The Integrated Spatial Ecological Risk Assessment of Heavy-Metal Contamination in Arid Mining-Influenced Region in Central Asia

Abstract

The spatial distributions of the potential ecological risk index (RI) and the geoaccumulation index (Igeo) in soils of the Zhetysu region (Kazakhstan) were examined. The enrichment factor ranged from 39.4 for cadmium to 21,481 for nickel. There are few non-ferrous metal enterprises and mineral deposits located in the region. Soil sampling was conducted at 54 locations across the region. The contamination indices were calculated based on the concentrations of four heavy metals in the soil in 2025: copper (Cu), lead (Pb), cadmium (Cd), and nickel (Ni). The RI index varied across the study area within range of 53–353, with an average value of 129. The main points of high environmental risk are the Balkhash Lake’s eastern coast (RI = 318) and industrial city Tekeli (RI = 353). The Igeo values were as follows: Cu −0.61–3.82 (mean: 2.07); Pb −0.58–3.35 (mean: 0.49); Cd −2.91–2.15 (mean: −0.11); and Ni −4.23–4.17 (mean: 0.43). The transport of contaminants occurs under the influence of the wind regime and water erosion processes. Lead, cadmium, and nickel have a variation coefficient greater than 50, indicating metal particle transport from adjacent areas. Wind patterns in certain areas of the region determine the distribution of foci of high heavy-metal concentrations in the soil.