Spatial distribution and pollution assessment of potentially toxic elements in stream sediments of the Luis Moya region, Central Mexico: Evidence from mining-affected areas

The main activities in the Luis Moya region of central Mexico are agriculture and tourism; however, a long history of mining may have enriched the surroundings with potentially toxic elements (PTEs), including As, Cd, Cr, Sn, and Pb. Areas of PTE enrichment were identified using stream sediments as the sampling medium. Stream sediments (top 5 cm) were collected from 20 sites throughout this region, and their metal concentrations were determined using X-ray Fluorescence (XRF). Sediment data of 50 additional sites, collected in 2001 by the Mexican Geological Survey, were incorporated as complementary historical data. The data were examined geochemically and spatially to identify concentration patterns and delineate contamination hotspots. A sharp increase in concentrations near mine wastes was observed, with 12-fold and 40-fold increases for As and Pb, respectively, compared with a two-fold increase for Cr. The geoaccumulation index (Igeo) and enrichment factor (EF) identified hotspot regions with elevated pollution levels for Pb, Zn, and As. Cd and Sn were below the detection limits of XRF. The highest pollution levels were observed near the historical Real de Angeles mines, with Pb and Zn showing highly localized pollution, whereas the associated As and Cd were more dispersed. In contrast, Cr hotspots were less pronounced and occurred in a different location, suggesting a different geochemical influence from that affecting As, Pb, and Zn. The study fills a gap in assessing pollution near mining sites in an understudied area, provides a baseline for future environmental monitoring and risk assessment, and identifies priority areas to support targeted management and remediation strategies.