Assessment of Human Exposures to Natural Sources of Radiation in Soils of the Cretaceous-Paleocene Formation of Sokoto Basin, Sokoto, Northwestern, Nigeria

Abstract

Natural radioactivity is a source of continuous exposure to human beings. It originates from both extraterrestrial sources and radioactive elements in the earth’s crust. The amount of radioactivity in soil varies geographically and ggeologically across the world. In Sokoto city and it’s environs, data on the levels of natural radioactivity in soils is absent. It was therefore considered imperative to measure the activity concentration of ²²⁶Ra, ²³²Th, and ⁴⁰K in soil samples collected from various areas of Sokoto. Activity concentrations were measured by means of Sodium Iodide gamma-ray spectrometry. A total of 12 surface soil samples were collected from around Sokoto city. The measured activity concentrations of these radionuclides were compared with the data reported worldwide. Mean measured activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K were 53.68.28 Bq kg ⁻¹, 115.2928.4 Bq kg ⁻¹, and 2003.1278.1 Bq kg⁻¹, respectively. Mean values of radium equivalent activity, air absorbed gamma radiation dose rate, and external radiation hazard index were 378.71±40.19 Bq kg⁻¹, 1.09±0.06 nGy h⁻¹, and 1.006 Bq kg⁻¹, respectively. The annual effective radiation dose was calculated to be 1.09 mSvy⁻¹. The result of this work has established the fact that soils from Sokoto contain enhanced level of gamma radiation that may be hazardous to the inhabitants of the area.