State and mobility of Cadmium(Cd)

Lead(Pb)

Copper(Cu) and Zinc(Zn) pollution were investigated at different depths of polluted farmland black soil

and the application of the BCR sequential extraction was studied.The results showed that the mobility order of the heavy metals is Cd>Cu>Pb>Zn.Cadmium occurred more abundantly in mobile fraction than did the other elements.The concentration of Pb in the acetic acid extractable fraction

as well as the concentration of hydroxide-bound fraction of Pb

Cu near the roadsides and Cd

Pb and Zn in the suburb all increased with the depth of profiles

indicated some downward movement of heavy metals.The concentrations of organically-bound fraction of the heavy metals in most of sampling area were all higher in the plow layer

which indicated the accumulation of heavy metals of this fraction in the surface layer.The results showed that application of sequential extraction of BCR was useful in assessing the pollution and movement of heavy metals in soil.