Radioactivity Levels, Spatial Distribution, and Radiological Risk Assessment of 226Ra, 228Ra, 40K, and 3H in Water Samples from Dhaka City and Savar, Bangladesh

This investigation was conducted to measure the radioactivity levels of Ra-226, Ra-228, K-40, and H-3 in the 13 most popular branded bottled mineral water (BMW), 12 groundwater sources consumed in Dhaka city, Bangladesh, and six water samples collected from the nuclear object site at Savar, adjacent to Dhaka. The activity of H-3 was measured by using a liquid scintillation counter, and a gamma-ray spectrometer with an HPGe detector was used to measure the activity of other radionuclides. The average activity concentrations of Ra-226, Ra-228, K-40, and H-3 in BMW samples and groundwater were found to be 1.81 +/- 0.43, 1.74 +/- 0.40, 43.08 +/- 6.23, 2.42 +/- 0.16, and 1.61 +/- 0.51, 1.69 +/- 0.45, 57.42 +/- 3.16, and 3.02 +/- 0.19 Bq/L, respectively. In addition, the activity concentrations of identified radionuclides in water samples collected from Savar were found to be 1.59 +/- 0.43, 1.53 +/- 0.50, 99.83 +/- 3.05, and 2.95 +/- 0.20 Bq/L. With the exception of H-3, the activity concentration and the annual effective dose of K-40, Ra-226, and Ra-228 surpassed the acceptable thresholds of the WHO. The combined activity of radium (Ra-c) also exceeds the USEPA recommended maximum permissible limit of 0.185 Bq/L. The excess lifetime cancer risk results were below the permissible threshold of 10(-3) for radiological risks. Groundwater was subjected to an AAS analysis for common metals (Na, Mg, and Ca) and heavy metals (Fe, Cr, Cu, and Pb). The results showed that the heavy metals were below the detection limit. Radionuclide contents in groundwater of Dhaka city were mapped spatially using a GIS technique. Statistical analyses such as one-way ANOVA, one sample t test, and Pearson's correlation analysis were also performed. According to Pearson's correlation analysis, Ra-228 is mostly responsible for radiation risk in BMW and groundwater.