M.I. Chowdhury

DISTRIBUTION OF RADIONUCLIDES IN THE RIVER SEDIMENTS AND COASTAL SOILS OF CHITTAGONG, BANGLADESH AND EVALUATION OF THE RADIATION HAZARD

The concentrations and distribution of natural and anthropogenic radioactive materials in sediments and soils from around the two major rivers and coastal area of Chittagong, Bangladesh were investigated with an aim of evaluating the environmental radioactivity and radiation hazard. In the sediment and soils in general, the concentration of 232Th was found to be higher than that of the 238U and the activities of 232Th and 238U in this area are higher than the world average. 137Cs was observed in all the samples, ranging from 0.4 to 3.88 Bq kg−1. The radium equivalent activities, emanation coefficients and radon exhalation rates were estimated for the sediment and soils; the emanation coefficients, radon exhalation rates and dose rates were found to be higher than the world average values.

Attenuation coefficients of soils and some building materials of Bangladesh in the energy range 276–1332 keV

The linear and mass attenuation coefficients of different types of soil, sand, building materials and heavy beach mineral samples from the Chittagong and Coxs Bazar area of Bangladesh were measured using a high-resolution HPGe detector and the gamma-ray energies 276.1, 302.8, 356.0, 383.8, 661.6 and 1173.2 and 1332.5 keV emitted from point sources of 133Ba, 137Cs and 60Co, respectively. The linear attenuation coefficients show a linear relationship with the corresponding densities of the samples studied. The variations of the mass attenuation coefficient with gamma-ray energy were exponential in nature. The measured mass attenuation coefficient values were compared with measurements made in other countries for similar kinds of materials. The values are in good agreement with each other in most cases.

Concentration of radionuclides in building and ceramic materials of Bangladesh and evaluation of radiation hazard

The concentration of radioactive226Ra,232Th and40K in building and ceramic materials of Bangladesh was investigated by γ-spectrometry with two HPGe detectors. Radium equivalent activities, representative level index values, criterion formula, emanation coefficients and222Rn mass exhalation rates were estimated for the radiation hazard of the natural radioactivity in the materials. The activity concentrations of the natural radionuclides, radium equivalent activities, emanation coefficients and222Rn mass exhalation rates are compared with the corresponding values for building and ceramic materials of different countries. The radium equivalent activities in the samples varied between 30.9 (mosaic stone) and 328.0 Bq·kg−1 (gypsum). The emanation coefficient of the materials ranged from 7.83 (cement) to 33.0% (soil) and the222Rn mass exhalation rate ranged from 2.31 (stone chips) to 118.0 μBq·kg−1·s−1 (gypsum).

Radioactivity in chemical fertilizers used in Bangladesh

Abstract The radioactivity concentrations of 226 Ra, 228 Th and 40 K in different chemical fertilizers, triple superphosphate (TSP), single superphosphate (SSP), diammonium phosphate (DAP), phosphogypsum, muriate of potash (MOP), urea, zinc sulfate and zinc oxysulfate used in the agricultural soil of Bangladesh have been analyzed by gamma spectrometry using a high purity germanium (HPGe) detector. In the fertilizer samples, 226 Ra ranged from 4.8 ± 0.8 to 323.8 ± 24.4 Bq kg −1 , 228 Th ranged from 3.4 ± 1.7 to 22.0 ± 2.8 Bq kg −1 , and 40 K ranged from 7.9 ± 2.4 to 12628.5 ± 169.0 Bq kg −1 . The ratio of radium to thorium was determined, the 226 Ra/ 228 Th ratio ranged from 0.237 to 18.69. This study could be useful as baseline data for radiation exposure to fertilizers, and their impact on human health.

Radionuclide concentrations in mussels collected from the southern coast of Bangladesh.

Abstract Concentrations of 226 Ra , 232 Th , 238 U , 40 K and 137 Cs were determined in whole soft tissues (WST) and shells of groups of different size of marine mussel Perna viridis L. and estuarine mussel Modiolus striatulus H. and water samples which were collected from the southern coast of Bangladesh. Correlation analysis showed that the concentrations of radionuclides vary with mussel size. A positive correlation existed for 238 U and 40 K and a negative one for 232 Th between the radionuclide concentration and mussel size; 232 Th concentrations in WST and shells of the mussels showed an inverse relationship with those of 238 U and 40 K , while 238 U showed positive correlation with 40 K . The concentration factors (CF) for 226 Ra , 232 Th and 238 U in both P. viridis and M. striatulus were higher than those for 40 K . The contents of 137 Cs in both mussels were below the detection limit.

RADIOACTIVITY IN MARINE FISH OF THE BAY OF BENGAL

The concentrations of natural radionuclides of 40K, 232Th and 238U and artificial radionuclides of 137Cs and 134Cs in different marine fish samples from the Bay of Bengal were determined. In some of the fish samples contamination of the 137Cs radionuclide was observed, but 134Cs was below detection level.

Radioactivity of 134Cs, 137Cs and 40K in sea-water on the Bay of Bengal

Abstract The radioactivity of 134 Cs, 137 Cs and 40 K in sea-water samples of the Bay of Bengal off the coast of Bangladesh were measured. The caesium and potassium radionuclides were collected on a ammonium phosphomolybdate precipitate and measured by HPGe γ-spectrometry.

Measurement of physiochemical parameters and determination of the level of radiological threat to the population associated with the Karnaphuli River sediment containing municipal and industrial wastes of Chittagong city in Bangladesh

The research work has been aimed to assess the radiological and chemical threat caused due to urban and industrial wastage drainage to the inhabitants of the Chittagong city in Bangladesh. For finding the chemical effects along with the measurement of radiological threat, the physiochemical characteristics (temperature, pH value and oxidation-reduction potential) of the sediment samples have been analysed. The activity concentrations of naturally occurring radionuclides (238)U, (232)Th, (226)Ra and (40)K in the investigated samples have been found to be higher than those of the world average values. The artificial radionuclide (137)Cs in the samples studied has not been detected. The mean value of the radium equivalent activity and outdoor exposure rate in the study region have been found to be 240.94 ± 23.12 Bq kg(-1) and 115.82 ± 10.81 nGy h(-1), respectively. The radiation doses have been measured directly by employing beta-gamma survey meter (model: LUDLUM 44-9) from where the samples have been collected. The average values of the radiological parameters have been calculated from the activity concentrations of the radionuclides mentioned in the sediment samples found to be higher than those of the corresponding world average values.

Natural and anthropogenic radioactivity levels and the associated radiation hazard in the soil of Oodalia Tea Estate in the hilly region of Fatickchari in Chittagong, Bangladesh

Radioactivity in the soil of a tea garden in the Fatickchari area in Chittagong, Bangladesh, was measured using a high-resolution HPGe detector. The soil samples were collected from depths of up to 20 cm beneath the soil surface. The activity concentrations of naturally occurring 238U and 232Th were observed to be in the range of 27 ± 7 to 53 ± 8 Bq kg−1 and 36 ± 11 to 72 ± 11 Bq kg−1, respectively. The activity concentration of 40K ranged from 201 ± 78 to 672 ± 81 Bq kg−1, and the highest activity of fallout 137Cs observed was 10 ± 1 Bq kg−1. The average activity concentration observed for 238U was 39 ± 8 Bq kg−1, for 232Th was 57 ± 11 Bq kg−1, for 40K was 384 ± 79 Bq kg−1 and for 137Cs was 5 ± 0.5 Bq kg−1. The radiological hazard parameters (representative level index, radium equivalent activity, outdoor and indoor dose rates, outdoor and indoor annual effective dose equivalents, and radiation hazard index) were calculated from the radioactivity in the soil.