Multivariate assessment of groundwater quality in the basement rocks of Osun State, Southwest, Nigeria

Groundwater is a major source of drinking water in many rural and urban areas of developing nations. Pollution of groundwater from diverse sources is an issue of concern due to inherent health problems. This study assessed the possible contamination source to groundwater quality in the basement rocks of Osun State, South-Western Nigeria using multivariate analyses of Principal Component Analysis (PCA) and Cluster Analysis (CA). The secondary data from 536 wells across the 30 Local Government Areas in the State were collected from the Rural Water and Environmental Sanitation Agency (RUWESA). The groundwater data include pH, temperature, turbidity, oxido-reduction potential, total dissolved solids, electrical conductivity, total alkalinity, magnesium hardness, calcium hardness, total hardness, free chlorine, total chlorine, chloride, fluoride, nitrate, nitrite, iron, manganese and zinc. The data were subjected to simple and inferential statistics using the Statistical Package for Social Sciences (SPSS vs. 21.0). The mean results of groundwater parameters such as nitrate and Mn were higher than the World Health Organisation (WHO) limits of 0.4 and 10 mg/L, respectively. The results of the PCA and CA revealed possible sources of pollutants to the groundwater quality as weathering of bedrocks, leachate from septic tanks and dumpsites, runoff of materials, hardness, nutrients from agricultural lands, and chlorine pollution.