[Soil pollution of Cu, Zn, Pb and Cd in different city zones of Nanjing].

The Nanjing city was divided into six zones as smelter industry, inner commercial, inner residence, newly developed, urban greenland and preserved scenic. In each zone, soil samples were randomly collected by triple subsampling technique. Total 56 soil samples were digested by mixed solution of nitric, chloridic and sulphatic acids and by sequential extractants respectively according to the standard methods. The total and fractional heavy metals were determined by AAS. The mean total content of Pb, Cu, Zn and Cd of the soils from smelter industry, inner commercial, inner residence, newly developed, urban greenland and preserved scenic zone was 117.1 +/- 103.7 mg.kg-1, 39.86 +/- 39.9 mg.kg-1, 273.3 +/- 131.6 mg.kg-1 and 1.13 +/- 0.7 mg.kg-1, with the overall pollution index being 5.4, 4.9, 3.4, 1.6, 2.4 and 2.3 respectively. The pollution in the smelter industrial zone was characterized by high concentration but low chemical mobility of Pb and Cd, while that in inner cities by high concentration of lead and zinc with quite larger acelatic acid extractable pool. Except for the soils from newly developed and preserved zones, the heavy metals were more or less superficial in respect to their depth distribution in the urban soils. The dramatic soil pollution of Pb and Cd in the urban area might cause any health risks for children, whose activities are believed to happen in a relative limited area. The future research on urban soil pollution should pursue the effect of soil pollution on human environment in the urban area.