Ferrihydrite-Humic Associations

Autor: Udo Schwertmann, Heike Knicker, F. Wagner
Přispěvatelé: German Research Foundation
Rok vydání: 2005
Předmět:
Zdroj: Digital.CSIC. Repositorio Institucional del CSIC
instname
ISSN: 0361-5995
DOI: 10.2136/sssaj2004.0274
Popis: 7 pages, 6 figures, 1 table, 18 references.
Humic–iron oxide associations are believed to exist in various surface environments, such as soils and surface waters, and may add substantially to the stability of organic matter under oxidizing surface conditions. However, a nondestructive, solid-state characterization of such associations is still lacking. In this paper synthetic coprecipitates between humic material (dissolved organic matter; DOM) obtained from a Podzol and synthetic ferrihydrite are examined using X-ray diffraction (XRD) patterns and Fe-specific Mössbauer spectra at temperatures between 4.2 K and room temperature. Lepidocrocite formed in the absence of DOM. However, DOM induced the formation of a four (XRD)-line ferrihydrite that contained 96 mg C/kg. In contrast to a pure four-line ferrihydrite, which was completely magnetically ordered at 4.2 K, the synthesized DOM–ferrihydrite was not fully ordered at 4.2 K and had a magnetic hyperfine field 1 to 2 T lower than the pure ferrihydrite. Such an effect was not observed when DOM was only surface-adsorbed. We conclude that organic components of the DOM coprecipitated with the ferrihydrite. Their interaction with the Fe atoms of the oxide prevents complete spin freezing at 4.2 K. Solid-state 13C nuclear magnetic resonance (NMR) spectra suggested that O-alkyl C of the DOM was mainly responsible for the interaction with the Fe in the oxide.
Deutsche Forschungsgemeinschaft financial support.
Databáze: OpenAIRE
Externí odkaz: