Thursday, November 8, 2007 - 11:35 AM
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Influence of EDDS on Metal Speciation in Soil Extracts: Measurement and Mechanistic Multicomponent Modeling.

Gerwin F. Koopmans1, Walter D.C. Schenkeveld1, Jing Song2, Yongming Luo2, Wim J. Chardon3, Jan Japenga3, and Erwin J.M. Temminghoff1. (1) Department of Soil Science, Wageningen University, P.O. Box 47, Wageningen, Netherlands, (2) Institute of Soil Science, Chinese Academy of Sciences, Nanjing, China, (3) Alterra, Wageningen, Netherlands

The use of the [S,S]-isomer of EDDS to enhance phytoextraction has been proposed for the remediation of heavy metal contaminated soils. Speciation of dissolved metals in the presence of EDDS and dissolved organic matter (DOM) received, however, almost no attention, while speciation and competition between metals for binding with synthetic chelants and DOM play an important role in relation to uptake of metals by plants. We investigated the influence of EDDS on speciation of dissolved metals in batch extraction experiments using four field-contaminated soils with a wide range in pH. Free metal concentrations were determined with the Donnan membrane technique, and compared with results obtained by the chemical speciation program ECOSAT and the Non Ideal Competitive Adsorption Donnan (NICA-Donnan) model using a multicomponent approach. Model predictions of free metal concentrations were very good, and predicted values were mostly within 1 order of magnitude difference from the measured concentrations. Multicomponent models can be helpful in chelant-assisted phytoextraction experiments to predict the speciation of dissolved metals and to further the understanding of metal uptake by plants.

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