Iron-oxide crystallinity increases during soil redox oscillations

Thompson, Aaron; Chadwick, Oliver A.; Rancourt, Denis; Chorover, Jon

doi:10.1016/j.gca.2005.12.005

Cited by 341 publications

(287 citation statements)

References 61 publications

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“…Molecular U(IV) produced by biogenic vivianite and phosphate treated biogenic magnetite Corr et al, 2004) and/or phases with low crystallinity. Similar results have been reported by Van der Zee et al (2003) and Thompson et al (2006) and for soil and sediment samples, and have been attributed to nano-goethite phases. This could also include some transition state between HFO and magnetite.…”

Section: Discussionsupporting

confidence: 90%

“…Similar results have been reported by Goya et al (2003) and Corr et al (2004) for synthetic, nanoparticulate (<10 nm) magnetite. However, the small H is not unique to nano-magnetite and could also correspond to other small particle sizes and/or phases with low crystallinity, consistent with nano-goethite phases as reported by Van der Zee et al (2003) and Thompson et al (2006) and. Siderite was detected as the third mineral phase in the sample (ca.…”

Section: Mö Ssbauer Spectroscopysupporting

confidence: 82%

“…T, again consistent with nanoparticulate phases. The magnetite phase could be confirmed at 77 K. The iron(II) phase in the 77 K spectrum could be interpreted as siderite, consistent with the analysis at 245 K. The spectra at 77 K spectra also showed broader peaks compared to those of highly crystalline samples, typical for small particle sizes that have previously been referred to as 'collapsed sextet' (Van der Zee et al, 2003;Thompson et al, 2006). At 5 K, the H field of the nanoparticulate Fe(III) phase increases to values in the range of magnetite (36-52 T) and cannot be resolved due to overlapping features.…”

Section: Mö Ssbauer Spectroscopysupporting

confidence: 80%

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Products of abiotic U(VI) reduction by biogenic magnetite and vivianite

Veeramani

Alessi

Suvorova

et al. 2011

Geochimica et Cosmochimica Acta

138

122

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Reductive immobilization of uranium by the stimulation of dissimilatory metal-reducing bacteria (DMRB) has been investigated as a remediation strategy for subsurface U(VI) contamination. In those environments, DMRB may utilize a variety of electron acceptors, such as ferric iron which can lead to the formation of reactive biogenic Fe(II) phases. These biogenic phases could potentially mediate abiotic U(VI) reduction. In this work, the DMRB Shewanella putrefaciens strain CN32 was used to synthesize two biogenic Fe(II)-bearing minerals: magnetite (a mixed Fe(II)-Fe(III) oxide) and vivianite (an Fe(II)-phosphate). Analysis of abiotic redox interactions between these biogenic minerals and U(VI) showed that both biogenic minerals reduced U(VI) completely. XAS analysis indicates significant differences in speciation of the reduced uranium after reaction with the two biogenic Fe(II)-bearing minerals. While biogenic magnetite favored the formation of structurally ordered, crystalline UO 2 , biogenic vivianite led to the formation of a monomeric U(IV) species lacking U-U associations in the corresponding EXAFS spectrum. To investigate the role of phosphate in the formation of monomeric U(IV) such as sorbed U(IV) species complexed by mineral surfaces, versus a U(IV) mineral, uranium was reduced by biogenic magnetite that was pre-sorbed with phosphate. XAS analysis of this sample also revealed the formation of monomeric U(IV) species suggesting that the presence of phosphate hinders formation of UO 2 . This work shows that U(VI) reduction products formed during in situ biostimulation can be influenced by the mineralogical and geochemical composition of the surrounding environment, as well as by the interfacial solute-solid chemistry of the solid-phase reductant.

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Section: Discussionsupporting

confidence: 90%

Section: Mö Ssbauer Spectroscopysupporting

confidence: 82%

Section: Mö Ssbauer Spectroscopysupporting

confidence: 80%

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Products of abiotic U(VI) reduction by biogenic magnetite and vivianite

Veeramani

Alessi

Suvorova

et al. 2011

Geochimica et Cosmochimica Acta

138

122

View full text Add to dashboard Cite

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“…A transient state may result in considerably altered properties of the obtained Fe oxides. For example, the degree of Fe oxide crystallinity increased in soil during redox cycles in closed redox-stat reactors (Thompson et al, 2006) while it decreased in soils under in situ conditions (Thompson et al, 2011). In open systems like in the latter study, transient conditions are maintained due to the variable supply of OM (topsoils) and of Si and Ti (subsoils), which inhibit the aging of Fe oxides (Thompson et al, 2011).…”

Section: Introductionmentioning

confidence: 64%

“…The coexistence of organic and inorganic compounds during Fe oxide precipitation was therefore included in dedicated experimental setups, e.g. in redox-stat reactors (Schuth et al, 2015;Thompson et al, 2006), or by the use of natural solutions (Gunnars et al, 2002). However, such approaches do not acknowledge substantial soil features, i.e.…”

Section: Introductionmentioning

confidence: 99%

Structure and composition of Fe–OM co-precipitates that form in soil-derived solutions

Fritzsche

Schröder

Wieczorek

et al. 2015

Geochimica et Cosmochimica Acta

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Iron oxides represent a substantial fraction of secondary minerals and particularly affect the reactive properties of natural systems in which they formed, e.g. in soils and sediments. Yet, it is still obscure how transient conditions in the solution will affect the properties of in situ precipitated Fe oxides. Transient compositions, i.e. compositions that change with time, arise due to predominant non-equilibrium states in natural systems, e.g. between liquid and solid phases in soils. In this study, we characterize Fe-OM co-precipitates that formed in pH-neutral exfiltrates from anoxic topsoils under transient conditions. We applied soil column outflow experiments, in which Fe 2+ was discharged with the effluent from anoxic soil and subsequently oxidized in the effluent due to contact with air. Our study features three novel aspects being unconsidered so far: 3

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River bank geomorphology controls groundwater arsenic concentrations in aquifers adjacent to the Red River, Hanoi Vietnam

Stahl

Harvey

Geen

et al. 2016

Water Resources Research

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Many aquifers that are highly contaminated by arsenic in South and Southeast Asia are in the floodplains of large river networks. Under natural conditions, these aquifers would discharge into nearby rivers; however, large‐scale groundwater pumping has reversed the flow in some areas so that rivers now recharge aquifers. At a field site near Hanoi Vietnam, we find river water recharging the aquifer becomes high in arsenic, reaching concentrations above 1000 µg/L, within the upper meter of recently (< ∼10 years) deposited riverbed sediments as it is drawn into a heavily pumped aquifer along the Red River. Groundwater arsenic concentrations in aquifers adjacent to the river are largely controlled by river geomorphology. High (>50 µg/L) aqueous arsenic concentrations are found in aquifer regions adjacent to zones where the river has recently deposited sediment and low arsenic concentrations are found in aquifer regions adjacent to erosional zones. High arsenic concentrations are even found adjacent to a depositional river reach in a Pleistocene aquifer, a type of aquifer sediment which generally hosts low arsenic water. Using geochemical and isotopic data, we estimate the in situ rate of arsenic release from riverbed sediments to be up to 1000 times the rates calculated on inland aquifer sediments in Vietnam. Geochemical data for riverbed porewater conditions indicate that the reduction of reactive, poorly crystalline iron oxides controls arsenic release. We suggest that aquifers in these regions may be susceptible to further arsenic contamination where riverine recharge drawn into aquifers by extensive groundwater pumping flows through recently deposited river sediments before entering the aquifer.

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Iron-oxide crystallinity increases during soil redox oscillations

Cited by 341 publications

References 61 publications

Products of abiotic U(VI) reduction by biogenic magnetite and vivianite

Products of abiotic U(VI) reduction by biogenic magnetite and vivianite

Structure and composition of Fe–OM co-precipitates that form in soil-derived solutions

River bank geomorphology controls groundwater arsenic concentrations in aquifers adjacent to the Red River, Hanoi Vietnam

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