Spatial distribution of natural radionuclides and its radiological impact in a fractured sedimentary zone, Nupe basin north-central Nigeria

Abstract

High-resolution aero-radiometric data were analysed over a fractured sedimentary zone to determine the concentrations of natural radionuclides ( 238 U, 232 Th, and 40 K), and to evaluate radiological hazard indices. This was done to assess the potential levels of risk associated with exposure to these radionuclides. The data, covering selected parts of the Nupe Basin, were obtained from the Nigeria Geological Survey Agency (NGSA) and analysed using Oasis Montaj software. Results showed that the activity concentration of uranium, thorium, and potassium in all the locations ranges from 3.7 ± 0.14 Bq/Kg to 1323.5 ± 3.00 Bq/Kg, and the average value of uranium, thorium and potassium are 35.3 ± 0.07 Bq/Kg, 48.88 ± 0.15 Bq/Kg, and 179.9 ± 0.21 Bq/Kg respectively. In addition, analyses of the radiological hazard indices showed that the average value of the absorbed dose rate, annual effective dose, and excess lifetime cancer risk are 53.38 ± 0.18 nGy/h, 0.065 ± 0.02 mSv/y, and 1.85E-4 ± 0.2E-4 as against the recommended values of 84 nGy/h, 1mSv/y, and 3.75E-3 respectively. However, a comparison of the radiological hazard indices with the recommended permissible limits shows that the average values remain within acceptable safety thresholds. It can therefore be concluded that the calculated Excess Lifetime Cancer Risk suggests a low probability of cancer development among residents in most parts of the study area. As a result, the area can be considered radiologically safe.