Evaluation of natural radionuclides distribution in beach sands of Cox's bazar sea beach, Bangladesh, using multivariate statistical technique

The distribution of natural series radionuclides Ra-226, Th-232 and non-series K-40 in the heavy mineral-rich beach sands of highly touristic areas of Cox's Bazar sea beach has been studied. The study is made to evaluate the gamma radiation exposure to individuals with an aim to establish reference data for the presence of naturally occurring radionuclides. The present study reports the probable first attempt of detail and systematic work in the study areas for estimation of activity concentration in the recent beach sand samples. Radiometric analysis was performed using gamma ray spectroscopy system based on HPGe detector. The mean activity levels of Ra-226, Th-232 and K-40 in Laboni beach sands were ranged from 255.69 +/- 64.57, 336.83 +/- 93.96 and 1785.91 +/- 89.60 Bq kg(-1), respectively. While in Kolatoli beach sands, the respective values were 166.42 +/- 35.99, 157.35 +/- 35.90 and 1894.42 +/- 74.07Bq kg(-1), respectively. The mean values of Ra-226 and Th-232 concentrations in the investigated beach sands were estimated to be very much higher than the corresponding world average values and comparable to those found in high background radiation areas in the world. The heavy minerals seem to control the activity concentrations of Ra-226 and Th-232 in sand samples, showing some variances based on uranium and thorium bearing minerals. Various radiation health hazard indicators were found to be extremely higher when compared to the recommended values. Hence, heavy mineral-rich sands may pose a significant radiological health risk to the people. The descriptive statistics indicating the radionuclides of Ra-226, Th-232 and K-40 are uniformly and symmetrically distributed in the Cox's bazar beach sand. Multivariate statistical analysis showing the radioactivity and estimated radiological parameters are strongly positively correlated with Ra-226 and Th-232, while weakly correlated with K-40, signifying that radiological risk is mainly associated and controlled by the radioactivity levels of uranium and thorium series radionuclides.