Investigation of Radon Activity Concentration in Groundwater Samples from Ondo State, Southwestern Nigeria and Estimation of Corresponding Effective Dose

Abstract

This research work investigates radon concentration levels in ground water samples from the Akoko region of Ondo state, Nigeria and the estimation of annual effective dose due to ingestion of water from these sources. A total of seventeen groundwater (borehole and hand dug wells) samples collected from different locations within the study area were collected using standard methods. The radon concentrations in all the samples were analyzed using Liquid Scintillation Counter (LSC). The activity concentration of radon in the water samples ranged `from 12.61 Bq/L to 57.50 Bq/L and 10.30 Bq/L to 41.89 Bq/L with mean values of 28.01Bq/L and 25.34Bq/L respectively for Boreholes and wells. The annual effective dose due to ingestion of raon from the borehole samples were found to have mean values of 0.20, 0.40 and 1.40 mSv/y for adults, children and infants respectively. For well water samples, mean values of 0.19, 0.37 and 1.29 mSv/y were found. The results of radon activity concentration were compared with the maximum contaminant level of 11.1 Bq/L set by United States Environment Protection Agency and it was observed that 94% of the samples exceeded the value. Also, all of the annual effectice doses estimated were above 0.1 mSv/y set by the World Health Organisation for intake of radionuclides in water. The geology of the study area may be a factor responsible for the observed trend. It is recommended that water sources in the region should be treated before consumption.