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| Titel |
New insight into halogen release from experimental studies on BrO/Br ratios in volcanic plumes |
| VerfasserIn |
Nicole Bobrowski, Julian Wittmer, Marcello Liotta, Sergio Calabrese, Giovanni Giuffrida, Lorenzo Brusca, Ulrich Platt |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250095323
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| Publikation (Nr.) |
 EGU/EGU2014-10771.pdf |
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| Zusammenfassung |
| Since the discovery of BrO in a volcanic plume (Bobrowski et al. 2003) many measurements
have been performed as well as modelling to understand the radical chemistry in volcanic
plumes, in particular, the interaction between volcanic gas species, released under strongly
reduced conditions, and the oxidizing atmosphere. Besides the goal in atmospheric chemistry
to better determine the impact of volcanic emission (e.g. reactive bromine) on the local (and
maybe global) scale, volcanologists also have an interest to understand if the BrO/SO2 ratios
can be used as a monitoring parameter giving further insides in dynamic processes of
volcanoes. However, one of the arguments which potentially makes volcanological
interpretations difficult is the reactivity of BrO. Therefore it is, of great importance to link
the measurements of BrO and gaseous hydrogen bromide to the total emission
flux of bromine in order to estimate the pristine gas composition released from
magmas.
In particular, trace gas composition of the surrounding atmosphere, the volcanic gas
composition and meteorological parameters can all potentially effect the formation of BrO
and might have to be considered. Some of these factors potentially also influence
near source (crater rim) in-situ measurement. We need to answer the question: Can
we correlate BrO measurements to the total bromine outgassing? Only with this
knowledge we can relate changes of the measured gas ratios (BrO/SO2) to the
volcanic fluids emitted by the underlying magma and can interpret data as signals
from depth, which provide insight on the degassing of magmatic bodies inside the
Earth.
Some studies indicate that the BrO/SO2 ratio is close to a temporarily equilibrium already
after only few minutes of the gas emission from the vent (e.g. Bobrowski and Giuffrida,
2012). This equilibrium seems to be relatively independent from meteorological parameters
except for extreme conditions.
We here present an empirical approach to answer the above question by discussing BrO
formation studies from five different volcanoes, Stromboli and Etna (Italy), Masaya
(Nicaragua), Gorely (Russia) and Nyiragongo (DR Congo). These volcanoes represent a
broad variation in their geological settings, surrounding environment and climate. They cover
subduction related systems and rift volcanism and encompass climate zones from the
subarctic to the tropics.
For the BrO studies Multi-Axis-Differential Optical Absorption Spectroscopy
(MAX-DOAS) measurements have been carried out. Active alkaline traps were applied to
determine bromine emissions at the crater rim. All measurements have been taken
simultaneously or within a maximum time distance of a few hours. From these measurements
we determined that a range of about 5% to 30% of the total bromine is transformed into
BrO. We show and discuss how the varying BrO-Br partition is related partly to
the geological settings, the various meteorological conditions and explore further
possible influences. We will shortly discuss the current limitations of the commonly
used measurement techniques itself and introduce possible future improvements. |
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