Premium
Iron Oxide Mineralogy of Well‐drained Ultisols and Oxisols: I. Characterization of Iron Oxides in Soil Clays by Mössbauer Spectroscopy, X‐ray Diffractometry, and Selected Chemical Techniques
Author(s) -
Bigham J. M.,
Golden D. C.,
Bowen L. H.,
Buol S. W.,
Weed S. B.
Publication year - 1978
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1978.03615995004200050033x
Subject(s) - ultisol , maghemite , hematite , magnetite , goethite , ammonium oxalate , iron oxide , mössbauer spectroscopy , oxisol , coprecipitation , chemistry , lepidocrocite , jarosite , oxide , mineralogy , silicate , ferrihydrite , inorganic chemistry , superparamagnetism , nontronite , materials science , clay minerals , geology , metallurgy , soil water , crystallography , magnetization , quantum mechanics , physics , magnetic field , organic chemistry , adsorption , soil science
The iron oxides in subsoil clays (<0.2 µm) from five North Carolina Ultisols and two Brazilian Oxisols were analyzed by Mössbauer spectroscopy, X‐ray diffractometry, and selected chemical techniques. Goethite and hematite were identified as the dominant crystalline iron oxides in these clays. Partial substitution of Al(III) or other nonmagnetic ions for Fe(III) in the oxide structures caused reduced unit cell dimensions and subnormal effective internal magnetic fields. All samples exhibited strong superparamagnetic relaxation, a collapse of the Mössbauer magnetic splitting at ambient temperatures due to the ultrafine size of the oxide particles. Negligible amounts of iron were solubilized with acid ammonium oxalate; however, the Ultisol clays did contain significant amounts of silicate and/or interlayer iron that was not extractable with dithionite‐citrate‐bicarbonate.