Wednesday, November 7, 2007
246-9

Metal Redistribution During Sequential Chemical Extraction of a Multi-Metal Contaminated Soil.

Mimi Roy and Louis M. McDonald. Plant & Soil Sciences, West Virginia University, Davis College of Agriculture, Forestry & Consumer Sciences, 1124 Agricultural Sciences Bldg, Morgantown, WV 26506

Selective sequential extraction techniques to fractionate metals within operationally defined soil fractions furnish information about the bioavailability, mobility and transport of the elements in natural environment. However, one of the major limitations of this technique seems to be associated with readsorption where the extracted metals are redistributed on the solid phases. In this study the efficiency of the chemical extractions were assessed for a multi metal contaminated site and then compared with some thin film tests to address readsorption issues. Extractions done in this study operationally isolates the water soluble, exchangeable, carbonates, Mn oxides, organic matter, Fe oxides, sulfidic and residual fractions of the solid phase. The concentration of the individual metals in each of these phases were determined by ICP-AES. Zn, Cd, Cu were primarily associated with the water soluble and exchangeable phases while Pb was found mostly in the oxide and organic matter associated phases and even to some extent in the sulfidic phases. Comparing the results with thin-film tests to address redistribution issues, readsorption accounted for less than 5 percent in the water soluble and exchangeable fractions but 15-20% for carbonates, oxide and organic matter fractions. Thus it can be concluded that for these samples, Zn, Cd and Cu associated with the water soluble and exchangeable phases are less susceptible to readsorption during selective chemical extractions.