Metals in Society and in the Environment: A Critical Review of Current Knowledge on Fluxes, Speciation, Bioavailability and Risk for Adverse Effects of ... Nickel and Zinc (Environmental Pollution)

Metals in Society and in the Environment

ENVIRONMENTAL POLLUTION VOLUME 8

Editors Brian J. Alloway, Department of Soil Science, The University of Reading, U.K. Jack T. Trevors, Department of Environmental Biology, University of Guelph, Ontario, Canada

Editorial Board T. Anderson, The Institute of Environmental and Human Health, Texas Tech University, Lubbock, U.S.A. T.H. Christensen, Department of Environmental Science and Engineering, Danish Technical University, Lyngby, Denmark I. Colbeck, Institute for Environmental Research, Department of Biological Sciences, University of Essex, Colchester, U.K. K.C. Jones, Institute of Environmental and Natural Sciences, Lancaster University, U.K. S. Parry, T.H. Huxley School of Environment, Earth Sciences and Engineering, Imperial College at Silwood Park, Ascot, Berks, U.K. W. Salomons, GKSS Research Center, Geesthacht, Germany

The titles published in this series are listed at the end of this volume.

Metals in Society and in the Environment A Critical Review of Current Knowledge on Fluxes, Speciation, Bioavailability and Risk for Adverse Effects of Copper, Chromium, Nickel and Zinc by

Lars Landner AF-Environmental Research Group (AF-MFG), Stockholm, Sweden

and Rudolf Reuther enas Environmental Assessments, Albertshofen, Germany

KLUWER ACADEMIC PUBLISHERS NEW YORK, BOSTON, DORDRECHT, LONDON, MOSCOW

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Table of Contents Figures ............................................................................................ xi Tables ................................................................................................xiii Acknowledgements ............................................................................ xx 0 0.1 0.2

0.3.2 0.3.3 0.4

EXECUTIVE SUMMARY AND CONCLUSIONS........ 1 Introduction .......................................................................... 1 Metal Fluxes from Society to the Environment and between Environmental Media............................................. 3 The European Copper Cycle in the Mid-1990s.................... 4 Metal Fluxes from Mining Waste – Falun Copper Mine ..... 5 Urban Metal Flows – the Case of Stockholm....................... 6 Critical Steps in Metal Fluxes from Cities to the Environment ......................................................................... 7 Speciation, Bioavailability and Effects of Trace Metals in the Environment ................................................................... 8 In the Water Column - BLM as a Tool for Prediction of Toxicity ................................................................................ 9 In Aquatic Sediments – AVS as a Tool for Prediction....... 10 In Soils – Laboratory versus Field Tests ............................ 11 General Conclusions........................................................... 12

1 1.1 1.2 1.3 1.4

PURPOSE OF THIS REVIEW....................................... 15 Background and justification.............................................. 15 The need and how to meet it .............................................. 17 Target groups for the updated report.................................. 18 Implementation of the work ............................................... 18

2

GLOBAL EXTRACTION, PRODUCTION AND CONSUMPTION.............................................................. 21 Copper ................................................................................ 21 Nickel ................................................................................. 22 Zinc..................................................................................... 23

0.2.1 0.2.2 0.2.3 0.2.4 0.3 0.3.1

2.1 2.2 2.3

vi 3

METAL CYCLES IN DEFINED GEOGRAPHICAL AREAS: EUROPE, THE NETHERLANDS AND STOCKHOLM ................................................................. 25 3.1 Example 1: The European Copper Cycle .......................... 25 3.1.1 Introduction ........................................................................ 26 3.1.2 Selection of boundaries of the system to be studied .......... 28 3.1.3 Some definitions and characterisation of the technical components......................................................................... 29 3.1.3.1. Production (mining, milling, concentration, smelting, refining) .............................................................................. 29 3.1.3.2. Fabrication, manufacturing and use ................................... 30 3.1.4 Waste management subsystem........................................... 33 3.1.5 Summary of stocks and flows of copper in European society, in 1994................................................................... 37 3.2 Example 2: Dynamic Modelling of Metal Flows in the Netherlands; Cu and Zn...................................................... 40 3.2.1 Models used........................................................................ 40 3.2.2 Summary of main results.................................................... 42 3.2.3 Critical review of the Dutch calculations ........................... 46 3.3 Example 3: Urban Metal Flows – Stockholm; Cr, Cu, Ni and Zn .............................................................. 48 3.3.1 New aspects of studies on urban metal flows..................... 50 3.3.2 Stock of metals in Stockholm............................................. 51 3.3.3 Outflows of metals from existing stocks to the solid waste compartment............................................................. 53 3.3.4 Outflows via other routes, e.g. diffuse emissions from goods .................................................................................. 53 3.3.5 Metal fluxes to and from sewage treatment plants in Stockholm........................................................................... 55 3.3.6 Constraints in metal cycling to arable land with sewage sludge.................................................................................. 59 3.3.7 Metal fluxes with groundwater in Stockholm .................... 59 3.3.8 Metal accumulation and metal pools in urban soils in Stockholm........................................................................... 61 3.3.9 Metal fluxes to sediments of lakes and coastal areas in Stockholm........................................................................... 65

vii 4

4.1

4.1.1 4.1.2 4.1.3 4.1.4 4.1.5 4.2

4.2.1 4.2.2 4.2.3

4.2.4 4.2.5 4.3 4.3.1 4.3.2 4.3.3 4.3.4 4.3.5 4.3.5.1 4.3.5.2 4.3.5.3

CRITICAL STEPS IN METAL FLUXES FROM SOCIETY TO THE ENVIRONMENT – SOME CASE STUDIES .................................................. 71 Case Study 1: Corrosion and runoff of metals from roofing materials made of copper, galvanized steel or stainless steel (Cu, Zn, Cr and Ni)...................................... 72 Definitions, background and experimental approaches ..... 73 Some principal results ........................................................ 75 Releases and fluxes of copper ............................................ 76 Releases and flows of zinc ................................................. 80 Releases and flows of chromium and nickel ...................... 84 Case Study 2: Relative importance of the traffic sector for metal fluxes from the urban environment to aquatic ecosystems.......................................................................... 86 Difficulties to quantify the contribution of street traffic to trace metal fluxes ........................................................... 87 Bioavailability to aquatic organisms of traffic-emitted metals.................................................................................. 88 Level of contamination with bioavailable trace metals in the waterways of central Stockholm, compared to other waters.................................................................................. 92 Possible over-interpretation of bioaccumulation data – a critical review .................................................................. 94 Which conclusions from the study are justified ? .............. 96 Case Study 3: Metal fluxes from households to STPs, sludge and agricultural soils ............................................... 98 Origin of trace metals in STPs and in sewage sludge ........ 99 Assessment of the causes of copper release from tap water pipes........................................................................ 101 Use of sewage sludge as a fertiliser in agriculture ........... 105 Permitted trace metal loads to agricultural soils .............. 106 Sustainable trace metal loadings to agricultural soils ...... 108 Trace metal deficiency symptoms and how to correct them .................................................................................. 109 Application of sewage sludge to soils – risk of metal toxicity to soil ecosystems................................................ 110 Long-term field studies – effects of sewage sludge application to soils............................................................ 110

viii 4.3.5.4 4.4 4.4.1 4.4.2 4.4.3 4.4.4 4.5

5

5.1 5.1.1 5.1.2 5.1.3

5.2 5.2.1 5.2.2 5.2.3 5.3 5.4 5.4.1 5.4.2 5.4.2.1 5.4.2.2 5.4.2.3 5.4.2.4 5.4.3

Conclusions regarding sustainable trace metal loadings to agricultural soils ........................................................... 117 Case Study 4: Metal fluxes from mine waste to rivers – Falun Copper Mine........................................................... 120 Background and definition of the case to be discussed.... 121 Brief description of the level of pollution with metals in water and sediments of receiving rivers and lakes ........... 124 Biological responses to the enhanced metal concentrations................................................................... 127 Some conclusions from the Falun studies ........................ 130 Summing up: Fluxes of Cr, Cu, Ni and Zn from Society to the Environment .............................................. 131 SPECIATION, MOBILITY AND BIOAVAILABILITY OF METALS IN THE ENVIRONMENT ........................................................... 139 Introduction ...................................................................... 139 General considerations ..................................................... 139 Definitions ........................................................................ 141 Fundamental properties of the selected metals................. 142 Chromium......................................................................... 144 Copper .............................................................................. 145 Nickel ............................................................................... 146 Zinc................................................................................... 147 In surface waters............................................................... 149 Metal speciation in the aqueous (dissolved) phase .......... 151 Adsorption versus bioavailability..................................... 156 Competition between aqueous and solid phases .............. 158 In groundwaters................................................................ 160 In aquatic sediments ......................................................... 163 Introduction ...................................................................... 163 Today’s knowledge on metal speciation in sediment/water systems.................................................... 164 General overview ............................................................. 165 Total concentration approach ........................................... 166 Partly theoretical approaches to metal speciation ............ 167 More empirical approaches to metal speciation (chemical extraction)........................................................ 168 The Acid-Volatile Sulphides (AVS) concept................... 170

ix 5.4.3.1 5.4.3.2 5.4.3.3 5.4.3.4 5.4.4 5.4.5 5.4.6 5.4.7 5.4.7.1 5.4.7.2 5.4.8 5.4.8.1 5.4.8.2 5.4.9 5.5 5.5.1 5.5.2 5.5.3 5.5.4 5.5.5 5.5.6 5.5.7 5.6 5.7

6 6.1 6.2 6.3 7 7.1 7.1.1 7.1.1.1

Development and application........................................... 172 Refinement of the “AVS hypothesis” .............................. 181 Operational drawbacks of SEM/AVS-based approaches. 187 New empirical evidence ................................................... 192 Chemical extraction and mobility .................................... 197 New spectroscopic approaches......................................... 201 Bioturbation, resuspension and bioirrigation ................... 206 Metal-ligand interactions.................................................. 214 Free ion activity model (FIAM) ....................................... 215 Surface complexation ....................................................... 218 Speciation-bioavailability interactions in sediment-ingesting biota................................................... 222 Absorption efficiency (AE) .............................................. 223 Gut juice extraction .......................................................... 227 Redox effects.................................................................... 230 In soils .............................................................................. 232 Introduction ...................................................................... 232 Metal adsorption and partitioning .................................... 233 Chemical extraction and plant uptake .............................. 237 Surface reactions .............................................................. 246 Redox effects.................................................................... 250 Aging and weathering ...................................................... 254 Sludge application and contaminated soils ...................... 258 In biota.............................................................................. 265 A proposal for “natural” or “preindustrial” regional background levels of metals in the sediment in waters surrounding Stockholm .................................................... 271 BIOTIC LIGAND MODELS ........................................ 275 Need for improved models to assess bioavailable fraction of metals.............................................................. 276 Development of Biotic Ligand Models ............................ 279 Application of BLMs........................................................ 284 TOXIC AND OTHER ADVERSE BIOLOGICAL EFFECTS OF TRACE METALS................................. 289 Toxicity to aquatic organisms in the water column ......... 290 Copper .............................................................................. 292 Sensitivity to copper of different aquatic organisms........ 292

x 7.1.1.2 7.1.2 7.1.3 7.1.3.1 7.1.3.2 7.2 7.2.1 7.2.2 7.2.3 7.2.3.1 7.2.3.2 7.2.3.3 7.2.3.4 7.2.3.5 7.3 7.3.1 7.3.2 7.3.2.1 7.3.2.2 7.3.3 7.3.4 7.4 7.4.1 7.4.2 7.4.3

Toxicity of copper estimated by means of BLMs ............ 297 Nickel ............................................................................... 302 Zinc................................................................................... 303 Sensitivity to zinc of different aquatic organisms ............ 303 Toxicity of zinc estimated by means of BLMs ................ 304 Toxicity to sediment-dwelling organisms ........................ 307 Some general considerations ............................................ 309 Field validation of the SEM/AVS model for zinc............ 311 Metal release and toxicity of sediments from the Stockholm area ................................................................. 314 Background and experimental design .............................. 314 Experimental results: transfer of metals from sediments to water and organisms.................................... 316 Experimental results: toxicity to amphipods .................... 317 Interpretation of results .................................................... 318 Some remarks on experimental design in sediment research............................................................................. 320 Toxicity to soil-dwelling organisms and to higher plants ..................................................................... 321 Some general considerations ............................................ 323 Summary of toxicity thresholds for soil organisms and plants.......................................................................... 326 Copper .............................................................................. 326 Zinc................................................................................... 328 Toxicity of trace metals in contaminated urban soils....... 330 Systematic assessment of zinc toxicity in laboratory spiked soils and in gradually contaminated field soils ..... 331 Essentiality, regulation and deficiency............................. 333 Some useful definitions .................................................... 334 Examples of copper essentiality and copper tolerance..... 336 Examples of zinc essentiality and zinc tolerance ............. 338

REFERENCES ............................................................................... 341 Abbreviations.................................................................................. 379 Index

......................................................................................... 385

xi

Figures Figure 2.1. Development of global production and consumption of refined nickel (in Mt/year) in the period 1999-2003. Figures for 2003 projected. After SGU, 2002; 2003. Figure 2.2. Development of global production and consumption of refined zinc (in Mt/year) in the period 1998-2003. Figures for 2003 projected. After SGU, 2002; 2003. Figure 3.1 The copper cycle for Europe in 1994. All units measured in kt/year. Reprinted from Spatari et al., 2002, with permission from Elsevier Figure 4.1 Results of equilibrium calculations for dissolved copper species, when all the thermodynamically stable solids are considered. Reprinted with permission from Linder and Taxén, 2002 Figure 4.2. Map showing the main water courses in the Falun area, especially the receiving waters of the mine waste: the Gruvbäcken Creek, River Faluån, Lake Tisken and Lake Runn, which empties into the great River Dalälven. Personal Communication, Lindeström, 2002 Figure 4.3. Average biomass of phytoplankton in August in several lakes in the River Dalälven catchments area in the period 1990-2000 as a function of the nutrient (phosphorus) status of the lakes. Biomasses expressed in mm³/l. Reprinted with permission from Lindeström, 2003. Figure 4.4. Concentrations of copper and zinc in water (curve) and in liver tissue of perch (bars) in several lakes in the River Dalälven drainage basin. Concentrations in water are expressed as µg/l and in liver tissue as µg/g DM. Reprinted with permission from Lindeström, 2003. Figure 5.1. Schematic representation of the role of complexation reactions in the medium of a metal-uptaking organism. Reprinted with permission from Leuuwen, 1999 (American Chemical Society) Figure 5.2. Cross section through a DGT device deployed in a pot of soil. For illustrative purposes, the DGT device is shown proportionally larger than the pot. Reprinted with permission from Zhang et al., 2001 (American Chemical Society)

xii Figure 5.3. Schematic representation of the dynamic interactions between free, labile and nonlabile metal pools in soil solution and their uptake by plant roots. Reprinted with permission from McBride and Martinez, 2000 (American Chemical Society) Figure 6.1. Conceptual diagram of the Biotic Ligand Model (BLM) showing inorganic and organic complexation in the water and interaction of metals and cations on the biotic ligand (BL). DOC = dissolved organic carbon. Modified after Pagenkopf’s (1983) original GSIM model.

xiii

Tables Table 3.1. Principal uses of copper in the world, in 1990 (Joseph, 1999, Graedel et al., 2002). Table 3.2. Example of stock buildup and decline for copper building wire (see text). Table 3.3. Solid waste generation and copper content in the waste for STAFEurope, in 1994 (after Bertram et al., 2002). Table 3.4. Origins of the immission of copper and zinc in surface waters in the Netherlands. S.S. stands for a steady-state scenario. After van der Voet and van Oers, 2000. Table 3.5. Origins of the immision of copper and zinc in agricultural soils in the Netherlands. S.S. stands for a steady-state scenario. After van der Voet and van Oers, 2000. Table 3.6. Origins of copper and zinc in the waste management system in the Netherlands. S.S. stands for a steady-state scenario. After van der Voet and van Oers, 2000. Table 3.7. Total emissions of metals to the Dutch environment in 1990 and at a steady-state scenario, as well as the main receiving compartment, according to data in van der Voet, Guinée and de Haes, 2000. Table 3.8. Stock of metals (ktonnes) in the city of Stockholm, the annual amounts of metals in inflows and outflows – with solid waste and via other routes (ktonnes/y) – and the percentages of metals in stock that are protected and exposed to soil, water and air, respectively. After Bergbäck et al., 2001; Sörme et al., 2001a. Table 3.9. Calculated metal emissions (kg/y) from the major goods emission sources in Stockholm, 1995. After Bergbäck et al., 2001 and Sörme et al., 2001b. Table 3.10. Flows of metals in Stockholm: the influx of metals to the STPs, the effluxes via sludge and treated sewage, including storm water and groundwater (emitted to surface waters, A), fluxes through the Stockholm Stream (B) and calculated fractions of metals emitted compared to total

xiv transports in the recipient and compared to total emissions from the metal stock in Stockholm, respectively. (Data from Bergbäck et al., 2001). Table 3.11. Contribution of metals from different sources (%) to the STP of Henriksdal in 1999. After Sörme and Lagerkvist, 2002. Table 3.12. Average emissions in the year 1999 (kg/year) of the four metals, copper, chromium, nickel and zinc, from various sources in Stockholm, within the catchment area of the STP of Henriksdal. Estimated according to methods described by Sörme and Lagerkvist, 2002. Table 3.13. Chromium, copper, nickel and zinc in the groundwater of Stockholm. Median and mean concentrations, degrees of elevation above the levels in groundwater in forest ecosystems (nation-wide), total amounts stored in the groundwater, estimates of total fluxes and direct contributions to Lake Mälaren and the Baltic Sea, the latter expressed both as percent of total transport from Lake Mälaren to the Baltic Sea and as percent of the total discharge to water from the city of Stockholm. After Aastrup and Thunholm, 2001. Table 3.14. Concentrations of chromium, copper, nickel and zinc (as mean values of total metal in mg/kg dry weight) in various soil types in the city of Stockholm and in arable soils in the Stockholm region. After Linde et al., 2001 and Eriksson et al., 1997 and 1999. Table 3.15. Calculated average pools of copper, lead and zinc (g/m²) in the top 30 cm of soils in the city centre of Stockholm as well as in parks outside the city centre. Data are also given on total pools, together with estimates of amounts of metals accumulated due to local emissions (given in tonnes). After Linde et al., 2001. Table 3.16. Estimates of total metal deposition to sediments in Lake Mälaren and in the Baltic Sea archipelago close to the city of Stockholm, and of the sediment metal loads originating from Stockholm (max and min), as well as the average metal flux from Lake Mälaren to the Baltic Sea in the period 1995-1997. All fluxes in t/y. After Lindström et al., 2001. Table 4.1. Annual zinc runoff rates from five major groups of zinccontaining commercial building materials used in Sweden, as well as individual values for each material, annual rates given in g/m². After Karlén et al., 2001.

xv Table 4.2. Annual release rates (mg/m²) of chromium and nickel from 304 and 316 stainless steels, exposed for four years to the urban atmosphere in Stockholm. After Odnevall Wallinder et al. (2003). Table 4.3. Total concentrations of metals (µg/l) in the surface layer of water in Lake Mälaren, in Saltsjön and in two smaller lakes in Stockholm during the fall of 2001. After Lithner et al., 2003. Table 4.4. Concentrations of some metals (µg/g DM )in soft tissues of Dreissena polymorpha after exposure for 6 weeks on stones in baskets placed at 8 different sites in Lake Mälaren and one site in Saltsjön during the fall (August-October) of 2001. Figures in the table are ranges of mean values for different sites. After Lithner et al., 2003. Table 4.5. Concentrations of some metals (µg/g DM )in soft tissues of Dreissena polymorpha after exposure for 6 weeks in central Stockholm compared to metal concentration in mussels caught in some other lakes and rivers. Ref. data compiled by Lithner et al., 2003. Table 4.6. Permitted trace metal loads (kg/ha per year) in the EU – at present and proposed for the future – as well as in some EU Member States and in some other countries. After Landner et al., 2000; Delbeke and Landner, 2000. Table 4.7. Limit values for some trace metals in sewage sludge (mg/kg DM, or when indicated, expressed as g/kg P) for use in agriculture. Values are from the EU – at present and proposed for the future – as well as from some EU Member States and from some other countries. After Landner et al., 2000; Delbeke and Landner, 2000. Table 4.8. Experimental scheme for studies of the long-term consequences of sewage sludge applications on agricultural land in southern Sweden. After Andersson, 2000. Table 4.9. Ranges of metal concentrations (mg/kg DM) in the sewage sludges used in the field experiments at Igelösa and Petersborg. After Andersson, 2000. Table 4.10. Trace metal total concentrations (mg/kg DM) in the topsoil at Igelösa (IG) and Pertersborg(PE) in 1981 and at later stages just before a new sludge application. After Andersson and Nilsson, 1999; Andersson, 2000.

xvi Table 4.11. Trace metal total concentrations (mg/kg DM) in the sub-soil (30-60 cm) at Igelösa (IG) and Pertersborg(PE) in 1999. After Andersson, 2000. Table 4.12. Metal contents (mg/kg DM) in the crops harvested in 1998 and 1999 at the two farms Igelösa and Petersborg, after several years of sewage sludge application. After Andersson, 2000. Table 4.13. Metal concentrations in the mine water pumped from the Falun Copper Mine and in the receiving rivers and lakes prior to 1978 and averages for the 1990s. All concentrations are total concentrations in the water, expressed as µg/l. After Lindeström, 2003. Table 4.14. Concentrations of some metals in superficial sediments in Lakes Tisken and Runn immediately downstream of the Falun Copper Mine and median value for small lakes in the catchment of River Dalälven. Concentrations in µg/g DM. After Lindeström, 2003. Table 4.15. Macroscopic benthic fauna in Lake Runn and similar oligotrophic lakes in the region investigated in 1996. Results are shown separately for shallow and deep bottoms (above and below the thermocline). After Lindeström, 2003. Table 4.16. Overview of copper and zinc concentrations in sediments collected in sediment traps and in superficial bottom sediment from three sites in the inner waterways of Stockholm. The table also displays calculated concentrations of copper and zinc in freshly settling material. For comparison, estimated regional background concentrations in sediments and copper and zinc levels in transplanted zebra mussels are given. All concentrations expressed as µg/g DM. After Broman et al., 2001; Östlund et al., 1998; Lithner et al., 2003. Table 5.1. Overview of currently used speciation approaches (modified after Turner and Whitfield, 1982) Table 5.2. Percentage of Swedish and Norwegian lakes below the lowest biological risk levels given as total concentrations in µg/l according to Norwegian and Swedish criteria (from Lydersen et al., 2002) Table 5.3. Aqueous and surface complexation reactions relevant for chromium speciation (from Nikoloaidis et al., 1999)

xvii Table 5.4. First-order oxidation rate constants and resulting half-lives for metal sulfides in natural river water (from Rozan et al., 1999) Table 5.5. Examples of sequential extraction procedures for trace metals in sediments (from Reuther, 1999). Table 5.6. Effect of surface area on extraction efficiency (from Cooper and Morse, 1998) Table 5.7. Extraction efficiency (from Cooper and Morse, 1998) Table 5.8. Local structure of Zn in reference compounds, determined by multishell fit of Zn K-edge EXAFS analysis (from Scheinost et al., 2002) Table 5.9. Reactivity of added solid phase metal constituents (M) in Iron Cove sedimenta and final metal sulphide formation upon sediment resuspension in seawater (from Simpson et al., 2000a) Table 5.10. Free metal ion activities as percentage of total dissolved concentration at equilibrium, and 7 and 21 days after introducing test organisms (Limnodrillus spp.) (from Vink, 2002) Table 5.11. Example of Cu released by 1 N HCl, gut fluids inArenicola marina, Parastichopus californicus, Cucumaria frondosa and sea water from harbour (BBH and PLH) and estuarine sediments (BIW), in comparison to total sedimentary Cu and acid-volatile sulphidea (AVS) (from Chen and Mayer, 1999) Table 5.12. Total and soluble Cu and Zn contents (µg/g dw) in two Swiss soils treated with manure, a Zn-containing fungicide (Propineb with 22.6% of Zn) and Cu salt (50% Cu) (from Aldrich et al., 2002) Table 5.13. Multiple and single regression equations between plant concentrations (alfalfa, wheat) of Co, Cu, Pb and Ni and metal concentrations in particular soil fractions (from Qian et al., 1996) Table 5.14. Influence of water depth and redox status on Zn speciation in wetland soils (from Bostick et al., 2001) Table 5.15. Comparison of metal concentrations in soils of two field experiments in Braunschweig/Germany that received 100 or 300 m3 year-1 of metal-contaminated sewage sludge for about 9 years (Germany), with metal

xviii concentrations in soils from them Woburn Market Garden Experiment/UK giving 50% inhibition of nitrogenase activity by cyanobacteria, in relation to German, UK and CEC metal limits for soils receiving sewage sludge (mg/kg dw) (after McGrath, 1994) Table 5.16. Possible regional background concentrations of some trace metals in uncontaminated sediment layers from 15 sediment cores, collected in the Stockholm area. Concentrations are based on digestion of samples in 7 N nitric acid (Swedish Standard) and are expressed as µg/g dw (from Landner, 2002). Table 7.1. LC50 values (96 h) for dissolved copper (µg Cu/l) measured with larval rainbow trout (body weight