Characterization And Ecological Risk Assessment Of Polycyclic Aromatic Hydrocarbons Contamination In Soil Of A Typical Coking Site

The environmental problems caused by contaminated sites left by coking industry are increasingly prominent,which pose a serious threat to the ecological environment and human health.Based on the test results of soil samples from a typical coking site in southern China,this paper explored the pollution characteristics and distribution of polycyclic aromatic hydrocarbons（PAHs）in the site.The sources of PAHs in site soil were analyzed by ratio method,principal component analysis-multiple linear regression（PCA-MLR）model and positive matrix factorization（PMF）model.The pollution safety index（CSI）method and the soil and groundwater risk assessment（HERA++）model were used to preliminarily assess the potential ecological risk and human health risk of PAHs in soil,and the contribution of PAHs pollution sources to human health risk was quantified by establishing PMF-HERA++coupling model.In order to provide theoretical basis for PAHs pollution prevention and control and soil environmental management in coking industry legacy sites.The results are as follows:（1）The pollution situation in the study area was not optimistic.The total amount ofΣ₁₆PAHs ranged from 0.88～2916.6 mg·kg^-1,with an average content of 15.98 mg·kg^-1.30%of the soil samples in the surface soil were heavily polluted and 34%in the deep soil were heavily polluted.The average content of Fla is the highest,followed by Pyr;PAHs had strong spatial heterogeneity in the surface layer and deep layer of soil,and the PAHs content in the surface layer is higher than that in the deep layer,and the spatial heterogeneity is stronger.The average content of PAHs in central ring was the highest.The surface soil was dominated by central and high-ring PAHs,and the pollution was concentrated in coking,chemical production,gas production and carbon black production area,while the deep soil was dominated by medium and low-ring PAHs,and the pollution was concentrated in chemical production,carbon black production area,gas production and coal preparation.（2）The results of three PAHs pollution source apportionment methods were basically consistent,which can complement and confirm each other.The results of ratio method showed that PAHs pollution in the study area mainly came from coal and biomass combustion,followed by liquid fossil combustion source and finally petroleum source.PCA-MLR model showed that the main sources of soil PAHs are coal and traffic mixed combustion source,coking source,petroleum source and diesel combustion mixed source in turn according to the contribution rate.The four pollution sources analyzed by PMF model were coking source,coal combustion source,mixed combustion source of coal,gasoline and petroleum,and mixed combustion source of petroleum and diesel in order of contribution rate.（3）The potential ecological risk of PAHs in surface soil was much higher than that in deep soil.About 30%of soil samples in the surface layer belonged to ultra-high ecological risk,and about 38%of soil samples in the deep layer belonged to very high ecological risk;The coke oven workshop and ammonium sulfate workshop in the surface production area had the highest ecological risk and belong to ultra-high risk areas.The ecological risk of tar loading and unloading in deep production area and oil tank area was the highest,followed by refined benzene section,all of which belong to ultra-high risk areas.（4）Benzo（a）pyrene（BaP）had the highest cancer risk in the soil of the study area,followed by dibenzo（a,h）anthracene（Db A）;Ba P has the highest non-carcinogenic risk,followed by naphthalene（Nap）.Except benzo（k）fluoranthene（Bk F）,the carcinogenic risk of other pollutants in the surface layer was higher than that in the deep layer.Different functional areas had different levels of over-standard pollutants and risks,which were related to site production technology,history,site environment and physical and chemical properties of pollutants.The carcinogenic risk and non-carcinogenic risk of PAHs produced by coal,gasoline and petroleum mixed combustion sources in the soil of the study area were the highest,with the contribution rates of 93.9%and 89.1%respectively.