 |
| Titel |
Tropospheric photooxidation of CF3CH2CHO and CF3(CH2)2CHO initiated by Cl atoms and OH radicals |
| VerfasserIn |
M. Antiñolo, E. Jimenez, A. Notario, E. Martínez, J. Albaladejo |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 4 ; Nr. 10, no. 4 (2010-02-19), S.1911-1922 |
| Datensatznummer |
250008124
|
| Publikation (Nr.) |
 copernicus.org/acp-10-1911-2010.pdf |
|
|
|
|
|
| Zusammenfassung |
The absolute rate coefficients for the tropospheric reactions of chlorine
(Cl) atoms and hydroxyl (OH) radicals with CF3CH2CHO and
CF3(CH2)2CHO were measured as a function of temperature
(263–371 K) and pressure (50–215 Torr of He) by pulsed UV laser
photolysis techniques. Vacuum UV resonance fluorescence was employed to
detect and monitor the time evolution of Cl atoms. Laser induced
fluorescence was used in this work for the detection of OH radicals as a
function of reaction time. No pressure dependence of the bimolecular rate
coefficients, kCl and kOH, was found at all temperatures. At room
temperature kCl and kOH were (in 10−11 cm3
molecule−1 s−1):
kCl(CF3CH2CHO) = (1.55±0.53);
kCl(CF3(CH2)2CHO) = (3.39±1.38);
kCl(CF3CH2CHO) = (0.259±0.050);
kCl(CF3(CH2)2CHO) = (1.28±0.24). A slightly
positive temperature dependence of kCl was observed for
CF3CH2CHO and CF3(CH2)2CHO, and
kOH(CF3CH2CHO). In contrast,
kOH(CF3(CH2)2CHO) did not exhibit a temperature
dependence over the range investigated. Arrhenius expressions for these
reactions were:
kCl(CF3CH2CHO) = (4.4±1.0)×10−11
exp{−(316±68)/T} cm3 molecule−1 s−1
kCl(CF3(CH2)2CHO) = (2.9±0.7)×10−10
exp{−(625±80)/T} cm3 molecule−1 s−1
kOH(CF3CH2CHO) = (7.8±2.2)×10−12
exp{−(314±90)/T} cm3 molecule−1 s−1
The atmospheric impact of the homogeneous removal by OH radicals and Cl
atoms of these fluorinated aldehydes is discussed in terms of the global
atmospheric lifetimes, taking into account different degradation pathways.
The calculated lifetimes show that atmospheric oxidation of
CF3(CH2)x CHO are globally dominated by OH radicals, however
reactions initiated by Cl atoms can act as a source of free radicals at dawn
in the troposphere. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|