Levels and distributions of PBDEs and PCBs in sediments of the Bohai Sea, North China

Fifty-four surface sediments covering the whole water body of the Bohai Sea in North China were collected and analyzed for PBDEs and PCBs, to acquire information about their levels, distributions and possible sources. The results show that BDE 209 is the predominant congener with a mean value of 7000 pg g(-1) dry weight, two orders of magnitude higher than other BDE congeners. The concentrations of Sigma PBDE7 (including BDE 28, 47, 99, 100, 153, 154 and 183) range from 220 to 900 pg g(-1) dw. Significant correlations were found between BDE congeners and total organic content (TOC) (r(2) = 0.48-0.73). Pearson analysis shows that most tri- to hepta-BDE congeners were closely correlated (r(2) > 0.69). Congener patterns varied little among most of the samples and all the detected BDE congeners make a relatively equal mass contribution to Sigma PBDE7. Such a profile is notably different from any of the BDE commercial products. As for PCBs, only a few congeners were detected in certain samples. They ranged from nd-610 pg g(-1) dw with a mean value of 145 pg g(-1) dw, at the lower end of the range reported in remote areas of Europe and North America. The overall burdens of Sigma PBDE7 and BDE 209 within the upper 3 cm sediment layer were estimated to be 0.95-1.25 t and 11-19 t respectively. The latter accounts for about 0.008-0.014% of total BDE 209 produced in China from 1999 to 2006.