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| Titel |
Global modelling of secondary organic aerosol from α-pinene oxidation using a parameterization based on a detailed chemical mechanism |
| VerfasserIn |
Karl Ceulemans, Jean-Francois Müller, Steven Compernolle, Jenny Stavrakou |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250034576
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| Zusammenfassung |
| Monoterpenes are oxidized in the atmosphere by ozone and the hydroxyl and nitrate radicals.
The condensable products resulting from these reactions contribute to Secondary
Organic Aerosol (SOA). We have developed a detailed α-pinene chemical mechanism
BOREAM (Capouet et al. 2008), in which the primary gas phase chemistry is based on
quantum-chemical results, structure activity relationships and experimental data. The
secondary chemistry of the most important products is treated explicitly, while further
chemistry is reduced by the aid of generic species classes. The partitioning between gas phase
and SOA is modeled using Pankow’s partitioning approach (Pankow 1994), with vapor
pressures (Capouet and Müller 2006) and activity coefficients (Compernolle et al. 2009)
obtained from group contribution methods.
We will discuss the performance of BOREAM through comparison of model predictions
for SOA formation with experimental SOA yields for a large number (>150) of
photo-oxidation and dark ozonolysis experiments (Ceulemans et al. 2009). Although
the BOREAM SOA yields are significantly higher than in several previous box
modeling studies, a reasonable agreement is found in comparison with most laboratory
measurements.
For use in a global model, the detailed BOREAM chemistry is replaced by a parameterized
scheme based on the two-product approach (Odum et al. 1996) with parameters obtained
through regressions of full model simulations. The reduced scheme accounts for
the dependence of SOA yield on the oxidant (ozone, OH or NO3) and the NOx
regime. For example, the reaction of alpha-pinene with OH generates a peroxy
radical which, upon reaction with either NO or HO2 leads to the formation of two
condensable products. The branching ratios and partitioning coefficients are temperature
dependent.
We inserted the obtained parameterized scheme in the global model IMAGES, where it is
used to represent the SOA formation due to the monoterpenes. For aromatics, isoprene and
sesquiterpenes we use two-product parameterizations based on smog chamber studies.
Irreversible SOA formation due to polymerization of short-chained aldehydes (glyoxal,
methylglyoxal, etc.) and direct emission of POA are also considered. Monoterpenes are
estimated to contribute about 20-40 TgOA/year globally, i.e. a factor 2-4 higher than in
previous modeling studies. This large contribution stems from the high SOA yields (of the
order of 50% in atmospheric conditions) obtained using BOREAM at low NOx in the the
oxidation of α-pinene by OH. These high yields result from the predicted formation of highly
condensable polyfunctional compounds (e.g. hydroxy-dihydroperoxides). Possible
uncertainties on these estimates will be discussed on the basis of sensitivity tests with the full
mechanism.
The calculated OA concentrations are compared with a large number of ground-based
(IMPROVE, CARBOSOL, etc.) and aircraft (INTEX-A and ACE-1) measurements. Whereas
a relatively good agreement is found over both Eastern and Western US, large OA
underestimations are generally found over Europe, Africa and Asia. Possible causes will be
discussed.
Capouet, M. and J.-F. Müller, A group contribution method for estimating the
vapour pressures of α-pinene oxidation products, Atmos. Chem. Phys., 6, 1455-1467,
2006.
Capouet, M., J.-F. Müller, K. Ceulemans, S. Compernolle, L. Vereecken, J. Peeters, Modeling
aerosol formation in α-pinene photooxidation experiments, J. Geophys. Res., 113, D02308,
2008.
Ceulemans, K., S. Compernolle, J. Peeters, and J.-F. Müller, Evaluation of a detailed model
of secondary aerosol formation from α-pinene against dark ozonolysis experiments,
submitted to Atmos. Environ., 2009.
Compernolle, S., K. Ceulemans, and J.-F. Müller, Influence of non-ideality on aerosol
growth, Atmos. Chem. Phys., 9, 1325-1337, 2009.
Odum, J. R., T. Hoffmann, F. Bowman, D. Collins, R. C. Flagan, and J. H. Seinfeld,
Gas/particle partitioning and secondary organic aerosol AMFs, Environ. Sci. Technol., 30,
2580–2585., 1996.
Pankow, J. F., An absorption model of gas/particle partitioning of organic compounds in the
atmosphere, Atmos. Environ., 28, 185–188, 1994. |
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