Efflorescence and ice nucleation in ammonium sulfate particles: Analysis of experimental results using scaled nucleation theory

Temperature-dependent efflorescence and ice nucleation results of ammonium sulfate aerosol obtained from flow tube studies are analyzed using a newly developed model based on scaled nucleation theory. The presented thermodynamic model defines trajectories of constant reduced nucleation barrier height as a function of temperature and yields simple analytic expressions for the liquid-solid nucleation boundaries. Within the context of the model the experimental results are interpreted in terms of surface enthalpy, entropy and nucleus size. These thermodynamic properties, along with a full thermodynamic model, can be then used to predict changes in the composition and phase of ammonium sulfate particles over the wide range of relative humidity and temperature conditions found in the atmosphere.