Pollution Characteristics,penetration Behavior And Ecological Risk Assessment Of Short-chain And Medium-chain Chlorinated Paraffins In Soils In Typical Agricultural,Industrial And Ecological Demonstration Areas In Shanghai

Chlorinated Paraffins（CPs）are complex industrial mixtures of n-chloroalkanes,which are widely detected in the atmosphere,soil,water and sediments and various environmental media,with a wide range of pollution.Soil is an important"reservoir"and"source of secondary pollution"for persistent organic pollutant pollution.Although there are many papers on the pollution characteristics of CPs,Research on pollution penetration and ecological evaluation of short-chain（SCCPs）and medium-chain chlorinated paraffins（MCCPs）in soil is limited.In this thesis,Shanghai,the central city of the Yangtze River Delta,was used as the research area.A total of 138 soil samples were collected in Songjiang Agricultural District,Qingpu Industrial area and Dianshan Lake Ecological Demonstration area,including surface soil and column core samples（0～15,15～30,30～45 cm）.The SCCPs and MCCPs in the samples were analyzed qualitatively and quantitatively by using the ultrasonic extraction,one-step purification of the composite packing column coupled with GC-ECNI-LRMS.The pollution level,composition characteristics,vertical distribution characteristics and ecological risk assessment of SCCPs and MCCPs in soil were studied,basic data and scientific references for CPs pollution control,migration patterns and ecological risks were provided.The results are as follows:（1）The contents of SCCPs and MCCPs in the surface soil of Songjiang Agricultural District were 52.58～237.56 ng/g and 417.21～1690.82 ng/g,respectively.C₁₀Cl_5~10（33.70%）and C₁₄Cl_5~10（50.90%）were the predominant carbon congener groups,SCCPs(Cl_5~7)（64.90%）and MCCPs(Cl_6~7)（48.80%）were the main chlorine congener groups.The vertical distribution demonstrated that the content of SCCPs were relatively uniform along the soil column,and it is not significant（p>0.05）.The content of MCCP congener groups decreased exponentially,significantly（p<0.01）,with the carbon chain homologues in the upper,middle and bottom layers were 60.50%,25.40%and 14.10%of the total abundance of MCCPs,respectively.The results showed that the shorter carbon chain(C_10~13)and lower chlorine(Cl_5~7)congener groups have stronger penetration potential and are easier to transport along the soil column.Principal component analysis showed that SCCPs and MCCPs may have different sources,which may be related to environmental conditions,human activities,and the differences of production and use of CPs products in surrounding areas.The risk quotient method showed that the RQ values of SCCPs and MCCPs in soils were 0.010-0.045 and 0.015-0.060,respectively,which indicated a low ecological risk（0.01-0.1）.The current content will not pose a hazard to soil organisms.The daily human exposure values of children and adults were estimated through the human exposure model,the CPs daily exposure levels of children and adults were no more than Tolerable Daily Intake（TDI）（10μg/（kg·d））,suggesting an absent risk caused by non-dietary exposure.With the production,use and storage of a large number of industrial CPs in recent years,environmental pollution and health risks in non-industrial areas deserve further attention.（2）The contents of SCCPs and MCCPs in surface soil of Qingpu Industrial Area were 60.7～977.1 ng/g and 370.9～10712.7 ng/g,respectively.Compared with agricultural areas,the content of CPs was higher.C₁₀Cl_5~10（30.40%）and C₁₄Cl_5~10（50.4%）were the most predominant carbon congener groups,SCCPs(Cl_7~8)（45.40%）and MCCPs(Cl_7~8)（50.30%）were the main chlorine congener groups.Similarly,the vertical distribution characteristics showed that only the content of MCCPs changed significantly（p<0.01）,with the carbon chain homologues in the upper,middle and bottom layers were 50.40%,30.50%and 19.10%of the total abundance of MCCPs,respectively,indicating low CPs with chlorinated short carbon chains have stronger soil vertical transport capacity.Pearson correlation analysis showed that there was not a significant relationship between the contents of CPs and TOC（p>0.05）.Principal component analysis showed that the sources of CPs are not the same sources.Except for the C₁₇-MCCPs homologues,the SCCPs and MCCPs(C_14~16)may have the same sources,and the contribution rate of the chlorine homologues is different,which may be related to the industrial production,use and transportation process.Risk quotient model showed that the RQ values of SCCPs and MCCPs in the soil were 0.011-0.185and 0.013-0.383,respectively,at a medium risk level（0.01-0.1）,indicating that the content of CPs will cause a certain degree of harm to the local biota.The daily exposure values of children and adults estimated by the human exposure model in industrial area is higher than the agricultural area,but lower than the TDI,indicating that the potential risk caused by non-dietary exposure in the industrial area is more serious than that in the agricultural area,although it is not yet harmful to human health.The results will improve our understanding of CP pollution in industrial area and support the development of measure to decrease the amounts of possible CPs released from industrial areas.（3）The contents of SCCPs and MCCPs in surface soil of Dianshan Lake Ecological Demonstration Area were 39.73～406.10 ng/g and 273.13～1908.30 ng/g,respectively.The contamination was higher than the agricultural area,lower than the industrial area in this study.Correlation analysis found that there was a positive correlation between the contents of SCCPs and MCCPs（R=0.90,p<0.01）.C₁₀Cl_5~10（28.30%）and C₁₄Cl_5~10（42.6%）were the most predominant carbon congener groups,SCCPs(Cl_7~8)（42.90%）and MCCPs(Cl_7~8)（46.0%）were the main chlorine congener groups.The proportion of carbon chain homologues was as follows:C₁₀>C₁₁>C₁₃>C₁₂;C₁₄>C₁₅>C₁₆>C₁₇,just like agricultural and industrial areas,the low chlorinated and short carbon chain components are the predominant homologues.Principal component analysis showed that the sources of CPs are not the same sources.Except for the C₁₁-MCCPs homologues,the SCCPs and MCCPs have the same sources,and the contribution rate of the chlorine homologues is different.Risk quotient method showed that the RQ values of SCCPs and MCCPs in the soil were 0.009-0.07 and 0.007-0.08,respectively,which were at a low risk level（0.01～0.1）.The daily exposure values of children and adults are significantly lower than the TDI,indicating that there is a lower health risk in this area,and the potential ecological risk caused by cross regional transmission of CPs cannot be ignored.