AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Liquid-liquid Phase Separation in Particles Containing Ammonium Sulfate, Ammonium Bisulfate, Ammonium Nitrate and Sodium Chloride Mixed with Organics
YUAN YOU, Jacqueline Yakobi-Hancock, Allan Bertram, University of British Columbia
Abstract Number: 515 Working Group: Aerosol Chemistry
Abstract As the relative humidity cycles in the atmosphere, particles may undergo a range of phase transitions, including liquid-liquid phase separation. Using optical microscopy, we investigated liquid-liquid phase separation in particles containing organics and the following inorganic salts: ammonium sulfate, ammonium bisulfate, ammonium nitrate and sodium chloride. Specifically we investigated the relative humidity at which liquid-liquid phase separation occurred, which we refer to here as the separation relative humidity (SRH). SRH of the different organic-inorganic salt mixtures showed the same qualitative dependence on oxygen to carbon elemental ratio (O:C) of the organic material: liquid-liquid phase separation was never observed for O:C > 0.8, was always observed for O:C < 0.5 and was frequently observed for 0.5 < O:C < 0.8. These results are consistent with the suggestion that liquid-liquid phase separation occurs widely in the atmospheric particles. In addition, the SRH of almost all of the particles followed the same trend in SRH, SRH((NH4)2SO4) ≥ SRH(NH4HSO4) ≥ SRH(NaCl) ≥ SRH(NH4NO3). The trend in SRH with inorganic salts is consistent with salting out constants for the different salts and the Hofmeister Series.