Spatial distribution, contamination levels, and health risk of potentially toxic elements in surface soils of an industrial—urban area in northwestern Mexico: a case study from La Paz, Baja California Sur

This study presents a comprehensive evaluation of potentially toxic elements (PTEs) contamination in surface soils of La Paz, Baja California Sur, Mexico, integrating geochemical, mineralogical, and magnetic analyses to identify contamination levels, spatial patterns, and potential health risks. Concentrations of Zn, V, Cr, Pb, Cu, Ni, As, Co, Sb, and Cd frequently exceeded local geochemical background values, with V and Ni particularly elevated near the heavy fuel oil fired (CTPP) and heavy fuel oil/diesel (CCI) power plants, consistent with emissions from fuel combustion. Spatial distribution analysis revealed that point sources dominated the signatures of V and Ni, while diffuse sources, such as vehicular traffic, contributed to elevated Sb, Zn, and Cu, especially along highways and in residential parks. Mixed-source elements (Cr, Pb, Co, As) showed overlapping industrial and urban signatures, with prevailing north-northwest winds likely enhancing contaminant dispersion. Soil color attributes and low frequency-dependent susceptibility indicated the predominance of coarse anthropogenic magnetic particles. Human health risk assessment showed no non-carcinogenic risk for adults, but hazard indices for children exceeded the safe threshold across all land uses, with the highest value at CTPP (HI = 2.22). Total cancer risk values remained within acceptable limits, although As contributions near CTPP approached the upper boundary. These findings highlight the persistent influence of industrial and urban activities on soil quality and underscore the importance of targeted monitoring and mitigation strategies to protect at-risk populations.