4. Conclusions
Desorption of heavy metals from soil aggregates of a lead/zinc tailing soil with EDTA was carried out.
Extraction of heavy metals with different extraction time shows that extractable content of heavy metals
was the highest in S2 for Zn or S3 for Pb, Cd and Cu, while lowest extraction efficiency was found in S2
for Zn, Pb and Cd or S3 and S4 for Cu, considering the total amount of the concerned metals in the
aggregates. The extraction kinetics of the four metals could be well fitted with Elovich formula. The
highest desorption rate appeared in the extraction of S4 for Zn and S1 for Pb, Cd, and Cu, and the lowest
appeared in extraction of S2 and S3 for Zn, S4 and S3 for Pb, and S3 for Cu. The extraction of the tested
metals strongly depended on the original pH value of EDTA extraction solution. Extractable metal
contents decreased with pH value. Exchangeable/acid soluble fraction and reducible fraction of four soil
metals were mainly affected by EDTA extraction.