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| Titel |
Investigation of Monoterpene Degradation in the Atmospheric Simulation Chamber SAPHIR |
| VerfasserIn |
Martin Kaminski, Ismail-Hakki Acir, Birger Bohn, Theo Brauers, Hans-Peter Dorn, Hendrik Fuchs, Rolf Haeseler, Andreas Hofzumahaus, Xin Li, Anna Lutz, Sascha Nehr, Franz Rohrer, Ralf Tillmann, Robert Wegener, Andreas Wahner |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250076768
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| Zusammenfassung |
| Monoterpenes are the volatile organic compound (VOC) species with the highest emission
rates on a global scale beside isoprene. In the atmosphere these compounds are rapidly
oxidized. Due to their high reactivity towards hydroxyl radicals (OH) they determine the
radical chemistry under biogenic conditions if monoterpene concentration is higher than
isoprene concentration. Recent field campaigns showed large discrepancies between
measured and modeled OH concentration at low NOx conditions together with high reactivity
of VOC towards OH (Hofzumahaus et al. 2009) especially in tropical forest areas (Lelieveld
et al. 2008). These discrepancies were partly explained by new reaction pathways in the
isoprene degradation mechanism (Whalley et al 2011). However, even an additional
recycling rate of 2.7 was insufficient to explain the measured OH concentration. So
other VOC species could be involved in a nonclassical OH recycling. Since the
discrepancies in OH also occurred in the morning hours when the OH chemistry
was mainly dominated by monoterpenes, it was assumed that also the degradation
of monoterpenes may lead to OH recycling in the absence of NO. (Whalley et al
2011).
The photochemical degradation of four monoterpene species was studied under high VOC
reactivity and low NOx conditions in a dedicated series of experiments in the atmospheric
simulation chamber SAPHIR from August to September 2012 to overcome the lack of
mechanistic information for monoterpene degradation schemes. α-Pinene, β-pinene and
limonene were chosen as most prominent representatives of this substance class.
Moreover the degradation of myrcene was investigated due to its structural analogy to
isoprene.
The SAPHIR chamber was equipped with instrumentation to measure all important OH
precursors (O3, HONO, HCHO), the parent VOC and their main oxidation products,
radicals (OH, HO2, RO2), the total OH reactivity, and photolysis frequencies to
investigate the degradation mechanism of monoterpenes in the SAPHIR chamber. All
experiments were carried out under low NOx conditions (-¤ 2ppb) and atmospheric
terpene concentrations (-¤ 5ppb) with and without addition of ozone into the SAPHIR
chamber. The measured temporal profiles of key constituents were compared to
model simulations of the experiments using the Master Chemical Mechanism v3.2. |
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