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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 10, issue 1 | Copyright
Atmos. Meas. Tech., 10, 1-14, 2017
https://doi.org/10.5194/amt-10-1-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 02 Jan 2017

Research article | 02 Jan 2017

Remote sensing of volcanic CO2, HF, HCl, SO2, and BrO in the downwind plume of Mt. Etna

André Butz1,5,6, Anna Solvejg Dinger2, Nicole Bobrowski2,3, Julian Kostinek1, Lukas Fieber2, Constanze Fischerkeller1, Giovanni Bruno Giuffrida4, Frank Hase1, Friedrich Klappenbach1, Jonas Kuhn2, Peter Lübcke2, Lukas Tirpitz2, and Qiansi Tu1 André Butz et al.
  • 1IMK-ASF, Karlsruhe Institute of Technology (KIT), Leopoldshafen, Germany
  • 2Institute for Environmental Physics, Heidelberg University, Germany
  • 3Institute of Geosciences, Johannes Gutenberg University Mainz, Germany
  • 4Istituto Nazionale di Geofisica e Vulcanologia, Palermo, Italy
  • 5Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Oberpfaffenhofen, Germany
  • 6Meteorologisches Institut, Ludwig-Maximilians-Universität (LMU), München, Germany

Abstract. Remote sensing of the gaseous composition of non-eruptive, passively degassing volcanic plumes can be a tool to gain insight into volcano interior processes. Here, we report on a field study in September 2015 that demonstrates the feasibility of remotely measuring the volcanic enhancements of carbon dioxide (CO2), hydrogen fluoride (HF), hydrogen chloride (HCl), sulfur dioxide (SO2), and bromine monoxide (BrO) in the downwind plume of Mt. Etna using portable and rugged spectroscopic instrumentation. To this end, we operated the Fourier transform spectrometer EM27/SUN for the shortwave-infrared (SWIR) spectral range together with a co-mounted UV spectrometer on a mobile platform in direct-sun view at 5 to 10km distance from the summit craters. The 3 days reported here cover several plume traverses and a sunrise measurement. For all days, intra-plume HF, HCl, SO2, and BrO vertical column densities (VCDs) were reliably measured exceeding 5 × 1016, 2 × 1017, 5 × 1017, and 1 × 1014moleccm−2, with an estimated precision of 2.2 × 1015, 1.3 × 1016, 3.6 × 1016, and 1.3 × 1013moleccm−2, respectively. Given that CO2, unlike the other measured gases, has a large and well-mixed atmospheric background, derivation of volcanic CO2 VCD enhancements (ΔCO2) required compensating for changes in altitude of the observing platform and for background concentration variability. The first challenge was met by simultaneously measuring the overhead oxygen (O2) columns and assuming covariation of O2 and CO2 with altitude. The atmospheric CO2 background was found by identifying background soundings via the co-emitted volcanic gases. The inferred ΔCO2 occasionally exceeded 2 × 1019moleccm−2 with an estimated precision of 3.7 × 1018moleccm−2 given typical atmospheric background VCDs of 7 to 8 × 1021moleccm−2. While the correlations of ΔCO2 with the other measured volcanic gases confirm the detection of volcanic CO2 enhancements, correlations were found of variable significance (R2 ranging between 0.88 and 0.00). The intra-plume VCD ratios ΔCO2SO2, SO2HF, SO2HCl, and SO2BrO were in the range 7.1 to 35.4, 5.02 to 21.2, 1.54 to 3.43, and 2.9 × 103 to 12.5 × 103, respectively, showing pronounced day-to-day and intra-day variability.

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Remote sensing of the gaseous composition of non-eruptive, passively degassing volcanic plumes can be a tool for volcano monitoring. Here, we report on a field study that demonstrates the feasibility of remotely measuring the volcanic enhancements of carbon dioxide, hydrogen fluoride, hydrogen chloride, sulfur dioxide, and bromine monoxide in the plume of Mt. Etna using portable spectroscopic instrumentation sampling the plume several kilometers downwind of the source.
Remote sensing of the gaseous composition of non-eruptive, passively degassing volcanic plumes...
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