Abstract
Purpose. To establish pre-mining indicators to assess radiological impact as a result of release of radionuclides to environment during uranium mining at Mkuju River Project radioactivity of 226Ra, 232Th and 40K in soil, plants, fruits and cereals. Methods. The High Purity Germanium detector was used to determine the radioactivity and the data were subsequently used to establish soil to plant transfer factors and annual effective dose. Findings. The results revealed a strong positive correlation (r) of 0.947 and 0.950 for 226Ra and 232Th, respectively, between values determined in soils and plants. Implicit in these finding is that the distribution of radionuclides in soils is directly proportional to the corresponding radionuclides in plants. Originality. The roots of wild grass had the highest specific radioactivity (Bqkg-1) for 226Ra (2.15 ± 0.02), 232Th (1.43 ± 0.02) and 40K (198.16 ± 1.72) and the roots of cabbage had the highest values for 226Ra (1.38 ± 0.04), 232Th (1.34 ± 0.03) and 40K (146.12 ± 1.02) among the food crops, an indication of a higher ability to uptake radionuclides from soil. Similarly, since the TFs were found higher in wild grass for 226Ra (0.0533 ± 0.04), 232Th (0.0374 ± 0.002) and 40K (0.5297 ± 0.05) and cabbage for 226Ra (0.0362 ± 0.03), 232Th (0.0360 ± 0.001) and 40K (0.4173 ± 0.05). Practical implications. It is an evident that these plants can serve as good bio indicators to assess release of radionuclides from inside the mining site to the public domain. Moreover, the annual effective dose (mSvy-1) for 40K (0.23 ± 0.02), 226Ra (0.046±0.004) and 232Th (0.073 ± 0.006) in edible crops when consumed in the vicinity of the MRP before the mining operations were, as expected, insignificant.
Highlights
Release of radioactive materials into the environment as a result of mining activity to a greater extent is responsible for enhanced effective dose to the population either through external gamma irradiation or internal exposure by inhalation and ingestion of radionuclides or both (IAEA, 1994; UNSCEAR, 2000; IAEA, 2008; Bersimbaev & Bulgakova 2015)
The roots of wild grass had the highest specific radioactivity (Bqkg-1) for 226Ra (2.15 ± 0.02), 232Th (1.43 ± 0.02) and 40K (198.16 ± 1.72) and the roots of cabbage had the highest values for 226Ra (1.38 ± 0.04), 232Th (1.34 ± 0.03) and 40K (146.12 ± 1.02) among the food crops, an indication of a higher ability to uptake radionuclides from soil
The radioactivity of 226Ra, 232Th and 40K were determined in species of plants, fruits, cereals and soils collected along with plants in the vicinity and the concession of the proposed Mkuju river project (MRP)
Summary
Release of radioactive materials into the environment as a result of mining activity to a greater extent is responsible for enhanced effective dose to the population either through external gamma irradiation (due to a source outside the body) or internal exposure (due to a source within the body) by inhalation and ingestion of radionuclides or both (IAEA, 1994; UNSCEAR, 2000; IAEA, 2008; Bersimbaev & Bulgakova 2015). Most of the gamma rays responsible for external exposure have average low intensity and their penetration into the body is limited. The occupancy time of external exposure of approximately 20% is lower than occupancy time of 100% for internal exposure when radioactivity is inside the body. The external population exposure due to environmental radioactivity in this study has been neglected. Internal exposure which is more important than external is closely related to the concentration of radionuclides in food crop mainly through roots uptake from soil
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