Diagenetic formation of uranium-silica polymers in lake sediments over 3,300 years

作者：Pierre Lefebvre, A. Gourgiotis, A. Mangeret, P. Sabatier, P. Le Pape, Olivier Diez, P. Louvat, N. Menguy, Pauline Merrot, C. Baya, Mathilde Zebracki, Pascale Blanchart, E. Malet, D. Jézéquel, J. Reyss, J. Bargar, J. Gaillardet, C. Cazala, G. Morin · 发表于：Proceedings of the National Academy of Sciences of the United States of America · 年份：2021 · DOI：10.1073/pnas.2021844118 · 被引用次数：11 · 研究领域：Medicine

Significance Understanding the long-term fate of widespread noncrystalline uranium (U) species is critical to improving our knowledge of U biogeochemistry and U-contaminated environments. We use naturally U-enriched lake sediments that have been deposited for thousands of years as an analogue for the progressive evolution of contaminated environments, in order to uncover if noncrystalline species may evolve into more resistant crystalline phases. We combine multidisciplinary tools including U isotope ratio and speciation techniques to describe a mineralogical transformation where organic-bound U evolves into polymeric and nanocrystalline uranium-silica phases that are still easily remobilized even 3,300 y after their deposition. These findings bring an interpretation that illuminates an active debate on uranium mobility in the environment. The long-term fate of uranium-contaminated sediments, especially downstream former mining areas, is a widespread environmental challenge. Essential for their management is the proper understanding of uranium (U) immobilization mechanisms in reducing environments. In particular, the long-term behavior of noncrystalline U(IV) species and their possible evolution to more stable phases in subsurface conditions is poorly documented, which limits our ability to predict U long-term geochemical reactivity. Here, we report direct evidence for the evolution of U speciation over 3,300 y in naturally highly U-enriched sediments (350–760 µg ⋅ g−1 U) fro...