 |
| Titel |
Bromine monoxide / sulphur dioxide ratios in relation to volcanological observations at Mt. Etna 2006–2009 |
| VerfasserIn |
N. Bobrowski, G. Giuffrida |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1869-9510
|
| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 3, no. 2 ; Nr. 3, no. 2 (2012-12-04), S.433-445 |
| Datensatznummer |
250000999
|
| Publikation (Nr.) |
 copernicus.org/se-3-433-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
Over a 3-yr period, from 2006 to 2009, frequent scattered sunlight
DOAS measurements were conducted at Mt. Etna at a distance of around 6 km
downwind from the summit craters. During the same period and in
addition to these measurements, volcanic observations were made by regularly
visiting various parts of Mt. Etna.
Here, results from these measurements and observations are presented and
their relation is discussed. The focus of the investigation is the bromine
monoxide/sulphur dioxide (BrO / SO2) ratio, and its variability in
relation to volcanic processes.
That the halogen/sulphur ratio can serve as a precursor or indicator for the
onset of eruptive activity was already proposed by earlier works (e.g.
Noguchi and Kamiya 1963; Menyailov, 1975; Pennisi and Cloarec, 1998; Aiuppa
et al., 2002). However, there is still a limited understanding today because of the
complexity with which halogens are released, depending on magma composition
and degassing conditions. Our understanding of these processes is far from
complete, for example of the rate and mechanism of bubble nucleation, growth
and ascent in silicate melts (Carroll and Holloway, 1994), the halogen
vapour-melt partitioning and the volatile diffusivity in the melt (Aiuppa et
al., 2009).
With this study we aim to add one more piece to the puzzle of what
halogen/sulphur ratios might tell about volcanic activities. Our data set
shows an increase of the BrO / SO2 ratio several weeks prior to an
eruption, followed by a decline before and during the initial phase of
eruptive activities. Towards the end of activity or shortly thereafter, the
ratio increases to baseline values again and remains more or less constant
during quiet phases. To explain the observed evolution of the BrO / SO2
ratio, a first empirical model is proposed. This model suggests that
bromine, unlike chlorine and fluorine, is less soluble in the magmatic melt
than sulphur.
By using the DOAS method to determine SO2, we actually observe most of
the emitted sulphur of Mt.~Etna. Regarding bromine, however, we are aware that
by determining only the bromine monoxide (BrO) radical we might just observe
a small or even a variable fraction of the total emitted bromine, which is
most probable originally in the form of HBr. Therefore, we present first
studies to justify the assumption that, despite the disadvantage just
mentioned, the BrO / SO2 ratio can nevertheless serve as a new parameter
to indicate the state of a volcano, when measurements are conducted under
certain, but rather convenient, conditions. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|