Polybrominated Diphenyl Ethers In Sediments In The Aquatic Environments Of The Pearl River Delta And Yangtze River Delta

Polybrominated diphenyl ethers (PBDEs) were determined in surface sediments collected from the Pearl River Delta (PRD), the adjacent South China Sea (SCS) and the Yangtze River Delta (YRD), and in two sediment cores collected from the Pearl River Estuary (PRE). Spatial and temporal distributions, patter composition, sources, transport and fate were examined. Surface sediments form the PRE and the adjacent SCS were also analyzed for polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs), emphasizing on evaluating the inventories of PAHs and OCPs in the study area.The concentrations of EPBDEs (except for BDE-209) and BDE-209 ranged from 0.04 to 94.7 and from 0.41 to 7341 ng/g, respectively, and varied greatly spatially in the PRD region. Extremely high concentrations of BDE-209 (up to 7341 ng/g), with average concentrations of 890 and 1441 ng/g were observed in the Zhujiang and the Dongjiang Rivers, respectively, which were mainly influenced by local industrial waste discharges. PBDE concentrations were general very low in sediments from the Xijiang River, which runs through relatively undeveloped areas and possibly receive PBDEs from the east PRD industrialized region via atmospheric transport. However, high concentrations observed in sediments in Macao coastal region may be as a result of transport and redistribution of PBDEs from the PRE to this region but not local discharges. BDE-209 apparently was the predominant congener, which was 1-2 orders of magnitude higher than ZPBDEs. This may be due to the fact that technical deca-BDE is the dominant brominated flame retardants in China nowadays. Concentration of BDE-209 increased exponentially from the bottom (0.5 ng/g) to the top segment (13.5 ng/g), whereas SPBDEs decreased rapidly (3.46 - 0.15 ng/g) in sediment core 1# obtained from the eastern side of PRE. Rapid increasing trend for BDE-209 and slight declining but fluctuant trend for SPBDEs was observed in sediment core 2# taken from western side of PRE. The results may indicate the rapid increaseing demand of technical deca-BDE products and the decrease of consumption of technical penta-BDEs products in the PRD region.The PBDE (tri- to hepta-) vertical composition variety in core 1# may be attributed to the different commercial penta-BDEs mixtures used in city of Shenzhen in the past, the photochemical/microbial degradation of BDE-209 and/or the congener-specific migration in the sediment column after deposition. The deposition fluxes of PBDEs to the whole estuary were assessed with data of cores 2#, which ranged from 1.81 to 10.2 ng/cm~2 yr and 2.97 to 20.2 ng/cm~2 yr forΣPBDEs and BDE-209, respectively. The total burdens PBDEs in the estuary were approximately 8.2 tons, suggesting the significant influence of the rapid economic development of the PRD region to the estuarial system.The investigation of PBDEs in surface sediments of the YRD regions, anothor of the most developed regions in China, showed that PBDEs concentrations were generally in the low to moderate range in sediments around the world, ranging from nd to 0.55 ng/g with a mean value of 0.15 ng/g for SPBDEs and 0.16 to 94.6 ng/g with an average of 13.4 ng/g. The concentrations were much lower than those in sediments in the PRE region except several samples with high concentrations of BDE-209 that were possibly influenced by point sources. The general low to moderate PBDE levels found in the present study are presumably attributable to the small quantity of PBDE flame retardants, especially the technical penta-BDEs products, used in the region. However, such low PBDE levels may also be explained by the specific hydrodynamic conditions of the YRE and Hangzhou Bay: the coarse sediments, and the much low TOC content. Compared to published data acquired from other regions, PBDE congeners with less than four bromines were more abundant in the YRD region, which may likely be as a result of congener fraction among particles of different sizes during their transport.PAHs and OCPs in surface sediments in the PRE and northern SCS were also examined. Their distribution in the northern SCS showed that the riverine and estuarial discharge, instead of atmospheric deposition (both gas and particle fluxes) and other routes, was the main pathway of PAH and OCP inputs to the northern SCS, which were further confirmed by the extremely relatively high concentrations of perylene in all samples and principal components analysis (PCA) of PAHs. Results of linear regression showed that the riverine and estuarial discharge reach approximately 124～276 and 143～172 km from the estuary to the open sea. PAHs and OCPs burdens were evaluated in surface sediments of the estuary and continental slope. The results suggested that 631 and 1.9 t PAHs and OCPs, mainly originated from the PRD regions, were deposited in sediments of the PRE and 423 and 1.4 t in those of the studied northern SCS during the past 25 years. The PAHs inventories (kg/km~2) were approximately 10-fold higher than those of the Mediterranean basin. Presumably, sediments of the PRE and the northern SCS may have served as a significant reservoir of POPs from the PRD region and at the same time a potential source of POPs to the global oceans.