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| Titel |
Development and application of compact denuder sampling techniques with in situ derivatization followed by gas chromatography-mass spectrometry for halogen speciation in volcanic plumes |
| VerfasserIn |
Julian Rüdiger, Nicole Bobrowski, Thorsten Hoffmann |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250102990
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| Publikation (Nr.) |
 EGU/EGU2015-2392.pdf |
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| Zusammenfassung |
| Volcanoes are a large source for several reactive atmospheric trace gases including sulphur
and halogen containing species. The detailed knowledge of volcanic plume chemistry can
give insights into subsurface processes and can be considered as a useful geochemical tool for
monitoring of volcanic activity, especially halogen to sulphur ratios (e.g. Bobrowski
and Giuffrida, 2012; Donovan et al., 2014). The reactive bromine species bromine
monoxide (BrO) is of particular interest, because BrO as well as SO2 are readily
measurable by UV spectrometers at a safe distance. Furthermore it is formed in the plume
by a multiphase reaction mechanism under depletion of ozone in the plume. The
abundance of BrO changes as a function of the reaction time and therefore distance from
the vent as well as the spatial position in the plume. Due to the lack of analytical
approaches for the accurate speciation of certain halogens (HBr, Br2, Br, BrCl,
HOBr etc.) there are still uncertainties about the magnitude of volcanic halogen
emissions and in particular their specificationtheir species and therefore also in
the understanding of the bromine chemistry in volcanic plumes (Bobrowski et al.,
2007).
In this study, the first application of a 1,3,5-trimethoxybenzene (1,3,5-TMB)-coated gas
diffusion denuder (Huang and Hoffmann, 2008) on volcanic gases proved to be suitable to
collect selectively gaseous bromine species with oxidation states of +1 or 0 (Br2 and
BrO(H)), while being ignorant to HBr (OS -1). The reaction of 1,3,5-TMB with bromine
gives 1-bromo-2,4,6-trimethoxybenzene (1-bromo-2,4,6-TMB) - other halogens give
corresponding products. The diffusion denuder technique allows sampling of gaseous
compounds exclusively without collecting particulate matter. Choosing a flow rate of 500
mL/
min-1 and a denuder length of 0.5 m a nearly quantitative collection efficiency was
achieved. Solvent elution of the derivatized analytes and subsequent analysis with gas
chromatography-mass spectrometry gives a limit of detection below 1 ng of bromine.
The method was applied on volcanic gas plumes at Mt. Etna and Mt. Stromboli
in Italy in July 2014 and on fumarolic gas emissions at Mt. Lastarria in Chile in
November 2014. The results show significant amounts of the concerning bromine species
(lower ppb range). Comprehensive data evaluation and comparison with results of
impinger extraction with NaOH solution as well as chamber experiments are still in
progress.
References
Bobrowski, N. and G. Giuffrida: Bromine monoxide / sulphur dioxide ratios in relation
to volcanological observations at Mt. Etna 2006-2009. Solid Earth, 3, 433-445,
2012
Bobrowski, N., R. von Glasow, A. Aiuppa, S. Inguaggiato, I. Louban, O. W. Ibrahim and
U. Platt: Reactive halogen chemistry in volcanic plumes. J. Geophys. Res., 112,
2007
Donovan A., V. Tsanev, C. Oppenheimer and M. Edmonds: Reactive halogens (BrO and
OClO) detected in the plume of Soufrière Hills Volcano during an eruption hiatus. Geochem.
Geophys. Geosyst., 15, 3346-3363, 2014
Huang, R.-J. and T. Hoffmann: A denuder-impinger system with in situ derivatization
followed by gas chromatography-mass spectrometry for the determination of gaseous
iodine-containing halogen species. Journal of Chromatography A, 1210, 135-141, 2008 |
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