Mapping of natural gamma radiation (NGR) dose rate distribution in tin mining areas of Jos Plateau, Nigeria

Abstract

An extensive study was conducted to measure the natural gamma radiation (NGR) dose rates for the tin mining areas of Jos Plateau with an objective to establish a reference data record on the levels and distribution of natural background gamma radiation. The measurement was carried out using a portable NaI(Tl) scintillation survey meter. The results obtained, varied significantly for different soil types and for geological features of the study area. NGR dose rates values ranged between 40 nGy h−1 measured on Ferric Luvisols–Ferric Luvisols (S13) soil type, underlain by geological formation G7 (sandstone, clay and shale) and 1265 nGy h−1 recorded on, Haplic Acrisols (S27), underlain by geological formation G8 (Younger granites) with overall mean value of 250 nGy h−1. This is by a factor of four higher than the reported world average value of 59 nGy h−1. Mean indoor and outdoor annual effective dose for the public was estimated to be 1.2 and 0.31 mSv/y, respectively. An isodose map for the distribution and exposure rate due to natural sources radiation for the study area was also plotted using ArcGis software. The data here presented can use to prepare a national radiological map for the country.