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UP: Fachverband Umweltphysik

UP 9: Methoden II

UP 9.3: Vortrag

Donnerstag, 5. März 2009, 17:12–17:24, VMP 8 R206

The SO2 camera - a novel method for quantifying spatial SO2 distributions at high time resolution. — •Markus Woehrbach, Christoph Kern, Leif Vogel, Matthias Fickel, and Ulrich Platt — Institut fuer Umweltphysik, University of Heidelberg, Heidelberg, Germany

Sulfur dioxide (SO₂) distributions in volcanic plumes are typically determined via spectroscopic measurements in scanning-mode or through instrument traverses. The SO₂ camera system presented here records two-dimensional images of the SO₂ distribution at a high temporal resolution and therefore allows the measurement of spatial and temporal variations in the SO₂ distribution that can not be resolved by spectroscopic techniques.
For this, two-dimensional images of the volcanic plume are alternately acquired with a UV-sensitive CCD-camera through two selected bandpass filters. The central wavelength of the first filter is chosen around 310 nm, a wavelength region in which SO₂ absorption is prominent, while the second filter is transparent at around 325 nm and therefore outside the strong SO₂ absorption bands. Intensity ratios of identical picture elements yield the required spectral information for SO₂ detection and quantification.
In recent field studies SO₂-fluxes up to 2000 t/day could be determined at Mt. Etna, Sicily. A dependency of the absorption signal on the spectral characteristics of the prevalent illumination conditions was discovered, with an observable diurnal variation of roughly 10% for sunny days and high variability for overcast days.