Geoenvironmental impacts of artisanal and semi-mechanized gold mining on surface water and sediment quality in the Batouri Gold District, East Cameroon.

Artisanal and semi-mechanized gold mining in developing countries poses serious threats to surface water and sediment quality. This study evaluates the geoenvironmental impacts of gold mining on the Djengou watershed in Batouri, East Cameroon. The methodology adopted consisted of measurement of physicochemical parameters, water and sediment sampling during the dry season (May 2024) and rainy season (August 2024), determination of total suspended solids (TSS), and heavy metal analysis (Hg, As, Pb, Fe, Zn). Mining activities in the watershed are conducted through two modes: (i) artisanal mining, using small motor pumps, sluices, pans, barrels, shovels, and pick axes, and (ii) semi-mechanized mining, involving mechanical shovels and chemicals such as mercury for gold amalgamation. Physicochemical analyses revealed that water in the Djengou watershed is slightly acidic to slightly basic (pH 6.5-7.3) and weakly to moderately mineralized (EC 145-662 µS/cm), with TSS ranging from 3 to 681.5 mg/L. Seasonal and spatial variations indicate significant pollution linked to mining activities. Water quality index (WQI) and heavy metal pollution index (HPI) revealed heavy metals exceeding WHO guideline values at mining-impacted sites. While mercury, lead, and iron concentrations were generally higher during the rainy season due to increased runoff and leaching, arsenic, the dominant contributor to human health risk, was higher during the dry season, resulting in overall non-carcinogenic and carcinogenic health risks via water exposure that were highest under low-flow, dry-season conditions (HI up to 4989 for children at the active mining site). Sediment exposure posed comparatively low non-carcinogenic risk (HI < 1 at all sites). Carcinogenic risk from arsenic and lead exceeded the USEPA acceptable threshold (1 × 10-4) at all water sampling sites (up to 3.3 × 10-1), but remained within or near the acceptable range for sediment. Heavy metal contamination explains the major challenges in the region, including limited access to safe water, health hazards, and threats to aquatic biodiversity. Mitigation measures proposed include drilling boreholes away from mining sites, using natural filters (charcoal and sand), implementing Integrated Water Resources Management (IWRM), and raising community awareness to promote sustainable water resource management.