Levels of Natural and Artificial Radioactivity in Soils, water and tuber crops in the Tano- North District of Brong-Ahofo Region; Ghana

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2014-08-13
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Abstract
The levels of radionuclides in water, soil and tuber crops from the Tano-North District of Ghana have been determined. Gamma ray spectrometry was used to analyze the activity concentrations of 238U, 232Th, 40K and 137Cs in the samples. Also the Gas-less Automatic Alpha/Beta counting system (Canberra iMatic Tm) was used to determine gross alpha and gross beta activity concentrations of the water. The estimated average annual effective dose due to ingestion of radionuclides in water by the public was 40.43 μSv/y, 20.08 μSv/y, 33.58 μSv/y, 53.45 μSv/y and 24.90 μSv/y for Duayaw/Nkwanta, Buokukruwa, Bomaa, Techire and Tanoso respectively. The average values for the annual effective dose from different locations in the district were lower compared with the recommended values of 100 μSv/y and 240 μSv/y by the World Health Organization and the United Nations Scientific Committee on the Effects of Atomic Radiations respectively. The average values for gross alpha and gross beta activities from the Tano-North District were 0.021 Bq/L and 0.094 Bq/L respectively. These average values were well below the guideline values of 0.5 Bq/L and 1.0 Bq/L for gross alpha and gross beta activities in the drinking water as recommended by the WHO. The result shows that, drinking water consumed by the inhabitants of the Tano-North District of Ghana does not pose any significant radiological health risk. The average activity concentrations of 238U, 232Th, 40K and 137Cs in the soil from different farmlands in the study area were 23.19 Bq/kg, 31.10 Bq/kg, 143.78 Bq/kg and 2.88 Bq/kg respectively. Clearly, these averages were lower compared with the world average of 30 Bq/kg, 35 Bq/kg and 400 Bq/kg for 238U, 232Th and 40K respectively. The estimated absorbed dose rate for the farmlands varied between 23.63 nGy/y to 50.51 nGy/y, which is within the worldwide range of 18 to 93 nGy/y. The activity concentrations of 238U, 232Th, 40K and 137Cs in cassava ranges from 0.38 to 6.73 Bq/kg, 1.82 to 10.32 Bq/kg, 17.65 to 41.01 Bq/kg and 0.38 to 1.02 Bq/kg respectively. Additionally, the activity concentration of 238U, 232Th, 40K and 137Cs in yam also ranges from 0.47 to 4.89 Bq/kg, 0.93 to 5.03 Bq/kg, 14.19 to 35.07 Bq/kg and 0.34 to 0.89 Bq/kg respectively. The average concentration factor for 238U, 232Th and 40K in yam were 0.12, 0.11 and 0.17 respectively. Furthermore, the average concentration factor for 238U, 232Th and 40K in cassava were 0.11, 0.12 and 0.2 respectively. Generally, the concentrations of the radionuclides in yam and cassava samples were low and would not result in a significant health effects to the consumers.
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A thesis submitted to the Department of Chemistry, Kwame Nkrumah University of Science Technology, Kumasi, in partial fulfilment of the requirements for the award of Master of Philosophy in Environmental Chemistry,
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