From Source To Sink Of Polybrominated Diphenyl Ethers, One Group Of Persistent Organic Pollutants In The East China Sea

As a group of anthropogenic chemicals, persistent organic pollutants (POPs) could be finally stored in the marine environment by the runoff input and atmospheric deposition, and have harmful effects on the marine ecosystems and food security. The East China Sea (ECS), one of the largest marginal seas in the world, receives a large amount of POPs from the Yangtze River input every year. Besides, atmospheric outflow carries amount of continental pollutants from North China into the ECS by dry/wet deposition due to the East Asian monsoon. Therefore, understanding the source and sink of POPs in the ECS is essential to assess the regional/global cycle of POPs.As typical one group of POPs, polybrominated diphenyl ethers (PBDEs) have been widely used as flame retardants in the world. PBDEs can be easily escaped into the environment during material crushing because they are dissolved in the polymer without chemical bond. They are difficult to be degraded from the environment, tend to undergo long-range transport from the source places to the remote areas. The lipophilicity of PBDEs led them accumulated in organisms and produced toxic to the human beings and ecological system. PBDEs could enter to the ECS by Yangtze River input, land surface runoff and atmospheric deposition. More importantly, the ECS should be subjected to the pollutions of PBDEs because of the recycling center of e-waste boomed in the coast of Zhejiang province. However, there have been very limited studies on PBDEs in the ECS. In this work, comprehensive researches on the occurrence, sources and fate of PBDEs were examined in order to understand the process from source to sink of PBDEs in the ECS.The results in this study showed that the BDE-209 was the dominant congener detected in air, seawater and sediments in the ECS. BDE-47 and BDE-99 were the most detected congeners among other lower brominated PBDEs except BDE-209. This was consistent with the wide usage of deca-and penta-BDE technical mixture in China.Atmospheric samples were collected from a receptor site (Huaniao island) in the ECS to determine the occurrence and sources of PBDEs. The concentrations (particle plus gas) of BDE-209 and PBDEs (total 11 PBDEs without BDE-209) were 9.5±6.9 pg/m3 and 2.5±1.5 pg/m3, respectively. A distinct seasonal variation was observed for BDE-209 with higher level in winter and spring dominated by the northwesterly winds while lower concentration in autumn and summer when the southeasterly winds prevailed, suggesting the significant source contribution from continental outflow on BDE-209 in winter and spring. The highest concentration of ∑11PBDEs occurred in summer implied that there were other sources for ∑11 PBDEs beside continental outflow. The good correlations between BDE-209 and ∑11 PBDEs both in autumn and summer indicated a potential source of the low brominated PBDEs from photoproducts of deca-BDE in warm season.∑11 PBDEs volatilizated from the seawater were confirmed to be important contribution to the surrounding atmosphere in autumn.PBDEs were mainly concentrated in particle phases in winter, while in gas phases in summer. The lower brominated PBDEs were present mostly exclusively in the gas phase, whereas the higher brominated PBDEs were easily adsorbed by particle phases. The good correlations between OC with BDE-47,-99 and BDE-209 in autumn and summer suggested a significant role of OC in the occurrence of atmospheric PBDEs over ECS, especially for the higher brominated PBDEs.In this study, air and precipitation samples collected for one year as well as surface seawaters collected in autumn were used to estimate the dry (FD) and wet (FW) deposition as well as air-water exchange flux (FG) of PBDEs.The average FD of BDE-209 was 338.9±323.3 pg/m2/d with higher in winter and spring, while ∑11PBDEs was 46.0±24.7 pg/m2/d with the highest concentrations occurred in summer. The average Fw of BDE-209 and ∑11PBDEs were 2343.0 and 106.4 pg/m2/d, respectively. A distinct seasonal variation of Fw was observed with highest level in summer due to the abundant precipitation. The result showed that Fw was much higher than FD in the ECS,especially for the lower brominated PBDE congeners. Calculated FG of selected PBDEs congeners were -114.1,-68.2,-14.0,3.7 and 43.5 pg/m2/d for BDE-28,-47,-99,-100 and BDE-209, respectively. As a whole, the total flux (FD+FW+FG) were -84.8 and -46.4 pg/m2/d for BDE-28 and BDE-47,13.5,5.9 and 2632.2 pg/m2/d for BDE-100 and BDE-209, implying a dominant volatilization for BDE-28 and BDE-47 while atmospheric deposition for higher brominated PBDEs in autumn. The result showed that the ECS acted not only as a sink but also as a significant source for PBDEs in the atmosphere.PBDEs of sixty-three sediment samples from the coastal ECS, extending about 1000 km from the Yangtze River Estuary to the south, were measured. The levels of BDE-209 and ∑7PBDEs were 6.4±4.8 ng/g and 1.6±1.4 ng/g, respectively. The compositions and distribution of PBDEs suggest that the PBDEs in this area could be mainly from the coastal electronic waste dismantling/recycling and Yangtze River input. Meanwhile, there was a slight decrease for ∑7PBDEs level in sediments from the north to the south which could be attributed to their different solubility in water. The poor correlations between TOC, grain size of sediments with PBDEs imply that the PBDE distribution is more related to their land-based inputs rather than the sediment characters in the area. The coastal ECS is an important sink of PBDEs in the world with the total accumulation flux of BDE-209 and ∑7PBDEs were 5.6 t/yr and 1.9 t/yr, respectively.Historical pollution levels of PBDEs in sediment core would be very useful in understanding the impact of pollutant input on the environment. In this study, high-resolution sedimentary records of PBDEs deposition in the ECS have been revealed using the sediment cores from different mud areas in the ECS. The concentrations of BDE-209 and ∑8PBDEs were nd-842.0 pg/g and 6.2-140.8 pg/g in coastal mud area sediment core (C0803), respectively. The relative amount of PBDEs in mud area southwest to Cheju Isiand sediment core (FFJ103) were much lower than in coastal mud area with the value of nd-229.0 pg/g for BDE-209 and 4.6-49.1 pg/g for ∑8PBDEs. The trend of ∑8 PBDEs observed at C0803 is response to the different stage of economic development of the coastal cities of the ECS. Apparent deviations of BDE-209 from the expected time trend of regional economic development were observed, and it was coincident with the booming of the e-waste cycle industry in Zhejiang province. Due to the atmosphere long-range transport, the trend of BDE-209 and ∑8 PBDEs in FFJ103 could response to the regional emission history of PBDEs in the North and East China.