Human exposure to Naturally Occurring Radioactive Materials (NORMs) and toxic heavy metals has been a concern for the entire history of mankind since they are com monly found in the environment. Their increased levels are a result of anthropogenic activities such as mining. A-cap Resources Ltd, now A-cap Energy Ltd company dis covered that there were large uranium deposits in the underlying rocks of Serule. It was given licensing to start mining in 2016 with a lease of about 144 km2 . Uranium mining results in large disruptions of surface soils which causes radionuclide and metal contamination thus affecting soil quality and human and environmental health. As a result, this work focused on evaluating NORMs and toxic heavy metal concentrations in the surface soil around Serule prospective mining area as well as their health risk to members of the public. From a depth of about 15 cm, 29 soil samples were ran domly collected using an auger and analysed for natural radionuclides and selected toxic heavy metals using a High-Purity Germanium (HPGe) detector and Inductively Coupled Plasma Mass Spectrometer (ICPMS), respectively. A control sample was also collected and analysed in the same manner. All measurements obtained were compared to the control and reference standards. The HPGe detector with a relative efficiency of 60 % and a 2.0 keV resolution was used to identify and measure activity concentrations of radionuclides found in samples. Average activity concentrations of 226Ra, 238U, 232Th, 40K and 210Pb in areas with high activity of 238U were 1126.26 ± 6.49, 498.21 ± 10.01, 71.39 ± 1.27, 284.18 ± 21.74 and 1490.20 ± 28.77 in Bq/kg, respectively. These activities were higher in comparison to the world average values as reported by UNSCEAR (2000), where average activity concentrations of 226Ra, 238U, 232Th and 40K were 32, 33, 45 and 420 in Bq/kg, respec tively. The world average activity concentration value of 210Pb is still not published. iv The radiological risk to members of the public in the study area was calculated using radiological parameters from UNSCEAR (2000). Areas with high activity of 238U had higher concentrations of radiological parameters in comparison to the world average, areas with low activity of 238U and the control. This showed that areas with high activity of 238U pose a radiological risk to residents. Following an acid digestion of method 3051A, toxic heavy metals were analysed using an Agilent (7500 series) ICP-MS. This was used to determine mass concentrations of these heavy metals. In areas with high activity of 238U, toxic heavy metal concentra tions decreased in the order Cr > Pb > As > Cd > Hg with values 101, 26.4, 9.56, 0.133 and 0.00475 in mg/kg, respectively. These concentrations were compared to the maximum permissible limits of World Health Organisation (WHO) guidelines, where the maximum permissible limits for Cr, Pb, As and Cd were 10, 100, 20 and 3 in mg/kg, respectively. The maximum permissible limit for Hg is not yet published. Cr was the only toxic heavy metal greater than the recommended World Health Organisa tion (WHO) value for areas with high activity of 238U. Using these concentrations, the total non-carcinogenic risk for adults and children was determined and results showed that they both have a close to zero non-carcinogenic risk due to toxic heavy metals in the study area. Toxic heavy metals from all locations of the study area showed a carcinogenic risk that was within the allowable limit of 1 × 10−4 , therefore, the carcinogenic threat to residents due to toxic heavy metals is negligible.

Thesis (Msc Applied Mathematics and Physics)) --Botswana International University of Science and Technology, 2021.