Crystallization of Sulfate-Nitrate-Ammonium
-Proton Particles

Aerosol particles exhibit hysteresis in their interaction with water vapor. Crystalline particles uptake liquid water when the ambient relative humidity (RH) reaches the deliquescence relative humidity (DRH) of the particles. However, aqueous particles of the same composition do not crystallize at the DRH, but become highly supersaturated until the RH reaches the crystallization relative humidity (CRH) and the particles crystallize. Predictions of aerosol particle phase thus require knowledge of the DRH, the CRH, and the ambient relative humidity (RH) history. Although the DRH values of aerosol particles can be predicted based on thermodynamic models, there is currently no physical model that can successfully predict CRH values.

DRH and CRH also depend on chemical composition. Particles composed of sulfate, nitrate, ammonium, and proton (SNA) are especially important because, on a global basis, they make the largest anthropogenic contribution to the aerosol mass budget.

In our first report, we experimentally determined the CRH values of SNA particles as a function of composition, providing polynomials that can be used in chemical transport models to determine the physical state of particles. Subsequent reports have focused on identifying the specific solids formed when particles crystallize. We are currently interested in determining the morphology of crystalline particles and how morphology depends on relative humidity history.

People Involved

• Current Group Members

  • Thomas Rosenorn
  • Scot Martin

Publications

1. T. Rosenoern, J.C. Schlenker, and S.T. Martin, "Hygroscopic Growth of Multicomponent Aerosol Particles Influenced by Several Cycles of Relative Humidity," Journal of Physical Chemistry A, 2008, 112, 2378-2385. PDF File. Errata.

2. Schlenker, J.C., and Martin, S.T., "Crystallization Pathways of Sulfate-Nitrate-Ammonium Aerosol Particles," The Journal of Physical Chemistry A, 2005, 109, 9980-9985. PDF File.

3. Schlenker, J.C., Malinowski, A., Martin, S.T., Hung, H.M., Rudich, Y., "Crystals Formed at 293 K by Aqueous Sulfate-Nitrate-Ammonium-Proton Aerosol Particles," Journal of Physical Chemistry A, 2004, 108, 9375-9383. PDF File.

4. Martin, S.T., Schlenker, J.C., Malinowski, A., Hung, H.M., and Rudich, Y., "Crystallization of atmospheric sulfate-nitrate-ammonium particles," Geophysical Research Letters, 2003, 30, 2102. PDF File. Movie File.