Occurrence and Distribution of Uranium in a Hydrological Cycle around a Uranium Mill Tailings Pond, Southern China

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.

Contaminación Del Agua Y Suelo Por Los Relaves Mineros

“…El legado de la minería, ha dejado importante información sobre la reutilización de los minerales, la administración y la recuperación de los suelos, la contaminación de las aguas superficiales y subterráneas, dando usos alternativos a los relaves mineros (Mubiarto et al, 2020). Se han hecho uso de prácticas de amalgamación, en las minas de Au de la localidad, contribuyendo a la degradación del medio ambiente debido a los relaves que contienen Hg, el cual se almacena en los sedimentos, el agua y en la cadena alimenticia, en detrimento de la salud humana (Ma et al, 2020).…”

Enhancement of Uranium Recycling from Tailings Caused by the Microwave Irradiation-Induced Composite Oxidation of the Fe–Mn Binary System

“…The utilization of uranium has been closely linked to human society since the industrial age, such as to fuel nuclear power plants in the civilian sector and to make high-density penetrators in the military counterpart. − U is normally extracted from the U-bearing ores by grinding and leaching (e.g., biotic and abiotic) techniques in combination after the mining activities. − U tailings are produced after U-related minerals and separated from raw ore sands via leaching. − The U tailings are commonly stored or stacked in huge impoundments, which retains up to 85% of the radioactivity of original U ores emitting to surroundings due to the residual existences of some contained radioactive nuclides such as uranium-238 ( 238 U), uranium-235 ( 235 U), thorium-230 ( 230 Th), and radium-226 ( 226 Ra). − In China, most of the U tailings are stored in the open air at present. Although the environmental hazards posed by the U tailings have attracted more attention, the old reservoir way is still maintained in some stockpiling regions due to the blurred responsibilities and the shortage of funds. − Therefore, the radionuclides and some coexisting heavy metals (HMs) contained in the tailings can be potentially migrated into groundwater from the surface by heavy rains and carried great distances by strong winds, finally entering the biological terminals through the food chain and threatening the ecosystem operations. − The residents can be exposed to uranium and its radioactive daughters by ingesting contaminated food and water and even by inhaling sand dust in the air. Furthermore, long-time uranium exposure will cause severe damage to the normal functioning of some organs (e.g., heart, liver, and kidney) and the nervous system. − …”

Chelating Agents in Assisting Phytoremediation of Uranium-Contaminated Soils: A Review

“…U tailings are the main source of U in contaminated soils. For example, U contamination in the soil and groundwater within the catchment of a U mill tailings pond can be caused by the hydrological cycle around the tailings pond [10].…”