EVALUATION OF SEQUENTIAL EXTRACTION FOR SPECIATION OF TRACE-METALS IN MODEL SOIL CONTAINING NATURAL MINERALS AND HUMIC-ACID

摘要

A model soil synthesized with several natural minerals and humic acid is used to evaluate the sequential extraction for speciation analysis of trace elements in soil. Although the recommended sequential extractants are able to bring the individual geochemical phases into solution at the experimentally defined stage, none of the extractants is completely specific and efficient. Various proportions of metals released at exchangeable, carbonate-bound, Fe-Mn oxide-bound, organic-bound fractions are readsorbed onto the other solid geochemical phases during sequential extraction. However, it is difficult to quantify the extent of readsorption and/or redistribution for the individual element and for the individual geochemical phase.