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| Titel |
Microbially-mediated transformation and mobilization of soil Fe-organic associations |
| VerfasserIn |
Christine Poggenburg, Robert Mikutta, Axel Schippers, Reiner Dohrmann, Stephan Kaufhold, Georg Guggenberger |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250090144
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| Publikation (Nr.) |
 EGU/EGU2014-4363.pdf |
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| Zusammenfassung |
| Soil organic matter (OM) has been proposed to be stabilized in the long term via sorption to
iron((oxy)hydr)oxides under aerobic conditions. However, in an anaerobic environment,
Fe-organic associations may be subject to microbial reduction and mobilization, which
counteract the suggested stabilizing effect of Fe compounds. Desorption of OM can
result in its microbial decomposition causing the emission of greenhouse gases
(CO2, CH4, N2O) or release of associated contaminants into the soil solution and
groundwater.
While the reductive dissolution of pure iron((oxy)hydr)oxides by dissimilatory FeIII
reducing bacteria is well established, little is known about the influence of natural OM on
microbially mediated mobilization of Fe-organic associations. Therefore, this study aims to
elucidate the effect of adsorbed OM on microbial FeIII reduction of Fe-organic associations
with regard to (i) the composition of OM, (ii) the carbon loading, and (iii) surface coverage
and/or pore blockage by adsorbed OM.
Mineral-organic associations with varying carbon contents were synthesized using several
iron((oxy)hydr)oxides (Goethite, Lepidocrocite, Ferrihydrite, Hematite, Magnetite) and OM
of different origin (dissolved OM extracted from the Oa horizon of a Podzol and Oi horizon
of a Cambisol, extracellular polymeric substance extracted from Bacillus subtilis). Incubation
experiments under anaerobic conditions were conducted for 16 days using two
different strains of dissimilatory FeIII reducing bacteria (Shewanella putrefaciens,
Geobacter metallireducens). At five sampling points in time the solution phase was
analyzed for pH, Fetotal, and FeII. The initial mineral-organic associations and
post-incubation phase were characterized by N2 gas adsorption, FTIR, XRD, and
XPS.
The results indicate that the composition of OM and carbon loading significantly
influence the rate and extend of microbial reduction of Fe-organic associations depending on
the type of microbial strain and iron((oxy)hydr)oxide used. |
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