Natural Radionuclide concentration in Phosphate fertilisers found in Kenyan market
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Date
2023-11
Authors
Mutwiri, Mbaka E
Journal Title
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Publisher
Kenyatta University
Abstract
ABSTRACT
Human exposure to radiations from natural radionuclides is an inevitable aspect of life on earth. Cosmic
sand radioactive materials are the two main sources of ionizing radiation on the earth's surface. Phosphate bearing rock, a material used to manufacture phosphate fertilizers, is known to contain relatively high content of uranium, thorium and potassium radionuclides. Continuous application of these phosphate fertilizers in our agricultural soils lead to contamination of our farming land with these radionuclides. Radiations from these radionuclides pose health risks such as cancer to the exposed individuals. Apart from the radionuclides, phosphate rock also contains traces of heavy metals such as cadmium (Cd) which is considered a big threat to human health. This research has analyzed the activity concentration of 238U, 232Th and 40K in various fertilizer types from three different brands sourced from Kenyan market. NaI(TI) detector and AAS were used for spectrometric analysis. The different types of fertilizers analyzed were; DAP, SSP, TSP, CAN and NPK (17:17:17). The radiological parameters; Radium equivalent, absorbed dose rate, external radiation hazard index, annual effective dose and excess lifetime cancer risk have been evaluated. The mean radium equivalent (Bq/kg) were 133±9 for DAP, 74±8 for CAN, 118±12 for SSP, 128±9 for TSP and 104±9 for NPK. The mean dose rate (nGy/h) were 69±5 for DAP, 37±4 for CAN 58±6 for SSP, 62±5 for TSP and 52±4 for NPK. The mean external radiation hazard index were in the range 0.20±0.03 to 0.36±0.04. The mean outdoor annual effective dose (mSvy1) were in the range 0.045±0.007 to 0.081±0.009. The mean excess life time cancer risk ranged from 0.157±0.010 to 0.283±0.020. DAP had the highest mean values while CAN had the lowest mean values for all the radiological parameters evaluated. The mean concentration of Cd ranged from 1.42±0.20 mg/kg to 11.13±0.48 mg/kg. The obtained results show that fertilizer samples are safe for use as cadmium levels and the radiological parameters assessed are below the maximum permissible limits of 60mg/kg for Cd concentration, 370 Bq/kg for radium equivalent, 60 nGy/h for dose rate,1 mSvy1 for annual effective dose and 0.29 x 10-3 for outdoor ELCR
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Abstract