XAS study of Fe mineralogy in a chronosequence of soil clays formed in basaltic cinders
Baker, Leslie L. (University of Idaho. Soil and Land Resources Division)
Strawn, Daniel G. (University of Idaho. Soil and Land Resources Division)
Vaughan, Karen L. (United States Department of Agriculture. Natural Resources Conservation Service (NRCS-USDA))
McDaniel, Paul A. (University of Idaho. Soil and Land Resources Division)

Data:	2010
Resum:	The characterization of poorly crystalline minerals formed by weathering is difficult using conventional techniques. The objective of this study was to use cutting-edge spectroscopic techniques to characterize secondary Fe mineralogy in young soils formed in basaltic cinders in a cool, arid environment. The mineralogy of a chronosequence of soils formed on 2, 6, and 15 thousand year old basaltic cinders at Craters of the Moon National Monument (COM) was examined using synchrotron-based X-ray absorption fine structure (XAFS) spectroscopy in combination with selective extractions. Fe K-edge XAFS is useful for determining speciation in poorly crystalline materials such as young weathering products. Over 86% of Fe in the soil clay fractions was contained in poorly crystalline materials, mostly in the form of ferrihydrite, with the remainder in a poorly crystalline Fe-bearing smectite. The XAFS spectra suggest that ferrihydrite in the 15 ka soil clay is more resistant to ammonium oxalate (AOD) extraction than is ferrihydrite in the younger materials. Fe in the poorly crystalline smectite is subject to dissolution during citrate-bicarbonatedithionite (CBD) extraction. The results indicate that relatively few mineralogical changes occur in these soils within the millennial time frame and under the environmental conditions associated with this study. Although the secondary mineral suite remains similar in the soils of different ages, ferrihydrite crystallinity appears to increase with increasing soil age.
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Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Fe mineralogy ; Ferrihydrite ; Smectite ; Weathering ; XAFS
Publicat a:	Clays and Clay Minerals, Vol. 58, Núm. 6 (2010) , p. 772-782, ISSN 1552-8367

DOI: 10.1346/CCMN.2010.0580605

11 p, 891.4 KB  Accés restringit a la UAB

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