PCBs in Donggang River Watershed sediments, Taiwan.

Polychlorinated biphenyls (PCBs) were measured in the sediments of the Donggang River Watershed, one of the most polluted bodies of water in southern Taiwan. Field data showed that detectable concentrations of 121 PCB congeners were found and total PCBs were measured in 32 out of 33 samples, and 98 congeners were detected. The total concentrations of PCBs in the sediment ranged from 25.5-63.5 ngg(-1) dw with a geometric mean ± standard deviation of 4.00 ± 1.73 ngg(-1) dw, with one sample below the detection limit. The highest concentration (20.79 ngg(-1) dw) was found at the most downstream sampling site near the head of the estuary, while average levels were highest at the tributary sampling site, ranging from 8.81-019.4 ngg(-1) dw. In general, the average concentrations in the tributary sampling sites were higher than those in the main stem sampling sites, which were 24.02 ± 10.15 and 19.97 ± 8.9 ngg(-1) dw, respectively. Among the 121 congeners, congener 1, 3, 22, 25, 33, 21, 53, 47, 41, 64, 71, 107, 136, 146, 158, 157, 200, 172, 189, 207, 205, 206, and 209 were all below the detection limit and were not found in any samples. Congeners 191, 85, and 26 were the most commonly detected, however, PCB 26, 12+13, and 52 were the most abundant congeners and contributed 11.5, 8.4, and 6.96% to the total PCBs, respectively. The results indicated that trace PCBs were still detectable in the sediment of the Donggang River and its tributaries. However, the concentrations were considerably lower than those found in other studies of nearby areas in Taiwan and around the world.