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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 Phase : Volume 8, Issue 4 (27/02/2008)

By Clegg, S. L.

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Book Id: WPLBN0003975854
Format Type: PDF Article :
File Size: Pages 29
Reproduction Date: 2015

Title: 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 Phase : Volume 8, Issue 4 (27/02/2008)  
Author: Clegg, S. L.
Volume: Vol. 8, Issue 4
Language: English
Subject: Science, Atmospheric, Chemistry
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Historic
Publication Date:
2008
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

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Seinfeld, J. H., Griffin, R. J., Kleeman, M. J., & Clegg, S. L. (2008). 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 Phase : Volume 8, Issue 4 (27/02/2008). Retrieved from http://www.ebooklibrary.org/


Description
Description: School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK. Air quality models that generate the concentrations of semi-volatile and other condensable organic compounds using an explicit reaction mechanism require estimates of the physical and thermodynamic properties of the compounds that affect gas/aerosol partitioning: vapour pressure (as a subcooled liquid), and activity coefficients in the aerosol phase. The model of Griffin, Kleeman and co-workers (e.g., Griffin et al., 2003; Kleeman et al., 1999) 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 which partition between the gas phase and both phases in the aerosol. Activity coefficients of the organic compounds are calculated using UNIFAC. In a companion paper (Clegg et al., 2008) we examine the likely uncertainties in the vapour pressures of the semi-volatile compounds and their effects on partitioning over a range of atmospheric relative humidities. In this work a simulation for the South Coast Air Basin surrounding Los Angeles, using lower vapour pressures of the semi-volatile surrogate compounds consistent with estimated uncertainties in the boiling points on which they are based, yields a doubling of the predicted 24-h average secondary organic aerosol concentrations. The dependency of organic compound partitioning on the treatment of inorganic electrolytes in the air quality model, and the performance of this component of the model, are determined by analysing the results of a trajectory calculation using an extended version of the Aerosol Inorganics Model of Wexler and Clegg (2002). Simplifications are identified where substantial efficiency gains can be made, principally: the omission of dissociation of the organic acid surrogates; restriction of aerosol organic compounds to one of the two phases (aqueous or hydrophobic) where equilibrium calculations suggest partitioning strongly in either direction; a single calculation of activity coefficients of the organic compounds for simulations where they are determined by the presence of one component at high concentration in either phase (i.e., water in the aqueous phase, or a hydrocarbon surrogate compound P8 in the hydrophobic phase) and are therefore almost invariant. The implications of the results for the development of aerosol models are discussed.

Summary
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 phase

Excerpt
Bates, R. G. and Pinching, G. D.: Acidic dissociation constant of ammonium ion at 0° to 50°C, and the base strength of ammonia, J. Res. Nat. Bur. Standards, 42, 419–430, 1949.; Bian, F. and Bowman, F. M.: A lumping model for composition- and temperature-dependent partitioning of secondary organic aerosols, Atmos. Environ., 39, 1263–1274, 2005.; Carslaw, K. S., Clegg, S. L., and Brimblecombe, P.: A thermodynamic model of the system HCl-HNO3-H2SO4-H2O, including solubilities of HBr, from <200 K to 328 K, J. Phys. Chem., 99, 11 557–11 574, 1995.; Clegg, S. L. and Brimblecombe, P.: Solubility of ammonia in pure aqueous and multicomponent solutions, J. Phys. Chem., 93, 7237–7248, 1989.; Chen, J., Mao, H., Talbot, R. W., and Griffin, R. J.: Application of the CACM and MPMPO modules using the CMAQ model for the Eastern United States, J. Geophys. Res., 111, D23S25, doi:10.1029/2006JD007603, 2006.; Clegg, S. L.: Extension of the Aerosol Inorganics Model to include organic compounds with user-defined properties, Report to U.S. EPA, Research Triangle Park, North Carolina, Requisition Reference No. U2D604, QT-RT-03-000685, 2004.; Clegg, S. L. and Brimblecombe, P.: Application of a multicomponent thermodynamic model to activities and thermal properties of 0–40 mol kg−1 aqueous sulphuric acid from <200 K to 328 K, J. Chem. Eng. Data, 40, 43–64, 1995.; Clegg, S. L., Brimblecombe P., and Wexler, A. S.: A thermodynamic model of the system H$^+ $- NH$_4^+ $- Na$^+ $- SO$_4^2- $- NO$_3^- $ - Cl$^- $ - H2O at at 298.15 K, J. Phys. Chem., A102, 2155–2171, 1998a.; Clegg, S. L., Brimblecombe, P., and Wexler, A. S.: A thermodynamic model of the system H$^+ $- NH$_4^+ $ - SO$_4^2- $ - NO$_3^- $ - H2O at tropospheric temperatures, J. Phys. Chem., A102, 2127–2154, 1998b.; Clegg, S. L., Kleeman, M. J., Griffin, R. J., and Seinfeld, J. H.: 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, Atmos. Chem. Phys., 8, 1087–1103, 2008.; Clegg, S. L., Pitzer, K. S., and Brimblecombe, P.: Thermodynamics of multicomponent, miscible, ionic solutions. II. Mixtures including unsymmetrical electrolytes, J. Phys. Chem., 96, 9470–9479, 1992.; Clegg, S. L., Rard, J. A., and Pitzer, K. S.: Thermodynamic properties of 0–6 mol kg−1 aqueous sulphuric acid from 273.15 to 328.15 K, J. Chem. Soc., Faraday Trans., 90, 1875–1894, 1994.; Clegg, S. L. and Seinfeld, J. H.: Improvement of the Zdanovskii-Stokes-Robinson model for mixtures containing solutes of different charge types, J. Phys. Chem. A, 108, 1008–1017, 2004.; Clegg, S. L. and Seinfeld, J. H.: Thermodynamic models of aqueous solutions containing inorganic electrolytes and dicarboxylic acids at 298.15 K. I. The acids as non-dissociating components, J. Phys. Chem. A, 110, 5692–5717, 2006a.; Clegg, S. L. and Seinfeld, J. H.: Thermodynamic models of aqueous solutions containing inorganic electrolytes and dicarboxylic acids at 298.15 K, II. Systems including dissociation equilibria, J. Phys. Chem. A, 110, 5718–5734, 2006b.; Clegg, S. L., Seinfeld, J. H., and Brimblecombe, P.: Thermodynamic modelling of aqueous aerosols containing electrolytes and dissolved organic compounds, J. Aerosol Sci., 32, 713–738, 2001.; Clegg, S. L. and Simonson, J. M.: A BET model of the thermodynamics of aqueous multicomponent solutions at extreme concentration, J. Chem. Thermodyn., 31, 1457–1472, 2001.; Clegg, S. L. and Whitfield, M.: Activity coefficients in natural waters, in: Activity Coefficients in Electrolyte Solutions

 

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