Deutsche Tagung f ¨ur Forschung mit ... - SNI-Portal

Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P112
X-ray spectromicroscopy - a tool for environmental sciences
Juergen Thieme 1 , Claudia Schmidt 1 , Sophie-Charlote Gleber 1 , Genoveva
Mitrea 1 , Eva Pereiro Lopez 2
1 Institute for X-Ray Physics, University of Goettingen, Germany – 2 CELLS-ALBA,
Barcelona, Spain
X-ray spectromicroscopy is a powerful tool for addressing key questions in environmental
sciences due to its high spectral and spatial resolution. As X-ray microscopy
achieves a much higher resolution than its visible light counterpart due to the much
shorter wavelength smallest structures around 20 nm in sizecan be seen. Imaging specimens
directly in aqueous media is possible as well as performing spectromicroscopy
studies by choosing an appropriate X-ray wavelength. Due to their surface activity,
colloidal structures are involved in a variety of chemical and physical processes. Nutrients
and toxicants can be bound and immobilized or transported, colloids can attach
to microorganisms building up microhabitats, and organic matter as humic substances
can flocculate due to interaction with metals.
In this work, interest was focused on the appearance of colloidal structures from soils
and groundwater aquifers, their distribution and the effect of changing chemical conditions
in the aqueous environment. X-ray microscopy images reveal the morphology
and its changes due to varied chemical conditions. With X-ray spectromicroscopy organic
matter could be identified within structures of soil colloids and spectra have been
analyzed for major components. Functional groups have been determined and mapped
in relation to changes in the chemical condition. The role of different sulfur species in
an entire soil profile has been assessed. Clay dispersions and microhabitats as well as
humic substances have been imaged tomographically. The 3D reconstruction conveys
the influence of oxidation on the morphology of humic substances as well as the internal
structure of associations of bacteria and inorganic soil colloids.