Gamma radioactivity levels and their corresponding external exposure of soil samples from tantalite mining areas in Oke-Ogun, South-Western Nigeria

¹ Department of Physical Sciences, Bells University of Technology, Ota Nigeria
² Department of Physics, University of Ibadan, Nigeria

Received: 9 September 2011
Accepted: 16 January 2012

Abstract

The radioactivity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K were measured using gamma-ray spectroscopy with NaI (Tl) detectors in four tantalite mining sites in the Oke-Ogun area, South-Western Nigeria. The measured values of the activities of ⁴⁰K, ²²⁶Ra and ²³²Th in the soil samples were found to lie in the ranges 123.7 ± 3.8 – 1372.3 ± 8.6, 16.8 ± 1.6 – 71.1 ± 2.53 and 3.0 ± 0.7 – 31.9 ± 1.0 Bq kg–1, respectively. These samples were also found to have radium equivalent activity in the range 74.2–121.0 Bq kg-1. Values of 0.2–0.3 for the external and 0.3–0.4 for the internal hazard indices were estimated for the samples and the annual effective dose varied from 70.3 ± 13.5 to 100.8 ± 42.8 µSv with a mean of 87.5 ± 18.6 µSv y^–1. The annual effective dose is higher than the world average.