关键词: 铀尾矿库, 稻田, 放射性核素, 比活度

Abstract:

Uranium mining and beneficiation produces large amounts of tailings, which have become the main sources of radioactive contamination in the soil surrounding the tailings dump sites, directly or indirectly affecting human health. An investigation was performed of the soils around a uranium tailings dump site of a uranium mining field in South China, to explore distribution characteristics of radionuclides ( ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K ) in paddy soil. Results show that the content of ²³⁸U peaked at 40 cm in depth of a soil profile at Sampling Site No. 2, and the highest content of ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K was found in the topsoil at all the other sampling sites. Moreover, within the 0-100 cm soil layer, the contents of radionuclides declined with soil depth gradually and the declining trend was the most obvious in the topsoil layer. The uneven distribution of radionuclides in the soil might be attributed to a variety of factors, such as human disturbance, local precipitation, soil pH, soil particle size, and horizontal distance from the dump site. Comprehensive evaluation of the radionuclides ( ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K) in the paddy soil around the dump site was performed using the method of Nemerow′s pollution index (NPI) as against the background values of the radionuclides in the soil of Jiangxi Province, indicating that the radioactive contamination in the paddy soil surrounding the uranium tailings dump site is at the hazardous level with NPI reaching 53.45.

Key words: uranium tailings, paddy field, radionuclides, specific activit