Disturbance and Natural Recovery of Surface Water Quality in a Semi-Industrial Gold Mining District (Eséka, Central Cameroon): A Tropical Earth System Perspective

Surface water quality in the Eséka gold district (Central Cameroon) was investigated to understand the coupled impacts of semi-industrial mining and tropical Earth surface processes. Physicochemical parameters and heavy metal concentrations were quantified across a chronosequence of actively mined and abandoned sites. Mining activities significantly lowered water pH, increased water temperature, and reduced dissolved oxygen concentrations. High concentrations of Pb, Cd, As, and Cr are linked to sulfide oxidation and leaching of host minerals (e.g., galena, arsenopyrite) in waste rock. The Water Quality Index (WQI) ranges from good (at older, abandoned sites) to very poor (at active mines), suggesting that natural recovery processes may improve water quality at some mining sites in humid tropical environments. Health risk assessment identified ingestion as the primary exposure pathway. The cumulative Hazard Index (HI) for children was 29.55, indicating significant non-carcinogenic risk resulting from the combined contributions of Pb, As, Co, and Cr. Adults face elevated risks primarily from As and Co. These findings provide a conceptual model of mining-induced disturbance and natural attenuation in tropical catchments, with implications for global change remediation strategies and sustainable development in resource-dependent regions.