Eco-environmental assessment and genetic analysis of heavy metal pollution in the soil around the abandoned tungsten-molybdenum mine area in Inner Mongolia

In order to study the heavy metal pollution characteristics, potential ecological risks and causes of the soil in the abandoned tungsten and molybdenum mine area in Chifeng City, Inner Mongolia, the authors collected 83 surface soil samples and 6 soil borehole samples. The spatial distribution of As, Cd, Cr, Cu, Ni, Pb, Mo and Zn was studied by ArcGIS spatial interpolation analysis. Heavy metal disturbance index was constructed to study the anthropogenic pollution degree. The geo-accumulation index method was used to verify the pollution degree of heavy metals in the mining area. The correlation analysis was used to judge the sources of heavy metals and discuss the causes of pollution. The results show that the average content of As, Cd, Cu, Pb, Zn and Mo in the soil around mining area is obviously higher than the background value around the mining area, and the high content is mainly distributed around the tailings pond, and the main source is mining activities of the mine. Cr and Ni are basically pollution-free, and the main source is the weathering of the parent rock. Through the calculation of the heavy metal disturbance index function, it is found that the use of regional background values to evaluate heavy metal pollution around the mining area exaggerates the pollution of heavy metals by the mining activities of the mine. The heavy metal pollution in the soil around the mining area is caused by the "double-drive mode"under the combined action of natural heavy metal enrichment and mining activities. The degree of heavy metal pollution in the soil around the tailings pond gradually decreases with the increase of the horizontal distance from the tailings pond and the increase of the depth. At the same time, the richness of precipitation is a key factor affecting the migration capacity of heavy metals. However, the mine is located in an area where precipitation is scarce, which makes the tailing pond exhibit a limited range of heavy metal pollution in the surrounding soil and slight impact on the ecological environment.