keywords: Exposure, gamma, mapping, radiation, terrestrial, Zamfara
This study measured and mapped terrestrial gamma radiation (TGR) exposure in seven local government areas of Northern Zamfara State, Nigeria. The assessment was carried out using a portable survey meter, Inspector Alert Nuclear Radiation Monitor and a global positioning system (GPS). Due to the random nature of radioactivity, five measurements were taken per each location to minimize the error, with the survey meter held 1 m above the ground. A total number of 166 average measurements were evaluated and recorded. Statistical analyses were carried out on the results using Statistical Package for Science Study (SPSS) version 23. The mean terrestrial gamma radiation exposure rate in the study area was found to be 32 nGy h-1. KauraNamoda local government area has the highest mean value of TGR exposure rate of 38 nGy h-1, while Bakura local government area has the lowest mean value of TGR exposure rate of 28 nGy h-1. Gamma radiation distribution map which shows the distribution of TGR exposure in the study area was plotted using ArcGIS software version 10.3. Exposure and risk; outdoor annual effective dose rate, mean population weighted dose rate, annual collective effective dose, lifetime dose and excess lifetime cancer risk were computed as 0.04 mSv y-1, 32.45 nGy h-1, 59.33 Sv y-1, 2.75 mSv, and 1.38×10-4, respectively.