Distribution characteristics and pollution assessment of soil heavy metals over a typical nonferrous metal mine area in Chifeng, Inner Mongolia, China

The spatial distribution characteristics of heavy metals (As, Cd, Cu, Pb, and Zn) in a typical lead–zinc mine located in Inner Mongolia were studied by applying mathematical statistics and the ArcGIS spatial interpolation analysis. The Nemerow index and potential ecological-risk index were applied to the pollution assessment of heavy metals from the soil in accordance with the Environmental Quality Standard for Soils of China (grade 2) and background value for heavy metals. Results indicated that the average concentrations of As, Cd, Cu, Pb, and Zn were 82.39, 1.01, 33.47, 96.47, and 254.64 mg kg⁻¹, respectively, and these values were higher than the regional background values in the studied scale. The average single-factor index (P_i) values of As, Cd, Cu, Pb, and Zn were 6.46, 6.61, 1.81, 3.93, and 4.02, respectively, when the regional background value was used as the assessment standard. Based on the Nemerow pollution index (P_N), all areas over the mine were in moderate or heavy pollution. The result of potential ecological-risk assessment showed that the mining-activity area and its surrounding areas were in the moderate risk level or above. Pollution was concentrated in the centre mining-activity area of tailing reservoir, concentrator, and waste dumps. The degree of heavy-metal pollution decreased with increased distance from the mining-activity area.