Origin and stability of uranium accumulation-layers in an Alpine histosol.

Details

Serval ID
serval:BIB_5DC855874EEF
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Origin and stability of uranium accumulation-layers in an Alpine histosol.
Journal
The Science of the total environment
Author(s)
Peña J., Straub M., Flury V., Loup E., Corcho J., Steinmann P., Bochud F., Froidevaux P.
ISSN
1879-1026 (Electronic)
ISSN-L
0048-9697
Publication state
Published
Issued date
20/07/2020
Peer-reviewed
Oui
Volume
727
Pages
138368
Language
english
Notes
Publication types: Journal Article
Publication Status: ppublish
Abstract
Uranium (U) accumulation in organic soils is a common phenomenon that can lead to high U concentration in montane wetlands. The stability of the immobilized U in natural wetlands following redox fluctuations and re-oxidation events, however, is not currently known. In this study, we investigated a saturated histosol that had accumulated up to 6000 ppm of U at 30 cm below ground level (bgl). Uranium in the waters feeding the wetland originates from the weathering of surrounding gneiss rocks, a process releasing trace amounts (<3 ppb) of soluble U into nearby streams. Redox oscillations in the first 20 cm bgl led to the accumulation of U, Ca, S in low permeability layers at 30 and 45 cm bgl. XRF measurements along the core showed that U strongly correlates with sulfur (S) and calcium (Ca), but not iron (Fe). We tested the stability of uranium in the histosol over a nine-month laboratory amendment of a large core of the histosol (∅ 30 cm; length 55 cm) with up to 500 ppm nitrate. Nitrate addition was followed by complete nitrate reduction and re-generation of oxidizing E <sub>h</sub> conditions in the top 25 cm of the soil without U release to the soil pore waters above background levels (1-2 ppb). Our results demonstrate that, fast reduction of nitrate, sulfate, and Fe(III) occur in the soil without U release. The remarkable stability of sorbed U in the histosol may result from buffering by sulfide and S <sub>n</sub> ° and/or strong U(IV)-OM or U(VI)-OM enhanced by organic S moieties or bridging complexation by Ca. That U in the soil was immobile under nitrate addition for up to 9 months can inform remediation strategies based on the use of artificial wetlands to limit U mobility in contaminated sites.
Keywords
Environmental Engineering, Waste Management and Disposal, Pollution, Environmental Chemistry, Groundwater quality, Nitrate amendment, Organic matter, Redox cycling, U mobility
Pubmed
Web of science
Open Access
Yes
Funding(s)
University of Lausanne
Create date
22/04/2020 11:29
Last modification date
10/07/2020 6:21
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