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Understanding the solid phase chemical fractionation of uranium in soil profile near a hydrometallurgical factory
- Yang, Sheng, Zhang, Xiaowen, Wu, Xiaoyan, Li, Mi, Zhang, Lijiang, Peng, Ying, Huang, Qianwen, Tan, Wenfa
- Chemosphere 2019 v.236 pp. 124392
- B horizons, C horizons, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, adsorption, anthropogenic activities, carbonates, food chain, fractionation, milling, mineral content, mining, organic matter, pH, particle size, polluted soils, scanning electron microscopy, soil pollution, soil profiles, surface area, toxicity, uranium
- Uranium (U) contamination of soil has become a major concern with respect to its toxicity, accumulation in the food chain, and persistence in the environment. Anthropogenic activities like mining and processing of U ores has become pressing issues throughout the world. The aim of the work is to understand the chemical fractionation of U in polluted soil and the mechanism involved. U-free soils samples of eluvial (E), illuvial (B), and parent-material (C) horizons from a hydrometallurgical factory area were used. The experimental results showed that the U adsorption capacity decreased with depth, and its mobility in the upper soil is better than the lower. It was closely related to distribution coefficient (Kd), pH, organic-matter (OM), and carbonate content of soil horizons. The chemical fractionation of U was studied using the BCR sequential extraction scheme for soils after saturated adsorption. It was noted that the U reducible and oxidizable fraction in the E and B horizons can vertically transfer to the C horizon and occurs a significant rearrangement of U in different horizons. BET, SEM, XRD, and FT-IR analyses showed that different U distribution and migration in soil profile is mainly affected by specific surface area, soil particle size, mineral composition, and active groups. The XPS data further indicated that U (VI) is gradually converted to U (IV) with decreased depth and fixed in deeper soil becoming insoluble and immobile. It is the first step to investigate potential migration and plan U mining and milling area long-term management.