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| Titel |
Effects of uncertainties in the thermodynamic properties of aerosol components in an air quality model – Part 2: Predictions of the vapour pressures of organic compounds |
| VerfasserIn |
S. L. Clegg, M. J. Kleeman, R. J. Griffin, J. H. Seinfeld |
| 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 ; 8, no. 4 ; Nr. 8, no. 4 (2008-02-27), S.1087-1103 |
| Datensatznummer |
250005684
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| Publikation (Nr.) |
 copernicus.org/acp-8-1087-2008.pdf |
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| Zusammenfassung |
| Air quality models that generate the concentrations of semi-volatile and
other condensable organic compounds using an explicit reaction mechanism
require estimates of the vapour pressures of the organic compounds that
partition between the aerosol and gas phases. The model of Griffin, Kleeman
and co-workers (e.g., Griffin et al., 2005)
assumes that aerosol particles consist of an aqueous phase, containing
inorganic electrolytes and soluble organic compounds, and a hydrophobic
phase containing mainly primary hydrocarbon material. Thirty eight
semi-volatile reaction products are grouped into ten surrogate species. In
Part 1 of this work (Clegg et al., 2008) the thermodynamic elements of the
gas/aerosol partitioning calculation are examined, and the effects of
uncertainties and approximations assessed, using a simulation for the South
Coast Air Basin around Los Angeles as an example. Here we compare several
different methods of predicting vapour pressures of organic compounds, and
use the results to determine the likely uncertainties in the vapour
pressures of the semi-volatile surrogate species in the model. These are
typically an order of magnitude or greater, and are further increased when
the fact that each compound represents a range of reaction products (for
which vapour pressures can be independently estimated) is taken into
account. The effects of the vapour pressure uncertainties associated with
the water-soluble semi-volatile species are determined over a wide range of
atmospheric liquid water contents. The vapour pressures of the eight primary
hydrocarbon surrogate species present in the model, which are normally
assumed to be involatile, are also predicted. The results suggest that they
have vapour pressures high enough to exist in both the aerosol and gas
phases under typical atmospheric conditions. |
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