In order to fully understand the pollution of polychlorinated biphenyls (PCBs) in Dongting Lake, 209 PCB congeners were quantitatively detected and analyzed by isotope-dilution high-resolution mass spectrometry in 21 surface water sampling sites of Dongting Lake and the inflow rivers of the lake. The results showed that a total of 50 PCB congeners were detected in the study area. The ρ(ΣPCBs) ranged from 0.077 to 10 ng·L-1, with an average concentration of 2.7 ng·L-1 and a median concentration of 1.9 ng·L-1. The order of contamination concentrations were as follows:the inflow rivers of the lake > lake region > outlet. Compared with the reports of domestic and foreign studies, PCB pollution in Dongting Lake is at a low level. The main pollutants in the surface water were dichlorobiphenyls and tri- and tetrachlorobiphenyls, with relative abundances of 67%, 14%, and 16%, respectively. PCB11, PCB17, PCB18, PCB20+33, PCB28, PCB47+75, PCB52, and PCB68 were the most widely distributed and detected in more than 80% of samples. Among them, ρ(PCB11) was the highest, with an average concentration of 1.6 ng·L-1, accounting for 59% of ρ(ΣPCBs), from the domestic organic pigment production process of unintentional emissions. Atmospheric transport deposition and historical residue were the main sources of PCBs in water. According to the toxicity equivalent factor method, the ecological toxicity risk of the study area was evaluated, and the results showed that the TEQ in the water was far lower than the relevant standard limit, indicating that the pollution of PCBs in the surface water of Dongting Lake and the inflow rivers would not cause harm to exposed organisms.
Keywords: Dongting Lake; high-resolution mass spectrometry; pollution characteristics; polychlorinated biphenyls (PCBs); risk assessment.