 |
| Titel |
New insights into the degradation of terpenoids with OH: a study of the OH budget in the atmosphere simulation chamber SAPHIR |
| VerfasserIn |
Martin Kaminski, Hendrik Fuchs, Ismail-Hakki Acir, Birger Bohn, Theo Brauers, Hans-Peter Dorn, Rolf Häseler, Andreas Hofzumahaus, Xin Li, Anna Lutz, Sascha Nehr, Franz Rohrer, Ralf Tillmann, Robert Wegener, Astrid Kiendler-Scharr, Andreas Wahner |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094094
|
| Publikation (Nr.) |
 EGU/EGU2014-9465.pdf |
|
|
|
|
|
| Zusammenfassung |
| The hydroxyl radical (OH) is the main oxidation agent in the atmosphere during daytime.
Recent field campaigns studying the radical chemistry in forested areas showed large
discrepancies between measured and modeled OH concentration at low NOx conditions and
when OH reactivity was dominated by VOC. These observations were only partially
explained by the evidence for new efficient hydroxyl radical regeneration pathways in the
isoprene oxidation mechanism. The question arises if other reactive VOCs with high global
emission rates are also capable of additional OH recycling. Beside isoprene, monoterpenes
and 2-methyl-3-buten-2-ol (MBO) are the volatile organic compounds (VOC) with the
highest global emission rates. Due to their high reactivity towards OH monoterpenes and
MBO can dominate the radical chemistry of the atmosphere in forested areas under certain
conditions.
In the present study the photochemical degradation mechanism of α-pinene, β-pinene,
limonene, myrcene and MBO was investigated in the Jülich atmosphere simulation chamber
SAPHIR. The focus of this study was in particular on the investigation of the OH budget in
the degradation process.
The photochemical degradation of these terpenoids was studied in a dedicated series of
experiments in the years 2012 and 2013. The SAPHIR chamber was equipped with
instrumentation to measure radicals (OH, HO2, RO2), the total OH reactivity, all important
OH precursors (O3, HONO, HCHO), the parent VOC, its main oxidation products and
photolysis frequencies to investigate the radical budget in the SAPHIR chamber. All
experiments were carried out under low NOx conditions (-¤ 2ppb) and atmospheric
terpenoid concentrations (-¤ 5ppb) with and without addition of ozone into the SAPHIR
chamber.
For the investigation of the OH budget all measured OH production terms were compared
to the measured OH destruction. Within the limits of accuracy of the instruments the
OH budget was balanced in all cases. Consequently unaccounted OH recycling
or primary OH production processes did not play a role for conditions of these
experiments.
Despite the OH budget was closed in these experiments simulation results from the
Master Chemical Mechanism v3.2 showed that the OH production was underestimated by the
model in the α-pinene, β-pinene and limonene experiments. The measured OH destruction
was overestimated by the numerical simulation. |
|
|
|
|
|
|