Sustainable management of urban soils to minimize their potential impact on the environment requires an understanding of factors influencing mobility of heavy metals in the soils.The objective of this study was to analyze concentrations, forms and acid solubilities of heavy metals in the soils from fifty residential sites in Hangzhou City.In addition,Pb,Cu,Zn, and Cd adsorption-desorption behavior,relationship between release of heavy metals and pH,and acid buffer capacity of the soils were also studied.The soils in the residential sites had been anthropogenically contaminated by heavy metals to a different extent.Except for Cr and Mo,however,concentrations of these heavy metals in the soils were found lower than those in the soils in commercial districts.Cd,Co,Cr and Ni were mainly in stable residual forms,while Cu,Pb,Zn and Mn were mostly in extractable forms.Generally the soils in the residential sites had a high capacity to adsorb heavy metals,so stably that they were not liable to get displaced by neutral salts.The capacity however,decreased with the decrease in pH,and release of heavy metals from the soils increased rapidly when soil pH went down below 4.0～6.0.The acid buffer capacity of the soils varied greatly and was mainly controlled by soil CaCO₃ content.The heavy metals in soils with a high acid buffer capacity were low in solubility. Since the soils in the residential sites contained higher CaCO₃ brought in by construction materials,they often had a high acid buffer capacity and thus enhanced stability of the heavy metals in the soils.Our data indicated that heavy metals of the soils from residential sites in Hangzhou City did not pose significant hazard to the environment in normal conditions.