The isotopic signature of U^V during bacterial reduction

verfasst von

A. R. Brown, M. Molinas, Y. Roebbert, R. Faizova, T. Vitova, A. Sato, M. Hada, M. Abe, M. Mazzanti, S. Weyer, R. Bernier-Latmani

Abstract

The two step electron transfer during bacterial reduction of U^VI to U^IV is typically accompanied by mass-independent fractionation of the ²³⁸U and ²³⁵U isotopes, whereby the heavy isotope accumulates in the reduced product. However, the role of the U^V intermediate in the fractionation mechanism is unresolved due to the challenges associated with its chemical stability. Here, we employed the U^V stabilising ligand, dpaea^2-, to trap aqueous U^V during U^VI reduction by Shewanella oneidensis. Whilst the first reduction step from U^VI to U^V displayed negligible fractionation, reduction of U^V to U^IV revealed mass-dependent isotope fractionation (preferential reduction of the ²³⁵U), contrary to most previous observations. This surprising behaviour highlights the control that the U-coordinating ligand exerts over the balance between reactant U supply, electron transfer rate, and U^IV product sequestration, suggesting that U^V speciation should be considered when using U isotope ratios to reconstruct environmental redox conditions.

Organisationseinheit(en)

Institut für Mineralogie
AG Geochemie

Externe Organisation(en)

Eidgenössische Technische Hochschule Lausanne (ETHL)
Karlsruher Institut für Technologie (KIT)
Tokyo Metropolitan University
Hiroshima University

Typ

Artikel

Journal

Geochemical Perspectives Letters

Band

29

Seiten

45-50

Anzahl der Seiten

6

ISSN

2410-339X

Publikationsdatum

09.04.2024

Publikationsstatus

Veröffentlicht

Peer-reviewed

Ja

ASJC Scopus Sachgebiete

Umweltchemie, Geologie, Geochemie und Petrologie

Elektronische Version(en)

https://doi.org/10.7185/geochemlet.2411 (Zugang: Offen)