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| Titel |
Reactivity of stabilized Criegee intermediates (sCIs) from isoprene and monoterpene ozonolysis toward SO2 and organic acids |
| VerfasserIn |
M. Sipilä, T. Jokinen, T. Berndt, S. Richters, R. Makkonen, N. M. Donahue, R. L. Mauldin III, T. Kurtén, P. Paasonen, N. Sarnela, M. Ehn, H. Junninen, M. P. Rissanen, J. Thornton, F. Stratmann, H. Herrmann, D. R. Worsnop, M. Kulmala  , V.-M. Kerminen, T. Petäjä |
| 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 ; 14, no. 22 ; Nr. 14, no. 22 (2014-11-19), S.12143-12153 |
| Datensatznummer |
250119170
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| Publikation (Nr.) |
 copernicus.org/acp-14-12143-2014.pdf |
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| Zusammenfassung |
| Oxidation processes in Earth's atmosphere are tightly connected to many
environmental and human health issues and are essential drivers for
biogeochemistry. Until the recent discovery of the atmospheric relevance of
the reaction of stabilized Criegee intermediates (sCIs) with SO2,
atmospheric oxidation processes were thought to be dominated by a few main
oxidants: ozone, hydroxyl radicals (OH), nitrate radicals and, e.g. over
oceans, halogen atoms such as chlorine. Here, we report results from
laboratory experiments at 293 K and atmospheric pressure focusing on sCI
formation from the ozonolysis of isoprene and the most abundant monoterpenes
(α-pinene and limonene), and subsequent reactions of the resulting
sCIs with SO2 producing sulfuric acid (H2SO4). The measured
total sCI yields were (0.15 ± 0.07), (0.27 ± 0.12) and
(0.58 ± 0.26) for α-pinene, limonene and isoprene, respectively.
The ratio between the rate coefficient for the sCI loss (including thermal
decomposition and the reaction with water vapour) and the rate coefficient
for the reaction of sCI with SO2,
k(loss) /k(sCI + SO2), was determined at relative
humidities of 10 and 50%. Observed values represent the average
reactivity of all sCIs produced from the individual alkene used in the
ozonolysis. For the monoterpene-derived sCIs, the relative rate coefficients
k(loss) / k(sCI + SO2) were in the range
(2.0–2.4) × 1012 molecules cm−3 and nearly independent
of the relative humidity. This fact points to a minor importance of the
sCI + H2O reaction in the case of the sCI arising from
α-pinene and limonene. For the isoprene sCIs, however, the ratio
k(loss) / k(sCI + SO2) was strongly dependent on the
relative humidity. To explore whether sCIs could have a more general role in
atmospheric oxidation, we investigated as an example the reactivity of
acetone oxide (sCI from the ozonolysis of 2,3-dimethyl-2-butene) toward small
organic acids, i.e. formic and acetic acid. Acetone oxide was found to react
faster with the organic acids than with SO2;
k(sCI + acid) / k(sCI + SO2) = (2.8 ± 0.3) for
formic acid, and k(sCI + acid) / k(sCI + SO2) = (3.4 ± 0.2) for
acetic acid. This finding indicates that sCIs can play a role in the
formation and loss of other atmospheric constituents besides SO2. |
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