ABSTRACT:

Geochemical studies of Yola area of Northeast Nigeria were studied during a dry season period (November 2008). This was to determine the process controlling the water chemistry and to assess the quality of water. The results show that, based on ionic ratios, precipitation and water-rock interaction (silicate weathering) are the main controlling factors contributing to solute concentration in these areas. The main water types in the area include Mg2 - HCO3 - and Na -Cl- are the dominant ion types for the shallow groundwater, Mg2 -Cl-, Mg2 -HCO3 - and Na -HCO3 - for the deep groundwater and Na -Cl- for the surface water bodies. Equilibrium specification calculations revealed that the water samples are largely undersaturated with respect to calcite and dolomite in the water samples. Groundwater samples from the shallow groundwater indicate pH values (6.10 to 7.08) and Eh values (mean 0.72 volt) whereas those of the deep groundwater revealed pH range (6.60 to 7.80) and Eh values (mean 0.75 volt). They are slightly acidic to neutral, largely soft, clean waters with fairly low to moderate concentration of dissolved solids that fall within the international acceptable limits for drinking, domestic and irrigation purposes. However some samples indicate iron and nitrate values that are above the recommended limits and should be treated before use. Employing Electrical Conductivity (EC), Total Dissolved Solids (TDS), Sodium Adsorption Ratio (SAR),