Deep anoxic aquifers could act as sinks for uranium through microbial-assisted mineral trapping

Pidchenko, Ivan N.; Christensen, John N.; Kutzschbach, Martin; Ignatyev, Konstantin; Puigdomenech, Ignasi; Tullborg, Eva-Lena; Roberts, Nick M.W.; Rasbury, E. Troy; Northrup, Paul; Tappero, Ryan; Kvashnina, Kristina O.; Schäfer, Thorsten; Suzuki, Yohey; Drake, Henrik. 2023 Deep anoxic aquifers could act as sinks for uranium through microbial-assisted mineral trapping. Communications Earth & Environment, 4 (1).

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Uptake of uranium (U) by secondary minerals, such as carbonates and iron (Fe)-sulfides, that occur ubiquitously on Earth, may be substantial in deep anoxic environments compared to surficial settings due to different environment-specific conditions. Yet, knowledge of U reductive removal pathways and related fractionation between 238U and 235U isotopes in deep anoxic groundwater systems remain elusive. Here we show bacteria-driven degradation of organic constituents that influences formation of sulfidic species facilitating reduction of geochemically mobile U(VI) with subsequent trapping of U(IV) by calcite and Fe-sulfides. The isotopic signatures recorded for U and Ca in fracture water and calcite samples provide additional insights on U(VI) reduction behaviour and calcite growth rate. The removal efficiency of U from groundwater reaching 75% in borehole sections in fractured granite, and selective U accumulation in secondary minerals in exceedingly U-deficient groundwater shows the potential of these widespread mineralogical sinks for U in deep anoxic environments.

Item Type: Publication - Article
Digital Object Identifier (DOI):
ISSN: 2662-4435
Date made live: 19 May 2023 13:26 +0 (UTC)

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