Statistical variability of radiation exposures from Precambrian basement rocks, NW Nigeria: Implication on radiogenic heat production

Radiogeochemistry, mineralogy, lithology, radiogenic heat production, and health implication using airborne radiometric data of Ilesha and its surroundings

The current study analyzed and interpreted airborne radiometric data from Ilesha's basement complex rock and its surroundings. At the surface, the concentrations of the most frequent primordial radionuclides notably K, elemental concentration of uranium eU, and elemental concentration of thorium eTh were measured. The weighted mean elemental and activity concentrations were 0.85%, 2.75 ppm, 10.22 ppm, and 267.54 Bq kg^-1, 34.41 Bq kg^-1, 41.51 Bq kg^-1 for ⁴⁰ K, ²³⁸U, and ²³²Th, respectively. The low concentration of ⁴⁰ K was certainly due to the effects of weathering, kaolinization of granites, and pedogenesis activities. The abundance of uranium was ascribed to the availability of uranium minerals such as allanite, apatite, and sphene with accessories minerals, while that of thorium was due to minerals such as cheralite, thorite, uranothorite, thorianite, and uranothorianite with accessories minerals. The RPHR weighted mean 1.48 µWm^-3 compared to the earth's crust mean between 0.8 and1.2 µWm^-3 was higher due to significant presence of gneiss rocks in all the studied profiles. Radiological hazard, in particular, dose rates, external hazard index, internal hazard index, radium equivalent, annual gonadal dose, effective dose dispensed to various organs of the body were computed to determine the deleterious effects of rocks in the area. The weighted means of annual gonadal dose of 363.98 µSv y^-1 and outdoor 0.91 × 10^×3 and indoor 1.65 × 10^-3 excessive life cancer risks were more than the global average 300 µSv y^-1, 0.29 × 10^-3 and 1.16 × 10^-3. As a result, proper surveillance is required in the area in order to prevent epidemics occurrence in future.