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Concentrations of seven polybrominated diphenyl ethers (PBDEs) congeners were determined in surface sediments collected from several rivers and lakes in Hanoi, the capital city of Vietnam, to understand the status of background contamination, accumulation pattern, sources, and toxic implications for benthic organisms. Total PBDE concentrations in all sediment samples ranged from 0.03 to 17.5 ng/g dry weight (mean 1.33 ng/g dry wt). The most predominant congeners were BDE-47 and BDE-99, which comprised 30 and 25 % of total PBDE concentrations, respectively. Results from statistical analysis indicated that the potential sources of PBDEs of sediments in Hanoi may come from penta-BDE and octa-BDE mixtures. Risk quotients of PBDEs in sediments were also calculated for a benthic species, ranged from 2.12 × 10 - 1.60 × 10, and were markedly lower than threshold value for occurrence of any ecotoxicological risk. This study provides some of the most comprehensive data on the occurrence of PBDEs in sediments from lake and river systems in Vietnam.

Concentrations of PCBs and OCPs were measured in 35 surface sediment samples collected from offshore waters of Central Vietnam. The mean concentrations of PCBs, HCHs, and DDTs in surface sediments were 86.5, 37.0, and 44.5pgg(-1), respectively. Additionally, nine PCDDs, eleven PCDFs, and twelve dl-PCBs were also examined in 19 sediment core samples collected from five locations. Concentration of PCDDs, PCDFs, and dl-PCBs ranged from 200 to 460, 0.39 to 2.9, and 1.6 to 22pgg(-1), respectively. OCDD was detected at the highest concentration, ranged from 100 to 300pgg(-1). Generally, the concentrations of PCDD/Fs at shallower depths were higher, meanwhile the depth profiles of dl-PCBs in sediment cores were different than the depth profiles of PCDD/Fs. The results suggest that the pollution of PCBs might be from many different sources leading to the variation between depths.