Radioactivity level in soil of a paleo-beach in the south-eastern part of Bangladesh and evaluation of radiation hazard

A small part of the paleo-beach formation extending along the south-eastern fringe of Bangladesh was selected as study area. The sandy beach formation, enriched with heavy mineral sands containing 232Th-bearing monazite, is covered by a thin layer of top soil. Activity concentrations of natural and artificial radionuclides (238U, 226Ra, 232Th, 40K and 137Cs), outdoor and indoor annual effective dose rates and the radiation hazard indices were determined in the soil. The radionuclides, investigated by direct gamma-ray spectrometry using HPGe detector, showed that mean activity concentrations of 226Ra, 238U, 232Th, 40K and 137Cs in soils were 254.53±6.66, 193.95±7.23, 362.18±6.45, 135.79±24.63 and 2.21±0.49 Bq kg-1 respectively. The mean value of radium equivalent activity, external and internal hazards, outdoor absorbed dose rate and total annual effective dose rate were 783.24 Bq Kg-1, 2.12 and 2.80, 354.32 nGyh-1 and 2.52 mSv y-1, respectively, which exceed the average worldwide limit and may pose a radiological threat to inhabitants. (authors)