Polychlorinated biphenyls in urban lake sediments from Wuhan, Central China: occurrence, composition, and Sedimentary record

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Nine surface sediments and a dated sediment core collected from urban lakes in Wuhan, Central China, were analyzed to investigate the concentrations, occurrence, composition, and depositional fluxes of polychlorinated biphenyls (PCBs). The concentrations of {Sigma}PCB (the sum of 39 congeners) in surface sediments ranged from 0.90 to 46.14 ng g–1 dry weight. Only in Longyang Lake and Nantaizi Lake did concentrations of {Sigma}PCB exceed the effects range low value. The concentrations of {Sigma}PCB in the sediment core varied from 1.3 to 43.1 ng g–1. The profile of {Sigma}PCB concentrations closely reflected the changes in production and usage of PCBs in this region, and the profiles of {Sigma}PCB fluxes were similar to those of {Sigma}PCB concentrations, except for a distinct decrease in {Sigma}PCB fluxes after about 1998. This was possibly due to more large-scale cases of land use and increasingly rapidly urban development occurring in China since 2000, resulting in increased lake sediment fluxes but reduced {Sigma}PCB fluxes. The results suggest that urban run-off and wet deposition leaching PCBs off the land and into the lake may be the most important source of PCBs in Donghu Lake. Sedimentary profiles for PCB congeners showed a decrease in concentrations in the following order: penta~hexa- > tetra- > tri- > hepta-PCBs. The relative abundances of tri- and tetra-PCBs in the core accounted for more than 80% of the total PCBs detected in sediments deposited before their first commercial use, suggesting the post-depositional mobilization of less chlorinated PCB congeners in the sediment core. This is the first study to estimate the spatial and historical trends of PCBs in subtropical urban lakes.

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