Study On The Pollution Characteristics And Migration Behavior Of Benzene Series In The Soil Of Typical Petrochemical Industrial Sites

The petrochemical industry is a key pollution emission source and a key monitoring industry for the soil environment.The current situation of soil pollution in petrochemical sites is becoming increasingly severe.Volatile organic compounds(VOCs)are significant representative pollutants,with high detection rate,wide range of pollution and large pollution depth.As a typical VOCs discharged in the petrochemical industry,there are more studies on benzene series in water and air media.However,the research on the pollution characteristics and environmental behavior of benzene series in site soils is still insufficient.This study investigates the data of petrochemical enterprises in the Yangtze River Economic Belt to reveal the spatial distribution pattern of petrochemical sites in this region.The content and spatial distribution characteristics of benzene series in the soil of a typical petrochemical site were analyzed by field sampling.Adsorption kinetics,isothermal adsorption and soil characterization analysis were used to study the adsorption process of benzene series in soil.The effects of initial p H of the solution,type of purple soil,dissolved organic matter(DOM),and cobalt(Co)on the adsorption process were explored.The dynamic soil column experiment was used to investigate the pollution behavior of benzene series in soil under the conditions of different pollution intensity,p H,pollution concentration and the coexistence of Co.The soil column leaching experiment was used to explore the release laws of benzene series in polluted soil under natural rainfall conditions such as acid rain and rainstorm.The release process of pollutants in soil contaminated by benzene series and Co under the action of rainfall leaching was also studied.The research conclusions are as follows:(1)Synthetic fiber manufacturing and synthetic resin manufacturing are typical representatives of petrochemical enterprises in the Yangtze River Economic Belt.Petrochemical enterprises have formed an industrial chain distribution pattern of“oil and gas extraction-petroleum refining-petrochemical product manufacturing”along the upstream to downstream of the Yangtze River.The Yangtze River Delta is the core of petrochemical industry in this region.The spatial distribution characteristics of toluene,ethylbenzene,m,p-xylene,and o-xylene in research site soil are similar.The benzene series are mainly concentrated in topsoil,and there is a tendency of downward diffusion.(2)The adsorption of benzene series on purple soil includes the combined action of soil mineral components and organic matter components,and is a linear adsorption process dominated by distribution.The initial p H of solution have no significant effect on the adsorption of benzene series in soil.The adsorption capacity of benzene series in acid purple soil is 29.3%～31.4%higher than that of calcareous purple soil.Low-concentration DOM has little effect on the adsorption process of benzene series in soil,while high-concentration DOM has a promoting effect.The coexistence of Co significantly inhibited the adsorption of benzene series in soil.(3)Within the pollution intensity range of 0.02～0.14 mg/cm~3,the migration ability of benzene series is relatively strong,and and the adsorption saturation can be reached in the early stage of soil column leaching.The p H has no significant effect on the pollution behavior of benzene series in soil.The migration ability and pollution risk of benzene series under high pollution conditions are significantly greater.Under the combined pollution of benzene series and Co,the content of benzene series in soil decreased by 6.8%～10.1%.The presence of Co increased the migration ability of benzene series in soil.(4)Acid rain inhibits the release of benzene series in polluted soil and weakens the vertical migration ability of benzene series in soil.The release of benzene series in soil increased significantly with the increase of rainfall intensity,and the cumulative release rate of benzene series under heavy rain conditions reached 26.0%～35.7%.The presence of Co in soil also promotes the release of benzene series,and the cumulative release rate of benzene series in the combined contaminated soil of benzene series and Co is as high as 30.5%～33.4%.Co adsorbed on the soil is difficult to desorb and exhibits weak mobility.