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| Titel |
Extension of the CAPRAM mechanism with the improved mechanism generator GECKO-A |
| VerfasserIn |
Peter Brauer, Camille Mouchel-Vallon, Andreas Tilgner, Ralf Wolke, Bernard Aumont, Hartmut Herrmann |
| 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 |
250075261
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| Zusammenfassung |
| Organic compounds are an ubiquitous constituent of the tropospheric multiphase system.
With either biogenic or anthropogenic sources, they have a major influence on the
atmospheric multiphase system and thus have become a main research topic within the last
decades.
Modelling can provide a useful tool to explore the tropospheric multiphase chemistry.
While in the gas phase several comprehensive near-explicit mechanisms exist, in the aqueous
phase those mechanisms are very limited. The current study aims to advance the currently
most comprehensive aqueous phase mechanism CAPRAM 3.0 by means of automated
mechanism construction. Therefore, the mechanism generator GECKO-A (Generator for
Explicit Chemistry and Kinetics of Organics in the Atmosphere; see Aumont et al., 2005) has
been advanced to the aqueous phase. A protocol has been designed for automated mechanism
construction based on reviewed experimental data and evaluated prediction methods. The
generator is able to describe the oxidation of aliphatic organic compounds by OH and
NO3. For the mechanism construction, mainly structure-activity relationships are
used, which are completed by Evans-Polanyi-type correlations and further suitable
estimates.
GECKO-A has been used to create new CAPRAM versions, where branching ratios are
introduced and new chemical subsystems with species with up to 4 carbon atoms are added.
The currently most comprehensive version, CAPRAMÂ 3.7, includes about 2000 aqueous
phase species and more than 3300 reactions in the aqueous phase. Box model studies have
been performed using a meteorological scenario with non-permanent clouds. Besides the
investigation of the concentration-time profiles, detailed time-resolved flux analyses have
been performed. Several aqueous phase subsystems have been investigated, such
as the formation of oxidised mono- and diacids in the aqueous phase, as well as
interactions to inorganic cycles and the influence on the gas phase chemistry and
composition. Results have been compared to results of previous versions and show
a significant improvement in the new mechanism versions, when comparing the
modelled data to field data from literature. For example, in CAPRAMÂ 3.7 there is
a malonic acid production of about 80 ng m-3 compared to a few ng m-3 in
CAPRAMÂ 3.0. The results in CAPRAMÂ 3.7 confirm recent measurements by Bao
et al. (2012), who measure up to 137 ng m-3. Moreover, several attempts have
been undertaken to validate the mechanisms created by GECKO-A with own field
experiments, such as the HCCT-2010 campaign and chamber experiments in the LEAK
chamber.
References
Aumont, B., Szopa, S., Madronich, S.: Modelling the evolution of organic carbon during its
gas-phase tropospheric oxidation: development of an explicit model based on a self
generating approach. Atmos. Chem. Phys., 5, 2497-2517 (2005).
Bao, L., Matsumoto, M., Kubota, T., Sekiguchi, K., Wang, Q., Sakamoto, K.: Gas/particle
partitioning of low-molecular-weight dicarboxylic acids at a suburban site in Saitama, Japan.
Atmos. Env., 47, 546 - 553 (2012). |
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