Hamburg 2009 – wissenschaftliches Programm
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UP: Fachverband Umweltphysik
UP 2: Atmosphäre II
UP 2.8: Vortrag
Dienstag, 3. März 2009, 15:42–15:54, VMP 9 HS
Bromine chemistry in volcanic plumes — •Leif Vogel, Christoph Kern, Matthias Fickel, Markus Woehrbach, and Ulrich Platt — Institut für Umweltphysik, Uni Heidelberg
Optical remote sensing via scattered sunlight Differential Optical Absorption Spectroscopy (DOAS) has become a standard tool in volcanology to determine trace gases in volcanic plumes. Bromine monoxide (BrO) and sulphur dioxide (SO2) were simultaneously measured at three different distances (4km, 10km, 16km) from the crater by ground based Multiaxis DOAS in the volcanic plume of Mt. Etna, Italy in July 2008. These distances correspond to plume ages of 3min, 7min, and 11min. Additional measurements of SO2 fluxes were performed by a novel type of SO2 UV-Camera as well as conventional road traverses also applying the DOAS technique. A SO2 flux up to 10000 Mg/d was determined, which is elevated due to Mt. Etna’s state of unrest during that period. For the MaxDOAS measurements, an improved evaluation scheme is proposed, which applies a variable fit range in order to minimize radiative transfer effects. Measured ratios are in the order of BrO/SO2 = 10−4. They are slightly lower than previously reported ratios, which might be explained by the new evaluation scheme. The change of ratio over time due to chemical reactions (e.g. "bromine explosion") is in the range of model calculations, although an unexplained minimum is observed in the ratio at 6.6 minutes plume age.