نتایج جستجو برای: ferrihydrite
تعداد نتایج: 542 فیلتر نتایج به سال:
Iron (Fe) oxides exist in a spectrum of structures in the environment, with ferrihydrite widely considered the most bioavailable phase. Yet, ferrihydrite is unstable and rapidly transforms to more crystalline Fe(III) oxides (e.g., goethite, hematite), which are poorly reduced by model dissimilatory Fe(III)-reducing microorganisms. This begs the question, what processes and microbial groups are ...
Although iron- and sulfate-reducing bacteria in subsurface environments have crucial roles in biogeochemical cycling of C, Fe, and S, how specific electron donors impact the compositional structure and activity of native iron- and/or sulfate-reducing communities is largely unknown. To understand this better, we created bicarbonate-buffered batch systems in duplicate with three different electro...
and abiogenic ferrihydrite: The influence of silica and implications for ancient environments (Forthcoming/Available Online), Geochimica et Cosmochimica Acta. NOTICE: this is the author's version of a work that was accepted for publication in Geochimica et Cosmochimica Acta. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and othe...
Infrared reflectance spectra of carefully selected Mars soil analog materials have been measured under low atmospheric pressures and temperatures. Chemically altered montmorillonites containing ferrihydrite and hydrated ferric sulfate complexes are examined, as well as synthetic ferrihydrite and a palagonitic soil from Haleakala, Maui. Reflectance spectra of these analog materials exhibit subtl...
Iron (oxyhydr)oxides are sensitive indicators of pH, Eh, temperature, microbial activity, and climate conditions in the Critical Zone. The most ubiquitous environmentally significant iron oxides soils two-line ferrihydrite, goethite, hematite. Here we present a comprehensive study transformation ferrihydrite to hematite goethite over wide range temperature (25–170 °C) initial pH (2−13) through ...
Organic matter (OM)-mineral complexation plays a critical role in soil carbon (C) stabilization. However, direct investigations of organo-mineral associations have been hampered by a lack of methods that can simultaneously characterize soil organic matter and soil minerals. We have applied scanning transmission X-ray microscopy (STXM), combined with near edge X-ray absorption fine structure (NE...
The tandem gene clusters orfR-ombB-omaB-omcB and orfS-ombC-omaC-omcC of the metal-reducing bacterium Geobacter sulfurreducens PCA are responsible for trans-outer membrane electron transfer during extracellular reduction of Fe(III)-citrate and ferrihydrite [a poorly crystalline Fe(III) oxide]. Each gene cluster encodes a putative transcriptional factor (OrfR/OrfS), a porin-like outer-membrane pr...
Recent studies of uranium(VI) geochemistry have focused on the potentially important role of the aqueous species, CaUO2(CO3)3 2 and Ca2UO2(CO3)3 (aq), on inhibition of microbial reduction and uranium(VI) aqueous speciation in contaminated groundwater. However, to our knowledge, there have been no direct studies of the effects of these species on U(VI) adsorption by mineral phases. The sorption ...
The multi-heme, outer membrane c-type cytochrome (c-Cyt) OmcB of Geobacter sulfurreducens was previously proposed to mediate electron transfer across the outer membrane. However, the underlying mechanism has remained uncharacterized. In G. sulfurreducens, the omcB gene is part of two tandem four-gene clusters, each is predicted to encode a transcriptional factor (OrfR/OrfS), a porin-like outer ...
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