Effects of flooding on changes in Eh, pH and speciation of cadmium and lead in contaminated soil.

Artificially contaminated soils (A, B) and naturally contaminated soil (S2) in China were used as the tested soils, and the effect of continuous flooding on the changes of Eh, pH and the speciation of cadmium, lead in contaminated soils was studied in the paper. The results indicated that soil Eh decreased with flooding time, and that soil pH increased with flooding time. The changes of soil pH ceased after 60 days of submergence. The exchangeable Cd and Pb decreased obviously during the flooding process from the results of five-step sequential extraction. The calculations of mobility factor (MF) showed that Cd mobility significantly decreased in artificially contaminated soils (A, B) after the flood. But the change of Pb mobility was not significant after the flood, although a decrease of Pb concentration in the exchangeable fraction (SE) was observed.