Groundwater quality assessment from parts of the basement complex area of oshogbo, southwestern nigeri

Abstract

The increasing population in Oshogbo metropolis with the attending rise in human generated waste and environmental pollution has created a quest in assessing the quality of the available groundwater. Therefore, drinking water must meet the desirable quality and standards, and there is need for thorough monitoring of the quality available for drinking purposes. A total of twenty (20) samples of water were randomly collected from borehole drilled into the basement complex rocks. The temperature of water samples ranges between 26°C and 29°C and an average of 27.9°C. The range of pH is from 6.7 to 7.8 with mean value of 7.2 which indicated that the water is neutral. The TDS was low and ranges between 21.3 to 50.5 mg/l with a mean value of 35.8 mg/l. Calcium has concentration ranging between 1.3mg/l and 7.2mg/l. Concentration of Magnesium  ranges between 1.5mg/l and 18mg/l while concentration of sodium ranges from 1.2mg/l to 8.9mg/l and Potassium ranges from 1.2mg/l to 4.3mg/l. Chloride concentration ranges from 2.1mg/l to 8.2mg/l and Sulfate concentration ranges between 0.4mg/l and 12.0mg/l while Bicarbonate ranges from 3.7mg/l to 14.3mg/l. The geochemical data for both cation and anion shows that: Mg>Na>Ca>K and HCO₃>SO₄>Cl. Mg-HCO₃ occupied 30% of the water type analyzed, Mg-Cl took 15%, Ca-HCO₃ took 25%, while Mg-SO₄ took 30%.  The major cations from the water facies indicate that Calcium and Magnesium are geogenic in origin and are as a result of interaction of water and the underlying rocks are reflective of bedrock dissolution. . Concentration of Cl^-, HCO₃^- and SO₄^2-can be attributed to increasing population and industrial growth within the metropolis, although the concentration is not when compared with WHO standard and Nigeria Standard standard desirable and permissible limits.