Application of sequential extraction methods to determine the speciation of Cr-contaminated soils from the New Jersey Meadowlands

Three sequential extraction methods (SE) were implemented to determine the speciation of Cr in soil samples taken from a Chromite Ore Processing Residue (COPR) dump site located in the New Jersey Meadowlands. The results from the SE methods indicated that Cr was primarily associated with the oxidizable and reducible soil fractions, and that a significant amount of Cr remained un-extracted and was present in the residual soil fraction. The quantitative analysis of the SE data proved to be difficult due to strong differences in the estimates of associated Cr to soil fractions. This is due to the limitations associated with the sequential extraction schemes such as re-adsorption of metals between steps. To avoid the issues in analysis due to the limitations seen in the SE data; it is proposed that a secondary method, such as X-ray Absorption Spectroscopy (XAS), is to be used in conjunction with the SE methods. Here, results from XAS analyses were proven to provide proper constraint to the SE data. The results from the XAS method qualitatively supported the sequential extraction scheme results, but demonstrated that comparisons between the SE and XAS data resulted in poor correlations meaning that direct comparisons is unreliable. Since application of XAS along with sequential extraction schemes is not feasible in many situations, it is suggested to so the suggestion is to design optimized sequential extraction scheme.M.S.Includes bibliographical referencesby Ashley C. McNamar