| In recent decades,with the rise and development of industrial zones in China,the environmental problems caused by them have attracted more and more attention.Heavy metals and polycyclic aromatic hydrocarbons(PAHs)are widely distributed in the environment of industrial sites.Heavy metals and PAHs in the environment,accumulated to a certain level,will cause various acute or chronic adverse effects on the land,waters,and marine ecosystems.If humans are continuously exposed to excessive heavy metals and PAHs,it will lead to various diseases of the cardiovascular system,kidney,liver,respiratory system,and nervous system,including cancer.Coal related comprehensive industrial zone is mainly characterized by coal utilization.The industrial chain includes coal chemical industry,coking,power generation,metallurgy,building materials(cinder utilization),and most of them are related to coal.Compared with the single industrial site,the ecological risk of coal related comprehensive industrial zone has the characteristics of multi-source,multi-channel and multi sensitive target,which further increases the complexity of environmental risk and is more likely to cause potential harm to environmental quality and human health.As the source and sink of pollutants in the environment,surface dust plays an important role in the diffusion,migration and transformation of pollutants in the environment.Therefore,the content,spatial distribution,ecological risk,health risk and source of heavy metals and PAHs in the surface dust of coal related comprehensive industrial zone have become the key scientific issues of environmental pollution research.The research results can provide the basis for the upgrading of the zone,the optimization of industrial layout and the maintenance of environmental sustainable development.In this study,167 surface dust samples were collected from Longmen Industrial Zone in Shaanxi Province.The contents of Cd,Cr,Cu,Mn,Ni,Pb,Zn,As and Hg were determined by atomic absorption spectrometry and atomic fluorescence spectrometry.The speciation of Cd,Cr,Cu,Mn,Ni,Pb and Zn was analyzed by modified BCR method.And the contents of 16 PAHs were determined by HPLC.On this basis,the spatial distribution,ecological risk,health risk and sources of heavy metals and PAHs in surface dust of the industrial zone were explored.And the main conclusions are as follows:(1)The average contents of nine heavy metals Cd,Cr,Cu,Mn,Ni,Pb,Zn,As and Hg were higher than the soil background value in Shaanxi Province,and all were enriched in varying degrees.Among them,the high value areas of Cr,Cu,Mn,Pb,Zn and As contents are mainly concentrated in the iron and steel smelting plants.The high value area of Cd content is mainly distributed in the vicinity of coking enterprises.As for Ni,in addition to the high content in iron and steel smelting area,the Baifan River Basin,is another high value area of Ni content.The high value areas of Hg content are distributed in power plants,coking plants and iron and steel smelters.The speciation analysis of seven heavy metals(Cd,Cr,Cu,Mn,Ni,Pb and Zn)by modified BCR method showed that six heavy metals(Cr,Cu,Mn,Ni,Pb and Zn)are mainly in the residual fractions and Cd is principally distributed in the oxidizable fraction.(2)The results of geoaccumulation index showed that Hg was moderately polluted,Pb and Cd were slightly polluted,and the other six heavy metals Cr,Cu,Mn,Ni,Zn and As were not polluted.The Nemerow synthetic pollution index(NSPI)of heavy metals ranged from 0.97 to 79.97,with an average of 5.64,reaching the level of heavy pollution.The average of heavy metal pollution load index(PLI)was 1.70(0.54-6.99),which was in a moderate pollution level.The samples with high pollution degree were mainly distributed in iron and steel smelting,thermal power station and coking areas,which indicated that these industries were the main pollution sources of heavy metals in surface dust.The evaluation results of pollution factor Cf showed that Cd is the easiest to migrate and the most harmful to the environment.The Cf values of Cu and Cr are less than 1,which indicated that these two elements are less harmful to the environment.The average value of RAC indicated that Cu is at low risk,Cr,Ni,Pb and Zn are at moderate ecological risk,while Cd and Mn are at high ecological risk.The average ecological risk index of the nine elements was 390.0,ranging from 46.2 to 3680.6,and the average value was in the strong ecological risk level.(3)The average amount of 16 PAHs was 7.897 mg·kg-1(0.336 mg·kg-1?143.70 mg·kg-1).The contents of tetracyclic PAHs was the highest,accounting for 36.42%.The average content of 7 kinds of carcinogenic PAHs was 3.520 mg·kg-1,accounting for 41.72%of the total amount of 16 PAHs,and the content of specific combustion compound PAHs was 5.441 mg·kg-1,accounting for 68.90%of the total amount.The content of PAHs in coal chemical industry area is the highest,followed by thermal power,coking,coal washing and other areas.The content of PAHs in iron and steel smelting area is lower than the above areas.It indicated that different coal utilization methods have important influence on PAHs content.(4)Compared with the screening values in the Soil environmental quality risk control standard for soil contamination of development land(Trial)(GB36600-2018),BaA,BaP,BbF,DBahA and IcdP in some samples respectively exceeded the screening value or even the control value of the first type of land,which had an unacceptable risk to human health.Compared with the European classification standard of PAHs pollution in agricultural soil,all samples were contaminated by PAHs.The average TEQBaP of 16 PAHs was 989.15 ?g·kg-1,ranging from 35.10 ?g·kg-1 to 22246.65 ?g·kg-1.Comparison with standard target reference value 32.96 ?g·kg-1 of TEQBaP of Dutch,the TEQBaP values of 16 PAHs in all samples exceeded the standard.The NSPI of PAHs ranged from 0.04 to 12.45,with an average of 0.82,which are on the warning level.(5)According to US EPA model,the non-carcinogenic risk of nine heavy metals to male,female and children was calculated.In terms of exposure in different ways,the exposure of all elements showed hand-mouth intake>skin contact intake>respiratory inhalation intake,that is,hand-mouth intake is the primary way of heavy metal exposure in surface dust.As,Pb,Mn and Cr are the main contributors of non carcinogenic risk.The non-carcinogenic risk of the nine heavy metals to adult male and adult female was less than 1 in all samples.However,for children,there are 13 samples and 1 sample in metallurgical and coal chemical areas respectively,the non-carcinogenic risk index of which was greater than 1,and there was non-carcinogenic risk for these samples.The single carcinogenic risk index and the overall carcinogenic risk index of the four elements Cd,Cr,Ni and As are less than 10-6,indicating that there is no carcinogenic risk of heavy metals in the surface dust of Longmen Industrial Zone.The lifetime incremental carcinogenic risk model was used to calculate the carcinogenic risk ILCRs and total risk CR of PAHs in different populations.In metallurgical area,CR values in 36.92%,36.92%,29.23%and 24.62%samples were between 10-6?10-4 for male,female,children(male)and children(female)respectively,which had tolerable risk.In extended area,CR values in 23.91%?23.91%?15.22%and 15.22%samples were between 10-6?10-4 for male,female,children(male)and children(female)respectively,which had tolerable risk.In coal chemical industry area,CR values in 35.71%?35.71%?30.35%and 28.57%samples were between 10-6?10-4 for male,female,children(male)and children(female)respectively,which had tolerable risk.In the three functional areas,the average CR value of different groups from large to small was adult female>adult male>children(male)>girl children(female).For all groups,PAHs in coal chemical industry area has the highest carcinogenesis risk,followed by thermal power and coking plants in metallurgical area.(6)Correlation analysis showed that the heavy metals in surface dust had weak or no correlation with pH and loss on ignition,indicating that pH and organic matter were not the main factors affecting the heavy metal content in surface dust.There was a certain degree of correlation between 16 PAHs and organic matter content.Except for acid and Ace,the other 14 PAHs had a certain degree of correlation with pH,but most of the correlation.are weak.The results of source apportionment showed that 70.43%of heavy metals were from coal combustion,transportation and building materials,and 29.57%from the industrial source of machinery manufacturing and coal combustion.The results of source apportionment showed that 72.37%of PAHs came from coal pyrolysis and combustion,and PAHs volatilization in raw coal and transportation accounted for 27.63%.Based on the study of heavy metals and PAHs in Longmen coal related comphrehensive industrial zone in Hancheng,some suggestions are put forward for the sustainable development of the environment in the industrial zone.In order to reduce the risk of heavy metals and PAHs to the residents,residential districts too close to enterprises in metallurgical area and coal chemical industry area can be corsidered for relocation.The ash storage yard of power plant should be protected to prevent the coal ash from spreading under the action of wind and surface runoff,thus harming the surrounding environment.When using coal ash as building materials,the proportion of coal ash should be controlled to reduce the risk to an acceptable range. |
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