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An Analysis for Distribution of Natural Radionuclides in Soil, Sand and Sediment of Potenga Sea Beach Area of Chittagong, Bangladesh

Sabina Yasmin
Department of Physics, Chittagong University of Engineering and Technology, Chittagong, Bangladesh; Atomic Energy Centre, Bangladesh Atomic Energy Commission, Chittagong, Bangladesh

Bijoy Sonker Barua
Atomic Energy Centre, Bangladesh Atomic Energy Commission, Chittagong, Bangladesh

Masud Kamal
Atomic Energy Centre, Bangladesh Atomic Energy Commission, Chittagong, Bangladesh

Md. Abdur Rashid
Department of Physics, Chittagong University of Engineering and Technology, Chittagong, Bangladesh

Abstract/ Executive Summary:

A HPGe (High Purity Germanium) detector based, low background gamma-ray counting system was used for activity measurement in soil, sand and sediment samples collected from Potenga sea beach area of Chittagong, Bangladesh. The specific radioactivities of Radium (²²⁶Ra), Thorium (²³²Th) and Potassium (⁴⁰K) were measured in the above samples. The investigation reflected the lower deposition of minerals exist in the collected samples. From the measured specific radioactivities of the above three natural radionuclides, the radium equivalent activity (Ra_eq), the external hazard index (H_ex), the external gamma absorbed dose rate and the annual effective dose were calculated. The obtained mean values of gamma absorbed dose rate in soil and sand samples and annual effective dose in soil, sand and sediment samples were found higher than the worldwide average as reported by United Nations Scientific Committee on the Effects of Atomic Radiation. The Ra_eq values were in the range of 47.86 to 293.76 Bq.kg⁻¹ and the H_exvaried from 0.13 - 0.81, which indicated that the study area was radiologically safe for human being.

Keywords: Natural Radioactivity, Specific Radioactivity, HPGe ?-Ray Detector, Radiation Hazard Index, Dose Rate, Potenga Sea Beach

Location: Department of Physics, Chittagong University of Engineering and Technology, Chittagong

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Contamination of soil

Objectives:

In the present study the knowledge of specific activities and distributions of ²³⁸U (²²⁶Ra), ²³²Th, ⁴⁰K and ¹³⁷Cs in soil, sand and sediment samples collected from Potenga sea beach area were of interest since it provided useful information for estimation of the radiation exposures of human being and in monitoring of environmental radioactivity at that area.

Methodology:

A number of soil, sand and sediment samples were collected from sea beach area of Potenga, Chittagong. Sediment samples (Sb-L-21 to Sb-L-30) were under the shallow sea water and the sand samples (Sb-L-11 to Sb-L-20) are frequently inundated by sea water. The studied area along the bank of the Bay of Bengal is located in Potenga, Chittagong, Bangladesh. It lies between the longitudes of 91⁰47.245' - 91⁰47.710' and the latitudes of 22⁰14.440' - 22⁰13.950'. At every location the sample was collected from 5 - 10 cm depth. All investigated locations were along a line from north to south and formed three adjacent rows. Each sample was about 101 m apart from the nearest one and kept in a plastic bag and labeled according to the location. All investigated samples were dried under the direct sunlight for several days to evaporate the water. After removing unwanted objects each sample was also oven dried at about 105⁰C to obtain constant weight. The investigated samples finally collected after passing through a 500 μm sieve to ensure the homogeneity of the sample. For the measurement of natural radioactivity, each dried sample was weighed and then taken into individual cylindrical plastic container of 8 cm diameter and 2.8 cm height. The sample in container was simply shaken by hand to allow the powder to settle down homogeneously. The volume of the soil sample amounting to about 131 cm3 was kept equal to the standard γ -ray source material. The containers were sealed tightly and wrapped with thick vinyl tapes around their screw necks to keep air tight. These samples were stored for minimum four weeks before the measurement of radioactivity to allow for the attainment of secular equilibrium between²²⁶Ra and²³²Th and their progeny.

Source of Information: Journal of Environmental Protection, 2014, 5, 1553-1563

Article Link (Online Journal): http://www.scirp.org/journal/jep; http://dx.doi.org/10.4236/jep.2014.517147

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The distribution of natural radionuclides in soil, sand and sediment samples collected from Potenga sea beach area of Chittagong, Bangladesh was analyzed by HPGe γ-ray spectrometry. Among the investigated samples, soil has the higher mean specific radioactivities of ²²⁶Ra, ²³²Th and ⁴⁰K and Ra_eq values as well as dose rate and most probably due to manipulation of tourism. The study also indicates that the analyzed soil, sand and sediment samples have lower deposition of minerals. No peak at 661 keV from the decay of ¹³⁷Cs activity was found in the spectrum. However, the results of radiation hazard indices reflected that the investigated area of Potenga sea beach seems to be radiologically safe for human being.

Knowledge Management: Journal