HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Schwertmann, U. Articles by Knicker, H. Search for Related Content PubMed Articles by Schwertmann, U. Articles by Knicker, H. GeoRef GeoRef Citation Agricola Articles by Schwertmann, U. Articles by Knicker, H. Related Collections Humic Substances Nuclear Magnetic Resonance, NMR

Soil Chemistry

Ferrihydrite–Humic Associations

Magnetic Hyperfine Interactions

^a Institute of Soil Science, Technical Univ. of Munich-Weihenstephan, 85350 Freising, Germany
^b Faculty of Physics, Technical Univ. of Munich-Weihenstephan, 85350 Freising, Germany

^* Corresponding author (uschwert{at}wzw.tum.de)

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.

Abbreviations: DOM, dissolved organic matter • NMR, nuclear magnetic resonance • XRD, X-ray diffraction