Chlorinated Polycyclic Aromatic Hydrocarbons In Surface Sediment From Maowei Sea, China

With the rapid development of economy of Guangxi, surface sediment has become an important factor for eco-environmental quality in Maowei Sea. Combined with the relevant domestic and international research, we made the systematic study for the concentration level, pollution distribution characteristics, potential sources, toxicity equivalent analysis and the pollution toxicity contribution of target contaminant in surface sediment samples obtained from Maowei Sea in April, 2014. Two provenance analysis methods were used to analyze chlorinated polycyclic aromatic hydrocarbons（Cl PAHs）, which provided more details to the sources contribution of environmental concentration and toxicity of Cl PAHs. Research conclusions are as follows:（1） In this study, Maowei Sea was divided into M, K, S and J four areas according to the geographical features and 35 sample positions were chosen. In the surface sediment samples collected（n = 35）, 18 of 20 target Cl PAHs were detected; indicating that Cl PAHs were already widely present in the surface sediments in this study area. The concentration range of ΣCl PAHs was 0.31 9.64 ng/g dw and the average value was 3.21 ng/g dw. 6-ClBaP and 9-Cl Phe were found with the highest average concentration of chlorinated PAHs in surface sediments in this study, which was consistent with research both at home and abroad. In addition, 9-Cl Phe was detected in all samples, and the average concentration was as high as 1120.39 pg/g dw, which was higher than other chlorinated PAH homologues. Combined the feature of topography, industry framework and pollution characteristics in Maowei Sea with comparative analysis based on some existing small amount of literature about surface sediments, we speculated that the concentration level of Cl PAHs in surface sediment of Maowei Sea belonged to the middle in the world. In this study, the total concentration of 18 Cl PAHs varied widely with the different sampling points, which was related with special landform and different pollution sources nearby in Maowei Sea. High concentrations of ΣCl PAHs in surface sediments were mainly found in the J, K and some sampling points in S area. K region with the highest total average concentration（5.36 ng/g dw）, followed by J area（4.22 ng/g dw） and M zone was the lowest（2.11 ng/g dw） one; indicating that the location of surface sediment had an important influence on the spatial distribution of Cl PAHs. Through factor analysis, we surmised that petrochemical complex material, cement factory emissions, fuel combustion and urban sewage discharge were possible reasons for the high concentrations of ClPAHs.（2） This study used REPBa PEC50/60 to standardize Cl PAHs’ toxicity equivalent, and then calculated the total toxicity equivalent of Cl PAHs. The dioxin-like total toxicity equivalent for Cl PAHs（TEQCl PAHs） was 601.68 pg TEQ g-1 and monomer toxicity equivalent ranged from 2.32 to 185.97 pg TEQ g-1. TEQ of the Cl PAHs homologue ranking as: 6-Cl Chr（30.91%） > 3,9,10-Cl3Phe（18.01%） > 7-Cl Ba A（15.77%） > 9-Cl Phe（5.59%） > 9,10-Cl₂Phe（5.17%） > 6-ClBaP（4.33%） > 8-ClFlu（4.32%） > 7,12-Cl₂ Ba A（2.53%） > 3-ClFlu（2.31%）. Major carcinogen is 6-Cl Chr and 3,9,10-Cl3 Phe. Compared with domestic and foreign research, it showed that Cl PAHs toxic pollution levels on the environment in Maowei Sea was still relatively moderate.（3） In this study, 6-ClBaP/1-ClPyr, 3-ClFlu/1-ClPyr, 6-ClBaP / 3-ClFlu and 1-ClPyr / 3-ClFlu were selected as the criterion to estimate the sources of Cl PAHs. Internationally characteristic ratio method was used in this article and we found that Cl PAHs might come from motor vehicle exhaust, waste incineration, coal burning and other industrial chemical production sources, namely, incomplete combustion emissions from the incinerator, traffic exhaust and combustion of chlorine-containing materials in surface sediments of Maowei Sea in Guangxi.（4） Using the PMF model, the source apportionment of Cl PAHs and the contribution of each source of Cl PAHs in surface sediment of Maowei Sea in Guangxi was obtained in this study, results showed that traffic-related emissions, petrochemical plants mixed emission of pollutants, forest and coal combustion and mixed sources（including daily wastewater emissions and solid waste emissions from petrochemical plants and urban） were respectively with the portion of 14.8%, 18.6%, 30.4% and 36.2% for source contribution to the concentration of Cl PAHs. Although PMF model has been widely used in environmental analysis, it has not been reported about source distribution of Cl PAHs using this positive definite matrix model in surface sediments of Maowei Sea in Guangxi. In order to better describe the toxicity of Cl PAHs, this study combined a positive definite matrix factorization model with TEQ concentrations to make the quantified assessment of Cl PAHs’ toxicity equivalent contribution values from different sources（TEQcontribution）. The results showed that the traffic related emissions（0.47 pg TEQBa P g-1）, petrochemical factory complex emissions（0.92 pg TEQBa P g-1）, trees and coal combustion（1.06 pg TEQBa P g-1） and mixed source（2.94 pg TEQBa P g-1） to Cl PAHs’ toxic effect was approaching, so for this, pollution control and governance was needed to improve the quality of surface sediment from Maowei Sea in Guangxi.