Pollution Characteristics And Risks Of Heavy Metals And Polycyclic Aromatic Hydrocarbons In The Surface Dust Of Xi'an Passenger Station

In this study,the surface dust from 18 passenger stations in Xi'an was taken as the research object,and the physicochemical indexes,pollution levels and distribution characteristics of heavy metals and polycyclic aromatic hydrocarbons in 72 surface dust samples were analyzed,the qualitative and quantitative analysis of the sources of heavy metals and polycyclic aromatic hydrocarbons was carried out,and the ecological risks and health risks of heavy metals and polycyclic aromatic hydrocarbons were evaluated.The results of this study can be combined with other studies on urban environmental media to complement and demonstrate each other and reflect the overall situation of regional environment in a more comprehensive and systematic way.It provides data support for a comprehensive understanding of the surface dust heavy metal and PAHs pollution status of Xi'an passenger stations and provides scientific reference for Xi'an passenger stations surrounding environment management,passenger station staff health protection and other aspects.The main research results are as follows:(1)The results of determination of the main physical and chemical indexes of surface dust in Xi'an passenger stations show that the surface dust in Xi'an passenger station is generally alkaline,the first mode of surface dust particle size is 10?63 m,the frequency magnetization rate is between 3.44%and 8.53%,and the content of surface dust organic matter in passenger stations is higher than that in Xi'an surface soil.The physicochemical indexes of the surface dust in Xi'an passenger stations all show a certain spatial and temporal distribution difference.(2)The content of V,Cr,Mn,Co,Ni,Cu,Zn,As and Pb in the surface dust of Xi'an passenger stations was determined by X-ray fluorescence spectrometer.The results show that,except for V,Mn,Ni and As,the average content of the other five elements was higher than the background value of soil elements in shaanxi province,with different levels of exceeding the standard.(3)The content of ?16PAHs in the surface dust of Xi'an passenger stations was analyzed by HPLC,and ?16PAHs ranged from 1.369 to 3287.061 mg/kg,with an average value of 100.305 mg/kg.The content of ?16PAHs in the surface dust of passenger stations is higher than that in the medium of other research areas in Xi'an,among which the PAHs of ring 3 contributes the most.(4)Kriging interpolation method of ArcGIS software is used to draw heavy metals in surface dust in Xi'an passenger stations and the spatial distribution of PAHs content,the results show that the high content of V,Mn,As the value mainly appear in Xi'an city,yanliang and zhouzhi county,the high value of Cr,Ni,Cu,Zn and Pb are mainly in the urban area,at the same time show the eastern district is higher than the trend of the western counties.The Co content in the southern district is higher than that in the northern district.The content of 5 elements in 9 heavy metals in spring was higher than that in winter.The rough trend of the spatial variation of ?16PAHs is:the central part of Xi'an is high.The time distribution difference of the content of 16PAHs is in winter>in autumn>in spring>in summer.(5)By using principal component analysis,PMF model analysis and ratio method,qualitative&quantitative method,analysis results show that the natural source contributions to the highest levels of V and Mn,traffic source of Cr,Ni,Cu and Zn,As,Pb content in the contribution is the highest,the content of Co is mainly composed of industrial source contribution.Heavy metal pollution in surface dust mainly comes from automobile traffic activities(51.8%),followed by industrial activities(26.2%)and natural factors(22.0%).The concentration of 2-ring and 3-ring PAHs dominated by the source of oil spill.Fla and Pyr mainly come from coal burning sources.The main sources of BaA,Chy,5-ring and 6-ring PAHs are traffic pollution sources.For the total surface dust of Xi'an passenger stations,the contribution of each pollution source is traffic pollution source(48.3%),coal source(28.6%)and oil leakage source(23.1%),respectively.(6)According to the analysis of cumulative index method and pollution load index method,it is concluded that V,Mn,Ni and As in the study area are pollution-free As a whole,Cr,Cu,Zn,Pb and Co all reach pollution levels of different degrees.The surface dust of passenger station is mainly polluted by heavy metals with moderate to strong degree,and the overall situation shows that the larger the passenger flow of passenger station is,the more serious the surface dust heavy metal pollution is.The results of single potential ecological risk assessment are as follows:Co has a strong potential ecological risk,Pb has a strong ecological risk,Cu has a medium potential ecological risk,and the remaining six elements have a slight potential ecological risk.Among the 18 passenger stations,the heavy metal pollution in the dust on the surface of 5 passenger stations reached a very high ecological risk level.(7)The results of single factor and nemero comprehensive pollution index method showed that both the PAHs monomer and the total amount in the surface dust of Xi'an passenger station were seriously polluted.The ERL and ERM analysis of the effect interval indicated that PAHs in surface dust of passenger stations in spring,autumn and winter was of high ecological harm,and there was occasional harm in surface dust in summer.(8)The results of the health risk assessment on the staff of passenger station show that the non-carcinogenic risk and carcinogenic risk of heavy metals in surface dust of Xi'an passenger station are both within the safety threshold,while PAHs has a certain carcinogenic risk.(9)Correlation analysis of PAHs and heavy metal content shows that PAHs is similar to Cr,Ni,Cu and Pb,and the content of dust on the surface of passenger stations is mostly affected by human factors,especially traffic activities.