Residues And Exchange Of Multiple Environmental Media Interfaces Of Chlorinated POPs In Mussel Culture Area Of Zhoushan Sea,Zhejiang Province

Persistent organic pollutants（POPs）can be widely found in various environmental media due to their persistence and long-distance migration,even in remote areas such as polar regions.Most semi-volatile persistent organic pollutants,such as polychlorinated biphenyls（PCBs）and organochlorine pesticides（OCPs）,migrate,settle and reach the Marine environment far from land worldw.In the research of this paper,we collected soil,water and atmospheric samples from a remote site（Huaniao Island）in the Yangtze River Estuary,analyzed the concentration,composition characteristics and source analysis of HCHs,DDTs and PCBs,and further used fugacity The model studies the characteristics of soil-air exchange and water-air exchange of chlorinated POPs in the study area,and clarifies the environmental behavior and migration trend of target pollutants.（1）The concentration level of∑HCHs in the soil of the study area was 0.176-10.4ng/g,with an average value of 1.48 ng/g,which was at a low level.The isomer concentrations of HCHs were ranked as follows:β-HCH>α-HCH>γ-HCH,andβ-HCH was dominant in most soil samples.The results of source analysis showed that the residues of HCHs in soil were mainly derived from the historical use of industrial 666.The specific concentration level was 0.739-117 ng/g,and the mean was 23.1 ng/g.Source analysis showed that there was a new DDT pesticide source input in this area recently,and DDTs were mainly metabolized by aerobic metabolism,which was related to soil porosity and the oxygen content of the environment.The soil was dominated by low-chlorinated PCBs congeners,including tri-chlorinated PCBs and tetra-chlorinated PCBs,and high-chlorinated PCBs were also enriched in the soil.（2）The concentration levels of∑HCHs in the atmosphere in winter in the study area ranged from 8.28 to 67.2 pg/m³ with an average of 25.2 pg/m³,and in summer from 10.4to 78.9 pg/m³ with an average of 26.3 pg/m³.In the winter atmosphere,α-HCH is the main composition of each isomer,while in the summer atmosphere,γ-HCH occupies the highest proportion.Source analysis showed that the atmosphere was polluted by different sources in winter,and the HCHs pollution in the summer atmosphere came from historical residues.The specific concentration levels are:0.3-9.21 pg/m³ in winter,with an average value of 2.57 pg/m³,and 0.542-198 pg/m³ in summer,with an average value of 34.4pg/m3.The concentration range of∑₄₁PCBs in the atmosphere in winter was 10.1-174pg/m³,with an average value of 72.9 pg/m³,and the concentration range of∑₄₁PCBs in summer was 57.1-658 pg/m³,with an average value of 282 pg/m³.Whether it is winter or summer,the composition characteristics of PCBs homologues in the atmosphere are mainly composed of Tri-CBs and Tetra-CBs.Source analysis showed that PCBs in the atmosphere may be derived from unintentional emissions of by-products containing PCBs.（3）The concentration level of∑HCHs in the water body in the study area was 220-1762 pg/L,with an average value of 619 pg/L,and the HCHs in the water body was at a low level.Among them,α-HCH dominates in most water samples.The results of source analysis showed that HCHs pollution in water bodies mainly came from historical residues.The concentration levels of∑DDTs in the soil ranged from 68 to 295 pg/L,with a mean value of 134 pg/L.The source analysis showed that the DDTs pollution in the water body all originated from the historical residual accumulation,and mainly anaerobic metabolism.The concentration range of∑₄₁PCBs in water was 8.24-51.5 pg/L,with an average value of 29.3 pg/L.The congeners of PCBs in water are mainly low-chlorinated PCBs congeners,including Tri-CBs and Tetra-CBs,which are consistent with the historical use of PCBs in my country.（4）The concentrations of∑DDTs in mussels in culture areas ranged from 168 ng/g lw to 899 ng/g lw,with an average of 482 ng/g lw.The dominant group of HCHs in mussels wasβ-HCH.The concentration level of∑DDTs in mussels ranged from 168ng/g lw to 899 ng/g lw,with an average of 482 ng/g lw,indicating that DDTs was the main component of OCPs in mussels.The dominant components of DDTs in mussels were p,p’-DDE;The concentrations of∑PCBs in mussels ranged from 10.4-34.4 ng/g lw to 20.9 ng/g lw.The indicator value of∑₇PCBs was 31-53%of the total PCBs,which provided a good guidance for monitoring the concentration of PCBs in mussels.Among them,the main distribution of Penta,Hexa and Hepta-CBs∑₄₁PCBs total concentration,which is mainly attributable to the use of technical products and PCBS physical and chemical properties such as homolog selection of metabolic differences.（5）The soil-air exchange fugacity fraction results show that the HCHs and DDTs in the current study area are mainly in the state of volatilization from the soil to the atmosphere,and the soil is still the secondary source of OCPs in the atmosphere;in addition,most of the sampling points PCBs are in the state of deposition from the atmosphere to the soil.The size of the fugacity fraction is related to the molecular weight of PCBs,that is,it increases with the increase of molecular weight.The fugacity score in winter is higher than that in summer.（6）The results of the water-gas exchange fugacity fraction show that,regardless of OCPs or PCBs,the current study area is in a state of equilibrium or volatilization from the water body to the atmosphere,and the water body is the secondary source of chlorinated persistent organic pollutants in the atmosphere;in addition,the fugacity fraction in winter It is higher than that in summer.