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Titre : Evaluation of primordial radionuclides and health impacts in soil, groundwater and food crops from the lower Swakop river, Namibia

Auteur : Amakali, Gideon

Université de soutenance : North-West University

Grade : Doctor of Philosophy in Science with Radiation Science 2021

Résumé partiel
Primordial radionuclides ; 238U, 232Th and 40K are found ubiquitously in varying concentrations in environmental media. The exploration and mining related activities have the potential to redistribute and concentrate primordial radionuclides to locations accessible to members of the public. These radionuclides are the significant contributor to the radiation doses received by humankind through various exposure pathways. The Swakop river community and environmental activists expressed concern over possible contamination of alluvial sand used in the construction industry and agricultural croplands in the lower Swakop river due to uranium mining related activities in the surrounding areas. This has motivated for the study to evaluate the primordial radionuclides in groundwater, soil and food crops in the lower Swakop river and possible associated health impacts. The study has also considered the portion of the Khan river that traversing between the uranium mining activities before confluent with the Swakop river. A total of 63 soil samples were subjected to high purity germanium (HPGe) detector gamma spectroscopic technique for the identification and quantification of primordial radionuclides present. Inductive Coupled Plasma Mass Spectrometry (ICP-MS) technique was used for the identification and quantification of total elements of U, Th and K in water and food crops samples. The average activity concentrations of 238U in soil samples across the study area were found to vary from 69.19±4.48 to 532.09±11.90 Bq.kg-1 . The average activity concentrations of 232Th in soil samples varied from 59.07±1.11 to 211.56±1.85 Bq.kg-1 , while for 40K were from 568.73±12.66 to 982.74±24.56 420 Bq.kg-1 . The activity concentrations of 40K and 238U in groundwater along the Swakop river were varied from 737.66 to 2475.98 mBq.l-1 and 0.161 to 1116.47 mBq.l-1 with average values of 1449.22±181.85 and 313.43±127.62 mBq.l-1 , respectively, while 232Th was below the detection limit of the technique used. The average activity concentrations for 238U, 232Th and 40K in the groundwater samples collected from the Khan river were 1282.55±230.04 mBq.l-1 , 0.167±0.09 mBq.l-1 and 1505.02±153.16 mBq.l1 , respectively

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