Abstract: The urban soil samples in Changchun were studied for the potential chemical speciation of some heavy metals by chemical extraction in order to analyse the relationships between the chemical speciation and the total heavy met al as well as the physicochemical characteristics of urban soils. The results sh ow that Pb and Cu are mainly in residual and organic phases, Cd is largely associated with the residual and exchangeable fractions, while Zn is largely associated with the residual and Fe-Mn oxide phases. The highest percentage of Cd associated with available fractions is 31.98%. The total metal contents have direct influences on the exchangeable and available Cd and Zn contents, inverse influences on the Fe-Mn oxide Cu and Pb contents, and no influences on　the carbonate Zn and Pb contents. The exchangeable Cd contents are directly correlated with cation exchange capacity, and the available Cd contents are inversely correlated with cation exchange capacity. The carbonate fractions are directly correlated with pH, and Fe-Mn oxide fractions are directly correlated with oxidation-reduction potential. The organic Cu contents are directly correlated with organic contents.

Key words: chemical extraction, chemical speciationactivity, influencing factors