Geostatistical and geochemical assessment of illegal artisanal mining impacts in Southern Hamisana, Sudan

Abstract

Artisanal and small-scale illegal mining, characterized by unregulated and environmentally destructive extraction methods, may pose severe environmental impacts. Heavy metal (HM) contamination from artisanal mining in Southern Hamisana, Sudan, was systematically investigated and evaluated. This study assessed HM concentrations, spatial distribution, sources, contamination levels, and associated health risks in 30 surface soil samples using geochemical analysis, statistical techniques, and risk assessment models. Geochemical analysis revealed mean concentrations of 757, 111, and 27 mg/kg for As, Pb, and Hg, respectively, significantly exceeding global background levels. Pearson correlation and Principal Component Analysis (PCA) were employed to differentiate distinct anthropogenic sources, primarily linked to illegal mining activities, with three components: PC1 (Ni, Cr, Cu); PC2 (As, Hg); and PC3 (Pb, Cd). Pollution indices, including the geoaccumulation index (I_geo) and contamination factor (CF), indicated severe contamination, particularly for As (I_geo up to 5.54, CF up to 108.31) and Hg (I_geo up to 6.28, CF up to 116.25). The ecological risk index (RI) highlighted high ecological risk (RI > 600) for Hg and As, with an average RI value of 1500 and a maximum of 5744 at site G17. Health risk assessments revealed significant non-carcinogenic risks for children, with hazard quotient through ingestion (HQ_ing) values of 3.23E+13 for As and 1.15E+12 for Hg, and carcinogenic risks with total carcinogenic risk (TCR) values of 1.46E+10 for As. This evaluation highlights the urgent need for stringent regulatory frameworks and remediation to counter artisanal mining impacts, offering vital insights for effective management and ecosystem restoration in Southern Hamisana.