Pollution Characteristics And Environmental Risk Assessment Of Arsenic In The Soil Around A Typical Coal-fired Power Plant In Guizhou Province

In order to explore the pollution characteristics and environmental risks of As in the soil environment around a typical coal-fired power plant in Guizhou Province.This study mainly collected soil samples around the Anshun Power Plant in Guizhou Province,determined the content and fraction of As in the soil samples,and analyzed its pollution level and spatial distribution characteristics;At the same time,samples of coal used in the power plant,surrounding plants and atmospheric dust were collected to determine the As content in the samples and analyze their distribution characteristics;Finally,environmental pollution assessment and health risk assessment are made for As in the soil environment around the power plant.The main conclusions are as follows:（1）The average value of As content in coal and fly ash in the study area are 8.86mg/kg and 16.90 mg/kg.The As content is relatively high and has high typicality.The average As content in atmospheric dustfall is 20.653 mg/kg,which is 1.39 times of the soil background value in Guizhou Province.It shows that the atmospheric environment in the study area is polluted to a certain extent.And the As content in the atmospheric dustfall in different directions is significantly different.The As content in the atmospheric dustfall in the downward direction of the prevailing wind throughout the year（north）is 22.847～27.636 mg/kg,and the As content in the atmospheric dustfall in the downward wind direction of the dominant wind（northwest）is 21.383mg/kg,and the As content in the atmospheric dustfall in the other non-dominant wind directions is less than 20 mg/kg,which is obviously affected by the local dominant wind direction.（2）The average As content in the surface soil of the study area is 29.650 mg/kg,which is 1.9 times and 2.0 times of the soil background value in Anshun and Guizhou provinces,respectively.The As content in the surface soil of dry fields（30.680 mg/kg）is higher than that in paddy fields（21.409 mg/kg）.There are significant spatial distribution differences in the As content in the surface soil.With the power plant as the center,it is located at 4.5 km downwind direction of the perennial dominant wind（north）and 2.0 km downwind direction of the secondary dominant wind that is the winter dominant wind（west-southwest）.There is a large concentration range where the total As content in the surface soil is above 40 mg/kg,and the As content in the surface soil in all directions increases first and then decreases with the increase of the distance,which is obviously affected by the dominant wind direction.The As content in the vertical space of the soil generally shows that the surface layer is relatively enriched（average value is 27.110 mg/kg）,and the bottom layer is relatively depleted（average value is 16.962 mg/kg）,but the As content in the soil varies with the depth of the soil.The law of change is not obvious.（3）The form of As in the surface soil is mainly in the residue fraction（accounting for 89.16%）,and the water-soluble fraction is the smallest（accounting for0.13%）.The bioavailable concentration and proportion of As in surface soil are both higher in paddy fields than in dry fields.The form concentration of As in the vertical space of the soil changes with the depth of the soil,showing that the surface layer is relatively enriched,and the bottom layer is relatively depleted.Correlation analysis of As in soil shows that the total As and the residue fraction in the surface soil of the study area are significantly negatively correlated with soil organic matter,and the remaining four As forms are significantly positively correlated with soil organic matter;The total As in the soil vertical space,water-soluble fraction,mild acido-soluble fraction,and residual fraction are all significantly positively correlated with soil organic matter;The As,Ni,and Pb in the surface soil are affected by the same pollution source;In the vertical space of the soil,As has the same pollution source as Cr,Zn,Cd,and Pb.（4）The As content in the edible parts of the plant is ginger（Zingiber officinale Roscoe）>eggplant（Solanum melongena）>pepper（Capsicum annuum）>corn（Zea mays）,and the average values are 0.432 mg/kg,0.336 mg/kg,0.175 mg/kg,0.052mg/kg,there is a certain degree of As enrichment phenomenon.Different plants have obvious differences in the accumulation ability of As in the soil.The highest accumulation ability is ginger（average value is 0.018）,and the lowest is corn（average value is 0.003）.（5）Pollution evaluation of As in soil:The average geo-accumulation index of As in the surface soil of the study area is 0.274,which belongs to light pollution,and the highest is light pollution in some areas;The average value of the potential ecological risk index of As in the surface soil is 19.912,which is a slight ecological hazard,and the highest is a moderate ecological hazard in some areas.Health risk assessment of As in soil:The carcinogenic health risk index of adults and children in the study area is generally between 10^-6～10^-4,which is generally at an acceptable level.However,children suffer from higher carcinogenic health risks than adults,and children in some areas have unacceptable carcinogenic health risks.As a whole,adults in the study area have no non-carcinogenic health risks,but children have non-carcinogenic health risks.At the same time,the high-value areas of carcinogenic and non-carcinogenic health risks of As in the soil of the study area are mostly concentrated in the prevailing wind direction throughout the year,and the maximum concentration of air pollutants in coal-fired power plants is at the landing distance.