Quantification of radiological hazards associated with natural radionuclides in soil, granite and charnockite rocks at selected fields in Ekiti State, Nigeria

Assessment of activity levels of radionuclides that exist in soil, granite, and charnockite rock samples is very crucial because it exhibits an enhanced elemental concentration of uranium (U) and thorium (Th) contributing higher natural background activity than usual in the environment and it may cause health risk to human health through the external and internal exposure. This study determined the radioactivity levels of ²³⁸U, ²³²Th, and ⁴⁰K radionuclides in soil, granite, and charnockite rock samples collected from selected fields in Ekiti State, Nigeria using Caesium iodide CsI(Tl) scintillation gamma spectrometer. It also evaluated indices of the radiological parameters consisting of radium equivalent activity (Ra_eq), absorbed dose rate (D_R), annual effective dose equivalent (AEDE), internal hazard index (H_in), and excess lifetime cancer risk (ELCR). The calculated average activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K are 30.40 ± 0.71 Bq kg⁻¹, 3.31 ± 0.05 Bq kg⁻¹, and 222.25 ± 14.72 Bq kg⁻¹, respectively, which were lower than their respective world average values. Comparatively, potassium concentrations in these collected samples have a higher value than concentrations of uranium and thorium (⁴⁰K > ²³⁸U > ²³²Th). All the evaluated values of the radiological parameters (except D_R) of the appraised radionuclides were below the global permissible limits. The granite rocks, charnockite rocks, and soils from Ekiti State in Nigeria do not pose any hazardous risk to humans, but continued monitoring is necessary when these materials are used as building materials, which cause long-term radiation exposure.