Hydro-geochemical evaluation of groundwater quality in Akoko North West local government area of Ondo State, Nigeria

Abstract

A sudden geometric increase in population of Akoko North West Local Government Area of Ondo State has led to an increase in demand for water and harnessing of subsurface water reserve. A total of twenty six water samples obtained from both boreholes and hand-dug wells were analyzed for their physico-chemical characteristics with the aim of assessing their quality, usability and also to determine the level of their contamination in the local government which is dominated by granite gneisses, charnockites, and augen gneisses as the main rock types. The following physico-chemical properties were analyzed for in the samples collected: electrical conductivity (EC), pH, total alkalinity (TA), total dissolved solids (TDS), total suspended solids (TSS), acid neutralizing capacity (ANC) with major cations (Na+, Mg2+, Ca2+), anions (PO43-, HCO3-, SO43-) and several heavy metals (Zn2+, Fe2+, As+, Ni+, Pb2+, Cd+, Cu2+). The following results were obtained from the analysis: Zn2+ (0.109 – 0.437 ppm), Fe2+ (0.216 – 0.726 ppm), As+ (0.01 – 0.03 ppm), Ni+ (0.036 – 0.074), Pb2+ (0.003 – 0.010), Cd+ (0.002 – 0.007), Cu2+ (0.086 – 0.241) with appreciable abundances of PO43-, Cd+, Fe2+and Ni+ some exceeding while some others are below the WHO acceptable level for drinking water, thereby making it a serious source of concern as it indicates varying levels of faecal contamination (from leaky septic tanks, interception with pit latrines) and heavy metal liberation into the water consumed by the residents. It was also noticed that the water was fresh based on the analysis of the Total Dissolved Solids and the Pb2+ concentrations almost exceeded the standard permissible limit. Generally, it was concluded that the overall quality of the ground water is averagely good physico-chemically.