| PAHs are typical organic pollutants with compounds arranged and combined by two or more benzene rings in different shapes such as string or branched chains.Having high lipophilic and hydrophobic characteristics,PAHs have become important environmental and food pollutants.they have attracted wide attention because of their characteristics of environmental persistence,bioconcentration,and "tri-induced"effects.As a solid-phase sediment,the study of the concentration status and distribution characteristics of PAHs in soil can determine the environmental pollution situation in the study area,which is an important basis for ecological risk and health risk assessment,and can also judge the information such as the main sources.A total of 89 surface soils were collected in Qinghai lake area in May 2019.The content and composition of PAHs in soil,the correlation between soil physicochemical properties and PAHs,the distribution characteristics of different regions in the study area and their environmental ecological and health risks were evaluated,and the potential sources were analyzed,PAHs,extracted from soil samples by ultrasonic extraction were purified by silica gel alumina chromatography column.Finally,16 PAHs of the samples were determined by gas chromatography-mass spectrometry(GC-MS).16 PAHs in the samples were determined.The PAHs in surface soil were evaluated by the toxicity equivalent concentration TEQBaP?risk quality standard method of benzo[a]pyrene and the lifetime carcinogenic risk method.Comparison method,result analyze the source of PAHs.The main findings are as follows:(1)The characteristics of total volume distribution and components in this study area:the average total amount of PAHs was 318.37?g·kg-1.The concentration range of total pahs in the sample was 169.00 to 638.94?g·kg-1,and the change range of monomer pah was 0.33 to 215.17?g·kg-1.The size was in order of Phe>Fla>Pyr>Nap>Flu>Phr>BbF>Acy>BaA>BaP>Bghip>BkF>InP>Ant>Ace>DahA.Among all samples,the relative content of 5-cyclic benzo[a,h]anthracene was the lowest,and the content of 3-cyclic phenanthrene was the highest.The proportions of 2 rings,3 rings,4 rings,5 rings and 6 rings in all samples were 8.80%,8.13%,7.83%,3.44%and 2.71%,respectively.The total amount of low molecular weight 2-3 ring PAHs was 157.48?g·kg-1,with a range of 71.39?311.01?g·kg-1,accounting for 49.22%,ranging from 40.89 to 70.73%.The total amount of 4-ring PAHs was 99.78?g·kg-1,ranging from 48.68 to 226.12?g·kg-1,accounting for 31.06%,ranging from 17.04 to 38.10%.The total amount of 5-6 ring PAHs was 61.12?g·kg-1,ranging from 26.13 to 108.91?g·kg-1,accounting for 19.72%,ranging from 9.58 to 33.40%.The 2-3 ring PAHs composition is dominant with the largest proportion.In terms of carcinogenic strength,4-6 The results of this study showed that the mass fraction of PAHs was 50.78%,the 4-ring PAHs of middle or toxicity was 31.06%,the 5-6-ring PAHs of strong cancer was 19.72%,and the other was non-cancerous or low-toxicity 2-3-ring PAHs,the mass fraction was 49.22%.(2)From the spatial distribution characteristics of pollutant concentration,the average PAHs content of sample points in the northern region of Qinghai Lake is 350.30?g·kg-1,ranging from 138.38 to 638.94?g·kg-1,and the monomer range is 0.33?215.17?g·kg-1.The average PAHs content of sample points in the southern region was 336.94?g·kg-1,ranging from 189.56 to 560.59?g·kg-1,and the monomer range was 0.61 to 157.85?g·kg-1.The average PAHs content of samples in the western region is 266.57?g·kg-1,ranging from 172.36 to 458.37?g·kg-1 and monomer ranging from 0.47 to 109.28?g·kg-1.The average PAHs content of sample points in the eastern region was 260.63?g·kg-1,ranging from 169.00 to 320.56?g·kg-1,and the monomer range was 0.66 to 97.44?g·kg-1.The average value of the total sample point PAHs in Qinghai Lake area is the northern region>the southern region>the western region>the eastern region.Judging from the distribution characteristics of pollutants in different soil types:the average value of PAHs content was ranked as farmland>grass beach>other sandy land,farmland soil was dominated by 2-4 ring PAHs,sandy soil was dominated by 2 ring PAHs,and the content of other rings PAHs little difference.(3)To assess the ecological and human health risks of heavy metal pollution in the soil of the study area,the standard method of toxicity equivalent concentration and risk quality of benzo[a]pyrene was selected.the benzo[a]pyrene toxicity equivalent concentration evaluation method shows that the benzo[a]pyrene toxicity equivalent concentration(TEQBap)in the surface soil samples in Qinghai lake area has exceeded the standard reference value(33?g·kg-1)by 33?58?71?73?74?78?89 and so on.There is a slight ecological risk,accounting for 7.87%of the total sample points.71 benzo[a]pyrene toxicity Equivalent concentration is highest,42.35 ?g·kg-1,1.3 times the standard reference value.From the distribution area of superscript sample points,the TEQBap value exceeds the standard sample points,mainly concentrated in the northern part of Qinghai Lake.This may be related to the distribution of farmland,pasture and population in the northern part of Qinghai Lake,which causes the local soil to be frequently affected by human activities such as life,transportation and industrial production.And the remaining 92.13%of soil samples with benzo[a]pyrene toxicity equivalent concentration values below the standard reference value belong to the eco-free risk level.Among them,sampling sites 4?19?34?52?56 benzo[a]pyrene TEQ concentration less than 10?g·kg-1,is much lower than the standard reference value.TEQBap values of samples 13?28?61?77 are close to standard reference values and need attention and prevention.The risk quality standard method evaluation showed that the Flu PAHs monomer content of 70 soil samples was greater than the ERL value,which would have occasional toxic effects on organisms,and 16 PAH monomers of other soil samples would hardly have toxic effects on organisms.(4)Assessment of soil PAHs health risk in the study area shows that the potential carcinogenic risk PAHs in the surface soil of Qinghai Lake area is generally obvious,and the potential carcinogenic risk of children is greater than that of adults.Among them,throughout the study area,the risk of lifetime carcinogenicity in children(including skin absorption,ingestion,respiratory inhalation 3 pathways)was 1.7790×10-5,slightly greater than 1.000×10-5,reaching a low risk of carcinogenicity.Adult lifetime carcinogenic risk is 1.0096×10-6,which has not yet constituted a lifetime carcinogenic risk.As far as carcinogenic pathways are concerned,both children and adults show>skin absorption pathways intake pathway>respiratory inhalation pathway.(5)Source analysis shows that most samples are affected by the pollution sources of motor vehicle exhaust and biomass and coal combustion,and individual samples may also be polluted by leakage during the mining and transportation of petrochemical products.Analysis showed that the PAHs of surface soil in Qinghai Lake area was mainly from fuel source,biomass combustion and oil source.This is consistent with the pollution sources indicated by the BaA/(BaA+Chr)values between 0.3-0.4 and InP/(InP+BghiP)near 0.5 in the ratio analysis.Comprehensive analysis shows that the main sources PAHs this study area are high temperature combustion sources of petroleum and biomass and mixture of petroleum sources.This may be due to the fact that the study area belongs to the less developed area,the way of life is dominated by the use of new firewood and cow dung biomass,and the tourism industry is the economic pillar,the foreign vehicle route is frequent,some sampling points are close along the main highway,and the contribution source of traffic is relatively large,so there is oil combustion composition. |
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