A phase equilibrium model for atmospheric aerosols containing 1 inorganic electrolytes and organic compounds ( UHAERO ) , with 2 application to dicarboxylic acids

4 Computation of phase and chemical equilibria of water-organic-inorganic mixtures is 5 of significant interest in atmospheric aerosol modeling. A new version of the phase par6 titioning model, named UHAERO, is presented here, which allows one to compute the 7 phase behavior for atmospheric aerosols containing inorganic electrolytes and organic com8 pounds. The computational implementation of the model is based on standard minimiza9 tion of the Gibbs free energy using a primal-dual method, coupled to a Newton itera10 tion. Water uptake and deliquescence properties of mixtures of aqueous solutions of salts 11 and dicarboxylic acids, including oxalic, malonic, succinic, glutaric, maleic, malic, or methyl 12 succinic acids, are based on a hybrid thermodynamic approach for the modeling of ac13 tivity coefficients [Clegg and Seinfeld [2006a, b]]. UHAERO currently considers ammo14 nium salts and the neutralization of dicarboxylic acids and sulfuric acid. Phase diagrams 15 for sulfate/ammonium/water/dicarboxylic acid systems are presented as a function of 16 relative humidity at 298.15K over the complete space of compositions. 17