STUDY OF RADIOACTIVITY IN CHEMICAL AND ORGANIC FERTILISERS USED IN CHATTOGRAM AREA, BANGLADESH.

Abstract

The present work deals with identifying and determining the activity levels of naturally occurring radionuclides 226Ra and 232Th series, their decay products and 40K in chemical and organic fertilisers used in Chattogram area, Bangladesh. A total of 39 samples collected from retail markets were investigated, out of which 28 are chemical fertilisers and the others are organic fertilisers. Gamma-ray spectrometry was applied as the measurement technique using a High Purity Germanium (HPGe) gamma-ray detector at the Atomic Energy Centre, Chattogram, Bangladesh. The average activity concentration of 226Ra and 232Th found in TSP fertiliser are 304.57 ± 36.0 Bqkg−1 and 19.1 ± 6.8 Bqkg−1 respectively and the average activity concentration of 40K in MOP fertiliser is found as 10,311.11 ± 1168 Bqkg−1. In the organic fertiliser samples, the mean concentration of 226Ra, 232Th and 40K are 17.35 ± 3.11 Bq kg−1, 7.20 ± 1.74 Bqkg−1 and 437.14 ± 42.58 Bqkg−1, respectively. The mean absorbed dose rates were measured after the end of our experiment and the value was found to be 91.39 nGyh−1. The combined (indoor + outdoor) annual effective dose equivalent was also estimated as 0.322 mSvyr−1. The mean radium equivalent activity found to be 190.15 ± 26.74 Bqkg−1 is well below the recommended level of 370 Bqkg−1. The internal hazard index, external hazard index and radioactivity level index of the investigated fertiliser samples were found as 0.56 ± 0.034, 0.54 ± 0.08 and 0.69 ± 0.10, respectively. From the calculated hazard parameters, the excess lifetime cancer risk (ELCR) was found to be higher than the world average in most of the chemical fertilisers except in DAP and BOR, while the organic fertilisers show lower than the world average. The obtained results reveal that there are no significant radiation hazards due to natural radionuclides of the fertiliser samples in the studied area, but the higher concentration of 40K in MOP suggests strengthening the regulatory work. Overall, this study highly recommends the use of organic fertilisers, as these kinds have hazard parameters lower than the recommended levels.