Sources And Distribution Of Hydroxylated And Methoxylated Polybrominated Diphenyl Ethers In Sediments From The East China Sea And Yellow Sea

Occurrence and sources of hydroxylated (OH-) and methoxylated (MeO-)polybrominated diphenyl ethers (PBDEs) are of considerable environmental concernbecause of their potential biological toxicities and worldwide distribution. Researchbased on radiocarbon abundance analysis and laboratory exposure studies suggest thatthese compounds could originate from natural process in the ocean. However,considerable debate with respect to their main natural producers still continues.Furthermore, few reports to date have been referred to their occurrence, sources anddistribution in marine abiotic enviroments despite large numbers of studies on marineorganisms have been reported.In this study, the contents, distribution and sources of OH-/MeO-BDEs in surfacesediments and two sediment cores from the Southern Yellow Sea (SYS) were studied.Out of9MeO-BDEs and10OH-BDEs, only6-MeO-BDE-47,2’-MeO-BDE-68,6-OH-BDE-47and2’-OH-BDE-68were detected as the predominant congeners inmost of sediment samples. The individual contents of these OH-/MeO-BDEs insediments from the SYS were much higher than those in Liaodong Bay, White Lakeand Kootenary River. The spatial distribution of OH-/MeO-BDEs in surfacesediments all presented a seaward increasing trend, differing from someanthropogenic organic pollutants. And the historical records in two sediment coresshowed OH-/MeO-BDEs in both cores began to increase rapidly since the1950s, withtheir detections from the bottom (~1800s) were prior to the production of PBDEs(1960s). Overall, the spatio-temporal distribution of OH-/MeO-BDEs in sedimentsfrom the SYS suggest they maily originate from natural origins rather than artificialPBDEs. Additionally, comparisons between total organic carbon (TOC) and OH-/MeO-BDEs in all sediment samples indicate TOC is a potential factorinfluencing the distribution and accumulation of OH-/MeO-BDEs in the SYS. Theinterconversion of6-MeO-BDE-47and6-OH-BDE-47was indicated to occur in theSYS sediments by their similar spatio-temporal trend and significant correlationbetween their contents. Significant relations and similar spatio-temporal trendsbetween most of OH-/MeO-BDEs and phytoplankton biomarkers as well as marineorganic matters (MOM) indicators of ΣA+B+D (total contents of phytoplanktonbiomarkers) and MTOC (marine total organic carbon) in both surface sediments andtwo sediment cores further imply that a majority of OH-/MeO-BDEs in sedimentsfrom the SYS are natural compounds produced by phytoplankton.Also, we have determined the contents of MeO-BDEs, OH-BDEs and the mainphytoplankton biomarkers in surface sediments and two sediment cores collectedfrom the East China Sea (ECS). Only6-MeO-BDE-47,2’-MeO-BDE-68, and6-OH-BDE-47were detected in surface sediments, while these OH-/MeO-BDEs wereidentified as the predominant congeners in both two cores. The individual contents ofMeO-BDEs in ECS sediments were comparable to those in SYS but much higher thanthose in Liaodong Bay, White Lake and Kootenary River, while the individualcontents of OH-BDEs in sediments from the ECS were lower than those in SYS butcomparable to those in Liaodong Bay. Spatial patterns of OH-/MeO-BDEs in surfacesediments all presented a seaward increasing trend and higher levels of thesecompounds were mainly concentrated in the outer shelf influenced by the KuroshioCurrent. Furthermore, sedimentary records of OH-/MeO-BDEs in two cores showedthat these compounds have been presented since the1920s prior to theproduction/usage of PBDEs. Such spatio-temporal patterns indicate thatOH-/MeO-BDEs in ECS sediments are natural compounds. Similar distribution andsignificant correlations were observed between6-MeO-BDE-47and6-OH-BDE-47inboth surface sediments and two cores, indicating their interconversion in the ECSsediments. Sedimentary TOC was suggested to be a potential factor to influence theinterconversion of6-MeO-BDE-47and6-OH-BDE-47, and to control the residuefeature of OH-/MeO-BDEs in sediments from the ECS. In addition, the similar distribution and significant correlations between most of OH-/MeO-BDEs andphytoplankton biomarkers suggest possible production of these natural compounds byphytoplankton, corresponding to significant relations between these compounds andMOM indicators of ΣA+B+D and MTOC in sediments from the ECS. Comparisonsbetween the content ratios of6-MeO-BDE-47to2’-MeO-BDE-68and brassicasterolto dinosterol in both surface sediments and two cores indicate that the signature ofMeO-BDEs is presumably controlled by phytoplankton community structure.Laboratory incubation experiments of Chaetoceros curvisetus, Prorocentrumdonghaiense and Emiliania huxleyi have been also conducted, and the detections of2’-MeO-BDE-68and6-MeO-BDE-47in these microalgae, with their contents rangingfrom15.1to37.1pg/g dw and10.3to33.6pg/g dw, further prove that phytoplanktoncan indeed produce MeO-BDEs. These results suggest that OH-/MeO-BDEs in thesediments from the ECS are mainly natural compounds produced by phytoplankton.