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| Titel |
The Secondary Organic Aerosol Processor (SOAP v1.0) model: a unified model with different ranges of complexity based on the molecular surrogate approach |
| VerfasserIn |
F. Couvidat, K. Sartelet |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 8, no. 4 ; Nr. 8, no. 4 (2015-04-22), S.1111-1138 |
| Datensatznummer |
250116281
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| Publikation (Nr.) |
 copernicus.org/gmd-8-1111-2015.pdf |
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| Zusammenfassung |
In this paper the Secondary Organic Aerosol Processor (SOAP v1.0) model is presented. This
model determines the partitioning of organic compounds between the gas and
particle phases. It is designed to be modular with different user options
depending on the computation time and the complexity required by the user.
This model is based on the molecular surrogate approach, in which each
surrogate compound is associated with a molecular structure to estimate some
properties and parameters (hygroscopicity, absorption into the aqueous phase
of particles, activity coefficients and phase separation).
Each surrogate can be hydrophilic (condenses only into the aqueous
phase of particles), hydrophobic (condenses only into the organic phases of
particles) or both (condenses into both the aqueous and the organic phases of
particles). Activity coefficients are computed with the UNIFAC (UNIversal Functional group Activity
Coefficient;
Fredenslund
et al., 1975) thermodynamic
model for short-range interactions and with the Aerosol Inorganic–Organic Mixtures
Functional groups Activity Coefficients (AIOMFAC) parameterization for
medium- and long-range interactions between electrolytes and organic
compounds. Phase separation is determined by Gibbs energy minimization.
The user can choose between an equilibrium representation and a dynamic
representation of organic aerosols (OAs). In the equilibrium
representation, compounds in the particle phase are assumed to be at
equilibrium with the gas phase. However, recent studies show that the organic
aerosol is not at equilibrium with the gas phase because the organic phases
could be semi-solid (very viscous liquid phase). The condensation–evaporation
of organic compounds could then be limited by the diffusion in the organic
phases due to the high viscosity. An implicit dynamic representation of
secondary organic aerosols (SOAs) is available in SOAP with OAs divided into
layers, the first layer being at the center of the particle (slowly reaches
equilibrium) and the final layer being near the interface with the gas phase
(quickly reaches equilibrium). Although this dynamic implicit representation
is a simplified approach to model condensation–evaporation with a low number
of layers and short CPU (central processing unit) time, it shows good agreements with an explicit
representation of condensation–evaporation (no significant differences after
a few hours of condensation). |
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