Abstract
A study on the detection of probable radionuclides and their activity concentrations in the raw material (phosphate rock), final product (fertilizer) and waste samples collected from all the phosphate fertilizer factories (total two factories—A Diammonium Phosphate, DAP and a Triple Super Phosphate, TSP factory) in Bangladesh were carried out. A total of seven types of samples (grossly divided into solid and liquid types); liquid waste, waste-mixed river water, normal river water, phosphate rock, phosphate fertilizer, solid waste and normal soil; were analyzed under this study. Raw material samples were collected only from the TSP fertilizer factory. Fertilizer, solid and liquid waste samples were collected from both the factories under study. Moreover, normal soil and natural surface water samples from the suitable areas adjacent to the factories were also collected for the comparison purpose. The samples were analyzed by gamma ray spectrometry technique using a Hyper-Pure Germanium (HPGe) detector of 40% relative efficiency. The analysis of the samples showed that only natural radionuclides such as 226Ra, 232Th and 40K were present in the samples and no traces of artificial radioactivity were found in any of the samples. 40K was found below the detection limit in some samples. The analysis of the samples in the case of TSP fertilizer factory showed that the average activity concentrations of 226Ra and 232Th and 40K in raw materials were 851.27 ± 7.10, 19.63 ± 6.57 and 54.06 ± 5.93 Bq/kg, respectively, in final product 211.90 ± 4.74, 42.48 ± 10.56 Bq/kg and ND (Not Detected), respectively, in solid waste 187.49 ± 4.88, 70.06 ± 11.76 and 289.27 ± 40.24 Bq/kg, respectively and in liquid waste 6.26 ± 0.63, 10.01 ± 1.39 Bq/L and ND, respectively. The measured results in the case of samples collected from DAP fertilizer factory showed that the average activity concentrations of 226Ra and 232Th and 40K in the final product were 17.31 ± 3.92, 69.74 ± 9.88 and 48.46 ± 17.22 Bq/kg, respectively, in solid waste 24.47 ± 4.15, 164.62 ± 11.08, 191.52 ± 33.74 Bq/kg, respectively and in liquid waste 3.59 ± 1.05, 37.08 ± 3.30 Bq/L and ND, respectively. Considering the stored raw materials and wastes the part of the ambient environment of the factory, radium equivalent activity, radiation hazard index and external annual effective dose to the workers and public due to these materials were also calculated and compared with world average values.
Highlights
Numerous types of human practices and non-nuclear industries contribute to further concentrate some of the natural radionuclides that can be found in the earth’s crust affecting the human and the environment
Natural radioactivity in phosphate fertilizer plants is principally due to raw materials, dehydrated calcium sulphate generated as by-product during production of phosphate fertilizer [2], the liquid wastes from the production process and the final product
The concentrations of 232Th in liquid waste and waste-mixed water samples collected from diammonium phosphate (DAP) factory is higher than those of 226Ra which agrees with the above report, the values of 226Ra and 232Th detected in the liquid waste and waste-mixed water samples collected from triple superphosphate (TSP) factory are lower than those of DAP factory, except 226Ra in liquid waste sample
Summary
Numerous types of human practices and non-nuclear industries contribute to further concentrate some of the natural radionuclides that can be found in the earth’s crust affecting the human and the environment. The analyses of radionuclide concentration levels in the starting material, final product and byproduct would provide us with interesting information to evaluate the extension, degree and routes of the radioactive impact, as well as the knowledge of the different pathways followed for the radioactive contamination to disturb the natural system. Taking this into account, the main objective of the proposed study is to determine the content of radioactivity in raw materials, final products and wastes generated from the phosphate fertilizer factories in Bangladesh and to estimate the radiological impact due to the use of the products and release of the wastes in the environment
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