Occurrence and possible sources of polychlorinated biphenyls in surface sediments from the Wuhan reach of the Yangtze River, China
Twenty-seven surface sediment samples were collected from the mainstream and eight tributaries of the Wuhan reach of the Yangtze River, China, in 2005, in order to assess the distribution, possible sources, and potential risk of polychlorinated biphenyls (PCBs) in the environment. The total concentrations of PCBs (the sum of 39 congeners) ranged from 1.2 to 45.1ng/g-1 dry weight, with a mean value of 9.2ng/g-1. Sediment samples with the highest PCB concentrations came from the tributary sites, which are closer to PCB sources. Conversely, PCB concentrations in the sediment from the mainstream sites of Yangtze River were relatively low. The observed PCB levels were higher than those found in the sediments of other rivers in China, but lower than those in river sediments from other urban areas and harbors around the world. Low-chlorinated PCBs, dominated by tetra-PCBs and penta-PCBs, were identified as being prevalent in the surface sediments. Correlation analyses between the PCBs and the geochemistry and heavy metal content of the sediments suggest that the washing of these compounds from the land into the river by floods and heavy rains, or industrial wastewater and domestic sewage, may be the major sources of the PCBs. According to established sediment quality guidelines, the risk of adverse biological effects from the levels of PCBs recorded at most of the studied sites should be insignificant, although the higher concentrations at other sites could cause acute biological damage.