Source Tracer And Risk Assessment Of PAHs In Soil And Surface Dust In Hangzhou

As a typical persistent organic pollutant,polycyclic aromatic hydrocarbons（PAHs）have attracted extensive attention from scholars at home and abroad due to their carcinogenicity,teratogenicity and mutagenicity.Among them,16 PAHs have been listed in the priority control pollutants list of the United States Environmental Protection Agency（USEPA）.Soil is the most important sink of PAHs in the ecosystem.Due to the hydrophobicity of PAHs,PAHs are easily adsorbed to soil particles.Once PAHs enter the soil,they will be adsorbed by the organic matter in the soil and difficult to decompose,thus causing soil pollution.Surface dust of PAHs is equally important,due to the strong human activities such as transportation,industrial and agricultural production,the influence of the surface dust adsorption of organic pollutants and transformation through atmospheric particulates,rainfall and surface runoff process in the atmosphere,hydrosphere and biosphere circulation transformation,the ecological environment and human health will produce harm can not be ignored.In this study,100 soil samples and 97 surface dust samples were collected by grid sampling method based on field investigation in Hangzhou city.The total organic carbon（TOC）,clay,silt and sandy soil of soil and surface dust were analyzed by total organic carbon analyzer and laser particle size analyzer.Used gas chromatography mass spectrometry instrument for USEPA optimal control of 16 kinds of pahs concentrations were measured,using feature ratio method,PMF receptor model and the monomer of stable carbon isotope analysis,the soil and the source of polycyclic aromatic hydrocarbons in surface dust was studied,using the single pollution index method,the merlot composite index method,risk value method and lifetime cancer risk method to assess the polycyclic aromatic hydrocarbons in soil and surface dust pollution level,ecological and health risks,by building the LUR model to explore the influence of different characteristic variables of polycyclic aromatic hydrocarbons,The aim is to provide theoretical basis for environmental protection and pollution control of polycyclic aromatic hydrocarbons in Hangzhou.The main conclusions and understandings of this study are as follows:（1）The results of PAH content showed that the detection rates of NaP,Acy,Fl,Phe,Ant,Flu,BaA,Chr,BbF,BkF,Ba P,InP and Dah A were 100%,and the detection rates of Ace,Pyr and Bghi P were 98%,99%and 96%,respectively.Except for the undetected monomers,the concentration of PAH was in the range of 0.30～545.11μg/kg,and the concentration of ∑16PAHs was in the range of 67.65～2950.07μg/kg,with an average of 417.47μg/kg.The detection rates of NaP,Acy,Fl,Phe,Ant,Flu,BaA,Chr,BbF,BkF,Ba P,InP and DBA were 100%,and the detection rates of Ace,Pyr and Bghi P were 98%,99%and 96%,respectively.Except for those undetected,the concentration of monomer PAH ranged from 1.37μg/kg to 542.93μg/kg,and the concentration of ∑₁₆PAHs ranged from 188.02μg/kg to 3818.31μg/kg,with an average value of 1103.51μg/kg.The concentration of cyclic PAHs and ∑₁₆PAHs in the dust was about 3 times that in the soil.Compared with the domestic and foreign studies,the content of PAHs in the soil and surface dust in Hangzhou is at a low level.（2）The ratios of each ring PAHs to ∑₁₆PAHs in the soils of Hangzhou were as follows:2 ring 9.00%,3 ring 24.06%,4 ring 36.05%,5 ring 22.02%and 6 ring8.86%.The proportions of PAHs and ∑₁₆PAHs in the surface dust were as follows:2rings 4.70%,3 rings 21.61%,4 rings 35.54%,5 rings 24.69%and 6 rings 13.45%.In the two kinds of environmental media,4 cyclic PAHs are the main composition,and the highest proportion of monomer PAH is Phe.The average concentration of ∑₁₆PAHs in soils of different land use types in Hangzhou was as follows:industrial and transportation construction land>Urban Land>Rural Residential Area>Cultivated land>Forest land;The average concentration of ∑₁₆PAHs of different land use types in the surface dust is as follows:urban land>Construction land for industrial and transportation>Cultivated land>Rural Residential Area>Forestland,frequent human activities and industrial production process are the important influencing factors of PAHs.（3）based on SPSS correlation analysis of polycyclic aromatic hydrocarbons and the physical and chemical properties,TOC,according to the results in addition to no correlation between Acy,Ace and TOC in the soil,soil and other monomers PAH andΣ16 pahs in the surface dust and TOC are significant（confidence level of 0.05）positive correlation.The results of particle size correlation analysis showed that there was no significant correlation betweenPAHs and clay,silt and sand in soil and surface dust in Hangzhou,indicating that particle size was not the main factor affecting PAHs.（4）The source analysis of PAHs in the soil and surface dust of Hangzhou City shows that,according to the characteristic ratio method,the PAHs in the soil are mainly from oil combustion,coal and vegetation combustion,followed by petroleum.The main source of PAHs in dust is coal and grass,followed by oil,and oil is less.According to the PMF receptor model,there are four major contributing factors of PAHs in soil,and their contribution rates are as follows:fossil fuel and biomass combustion source 51.8%,traffic emission source 35.2%,coke oven source 9.4%,petroleum product volatilization and leakage source 3.6%.There are three major contributing factors of surface dust,and their contribution rates are as follows:51.3%of fossil fuel and biomass combustion,29.5%of traffic emission,and 19.1%of mixed sources of volatilization and leakage of coke oven and petroleum products.Single based on stable carbon isotope analysis,the soil of each monomer polycyclic aromatic hydrocarbons in the delta of hangzhou ¹³C values range from 31.4‰to 23.5‰,the surface of the dust in the deltaδ¹³C values range from 31.3 to 23.6‰,low ring pahs deltaδ¹³C values compared with epipodium pahs are smaller,so the soil and surface dust in theδ¹³C more enrichment in low ring pahs,and low ring pahs sources are mainly coal and biomass combustion,epipodium sources of pahs is mainly coal processing and transport emissions.（5）The results of pollution assessment showed that according to the Dutch standard,Flu was at a high pollution level,Nap,Phe and Chr were at a medium pollution level,and all other PAHs were at a low pollution level.The comprehensive pollution index of ∑₁₆PAHs was 2.73.Flu and Chr,Nap,Phe and Bghip were high pollution levels,BaA,BkF,Ba P and InP were medium pollution levels,and only Ant was low pollution level.The ∑₁₆PAHs comprehensive pollution index was 6.48.According to the Canadian standard,the monomeric PAHs in the soil of Hangzhou were all at a low pollution level,and the comprehensive pollution index of ∑₁₆PAHs was 0.42.In the surface dust,except for Phe,all other monomer PAHs are at a low pollution level,and the comprehensive pollution index of ∑₁₆PAHs is 1.26.（6）The ecological risk and health risk assessment showed that according to the risk quotient method,the RQ _{∑PAHs（NCs）}in the soil of Hangzhou ranged from 26.66 to 602.70,with an average of 87.76,and the RQ _{∑PAHs（MPCs）}ranged from 0.29 to 7.33,with an average of 1.03.The range of RQ _{∑PAHs（NCs）}in the surface dust is 41.46～893.90,with an average of 253.26,and the range of RQ _{∑PAHs（MPCs）}is 0.57～10.73,with an average of3.17. ∑₁₆PAHs in soil and surface dust were at medium ecological risk level.According to the results of lifetime carcinogenic risk,the carcinogenic risk rates in soil and surface dust from the highest to the lowest were:skin exposure>eat ingestion>spiratory ingestion.In terms of age and sex,adults are at higher risk for cancer than children,and women are at higher risk for cancer than men.（7） ∑₁₆PAHs, ∑_2ringPAHs, ∑_3ringPAHs, ∑_4ringPAHs, ∑_5ringPAHs and ∑_6ringPAHs concentration as the dependent variable,with land use types,population distribution,traffic characteristic variables as independent variables,such as road,industrial pollution sources to build hangzhou soil and surface dirt land use（LUR）regression model,because there was no obvious correlation between independent variables and dependent variables in the soil,therefore not suitable for LUR model was constructed.Only LUR model was constructed for the surface dust,and the R2 after model adjustment was 0.981,0.953,0.976,0.973,0.970 and 0.955,respectively.Moran index and leave-one cross-validation were used to verify the model,and the correlation coefficients between the predicted and measured values of the model were 0.363,0.318,0.274,0.500,0.307 and 0.390,respectively,showing significant positive correlation（P<0.01）.RMSE values were 0.265,0.279,0.235,0.300,0.248 and 0.354,respectively.The RMSE values were small,indicating a high accuracy of the model.