Biogeochemical processes controlling the speciation and mobility of trace metals in contaminated floodplain soils
Event details
| Date | 29.11.2010 |
| Hour | 16:15 |
| Speaker | Kretzschmar, Ruben |
| Location |
GR A3 31
|
| Category | Conferences - Seminars |
During the past decades to centuries, many river floodplains in Europe and other industrialized regions of the world have served as sinks for inorganic and organic contaminants released into rivers with urban wastewater and runoff, industry, mining, and other human activities. Such historically contaminated floodplain soils may release contaminants into rivers and groundwater even long after the original contamination sources have been remediated. They therefore can pose a continued threat to water quality and ecosystem health. Biogeochemical processes in floodplain soils are highly dynamic, e.g., periodic flooding and drainage induce pronounced soil reduction and oxidation cycles. Our current research aims at a better understanding of the speciation changes and mobility of trace metals and metalloids during redox fluctuations in contaminated floodplain soils, in order to improve predictions of contaminant mobility and toxicity.
Different biogeochemical processes can lead to increasing or decreasing trace metal mobility during prolonged soil flooding. Reductive dissolution of iron and manganese oxyhydroxides results in a loss of sorbent surfaces and increased concentrations of dissolved Fe2+ and Mn2+ in solution, which promotes the release of adsorbed trace metals. Additionally, increasing concentrations of dissolved organic carbon in pore water can contribute to trace metal mobilization. On the other hand, trace metals can be immobilized as a result of rising pH and by formation of poorly-soluble sulfide minerals during sulfate reduction. The potential for trace metal immobilization by sulfate reduction, however, depends on the concentrations of sulfide-forming trace metals and of available sulfate present in the soil. The amount of sulfate in river floodplain soils can become the limiting factor, in which case formation of the most insoluble metal sulfides (e.g., CuS) consume most available sulfide, leaving other chalcophile metals in more mobile forms. However, chalcophile metals can also bind to reduced sulfur groups of soil organic matter. Recent results suggest that prolonged soil flooding can also lead to the formation of metallic Cu(0) and sulfide colloids in the pore water, which may be mobile and thereby increase trace metal mobility. In this presentation, our recent research on trace metal speciation and mobility in river floodplain soils will be presented and discussed.
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Practical information
- General public
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Contact
- Bernier-Latmani, Rizlan (EML)