Impact of mining exploitation on sediments and water in the Batouri gold district (East-Cameroon)

Abstract

Artisanal and semi-mechanized gold mining in developing countries has raised significant concerns about the degradation of sediment and water quality. It is in this context that this study aims to assess the impacts of gold mining on the sediment and water quality of the Djengou watershed in eastern Cameroon. To do this, in addition to an intense bibliographic research, field and laboratory observations and investigations were carried out such as: in-situ measurement of physicochemical parameters, sampling of sediments and water in the dry season (May) and rainy season (August) during the year 2024, determination of total suspended solids (TSS) and analysis of heavy metals (Hg, As, Pb, Fe and Zn) of the collected samples. There are two modes of gold mining exploitation in the study area which are artisanal gold mining characterized by small motor pumps, sluices, pans, barrels, shovels and pick axes and semi-mechanized gold mining characterized by the use of mechanical shovels, and chemical products such as mercury for gold amalgamation. On the physicochemical level, the waters of the Djengou watershed (BVD) are slightly acidic to slightly basic (6.5 ≤ pH ≤ 7.3), weakly to moderately mineralized (145 ≤ EC ≤ 662μS/cm). Total suspended solids range from 3 to 681.5 mg/l, with an average of 225.5 mg/l. Seasonal and spatial variations in physicochemical parameters indicate severe pollution related to artisanal and semi-mechanized gold mining practices. The use of assessment tools such as the water quality index (WQI), the heavy metal pollution load index (HPI), the degree of contamination (DC) for water, the contamination factor (CF), the pollution load index (PLI) and the geo-accumulation index (Igeo) for sediments, revealed the presence of heavy metals such as Hg, As, Pb, Fe and Zn at concentrations higher than the WHO standard values. The latter have higher concentrations in the rainy season than in the dry season due to increased runoff and leaching. Heavy metal contamination of sediments and water objectively justifies the major problems (access to drinking and domestic water, health problems and extinction of aquatic species) encountered in this locality. Recommendations to mitigate these environmental and health impacts include drilling boreholes away from active mining sites, the use of natural filters (charcoal and sand), implementation of IWRM, sensitization and education of the local population to support water resource management.