Geospatial Assessment and Environmental Implications of Natural Radioelement Distribution in Selected Locations in Ondo and Osun States Using Aeroradiometric Technique

Abstract This study presents an airborne radiometric assessment of natural gamma radiation across selected areas in Ondo and Osun States, Nigeria, utilising radiometric datasets from Sheets 263 and 264 obtained from the Nigerian Geological Survey Agency. The data, organised in a gridded format, were analysed using Oasis Montaj software to quantify the concentrations of naturally occurring radioelements, ²³⁸U, ²³²Th, and ⁴⁰K, and to estimate the corresponding terrestrial gamma dose rates. Results indicate that, in Sheet 264, concentrations of ²³⁸U, ²³²Th, and ⁴⁰K range from 3.08–102.31 Bq/kg, 19.10–174.05 Bq/kg, and 91.85–1,563.00 Bq/kg, respectively. For Sheet 263, ²³⁸U concentrations span 0.38–94.72 Bq/kg, ²³²Th from 5.90–162.70 Bq/kg, and ⁴⁰K from 59.50–943.00 Bq/kg. The calculated absorbed dose rates in both sheets exceed the global average of 59 nGy/h, with generally higher values observed in Sheet 264. The elevated levels of primordial radionuclides and associated radiation doses in several locations suggest a potential public health concern due to chronic exposure to ionising radiation. Given the geological context and ongoing anthropogenic activities in the region, routine environmental monitoring is recommended to mitigate potential radiological risks to local populations.