Assessment of Environmental and Ecological Risks Associated with Heavy Metals in Agricultural Soils Affected by the Poura Mine in Burkina Faso, West Africa

Abstract

This study assessed the environmental and ecological risks associated with heavy metals in agricultural soils influenced by the former Poura mine in Burkina Faso, West Africa. Soil sampling was conducted around three potential contamination sources: Tailing 1, Tailing 2 and the cyanide tank. A total of 35 surface soil samples were collected from the 0–30 cm horizon, including 13 samples around Tailing 1, 11 around Tailing 2 and 11 around the cyanide tank. Sampling points were arranged at 200 m intervals along the four cardinal directions, while also considering the direction of surface-water flow. The concentrations of Cd, Cr, Cu, Ni, As, Zn, Pb and Mn were determined using ICP-OES. Pollution and ecological risk were evaluated using the contamination factor, geoaccumulation index, pollution index, degree of contamination, elemental risk factor and ecological risk index. The results showed marked spatial variability in metal contamination around the three sources. High contamination levels were identified near the cyanide tank, particularly at point S3, where the degree of contamination reached 1688.494. Tailing 2 also showed strong contamination, especially at W2, N2 and N1, with degree of contamination values of 1417.675, 477.695 and 150.152, respectively. Around Tailing 1, the highest contamination was observed at E3 and S1, with degree of contamination values of 1378.01 and 259.572, respectively. Arsenic and cadmium were the principal contributors to the highest ecological risk values. Overall, the findings indicate that the former Poura mine remains a significant source of heavy metal contamination in surrounding agricultural soils, with contamination patterns influenced by source location, runoff direction and local dispersion processes.