Groundwater geochemistry and hydrochemical processes in the Egbako aquifer, Northern Bida Basin, Nigeria

Geoquímica e processos hidroquímicos de águas subterrâneas no aquífero Egbako, Bacia de Bida do Norte, Nigéria

ABSTRACT

Thirty-five groundwater samples from the aquifer were collected and analyzed for major cations and anions to understand the groundwater chemistry and hydrochemical processes in the Egbako aquifer. Laboratory studies identified the major ions while the results were analyzed using different graphical methods and ionic plots. The abundance of the major cations and anions are Ca²⁺>K⁺>Na⁺>Mg²⁺ and HCO₃^->NO₃^->Cl^->SO₄^2- respectively. The dominant hydrochemical facies are calcium-bicarbonate (Ca-HCO₃), sodium-bicarbonate (Na-HCO₃) and mixed calcium-sodium bicarbonate (Ca-Na-HCO₃) water types. Interpretation of bivariate and scatter plots indicate silicate weathering, simple dissolution and ion exchange as the dominant processes in the aquifer. Saturation indices reveals evaporites (halite, gypsum and anhydrite) undersaturation, supersaturation in most samples with respect to silicates (quartz and kaolinite) and few samples for carbonate (calcite, aragonite, dolomite). Assessment of the water quality indicate that they are chemically suitable for human consumption except in the agricultural fields of southwestern areas where high nitrate concentration is present.

Keywords:
Water quality; Saturation index; Groundwater evolution; Bida Basin; Hydrochemical processes