Levels, distributions and profiles of polychlorinated biphenyls in surface soils of Dalian, China

Surface soil (0–5 cm) samples from 14 sampling sites including rural and urban areas of Dalian, a coastal city in Liaoning Province, China, were collected and analyzed for 84 polychlorinated biphenyls (PCBs). Total 57 PCB congeners were identified and mean concentration of total PCBs among all the sites was 2.8 μg kg−1 dry weight (dw) with a range of 1.3 (rural site) to 4.8 μg kg−1 dw (urban site). For the urban sites, total PCB concentrations in the soil samples collected in industrial area are highest, followed by those from business/residential sites and the garden sites, but the differences are not significant. Higher percentage of lighter weighted molecular PCBs were found in the rural site than urban sites in Dalian, possibly indicating the “urban fractionation effect”. Total seven dioxin-like PCBs (CB-77, 81, 105, 114, 118, 123, and 126) have been found in Dalian soils and the mean concentration (in μg kg−1 dw) among all the sites of CB-105 (0.17) is higher than any other dioxin-like PCBs, followed by that for CB-81 (0.14) and for 118 (0.06). No significant correlation relationship between the concentrations of dioxin-like PCBs and those of total PCBs was found. The toxic equivalency (TEQ) concentrations (in ng kg−1 dw) of these seven dioxin-like PCBs in 14 soil samples range from 0.0067 to 4.8857 (with a mean 1.3727) for humans and mammals, from 0.0017 to 0.377 (with a mean 0.147) for fish, and from 0.017 to 31.477 (with a mean 17.237) for birds.