| Polybrominated diphenyl ethers（PBDEs）are a class of additive-type brominated flame retardants（BFRs）and are also a class of persistent organic pollutants（POPs）.Sediments are important sources and sinks of PBDEs.Quanzhou is a typical coastal water-shortage city,and water security is an important constraint to the economic and social development of the city.As the main water source reservoir in Quanzhou,Shanmei reservoir accepts the pollutants released from the upstream water and the surrounding areas of the reservoir.After flowing through the main urban area of Quanzhou,Jinjiang receives the pollutants discharged from the urban area and injects the pollutants into Quanzhou Bay,which is an important wetland area in Fujian Province.Research on the pollution characteristics,environmental risks of PBDEs in this region and its influencing factors have theoretical and practical significance.We collected surface and columnar sediments from Shanmei Reservoir and Quanzhou Bay in different seasons to study the content of PBDEs,the total amount of PBDEs in sediments,the composition of the homologues,historical trends,spatial distribution,seasonal changes,and analyze their sources,evaluate their environmental health risks and also study the relationship between its spatial and temporal distribution and TOCand BC.The main conclusions are as follows:（1）The extraction methods of PBDEs in sediment are optimized and compared.The extraction efficiency of Acetone/Hexane（1:1）was the best in Soxhlet extraction.The temperature is the most important factors in microwave extraction,the optimum conditions were as follows:sample amount 5 g,extraction volume 40 ml,power 1400W,temperature 100°C,extraction time 20 min.Ultrasonic extraction,Acetone/Hexane（1:1）was chosen as the extraction solvent,liquid to solid ratio is the most important factor,the optimum conditions were as follows:liquid to solid ratio was40,extraction time was 50 mins extraction times was 3,and extraction temperature was 30℃.The extraction efficiency of Acetone/Hexane（1:1）was the best.The recovery of Soxhlet extraction（97.5%）was comparable to that of microwave extraction（95.9%）and that both were slightly better than ultrasonic extraction（90.4%）.（2）The median content of∑PBDEs（Summation of 22 PBDEs Congeners including BDE-209）in surface sediments of Shanmei Reservoir was 160.4 ng/g（10.6-1445.7ng/g）.The∑PBDEs pollution in the storage area come from the upstream water,the PBDEs in the storage area:wet season>normal season>dry season;the main pollution sources in the tail area come from the surrounding townships,and the tail area:dry season>wet season>normal season;The dam area is affected by the dam drainage,the wet season is low,The dry season is fairly parallel to the normal season,.The average content of PBDEs in surface sediments of Quanzhou Bay is 139.7 ng/g（24.3-7532.6 ng/g）.the pollution is more serious when Quanzhou Bay is near to the city.The areas with obvious sources of pollution are significantly higher in summer than in winter.The major homologues are all BDE-209（>84.5%）,and the main homologues in the∑21PBDEs are BDE-207,-206,-197,-99,and-47.The median content of PBDEs in the sediments of Shanmei Reservoir and Quanzhou Bay were78.0 ng/g（0.8-2002.8 ng/g）and 135.5 ng/g（6.5-1163.7 ng/g）,respectively.The columnar sedimentation rate of Shanmei Reservoir is 0.53 cm/yr.The vertical variation trend of PBDEs in the three water periods at each sampling point is roughly the same.The content of PBDEs in the lower layer of the storage area is higher,and the content in the lower layer of the tail area and the dam area is lower.The vertical change trend in the central area is not obvious.Quanzhou Bay area is close to the urban pollution sources,the vertical change trend of PBDEs is not obvious.The total amount of PBDEs in Shanmei Reservoir and Quanzhou Bay Area was 1.61 tons and11.30 tons,respectively,which was mainly due to the serious pollution and large water area in Quanzhou Bay.（3）The main source of PBDEs in the surface sediments of Sanmei Reservoir and Quanzhou Bay is the use of commercial Deca-BDE.Low BDEs are mainly derived from Deca-BDE by stepwise debromination degradation.The PBDEs degradation of Deca-BDE to Octa-BDE in the surface sediments of Shanmei Reservoir resulted in a faster degradation of N-bromodiphenyl ether to lower BDEs,degradation of Nona-BDE to Octa-BDE show different trends between different homologues.During the degradation of Octa-BDE to Penta-BDE,there was an accumulation of Hexa-BDE and Hepta-BDE.The contribution rate of PBDE degradation is more than 70%during the degradation of Penta-BDE to Tri-BDE.The degradation of PBDEs from decaBDE to Octa-BDE in the surface sediments of Quanzhou Bay is similar to that of Shanmei Reservoir.Consistently,during the degradation of Octa-BDE into Hepta-BDE,the rapid degradation of Hepta-BDE to lower BDEs was found,and the contribution to the degradation rate from Hepta-BDE to Tri-BDE is about more than 50%,which is lower than Shanmei Reservoir,the difference in contribution rates between the two regions is mainly due to the different water environment.（4）The potential risks of PBDEs in surface sediments from Shanmei Reservoir and Quanzhou Bay are high,Deca-BDE and Penta-BDE have ecological risks to sediment organisms in Shanmei Reservoir（Deca-BDE:RQ>1,high risk;Penta-BDE:0.01≤RQ<0.1,low risk）.When using the toxicological data of Eisenia foetida for ecological assessment,Penta-BDE and Deca-BDE in the surface sediments of Shanmei Reservoir have major ecological risks（Penta-BDE>1,Deca-BDE>1）.The former risk assessment was based on brominated PBDEs classification,the latter was classified by the composition of PBDE commercial product,thus the ecological risk of the two regions was more comprehensively evaluated by different classifications:Shanmei Reservoir and Quanzhou Bay surface sediments Deca-BDE and Penta-BDE have major ecological risks.The non-carcer risk values（95%confidence）in surface sediments from Shanmei Reservoir during the three periods are:children:0.540,teens:0.539,adults:0.328,non-carcer risks in sediments from Quanzhou Bay in winter and summer are:children:0.532,teens:0.513,adults:0.323,which are all less than 1;the risk vaule indicate that Shanmei Reservoir and Quanzhou Bay have lower risk of non-carcer risk.The cancer risk values（95%confidence）of BDE-209 in surface sediments from Shanmei Reservoir during the three water period are 0.74*10-10、0.39*10-10、2.05*10-10,The cancer risk values of BDE-209 in the surface sediment from Quanzhou Bay are 0.395*10-10、0.209*10-10、1.09*10-10,which is all lower than the baseline value(1*10-6-1*10-7)3-4 orders of magnitude;the risk vaule indicates that the BDE-209 has a lower carcer risk in both regions,However,the environmental health risks of debromination products need further study.（5）There were significant correlations between TOC,NonaBDE and DecaBDE in the wet and normal period of Shanmei Reservoir（r=0.667-0.738,p<0.05）.There was no correlation between PBDEs and TOC in the dry period,which may be due to the higher octanol water-partition coefficients of high bromine BDEs,they are more likely to be adsorbed in the particulates,Secendly,Compared to dry period,the upstream are relatively richer during the wet and normal period,and the main sources of pollution are the upstream water.There was no correlation between PBDEs and TOC due to pollution injection into Quanzhou Bay in winter and summer seasons;there was no correlation between PBDEs and BC in surface sediments of Shanmei Reservoir and Quanzhou Bay,and BC/TOC of Shanmei Reservoir was 0.31（0.14-0.49）.The source of BC is biomass combustion and fossil fuel combustion,which enter into the water through atmospheric deposition.The BC/TOC of Quanzhou Bay is 0.36（0.24-0.57）.The source of BC is biomass combustion and fossil fuel combustion,as some of the sites are close to industrial and densely populated areas,BC adsorption of PBDEs did not reach equilibrium in Quanzhou Bay.（6）The dam drainage of Shanmei Reservoir enters Jinjiang through Dongxi and passes through counties and cities in Quanzhou.Because of the injection of new pollution in the urban area,PBDEs content in the Jinjiang Estuary of the Quanzhou Bay in summer and winter is 13.3 and 1.4 times than that of the Shanmei Reservoir dam area.More than 90%of BDE-183 and BDE-154 have been degraded,and BDE-99 has accumulated.At the same time,the difference in DecaBDE/NonaBDE caused by the new pollution injection and the difference in water environment.By comparing the trends of PBDEs with TOC and BC of the two regions in winter and summer,it is found that the trends of PBDEs are consistent with TOC and BC in winter,but they are inconsistent in summer,which may be due to the effect of drainage of PBDEs in Shanmei Reservoir dam area in summer.In the summer,the upstream water is abundant,and the Jinjiang River flows through Quanzhou City.The injection of large amounts of pollutants may lead to incomplete adsorption of PBDEs by BC. |
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