Geochemical and Isotopic Insights into Groundwater Dynamics and Sustainable Management in Mount Cameroon's Volcanic Aquifer

Abstract

Groundwater resources under tropical climates face escalating pressures from climate change and anthropogenic activities. The eastern flank of Mount Cameroon a critical agro-industrial zone exemplifies these challenges, yet comprehensive assessments integrating hydrogeochemical and isotopic evidence remain limited. 50 groundwater samples (boreholes, springs, wells) and 14 precipitation events. In-situ parameters (pH, EC, temperature) were measured followed by laboratory quantification of major ions (ion chromatography), trace elements (ICP-MS), and stable isotopes (δ¹⁸O, δ²H; cavity ring-down spectroscopy). Hydrochemical facies and recharge processes were evaluated using Aquachem, Piper diagrams, and Local Meteoric Water Line (LMWL) regression. Three dominant hydrochemical facies were identified: Ca-Cl (74%), indicating ion exchange and evaporite dissolution; Ca-HCO₃ (20%), reflecting active recharge and carbonate weathering; and mixed Ca-Mg-Cl (6%). Groundwater exhibited low mineralization (mean TDS: 102.24 mg/L; EC: 314.94 µS/cm) but localized Fe (≤5.31 mg/L) and Mn (≤3.28 mg/L) exceeded WHO thresholds. Isotopic signatures (δ¹⁸O: −2.90 ± 0.46‰; δ²H: −11.39 ± 1.99‰) confirmed precipitation as the primary recharge source, with d-excess values (9.96‰) indicating minor evaporation. A 15% precipitation decline (1991–2020) correlated with enriched δ¹⁸O-Cl⁻ trends, signalling climate-induced recharge vulnerability. The aquifer’s sustainability is threatened by climate-driven precipitation variability, geogenic contamination (Fe/Mn), and agricultural pollutants. Targeted monitoring of shallow zones, protection of fracture-mediated recharge systems, and climate-resilient policies are imperative for water security. This study establishes a critical baseline for sustainable management of volcanic aquifers in tropical regions.