AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Adsorption-Based Chemical Thermodynamics of Atmospheric Aerosols: Towards Reduced Parameterization, Temperature Dependence, and Organic Solvents
CARI DUTCHER, Caitlin Asato, Anthony Wexler, Simon Clegg, University of California, Davis
Abstract Number: 96 Working Group: Aerosol Chemistry
Abstract The calculation of gas/liquid/solid equilibrium by soluble aerosols, and their water uptake as functions of temperature and relative humidity, is central to atmospheric chemistry (e.g., new particle formation, the behavior of cloud condensation nuclei, cloud formation, visibility, air quality, and climate). Using statistical mechanics and multilayer adsorption isotherms, we recently developed a transformative method for capturing thermodynamic properties of multicomponent aerosols over the entire concentration range (i.e., 0 to 100% relative humidities).[1] Now, we explore improvements of the model to include reduced parameterization, temperature dependence, and organic phases. Starting with the apparent radial dependence in the multilayer adsorption of solvent molecules on a solute, in this work, the values of the energies of adsorption are related to known analytic short-range dipole-dipole and ion-dipole Coulombic electrostatic relationships. In the case of non-electrolytes or organic molecules, the physical properties necessary to calculate the energies of adsorption are the dipole moments of the solvent and the solute and the intermolecular solute-solvent and solvent-solvent bond lengths. For ionic solutions, the ionic charge types, ionic-solvent bond lengths and solvent-solvent bond lengths are the necessary parameters to calculate the energy of adsorption parameter. The majority of these physical properties, with the exception of the solute-solvent intermolecular bond lengths, are available in the literature, resulting is significant reduction of adjustable parameters as well as activity coefficient predictions for solutes and mixtures for which there are no activity data. Further implications for systems of mixed charge types and mixed-solvents as well as parameter temperature dependence are explored. Finally, a practical discussion of the thermodynamic model for key atmospheric systems, such as sulfuric acid containing aqueous solutions, to extreme low water activity and temperatures will be given.
[1] Dutcher et al. J. Phys. Chem. (2011, 2012, 2013).