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| Titel |
Anion-catalyzed Disprotionation of Nitrogen Dioxide on Microdroplets Surfaces |
| VerfasserIn |
M. R. Hoffmann, S. Enami, A. J. Colussi |
| 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 |
250029063
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| Zusammenfassung |
| The reactive dissolution of NO2(g) on cloud and fog droplets and the conversion to HONO(g)
: 2 NO2(g) + H2O(l) = HONO(g) + NO3-(aq) + H+(aq), is a viable transformation process.
Recently, unexpectedly large HONO concentrations were observed that may account for
~ 50 % of OH radical production at noon and entail a diurnal source ~ 64 times
stronger than the reaction above at night (Kleffmann, Chem. Phys. Chem. 2007,
8, 1137). Reported NO2(g) uptake coefficients in water are at odds in the range
from γg 10-7 up to 10-3. Here we show that the probability of NO2 uptake on
aqueous microdroplets depends on their ionic composition at the air/water interface,
reaching peak values at ion concentrations in the low mM range, using a novel
application of electrospray mass spectrometry. We found that the uptake rates under these
conditions are three orders of magnitude larger than in pure water. Uptake appears to be
controlled by the capture of NO2 into radical anion intermediates on droplet surfaces,
and is modulated by overall anion concentration. These results would resolve the
outstanding discrepancies between previous NO2 uptake measurements in water vs.
NaCl-seeded clouds, and lead to half-lives for the reactive dissolution of NO2 in typical
clouds and fogs that are sufficiently short to impact diurnal -
OH/HO2-
budgets. |
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