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
Open Access
- 27 February 2008
- journal article
- Published by Copernicus GmbH in Atmospheric Chemistry and Physics
- Vol. 8 (4), 1087-1103
- https://doi.org/10.5194/acp-8-1087-2008
Abstract
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.Keywords
This publication has 28 references indexed in Scilit:
- Effects of uncertainties in the thermodynamic properties of aerosol components in an air quality model – Part 1: Treatment of inorganic electrolytes and organic compounds in the condensed phaseAtmospheric Chemistry and Physics, 2008
- Vapor pressure prediction for alkenoic and aromatic organic compounds by a UNIFAC-based group contribution methodAtmospheric Environment, 2006
- Assessment of vapor pressure estimation methods for secondary organic aerosol modelingAtmospheric Environment, 2006
- Thermodynamic Models of Aqueous Solutions Containing Inorganic Electrolytes and Dicarboxylic Acids at 298.15 K. 2. Systems Including Dissociation EquilibriaThe Journal of Physical Chemistry A, 2006
- A new method for the estimation of the normal boiling point of non-electrolyte organic compoundsFluid Phase Equilibria, 2002
- Estimating the vapor pressures of multi-functional oxygen-containing organic compounds using group contribution methodsAtmospheric Environment, 2002
- Air Quality Model Evaluation Data for Organics. 5. C6−C22 Nonpolar and Semipolar Aromatic CompoundsEnvironmental Science & Technology, 1998
- Air Quality Model Evaluation Data for Organics. 4. C2−C36 Non-Aromatic HydrocarbonsEnvironmental Science & Technology, 1997
- New group contribution method for estimating properties of pure compoundsAIChE Journal, 1994
- Modified Joback group contribution method for normal boiling point of aliphatic halogenated compoundsIndustrial & Engineering Chemistry Research, 1992