Occurrence Characteristics And Risk Assessment Of Short Chain Chlorinated Pafaffins(SCCPs) In Typical Urban Soils Of Yangtze River Delta

Short-chained chlorinated paraffins(SCCPs,C₁₀-C₁₃),as a kind of widely used mixed chlorinated industrial product,has been detected in the atmosphere,soil,various biological tissues,even in human blood,placenta,and maternal and infant cord blood media,and has been included in the control A appendix to the Stockholm Convention in 2017.At present,there are more and more reports on the occurrence and migration of SCCPs environment,and a large number of basic data have been accumulated.The Yangtze River Delta?YRD?is one of the most developed economic zones in China,where rapid economic development and industrialization have led to a series of environmental problems,which have been identified by previous studies on persistent organic pollutants?POPs?in the region.A number of studies on wildlife CPs exposure have been conducted in the Yangtze River Delta region.However,there is a lack of CPs data in the surrounding environment.Therefore,further research on the level of CPs in this region is needed urgently.It is helpful to further understand the content distribution of SCCPs in environmental media,assess regional differences and dynamic trends,provide scientific reference for SCCPs pollution monitoring,health prevention,control,and provide reference for the green and healthy development of the Yangtze River Delta and China's promotion of global environmental governance.In this study,we selected the surface soil samples as the research object to explore the occurrence characteristics and risk assessment of SCCPs in typical cities of the Yangtze River Delta.The main results obtained are as follows:?1?SCCPs have been detected in all levels of the topsoil in Nanjing,Su-Xi-Chang,and Ningbo Metropolitan,with a detection rate of 100%.The average concentration of SCCPs in each sampling area is distributed in the following order:Ningbo Metropolitan?577.83ng/g?>NanjingMetropolitan?179.55ng/g?>Suzhou-WuXi-Changzhou Metropolitan?144.13 ng/g?>Hefei Metropolitan?21.95 ng/g??Hangzhou Metropolitan?21.17 ng/g?.The high pollution point of individual direct emissions makes the whole high average,and the concentration distribution of SCCPs is unbalanced.?2?Industrial land and green belt are the landuse types that are heavily polluted by SCCPs in typical urban soils in the Yangtze River Delta.Industrial land is the main source and sink of POPs the environment.Few high-value forest land samples have been dumped by the surrounding industrial waste,road dust and utilization of sewage sludge to forest land treatment and utilization,urban sludge compost forest land complex pollution.?3?The high-value samples of typical cities in the Yangtze River Delta are mainly affected by industrial activities and urbanization,which are mainly caused by point source pollution,and mainly composed of long carbon chain components.The low-value sample points are affected by the distance from the source,and meteorological factor conditions,mainly from atmospheric migration.the sample point of homogeneous composition of the carbon chain,the migration ability of the“light”component and the deposition of the“heavy”component reached a relatively saturated state.C₁₂2 is the least proportion of carbon homologues SCCPs the entire Yangtze River Delta.In the samples with homogeneous carbon chain,the migration ability of the“light”component and the deposition of the“heavy”component have reached a relatively saturated state.C₁₂ is the carbon homologue with the least proportion of SCCPs in the Yangtze River Delta.?4?Using principal component analysis to obtain the preliminary analysis of the potential sources SCCPs in each functional area,the effluent from the municipal sewage treatment plant may lead to a relatively high concentration of SCCPs in the green belt in this study.The composition of SCCPs monomers in residential areas tends to be long carbon chains,high-chlorine substituted,may be derived from plasticizers or sealants in plastic products that are difficult to degrade during frequent human activities.The SCCPs concentration of some farmland sites is about10³ ng/g,which may be from plastic sheds or plastic bags mixed with soil samples.The SCCPs with short carbon chains and low chlorine substitution in the farmland account for the majority and the dry and wet deposition of the atmosphere makes SCCPs with long-distance diffusion the main source of SCCPs in farmland.Woodland is the most polluted landuse type except industrial land,and the presence of SCCPs in organic particulate pollutants generated by friction between automobile tires and road ground may be another important source.?5?Use the quotient method to assess the risk of soil SCCPs in different metropolitan.It is found that the degree of risk control obtained by using different PNEC values was different.When PNEC=0.68 mg/kg,Hangzhou and Hefei Metropolitan have medium environmental risks,and the maximum value points of Nanjing,Suzhou-Wuxi-Changzhou and Ningbo Metropolitan are high environmental risks.The average concentration of each metropolitan area is used to calculate the risk quotient,which is in the middle risk range.The risk of Ningbo Metropolitan is slightly higher than that of the other four metropolitans.When PNEC=5.28 mg/kg,the concentration of SCCPs in the soil of Hangzhou and Hefei Metropolitan does not constitute a major ecological risk to soil organisms.The RQ values of the two high value points of woodland and industrial land in Nanjing and Suzhou-Wuxi-Changzhou Metropolitan are within the medium environmental risk.The highest value of Ningbo Metropolitan area is one order of magnitude higher than the PNEC value.This high value point has a high environmental risk and needs high attention.?6?Use simple human exposure models to estimate daily human exposure values for different metropolitans and different landuse types.The human exposure values of children and adults are lower than TDI?10 pg/kg/day?in both cases.The soil intake of adults is smaller than that of children,while the skin absorption exposure is the opposite,i.e.adults are higher than children.The health risk caused by non-diet exposure in Ningbo Metropolitan area is slightly higher than those of the other four metropolitans.However,the human health risks in the five metropolitan areas are low.The health risks caused by non-dietary exposure under different land use types are also low.