Soil contamination and soil-mediated human health risks associated with household coal combustion in residential areas of Zavkhan Province, Mongolia

Abstract. Soil contamination by heavy metals represents a growing environmental and public health concern in cold–dry rural settlements where coal-based household heating remains dominant. This study investigates how coal combustion alters soil element dynamics and associated human health risks by applying a process-oriented, integrated soil system assessment in a residential area of Uliastai city, western Mongolia.

Surface soils (0–10 cm) from 38 sites were analyzed using ICP-OES and ICP-MS to determine major and trace element concentrations. Multivariate statistical analysis (principal component analysis, PCA) was combined with contamination indices (enrichment factor and geo-accumulation index) and human health risk assessment to explicitly link contamination sources, transport pathways, soil retention processes, and potential human exposure.

Results reveal a clear separation between anthropogenically influenced metals (As, Pb, Cd, Zn, and Cu) and elements predominantly controlled by geogenic background conditions (Cr, Co, and Ni). Very high to extreme enrichment and geo-accumulation levels for As, Pb, Zn, Cd, and Cu indicate substantial anthropogenic alteration of surface soil metal pools. Comparison of soil, coal, and ash compositions identifies coal combustion ash as the primary source of metal enrichment, acting as a concentrated reservoir that is redistributed to soils via atmospheric deposition and surface processes. Human health risk assessment shows that the most enriched metals, particularly As and Pb, dominate both non-carcinogenic and carcinogenic risks, with inhalation and ingestion pathways contributing most strongly to potential exposure.

The findings demonstrate that soil contamination in Uliastai reflects systemic changes in soil functioning driven by household energy practices rather than isolated concentration exceedances. By integrating source identification, contamination intensity, and health risk within a unified soil system framework, this study provides mechanistic insight into soil–human interactions and offers a transferable approach for assessing soil impacts in coal-dependent rural environments.