AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Temperature Effects on Secondary Organic Aerosol Formation and its Properties
MARY KACARAB, Ping Tang, Lijie Li, Derek Price, David R. Cocker III, University of California, Riverside
Abstract Number: 500 Working Group: Aerosol Chemistry
Abstract Temperature has a profound effect on secondary organic aerosol (SOA) formed from various aromatic hydrocarbon species. A series of temperature-controlled atmospheric chamber experiments were carried out to revisit the effects of temperature on aerosol formation, volatility, hygroscopicity, and chemical composition. The temperature of the environmental chamber system was cycled through various patterns of 5, 27, and 40$^oC in order to examine the reproducibility and hysteresis of the SOA formed during aromatic photooxidation. It is consistently seen that a larger volume of SOA than would be expected is formed at the lower temperature (5$^oC) than is formed at room (27$^oC) and higher (40$^oC) temperatures. Significant mass is lost when the system is heated up, not all of which is gained back once the system is cooled down again, indicating the formation of thermally labile compounds. The chemical composition of the aerosol is monitored with an Aerodyne High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS), while volatility and hygroscopicity are each measured with a Tandem Differential Mobility Analyzer (V-TDMA and H-TDMA, respectively). Furthermore, online gas phase chemical composition is observed with the SYFT Technologies Voice200 Selected Ion Flow Tube Mass Spectrometer (SIFT-MS). The multiple physical and chemical properties studied also show clear impacts due to both current system temperature and temperature at which the aerosol is formed. Properties of aerosol formed at 40$^oC then cooled to 5$^oC do not match the properties of aerosol formed at 5$^oC, showing a clear hysteresis effect. Due to the wide range of temperatures encountered in our troposphere, it is imperative that we understand temperature’s effect on aerosol formation in order to implement it in current SOA formation models.