Background gamma radiation mapping in forest ecosystem of Bangladesh: A study on the radioactivity distribution in the national reserve forest of Gazipur

Abstract

Natural and artificial radioactivity appears to be different in different geological regions. Moreover, the radionuclides may migrate to the deeper region of the earth after deposition, and the depth profile of a radionuclide reveals information on the rate of migration. Countrywide background gamma radiation mapping program has been initiated in Bangladesh by dividing the whole country primarily into ~2 km × ~2 km (1' ×1' in Global Positioning System scale) systematic square grids to formulate the radioactivity profile. About 28 km × 30 km area of forest land of Gazipur district called the “BhawalGahr” including the Bhawal National Park was selected for sampling. Soil samples from 0 to 5 cm, 5 to 15, cm and 15 to 30 cm depth were collected from the 27 grid node points of the square grids. A total of 81 samples were collected for the current study. The samples were subjected to elemental and radioactivity analyses. The elements found in the samples were in decreasing order as Fe>K>Ti>Ca>Co>Mn>V>Cr>Ni. The calculated activity concentration of natural radionuclides 226Ra, 232Th, and 40K for surface soil samples (0–5 cm depth) ranged from 44.2 ± 5.7 to 84.5 ± 10.2 Bq/kg, 75.6 ± 8.3 to 126.5 ± 8.3 Bq/kg, and 263.7 ± 92.3 to 606.7 ± 107.9 Bq/kg, respectively and there is no significant variation for other depths. The radiological hazard indices such as radium equivalent activity, radiation external hazard index, absorbed dose rate, and annual effective dose were also estimated from the calculated values of activity concentrations.

Keywords

• Artificial radionuclide
• BhawalGahr
• high purity germanium detector
• natural radionuclide
• proton-induced X-ray emission
• radioactivity