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| Titel |
Unexpected autumnal halogen activity in the lower troposphere at Neumayer III/Antarctica |
| VerfasserIn |
Jan-Marcus Nasse, Udo Frieß, Denis Pöhler, Stefan Schmitt, Rolf Weller, Thomas Schaefer, Ulrich Platt |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250140492
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| Publikation (Nr.) |
 EGU/EGU2017-3888.pdf |
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| Zusammenfassung |
| The influence of Reactive Halogen Species (RHS, like IO, BrO, ClO, etc.) on the lower
polar troposphere has been subject of intense research for several decades. Ozone
Depletion Events (ODEs) caused by the catalytic reaction of tropospheric ozone with
inorganic halogen species or the oxidation of gaseous elemental mercury are well
observed phenomena that occur during the respective springtime in both Arctic and
Antarctica.
Chlorine atoms also react more efficiently with hydrocarbons than e.g. OH radicals and
all reactive halogen species can furthermore influence the atmospheric sulphur or nitrate
cycles. While an autocatalytic release mechanism from salty surfaces, the so called
bromine explosion, has been identified to rapidly increase inorganic bromine mixing
ratios many aspects of atmospheric halogen chemistry in polar regions remains
unclear.
Since January 2016, we are operating an active Long Path DOAS instrument at Neumayer
III on the Antarctic Ekström shelf ice designed for autonomous measurements. This
instrument is able to detect a wide range of trace gases absorbing in the UV/Vis including
ClO, BrO, OClO, IO, I2, OIO, ozone, NO2, H2O, O4, and SO2 at a temporal resolution of
5-30 minutes.
The analysis of the first year of observations shows several surprising findings
which give new insights into polar halogen chemistry. E.g. we observe surprisingly
strong bromine activity in late summer and autumn (in addition to well-known
springtime events) with mixing ratios often higher than 20 pptv. We could even observe
peak mixing ratios of 110 pptv. The observed BrO levels could be the result of
local/regional chemistry rather than long-range transport and modulated by the stability
of the boundary layer. Also, there are hints for NOx - driven halogen activation.
Furthermore, chlorine monoxide (ClO) and OClO mixing ratios of several ten pptv
could be detected on a number of days, however the source mechanism for reactive
chlorine remains unclear. We will give an overview of the entire time series and
discuss interesting case studies with regard to chemistry, atmospheric conditions and
transport. |
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