| Polyhalogenated carbazoles（PHCZs）are a kind of organic compounds in which the hydrogen atom on the carbazole ring is replaced by one or more halogen atoms（Cl,Br,I）.Due to their persistence,bioaccumulation and toxic effects similar to dioxins,PHCZs have become a new type of pollutant of great concern in the field of International Environmental Science.At present,it is widely detected in environmental samples such as air,soil,surface water,sediment,algae and fish.In this study,137 seawater and 122 sediment samples were collected from 103 stations in the Yellow Sea and East China Sea in wet and dry seasons respectively for the determination of carbazole（CZ）and 8 kinds of PHCZs:3-chlorocarbazole（3-CCZ）,2-bromocarbazole（2-BCZ）,3-bromo-9H-carbazole（3-BCZ）,3,6-dibromocarbazole（36-BCZ）,2,7-dibromocarbazole（27-BCZ）,3,6-diiodo-9H-carbazole（36-ICZ）,1,3,6,8-tetrabromocarbazole（1368-BCZ）.As another new pollutant,organophosphorus flame retardants（OPFRs）are ubiquitous in the environment and will eventually enter the marine sediments.In this study,the content,spatial distribution and ecological risk of seven kinds of OPFRs in sediment samples from the South China Sea were studied for the first time.This study provides rich basic data for clarifying the pollution status,diffusion behavior and ecological risk of PHCZs in the east Yellow Sea and OPFRs in the South China Sea.The specific research contents and results include the following aspects:（1）Distribution of CZ and PHCZs in water and sediments in wet and dry seasons in the Yellow Sea and East China Sea.In seawater,the total concentration of CZ and PHCZs in wet season was 0.09-16.66 ng/L,with a median of 3.21 ng/L,while in dry season,the total concentration of CZ and PHCZs was 1.17-56.38 ng/L,with a median of 6.42 ng/L.The main components of carbazole pollutants in seawater were CZ,3-CCZ and 27-BCZ.The composition of carbazole pollutants in sediments was mainly CZ,27-BCZ,36-BCZ and 36-CCZ.The content of PHCZs in sediments was significantly higher than that in seawater.In wet season,the concentration range of CZ and PHCZs was 0.13-13.31ng/g dry weight（dw）,while in dry season,the concentration range of CZ and PHCZs was 0.26-8.02ng/g dw.The high concentration points of CZ and PHCZs were mainly concentrated in the Yellow Sea cold water mass（YSCWM）and the north coast of the East China Sea.CZ andΣPHCZs show obvious seasonal variation trend.（2）Fugacity analysis of CZ and PHCZs in the Yellow Sea and East China Sea.Seawater sediment fugacity analysis shows that most PHCZs are in equilibrium in the wet season,and a few low halogenated PHCZs and CZ tend to diffuse from sediment to water.In dry season,most PHCZs are in equilibrium or deposited in sediments,and a few highly halogenated PHCZs are easier to be adsorbed in sediments.In addition,for most PHCZs,fugacity fraction decreases with the increase of the number of halogen atoms in the compound in the wet and dry seasons,indicating that PHCZs tend to precipitate into the sediment with the increase of halogen atoms.（3）Source analysis of CZ and PHCZs in the Yellow Sea and East China Sea.Spearman correlation test showed that there was also a strong positive correlation between the concentrations of CZ and PHCZs in seawater samples（wet season:r=0.984,p<0.01;dry season:r=0.743,p<0.01）.In sediments,there is not only a significant correlation between CZ and PHCZs（wet season:r=0.773,p<0.01;dry season:r=0.923,p<0.01）,but also a positive correlation between PHCZs and TOC（wet season:r=0.290,p<0.05;dry season:r=0.346,p<0.05）,which means that some PHCZs may have similar sources with CZ and may be derived from the halogenation of CZ.These unique temporal and spatial distribution patterns show that PHCZs in seawater and sediments of the Yellow Sea and the East China Sea are jointly contributed by terrestrial and natural sources.（4）Toxicity equivalence assessment of CZ and PHCZs in seawater and sediment samples from the Yellow Sea and the East China Sea.In seawater samples,the(（5）in the Yellow Sea and East China Sea in wet season was 0-0.1 pg TEQ/L(average:0.4×10-2 pg TEQ/L,median:0.2×10-2 pg TEQ/L),0.1 in dry season×10-2-3.4 pg TEQ/L(mean:0.3pg TEQ/L,median:2.8×10-2 pg TEQ/L).In sediment samples,the range of(（5）in wet season was 0.4×10-2-0.6 pg TEQ/g dw（average concentration:0.1 pg TEQ/g dw,median concentration:0.1 pg TEQ/g dw）,0.7 in dry season×10-2-0.2 pg TEQ/g dw(average concentration:6×10-2 pg TEQ/g dw,median concentration:4.8×10-2 pg TEQ/g dw).Among the seawater and sediments in this study,the high(（5）of 36-CCZ and 1368-BCZ deserve attention.（5）Due to the restrictions on the use of brominated flame retardants in recent years,organic phosphorus flame retardants（OPFRs）,as their substitutes,are widely produced and used all over the world.The concentration,spatial distribution and ecological risk of seven organophosphorus pesticides in sediment samples from the South China Sea were investigated for the first time.The total concentration range of all OPFRs was 2.5-32.3 ng/g dw,among which the concentration of trimethylphenyl phosphate（TCPs）was the highest.Compared with other regions in the world,the OPFRs in the South China Sea was at a medium level.The spatial distribution of OPFRs may be affected by nearshore currents,ship transport and river input.The risk factor（HQ）of opfrs was 0 to 3.2×10-2,indicating that OPFRs has negligible ecological risk in the sediments of the South China Sea.However,due to their continuous land-based input,these OPFRs need long-term attention in the future. |
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