Treatment for removing radium in soil and groundwater.

The results of 226Ra activity concentration measurements in 50 soil and groundwater samples in Ninh Son region, Vietnam were evaluated in the present study. Average activity concentration in the soils was significantly higher than the worldwide average concentration in soils published by UNSCEAR, 2008. 90% of groundwater samples had concentrations of 226Ra that were higher than the USEPA drinking water standard. The results showed that there was a linear correlation between the 226Ra radioactivity in the soils and the concentration of 226Ra in the groundwater samples. The procedure for removal of 226Ra from soil and groundwater samples was built upon the chemistry behavior of radium. 226Ra in contaminated groundwater samples was removed by using MnO2 fiber. The removal efficiency of 226Ra reached ∼ 91% for the groundwater samples and ∼ 70% for the soil samples. Chemical removal of 226Ra from soils was investigated using a three-step extraction procedure (Easily leachable and exchangeable, Acid-reducible, and Oxidisable-organic). A moderate mobility of 226Ra (22-52%) was noted and mainly found in acid-reducible fractions, which suggests that 226Ra is mainly bound to Fe/Mn oxides and hydroxides. A multiple regression indicates that the 226Ra removal efficiency appears to be significantly dependent on Fe/Mn and organic matter content.

Soil radon gas in some soil types in the rainy season in Ho Chi Minh City, Vietnam.

Field experiments on soil radon and radium concentrations were carried out in eighteen locations in Ho Chi Minh City, Vietnam. Soil radon depth profiles (10-100 cm) of loam, sand and clay soil samples in the rainy season were measured using RAD7 radon detector. Mean concentrations of 222Rn and 226Ra were found to be 28.6 ±â€¯2.0 Bq.kg-1 and (1.56 ±â€¯0.06) × 104 Bq.m-3 in clay soil while they are 31.2 ±â€¯2.5 Bq.kg-1 and (1.15 ±â€¯0.05) × 104 Bq.m-3 in loam soil. They are 30.7 ±â€¯2.0 Bq.kg-1 and (9.37 ±â€¯0.52) × 103 Bq.m-3 in sandy soil, respectively. Values of radon diffusion length and diffusion coefficient for different soils were obtained using semi-empirical fit method linked to the poor diffusion of gas in clay soil (0.2 × 10-6 m2 s-1), the moderate diffusion coefficient (0.9 × 10-6 m2 s-1) in loam and good diffusion of radon gas in sandy soil (1.4 × 10-6 m2 s-1). An unexpectedly unclear linear relation was found between soil radon concentration and radium content. The grain size smaller than 0.1 mm was dominant reason for the lowest (0.15 ±â€¯0.01) and highest (0.40 ±â€¯0.03) values emanation coefficient for sand and clay soil, respectively. A strong positive correlation was found between radon concentration and soil pH level leads to soil pH is an indirect dynamic parameter affecting the migration of radon in soil.