HR: 15:45h
AN: A33C-07    [Abstracts]
TI: Modeling and Computation of Thermodynamic Equilibrium for Mixtures of Inorganic and Organic Species
AU: * Caboussat, A
EM: caboussat@math.uh.edu
AF: University of Houston, 4800 Calhoun Rd, Houston, TX 77204-3008, United States
AU: Amundson, N R
EM: amundson@uh.edu
AF: University of Houston, 4800 Calhoun Rd, Houston, TX 77204-3008, United States
AU: He, J
EM: jiwenhe@math.uh.edu
AF: University of Houston, 4800 Calhoun Rd, Houston, TX 77204-3008, United States
AU: Martynenko, A V
EM: andrey@math.uh.edu
AF: University of Houston, 4800 Calhoun Rd, Houston, TX 77204-3008, United States
AU: Seinfeld, J H
EM: seinfeld@caltech.edu
AF: California Institute of Technology, Mail Code 210-41, Pasadena, CA 91125, United States
AB: A series of modules has been developed in the atmospheric modeling community to predict the phase transition, crystallization and evaporation of inorganic aerosols. Modules for the computation of the thermodynamics of pure organic-containing aerosols have been developed more recently; however, the modeling of aerosols containing mixtures of inorganic and organic compounds has gathered less attention. We present here a model (UHAERO), that is flexible, efficient and rigorously computes the thermodynamic equilibrium of atmospheric particles containing inorganic and organic compounds. It is applied first to mixtures of inorganic electrolytes and dicarboxylic acids, and then to thermodynamic equilibria including crystallization and liquid-liquid phase separation. The model does not rely on any a priori specification of the phases present in certain atmospheric conditions. The multicomponent phase equilibrium for a closed organic aerosol system at constant temperature and pressure and for specified feeds is the solution to the equilibrium problem arising from the constrained minimization of the Gibbs free energy. For mixtures of inorganic electrolytes and dissociated organics, organic salts appear at equilibrium in the aqueous phase. In the general case, liquid-liquid phase separations happen and electrolytes dissociate in both aqueous and organic liquid phases. The Gibbs free energy is modeled by the UNIFAC model for the organic compounds, the PSC model for the inorganic constituents and a Pitzer model for interactions. The difficulty comes from the accurate estimation of interactions in the modeling of the activity coefficients. An accurate and efficient method for the computation of the minimum of energy is used to compute phase diagrams for mixtures of inorganic and organic species. Numerical results show the efficiency of the model for mixtures of inorganic electrolytes and organic acids, which make it suitable for insertion in global three-dimensional air quality models. Preliminary results for mixtures of inorganic and organic species are presented and exhibit the influence of liquid phase separation on the salt cristallyzation.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 1029 Composition of aerosols and dust particles
DE: 1610 Atmosphere (0315, 0325)
DE: 3367 Theoretical modeling
DE: 4801 Aerosols (0305, 4906)
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly