in the 1980's and 1990's and it is currently being distributed down-gradient. Sediment mercury concentrations have decreased since 1993 due to an increase in awareness of mercury's hazardous affects and controls on its use. Mercury concentrations increased dramatically throughout the watershed between 1973 and 1993 and sources that could uniformly distribute mercury concentrations over the entire watershed are limited. Source transport processes including mercury leached from the soil by MMT or deposited from the atmosphere are both possibilities. In theory, both scenarios would run-off impervious areas and therefore should correlate well with effective impervious area. Mercury in street dirt has also increased significantly from 1973-93 (McCallum 1995). The source of mercury in street dirt is most likely a combination of atmospheric or automotive sources. But for the tentative assumption that MMT is leaching mercury out of soil to be true, there should be some type of correlation between mercury and manganese in sediment loading, geochemistry and transport, which was not observed anywhere in the watershed. Also, the microcosms experiment released very little, if any manganese. This also reinforces the idea that manganese oxides are not a dominant process in the transport of mercury. 74 McCallum (1995) suspects the nearby Burnaby incinerator is a contributing source of mercury to the watershed due to its proximity, which released up to 1.8 kg/day in 1989 (McCallum 1995). McCallum (1995) also found a significant correlation "that traffic density is responsible for a large part of Pb, Cu, and Zn contamination in urban streams". McCallum (1995) associates all of these metals with automotive deposition and runoff. Another study indicated that yields to aquatic sediment from atmospheric mercury of urban watersheds are 40-100% higher then forested, rural areas (<10%) (Mason et al. 1997). Increased imperviousness, surficial runoff and the lack of organic binding sites are suspected processes for higher levels of mercury in urban areas. Mercury deposited from atmospheric sources is almost always bound to particulate; regardless of wet or dry deposition (Pacyna 1996). It is highly likely that particulates released from an incinerator would be associated with other metals like Ni, Cu, Pb and Zn. How long these associations would last through transport would depend on their bonding strength and environmental conditions. If the incinerator were responsible for the large mercury increase in watershed concentrations, it would have to be a rapid process. The incinerator became operational in March 1988 and stream sediment sampling was next performed in May 1989. It is feasible that mercury could be released, deposited and washed into streams leading to a 68.0 wg/kg median increase in concentrations from 1973-1989, especially with the regions high level of precipitation (Figure 4.19 and 4.20). The decrease of mercury from the incinerator could also be related to the decreased level of mercury observed throughout the watershed sediment in 2003. Mercury follows a similar trend of most other metals in the watershed from 1973 to 1989. It is highly correlated with lead, copper, nickel and zinc through this time (Figure 4.20). This may indicate similar transport mechanisms because these other metals have been linked to automotive sources and they do not react geochemically with mercury. Figure 4.19 and 4.20 indicate that mercury is the only metal that increases from 1989 and 1993. All other metal concentrations decrease from 1989. This is probably due to an overall increased awareness of the presence of toxic metals in urban sediments and implementation of sediment control best management practices by the GVRD. After 1989, mercury's correlation to most other metals drops and this trend continues until 2003. 75 Mercury concentrations peaked in 1993, the same year that air scrubbers were installed at the Burnaby Incinerator. Figure 4.19 Metal median concentrations in <180 um stream sediment from 1973-2003. Mercury in wg/kg. Iron in mg/kg. Manganese in wg/kg x 0.1 76 Figure 4.20 Metal median concentrations in <180 um stream sediment from 1973-2003. (All metals in ug/kg) 77 5. SUMMARY AND CONCLUSIONS The results of this project are summarized in the following sections. Contaminant levels from different media and time frames were compared and evaluated for trends. Temporal changes are representative of historical trends in watershed. Due to problems with laboratory results in microcosm Experiment II, water quality parameters could not be compared to sediment concentrations and other parameters. Therefore, focus was shifted to examine the temporal relationship between trace metals within stream sediment. These conclusions are discussed in the following, Section 5.3. 5.1 Temporal and spatial changes in mercury and trace metal contamination since 1973 One important temporal trend identified in this study is the overall level of mercury in stream sediment has started to decline in the watershed. This decrease is probably due a combination of increased public awareness and a decrease of releases. Overall, the level of contamination in Burnaby Lake is similar to other nearby lakes, Deer Lake and Gwendoline Lake, both of which are not connected to stormwater drainage systems. Due to its remote location, contamination in Gwendoline Lake is primarily from atmospheric deposition. Mercury concentrations in Brunette Watershed stream sediment are actually higher than reported in this and other studies because it was found that an average of 66.8% of mercury was lost in the drying process. When sediment concentrations were adjusted for the loss 1973, 1989 1993 and 2003 sediments exceed n=0, n=12, n=12, and n=l of the federal Interm Sediment Quality Guidelines, in respective order. Previous studies from 1973-1993 have shown that mercury concentrations were highest in the Still Creek Sub-basin. Current 2003 data indicates that Still Creek Sub-basin mercury levels are approximately equal in the Brunette Sub-basin with at ratio of 1.05 (Still/Brunette). With an overall decrease in the watershed concentrations from 1993-2003, it is reasonable to conclude that source loadings are decreasing and mercury concentrations are being distributed downstream. The trends in Section 4.8 indicated the Burnaby incinerator was a probable source of mercury to the watershed from 1988-1993. Mercury seems to follow a trend similar to other trace metals within the watershed, except in a small period from 1989-1993 when 78 every metal concentration decreased from 1989-1993, except for mercury. Consequently, the incinerator was releasing its highest concentration of mercury into the atmosphere for the same period. It is well known that atmospheric mercury can lead to increased levels of mercury contamination in waterways. Mercury's transport mechanisms and geochemical associations after deposition are not as well known. Catchment effective impervious area may play an important role in determining the transport mechanism relative to mercury runoff. Although this needs to be examined further, when the Burnaby Incinerator provided a source, levels of mercury increased in stream sediment while all other metals decreased. Also, in that same time frame, mercury's correlation with the catchments effective impervious area was higher than without the incinerator releases. 5.2 Mercury's correlations with organic carbon, iron oxyhydroxides, manganese oxyhydroxides, sulfur and other trace metals in stream sediment, lake sediment, stormwater and laboratory controlled redox conditions From 1973-2003, mercury's correlations in stream sediment and Burnaby Lake sediment were highest with lead, copper, nickel and zinc. These four metals and chromium were all significantly related to each other from 1973-2003. This may be due to their similar anthropocentric sources and transport mechanisms, more than their geochemical associations. No consistent correlations were observed between mercury and organic carbon, iron oxyhydroxides, manganese oxyhydroxides and sulfur in stream sediment, lake sediment, stormwater and laboratory controlled redox conditions . 5.3 Levels of mercury, iron, manganese and organic carbon released from lake sediment to overlying water due to sediment anoxia Two separate microcosm experiments were performed to determine if anoxic conditions would lead to increased levels of mercury in overlying water. The first trial microcosm, from November 17 to December 9, 2002, displayed a release of mercury in all four microcosm chambers. This release coincided with a release of iron. The anoxic microcosm with lake water released 398% (1.59 ug/L) more mercury and 688% (1.86 ug/L) more iron than the oxic microcosm with lake water. It is suspected that methylmercury may have been 79 produced in the microcosms due to lower levels of mercury released when microbial activity was suppressed. Since the microcosms were intended to replicate seasonal redox conditions within Burnaby Lake, it is likely that similar releases of mercury and iron occur in the lake. (The second experiment ran from February 9 to March 25, 2003 without any results due to mercury contamination.) 5.4 MMT's responsibility for the increase of mercury concentrations in the Brunette Watershed stream sediment Little evidence compiled in this study supported the hypothesis that manganese, iron, sulfur or DOC is associated with mercury throughout the watershed. Thus, it is difficult to conclude or rule out that MMT or manganese oxides play a major role in the transport of total mercury. Overall, evidence that would lead to conclusions about mercury's geochemical association within the watershed from this study was inconclusive. In this study, mercury does not correlate with any substances typically found in the literature to have geochemical associations with mercury. Therefore, correlation's in stream sediment, lake sediment, stormwater and laboratory controlled redox conditions may not be the optimum method to examine a watershed's geochemical associations. Since a relationship between mercury and manganese was not observed in field data, microcosm experiments, stream sediment, and other studies were examined to determine other potential sources of mercury to the Brunette Watershed. 80 6. RECOMMENDATIONS The conclusions drawn from this study can be used to make better management decisions concerning the remediation and conservation in the Brunette Watershed and urban watersheds in general. Further research would enable improved understanding of the source, transport and fate of mercury and other trace metals in urban environments. 6.1 Implications for further research This project indicates source and transport processes to a waterway may be important to the distribution of mercury in stream sediments. Further research into effective imperviousness effect on mercury distribution in waterways and stream sediments is recommended. It may be an important component in modeling mercury's intermediary fluxes between air to aquatic transport. Other projects should examine the relationship between mercury in waterways and point-source releases, including a detailed examination of mercury concentrations in core samples from 1988- 1996 to identify temporal fluxes. Future work should investigate the levels of mercury and methylmercury within various media throughout the watershed. Due to methodological errors, historic concentrations of mercury in sediment and waters are suspect. More research is needed, using current methods, to determine levels of contamination throughout the watershed. Methylmercury is a highly toxic compound and the microcosm Experiment I indicated anoxic sediments might release methylmercury. Laboratory analysis should examine the relationship between MMT and mercury to reduce variables present in the environment. Further research is needed to identify levels of methylmercury in fish and other biota within the watershed. Then, if necessary, investigate levels of contamination in water and sediment. Further research is needed into mercury's geochemical associations and the release of mercury from anoxic sediments in the Burnaby Lake and other urban watersheds, possibly Gwendoline Lake could be used for a comparison. Burnaby Lake has the environmental conditions/cycling that would make it possible for sediment releases of stored mercury into the overlying sediment and thus downstream. For this investigation, methodologies involving microcosms to study mercury's geochemical relationships and stormwater sampling to study mercury's aquatic transport are recommended. 81 Also, it is important to determine if the biological and ecological health of the watershed has improved with decreased trace metal contamination. An ecological assessment conducted in 1998 by the UBC could be used to provide background information on contamination (Richardson et al. 1988) There has been a focus on improving the physical and chemical indicators within the watershed for sometime. It would be interesting to determine if improvements in physical and chemical indicators resulted in biological indicator improvements. 6.2 Management implications The GVRD is considering dredging Burnaby Lake to improve the recreational and environmental conditions. To prevent the need for further dredging, the GVRD and the Brunette Basin Task Group (BBTG) should continue implementing sediment control measures to reduce the influx of contaminated sediment into the lake. Environmental impacts of dredging would be dependent on the level of freshly exposed sediment. Enkron(2002) recommends the use sediment control devices to minimize the impact of suspended solids over a large area within the lake. Small mercury releases are possible from anoxic sediment due to sediment exposed by dredging; although mercury would have already had the opportunity for release when it was originally deposited. The planned sediment controls proposed by the GVRD should reduce the release of mercury and the transport of mercury and other contaminants. 82 7. LITERATURE CITED Allen, C. (2003). GVRD Waste-to Energy Facility Emissions (1991-2002), Greater Vancouver Regional District: 1. Analytical, P. S. (2001). 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Woodward-Clyde, C. (1992). Source identification and control report, prepared for the Santa Clara Valley Non-Point Source Pollution Control Program. Zar, J.H. 1996. Biostatistical Analysis 4th ed., Prentice-Hall. Zandbergen, P., H. Schreier, et al. (1997). Integrated watershed management. Institute for Resources and the Environment, University of British Columbia. Vancouver, B.C. Zandbergen, P., H. Schreier, et al. (2000). Urban watershed management CD. Institute for Resources and the Environment, University of British Columbia. Vancouver, B.C. 89 APPENDIX A Stream Sediment Sampling Locations Table A-l Stream sediment sampling locations Station Number Station Description General Remarks 1. Brunette R. at Spruce Ave. (bridge) At river mouth, wood products industries 2. Brunette R. at Camphor Ave., near railway bridge. Wood products industry nearby. 3. Brunette R. at Braid St. (bridge) Wood products industry nearby. 4. Brunette R. at Brunette Rd. Potentially affected by high traffic volumes 6. Brunette R. at North Rd. (east side) Sampled within Hume Park. 7. Stoney Creek at Grandview Hwy., 100m west of intersection of Hunter and Keswick Streets 8. Stoney Cr. at Beaverbrook Dr. and Noel Dr., samples obtained upstream and downstream of bridge. Residential area. 9. Stoney Creek at East Broadway, 50m west of Norcrest Rd. Residential area. 10. Brunette R. at Cariboo Rd., samples obtained upstream and downstream of bridge. Potentially affected by high traffic volumes. 11. Small stream arising from a storm sewer, south side of Winston St., east of Brighton St. Light industrial and residential area. 13. Eagle Creek on Piper Avenue, south of Winston St. Located in Werner Boat Park. 14. Eagle Creek at East Broadway (south side), bgetween Lake City Way and Lawrence Drive. Below golf course. 15. Tributary of Eagle Creek at Shellmont St. (north side), east of Arden Drive. Downstream of petroleum tank farm runoff detention facility. 16. Tributary of Eagle Creek at Woodbrook Place, east of Phillips Ave. Upstream of golf course, wooded stream buffer. 17. Robert Burnaby Creek, near park entrance at 4th St. Located within Robert Burnaby Park. 19. Deer Lake Brook at Glencairn Dr. (north side) North of freeway south of Burnaby Lake. 20. Deer Lake Brook at Deer Lake Ave., south of Canada Way, upstream and downstream of bridge. Downstream of Deer Lake. 21. Small stream at Moscrop St. (south side), Residential area downstream of 90 between Royal Oak Ave and Oaktree Ct. cemetery. 24. Small creek at intersection of Sperling Ave. and Jordan Dr. Residential area. 25. Beecher Cr. near Goring Ace., sampled on south side of railroad tracks Small tributary of Still Creek 26. Beecher Cr. at Lougheed Hwy. (south side) Upstream of station 25. 27. Beecher Cr. at Springer Ave. (east side). Upstream of station 26. 29. Small stream in Westburn Park along Gilpin Cr. 400m upstream of 1973 location. 30. Still Creek on Still Creek Dr., west of Willingdon Ave. Industrial area, heavy traffic. 31. Still Creek at Gilmore Ave. (east side). Industrial area. 32. North branch of Still Creek at Lougheed Hwy. (south side) Affected by heavy traffic. 33. Still Creek at Grandview Hwy. (south side) and Rndfew St. (east side) Residential area. 34. Still Creek at Myrtle St., east of Boundary Rd. Industrial area 35. Still Creek at Douglas Ave. Industrial area. 37. Still Creek at Atilin St. and 27th Ave. Wooded ravine. 91 APPENDIX B Concentration of trace metals in Brunette Watershed stream sediment from 1973-2003 Table B-l Streambed sediment, <180um fraction in the Brunette Watershed, total concentration in 1973 (Hall et al. 1976). Values in dry weight. Nitric acid digest for all metals except Hg. Mercury analyzed with potassium permanganate digestion and cold vapor analysis. 1973 Stations Fe Hg Mn Pb Cu Cr Ni Zn OM (mg/kg) (wg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) % 1 41600 44 716 104 52.3 175 41.1 136 6.4 2 36000 40 684 108 46.3 100 23.6 128 5.3 3 20800 52 652 134 44.4 50 15 117 6.3 4 25200 11 460 50 16.1 75 10 52 2.3 6 14000 11 165 50 12.3 100 7.4 47 2 7 22600 19 248 45 16.7 50 8.4 46 52.2 8 23000 • 14 444 .63 18.2 75 9 67 5 9 26000 20 275 39 17 100 9 60 2.3 10 19400 12 655 24 14.5 100 12.4 60 2.4 11 10800 10 196 14.5 13.9 50 5 32 7.4 13 24000 27 315 91 42 200 12.6 126 2.1 14 15200 30 325 10 12.3 0 8.4 65 2.5 15 50000 9 250 5 11.6 75 10 47 7.9 16 14800 13 205 26 15.8 700 11 47 2.5 17 23800 14 436 118 16.5 75 9.4 47 4.6 19 15600 18 242 292 48.6 50 14.4 136 2.2 20 24000 22 682 324 40.3 50 13.4 167 7.3 21 31800 18 875 58 40.4 125 20.8 118 7.9 24 24000 53 415 470 72.8 100 18.8 168 7 25 30800 29 328 950 82.9 100 194 199 2.2 26 23200 15 225 66 19 125 12 51.5 4.6 27 22600 22 468 48 17.8 100 8 69 9.4 29 73000 73 398 276 50.7 125 29 121 5.9 30 23800 101 211 440 684 100 33.6 206 6.4 31 2500 60 308 400 1765 150 23 168 1.8 32 22600 37 200 359 62.8 150 54 130 2.2 33 19400 34 294 34 52.7 50 10 100 3.8 34 36200 NA 114 600 95.1 200 19.2 305 29.7 35 33400 NA 425 840 816 NA 85 408.00 NA 92 Table B-2 Streambed sediment, <180wm fraction in the Brunette Watershed, total concentration in 1989 (Macdonald et al. 1996b). Values in dry weight. Nitric acid digest for all metals except Hg. Mercury analyzed with potassium permanganate digestion and cold vapor analysis. 1989 Fe Hg Mn Pb Cu Cr Ni Zn Stations (mg/kg) (ug/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) 1 379000 120 1108 169 91 75 35 263 2 381000 110 1203 180 77 73 33 218 3 325000 80 1187 155 77 53 25 177 4 385000 45 1123 142 58 57 17 148 6 333000 80 1398 245 91 50 23 211 7 297000 80 726 113 85 75 19 126 8 291000 35 727 85 61 48 18 106 9 330000 45 720 82 48 55 20 104 10 344000 90 2118 159 85 55 20 205 11 NA NA NA NA NA NA NA NA 13 190000 40 506 36 53 34 16 83 14 540000 35 1090 48 53 55 17 130 15 455000 40 1007 60 72 50 18 306 16 277000 50 756 90 63 47 21 120 17 350000 25 757 47 50 65 28 95 19 266000 95 1093 247 151 55 22 227 20 324000 105 2513 132 69 58 25 178 21 261000 115 640 356 108 63 24 202 24 782000 350 4083 577 262 94 31 443 25 363000 55 1084 145 83 70 23 163 26 329000 65 1101 143 80 64 21 150 27 299000 70 899 93 61 54 21 138 29 332000 90 701 176 83 61 24 212 30 300000 160 1152 388 234 59 27 298 31 254000 90 649 140 102 46 18 155 32 530000 365 554 667 394 131 59 445 33 448000 415 8794 444 267 93 34 759 34 390000 200 845 267 157 81 40 252 35 282000 120 676 170 106 62 25 208 37 350000 175 767 479 155 76 24 285 93 Table B-3 Streambed sediment, <180um fraction in the Brunette Watershed, total concentration in 1993. (McCallum 1995). Values in dry weight. Nitric acid digest for all metals except Hg. Mercury analyzed with potassium permanganate digestion and cold vapor analysis. 1993 Fe Hg Mn Pb Cu Cr Ni Zn OM Stations (mg/kg) (ug/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) % 1 32739 132 768 63 66 38 34 186 6.3 2 20929 132 534 62 51 41 24 134 5.4 3 26948 137 401 55 58 38 22 145 5.9 4 20199 51 1299 48 42 20 11 116 4.5 6 10437 57 561 48 31 15 7 111 3.2 7 20287 85 1009 37 32 24 13 87 4.6 8 13208 51 508 32 30 21 9 115 4.2 9 17474 115 807 96 51 26 12 95 4.7 10 30431 79 1435 407 141 35 19 310 8.1 11 22800 103 975 62 101 26 11 185 5.6 13 16994 45 1109 22 43 18 8 106 4.2 14 23872 50 791 39 34 18 9 93 3.7 15 44724 15 1553 24 45 19 6 163 7.8 16 28657 15 839 36 50 20 24 166 5.9 17 14822 60 474 40 97 40 14 161 4.8 19 9370 61 200 53 55 19 8 110 5.0 20 12923 69 1315 86 72 18 10 171 7.8 21 18421 95 906 60 52 30 17 146 6.3 24 27289 102 2004 190 119 45 21 391 5.0 25 13901 352 333 43 50 18 12 89 19.9 26 18178 64 869 72 55 24 11 128 4.2 27 21421 68 1273 73 56 29 16 196 6.5 29 11430 154 357 26 26 17 13 136 4.2 30 23219 121 346 127 195 34 28 262 4.6 31 23293 149 1334 141 279 33 16 341 r 7.1 32 12225 91 194 133 80 •31 15 140 10.6 33 23115 870 1440 307 162 33 19 278 5.2 34 21054 214 366 190 142 35 17 255 3.7 35 18787 137 287 116 142 37 18 , 283 5.9 37 14651 NA 722 207 199 38 19 271 3.0 94 Table B-4 Streambed sediment, <180um fraction, in the Brunette Watershed, total concentration in 2003. Values in dry weight. Nitric acid digest for all metals except Hg. Mercury analyzed with pyrolysis digestion and AA detection. 2003 Fe Hg Mn Pb Cu Cr Ni Zn OM S Cd Stations (mg/kg) (wg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) - % (mg/kg) (mg/k 1 20163 72.4 461 43 32 12 12 140 1.57 268 2.6 2 4707 26.3 171 9 8 8 7 39 0.40 75 0.6 3 20539 65.1 210 7 29 27 29 60 0.60 66 1.9 4 22179 20.1 224 8 31 28 30 62 0.65 71 2.7 6 7571 102.9 294 22 14 7 4 49 0.36 105 0.7 7 12456 78.8 503 15 24 11 9 86 1.25 161 1.3 8 7805 59.6 373 33 15 7 6 57 1.45 157 0.8 9 11897 44.3 511 31 32 13 8 104 1.45 232 1.4 10 14695 56.1 1594 67 78 20 13 190 1.22 329 1.9 11 36853 58.4 1490 62 87 26 13 311 2.84 389 4.4 13 16189 10.9 1587 20 22 11 7 136 3.20 324 1.8 14 7990 32.7 402 3 8 4 3 45 0.55 112 0.8 15 17670 56.9 927 8 14 7 4 124 1.69 173 1.7 16 12575 79.4 790 50 50 17 . 8 143 4.24 352 1.6 17 10846 85.5 153 622 176 19 9 220 4.26 872 1.4 19 20831 101.2 1725 93 103 27 13 301 13.90 1773 2.8 20 11884 28.2 1438 50 48 10 18 126 5.74 619 1.4 21 8492 33.1 509 18 20 8 6 68 1.93 164 1.3 24 17187 99.6 990 157 99 22 17 181 3.44 345 2.3 25 21693 24.3 1076 60 53 18 13 181 3.38 360 2.6 26 9231 62.1 361 29 28 11 7 83 1.93 195 1.1 27 15006 48.7 633 44 49 18 13 129 1.82 243 1.8 29 23528 110.8 1662 33 41 16 13 160 3.09 312 2.7 30 15228 51.7 212 54 76 18 11 162 1.16 285 1.8 31 15516 69.1 306 102 107 19 18 152 1.46 261 1.8 32 38807 46.2 312 270 162 49 33 403 4.73 729 4.6 33 24247 71.1 1439 168 166 37 19 359 3.31 545 3.8 34 31769 17.8 1601 186 126 38 23 366 2.52 801 4.6 35 8609 32.2 160 27 46 11 9 96 1.32 205 1.0 37 11140 102.0 201 69 55 22 9 106 0.81 274 1.5 95 APPENDIX C Metal concentrations in sediment cores from Burnaby Lake Table C-l Metal concentrations in sediment cores (depth < 2.0 cm) from Burnaby Lake (Enkon 2002) [mg/kg dry weight]. Refer to Figure C-l for site locations. (C) indicates composite sample was analyzed. Site Hg Mn Fe Pb Cu Ni Zn TOC S A-C 0.16 240 13300 153 80.9 17.6 177 14 2210 B-C 0.28 394 25100 514 189 26.9 476 8.3 2210 C-C 0.05 443 25700 4 35.3 16 55.2 0.24 234 D-C 0.06 180 10400 5 20 13.3 48.2 9.1 3290 E-C 0.1 243 15700 62 35.7 16.8 152 8 1870 F-C 0.08 232 1500 50 39.8 39.5 91.3 7.3 2170 G 0.07 252 9850 6 16.2 14.9 56.7 14 2580 H 0.06 233 15300 4 29.3 17.9 60.4 7.8 2690 I 0.05 219 14200 12 24.9 14.9 62.2 7.7 2400 J 0.1 201 9720 30 23.6 12.5 80.5 12 2970 K-C 0.26 420 16800 277 125 33.6 412 14 5430 L-C 0.25 323 20900 209 175 22.6 426 9.7 2700 M-C 0.2 291 17300 70 38.6 16.1 172 14 2470 N-C 0.05 218 10600 58 28.4 12.5 98 7.3 1030 OC 0.44 424 31500 533 254 36 571 12 4330 Figure C-l Location of Burnaby Lake sediment core sampling stations. Photo adapted from (Enkon 2002). O Burnaby Lake sediment core locations. ft North 96 APPENDIX D Total metal concentrations within a Brunette Watershed stormwater event Table D-l Total metals within a stormwater event on the Brunette River, February 28, 1997 (Sekela et al. 1998) Brunette River Flow time Hg Fe Mn (cms) (hr) (ng/L) (mg/L) (mg/L) 1.57 1:00 22.0 0.882 0.075 1.80 2:00 11.0 1.600 0.087 3.92 3:00 18.0 1.830 0.117 6.30 5:00 19.0 0.983 0.085 6.58 7:00 22.0 0.986 0.083 6.88 8:15 21.0 1.120 0.086 Ave 18.8 1.234 0.089 Std Dev. 4.1 0.387 0.015 Table D-2 Total metals within a stormwater event on Still Creek, February 28, 1997 (Sekela etal. 1998) Flow Time Hg Fe Mn (cms) (hr) (ng/L) (mg/L) (mg/L) 0.38. 1:00 27.0 1.790 0.240 0.66 2:00 23.0 1.740 0.234 1.59 3:00 26.0 2.540 0.225 1.97 4:15 39.0 4.280 0.179 2.81 5:45 25.0 2.080 0.088 4.90 7:45 28.0 3.020 0.098 Ave 28.0 2.575 0.177 Std Dev 5.7 0.966 0.069 97 APPENDIX E Microcosm data from Experiment 1, November 17 to December 9,2002 Table E-l Microcosm pH data from Experiment 1, November 17 to December 9, 2002. Note: Microcosm variables (1. Control, 2. DI water, 3. Oxic and 4. Molybdate ions) Microcosm 18-Nov-02 20-Nov-02 2-Dec-02 9-Dec-02 5.73 6.44 5.60 6.54 5.38 6.02 4.03 6.44 5.80 5.32 4.80 5.73 5.73 6.68 6.48 6.70 Table E-2 Microcosm conductivity data (uS/cm) data from Experiment 1, November 17 to December 9, 2002. Note: Microcosm variables (1. Control, 2. DI water, 3. Oxic and 4. Molybdate ions) Mbrocc^m^^ 70 126 112 620 12 38 54 34.7 73 108 112 75.0 70 2675 2525 1385 /" Table E-3 Microcosm dissolved oxygen data (mg/L) data from Experiment 1, November 17 to December 9, 2002. Note: Microcosm variables (1. Control, 2. DI water, 3. Oxic and 4. Molybdate ions) McI9COsm_ 18-Nov-0*2 20-Nov-02 02^Dec-02 09-Dec-02 1 2.0 0.45 6.35 0.20 2 3.4 0.55 0.5 0.20 3 2.1 5.2 5.1 5.8 4 1.5 0.5 0.45 0.15 98 Table E-4 Microcosm dissolved organic carbon data (mg/L) data from Experiment 1, November 17 to December 9, 2002. Note: Microcosm variables (1. Control, 2. DI water, 3. Oxic and 4. Molybdate ions) Microcosm 18-Nov-02 09-Dec-02 1 13 " 37 2 13 33 3 13 4 4 13 17 Table E-5 Microcosm mercury data (//g/L) data from Experiment 1, November 17 to December 9, 2002. Note: Microcosm variables (1. Control, 2. DI water, 3. Oxic and 4. Molybdate ions) Microcosm 18-Nov-02 25-Nov-02 1 0.104 0.47 2 0.300 0.204 3 0.173 0.081 4 0.173 0 02-Dec-02 09-Dec-02 09-Dec-02 Pis 1.3 2.092 1.953 0.88 1.631 1.400 0.758 0.570 0.524 0 0.201 0.450 Table E-6 Microcosm Iron data (ppm) data from Experiment 1, November 17 to December 9, 2002. Note: Microcosm variables (1. Control, 2. DI water, 3. Oxic and 4. Molybdate ions) Microcosm 18-NOV-02 25-NOV-02 02-Dec-02 09-Dec-02 09-Dec-02 Dis 1 0.108 0.213 0.128 " 224 0.084 2 0.624 0.464 0.129 0.804 0.176 3 0.448 0.476 0.184 0.714 0.327 4 1.654 1.353 0.263 1.784 1.092 Table E-7 Mercury concentrations of Bumaby lake sediment used in Microcosm #1 analysis, November 1, 2002 Description Concentration (wg/kg) % Solids Adjusted concentration (wg/kg) Microcosm Sediment 21 9.97 210.63 99 APPENDIX F Correlations for 1973-2003 stream sediment in the Brunette Watershed Table F-l Spearman's rho Correlations with Bonferroni Correction- 1973 Stream Sediment in the Brunette Watershed Fe Hg Mn Pb Cu Cr Ni Zn 1.000 35 .162 1.000 33 33 .347 .350 1.000 35 33 35 .188 .664(**) .127 1.000 35 33 35 35 .281 .821(**) .038 .850(**) 1.000 29 27 29 29 29 .288 .221 -.115 .312 .377 1.000 28 27 28 28 28 28 .483 .657(**) .212 .772(**) .815(**) .500 1.000 29 27 29 29 29 28 29 .362 774(**) .178 .843(**) .894C) .320 .820(") 1.000 29 27 29 29 29 28 29 29 .209 -.105 .069 -.087 -.042 -.168 -.088 -.041 33 32 33 33 28 28 28 28 OM% Fe Hg Mn Pb Cu Cr Ni Zn OM% Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N 1.000 34 Correlation is significant at the 0.005 level (2-tailed). " Correlation is significant at the 0.001 level (2-tailed). 100 Table F-2 Spearman's rho Correlations with Bonferroni Correction- 1989 stream sediment data in the Brunette Watershed Fe Hg Mn Pb Cu Cr Ni Zn Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Fe Hg Mn Pb Cu Cr 1.000 29 .190 1.000 29 29 .450 .216 1.000 29 29 29 .263 .901(**) .264 1.000 29 29 29 29 .150 .894(**) .133 .902(**) 1.000 29 29 29 29 29 •557(*) .654(**) .167 .630(**) .571(**) 1.000 29 29 29 29 29 29 .362 .750(") .262 .691 (**) .596(**) .725(**) 29 29 29 29 29 29 .490 .810(**) .380 825(**) .818(**) .541(**) 29 29 29 29 29 29 Ni Zn 1.000 29 .641(**) 29 1.000 29 Correlation is significant at the 0.005 level (2-tailed). ' Correlation is significant at the 0.001 level (2-tailed). 101 Appendix F-3 Table F-3 Spearman's rho Correlations with Bonferroni Correction- 1993 stream sediment in the Brunette Watershed Fe Hg Mn Pb Cu Cr Ni Zn OM% Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Correlation Coefficient N Fe Hg Mn Pb Cu Cr Ni Zn 1.000 36 -.012 1.000 35 35 .427 -.080 1.000 36 35 36 .134 .640(**) .224 1.000 36 35 36 36 .288 .502 .052 .848(**) 1.000 30 29 30 30 31 .414(*) .445 -.027 .619(**) .706(**) 1.000 30 29 30 30 31 31 .496(*) .546(*) -.076 .531C) .565(**) .780(**) 1.000 30 29 30 30 31 31 31 .485 .345 .293 .701(**) .830(**) .631(**) .608(**) 1.000 30 29 30 30 31 31 31 31 .302 .285 .343 .299 .261 .147 .227 .291 36 35 36 36 30 30 30 30 OM% 1.000 36 " Correlation is significant at the 0.001 level (2-tailed). Correlation is significant at the 0.005 level (2-tailed). 102 Appendix F-4 Table F-4 Spearman's rho Correlations with Bonferroni Correction- 2003 Stream Sediment in the Brunette Watershed Fe Hg Mn Pb Cu Cr Ni Zn o% Fe Correlation 1.000 Coefficient N 36 Hg Correlation Coefficient N .041 36 1.000 36 Mn Correlation .398 36 .129 36 1.000 36 Coefficient N Pb Correlation Coefficient N .245 36 .304 36 .353 36 1.000 36 Cu Correlation Coefficient .555(") .200 .215 .930(") 1.000 N 30 30 30 30 30 Cr Correlation Coefficient .748(") .103 .167 .635(**) .800(") 1.000 N 30 30 30 30 30 30 Ni Correlation Coefficient .715(**) -.030 .189 .493(**) .667(**) .825(**) 1.000 N 30 30 30 30 30 30 30 Zn Correlation .712(") .135 Coefficient 5140 864(") .890(**) .685(**) .553(*) 1.000 N 30 30 30 30 30 30 30 30 Om Correlation Coefficient .332 .205 ,639(") 663(") .574(**) .307 .306 .703(") 1.000 N 36 36 36 36 30 30 30 30 36 * Correlation is significant at the 0.005 level (2-tailed). ** Correlation is significant at the 0.001 level (2-tailed). 103 APPENDIX G Correlations for Burnaby Lake composite core sediments Table G-l Spearman's rho Correlations with Bonferroni Correction- Burnaby Lake composite core sediments (Enkon 2002) Hg Mn Fe Pb TOC s Cu Ni Zn Hg Correlation 1.000 Coefficient N 15 Mn Correlation Coefficient N .533 15 1.000 15 Fe Correlation Coefficient N .454 15 ,832<**) 15 1.000 15 Pb Correlation Coefficient N .876(**) 15 .463 15 .461 15 1.000 15 TOC Correlation Coefficient .634 .197 .020 .448 1.000 N 15 15 15 15 15 s Correlation Coefficient .467 .027 .041 .229 .624 1.000 N 15 15 15 15 15 15 Cu Correlation Coefficient ,788(*») .668 .664 ,835(**) .159 .080 1.000 N 15 15 15 15 15 15 15 Nt Correlation Coefficient ,652(**) .576 .420 .571 .091 .163 .843(*») 1.000 N 15 15 15 15 15 15 15 15 Zn Correlation Coefficient 862(*») .496 .525 .976(**) .372 .181 .886(**) .626 1.000 N 15 15 15 15 15 15 15 15 15 * Correlation is significant at the 0.005 level (2-tailed). ** Correlation is significant at the 0.001 level (2-tailed). 104 APPENDIX H Correlations for Microcosm #1 data Table H-l Spearman's rho Correlations with Bonferroni Correction for Microcosm #1 data 1 PH conductivity D.O. DOC Hg Fe pH Correlation 1.000 Coefficient Sig. (2-tailed) N 16 Conductivity Correlation Coefficient Sig. (2-tailed) N .346 .189 16 1.000 16 D.O. Correlation Coefficient Sig. (2-tailed) N -.649(*) .006 16 -.059 .828 16 1.000 16 DOC Correlation Coefficient Sig. (2-tailed) •754<*) .031 .345 .403 -.638 .089 1.000 N 8 8 8 8 Hg Correlation Coefficient -.500 -.265 .154 .651 1.000 Sig. (2-tailed) .049 .322 .570 .081 N 16 16 16 8 16 Fe Correlation Coefficient .539 .158 -.221 .533 .000 1.000 Sig. (2-tailed) .031 .560 .411 .174 1.000 N 16 16 16 8 16 16 ** Correlation is significant at the 0.008 level (2-tailed). * Correlation is significant at the 0.001 level (2-tailed). 105 APPENDIX I Correlations for the February 28, 1997 stormwater event in the Brunette Watershed Table 1-1 Spearman's rho Correlations with Bonferroni Correction for the February 28, 1997 on Still Creek stormwater event (Sekela et al. 1998) Cr Cu Hg Fe Mn Ni Pb Zn Cr Correlation 1.000 Coefficient Sig. (2-tailed) Cu Correlation Coefficient Sig. (2-tailed) .257 .623 1.000 Hg Correlation Coefficient Sig. (2-tailed) .600 .208 .771 .072 1.000 Fe Correlation Coefficient Sig. (2-tailed) .143 .787 .943(*) .005 .829 .042 1.000 Mn Correlation Coefficient Sig. (2-tailed) .086 .872 -.714 .111 -.143 .787 -.543 .266 1.000 Ni Correlation Coefficient .714 -.086 .371 -.143 .543 1.000 Sig. (2-tailed) .111 .872 .468 .787 .266 Pb Correlation Coefficient .086 .886 .543 .829 -.829 -.314 1.000 Sig. (2-tailed) .872 .019 .266 .042 .042 .544 Zn Correlation Coefficient .029 .943(*) .600 .886 -.771 -.200 .943(*) 1.000 Sig. (2-tailed) .957 .005 .208 .019 .072 .704 .005 ** Correlation is significant at the 0.001 level (2-tailed). * Correlation is significant at the 0.006 level (2-tailed). 106 |Table 1-2 Spearman's rho Correlations with Bonferroni Correction for the February 28, 1997 on the Brunette River stormwater event (Sekela et al. 1998) Cr Cu Hg Fe Mn Ni Pb Zn Cr Correlation 1.000 Coefficient Sig. (2-tailed) Cu Correlation -.841 .036 1.000 Coefficient Sig. (2-tailed) Hg Correlation Coefficient Sig. (2-tailed) .464 .354 -.515 .296 1.000 Fe Correlation -.486 .329 .580 .228 -.725 .103 1.000 Coefficient Sig. (2-tailed) Mn Correlation -.429 .397 .493 .321 -.870 .024 .943(*) .005 1.000 Coefficient Sig. (2-tailed) Ni Correlation -.667 .647 -.250 -.116 -.029 Coefficient 1.000 Sig. (2-tailed) .148 .165 .633 .827 .957 Pb Correlation -.429 .638 -.783 .943(*) Coefficient .886 -.058 1.000 Sig. (2-tailed) .397 .173 .066 .005 .019 .913 Zn Correlation .986(**) Coefficient -.771 -.551 .600 .543 .638 .657 1.000 Sig. (2-tailed) .072 .000 .257 .208 .266 .173 .156 ** Correlation is significant at the 0.001 level (2-tailed). * Correlation is significant at the 0.006 level (2-tailed). 107 APPENDIX J Quality control data for mercury in sediment Table J-lQuality control data for mercury in sediment, analyzed on a Lumex AA. Results in ug/kg, dry wieght. Environmental Resource Associates: Reference Sample Catalog #540 Lot # D035-540. QC Data Weight Cone. % (ppm) (mg) (ppm) Recovery era-24.6 18.6 26.0 105.8% era 24.6 35.2 21.9 89.0% era 24.6 31.6 20.5 83.5% era 24.6 20.9 25.2 102.3% era 24.6 33.3 23.9 97.2% era 24.6 4.7 29.6 120.3% era 24.6 31.0 23.0 93.5% Ave 23.5 95.6% std dev 3.0 conf@95% 1.86 check-30 100 26.3 87.7% check-30 100 28.3 94.3% check-30 100 24.6 82.0% check-50 100 57.4 114.8% check-50 100 45.7 91.4% check-50 100 52.6 105.2% Ave 95.9% Blank 1 -2.0 Blank 1 -1.3 Blank 1 -3.0 Blank 1 2.9 Blank 1 0.8 Blank 1 -0.2 Blank 1 -0.7 Ave -0.5 std dev 1.9 108 APPENDIX K Wilcoxon Paired Sample Signed Rank Test for mercury stream sediment data in the Brunette Watershed. Table K-l Wilcoxon Paired Sample Signed Rank Test for 1973, 1989, 1996 and 2003 mercury stream sediment data in the Brunette Watershed N Mean Rank Sum of Ranks 1989-1973 Negative Ranks 0(a) .00 .00 Positive Ranks . 27(b) 14.00 378.00 Ties 0(c) Total 27 1993-1973 Negative Ranks 0(d) .00 .00 Positive Ranks 28(e) 14.50 406.00 Ties ' 0(f) Total 28 2003-1973 Negative Ranks 5(g) 10.80 54.00 Positive Ranks 23(h) 15.30 352.00 Ties 0(i) Total 28 1993-1989 Negative Ranks 12(1) 15.08 181.00 Positive Ranks 17(k) 14.94 254.00 Ties 0(l) Total 29 2003 -1989 Negative Ranks 22(m) 16.27 358.00 Positive Ranks 7(n) 11.00 77.00 Ties 0(o) Total 29 2003 - 1993 Negative Ranks 24(p) 16.71 401.00 Positive Ranks 6(q) 10.67 64.00 Ties 0(r) Total 30 a 1989 < 1973, b 1989 > 1973,c 1989 = 1973, d 1993 < 1973, e 1993 > 1973, f 1993 = 1973, g 2003 < 1973, h 2003 > 1973, i 2003 = 1973, j 1993 <1989, k 1993 >1989,1 1993 =1989, m 2003 < 1989, n 2003 > 1989, o 2003 = 1989, p 2003 < 1993, q 2003 > 1993, r 2003 = 1993 109 Table K-2 Test Statistics for data from 1973-2003 1989-1973 1993- 1973 2003- 1973 1993-1989 2003 - 1989 2003 - 1993 z -4.541(a) -4.623(a) -3.393(a) -.789(a) -3.038(b) -3.466(b) Asymp. Sig. (2-tailed) .000 .000 .001 .430 .002 .001 a Based on negative ranks, b Based on positive ranks, c Wilcoxon Signed Ranks Test 110 APPENDIX L Mercury concentrations in stream sediment adjusted for a 66.8% loss caused by drying the sediment Table L-l Mercury concentrations in stream sediment adjusted for a 66.8% loss caused by drying the sediment (Mg/kg, dry weight). Stations 1973 Hg 1989 Hg 1993 Hg 2003 Hg (yg/kg) (ug/kg) (wg/kg) (ug/kg) 1 73 200* 220* 121 2 67 183* 220* 44 3 87 133 229* 109 4 18 75 85 34 6 18 . 133 95 172 7 32 133 142 131 8 23 58 85 99 9 33 75 192* 74 10 20 150 132 94 11 17 NA 172 97 13 45 67 75 18 14 50 58 83 55 15 15 67 25 95 16 22 83 25 132 17 23 42 100 143 19 30 158 102 169 20 37 175* 115 47 21 30 192* 158 55 24 88 584** 170 166 25 48 92 587* 41 26 25 108 107 104 27 37 117 113 81 29 122 150 257* 185* 30 168 267* 202* 86 31 100 150 249* 115 32 62 609** 152 77 33 57 692** 1451** 119 34 NA 334* 357* 30 35 NA 200* 229* 54 37 NA 292* NA 170 Mean 50 192* 211* 97 * indicates concentrations higher than Environment Canada Intenn Sediment Quality Guideline of 174 wg/kg ** indicates concentrations higher than Environment Canada Probable Effect Level of 486 wg/kg 111 

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