Aerosol Physical Chemistry Process Modeling

Aerosol particles affect the Earth’s climate both directly and indirectly by scattering and absorbing solar radiation and modifying cloud properties, respectively. Atmospheric aerosols are often complex aqueous mixtures of organic and inorganic components. In the laboratory experiment part of our research we measure the surface tension, refractive index, and water vapor pressure phase lines for a select number of solution compositions, containing various amounts of organic and inorganic components found in atmospheric particles. However to successfully use the results of our experiments in large-scale chemistry and climate models of the atmosphere would require development of physical chemistry process models (PCPMs). Compact PCPMs are often used in large-scale models to numerically predict the physicochemical properties of aerosol solutions in the atmosphere for a given set of ambient conditions (temeprature, pressure and relative humidity) and species concentrations. In the past we have successfully used measured properties of binary aqueous solutions (i.e., water and solute activity coefficients, binary adsorption isotherms, etc.) to predict the phase behavior and surface composition of multicomponent inorganic solutions both in the troposphere and stratosphere. We plan to expand our previous work in this area to take into account for the effects of organic matter phase distribution on the physicochemical properties of atmospheric aerosols. Cloud activation, ice nucleation, hygroscopic growth, surface and optical properties of particles are all affected by the aerosol composition and phase and our ultimate goal is to be able to predict such variables using compact PCPM algorithms. Some aspects of this project will involve collaborations with Mark Jacobson in the Department of Civil and Environmental Engineering at Stanford.

 

Relevant References

Djikaev, Y., and A. Tabazadeh, The effect of adsorption on the uptake of organic trace gas by cloud droplets, J. Geophys. Res., 108 (22), doi: 10.1029/2003JD003741, 2003.

Tabazadeh, A., Y. S. Djikaev, and H. Reiss, Surface crystallization of supercooled water in clouds, Proc. Natl. Acad. Sci. 99, 15873, 2002. (NAS issued a press release on this article)

Tabazadeh, A., Y. S. Djikaev, P. Hamill, and H. Reiss, Laboratory evidence for surface nucleation of solid polar stratospheric cloud particles, J. Phys. Chem.A., 106, 10238, 2002.

Djikaev, Y., A. Tabazadeh, P. Hamill, and H. Reiss, Thermodynamic conditions for the surface-stimulated crystallization of atmospheric droplets, J. Phys. Chem. A, 106, 10247, 2002.

Lin, J. S., and A. Tabazadeh, The effect of nitric acid uptake on the deliquescence and efflorescence of binary ammoniated aerosols in the upper troposphere, Geophys. Res. Lett., 29(10), doi:10.1029/2002GL015251, 2002.

Lin, J. S., and A. Tabazadeh, An aerosol physical chemistry model for the NH3/H2SO4/HNO3/H2O system at cold temperatures, J. Geophys. Res., 106, 4815, 2001.

Tabazadeh, A., E. J. Jensen, and O. B. Toon, A surface chemistry model for nonreactive trace gas adsorption on ice: Implications for nitric acidscavenging by cirrus, Geophys. Res. Lett., 26, 2211, 1999.

Tabazadeh, A., O. B. Toon, S. L. Clegg, and P. Hamill, A new parameterization of the H2SO4/H2O composition: Atmospheric implications, Geophys. Res. Lett., 24, 1931, 1997.

Tabazadeh, A., R. P. Turco, and M. Z. Jacobson, A model for studying the composition and chemical effects of stratospheric aerosols, J. Geophys. Res., 98, 12,897, 1994.