Geogenic Imprint on Groundwater and Its Quality in Parts of the Mamfe Basin, Manyu Division, Cameroon

Abstract

Groundwater studies in parts of the Mamfe basin are sparse and the Mamfe area has the highest population density in the Mamfe basin. An in-depth study of groundwater rock interaction and groundwater quality is of vital importance. This same part of the basin is the economic centre and as such development of businesses in this area requires knowledge of the groundwater quality. Therefore, this study was undertaken to determine the input of the rock formations on the groundwater solute chemistry and groundwater domestic-agro-industrial quality using hydrogeochemical tools and physicochemical parameters: Ionic ratios, Gibbs diagrams, Piper diagrams, Durov diagrams and water quality indices. From physicochemical parameters, in the rainy season, pH ranged from, 4.3 - 8.6; EC, 3 - 1348 µS/cm; Temperature, 24.4˚C - 30.1˚C and TDS, 2.01 - 903.16 mg/L and in the dry season, pH ranged from 5.5 - 9.3; EC, 6 - 994 µS/cm; Temperature, 25˚C - 38.6˚C and TDS, 4.02 - 632.48 mg/L. Forty groundwater samples: 20 per season, wet and dry were analysed. The major ions fell below WHO acceptable limits for both seasons. The sequences of abundance of major ions were: Ca2+ > K+ > Mg2+ > > Na+, Cl− > > > > NO3 in wet season and Ca2+ > Mg2+ > K+ > Na+, > Cl− > > > in dry season. Ion-exchange, simple dissolution and uncommon dissolution processes determined groundwater character. Groundwater ionic content was as a result of ion exchange from rock-weathering. Water types are: CaSO4 and MgHCO3 in both seasons. Hydrogeochemical facies are Ca-Mg-Cl-SO4 and Ca-Mg-HCO3. SAR for wet season 0.05 - 0.06 and dry season 0.00 - 0.05, %Na wet season 3.64 - 16.59 and dry season 1.22 - 10.97, KR wet season 0.01 - 0.02 and 0.00 - 0.02 dry season, PI wet season 0.89 - 68.63 and dry season 18.75 - 73.35, MAR wet season 13.3 - 67.88 and dry season 27.02 - 77.01, WQI wet season 0 - 70.79 and 0 - 276.60 dry season, RSC wet season −4.59 to −0.33 and dry season −5.13 - 0.31 and groundwater was excellent-good for irrigation purposes. Some physicochemical parameters: pH, EC and TDS exceeded permissible limits.