Characteristics,Sources And Human Health Risk Assessment Of PAHS In The Atmosphere,Water And Soil Of An End-of-Life Vehicle Dismantling Site

With the rapid development of the global economy,the number of automobiles has been increasing,resulting in an increasing amount of scrap cars.The dismantling of scrap cars produces a large amount of polycyclic aromatic hydrocarbons（PAHs）,which have toxic effects such as carcinogenicity,teratogenicity,and mutagenicity.Long-term exposure to PAHs can cause irreversible harm to human health.In this study,a typical domestic scrap car dismantling base was selected as the research background,and the 16 PAHs prioritized by the United States Environmental Protection Agency（USEPA）were studied.Air,water,and soil samples were collected.For the first time,this paper analyzed the concentration level,composition characteristics,emission factors,major sources,and human health risk assessment of PAHs in the scrap car dismantling base and briefly explored several types of PAHs that should be focused on controlling.The conclusions are as follows:（1）The distribution characteristics and composition of PAHs in the three media in the scrap car dismantling base:A large amount of PAHs will be produced in the scrapped car dismantling base,and its concentration of PAHs does not meet my country’s air standards.The concentrations of PAHs in the PM_2.5,PM₁₀,and gas phase of the scrap car dismantling base were 0.638μg/m³,0.634μg/m³,and 1.6131μg/m³,respectively.The concentration of PAHs in the gas phase was higher than that in the particulate matter in the atmosphere,Gas accounted for 89%of the total PAHS,and the particle phase accounted for 11%.The concentration of parts storage area,mechanical crushing area and scrap car storage area is the highest concentration.The total concentration of PAHs in water ranged from7.892μg/L to16.93μg/L,with an average range of 0-12.72μg/L in the process technology area and 0-4.091μg/L in the outside plant area.The mass concentration of target compounds in the water of the process technology area was generally higher than that in the water outside the plant area,and the content of acenaphthene was the highest,with a concentration range of ND-18.2μg/L in the process technology area.The content of PAHS in the sewage is greater than the concentration of PAHS in the rainwater.Among them,a large amount of polychic garden hydrocarbons produced in the mechanical crushing area and artificial sub-region have fallen into the water quality.The mass concentration of BaP should be controlled within 0.55 mg/kg.The concentration of BaP in the surface soil was 0.0056μg/kg.The concentration of PAHs in the surface soil was higher than that in the deep soil.The PAHs concentration in the soil near the mechanical crushing area and the artificial branch area is high,and the concentration of BaP in the deep soil was 0.0026μg/kg.The distribution of PAHs in the number of rings was（2-3）rings>4 rings>（5-6）rings,mainly 2-3 rings and 4 rings.The proportion of 2-3 rings in the gas phase was over 90%,with the highest proportion in the small car cutting area;the proportion of different numbers of rings in PM_2.5was basically the same as that in PM₁₀,with 2-3 rings accounting for about 60%and 4 rings accounting for about 30%.Low-ring PAHs were more common in water,and the concentration of high-ring PAHs was higher than that of 4-ring PAHs in water and deep soil.Among the three mediums:air,water and soil in the disassembly base of the scrap car,the PAHS concentration of polygon aromatic hydrocarbons in the air is the highest,followed by the PAHS concentration in the water is high,and the PAHS concentration in the soil is the lowest.The low ring is mainly distributed in the air,and exists in the form of gas phase.The multi-ring aromatic hydrocarbons in the Central are reduced in the water body.（2）Emission factors of polycyclic aromatic hydrocarbons（PAHs）and human health risk assessment in scrap vehicle dismantling yards:The parts storage area,mechanical crushing area,and vehicle disassembly area in the disassembly base of the scrap car disassembly base are relatively high.Among them,the highest parts of the parts storage area are the vehicle disassembly area,the car cutting area,the mechanical crushing area 4.4,3.4 and 4 Times.The overall emission volume is the highest,followed by the high emissions of Phe and BaA.The emissions of the BaA accounted for 5.6%of the total ratio.In the gas phase,the toxic equivalent concentrations in the parts storage area,the cart cutting area,the end-of-life vehicle storage area and other areas of the plant exceeded the standard limits,posing a greater health hazard to humans;in PM_2.5,the mass concentrations in the mechanical crushing area and the cart dismantling area exceeded the standard limits for ambient air quality concentrations in China;in PM₁₀,the mass concentrations in the complete vehicle dismantling area,the manual sorting area and the end-of-life vehicle dismantling area all exceeded the standard limits for ambient air quality concentrations in China.The PM₁₀concentrations in the vehicle dismantling area,the manual sorting area and the end-of-life vehicle dismantling area all exceed the standard limits for ambient air quality concentrations.The carcinogenic risk is PM_2.5>PM₁₀>gas phase.The gas phase,PM_2.5and PM₁₀of the end-of-life vehicle dismantling site all have different levels of carcinogenic risk,with PM_2.5having the highest carcinogenic risk.（3）Major sources and priority control pollutants of PAHs in scrap vehicle dismantling yards:The main sources of PAHs in scrap vehicle dismantling yards are lubricating oil emissions,coating emissions,adhesive emissions,carbon fiber composite material emissions,petroleum volatiles,cleaning agent emissions,synthetic material emissions,diesel exhaust emissions,and organic luminescent material emissions,with synthetic material emissions and petroleum volatiles being the largest contributors.Nap,Flu,Fla,BaA,Chr,BbF,BkF,BaP,BghiP,and IcdP are priority control pollutants in the atmosphere of scrap vehicle dismantling yards,ranked from highest to lowest as Nap,Chr,Flu,Fla,BaA,BbF,BaP,BkF,IcdP,and BghiP.Therefore,this study can further understand the environmental behavior of PAHs in scrap vehicle dismantling yards,providing reference for monitoring and controlling organic pollutants in the environmental of the scrap vehicle dismantling industry.