Spatial distribution and health risk assessment of toxic metal(oid)s in soils of coal mining areas of the Salt Range, Punjab, Pakistan

Abstract

Long-term coal mining operations have been linked to increases in HM concentrations in subterranean soils, which degrades soil quality. The clusters of coal mines and mine tailings considerably increase metal(loid)s concentrations in the surrounding soils and air of the Eastern (ESR), Central (CSR), and Trans-Indus Salt Range (TSR). The present study was conducted in this scenario to ascertain the occurrence and dispersion of toxic metals from mine tailings to different environmental components and their pollution load in soils and possible risk. The geochemical characterization of the soil, coal waste, and dust particulate matter revealed that waste samples are highly enriched in As, Cd, Pb, Fe, and Zn. In terms of soil quality standards, geo-accumulation index (Igeo), enrichment factor (EF), and contamination factor (CF), Fe, Mn, and Zn are extremely contaminated. However, As, Cd, Co, and Cr show moderate contamination. These harmful soil contaminants, primarily originate from coal-associated tailings. Further, the principal component analysis, multiple linear regression (PCA-MLR), and agglomerative hierarchical clustering (AHC) signify that mineralization and weathering of sulfide and carbonate minerals within the coal wastes and lithological units of the present study area cause the release of environmentally sensitive trace elements, which upon dispersion, leaching, and atmospheric deposition enters the air and soils of the present study area. We propose that higher HI index of Co (4), Fe (35), Mn (11), and Zn (13) values can be a significant human health concern.