Forms and Acid-solubility of Heavy Metals in the Soils from Residential Areas in Hangzhou City, Zhejiang Province

The objective of this study was to analyze the concentrations, forms and acid solubility of heavy metals in the soils from fifty residential areas in Hangzhou city. The results showed that the soils in the residential areas had been anthropogenically contaminated by heavy metals to a different extent, and heavy metals in the soils, including Cd, Cr, Cu, Ni, Pb, Zn, Mn, and Mo, were higher than those in the suburban agricultural soils. Except Cr and Mo, however, the metal concentrations of the soils in the residential areas were lower than those of soils in commercial areas. The concentrations of the metals in the soils increased with ages of the residential areas. Cadmium, Co, Cr and Ni were mainly associated with residual fraction, while Cu, Pb, Zn and Mn were majorly extractable fractions. Except for Zn and Mn, the concentrations of the acid extractable metals were generally low. Amounts of the heavy metals dissolved in dilute acid (pH 2.5) increased with decreasing pH in equilibrium solution. Low potential solubility of the heavy metals in the dilute acid was due to their low percentage of acid-extractable fraction of the heavy metals in the soils. Our data indicated that heavy metals of the soils from residential areas in the Hangzhou city did not pose a significant environmental health hazards in normal conditions.