Occurrence, sources, and cancer risk of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in agricultural soils from the Three Gorges Dam region, China

Eighty agricultural topsoil samples were collected near the Three Gorges Dam region of Yangtze River, China, to investigate concentrations, distribution patterns, and possible sources and potential cancer risks of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in this area. Total PAHs concentrations in agricultural topsoil ranged from 277.79 to 3,217.20 ng g(-1) (ppb) with a mean concentration of 1,023.48 +/- 815.31 ng g(-1). Total concentrations of seven carcinogenic PAHs (C-PAHs) were between 45.85 ng g(-1) and 1,147.45 ng g(-1), accounting for 6% to 49% of the total PAHs. Total PCBs concentrations varied from 18.56 to 183.90 ng g(-1) with a mean concentration of 35.28 +/- 41.01 ng g(-1). Positive linear correlations were found between total PAHs and total PCBs, showing these compounds may originate from common sources. Isomer ratios analysis indicated that atmospheric deposition was the main common source for PAHs and PCBs. The incremental lifetime cancer risk (ILCR) of PCBs in agricultural topsoil near the Three Gorges Dam region were all below 10(-6), indicating no cancer risk, whereas ILCR of PAHs were between 10(-6) and 10(-4); special attention needs to be paid to PAHs in the study area.