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.
Keywords: Factor analysis, cluster analysis, hydrogeochemical, Dahomey basin,
groundwater
