Hysteresis and History Effects of Organic Aerosol Particles Containing phenylglyoxylic acid and 3,4-dimethoxyphenylacetic acid

Open Access
Author:
Parker, Robert Graveson
Graduate Program:
Chemistry
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
February 19, 2016
Committee Members:
  • Miriam Arak Freedman, Thesis Advisor
Keywords:
  • liquid-liquid phase separation
  • Aqueous 2-phase system
  • organic aerosol
  • atmospheric chemistry
  • climate
Abstract:
Aerosol particles undergo numerous phase transitions in the atmosphere as the relative humidity is varied. Understanding the location and occurrence of these phase transitions is essential for understanding the morphology and successful modeling of aerosol particles. Some phase transitions that are possible are deliquescence, efflorescence, separation, and mixing. To investigate the phase transitions of organic aerosol particles, model systems composed of either phenylglyoxylic acid or 3,4-dimethoxyphenylacetic acid with either ammonium sulfate, ammonium chloride, or sodium sulfate were studied. Using optical microscopy, these systems have revealed a hysteresis between the location of separation and mixing phase transitions. To our knowledge this hysteresis has never been reported before. Additionally a history effect has been observed in which the immediate RH and time history of the aerosol particle influences the location of the mixing phase transition. The existence of these two phenomena, in addition to their atmospheric implications, are discussed.