Radiological risks and spatial distribution of natural radionuclides in riverbed sediments along the Pashur River, Bangladesh

This study investigates the natural radioactivity levels of 238 U, 232 Th, and 40 K, using an HPGe gamma-ray spectrometry detector, along with the related radioactive risks in the riverbed sediments of the Pashur River in southwestern Bangladesh. The research seeks to elucidate possible radioactive threats posed by incorporating these sediments into building products. The range (mean) activity concentrations of 238 U, 232 Th, and 40 K were found to be 24.2–30.1 (28), 24.6–30.1 (27) and 291.5–430 (376) Bq kg −1 , respectively. The average concentrations of these radionuclides are lower than the world averages of 35, 30 and 400 Bq/kg, respectively, except for the four samples (Sed-1 and Sed 5–7), one sample (Sed-3), which exceeded the 40 K and 232 Th safe limits. All calculated radiation hazard indices (gamma representative index, absorbed dose rate, total annual effective dose, excess lifetime cancer risk, and radium equivalent activity) were below the globally recommended threshold levels. Among the radionuclides, 40 K showed the highest frequency and average effective dose rate, followed by 238 U and 232 Th. Principal component analysis (PCA) was used to explore the nexus among the radioactive elements. Statistical analysis revealed that 40 K and 238 U are the key drivers of radiological risks, verified by significant correlations and high principal component loadings. The results indicate that naturally existing radionuclides in the sediment of the Pashur River do not pose a serious radiological risk to people and the riverine environment, which uses them as construction materials. This work may provide a novel research avenue in riverbed monitoring, environmental health, and radiation protection measures.