Source Apportionment And Potential Risk Assessment Of PAHs And OCPs In Soils Of Shenyang North New Area

Polycyclic aromatic hydrocarbons(PAHs)and organochlorine pesticides(OCPs)are typical persistent organic pollutants in the soil environment,which pose a significant threat to the ecological environment and human health.The intensification of human activities and the dense industrial distribution in the Shenyang North New Area(SNNA),the typical area of rapid urbanization and industrialization,may lead to serious environmental problems.In this study,we collected the surface soil samples of the SNNA and analyzed the occurrence level,composition characteristics,main sources and potential risks of PAHs and OCPs in the soil so as to make clear the distribution and environmental behavior of PAHs and OCPs in the process of urbanization,and to provide the basic information for the formulation of regional pollutant control and pollution remediation policies.Results showed that the content of PAHs and OCPs in different soils of the SNNA was at the low pollution level,and the pollutant contents in different sampling sites were different.The pollutant contents decreased gradually from the urban traffic density area,to the urban junction facilities farmland,to the rural surrounding arable land,to the ecological protection zone,indicating that the content of PAHs and OCPs in soil was affected by urban traffic and modern industry and agricultural production.With the increase of distance from the southern city,the proportion of high-ring PAHs from vehicle exhaust and fossil fuel combustion reduced gradually and the proportion of low-ring PAHs from incomplete biomass combustion increased.HCHs and DDTs had similar spatial distribution patterns,and the residual population in the eastern and southern regions is generally higher than that in the middle and northern farmland and the northwest ecological reserve.The main source of PAHs in the surface soil of SNNA was identified as fuel combustion and oil spill by the characteristic ratio method in the soil.Factor analysis/multiple linear regression(FA/MLR)and positive definite matrix factorization model(PMF)were similar,but there were some differences.The results of FA/MLR analysis showed that industrial coal and motor vehicle exhaust gas was the main source of PAHs(contribution rate is 79.6%),oil leakage and coke oven emissions(16.2%)were lower,biomass fuel combustion contribution rate was the lowest(4.2 %).The results of PMF analysis showed that the contribution rate of biomass burning was the highest(31.7%).The identified fossil fuel combustion source was analyzed as 3 parts including coal source(23.7%),diesel combustion(8.1%),and gasoline combustion(17.5%).The contribution rate of oil spill sources was relatively low(19.0%).HCHs in the soil were mainly derived from the use of lindane,such as the paddy fields of middle study area and urban green space.DDTs were mainly derived from the use of early pesticides residues,such as forest areas in the eastern region.The Nemerro pollution index of PAHs in most samples(64.4%)in SNNA was at no pollution or light pollution level.The toxic equivalent of PAHs was also at a low level compared with other studies,indicating that the potential ecological threat of PAHs was low.The residual HCHs in the soils were lower than the ecological risk assessment values,which indicated the soils in SNNA were at low risk level.The DDTs in the soil might pose adversely effect on the creatures in the study area,but the ecological risks were lower.The results of the exposure model showed that the total risk index for non-carcinogenic and carcinogenic pollutants was lower than the acceptable standard value,indicating a lower risk to human beings.The risk of cancer exposure in three way followed the sequence of ingestion> skin contact> respiration,and carcinogenic risk to adult was higher than that to child.