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| Titel |
Influence of relative humidity and temperature on the production of pinonaldehyde and OH radicals from the ozonolysis of α-pinene |
| VerfasserIn |
R. Tillmann, M. Hallquist, A. M. Jönsson, A. Kiendler-Scharr, H. Saathoff, Y. Iinuma, Th. F. Mentel |
| 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 ; 10, no. 15 ; Nr. 10, no. 15 (2010-08-03), S.7057-7072 |
| Datensatznummer |
250008670
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| Publikation (Nr.) |
 copernicus.org/acp-10-7057-2010.pdf |
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| Zusammenfassung |
The ozonolysis of α-pinene has been investigated under dry and humid
conditions in the temperature range of 243–303 K. The results provided new
insight into the role of water and temperature in the degradation mechanism
of α-pinene and in the formation of secondary organic aerosols
(SOA). The SOA yields were higher at humid conditions than at dry
conditions. The water induced gain was largest for the lowest temperatures
investigated (243 and 253 K). The increase in the SOA yields was dominated
by water (and temperature) effects on the organic product distribution,
whilst physical uptake of water was negligible. This will be demonstrated
for the example of pinonaldehyde (PA) which was formed as a major product in
the humid experiments with total molar yields of 0.30±0.06 at 303 K
and 0.15±0.03 at 243 K. In the dry experiments the molar yields of PA
were only 0.07±0.02 at 303 K and 0.02±0.02 at 253 K. The
observed partitioning of PA as a function of the SOA mass present at 303 K
limited the effective vapour pressure of pure PA pPA0 to the range
of 0.01–0.001 Pa, 3–4 orders of magnitude lower than literature values.
The corresponding mass partitioning coefficient was determined to
KPA=0.005±0.004 m3 μg−1 and the total mass yield
αPAtotal=0.37±0.08. At 303 K PA preferably stayed in
the gas-phase, whereas at 253 K and 243 K it exclusively partitioned into
the particulate phase. PA could thus account at least for half of the water
induced gain in SOA mass at 253 K. The corresponding effect was negligible
at 303 K because the PA preferably remained in the gas-phase.
The yield of OH radicals, which were produced in the ozonolysis, was
indirectly determined by means of the yield of cyclohexanone formed in the
reaction of OH radicals with cyclohexane. OH yields of the α-pinene
ozonolysis were determined to 0.67±0.17 for humid and 0.54±0.13
for dry conditions at 303 K, indicating a water dependent path of OH
radical formation. For 253 and 243 K OH yields could be estimated to 0.5
with no significant difference between the dry and humid experiments. This
is the first clear indication for OH radical formation by α-pinene
ozonolysis at such low temperatures. |
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