 |
| Titel |
Does acetone react with HO2 in the upper-troposphere? |
| VerfasserIn |
T. J. Dillon, A. Pozzer, L. Vereecken, J. N. Crowley, J. Lelieveld  |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 3 ; Nr. 12, no. 3 (2012-02-02), S.1339-1351 |
| Datensatznummer |
250010633
|
| Publikation (Nr.) |
 copernicus.org/acp-12-1339-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
Recent theoretical calculations showed that reaction with HO2 could be
an important sink for acetone (CH3C(O)CH3) and source of acetic
acid (CH3C(O)OH) in cold parts of the atmosphere (e.g. the tropopause
region). This work details studies of HO2 + CH3C(O)CH3
(CH3)2C(OH)OO (R1) in laboratory-based and theoretical
chemistry experiments; the atmospheric significance of Reaction (R1) was assessed in a
global 3-D chemical model. Pulsed laser-kinetic experiments were conducted,
for the first time, at the low-temperatures representative of the
tropopause. Reaction with NO converted HO2 to OH for detection by laser
induced fluorescence. Reduced yields of OH at T < 220 K provided indirect
evidence for the sequestration of HO2 by CH3C(O)CH3 with a
forward rate coefficient greater than 2 × 10−12 cm3 molecule−1 s−1.
No evidence for Reaction (R1) was observed at T > 230 K,
probably due to rapid thermal dissociation back to HO2 +
CH3C(O)CH3. Numerical simulations of the data indicate that these
experiments were sensitive to only (R1a) HO2-CH3C(O)CH3
complex formation, the first step in (R1). Rearrangement (R1b) of the
complex to form peroxy radicals, and hence the atmospheric significance of
(R1) has yet to be rigorously verified by experiment.
Results from new quantum chemical calculations indicate that K1 is
characterised by large uncertainties of at least an order of magnitude at
T < 220 K. The large predicted values from Hermans et al. lie at the top
end of the range of values obtained from calculations at different (higher)
levels of theory. Atmospheric modelling studies demonstrated that whilst
(R1) chemistry may be a significant loss process for CH3C(O)CH3
near the tropopause, it cannot explain observations of CH3C(O)OH
throughout the troposphere. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|