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Fast microbial reduction of ferrihydrite colloids from a soil effluent

Title data

Fritzsche, Andreas ; Bosch, Julian ; Rennert, Thilo ; Heister, Katja ; Braunschweig, Juliane ; Meckenstock, Rainer U. ; Totsche, Kai Uwe:
Fast microbial reduction of ferrihydrite colloids from a soil effluent.
In: Geochimica et Cosmochimica Acta. Vol. 77 (2012) . - pp. 444-456.
ISSN 0016-7037

Abstract in another language

Recent studies on the microbial reduction of synthetic iron oxide colloids showed their superior electron accepting propertyin comparison to bulk iron oxides. However, natural colloidal iron oxides differ in composition from their synthetic counterparts.Besides a potential effect of colloid size, microbial iron reduction may be accelerated by electron-shuttling dissolvedorganic matter (DOM) as well as slowed down by inhibitors such as arsenic. We examined the microbial reduction ofOM- and arsenic-containing ferrihydrite colloids. Four effluent fractions were collected from a soil column experiment rununder water-saturated conditions. Ferrihydrite colloids precipitated from the soil effluent and exhibited stable hydrodynamicdiameters ranging from 281 (±146) nm in the effluent fraction that was collected first and 100 (±43) nm in a subsequentlyobtained effluent fraction. Aliquots of these oxic effluent fractions were added to anoxic low salt medium containing dilutedsuspensions of Geobacter sulfurreducens. Independent of the initial colloid size, the soil effluent ferrihydrite colloids werequickly and completely reduced. The rates of Fe2+ formation ranged between 1.9 and 3.3 fmol h1 cell1, and are in the rangeof or slightly exceeding previously reported rates of synthetic ferrihydrite colloids (1.3 fmol h1 cell1), but greatly exceedingpreviously known rates of macroaggregate-ferrihydrite reduction (0.07 fmol h1 cell1). The inhibition of microbial Fe(III)reduction by arsenic is unlikely or overridden by the concurrent enhancement induced by soil effluent DOM. These organicspecies may have increased the already high intrinsic reducibility of colloidal ferrihydrite owing to quinone-mediated electronshuttling. Additionally, OM, which is structurally associated with the soil effluent ferrihydrite colloids, may also contribute tothe higher reactivity due to increasing solubility and specific surface area of ferrihydrite. In conclusion, ferrihydrite colloidsfrom soil effluents can be considered as highly reactive electron acceptors in anoxic environments.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER109773
Institutions of the University: Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Research Institutions
Research Institutions > Research Centres
Result of work at the UBT: Yes
DDC Subjects: 500 Science
Date Deposited: 07 Aug 2015 06:59
Last Modified: 07 Aug 2015 06:59