Evaluation of Hydrochemical Facies of Groundwater in Ajaokuta, North-Central, Nigeria

The total well-being of humans cannot be separated from the quality of water they consume. Therefore, hydrochemical evaluation of water resources in Ajaokuta area of Kogi Sate hosting a major iron and steel industry in North-Central, Nigeria, has been conducted. This was aimed at evaluating the sources and processes that emplaced the ions in the water. Twenty water samples were collected from boreholes and were subjected to physicochemical analysis using standard methods. Results showed that pH, EC and TDS ranged from 5.2 to 8.40, 0.22 to 5.20 µS/cm and 165–428 mg/L, respectively. The concentrations of the major cations in mg/L ranged from 20.80 to 53.40, 52.80 to 162.66, 3.50 to 13.70 and 2.30 to 12.30 for Na+, Ca2+, Mg2+ and K+, respectively, while the concentration of the anions in mg/L ranged from 0.22 to 1.22, 0.09 to 1.63, 0.01 to 12.18, 12.86 to 35.74 and 74 to 124 for NO3−, SO42−, Cl−, CO3− and HCO3−, respectively. These results are within the limits of World Health Organization (WHO) and Standards Organization of Nigeria (SON) guidelines. The concentrations of the heavy metals in mg/L ranged from 0.02 to 0.38, 0.02 to 0.5, 0.00 to 0.03 and 0.00 to 0.04 for Fe2+, Cr6+, As3+ and Pb2+, respectively. The elevated concentration of heavy metals in a few samples poses threat to the lives of people habiting the study area. The Piper trilinear for the water samples showed dominance of normal earth alkaline metals (Ca2+—Mg2+) with prevailing bicarbonate (− HCO3). The dominant hydrochemical facies is (Ca2+—Mg2+—HCO3) representing recently recharged water of meteoric origin. Durov diagram showed that mixed water type prevails in the study area indicating water with simple dissolution or mixing. The results obtained also suggests precipitation-induced chemical weathering along with dissolution of rock forming minerals.