Assessment of Metal Pollution in Water and Sediments in Gold Mining Areas in Mayo, Dalalang, Forage and Vounbiyao in Mayo Kebbi-Ouest, Chad

Abstract

Artisanal gold mining can affect aquatic and sedimentary environments through the mobilisation and discharge of metallic elements. This study assessed metal pollution in water and sediments from four gold mining sites in Gamboké, Mayo Kebbi-Ouest, Chad, namely Mayo, Dalalang, Forage and Vounbiyao. Wastewater and sediment samples were collected from the study sites and analysed by atomic absorption spectrometry to determine the concentrations of Hg, Cd, Pb, Ni, Co, Zn, Mn and Fe. Mercury was determined using a hydride generator coupled to atomic absorption spectrometry. Sediment quality was evaluated using the geoaccumulation index, enrichment factor, contamination factor, degree of contamination and ecological risk index, while water concentrations were compared with the standards used in the study. The results showed marked metal contamination, particularly by Hg and Cd. In sediments, Hg and Cd had the highest geoaccumulation values, while Pb, Ni, Fe, Zn and Mn generally showed negative Igeo values. The enrichment factor indicated very high enrichment of Hg and Cd, with the highest mercury enrichment at Mayo. The degree of contamination was very high at Mayo and moderate at Vounbiyao, Forage and Dalalang. Water samples contained elevated Hg, Cd, Pb, Ni and Fe concentrations, with mercury exceeding the reference limit at all sites. The findings indicate that artisanal gold mining contributes to metal pollution and requires mitigation measures to reduce environmental and health risks.