KONG Qiumei1,2, FENG Zhigang1,2, Ma Qiang1,2, LIU Xuanzhi1,2, HAN Shili1,2
(1.School of Nuclear Resource Engineering, University of South China, Hengyang 421001, China;
2.Key Discipline Laboratory for National Defense for Biotechnology in Uranium and Hydrometallurgy, University of South China, Hengyang 421001, China)
Abstract: In this paper we took three soil profiles (i.e., S1, S2 and S3), around a uranium mill tailings pond in Hunan Province, China as the research objective, and discussed input mechanisms of exotic uranium in the soils by contrasting their geochemical characteristics with those of the background profiles and uranium mill tailings sands in the study area by using sequential chemical extraction technique. Results show as follows. (1) The uranium mill tailings pond has given rise to the uranium contamination to ambient soils, and the uranium contamination degree in the soils displays a decreasing trend with increasing distance from the contamination source. For example, the profiles S1 and S2 near the source received heavy uranium contamination and their uranium pollution index (Pi) characterized by the single factor index method are 18.98 and 14.76, respectively, and the profile S3 far away from the source is subjected to slight uranium contamination (i.e., Pi=1.35). (2) As the agricultural soils, the input of exotic uranium into them has been through the whole profiles due to the anthropogenic disturbance in the process of cultivation. (3) The input of exotic uranium of soils, especially for that in the heavily uranium-polluted soils near the source, mainly includes two mechanisms, namely, the one is physical interfusion of uranium carried by tailings sands, and the other is the entrance of water-soluble uranium ion carried by seepage fluid from the pond, and the former is the dominant. However, for the exotic uranium of specific adsorption state, which possessed absolute superiority in the amount among various speciations of exotic uranium in the soils, it is mainly contributed from the latter. For uranium carried by tailings sands, its speciations are inherited in the soils, and for uranium carried by seepage fluid, it is mainly specifically adsorbed onto the soil matrices. This study provides a useful scientific reference for effective governance of the uranium mill tailings pond.
Key words: uranium mill tailings pond; soil; exotic uranium; input mechanism; Hunan Province
EARTH AND ENVIRONMENT Vol.45, No.2, Tot No.316, 2017, Page 135-144
