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| Titel |
Variations of the BrO/SO2 molar ratios during the 2015 Cotopaxi eruption |
| VerfasserIn |
Florian Dinger, Santiago Arellano, Jean Battaglia, Nicole Bobrowski, Bo Galle, Stephen Hernandez, Silvana Hidalgo, Christoph Hörmann, Peter Lübcke, Ulrich Platt, Mario Ruiz, Simon Warnach, Thomas Wagner |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250122068
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| Publikation (Nr.) |
 EGU/EGU2016-1001.pdf |
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| Zusammenfassung |
| Cotopaxi volcano is located 50 km south of Quito, the capital of Ecuador. In case of a large eruption producing lahars, these may cause damage to the inhabited areas located to the south and north of the volcano and to the local water supply and other infrastructure. After almost 140 years of relative quiescence, increasing activity is observed in seismicity and gas emissions since May 2015. During August 2015 ash and gas emissions are recorded. Cotopaxi volcano is part of the Network for Observation of Volcanic and Atmospheric Change (NOVAC) since 2009, thus the observations include the overall eruptive activity onset and its evolution. NOVAC regularly monitors the SO$_2$ emissions of more than 30 volcanoes using scanning UV-spectrometers. Today, monitoring of volcanic SO$_2$ emissions by UV-spectrometers is a widespread tool but its interpretation can be improved by additionally recording halogen/sulphur emission ratios. Recently, it has been shown that spectra from NOVAC instruments can also be used to retrieve the BrO/SO$_2$ molar ratio by applying Differential Optical Absorption Spectroscopy (DOAS).\\
We apply this new technique to analyse the plume composition of Cotopaxi volcano and will present time series of the BrO/SO$_2$ ratios as monitored by the ground-based NOVAC instruments since March 2015. The SO$_2$ column densities were below $6\cdot10^{16}\,\frac{\text{molec}}{\text{cm}^2}$ prior to May 2015 and up to $1.5\cdot10^{18}\,\frac{\text{molec}}{\text{cm}^2}$ between May and August 2015. For these periods, the BrO column densities were below the detection limit of $3\cdot10^{13}\,\frac{\text{molec}}{\text{cm}^2}$. After the phreatic explosions on 14.08.2015, SO$_2$ column densities of up to $3\cdot10^{18}\,\frac{\text{molec}}{\text{cm}^2}$ and BrO column densities of up to $5\cdot10^{14}\,\frac{\text{molec}}{\text{cm}^2}$ were observed. Until December 2015 these SO$_2$ column densities kept at about the same level but the BrO column densities increased up to $3\cdot10^{14}\,\frac{\text{molec}}{\text{cm}^2}$. After the phreatic explosions we find a detectable signal of BrO. Soon after the eruption the BrO/SO$_2$ molar ratio was low as $1\cdot10^{-5}$, but during September-December 2015 this ratio varies between $3-11\cdot10^{-5}$ as observed by three NOVAC stations. The variations in the BrO/SO$_2$ ratios are compared with SO$_2$ measurements from NOVAC and satellite observations as well as seismic data and volcanological observations. |
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