| Objective:Focusing“the source（waste residue）-non-biological media（soil）-biological media（vegetable）-health risks（human body）”causality chain of an e-waste disposal area,from a holistic perspective to explore the PCBs pollution characteristics,migration process and potential health risks,in order to put forward constructive guidance and advicefor the farmland soil using,vegetable planting and human activities and the dietary of intaking vegetables.Methods:Select a site for dismantling e-waste in a certain area,and three e-waste residues sample piled up next to the farmland soil were collected as point source pollution.At the same time,10 and 18（6 from oilseed cabbage,6 from green beans and 6 from chinese cabbage）samples were collected from the farmland soil and vegetables near the waste residue.The mass concentration of PCBs in waste residue,soil and vegetables were determined by high resolution gas chromatography-mass spectrometry.Excel in WPS 2019,IBM SPSS Statistics 21 and Graph Pad Prism 8were used to collate and analyze the data.The characteristics of PCBs pollution in waste residue-soil-vegetable system were studied by correlation analysis,bioconcentration factor and toxic equivalency factor.The potential health risks of human body’s comprehensive exposure to PCBs in soil and vegetables were assessed using the environmental health risk assessment model developed by the United States Environmental Protection Agency（USEPA）.Results:1.Characteristics of PCBs pollution in waste residue-soil-vegetable system（1）The total PCBs concentration levels in the waste residue was much higher than that of soil and vegetables,with the mean values of 11938.55 ng/g dw,45.54 ng/g dw and 11.51 ng/g dw,respectively.The total PCBs concentration levels in soil was higher than that of vegetables（P<0.05）.The total PCBs concentration levels of different vegetables:oilseed cabbage（8.43 ng/g dw）>green beans（2.40 ng/g dw）>Chinese cabbage（0.68 ng/g dw）,all P<0.05.There were no correlation between soil and vegetables of total PCBs concentration levels（all P>0.05）.The bioconcentration factors of PCBs in soil were 0.18,0.05 and 0.01 for oilseed cabbage,green beans and Chinese cabbage,respectively.（2）37 kinds of homologues were found in the waste residue and soil,and 33kinds of homologues were found in vegetables in the 37 kinds of homologues.All the7 indicative PCBs were detected in waste residue,soil and vegetables,but only 3dioxin-like PCBs were detected,namely PCB105,PCB118 and PCB156.The mean indicative PCBs concentrations of waste residue,soil and vegetables were 6116.16ng/g dw,21.42 ng/g dw and 4.69 ng/g dw,respectively.The mean mass concentrations of dioxin-like PCBs were 1277.40 ng/g dw,7.05 ng/g dw and 0.82ng/g dw,and the corresponding toxic equivalents were 3.83×10-2ng/g dw,2.12×10-4ng/g dw and 2.39×10-5ng/g dw,respectively.There was no correlation between the indicative and dioxin-like PCBs in soil and oilseed cabbage,green beans（P>0.05）,but there was correlation with some homologs in Chinese cabbage（P<0.05）.（3）The distribution of chlorine algebra in waste residue,soil and vegetables has a similar trend.The content and proportion of pentachlorobenzene was the largest,and the average content was 3633.54 ng/g dw,17.92 ng/g dw and 3.03 ng/g dw,respectively,accounting for 30.44%,39.36%and 26.32%.In general,the proportion of the highest is trichlorobenzene～pentachlorobenzene of low chlorobenzene,accounting for 77.92%,59.73%and 71.96%,respectively.The proportion of high chlorinated biphenyls is relatively small,with the chlorine algebra increased and the proportion decreased.2.Environment health risk assessment（1）For adults（male/female）and children exposed to soil and vegetables PCBs,the comprehensive hazard quotients were 0.480（0.448/0.511）and 0.864 respectively,which were all lower than the prescribed hazard quotients 1.Among them,the total hazard quotients for adults（male/female）exposed to soil PCBs were 1.88×10-2(1.81×10-2/1.94×10-2)and 8.96×10-2for children.The total hazard quotients of intaking three kinds of vegetables PCBs for adults（male/female）were 0.461（0.430/0.492）and 0.774 for children.（2）For adults（male/female）and children exposed to soil and vegetables PCBs,the comprehensive carcinogenic risks were 7.96×10-6(7.43×10-6/8.50×10-6)and3.62×10-6,which were all higher than the prescribed carcinogenic risk level of 1×10-6.Among them,the total risk of cancer for adults（male/female）exposed to soil PCBs were 6.45×10-8(6.20×10-8/6.67×10-8)and 8.19×10-8for children,which were all lower than the prescribed carcinogenic risk level of 1×10-6.The total carcinogenic risk of intaking three kinds of vegetables PCBs for adults（male/female）were 7.90×10-6(7.36×10-6/8.43×10-6)and 3.54×10-6for children,which were all higher than the prescribed carcinogenic risk level of 1×10-6.The carcinogenic risk of intaking oilseed cabbage PCBs was 6.56×10-6(6.11×10-6/7.00×10-6)for adults（male/female）and2.94×10-6for children.The carcinogenic risk of intaking green beans PCBs was1.26×10-7(1.17×10-7/1.34×10-7)for adults（male/female）and 5.69×10-8for children.The carcinogenic risk of intaking Chinese cabbage PCBs was 1.22×10-6(1.13×10-6/1.30×10-6)for adults（male/female）and 5.54×10-7for children.The carcinogenic risk level of intaking different vegetable PCBs of the population was ranked as follows:oilseed cabbage>Chinese cabbage>green beans.Conclusions:（1）E-waste dismantling activities have a great impact on the PCBs contents in local soil and vegetables.（2）Vegetables may have a certain absorption of PCBs in the soil and different vegetables have different PCBs accumulation capacity.（3）The non-carcinogenic risk of comprehensive exposure to PCBs in local soil and vegetables to human body is at an acceptable level.（4）The carcinogenic risk of comprehensive exposure to PCBs in local soil and vegetables to human body is at an unacceptable level.The carcinogenic risk for adults（male/female）is greater than that of children,and the carcinogenic risk of oilseed cabbage and Chinese cabbage were higher than that of green beans. |
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