download pdf - Institut für Umweltphysik - Ruprecht-Karls-Universität ...

2.1. TROPOSPHERIC RESEARCH GROUP 19
2.1.1 Halogen oxide and sulphur dioxide emission of volcanoes
Participating scientist Nicole Bobrowski
Abstract A novel instrument, the ’Mini-MAX-DOAS’ was applied to study reactive halogen and
sulphur emissions of several volcanoes. The study was focussed on the determination of SO2 and BrO
concentrations, but also ClO and OClO could be detected for the first time in a volcanic plume. The
chemistry of volcanic plumes can give insights into volcanic processes, which could help to improve the
forecast of volcanic eruptions and is also of atmospheric relevance as the volcanic source of aerosols
and trace gases can have significant climatic impact.
Figure 2.1: The BrO/SO2 ratios for the different distances from the summit (left panel). Sketch of
processes in a volcanic plume: after emission the plume mixes with ambient air, thus ozone becomes
available and radical chemistry starts (right panel).
Background The chemistry of volcanic plumes
can give insights into volcanic processes, which
could help improving the forecast of volcanic eruptions
and is also of atmospheric relevance as the
volcanic source of aerosols and trace gases can
have a significant climatic impact. Although both
are very important aspects until now the chemical
processes are hardly understood and unfortunately
still rarely studied.
Funding IMPRS Fellowship and DORSIVA
(Development of Optical Remote Sensing for Volcanic
Applications- EU-project)
Methods and results Spectroscopic measurements
were carried out with the new Mini-MAX-
DOAS instrument combined with a Pocket PC.
The main results obtained in this work are: BrO
is formed downwind, although it is not yet clear
by what chemical processes. Nevertheless a suggested
chemistry is given in Figure 1, right panel.
Experimental studies at two volcanic sites, Mt.
Etna and Mt. Villarica, were carried out and
showed similar results. At Mt. Etna, measurements
took place from the summit up to a distance
of 19 km in downwind direction (see Figure 2.1,
left panel). ClO and OClO were detected for the
first time as further active halogen compounds in
volcanic plumes. ClO was already detected next
to the source (in contrast to BrO), and shows no
significant increase in the ClO/SO2 ratio in the
aging plume. The ClO/SO2 ratio even seems to
decrease by measuring further downwind.
The BrO/SO2 variations were studied during and
after the Mt. Etna eruption 2004. They were
compared with filter pack measurements and SO2
flux variations. This measurements show differences
of the feeding systems of Mt. Etna (North
East Crater and Voragine). The North East
Crater showed larger BrO/SO2 ratios than Voragine.
Outlook/Future work The Mini-MAX-
DOAS system will be set-up at many volcanic
sites in the frame of a new started EU-project -
NOVAC. The extension of the data set will open
the possibility of a better estimation of the volcanic
reactive bromine source and also allows the
investigation of changes in the BrO/SO2 ratio
with volcanic activity.
Main publications [Bobrowski, 2005],
[Bobrowski & Filsinger, 2005],
[Bobrowski et al. , 2005]