Spatial distributions of methoxylated and hydroxylated polybrominated diphenyl ethers in the East China Sea-A seaward increasing trend

Methoxylated (MeO-) and hydroxylated (OH-) polybrominated diphenyl ethers (PBDEs) in marine environments have been of increasing concern due to their potential ecological toxicities and worldwide occurrence. However, few reports have been referred to their occurrence and distributions in marine sediments despite large numbers of studies on marine organisms have been reported. In the present paper, nine MeO-BDEs, ten OH-BDEs and three phytoplankton biomarkers (PBs) of brassicasterol, dinosterol and alkenones have been measured in surface sediments from the East China Sea. 6-MeO-BDE47, 2′-MeO-BDE68 and 6-OH-BDE47 were predominant congeners, ranging from 5.2 to 599.5 pg g−1 dw, 5.2 to 562.4 pg g−1 dw, and 11.4 to 129.1 pg g−1 dw, respectively. Their spatial patterns all presented a seaward increasing trend and higher levels of these compounds were mainly concentrated in the outer shelf influenced by the Kuroshio Current. The patterns further prove that these ortho-substituted MeO-BDEs and OH-BDEs in marine sediments are natural compounds. Furthermore, alkenones also presented a seaward increasing trend. Statistical analysis shows that there are significant correlations between MeO-BDEs, OH-BDEs and alkenones, impling the potential of coccolithophorids for producing these natural compounds and their global distribution, especially in open oceans. Comparison between TOC and the ratio of 6-MeO-BDE47/6-OH-BDE47 suggests that TOC should be a potential controlling factor of the conversion between MeO-BDE and OH-BDE pairs.