Geostatistical analysis for characterization of groundwater quality in Igbokoda coastal aquifer of Dahomey Basin

Thirty-one samples of groundwater were collected in the study area and the samples collected were carried to Adekunle Ajasin Research laboratory where each sample was analyzed for 27 parameters.Anions concentrations were determined by titration while heavy metals by Atomic Absorption Spectrophotometer and sodium and potassium by flame photometer.Descriptive, correlation coefficient, cluster, and factor analyses were the geostatistical methods used for the interpretation of the data.The aim is to determine the spatial variability of groundwater samples and their chemical evolution.The results showed that the major pollutants in the groundwater samples were Mg2+ and Cl-due to saltwater intrusion from the Atlantic Ocean, iron, oil, and grease.Cluster analysis classified water into 3 groups; fresh, intermediate, and polluted water due to their geochemical and location characteristics.There were 4 factor analyses; factor 1 indicated high loading of magnesium and chloride.Magnesium and chloride were responsible for the groundwater pollution and are likely to be due to saltwater intrusion.Factor 2, showed a high loading of calcium and calcium hardness.Observed temporary hardness was caused by calcium hardness.Factor 3, exhibits a high loading of sodium and potassium which may be due to saltwater intrusion.Factor 4, showed high loading of manganese and zinc and low loading of sulphate.Manganese and zinc might be derived from ores.Some of the groundwater samples are good for drinking but those in locations 3, 4, 5, 20, 21, 21, 23, and 28 which were polluted should be treated or discarded to avoid public health hazards.