Metal Mobility and Fraction Distribution in a Multimetal Contaminated Soil Chemically Stabilized with Different Agents

To investigate the efficiency of chemical stabilization on soil residuals after soil washing, laboratory batch experiments were performed on a clayish soil contaminated with Cu, Cr, Ni, Pb, Zn with lime, Na2HPO4, or a mixture containing FeSO4 under various concentrations. The instant and overall mobility and the fraction distribution of these metals after 7-day stabilization were determined by acid extraction and the modified Tessier's sequential extraction procedures. Results show that the potential mobility of metals is orders of magnitude much more than instant mobility, and specific attention therefore should be paid to the potential mobility when evaluating the performance of chemical stabilization. Metal fraction analyses suggested that the metal stabilization involved various mechanisms dependent on the metal's properties, species, and the interference between metals. Among the stabilization combinations, the mixture of FeSO4 and lime most effectively reduced the sum of the metal instant mobility, and 15 mg g(-1) Na2HPO4 achieved the highest efficiency in lessening the corresponding overall mobility. However, a more substantial decrement of instant mobility was observed. (C) 2011 American Society of Civil Engineers.