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| Titel |
Evaluation of the volatility basis-set approach for the simulation of organic aerosol formation in the Mexico City metropolitan area |
| VerfasserIn |
A. P. Tsimpidi, V. A. Karydis, M. Zavala, W. Lei, L. Molina, I. M. Ulbrich, J. L. Jimenez, S. N. Pandis |
| 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. 2 ; Nr. 10, no. 2 (2010-01-20), S.525-546 |
| Datensatznummer |
250007959
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| Publikation (Nr.) |
 copernicus.org/acp-10-525-2010.pdf |
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| Zusammenfassung |
| New primary and secondary organic aerosol modules have been added to
PMCAMx, a three dimensional chemical transport model (CTM), for use
with the SAPRC99 chemistry mechanism based on recent smog chamber
studies. The new modelling framework is based on the volatility
basis-set approach: both primary and secondary organic components
are assumed to be semivolatile and photochemically reactive and are
distributed in logarithmically spaced volatility bins. This new
framework with the use of the new volatility basis parameters for
low-NOx and high-NOx conditions tends to predict 4–6 times higher
anthropogenic SOA concentrations than those predicted with the older
generation of models. The resulting PMCAMx-2008 was applied in
Mexico City Metropolitan Area (MCMA) for approximately a week during
April 2003 during a period of very low regional biomass burning
impact. The emission inventory, which uses as a starting point the
MCMA 2004 official inventory, is modified and the primary organic
aerosol (POA) emissions are distributed by volatility based on
dilution experiments. The predicted organic aerosol (OA)
concentrations peak in the center of Mexico City, reaching values
above 40 μg m−3. The model predictions are compared with
the results of the Positive Matrix Factorization (PMF) analysis of
the Aerosol Mass Spectrometry (AMS) observations. The model
reproduces both Hydrocarbon-like Organic Aerosol (HOA) and
Oxygenated Organic Aerosol (OOA) concentrations and diurnal
profiles. The small OA underprediction during the rush-hour periods
and overprediction in the afternoon suggest potential improvements
to the description of fresh primary organic emissions and the
formation of the oxygenated organic aerosols, respectively, although
they may also be due to errors in the simulation of dispersion and
vertical mixing. However, the AMS OOA data are not specific enough
to prove that the model reproduces the organic aerosol observations
for the right reasons. Other combinations of contributions of
primary and secondary organic aerosol production rates may lead to
similar results. The model results strongly suggest that, during
the simulated period, transport of OA from outside the city was a
significant contributor to the observed OA levels. Future
simulations should use a larger domain in order to test whether the
regional OA can be predicted with current SOA parameterizations.
Sensitivity tests indicate that the predicted OA concentration is
especially sensitive to the volatility distribution of the emissions
in the lower volatility bins. |
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