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| Titel |
Evidence for a snowpack biological source of NOx and HONO to the Arctic boundary layer in Svalbard |
| VerfasserIn |
A. Amoroso, F. Domine, G. Esposito, S. Morin, M. Nardino, M. Montagnoli, J. Erbland, J. Savarino, H. Beine |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250022796
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| Zusammenfassung |
| Nitrogen oxides (NO + NO2) and HONO are among the most reactive species in the polar
boundary layer. About a decade ago, the discovery of photochemical production of NOx and
HONO in the polar snowpack forced us to consider the role of snowpack emissions to
understand the composition of the polar boundary layer. Here we present evidence that NOx
and HONO can be emitted by the snowpack to the polar boundary layer in the absence of
sunlight. NOx and HONO fluxes were measured at Ny Alesund, Svalbard (79∘N) from mid
February (no sunlight) to late April (24 h sunlight). Values were mostly positive (i.e. species
transferred from snow to atmosphere) and up to 800 and 120 nmol m-2 h-1, respectively,
with the highest values observed in the near absence of sunlight. Mineral ions in surface snow
were also analyzed continuously, and snow chemistry data led us to suspect that
bacteria were involved in those emissions. The measurements of nitrate isotopic data
(δ15N and Δ17O) confirmed that a large fraction of nitrate in most snow layers
was not of atmospheric origin, and our interpretation is that is was produced from
ammonium by nitrifying bacteria. NO2- is an intermediate in nitrification, and can
lead to NO emission by bacteria. NO can be rapidly oxidized to NO2 by ozone
in the snowpack. Physical release of HONO from NO2- by the snow also takes
place. We therefore suggest that microbial activity in cold snowpacks can lead to
the release of significant amounts of reactive species, and deserves consideration
in the understanding of polar boundary chemistry and of polar snow chemistry. |
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