Concentrations, distribution, sources, and ecological risk assessment of heavy metals in agricultural topsoil of the Three Gorges Dam region, China.

Concentrations, distribution, sources, and ecological risk of seven heavy metals including chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), lead (Pb), cadmium (Cd), and mercury (Hg) in agricultural topsoil samples of the Three Gorges Dam region, China were investigated in this study. Among seven heavy metals, Zn had the highest mean concentration (149 mg kg(-1)) in the agricultural topsoil, followed by Cr (66 mg kg(-1)), Cu (52.2 mg kg(-1)), Pb (13.0 mg kg(-1)), Ni (8.5 mg kg(-1)), Cd (0.29 mg kg(-1)), and Hg (0.08 mg kg(-1)). Enrichment factor (EF) values of Zn, Cu, Cd, and Hg were higher than 1.5, indicating that Zn, Cu, Cd, and Hg were the major pollutants in this study area. The average potential ecological risk index (RI) value was 147, suggesting that heavy metals in the agricultural topsoil in the study area had a low ecological risk. The result of factor analysis (FA) and correlation analysis showed that long-term use of chemical fertilizer and pesticides, natural rock weathering, and atmospheric deposition were the several main sources of seven heavy metals in agricultural topsoil of the Three Gorges Dam region. Factor analysis-multiple linear regression (FA-MLR) results indicated that the most important source in this area was long-term use of chemical fertilizer and pesticides, which contributed 70 % for Cu and Zn, 62 % for Cd, and 72 % for Hg. More attention must be paid to the extensive use of chemical fertilizers and pesticides containing heavy metals which have been accumulated in the agricultural soil.