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Rhizotoxicity of cadmium and copper in soil extracts

Authors

  • Astrid Voigt,

    1. Department of Natural Resource Sciences, Macdonald Campus, McGill University, 21,111 Lakeshore Road, Ste-Anne-de-Bellevue, Québec H9X 3V9, Canada
    2. Applied Ecotoxicology, Biotechnology Research Institute, 6100 Royalmount Avenue, Montreal, Québec H4P 2R2, Canada
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  • William H. Hendershot,

    Corresponding author
    1. Department of Natural Resource Sciences, Macdonald Campus, McGill University, 21,111 Lakeshore Road, Ste-Anne-de-Bellevue, Québec H9X 3V9, Canada
    • Department of Natural Resource Sciences, Macdonald Campus, McGill University, 21,111 Lakeshore Road, Ste-Anne-de-Bellevue, Québec H9X 3V9, Canada
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  • Geoffrey I. Sunahara

    1. Applied Ecotoxicology, Biotechnology Research Institute, 6100 Royalmount Avenue, Montreal, Québec H4P 2R2, Canada
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  • Presented at the Symposium on Risk Assessment of Metals in Soils, 14th Annual Meeting, SETAC Europe Meeting, Prague, Czech Republic, April 18–22, 2004.

Abstract

Dissolved organic matter (DOM) influences metal speciation in soil solutions and, hence, metal toxicity. Root-elongation experiments were conducted to examine the effect of soil solution components, such as Ca, H, and DOM, on metal rhizotoxicity. A biotic ligand model (BLM) was tested for its ability to predict the rhizotoxicity of Cd and Cu in soil extracts. It was hypothesized that the concentration of Cd and Cu bound to functional groups at the root surface estimated using a BLM would be a better predictor of rhizotoxicity than the free-metal ion activity in solution. Both metals became less toxic at higher DOM, Ca, and H concentrations. Solution speciation and the effect on root growth explained most of the variability observed in the DOM experiments, but not in the cation experiments. It was concluded that Ca and H inhibited the rhizotoxicity of both metals tested. Rhizotoxicity data correlated better with estimates of metal-root complexes that have been estimated with a BLM than with free-metal ion activity or with total metal concentrations. The BLM seems to be a promising approach for predicting metal availability in soils and for assessing the associated risk.

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