Assessment of Natural Radioactivity in Groundwater from Basement Complex Aquifers in Ekiti State

Groundwater from basement complex aquifers in South West Nigeria may contain elevated concentrations of naturally occurring radioactive elements including uranium, radium, and radon derived from the dissolution of granitic country rock. Regular radiological monitoring of groundwater used for drinking is essential for protecting public health in communities dependent on borehole water. This study assesses the natural radioactivity of groundwater samples from 35 boreholes in Ekiti State using gross alpha-beta counting and high-purity germanium gamma spectrometry. Uranium-238, Ra-226, and Th-232 activity concentrations are quantified in filtered and acidified water samples. Gross alpha activity ranges from 0.02 to 0.85 Bq per litre, and gross beta activity ranges from 0.08 to 1.42 Bq per litre across the sampled boreholes. Fourteen percent of samples exceed the WHO provisional guideline value for gross alpha activity of 0.5 Bq per litre. Uranium concentrations in the most elevated samples reach 28 micrograms per litre, approaching the WHO chemical quality guideline of 30 micrograms per litre. The study recommends inclusion of uranium and gross alpha testing in the Ekiti State Rural Water Supply and Sanitation Agency's routine borehole water quality programme. Keywords: radioactivity, groundwater, basement complex, Ekiti State, uranium