Sequential Extraction Procedure for the Speciation of Particulate Trace Metals

An analyticai procedure involving Sequential chemical extractions has been developed for the partitioning of Particulate trace metals (Cd, Co, Cu, Ni, Pb, Zn, Fe, and Mn) into five fractions: exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter, and residual. Experimental results obtained on replicate samples of fluvial bottom sediments demonstrate that the relative standard deviation of the Sequential extraction procedure is generally better than A10 %. The accuracy, evaluated by comparing total trace metal concentrations with the sum of the five individual fractions, proved to be satisfactory. Complementary measurements were performed on the individual leachates, and on the residual sediments foilowing each extraction, to evaluate the selectivity of the various reagents toward specific geochemical phases. An application of the proposed method lo river sediments is described, and the resulting trace metal speciation is discussed.