Distributions, historical trends, and source investigation of polychlorinated biphenyls in Dianchi Lake, China.

Six commonly occurring polychlorinated biphenyl congeners (PCB28, PCB52, PCB101, PCB138, PCB153 and PCB180) were measured in water, surface sediments, and sediment core samples from 10 monitoring stations across Dianchi Lake in Kunming, China to determine the distributions, historical trends, and sources of PCBs to this ecologically and regionally important water body. The summed total concentration of all six PCB congeners ranged from 13 to 72 ng L(-1) in water, 0.6-2.4 ng g(-1) dry weight (d.w.) in surface sediment, and from non-detectable to 2.2 ng g(-1) d.w. in sediment core samples. The six PCB congeners were found to demonstrate similar distribution characteristics across water and surface sediment samples, with PCB28 and PCB52 accounting for more than 67% of the total summed concentration in both matrices. The concentration of individual congeners in each media decreased in the order of PCB28>PCB52>PCB101≈PCB138≈PCB153≈PCB180. Analysis of PCB congeners in sediment core layers as a function of depth revealed two distinct peaks occurring in the top velocity layer and in the layer between 25 and 30 cm in depth (corresponding to 1970s). Core sediment analysis showed PCBs are currently being released to Dianchi Lake and showed the historical trends of PCB deposition into the lake sediment. Data from this multi-media exploration of PCBs can be used by researchers, regulators, and policy makers to understand the fate of PCBs in Dianchi Lake, and also to begin to identify current sources of PCBs to the lake.