Soil heavy metals in a typical coal mining cluster of Northern China: Pollution, source apportionment, and eco-health risks

Abstract

Summary Coal mining activities can alter soil heavy-metal accumulation and risk patterns. To identify pollution characteristics, sources, and ecological and health risks, 88 surface soil samples from Tongchuan Town, Ordos City, were analyzed using enrichment factor, potential ecological risk index, positive matrix factorization, soil physicochemical analysis, and Monte Carlo-based health risk assessment. Heavy-metal concentrations were generally low and regional pollution risk was controllable, although Cd exceeded the agricultural soil risk screening value at some sites. Cd and Hg showed local enrichment and dominated ecological risk, with over 60% of sites at moderate or higher risk. Industrial-traffic sources contributed the most (44.09%), followed by natural sources (34.06%), coal-related emission-atmospheric deposition (16.35%), and mining disturbance-agricultural inputs (5.50%). Soils were strongly alkaline, with low organic matter and nitrogen and potassium deficiencies. Health risks were acceptable; oral ingestion was dominant, Cr and As were key contributors, and children were more sensitive.