Spatial distribution of natural radionuclides in soils near the Siddirganj combined cycle power plant, Bangladesh

This study assesses the spatial distribution of naturally occurring radionuclides in soils surrounding the Siddirganj Combined Cycle Power Plant, Narayanganj, Bangladesh. Thirty soil samples were collected at radial distances of 100, 250, 500, 1000, and 1500 m from the facility and analyzed using high-purity germanium (HPGe) gamma-ray spectrometry to determine the activity concentrations of 226Ra,232Th, and 40K. The mean activity concentrations were 17 ± 1, 31 ± 3, and 329 ± 27 Bq/kg, with observed ranges of 14–20, 21–41, and 260–400 Bq/kg, respectively. In general, the measured activities were below the worldwide average values of 30, 35, and 400 Bq/kg reported by the United Nations Scientific Committee on the Effects of Atomic Radiation. Some spatial variability was observed among sampling distances; however, no systematic increase in radionuclide concentration was detected with proximity to the power plant, indicating that the distribution is primarily controlled by natural soil characteristics. Correspondingly, the calculated radiological hazard parameters, including absorbed dose rate and annual effective dose, remained within internationally accepted reference levels. These results suggest that the soils in the study area do not pose significant radiological risk under current environmental conditions and are suitable for typical land-use activities such as agriculture and construction. Nevertheless, periodic monitoring is recommended to support long-term environmental assessment.