[Extraction of heavy metals from contaminated soils with EDTA and their redistribution of fractions].

EDTA was used as extractant to leach Pb, Zn, Cu and Cd from tailing soils in soil columns. The redistributions of Pb, Zn, Cu and Cd were determined using the sequential extraction procedure of the optimized European Community Bureau of Reference (BCR) before and after extraction. The results indicated that EDTA was an effective extracting agent because of its strong chelating ability for different heavy metals. Percentage extractabilities of metal followed the sequence of Cd>Zn>Cu>Pb. The four fractions of metal could be extracted by EDTA and the proportions of Pb, Zn, Cu and Cd in the four fractions varied largely after EDTA extraction. The extraction efficiency of EDTA on the acid-extractable fraction was significant in shallow soil column, while in deeper soil column, a descent of the extraction efficiency on reduced, oxidizable and residual fractions was obtained. And heavy metals chelated by EDTA were more easily desorption by soil particles with the depth of the soil columns increased.