The distribution, fate and environmental indications of uranium, thorium in reservoir water and sediment profile near a uranium milling area, Guangdong Province

During a sampling campaign from 2010 to 2012, the concentrations of Uranium (U) and thorium (Th) in surface waters were extensively investigated; the concentrations of U and Th in water decrease with the distance from the... [ view full abstract ]

During a sampling campaign from 2010 to 2012, the concentrations of Uranium (U) and thorium (Th) in surface waters were extensively investigated; the concentrations of U and Th in water decrease with the distance from the uranium milling site, and reach the local background level when getting to the reservoir as a terminal. In order to study the fate of U and Th, water in different depth and 4 sediment profiles in the reservoir were sampled and analyzed with ICP-OES. The results show that: (1) the concentrations of U and Th in surface water of reservoir are extremely low but U rise significantly in the depth of 5~10 m while Th represents homogeneous distribution with very low concentration in the same depth; it is likely that most of U and Th have transferred to sediments; (2) The total U concentrations in sediment profiles ranged from 114.6 to 916.2 mg/kg with the average of 415.6 mg/kg while Th ranged from 41.9 to 114.5 mg/kg, averaged 80.3 mg/kg; and (3) 30~50% of U and around 33% of Th in reservoir sediment could be leached using 0.50 mol/L hydrochloric acid, indicating the great possibility of potential release from sediment to water. XRD test shows that the main mineral in sediment is associated with illite and kaoline, together, accounting for more than 50% of total, which might dominate the process of mass balance and environmental behaviors of U and Th between water and sediments.