Distribution Characteristics,Sources And Risk Assessment Of Polycyclic Aromatic Hydrocarbons In Surface Soils In The Central And Eastern Qinghai-Tibet Plateau

Seventy-five soil samples were collected across the central and eastern Qinghai-Tibet Plateau(along the main Qinghai-Tibet Road)during July to August in 2013.The soil samples were subjected to ultrasonic extraction and HLB solid-phase extraction cartridges.Sixteen polycyclic aromatic hydrocarbons(PAHs)of USA EPA contents were analyzed.The content and distribution characteristics of PAHs in the soils were analyzed.The sources of PAHs were studied by using the diagnostic rations and principal component analysis(PCA).And the risk assessment of PAHs by using the toxic equivalent concentration(TEQ)of benzopyrene(a)pyrene(TEQBaP)and the quality standard method and carcinogenic risk assessment(ILCR).The result are as follows:(1)Sixteen kinds of PAHs were detected,the total PAHs concentrations ranged from 46.42 to 864.54 μg · kg-1 in the study area,with an average value of 246.16 μg · kg-1 and a median value of 220.22 μg · kg-1.The contents of Phe in the 16 PAHs were the highest,the content ranged from 12.90 to 440.51 μg · kg-1,and the average of 104.93 μg · kg-1,and the median value of 96.50μg· kg-1.The order of the content of PAHs in 16 species was Phe>Fla>Pyr>BbF>BghiP>InP>flu>Chr>Nap>BaP>DaA>BkF>BaA>Ace>Ant>Acy.Low-ring PAHs(two and three rings PAHs)were dominant in all samples,ranged from 44.15%to 86.75%with an average of 66.45%.The proportions of four rings PAHs ranged from 9.06%to 36.35%with an average of 18.79%The proportions of five and six rings PAHs ranged from 2.82%to 26.19%,with an average of 10.41%.(2)Through calculation and analysis,it is concluded that the PAHs are roughly in the range of non-polluting and mild polluting in this research.Compared with other areas in the Qinghai-Tibet Plateau,the pollution level is high,while that in other cities at home and abroad is far below the pollution level.The discussion about pH、δ13CTOC,TN,TP and PAHs,the positive correlation betweewn PAHs and δ13CTOC,TN,TP and the negatively correlation between PAHs and pH.(3)The source of the surface soils in the middle and eastern Qinghai-Tibet Plateau was analyzed by diagnostic rations and the principal component analysis.The comparative analysis of the PAHs in soil showed that the source of the PAHs in the study area was mainly the combustion source.The main contribution rate of PAHs in the soil is the high-ring PAHs(BaA,BbF,BaP,InP and Bghip)obtained by principal component analysis.The main components of PAHs are petroleum combustion source and biomass combustion source.(4)Toxic equivalent concentration(TEQ)of benzopyrene(a)pyrene(TEOBaP)and risk quality standard method showed that there was a low risk of soil PAHs in the study,and the toxicity of some areas exceeded the target reference value.According to the health risk assessment of lifetime carcinogenic risk(ILCR),the health risks of soil PAHs in the study are at risk-free status.Overall,the risks in this study are low,but we still need to be taken seriously.The decision-making development mode needs to consider the ecological environment influences.