Heavy Metals Contamination and Ecological Risk Assessment in Illicit Mined Soils at Noyem and Nyafoman in the Birim North District, Ghana

Abstract

Williams Ampadu Oduro* and Eunice Eduful

Illegal mining / “galamsey” is a major source of soil pollution in Ghana, but ecological risk levels at local sites remain poorly quantified. This study assessed heavy metal contamination in soils from three illicit mining sites at Noyem and Nyafoman in the Birim North District, using pristine soils as controls. A total of 40 samples were collected and analyzed for Cu, Zn, Fe, Hg, and Cd concentrations using atomic absorption spectrometry. Results were summarized in tables and a bar graph, and contamination was evaluated through geoaccumulation index (Igeo), contamination factor (CF), pollution load index (PLI), enrichment factor (EF), and ecological risk index (RI).

The mining sites recorded markedly higher concentrations of Zn (40 ppm), Fe (5 ppm), Hg (0.04 ppm), and Cd (0.07 ppm) compared with the control (Zn: 2.4 ppm; Fe: 0.3 ppm; Hg: 0.008 ppm; Cd: 0.0004 ppm). Conversely, Cu was slightly higher in the control soils (0.70 ppm) than in the mining sites (0.15–0.21 ppm). Igeo values indicated extreme Cd contamination (>6), strong Zn and Fe contamination (>3), and moderate Hg contamination, while Cu showed no enrichment. PLI values exceeding unity (8–10) confirmed overall soil pollution. Cd exhibited the highest CF (43–66) and Eri (4200–6100), followed by Hg (175–210), resulting in composite RI values (4400–6400) that signify very high ecological risk across all sites.

These findings demonstrate that illicit mining in Noyem and Nyafoman has significantly increased soil contamination, with Cd and Hg posing the greatest ecological threats. Stronger regulation of mining practices, mercury phase-out, and remediation strategies such as phytoremediation and soil amendments are recommended to mitigate risks and protect community health.

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