Study On Ecological Risk Prediction And Early Warning Of Soil Heavy Metal Pollution In A Typical Mining Area In Inner Mongolia

In recent years,long-term mining activities have led to more and more serious environmental problems caused by the accumulation of heavy metals in soils such as cultivated land and forest land around the mining area.The time and space prediction and early warning research of heavy metal pollution in soil is of great significance for the prevention and control of soil environmental pollution and the realization of optimal utilization of regional soil resources.This research plan takes the land of a typical mining area such as a lead-zinc mine in Chifeng City,Inner Mongolia Autonomous Region as an example.For the mine and nearby land,a number of soil samples at different depths are collected,and the BP neural network and gray prediction simulation are used to conduct the research.The spatial and temporal estimation of the concentration distribution of heavy metals in the land in the study area is carried out,and the ecological risk of heavy metals in the study area is assessed and early-warned by the geoaccumulation index method and the potential ecological risk index method,combined with the ecological risk index method.This paper attempts to provide a basis for research on the prevention and control of heavy metal pollutants in mine land.The main research conclusions are as follows:Taking the soil environmental pollution risk detection value in the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Management and Control Standards"(GB15618-2018)as the comparison criterion,the content of As and Cd in the lower three layers of the soil surface in the study area all exceeded the standard seriously,and Cu,Zn surface soil content exceeded the standard to varying degrees.As and Cd have higher enrichment than other heavy metal elements.Evaluation of the status of heavy metal pollution From the perspective of the entire study area,Pb and Zn belong to the non-pollution level,Cu is slightly polluted,Cd is moderately polluted,and As is slightly polluted.Ecological risk assessment of heavy metals From the perspective of the entire study area,As and Cd belong to high potential ecological risks,and contribute greatly to the environmental pollution of the entire study area,while Cu,Pb,and Zn belong to low potential ecological risks.The comprehensive ecological risk of heavy metals in the study area belongs to the medium potential ecological risk.The toxic heavy metal substances in the land cause harm to the natural environment and various natural environments in the development.The ecological environment safety factor of the scientific research area is general,and there is a certain environmental threat.The results of BP neural network simulation and spatial distribution prediction of heavy metal concentrations in the soil in the study area show that the contents of As,Cu,Zn,Cd in the surface,middle and lower layers of the soil all exceed the standard to varying degrees,and the surface soil of Pb is slightly polluted.The contents of Cr and Ni in the soil surface layer,middle layer and lower layer did not exceed the standard.Among them,As,Cd and Cu are seriously exceeding the standard,and the area exceeding the standard is wide,and the content of As,Cd and Cu in some areas has reached 80 times,25 times and 7 times of the risk screening value of agricultural land,respectively.The time prediction results of the heavy metal content in the study area by the grey prediction model show that the As and Cu content will decrease in the mining repair demonstration area in the next three years,and the Cu content will drop to within the risk screening value in some areas by 2024;As and Cu content It continued to increase in the unrestored areas of the surrounding farmland and mining areas,while it basically stabilized in the concentration of residents and forest land.The Zn and Cd content decreased in the mining remediation demonstration area,while the Zn content decreased to within the risk screening value by 2024.The content of Zn and Cd continued to increase in the unrepaired areas of the mining area,but increased slowly in the forest land and surrounding farmland.The Pb content in the restoration demonstration area of the mining area shows a downward trend,and will fall within the risk screening value by 2024;in the unrepaired area and forest land of the mining area,it shows an increasing trend and slightly exceeds the standard,and the concentration of residents and other areas such as surrounding farmland tend to be stable.The ecological risk early warning results show that in the study area,Pb is at the no-alarm level,Cu and Zn have reached the early-warning level,Cd has reached the medium-alarm level,and As has reached the serious-alarm level.The research area as a whole is at the serious warning level of serious damage to the natural environment,large ecological problems,many natural disasters,and many disasters.Five heavy metals such as As,Cu,Pb,Zn,and Cd in the study area all exceeded the standard in different ranges and degrees.The spatiotemporal prediction results showed that the content of heavy metals in the restoration demonstration area was reduced,and the restoration effect was better.Based on the results of early warning,it is suggested that soil remediation technology can be actively adopted in the surrounding farmland and other areas of the study area under the condition of controlling pollution sources to ensure the reduction of environmental pollution and the harm to human health.