Ecological Risk Assessment Of Heavy Metal Pollution In Soil Of A Mining Area In Hunan Province

The paper takes a mining area in Hunan as the research object,and analyzes the status of heavy metal pollution in the mining area by using the heavy metal background value of the soil in the mining area.The geostatistics method is used to analyze the horizontal distribution rule of heavy metal pollution in the soil around the mining area.RGA model and RBCA model of contaminated site ecological risk assessment technology method to carry out ecological risk assessment of heavy metal pollution in the mining area,through the "five-step method" evaluation step,to determine the mining site soil heavy metal pollution risk control value,in order to be able to carry out the soil heavy metal pollution risk control And governance remedies provide a theoretical basis.The main findings are as follows:(1)The overall distribution rule of soil arsenic and antimony pollution in the mining area is top soil(0-0.2m)>middle soil(0.2-0.5m)>lower soil(0.5-1m).The leaching concentrations of arsenic and antimony in the waste residue at various sites are all low,indicating that due to the long time for the waste slag to be deposited in the mining area,a large amount of arsenic and antimony have already occurred in the waste slag and accumulate in the soil of the mining area,resulting in a high content of arsenic and antimony in the mining area.The distribution characteristics.(2)There is a significant difference in arsenic contamination in each stratum of the mining area.The surface soil arsenic in the construction area and tailings reservoir has a high degree of overall pollution.The overall pollution degree in the old mining area and flotation workshop is low,and the middle layer of soil arsenic in the working shed area and the tailings reservoir have a high degree of overall pollution,in the flotation workshop.The overall pollution level is low.The arsenic in the underlying soil has extremely high levels of pollution in tailings and flotation workshops,and the level of arsenic contamination in the shelters is low.Arsenic in the surface soil is distributed in the tailings pond>shed area>flotation workshop>old mining area.According to the law,the arsenic in the middle layer of soil is in the tailings deposit>shed area>flotation plant's pollution distribution rule,the arsenic in the underlying soil is tailing pond>flotation workshop>shed pollution distribution law.(3)The distribution of antimony pollution in each stratified soil in mining area is obviously different.The overall level of contamination of surface soil in the flotation plant and work area is high.There is a large difference in the distribution of east-west pollution in the tailings area.It is extremely high in the west and very low in the east.The overall level of pollution in the old mining area is extremely low,and the middle soil is contaminated in the flotation plant.The overall pollution level in the construction and construction areas is high,the overall pollution degree of the tailings yard is reduced,the overall pollution degree of the lower soil flotation plant and the tailings pond is high,and the overall pollution degree of the earthworm area is low.In the surface soil,there is a flotation workshop>tailings reservoir>work shed area>pollution distribution rule of the old mining area,maggot flotation workshop in the middle layer soil>work shed area>pollution distribution rule of the tailing pond,and flounder in the lower soil.Workshop>Tailings Reservoir>Pollution Distribution Law in Gongping District.(4)Based on C-RAG model and RBCA model,the risk value of arsenic carcinogenesis in mining area is calculated.The risk of arsenic carcinogenesis in mining area from large to small is as follows:shed>tailings>floatation workshop>old mining area.Under the C-RAG model,the total level of total carcinogenic risk of arsenic in the mining area was 1.17×10-4.Under the RBCA model,the total level of total carcinogenic risk of arsenic in the mining area was 2.38×10-4,both of which reached Grade ?-High risk level.Based on the C-RAG model and the RBCA model,there is a big difference in the average levels of total hazards of arsenic and antimony in the mining area.The average level of total arsenic hazards in the four regions under the C-RAG model was in the order of work area(10.72)>tailings(8.86)>flotation plant(3.37)>old mining area(0.43)Followed by the flotation plant(16.87)>Gong Peng area(12.95)>tailings reservoir(10.08)>old mining area(0.84);the average level of total arsenic hazards in the four areas under the RBCA model is the workshed area(2.19)>Tailings Storage(1.81)>Flotation Workshop(0.69)>Old Mining Area(0.082),The average level of total hazards for earthworms was flotation plant(3.51)>shed area(2.69)>tailing pond(2.10)>old Mining area(0.171).(5)under the two models,the difference in the contribution rate of the carcinogenic risk in the arsenic exposure pathway is small,and the difference in the contribution rate of the arsenic and antimony non carcinogenic risk varies greatly.According to the mine soil arsenic,antimony cancer risk and non cancer risk value,calculated the carcinogenic effects of soil arsenic mine under the risk control value should be controlled within 22.1 mg/kg,the non carcinogenic risk of soil arsenic risk control value should be controlled within 200 mg/kg,antimony soil risk control value should be controlled within 175.44mg/kg.