Pollution Characteristics Of Polyhalogenated Carbazole And Brominated Flame Retardants In Harbor Seals Of The California

Polyhalogenated 9H-carbazoles(PHCZs)are commonly used in dyes,pharmace-uticals,photoconductors,and many other fields.However,studies on the environmental distribution,source and trend of PHCZs remain limited.Brominated flame retardants have been broadly applied in textiles,furniture,thermoplastics,electrical and electronic products.Main BFR chemicals include polybrominated diphenyl ethers(PBDEs)and alternative brominated flame retardants(NBFRs)that have been used to replace PBDEs.As some PHCZs and BFRs are persistent,bioaccumulative,toxic,and may be subjected to long range transport,investigation on their contamination in important aquatic ecosystems and potential effects on wildlife become critically needed.In this study,we investigated and determined PHCZs and BFRs in harbor seal(Phoca vitulina)blubber collected from coastal waters of seven California counties(Marin,Mendocino,Monterey,San Luis Obispo,San Mateo,Santa Cruz and Sonoma)in 2003-2016,including 11 PHCZs,21 PBDEs,and 15 Kind of NBFRs are detected in the samples.According to the measured concentration levels and composition of PHCZs,PBDEs and NBFRs in the harbor seals,the regional differences and temporal trends of these pollutants in 7 counties were investigated,and the possible causes of the differences were also investigated.The results showed that the concentrations of ?PHCZs in the harbor seals ranged from 0.36 to 84.4 ng/g lw(median 4.8 ng/g lw).The composition of PHCZs was mainly composed of 2,7-dibromocarbazole(27-BCZ,47.4%),followed by 1,8-dibromo-3,6-dichlorocarbazole(18-B-36-CCZ,19.5%),3,6-dichlorooxazole(36-CCZ,12.7%),3-chlorocarbazole(3-CCZ,6.6%)and 3,6-dibromocarbazole(36-BCZ,6.4%).The concentrations of ?PBDEs ranged from 24.2-3625 ng/g lw(median 179.6 ng/g lw),and the relative abundance of homologues was 2,2',4,4'-tetrabromodiphenyl ether(BDE-47,accounting for 72.4%),followed by decabromodiphenyl ether(BDE-209,14.1%),2,2',4,4',5-pentabromodip-henyl ether(BDE-99,5.3%)and 2,2',4,4',6-pentabromodiphenyl ether(BDE-100,4.6%).The total concentrations of ?NBFRs ranged from 21.3-4644 ng/g lw(median 144.5 ng/g lw)and the most abundant chemical was tetrabromo-6-chloromethylbenzene(TBCT,accounting for 70.3%),followed by 2-ethylhexyl-2,3,4,5-tetrabromobenzoate(EHTBB,20.3%).No significant spatial differences in the concentrations or compositions of ?PHCZs,?PBDEs and ?NBFRs were observed in harbor seals from seven counties.During different sampling periods(2003-2016),concentration of ?PBDEs and ?NBFRs exhibited significant decreases in harbor seals.?PHCZs also showed a downward trend.This study demonstrates the widespread distribution of PHCZs,PBDEs,and NBFRs in harbor seals in California,suggesting their enrichment in aquatic organisms and potential risks that may be widely distributed in aquatic environments and other aquatic organisms.This study investigated the concentration,composition,spatial distribution and possible sources of PHCZs,PBDEs and NBFRs in marine mammalian harbor seals,and provides data on the distribution and contamination of PHCZs,PBDEs and NBFRs in biological samples,especially marine mammals,and also provide data support for human exposure assessments of these types of contaminants to better analyze the impact of persistent organic pollutants on human health.