Environmental effects of Gold mining in Burundi : a case study of Butihinda Commune, Muyinga Province, North Eastern Burundi

Abstract

The study was conducted in Butihinda Commune, Northeastern Burundi, to evaluate the environmental effects of gold mining by assessing contamination levels of selected heavy metals in springs, streams, and soils proximal to mining waste and tailings. A total of 10 rock, 15 soil (seven from near the mining waste, the other seven from near the tailings stockpiles, and one baseline soil sample), and five water samples were collected during the wet season. Mapping, petrographic analysis, X-Ray Fluorescence (XRF), and Atomic Absorption Spectrometry (AAS) were used to establish the lithology, identify gold-associated minerals, and determine the Contamination Factor (CF) and Heavy Metal Pollution Index (HPI). Quartzite was the dominant lithology, composed mainly of quartz with minor sulphide minerals such as arsenopyrite, chalcopyrite, and pyrite. The X-Ray Fluorescence results showed elevated concentrations for Fe₂O₃ (16.24-39.47 wt.%), As₂O₃ (0.01-0.26 wt.%), Cr₂O₃ (0.05-0.09 wt.%), NiO (0.04 wt.%), CuO (0.01-0.18 wt.%), PbO (0.13 wt.%), and SiO₂ (64.90-97.28 wt.%) in most rock samples, reflecting both natural geochemical enrichment and hydrothermal recrystallization within shear zones. Soil samples near mining waste exhibited very high CF values for As (CF = 15.71) and Cu (CF = 7.42), while those near tailings had high CF values for Ni (CF = 18.59), As (CF = 58.57), and Cu (CF = 14.57), indicating strong anthropogenic input. Water quality assessment revealed that spring waters had an HPI of 1.92, classifying them as excellent potable water (HPI < 50), whereas the Rugomero stream recorded an HPI of 3,709.58, rendering it unsuitable for human consumption (HPI > 300) according to WHO (2017) standards. The extreme HPI in the stream was attributed to elevated concentrations of Fe (3.80-79.12 mg/L), As (0.040 mg/L), Cd (0.216 mg/L), and Hg (0.140 mg/L), mainly from artisanal gold extraction introducing these toxic elements in Rugomero stream. Overall, the findings demonstrate that Butihinda’s bedrock naturally contains high levels of Fe, As, Cu, Ni, and Cr due to its quartzite-sulphide mineral assemblage, while Hg contamination is primarily anthropogenic. Poor management of mining waste and tailings significantly exacerbates soil and water pollution in the Butihinda gold mining areas, posing environmental and public health concerns.