Study On Organochlorine Pollutants In Soil Based On Passive Sampling Technique

Compared with traditional monitoring analysis of sampling technology,passive sampling technique has incomparable advantages including high accuracy which can reflect the actual situation,simple operation and low price.Passive sampling technique is named as the "green" monitoring technology,but the practical application of this technology in China has rarely been reported.As important persistent organic pollutants(POPs),organochlorine pollutants(OCPs)in surface soil pose a serious threat to soil organisms and human health.Compared with other regions,OCPs concentration in soil from Tianjin is higher,but the data in the literature are total concentration of OCPs from traditional sampling analysis technology while bioavailable OCPs concentrations in soil from Tianjin has not been reported.This study tests two kinds of representative POPs in surface soil respectively in Dagang,a typical industrial production area of Tianjin and Xiqing an agricultural area,with the application of low density polyethylene(LDPE)and passive sampling technology,in 2017:bioavailable concentration of polychlorinated biphenyls(PCBs)and dichlorodiphenyltrichl-oroethane(DDTs)and makes a preliminary analysis on the spatial distribution of two kinds of pollutants,composition,pollution sources and the possible risk.The main conclusions are as follows:(1)According to the 99 surface soil samples in Tianjin,52 PCBs homologs were detected,and the bioavailable PCBs concentrations of PCBs in soil pore water and soil were respectively:0.085～0.81μg/L and 0.84～8.3μg/kg.PCBs content in Dagang is higher than that in Xiqing,and soil pore water concentrations of PCBs in these two districts are higher than surface water concentrations of PCBs at home and abroad,and bioavailable PCBs concentration significantly lower than the concentration of PCBs in the surface soil total at home and abroad.The PCBs in the surface soil of the two regions show obvious point source distribution characteristics,and the high concentration of industrial developed and densely populated areas is mainly composed of trichlorobiphenyls and tetrachlorobiphenyls,and the proportion of high chlorinated biphenyls is relatively low.According to the source analysis,PCBs in Dagang is similar to domestic PCBs products,and the composition of PCBs in Xiqing may be mainly affected by the nature of the soil and atmospheric deposition.(2)The concentration range of bioavailable DDTs in the surface soil of the Dagang and Xiqing area are respectively 0.18～12.93μg/kg and nd～89.20μg/kg,showing significant point source distribution.Contents around pesticide plants and DDTs related factories are higher,meanwhile mainly agriculture area Xiqing(average 20.23 μg/kg)is higher than predominantly industrial Dagang(average 2.96 mu g/kg);The concentration of pp ’-DDT and pp’-DDE of DDT derivatives is high,accounting for 90%of the total.Compared with 20 years ago,DDT residues increased and degradation rate slowed down.Source analysis shows that the DDTs in Xiqing mainly come from historical residues,while that in Dagang may be mainly derived from atmospheric deposition,but it cannot exclude the possibility of new DDTs product input.The ecological risk assessment and health risk assessment on PCBs and DDTs in the surface soil in Tianjin show that:bioavailable PCBs concentrations of surface soil in Xiqing and Dagang are less than low toxicity effect value ERL.Toxic equivalent calculation shows the toxic equivalent ΣTEQ of PCBs in the soil pore water in the topsoil of Dagang and Xiqing are 0～1.753×10-3μg/L and 0～0.481 ×10-3p.g/L respectively which is lower than that in domestic and foreign surface water,but the possibility of risk can’t be ignored.According to DDTs residues level,The bioavailable DDTs concentration of more samples exceeded the low toxicity value ERL,but it was less than the high toxic effect value ERM,and the risk probability would be between 10%and 75%,which must be taken seriously.Health risk assessment on PCBs and DDTs for adults and children showed that both the oncogenic risk index and the non-carcinogenic risk index were below the standard value,with little risk.To sum up,the monitoring and control of OCPs in surface soil of Tianjin still needs to be strengthened to prevent future ecological and health risks.