Geochemical Examination of Surficial Soil Overlying Uranium Deposit in Manyoni, Central Tanzania

Ngulimi, Miguta Faustine; Ishiga, Hiroaki

doi:10.5539/esr.v5n2p121

Cited by 2 publications

(1 citation statement)

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“…The concentration did not significantly differ for Kakonko (8.80 ± 0.45), Bukombe (8.26 ± 0.49), Urambo farm (8.21 ± 0.65), Biharamulo (8.14 ± 0.37), and Kahama (7.83 ± 0.86). The presence of surficial and sedimentary uranium mineralization in Manyoni and Namtumbo (Banzi et al 2015 ; Ngulimi and Ishiga 2016 ), respectively, may have influenced the higher 238 U concentrations in the soils which can then increase uptake by tobacco leaves. The concentrations of 238 U in tobacco leaves from the Bukombe and Biharamulo sampling sites were not detected (below the detection limit).…”

Section: Resultsmentioning

confidence: 99%

Influence of phosphate fertilizers on the radioactivity of agricultural soils and tobacco plants in Kenya, Tanzania, and Uganda

Mwalongo

Haneklaus

Carvalho

et al. 2023

Environ Sci Pollut Res

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Three brands of NPK fertilizers that contain variable concentrations of natural radioactivity are commonly used in tobacco plantations in Kenya, Tanzania, and Uganda. Tobacco plants are known for hyper-accumulation of natural radionuclides, particularly 238U. This study investigated if the elevated radioactivity in phosphate fertilizers could enhance radioactivity in soils and tobacco plant leaves. The 232Th, 238U, and 40K radionuclide levels in NPK-fertilized soils and tobacco leaves were measured using gamma-ray spectroscopy. The research included a one-year reference experiment with tobacco growing in plots, a ten-year semi-controlled experiment in well-managed tobacco farms, and a field survey of radioactivity in soils and tobacco leaves at three traditional tobacco fields in Migori (Kenya), Urambo (Tanzania), and Kanungu (Uganda). The findings demonstrated that soils and tobacco leaves exposed to NPK fertilizers with increased radioactivity had activity concentrations of 232Th, 238U, and 40K that were considerably higher (at all sites) than in the control samples (with no use of NPK fertilizers). As the continued application of NPK fertilizers raises concentrations of 232Th, 238U, and 40K in agricultural soils, the study assessed radiological risks for humans from exposure to agricultural soils enriched with phosphate fertilizers, and it was found to be below the exposure limit of 1 mSvy-1 suggested by the International Commission on Radiological Protection (ICRP). However, tobacco consumers, both by snuffing and smoking, may face significant radiological risks, as the snuffing and smoking resulted in effective doses that were 2.41 to 6.53 and 1.14 to 2.45 times greater than the average yearly dose that the general public receives from inhalation of natural radionuclides (United Nations Scientific Committee on Atomic Radiations estimates). Furthermore, the results indicate that the lifetime excess cancer risk for tobacco snuffers and smokers ranged from 5 × 10-5 to 24.48 × 10-3 and 2.0 × 10-5 to 9.18 × 10-3, respectively. The influence of phosphorus-derived fertilizer containing relatively high natural radioactivity, potential human radiation exposure, and radiological risk due to gamma radionuclides is estimated and discussed. The results reveal that applying phosphate fertilizers enhances natural radioactivity in soil and is subsequently influenced by soil to tobacco plant uptake. Therefore, the study recommends that countries use fertilizers with lower radionuclide content to conserve soil quality and reduce gamma-emitting radionuclides in tobacco plants.

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Section: Resultsmentioning

confidence: 99%