1. Explaining Low Bioavailability of Metals in Contaminated Urban Soils Sauvé S, Ge Y, Murray P, Hendershot W Département de chimie, Université de Montréal Department of Natural Resource Sciences, Macdonald Campus of McGill University

2. © Sauvé 2001 Explaining… Soil chemistry pH partitioning chemical speciation Bioavailability plant metal uptake soil fauna soil microbial process

3. © Sauvé 2001 Soil pH Ranges 3045 US Agricultural soils Mean pH=6.3 70 Montreal Urban soils Mean pH=7.7 Holmgren et al. 1993. J. Environ. Qual. 22:335- 348. Ge et al. 2000. Environ. Pollut. 107:137-144 and Sauvé et al. 1998. Environ. Pollut. 98:149- 155. 10 th centile = 5.0 90 th centile = 7.9

4. © Sauvé 2001 Partitioning Tot al OM-Bound Free Metal Cl Complexes SO 4 Complexes

5. © Sauvé 2001 Solid/liquid Partitioning Assumes a unique and constant ratio between solution and solid phases: Total metal is in mg/kg dry soil and dissolved metal is in mg/L, hence K d are usually reported as L/kg Sensitive to determination method, solid:liquid ratio, extracting solution, time of extraction and filtration

6. © Sauvé 2001 Dependence of K d on pH For a compilation of literature K d ’s, 29 to 58 % of the variability depends on soil solution pH. Sauvé S. Hendershot W., Allen H.E. 2000. «Solid-Solution Partitioning of Metals in Contaminated Soils: Dependence on pH, Total Metal and Organic Matter ». Environ. Sci. Technol. 34:1125-1131.

7. © Sauvé 2001 Solution Speciation

8. © Sauvé 2001 Partitioning Sauvé S. 2001. The Role of Chemical Speciation in Bioavailability. In: Naidu R., Gupta V.V.S.R., Kookana R.S., Rogers S., Adriano D. (Eds.), Bioavailability, Toxicity and Risk Relationships in Ecosystems. (in press).

9. Mineral Solubility Equilibria Sauvé S. 2001. «The Role of Chemical Speciation in Bioavailability » In: Naidu R., Gupta V.V.S.R., Kookana R.S., Rogers S., Adriano D. (Eds.), Bioavailability, Toxicity and Risk Relationships in Ecosystems. (in press).

10. © Sauvé 2001 Chicory uptake of Cd Ge Y, Murray P, Sauvé S, Hendershot W. Low metal bioavailability in a contaminated urban site. Submitted to Environmental Toxicology and Chemistry.

11. © Sauvé 2001 Linking plant uptake and soil metals Dandelion, bladder campion, chicory with Cd, Cu, Ni, Pb and Zn (n=20 to 40)  Bladder campion (leaf) Cd, Ni, Pb and Zn were significant, but not Cu.  Dandelion, Cd and Zn (leaves and roots) were significantly related to total metals  For chicory, only Pb in the roots had any significant relationship with total soil Pb

12. © Sauvé 2001 Dandelion field data Marr K, Fyles H, Hendershot W. 1999. Trace metals in Montreal urban soils and the leaves of Taraxacum officinale. Canadian Journal of Soil Science 79:385-387.

13. © Sauvé 2001 Soil Respiration Dumestre A, Sauvé S, McBride M, Baveye P, Berthelin J. 1999. Copper speciation and microbial activity in long-term contaminated soils. Archives of Environmental Contamination and Toxicology:36:124-131.

14. Bioavailability No consistent predictor of plant metal uptake In the field, wild chicory was absent from the most contaminated sites Soil respiration (in a glucose amendment assay) is unaffected by metals Nitrification potential significantly inhibited by higher Cu, Ni, Pb and Zn levels Ge Y, Murray P, Sauvé S, Hendershot W. Low metal bioavailability in a contaminated urban site. Soumis à Environmental Toxicology and Chemistry.

15. © Sauvé 2001 Earthworms Kennette D, Sauvé S, Hendershot W, Tomlin A. 2001. Uptake of trace metals by the earthworm Lumbricus terrestris L. in urban contaminated soils. Applied Soil Ecology (sous presse).

16. © Sauvé 2001 Soil Fauna Little or no toxicological effects on earthworms, albeit some accumulation of metals is observed No effects observed on species occurrence or distribution of soil invertebrates Could represent a risk for trophic transfer to worm-eating birds or rodents

17. © Sauvé 2001 Concerns Wild chicory is absent from the most contaminated areas of the site and this suggests a potential for reduced species diversity The sensitivity of soil microbes responsible for nitrification also suggests that nutrient cycling is affected, with some potential effects on species distribution

18. © Sauvé 2001 Concerns at mid- to long-term No drastic effects, but nevertheless some problems with a decreased sustainability of the ecosystem on some sites Present, future and potential land uses have to be considered