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| Titel |
Light induced conversion of nitrogen dioxide into nitrous acid on submicron humic acid aerosol |
| VerfasserIn |
K. Stemmler, M. Ndour, Y. Elshorbany, J. Kleffmann, B. D'Anna, C. George, B. Bohn, M. Ammann |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 7, no. 16 ; Nr. 7, no. 16 (2007-08-20), S.4237-4248 |
| Datensatznummer |
250005165
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| Publikation (Nr.) |
 copernicus.org/acp-7-4237-2007.pdf |
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| Zusammenfassung |
| The interactions of aerosols consisting of humic acids with gaseous nitrogen
dioxide (NO2) were investigated under different light conditions in
aerosol flow tube experiments at ambient pressure and temperature. The
results show that NO2 is converted on the humic acid aerosol into
nitrous acid (HONO), which is released from the aerosol and can be detected
in the gas phase at the reactor exit. The formation of HONO on the humic
acid aerosol is strongly activated by light: In the dark, the HONO-formation
was below the detection limit, but it was increasing with the intensity of
the irradiation with visible light. Under simulated atmospheric conditions
with respect to the actinic flux, relative humidity and
NO2-concentration, reactive uptake coefficients γrxn for the
NO2→HONO conversion on the aerosol between γrxn
<10−7 (in the dark) and γrxn=6×10−6 were observed.
The observed uptake coefficients decreased with increasing
NO2-concentration in the range from 2.7 to 280 ppb and were dependent
on the relative humidity (RH) with slightly reduced values at low humidity
(<20% RH) and high humidity (>60% RH). The measured uptake
coefficients for the NO2→HONO conversion are too low to
explain the HONO-formation rates observed near the ground in rural and urban
environments by the conversion of NO2→HONO on organic
aerosol surfaces, even if one would assume that all aerosols consist of
humic acid only. It is concluded that the processes leading to HONO formation on the Earth
surface will have a much larger impact on the HONO-formation in the
lowermost layer of the troposphere than humic materials potentially
occurring in airborne particles. |
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