Heidelberg 2006 – wissenschaftliches Programm
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UP: Umweltphysik
UP 19: Neuartige Messverfahren der Umweltphysik
UP 19.7: Fachvortrag
Dienstag, 14. März 2006, 18:00–18:15, A
Characterization and distribution of soluble and insoluble impurities in ice depending on the mode of freezing by synchrotron computer tomography — •Markus Maria Miedaner1, Thomas Huthwelker2, Frieder Enzmann1, Stampanoni Marco3, Michael Kersten1, and Markus Ammann2 — 1Johannes Gutenberg-Universität, Institut für Geowissenschaften, Becherweg 2, 55099 Mainz — 2Laboratory for Radiochemistry and Environmental Chemistry,CH-5232 Villigen PSI, Switzerland — 3Swiss Light Source (SLS), CH-5232 Villigen Switzerland
Impurities in ice play a key role in atmospheric chemistry, as they may host important chemical reactions. When salt solutions freeze, the dissolved impurities are expelled from the ice crystal matrix into micrometer-sized inclusions. We characterize the location and morphology of these gaseous, solid and liquid impurities in three dimensions, using synchrotron based micro-tomography with a spatial resolution of 1.4 µm.
Samples include salt solutions (NaBr, NaCl) as well as mixtures with organic solvents and solid particles. A strong temperature dependence of the impurity distribution was found. Furthermore, we compare sample frozen on a hydrophobic matter with sample frozen in an acoustic trap. Moreover, we investigated the transport of impurities during temperature cycles. Main finding is that air behaves contrary to the salt. Identical behavior was found in natural samples (graupel) under the same conditions. We present a model to simulate the cumulative volume distribution of trapped inclusion of salt and air.