Speciation of heavy metals in polluted soils by sequential extraction and ICP spectrometry

Heavy metals were leached from various polluted soils by selective extraction reagents (water, BaCl2, acetate buffer + EDTA, HNO3) in order to establish the distribution of the chemical species of Cd, Zn, Cu and Pb. The leachates were directly injected into a plasma spectrometer in order to analyse immediately the extraction solution. This continuous on-line analysis gives qualitative information about the chemical behaviour of each element in function of the type of soil. It permits also to modify the extraction procedure for each sample studied by adjusting the volume of the extraction solution, the time of extraction, or by choosing another extraction reagent more adapted to the sample. The sum of the respective fraction is in rather good agreement with the total analysis of the soil.