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

Abstract

A small part of the palaeo 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.