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 ( 238 U,226 Ra,232 Th and 40 K ) in paddy soil. Results show that the content of 238 U peaked at 40 cm in depth of a soil profile at Sampling Site No. 2, and the highest content of 238 U, 226 Ra, 232 Th and 40 K was found in the topsoil at all the other sampling sites. Moreover, within the 0-100 cm soil layer, the con-tents 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, in-dicating that the radioactive contamination in the paddy soil surrounding the uranium tailings dump site is at the hazardous level with NPI reaching 53. 45.%选取南方某铀尾矿库区周边土壤为研究对象,研究稻田土壤中放射性核素( 238 U、226 Ra、232 Th和40 K)的分布特征. 结果表明,2号点位238 U含量在土壤40 cm深处达到最大值,其余各采样点238 U、226 Ra、232 Th和40 K含量均在土壤表层达最高. 土壤0~1m深范围内,随深度增加放射性核素含量呈递减趋势,且在表层土壤下降速率更大.土壤中放射性核素含量分布不均匀可能受人为因素、当地降水量、土壤酸碱度、土壤颗粒粒径以及与铀尾矿库的水平距离等多种因素影响. 采用江西省土壤放射性核素背景值,通过内梅罗指数评价法对铀尾矿周边稻田土壤放射性核素238 U、226 Ra、232 Th和40 K含量进行综合评价,综合污染指数为53. 45,属危险状态.
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