Distribution,Sources And Risk Assessment Of Polycyclic Aromatic Hydrocarbons In The Yangtze River Delta

Yangtze River Delta（YRD）is one of the most prosperous and populous regions in China.With the acceleration of urbanization and industrialization,the contradiction between environment and economic development in the YRD is becoming more and more prominent.YRD is the concentration of chemical industrial parks,accounting for more than 1/6 of the total number of chemical industrial parks in China.PAHs produced and discharged by enterprises in the park enter the tributary water body through surface runoff and atmospheric deposition,and finally enter the Yangtze River.However,the current literature on the source of PAHs mainly focuses on petroleum sources（unburned petroleum and coal）and combustion sources（combustion and vehicle emissions）,and the study on chemical sources of PAHs is relatively insufficient.In order to understand the distribution characteristics and sources of PAHs in the YRD,128 samples were collected from the chemical industry park and surrounding areas as the key research area.The distribution characteristics,sources and risk assessment of water,soil and sediment in typical industrial parks and their surrounding areas in YRD were studied.The results showed that:（1）The total concentration of 19 PAHs in the water and sediments of the YRD is 32.98～286 ng·L^-1and 15.14～5355 ng·g^-1,respectively.Wuxi has the highest content of PAHs,mainly high molecular weight PAHs,which may be affected by the fine chemical industry park nearby.Four-ring and five-ring PAHs in sediments accounted for 61%of the∑PAHs in sediments,and the concentration of two-ring and three-ring PAHs in water was more than 68%.The isomeric ratio analysis and PCA/MLRA results show that the concentration of PAHs in water and sediment is greatly affected by industrial emissions.The fugacity fraction approach was applied to explain the trend for water–sediment exchange of 16 priority PAHs,which showed that net fluxes for most were from the sediment into water.The results indicated that the LMW PAHs were in a non-steady state in the sediment–water system.An ecological risk assessment showed that most sites were of low to medium risk,while the risk level of Wuxi City is relatively high.（2）The concentration of∑PAHs₁₉in the soil is 16.3～4694 ng·g^-1,with4-ring and 5-ring PAHs dominated.The spatial distribution of PAHs in the soil is similar to that in water and sediment.The areas with the highest concentrations are located in the middle of the YRD.The PAH isomer ratios and PCA/MLRA results indicated that PAHs concentrations in soil in the YRD and RD are mainly supplied by industrial and traffic emissions.Incremental lifetime cancer risks（ILCRs）indicated that PAHs in soil pose negligible cancer risks to children and adults,but much stronger risks to children than adults.The research results show that PAHs in water,sediment and soil in the YRD is at a moderate level,and the main sources of PAHs are industrial and traffic emissions.In addition,most of the sampling points in the YRD are at a medium to low risk level.The results of this study can provide data basis and theoretical basis for the pollution control of PAHs in the YRD.