Aggregate-scale spatial heterogeneity in reductive transformation of ferrihydrite resulting from coupled biogeochemical and physical processes

Pallud, Céline; Masue-Slowey, Yoko; Fendorf, Scott

doi:10.1016/j.gca.2010.01.032

Cited by 42 publications

(43 citation statements)

References 31 publications

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“…Our guiding hypothesis was that aggregatescale transport coupled to microbial Se reduction will lead to systematic spatial concentration gradients within aggregates. Similarly to what has been observed for Fe minerals and As (Pallud et al, 2010a(Pallud et al, , 2010bMasue-Slowey et al, 2011), we expected Se reduction rates and emergent gradients to depend on the bulk chemical concentrations of C source and electron acceptor, aeration conditions, microbial activity, and the presence of sorptive phases in the solid matrix of aggregates. Our objective was thus to assess the impact of these factors on aggregate-scale Se reduction and transport as well as to characterize emergent chemical gradients.…”

supporting

confidence: 52%

“…Ar fi cial Aggregate Construc on Spherical (2.5-cm diameter) aggregates were constructed in the laboratory using the protocol developed by Pallud et al (2010b). Aggregates were composed of either pure fi ne quartz sand (IOTA 4 pure quartz powder, grain size of 150-250 μm, Unimin Corporation) or ferrihydrite-coated quartz sand (8-10 g Fe kg −1 aggregate, synthesis [Schwertmann and Cornell, 2000] and coating [Pallud et al, 2010b] as previously described), and contained a homogenous distribution of either E. cloacae or T. selenatis.…”

Section: Methodsmentioning

confidence: 99%

“…Th e physical similarity of constructed and natural soil aggregates has previously been confi rmed by Hg porosimetry measurements (performed on ferrihydrite-coated sand aggregates). Th eir apparent dry bulk density is 1.19 g cm −3 and they have an average pore diameter of approximately 39 μm and a porosity of 0.58 (Pallud et al, 2010b). 2 mmol L −1 (from a fi ltered, sterile stock solution) to investigate the impact of reactant concentrations.…”

Section: Methodsmentioning

confidence: 99%

“…Tokunaga et al (1994) showed that anoxic microzones within fl at synthetic soil aggregates (1-3 cm in diameter) are likely to support localized sites of Se reduction and documented transport-controlled reduction of soluble Cr(VI) to solid Cr(III) taking place exclusively within the surface layer of natural soil aggregates (9-15-cm dimensions) immersed in a Cr(VI) solution (Tokunaga et al, 2003). Pallud et al (2010aPallud et al ( , 2010b recently investigated ferrihydrite reduction in anoxic fl ow-through experiments utilizing novel artifi cial aggregate systems that closely mimic fi eld transport conditions in structured soils and found strong radial gradients in secondary mineralization products as a result of mass-transfer limitations. Utilizing the same artifi cial aggregate systems, Masue-Slowey et al (2011) investigated As reduction and release in artifi cial aggregates surrounded by oxic solution and found, through reactive transport modeling, that the development of an anoxic region within the aggregate best described their experimental results.…”

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confidence: 99%

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Soil‐Aggregate‐Scale Heterogeneity in Microbial Selenium Reduction

Kausch

et al. 2012

Vadose Zone Journal

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Given the role of Se as both an environmental contaminant and a micronutrient, the microbial reduction and subsequent sequestration of bioavailable Se in soils are of great ecological interest. Primary particles in surface soils are typically bound into loosely packed, microporous aggregates, which may be critical spatial units in determining the fate of Se in soils. Surrounded by macropores where preferential flow rapidly advects dissolved compounds, soil aggregates are domains of slow diffusive transport where spatial variations in chemical concentrations and biogeochemical reactions can prevail. We conducted a series of controlled flow‐through experiments utilizing three‐dimensional, artificial soil aggregates (2.5‐cm i.d.) surrounded by a macropore. Aggregates were composed of either quartz sand or ferrihydrite‐coated sand inoculated with one of two Se‐reducing bacteria (Thauera selenatis or Enterobacter cloacae SLD1a‐1). Selenite export rates varied between 0.02 ± 0.01 and 3.4 ± 0.2 nmol h−1 g−1 as a function of aeration condition and input solution composition (higher SeO42− or C‐source concentrations led to higher SeO32− export). Oxic input conditions significantly decreased Se reduction; however, the detection of SeO32− in effluent samples indicates the occurrence of anoxic microzones within aggregates. Furthermore, we found that solid‐phase concentrations of reduced Se increased toward the core of aggregates and are estimated to at least double within the first millimeter into the aggregate under all conditions investigated. This indicates that concentrations of reduced Se may generally be expected to increase with distance from the advection boundary (macropore) inside aggregates, which would imply that soils with larger aggregates retain more Se.

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supporting

confidence: 52%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Soil‐Aggregate‐Scale Heterogeneity in Microbial Selenium Reduction

Kausch

et al. 2012

Vadose Zone Journal

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“…Physical heterogeneity within soils is known to give rise to localized biogeochemical gradients due to the presence of both advection (in large pores) and diffusion (in smaller micropores)-dominated domains (Tufano et al 2009;Pallud et al 2010;Masue-Slowey et al 2013 concentration is an important parameter influencing the transformation of ferrihydrite to secondary Fe minerals and hence sequestration and release of contaminants like arsenic (Pedersen et al 2005;Hansel et al 2003;Latta et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Understanding abiotic ferrihydrite re-mineralization by ferrous ions

Raghav

Sáez

Ela

2014

Int. J. Environ. Sci. Technol.

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In this work, we study the abiotic re-mineralization of ferrihydrite under reducing conditions, obtained by adding zero-valent iron (ZVI) to a suspension of ferrihydrite particles. Under similar conditions, the system (ferrihydrite and ZVI) proceeded along two different transformation pathways differentiated by whether a magnetic stirrer or an overhead stirrer was used for mixing. X-ray diffraction characterization of the solid products showed that magnetite was the sole product of ferrihydrite transformation when a magnetic stirrer was used, whereas both goethite and magnetite were formed when an overhead stirrer was used. The system also behaved differently in terms of transformation kinetics and amount of magnetite formed. The quantification of magnetite generated was performed using a procedure developed in this study. The role of four mechanisms was investigated to explain these observed differences, namely-(1) presence/absence of high local Fe 2? concentrations, (2) mechanical abrasion, (3) presence/absence of a magnetic field, and (4) presence/ absence of a crystalline ZVI surface. Ferrous ions are expected to be concentrated near the magnetic bead on the magnetic stirrer as opposed to a more dispersed distribution with the overhead stirrer. This mechanistic study concluded that the presence of high local Fe 2? concentrations in the system leads to magnetite formation and the absence of the same leads to mixed goethite/magnetite or magnetite-free systems. These findings have significant implications for the mobilization of arsenic from iron (III) hydroxides as the conditions move from oxidizing to reducing, such as often occurs in engineered landfills and natural carbon-rich sediments.

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Formation and Transformation of Iron‐Bearing Minerals by Iron(II)‐Oxidizing and Iron(III)‐Reducing Bacteria

Miot

Etique

2016

Iron Oxides

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Aggregate-scale spatial heterogeneity in reductive transformation of ferrihydrite resulting from coupled biogeochemical and physical processes

Cited by 42 publications

References 31 publications

Soil‐Aggregate‐Scale Heterogeneity in Microbial Selenium Reduction

Soil‐Aggregate‐Scale Heterogeneity in Microbial Selenium Reduction

Understanding abiotic ferrihydrite re-mineralization by ferrous ions

Formation and Transformation of Iron‐Bearing Minerals by Iron(II)‐Oxidizing and Iron(III)‐Reducing Bacteria

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