Abstract
Uranium (U) mining activities, which lead to contamination in soils and waters (i.e., leachate from U mill tailings), cause serious environmental problems. However, limited research works have been conducted on U pollution associated with a whole soil-water system. In this study, a total of 110 samples including 96 solid and 14 water samples were collected to investigate the characteristics of U distribution in a natural soil-water system near a U mining tailings pond. Results showed that U concentrations ranged from 0.09 ± 0.02 mg/kg to 2.56 × 104± 23 mg/kg in solid samples, and varied greatly in different locations. For tailings sand samples, the highest U concentration (2.56× 104 ± 23 mg/kg) occurred at the depth of 80 cm underground, whereas, for paddy soil samples, the highest U concentration (5.22 ± 0.04 mg/kg) was found at surface layers. Geo-accumulation index and potential ecological hazard index were calculated to assess the hazard of U in the soils. The calculation results showed that half of the soil sampling sites were moderately polluted. For groundwater samples, U concentrations ranged from 0.55 ± 0.04 mg/L to 3.36 ± 0.02 mg/L with a mean value of 2.36 ± 0.36 mg/L, which was significantly lower than that of percolating waters (ranging from 4.56 ± 0.02 mg/L to 12.05 ± 0.04 mg/L, mean 7.91 ± 0.98 mg/L). The results of this study suggest that the distribution of U concentrations in a soil-water system was closely associated with hydrological cycles and U concentrations decreased with circulation path.
Highlights
Uranium (U) is a strategic source and has been enormously exploited with an increased demand of nuclear power industry
The results of this study suggest that the distribution of U concentrations in a soil-water system was closely associated with hydrological cycles and U
U concentrations ranged from 1.76 × 104 ± 17 mg/kg to 2.56 × 104 ± 23 mg/kg, and showed vertical variation with all highest values at the depth of 80 cm
Summary
Uranium (U) is a strategic source and has been enormously exploited with an increased demand of nuclear power industry. There are three ways to exploit U: surface (open pit), underground and solution mining (e.g., in-situ leaching). Tailings would be generated worldwide during the U mining and ore processing with particular means of open pit and underground [1]. Tailings and waste rocks produced were difficult to be efficiently isolated from the environment They can be a significant source of radionuclides being released in soils and natural waters via weathering, suspension, denudation, percolation and erosion of meteoric water. These processes would further expand pollution and cause a great damage to the ecological environment [4,5,6]
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