Reduction of ferrihydrite with adsorbed and coprecipitated organic matter: microbial reduction by Geobacter bremensis vs. abiotic reduction by Na-dithionite
| Autor: | Anke Hädrich, Kirsten Küsel, Julia Neidhardt, Klaus D. Jandt, Kai Uwe Totsche, Karin Eusterhues, Thomas F. Keller |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2014 |
| Předmět: |
chemistry.chemical_classification
Oxide minerals Goethite Geobacter bremensis Inorganic chemistry lcsh:QE1-996.5 Oxide lcsh:Life Dithionite lcsh:Geology chemistry.chemical_compound Ferrihydrite lcsh:QH501-531 chemistry visual_art ddc:570 lcsh:QH540-549.5 visual_art.visual_art_medium Organic matter lcsh:Ecology Dissolution Ecology Evolution Behavior and Systematics Earth-Surface Processes |
| Zdroj: | Biogeosciences, Vol 11, Iss 18, Pp 4953-4966 (2014) Biogeosciences 11(18), 4953-4966 (2014). doi:10.5194/bg-11-4953-2014 |
| ISSN: | 1726-4189 1726-4170 |
| DOI: | 10.5194/bg-11-4953-2014 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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