March 2010 issue
Synchrotron radiation in soil and geosciences
soil and geosciences
X-ray spectromicroscopy is a tool excellently suited to studying materials from geo- and environmental sciences, and combines high spatial resolution with high spectral resolution, thus connecting morphology with chemistry. Using tomography or the newly developed coherent diffraction imaging, three-dimensional information about the structure of samples on the micro- and nanoscale can be obtained.
Scanning transmission X-ray microscopy/C 1s-NEXAFS, laser scanning luminescence microscopy and quantum chemistry are combined for the characterization of humic acid metal ion complex formation.
The combination of laterally resolving S and Fe µ-XANES reveals relationships between the distribution and the oxidation state of sulfur and iron in a soil aggregate.
Around 80% of the initial Cr(VI) was reduced to Cr(OH)3 by natural organic matter in a 4.0 wt% Cr(VI)-doped latosol soil treated at temperatures ≤378 K.
XANES has provided key information on the inorganic mercury speciation of geological samples without any sample pre-treatment. The mobility of mercury in mining environments shows a strong dependence on metallurgy treatment and presence of chlorides and sulfates.
XANES investigations have revealed that mercury speciation in a polluted soil is changing, going down with size from the bulk soil to the colloidal fraction.
Shells of the freshwater bivalve Diplodon chilensis patagonicus were studied with XANES spectroscopy. Mn in these shells is most probably Mn(II), and the speciation state of this element does not depend on sample provenance, ontogenetic age, Mn concentration or seasonal deposition.
This work exemplifies the utilization of in situ EXAFS and XANES to reveal speciation, dissolution and electromigration of copper recovered from a copper-rich sludge using electrokinetic methods. About 85% of the copper is dissolved in the aqueous phase, 13% of which is migrated and enriched on the cathode after 120 min of electrokinetic treatment.
High-resolution synchrotron-based powder X-ray diffraction data have been used in the structural refinement of synthetic analogues of the pyromorphite–mimetite solid solution series. The series was confirmed to be continuous at near-Earth-surface conditions.
Synchrotron X-ray computed microtomography has been used to generate three-dimensional views of the internal textures of volcanic rocks and to link such features to processes occurring in volcanic conduits.
Failures of laterally extended polymer composite panels are imaged using 3D computed laminography. The experimental parameters and capability of the method are studied.
Single-bounce glass monocapillary X-ray optics provide a practical and effective means of upgrading existing synchrotron beamlines for microcrystallography.
The first practical application of microfocusing kinoform lenses for the X-ray reflectivity characterization of thin layered materials is demonstrated.
A differential pumping system has been constructed for the windowless connection of a soft X-ray high-vacuum beamline and an experimental chamber under normal atmospheric conditions.
Single-crystal diffuse X-ray microdiffraction was used to characterize radiation-induced defects in individual grains of a polycrystalline proton-irradiated Fe foil.
Scanning small-angle X-ray scattering patterns of dip-coated polyamide 6 monofilaments are tomographically reconstructed based on Abel inversion. The reconstructed sequence reflects the local nanostructure variation along the filament radius.
A preliminary comparison between the trace metal distributions in diseased and healthy teeth suggests that Zn, Cu and Ni may play a role in the progression of periodontal disease.
The combined techniques of wavelength-dispersive X-ray fluorescence spectrometry and X-ray absorption near-edge spectroscopy were used to present the possible roles of calcium, chlorine, phosphorus and sulfur in the etiology of dementias in elderly patients.
A novel experimental set-up for in operando studies of homogeneous catalyzed reactions under laboratory conditions has been developed and tested, which combines time-resolved X-ray absorption spectroscopy with UV/Vis spectroscopy.
The Landweber iteration approach is used to construct the radial pair distribution function (RPDF) as a solution of the fundamental EXAFS integral equation. The RPDF is determined for theoretical and real examples in a stable way without supplementary conditions.
Micro-radiography using hard X-ray synchrotron radiation is the first potential tool to allow an evaluation of the mechanical behavior of the dental implant–abutment complex during force application, thus enabling the enhancement of the design of dental implants which has been based on theoretical analysis to date.