Concentration and distribution characteristics of gross alpha, 238U, 234U and 226Ra in freshwater of some rivers and artificial lakes in southeast Vietnam
Minh An Dinh, Nhut Tan Tran, Van Thang Nguyen, Xuan Anh Dao Lam, Truc Phuong Huynh, Cong Hao Le
Applied Radiation and Isotopes 225 (2025) 112064
Abstract:
Rivers and artificial lakes are the major sources that supply freshwater to communities, cities, agriculture, and industry. However, this water type is normally polluted by radionuclides, which are from groundwater discharge, surface soil runoff, or Naturally Occurring Radionuclides (NOR) effluents. In this study, gross alpha and alpha-emitting radionuclides (234U, 238U and 226Ra) were analysed in freshwater samples collected in 31 sites in two rivers and four quarry lakes in Southeast Vietnam. The analyses were conducted in two separate parts of water: suspended matter and filtered water. The mean gross alpha, 234U, 238U and 226Ra activities in unfiltered water were 52.9, 8.2, 7.9, and 6.1 mBq L−1, respectively. These values remain within the recommendations of the United States Environmental Protection Agency (USEPA) and World Health Organization (WHO) for the contamination of radionuclides in drinking water. High activities were found in the water of the Sai Gon River due to the impact of pollutants from the densely populated and industrial zones. Ratios of 234U/238U were found to be slightly >1, while ratios of 226Ra/234U and 226Ra/238U were found to be < 1. Radionuclides 234U, 238U and 226Ra contribute significantly to the gross alpha in both rivers and artificial lakes. Strong linear correlations were found between the activities of alpha-emitting radionuclides and gross alpha in quarry lake water (Pearson correlation coefficient p > 0.7). For two types of freshwater, a significant amount of gross alpha, alpha-emitting radionuclides, was found in the suspended solids of water. The suspended matter/water partition coefficients (Ksw) for two types of water were 1.23 × 105, 1.66 × 104, 1.55 × 104, and 9.7 × 103 L kg−1 for gross alpha, 234U, 238U and 226Ra, respectively. Ksw values of the gross alpha and radionuclides for river water are significantly higher than those in quarry lake water.
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