Quantitative assessment and source apportionment of metal pollution in soil along Chao River

Heavy metal pollution in surface soil is a serious threat to the drinking water source area, which might be washed into the reservoir by stormwater runoff. In this study, concentrations of 26 metals were measured for 15 surface soil samples taken along Chao River, which is the major inflow river for Miyun reservoir. The characteristics of metal concentrations were demonstrated and the pollution sources were analyzed by principal component analysis/multiple linear regression method and positive matrix factorization method. Results show that the mean concentrations of nickel (Ni), chromium (Cr), copper (Cu), and mercury (Hg) are larger than their standard values. Moderate risk of Hg pollution and lightly risk of lead (Pb) and Ni pollution are found in the study area. Anthropogenic behaviors of mining, vehicular emission, and coal combustion are the dominant metal pollution sources, which contribute to 33-35, 17-27, and 11-26% of the total metal pollution, respectively. Most of Hg, Pb, Cu, Cr, and manganese come from these sources. Natural source contributes to 22-29% of the total metal pollution, which is the main source of zinc and cadmium.