Modeling of ecological radiation exposure to naturally occurring radioactive materials in Bahi district, Tanzania

This study presents modelling of dose rates using RESRAD BIOTA family code (version 1.8) for natural radioactivity level in the terrestrial environment, Bahi District, Tanzania. The previously reported radioactivity concentrations of ²³⁸ U, ²²⁶ Ra, ²³² Th and ⁴⁰ K in soil have been used to model the non-human biota dose rates. Weighted means and statistical justifications were employed. Statistical rationalization for using weighted mean activity concentrations of the secondary data, radionuclides revealed homogeneity of the sampled locations with ²³² Th and ⁴⁰ K (p < 0.05 at 95% Cl), as major contributors to the total dose rates. The PCA output shows there is a high positive correlation between ²²⁶ Ra and ²³² Th and a slightly weak correlation with ⁴⁰ K. Total dose rates for radiation exposure due to the selected radionuclides were approximately 8.9 µGy h ^–1 and 8.5 µGy h ^–1 for the reference animal and plant, respectively. The RESRAD BIOTA–Level 3 engaged 10 modeled animal species, representatives for the study area of which the overall observation for total dose of radiation exposure was 7.53 µGy h ^–1 for large mammals and 5.8 µGy h ^–1 for other small animals. Generally, all organisms estimated to be exposed to less than 25% and 42% when compared to 10 µGy h ^{– 1} reference level for wildlife for both large mammals and other small animals, respectively. The obtained results suggest no significant radiation exposure or indicating minimal radiological risk under current environmental conditions. However, continuous monitoring is recommended for sites with elevated radioactivity concentrations before any major prospective land exploitations.