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| Titel |
Reduction of ferrihydrite with adsorbed and coprecipitated organic matter: microbial reduction by Geobacter bremensis vs. abiotic reduction by Na-dithionite |
| VerfasserIn |
K. Eusterhues, A. Hädrich, J. Neidhardt, K. Küsel, T. F. Keller, K. D. Jandt, K. U. Totsche |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 18 ; Nr. 11, no. 18 (2014-09-16), S.4953-4966 |
| Datensatznummer |
250117596
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| Publikation (Nr.) |
 copernicus.org/bg-11-4953-2014.pdf |
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| Zusammenfassung |
| Ferrihydrite is a widespread poorly crystalline Fe oxide which
becomes easily coated by natural organic matter in the environment. This
mineral-bound organic matter entirely changes the mineral surface properties
and therefore the reactivity of the original mineral. Here, we investigated
2-line ferrihydrite, ferrihydrite with adsorbed organic matter, and
ferrihydrite coprecipitated with organic matter for microbial and abiotic
reduction of Fe(III). Ferrihydrite-organic matter associations with
different organic matter loadings were reduced either by Geobacter bremensis or abiotically by
Na-dithionite. Both types of experiments showed decreasing initial Fe-reduction rates and decreasing degrees of reduction with increasing amounts
of mineral-bound organic matter. At similar organic matter loadings,
coprecipitated ferrihydrites were more reactive than ferrihydrites with
adsorbed organic matter. The difference can be explained by the smaller
crystal size and poor crystallinity of such coprecipitates. At small organic
matter loadings the poor crystallinity of coprecipitates led to even faster
Fe-reduction rates than found for pure ferrihydrite. The amount of
mineral-bound organic matter also affected the formation of secondary
minerals: goethite was only found after reduction of organic matter-free
ferrihydrite and siderite was only detected when ferrihydrites with
relatively low amounts of mineral-bound organic matter were reduced. We
conclude that direct contact of G. bremensis to the Fe oxide mineral surface was
inhibited by attached organic matter. Consequently, mineral-bound organic
matter shall be taken into account as a factor in slowing down reductive
dissolution. |
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