Pollution Characterization Of Polycyclic Aromatic Hydrocarbons In Air And Soil In Xi’an

As a persistent organic pollutant, polycyclic aromatic hydrocarbons (PAHs) werewidely found in various environmental media, and which can cause serious harm tohuman. In this study, gas phase and particulate phase samples were collected from July2008to May2010by a high volume sampler in Xi’an, top soil samples of five differentpoints were collected in August2009, and16kinds of priority control PAHs wereanalyzed via GC/MS. Annual and seasonal variations of atmospheric PAHs wereanalyzed, and using the diagnostic ratio method and PMF method for sourceapportionment. The pollution characteristic, spatial distribution, composition and ofsoil samples in Xi’an area were analyzed, as well as source analysis and riskassessment.While the correlation of PAHs monomers were analyzed, and of andcorrelation analysis of PAHs in atmosphere and soil were discussed.The total concentrations (gas plus particle phases) of∑PAHs ranged from39.93to1032.46ng/m~3in atmosphere, with the average concentration of205.95ng/m~3, theaverage PAHs concentrations between two years were indentical and high content ofPAHs monomers as Phe, Flo, Flu and Pyr. By comparing the change of atmosphericPAHs between two years in Xi’an, found that the distribution rule of PAHs between twoyears were basic agreement, but there are still differences. The results show that,compared with08-09year, seasonal differences of2rings and3rings PAHs decreasedgradually in09-10years, the proportion of3rings PAHs between four seasons reduced,while the rest of PAHs increased, the seasonal diversity of benzene and (a) pyreneequivalent toxic (BEQ) increased, comparing09-10particles phase concentration of08-09increased obviously. Using diagnostic ratio method and PMF method for sourceapportionment, the results showed that the main pollution sources of PAHs was the burning of fossil fuels, the source of PAHs in heating season and the heating season hadcertain difference. According to PMF model, source of PAHs were divided into Coalsource, traffic source and coal chemical industry source and biomass burning source.The contribution of heating season were Coal40.2%，coal chemical industry28.3%,traffic18.8%, biomass burning12.7%, and the contribution of no-heating season wereCoal18.6%, coal chemical industry22.1%, traffic43.5%, biomass burning15.8%.The concentration of PAHs ranged from125.18to9057.17ng/g in top soil of Xi’an,the average concentration was2726.94ng/g, the size order of conceatration:Fangzhicheng aera> Xi’an University of Architecture and Techlonoly> Xingqinggong>caotan> farmland in Chang’an District, principal pollutants contained Flu, BbF, Chrand Pyr. Correlation between PAHs monomer and total PAHs was very good in the soil,especially Flu, Pyr, BaA, Chr, BbF, BkF and DahA, the correlation coefficient was morethan0.99. The correlation coefficient R~2of PAHs between particles and soil was0.8402,which showed very good relevance, however, R~2of PAHs between gas phase and soilwas0.0037, which showed no relevance. Using the isomer ratio method for sourceapportionment, the result showed soil PAHs mainly came from burning source, mainlywas the fossil fuel and timber incomplete combustion. Carcinogenicity analysis throughbenzo (a) pyrene equivalent toxicity (BEQ) of soil PAHs, the result showed that, soilhad certain potential carcinogenicity in the studied area.