Beam-induced oxidation of monomeric U(IV) species

Alessi, Daniel S.; Uster, Benjamin; Borca, Camelia N.; Grolimund, Daniel; Bernier‐Latmani, Rizlan

doi:10.1107/s0909049512041763

Cited by 9 publications

(5 citation statements)

References 14 publications

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“…A strontium foil and Soller slits were used to increase the signal-to-noise ratio. Beam damage was not observed during measurement of sequential scans, as expected (47).…”

Section: Methodssupporting

confidence: 49%

Uranium(IV) adsorption by natural organic matter in anoxic sediments

Bone

Dynes

Cliff

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

148

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Uranium is an important carbon-free fuel source and environmental contaminant that accumulates in the tetravalent state, U(IV), in anoxic sediments, such as ore deposits, marine basins, and contaminated aquifers. However, little is known about the speciation of U(IV) in low-temperature geochemical environments, inhibiting the development of a conceptual model of U behavior. Until recently, U(IV) was assumed to exist predominantly as the sparingly soluble mineral uraninite (UO2+x) in anoxic sediments; however, studies now show that this is not often the case. Yet a model of U(IV) speciation in the absence of mineral formation under field-relevant conditions has not yet been developed. Uranium(IV) speciation controls its reactivity, particularly its susceptibility to oxidative mobilization, impacting its distribution and toxicity. Here we show adsorption to organic carbon and organic carbon-coated clays dominate U(IV) speciation in an organic-rich natural substrate under field-relevant conditions. Whereas previous research assumed that U(IV) speciation is dictated by the mode of reduction (i.e., whether reduction is mediated by microbes or by inorganic reductants), our results demonstrate that mineral formation can be diminished in favor of adsorption, regardless of reduction pathway. Projections of U transport and bioavailability, and thus its threat to human and ecosystem health, must consider U(IV) adsorption to organic matter within the sediment environment.

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“…A strontium foil and Soller slits were used to increase the signal-to-noise ratio. Beam damage was not observed during measurement of sequential scans, as expected (47).…”

Section: Methodssupporting

confidence: 49%

Uranium(IV) adsorption by natural organic matter in anoxic sediments

Bone

Dynes

Cliff

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

148

View full text Add to dashboard Cite

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“…The μ-XANES spectra on locations of high U intensity in the hepatic ceca and midgut shared the same characteristics as those collected as part of dry UNP characterization work, suggesting the UNPs retained in daphnids are also oxidized (Figure S4). However, contributing factors from the sample preparation or potential photooxidation incurred on the beamline could not be excluded and further analysis is required to confirm the results from this work.…”

Section: Resultsmentioning

confidence: 97%

Synchrotron XRF and Histological Analyses Identify Damage to Digestive Tract of Uranium NP-Exposed Daphnia magna

Byrnes

Rossbach

Jaroszewicz

et al. 2023

Environ. Sci. Technol.

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Micro- and nanoscopic X-ray techniques were used to investigate the relationship between uranium (U) tissue distributions and adverse effects to the digestive tract of aquatic model organism Daphnia magna following uranium nanoparticle (UNP) exposure. X-ray absorption computed tomography measurements of intact daphnids exposed to sublethal concentrations of UNPs or a U reference solution (URef) showed adverse morphological changes to the midgut and the hepatic ceca. Histological analyses of exposed organisms revealed a high proportion of abnormal and irregularly shaped intestinal epithelial cells. Disruption of the hepatic ceca and midgut epithelial tissues implied digestive functions and intestinal barriers were compromised. Synchrotron-based micro X-ray fluorescence (XRF) elemental mapping identified U co-localized with morphological changes, with substantial accumulation of U in the lumen as well as in the epithelial tissues. Utilizing high-resolution nano-XRF, 400–1000 nm sized U particulates could be identified throughout the midgut and within hepatic ceca cells, coinciding with tissue damages. The results highlight disruption of intestinal function as an important mode of action of acute U toxicity in D. magna and that midgut epithelial cells as well as the hepatic ceca are key target organs.

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“…No beam damage was observed between scans. To assess U oxidation state, linear combination fitting of the near-edge region was performed in Athena using a molecular U(IV) reference obtained from a pure culture of U(VI) reducing bacteria and U(VI) adsorbed to ferrihydrite. Shell-by-shell analysis of extended X-ray absorption fine edge structure (EXAFS) spectra was performed in Artemis with paths calculated (using FEFF 6 L) based on the structures for uraninite, rutherfordine, and ningyoite to obtain information on the local coordination environment of U (within 6 Å) (fitting details provided in SI).…”

Section: Methodsmentioning

confidence: 99%

Oxidative Uranium Release from Anoxic Sediments under Diffusion-Limited Conditions

Bone

Cahill

Jones

et al. 2017

Environ. Sci. Technol.

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Uranium (U) contamination occurs as a result of mining and ore processing; often in alluvial aquifers that contain organic-rich, reduced sediments that accumulate tetravalent U, U(IV). Uranium(IV) is sparingly soluble, but may be mobilized upon exposure to nitrate (NO) and oxygen (O), which become elevated in groundwater due to seasonal fluctuations in the water table. The extent to which oxidative U mobilization can occur depends upon the transport properties of the sediments, the rate of U(IV) oxidation, and the availability of inorganic reductants and organic electron donors that consume oxidants. We investigated the processes governing U release upon exposure of reduced sediments to artificial groundwater containing O or NO under diffusion-limited conditions. Little U was mobilized during the 85-day reaction, despite rapid diffusion of groundwater within the sediments and the presence of nonuraninite U(IV) species. The production of ferrous iron and sulfide in conjunction with rapid oxidant consumption suggested that the sediments harbored large concentrations of bioavailable organic carbon that fueled anaerobic microbial respiration and stabilized U(IV). Our results suggest that seasonal influxes of O and NO may cause only localized mobilization of U without leading to export of U from the reducing sediments when ample organic carbon is present.

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Beam-induced oxidation of monomeric U(IV) species

Cited by 9 publications

References 14 publications

Uranium(IV) adsorption by natural organic matter in anoxic sediments

Uranium(IV) adsorption by natural organic matter in anoxic sediments

Synchrotron XRF and Histological Analyses Identify Damage to Digestive Tract of Uranium NP-Exposed Daphnia magna

Oxidative Uranium Release from Anoxic Sediments under Diffusion-Limited Conditions

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