RESUMEN
Groundwater is regularly used for many purposes, such as drinking and agricultural irrigation systems. Still, it contains high levels of radionuclides (e.g., 238U, 232Th, and 226Ra) that are potentially hazardous to humans and the environment. In this study, activity concentrations of uranium isotopes were analyzed in 15 groundwater samples taken from 15 bored wells in Thu Duc district, Ho Chi Minh City, Vietnam. Environmental effects of the irrigation system with groundwater on agricultural soil in the study area were assessed by models. It was found that the activity concentrations of 238U and 234U in groundwater samples were in the ranges of (13.5-268.7) mBq l-1 and (20.2-438.3) mBq l-1, respectively. The ratio 234U/238U values were ranged from 1.12 to 2, with an average value of 1.44. Based on the model prediction, 25 years irrigation with the groundwater can inject 94.8 Bq both uranium isotopes in 1 kg topsoil. For investigated groundwater samples, the proposed removal method using K2FeO4 removed 74.28% and 81.04% for 234U and 238U, respectively.
Asunto(s)
Agua Subterránea , Uranio , Contaminantes Radiactivos del Agua , Ciudades , Humanos , Uranio/análisis , Contaminantes Radiactivos del Agua/análisis , Pozos de AguaRESUMEN
The effects of moisture content, grain size, temperature, major elemental composition, and the pH of soils on the radon emanation and diffusion coefficients were evaluated in this study. The emanation and diffusion coefficients are strongly influenced by moisture content and grain size. The radon emanation coefficient increased and the diffusion coefficient decreased with decreasing particle size. However, for soils with large particle sizes, the radon emanation and diffusion coefficient remain almost unchanged with variation in grain size. Comparing five different sized soil particles, the emanation coefficient increased and the diffusion coefficient decreased with moisture content. The radon emanation coefficient reached a constant value with different moisture contents depending on the range of grain sizes. The saturation emanation coefficient for less than 0.1, 0.1-0.2, 0.2-0.3, 0.3-0.5, and more than 0.5 mm sized soil grain ranges are 0.47, 0.42, 0.35, 0.26 and 0.23, respectively, with saturation moisture contents of 16%, 14%, 10%, 6% and 4%, respectively. A drastic increase in radon emanation is found at smaller grain sizes with increasing moisture content. Based on the content of major elements and pH of the soils, the multiple regression indicates that the radon emanation coefficient appears to be significantly dependent on iron content and pH. Effective diffusion coefficient values calculated in our study agree with the results calculated by a previous model. Experimental values show that the temperature dependence of the radon diffusion coefficient follows Arrhenius behavior.