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<p>Artisanal gold mining in Nigeria’s Ile-Ife–Ilesha schist belt has triggered an unprecedented heavy metal contamination crisis, posing severe environmental and public health risks. Despite increasing reports of pollution, comprehensive geospatial and multivariate assessments of contamination patterns and sources remain limited, creating a significant knowledge gap in understanding heavy metal dynamics in the region. This study assessed the extent, sources, and health implications of heavy metal pollution in the Ile-Ife–Ilesha mining corridor using integrated geospatial and multivariate statistical analyses. Surface water samples exhibited alarmingly high Heavy Metal Pollution Index (HPI) values, reaching 43,376.9&#xa0;ppm, exceeding WHO guidelines by up to 500fold, driven by extreme cadmium (Cd ≤ 42,678&#xa0;ppm), mercury (Hg ≤ 7,659&#xa0;ppm), arsenic (As ≤ 4,029&#xa0;ppm), and lead (Pb ≤ 2,614&#xa0;ppm) concentrations. Sediment analysis revealed severe enrichment (Igeo ≤ 12.3 for Cd; ≤ 10.4 for Hg), among the highest globally for artisanal mining regions. Principal Component Analysis identified three pollution sources: (1) mining derived inputs (Pb Cd Cr, 48%), (2) lithogenic weathering (Co Ni, 29%), and (3) mercury amalgamation (18%). Strong correlations between chromium and cadmium (r = 0.715) and spatial clustering were confirmed by Moran’s I (&gt; 0.65, p &lt; 0.05). Hydrological assessment revealed strong surface&#xa0;water to groundwater connectivity (r ≈ 1; conductivity: 2–18 mS/cm), while weak correlation between HPI and sediment contamination (r = 0.21) suggests sediment buffering. Geospatial analysis identified Ilesha as the contamination epicenter, with mean HPI nearly double that of Ile Ife (p &lt; 0.01). Cadmium accounted for 85.1% of total HPI, while Pb and Hg posed neurotoxic and carcinogenic risks to approximately 500,000 residents. Although weakly acidic pH (6.1 ± 0.3) mitigates acid drainage, shallow sediments (≤ 1.5&#xa0;m) exacerbate aquatic degradation. Remediation strategies proposed include phosphate amendments, constructed wetlands, and SDG aligned environmental governance.</p>

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Heavy metal contamination driven by artisanal gold mining in the Ile-Ife–Ilesha Schist Belt, Nigeria: Geospatial assessment of pollution sources and hotspots

  • 期刊论文

  • 发表日期：

    2025年9月3日

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  • AbdulGaniyu Isah,
  • Olukole Adedeji Akinbiyi,
  • Ayodeji Hansen-Ayoola,
  • Nelson Chinaka Ayajuru,
  • Taoreed Adekunle Muraina,
  • Fasilat Olajumoke Rafiu

摘要

Artisanal gold mining in Nigeria’s Ile-Ife–Ilesha schist belt has triggered an unprecedented heavy metal contamination crisis, posing severe environmental and public health risks. Despite increasing reports of pollution, comprehensive geospatial and multivariate assessments of contamination patterns and sources remain limited, creating a significant knowledge gap in understanding heavy metal dynamics in the region. This study assessed the extent, sources, and health implications of heavy metal pollution in the Ile-Ife–Ilesha mining corridor using integrated geospatial and multivariate statistical analyses. Surface water samples exhibited alarmingly high Heavy Metal Pollution Index (HPI) values, reaching 43,376.9 ppm, exceeding WHO guidelines by up to 500fold, driven by extreme cadmium (Cd ≤ 42,678 ppm), mercury (Hg ≤ 7,659 ppm), arsenic (As ≤ 4,029 ppm), and lead (Pb ≤ 2,614 ppm) concentrations. Sediment analysis revealed severe enrichment (Igeo ≤ 12.3 for Cd; ≤ 10.4 for Hg), among the highest globally for artisanal mining regions. Principal Component Analysis identified three pollution sources: (1) mining derived inputs (Pb Cd Cr, 48%), (2) lithogenic weathering (Co Ni, 29%), and (3) mercury amalgamation (18%). Strong correlations between chromium and cadmium (r = 0.715) and spatial clustering were confirmed by Moran’s I (> 0.65, p < 0.05). Hydrological assessment revealed strong surface water to groundwater connectivity (r ≈ 1; conductivity: 2–18 mS/cm), while weak correlation between HPI and sediment contamination (r = 0.21) suggests sediment buffering. Geospatial analysis identified Ilesha as the contamination epicenter, with mean HPI nearly double that of Ile Ife (p < 0.01). Cadmium accounted for 85.1% of total HPI, while Pb and Hg posed neurotoxic and carcinogenic risks to approximately 500,000 residents. Although weakly acidic pH (6.1 ± 0.3) mitigates acid drainage, shallow sediments (≤ 1.5 m) exacerbate aquatic degradation. Remediation strategies proposed include phosphate amendments, constructed wetlands, and SDG aligned environmental governance.