Diagenetic formation of uranium-silica polymers in lake sediments over 3,300 years
Pierre Lefebvre, Alkiviadis Gourgiotis, Arnaud Mangeret, Pierre Sabatier, Pierre Le Pape, Olivier Diez, Pascale Louvat, Nicolas Menguy, Pauline Merrot, Camille Baya, Mathilde Zebracki, Pascale Blanchart, Emmanuel Malet, Didier Jézéquel, Jean-Louis Reyss, John Bargar, Jérôme Gaillardet, Charlotte Cazala, Guillaume Morin
Abstract
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.