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ARS Home » Midwest Area » West Lafayette, Indiana » National Soil Erosion Research Laboratory » Research » Publications at this Location » Publication #91330
Title: SOFT X-RAY SPECTROMICROSCOPY ON HYDRATED COLLOIDAL SYSTEMS

Author
item NEUHAUSLER, U. - STATE UNIV. OF NY
item ABEND, S. - KIEL, GERMANY
item THIEME, J. - GOTTINGEN, GERMANY
item SCHULZE, D. - PURDUE UNIVERSITY
item Stott, Diane
item JACOBSEN, C. - STATE UNIV. OF NY
item LAGALY, G. - KIEL, GERMANY

Submitted to: Clay Mineral Society
Publication Type: Abstract Only
Publication Acceptance Date: 5/31/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Soft x-ray microscopes offer favorable contrast mechanisms for studying colloidal systems. Unlike electron microscopy, samples can be examined in transmission in a hydrated state at atmospheric pressure without any pretreatment, and with a tenfold higher spatial resolution than with visible light microscopy. The energy range of the water window between O - and C - K absorption edges (543 and 284 eV) is of particular interest for studies on hydrated samples, as water there is highly transparent to x rays compared to other substances. In addition, x-ray absorption edges (e.g. C, O, N, Ca) can be used to visualize and map compounds containing these elements versus other compounds. We used soft x-ray microscopy to image hydrated clays, to obtain contrast based on elemental composition, and to highlight chemical states of C. Polyacrylamide is a flocculent that is added to irrigation water, reducing erosion by 94 percent and increasing irrigation water uptake by 15 percent in loam soils. We have used the scanning transmission x-ray microscope (STXM) to visualize the flocculation of a KGa-1 kaolinite clay suspension at various concentrations of polyacrylamide. The results are in good agreement with the concentrations needed for field application, yet provide a very direct way of visualizing the effects of the flocculent. X-ray absorption near-edge spectroscopy (XANES) makes use of the coupling of inner shell electrons to outer lying orbitals (such as molecular orbitals) which are highly senstive to the chemical bonding of the element being probed. We have used carbon XANES to map the characteristics of humic substances, and are undertaking to use C XANES to highlight different organic components in soils in future studies.