Distribution Characteristics and Potential Risk of PCBs in Surface Water from 22 Tributaries and Mainstream in Middle Reaches of Yangtze River
长江中游干流及22条支流表层水中多氯联苯的分布特征及其潜在风险

47 surface water samples were collected from 22 tributaries and mainstream of the Yangtze River from Chongqing to Yichang. The contents of 28 PCB congeners in surface water samples were measured using Varian CP3800/300 GC-MS/MS technique. PCB8, 28, 52 and 118 are the most predominant PCB congeners in the samples from tributaries, PCB8 and 28 are the most predominant PCB congeners in those from mainstream. The measured level of PCBs in the samples from the tributaries and from the mainstream were 20.71 ng·L-1 and 13.25 ng·L-1 respectively. The highest concentrations of PCBs was detected in the samples from Rangdu River (61.79 ng·L-1), the lowest concentrations of PCBs was detected in water samples from Caotang River (3.77 ng·L-1). The average concentrations of PCBs in the samples from more than 85% of tributaries are higher than the USEPA criterion continuous concentration (14 ng·L-1), however, all the levels of PCBs in mainstream and tributaries are far lower than the Chinese drinking water guideline value (500 ng·L-1). The concentrations of PCBs in the samples were in the same order of magnitude of those reported on lower levels in European and American countries. The estimated cumulative cancer risk for the local residents who drink water from tributaries and mainstream were 2.07×10-7 and 1.33×10-7, which shows that cancer risk is negligible due to PCBs contamination in these samples.