Pollution Characteristics,Sources And Ecological Risks Of Polychlorinated Biphenyls (PCBs) In Surface Sediment Of Dongping Lake

Polychlorinated biphenyls?PCBs?as one kind of persistent organic pollutants which are highly toxic,difficult to degrade and can be enriched in organisms.Based on this,In this thesis,surface sediment samples of Dongping Lake were sampled and measured.studied the pollution characteristics of PCBs in the surface sediments of Dongping Lake,analyzed the composition characteristics of PCBs in the surface sediments of Dongping Lake and discussed the sources of pollution.The ecological risk assessment of polychlorinated biphenyls?PCBs?in surface sediments of Dongping Lake was carried out by using various evaluation criteria.The results showed that:?1?PCBs concentrations in surface sediments of 16 sampling sites in Dongping Lake ranged from nd to 605.9 ng·kg^-1,with an average of 126 ng·kg^-1.Compared with PCBs concentrations in other areas of China,PCBs concentrations in surface sediments of Dongping Lake were relatively low and pollution levels were relatively low.?2?The average pH value of surface sediments in Dongping Lake is 8.595,the average TOC?%?is 2.091 and the average salinity?%?is 0.026.It is found that the influence of TOC on PCBs is not obvious.The correlation analysis shows that PCBs in surface sediments of Dongping Lake have no obvious correlation with pH and TOC.Due to the difference of hydrological factors and human activities,the spatial distribution of PCBs in surface sediments of Dongping Lake shows a decreasing trend from the Dawen River estuary to the northwest.?3?PCBs in surface sediments of Dongping Lake are mainly heptachlorobiphenyl?66.72%?,followed by trichlorobiphenyl?11.11%?.According to the composition characteristics of PCBs in surface sediments of Dongping Lake,the content of high-chlorinated biphenyls is much higher than that of low-chlorinated biphenyls,which is caused by the difference of sources and properties of PCBs in surface sediments of Dongping Lake.PCBs in surface sediments of Dongping Lake are mainly high-chlorinated biphenyls,presumably from the combustion,release and import of wood and coal.The migration of polychlorinated biphenyls in capacitors,pollution caused by cement plants and electric furnace steelmaking plants around Dongping Lake and along Dawen River.However,principal component analysis of PCBs and 8 commercial Aroclors in surface sediments of Dongping Lake shows that the distribution of PCBs in the study area is quite different from that of common commercial mixtures,which further illustrates the complexity of the sources and influencing factors of PCBs in sediments.?4?In this study,the ecological risk assessment of PCBs in surface sediments of Dongping Lake was carried out by using the EPA method,Canadian sediment environmental quality standard SQG method and toxicity equivalent factor method?TEFs?.The results obtained by these three methods were consistent.The results of he EPA method?the Canadian Sediment Environmental Quality Standard SQG and Toxicity Equivalent Factor Method?TEFs?show that the ecological risk of PCBs in surface sediments of Dongping Lake is low,and the risk of harmful effects on organisms is also low.The results of this study can systematically and comprehensively analyze the pollution characteristics,composition characteristics,pollution sources and ecological risk assessment of PCBs in surface sediments of Dongping Lake.Hoping to prevent and control organic pollutants in Dongping Lake.The pollution status of organic pollutants to manage in South-to-North Water Transfer Project-East Route Project provides an important scientific basis.