AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Cloud Condensation Nuclei Activity of Secondary Organic Aerosol: Investigation of Hygroscopicity and Activation Kinetics
KATE CERULLY, Lea Hildebrandt Ruiz, Andrea Paciga, Tomi Raatikainen, Neil Donahue, Spyros Pandis, Athanasios Nenes, Georgia Institute of Technology
Abstract Number: 346 Working Group: Aerosols, Clouds, and Climate
Abstract Cloud condensation nuclei (CCN) activation is dependent on both aerosol size and chemistry. Thus, the investigation of CCN behavior of secondary organic aerosol (SOA) as it undergoes transformation in the atmosphere is complex and important. SOA from toluene was formed during Carnegie Mellon University chamber experiments. A suite of instruments, including a cloud condensation nuclei counter (CCNC), thermodenuder (TD), and high resolution time-of-flight aerosol mass spectrometer (AMS), were used to measure CCN activity, aerosol volatility, and aerosol composition and oxidation, respectively.
In this study, we investigate the hygroscopicity of SOA and specifically, the difference in hygroscopicity of denuded versus non-denuded as well as fresh versus aged aerosol. While the hygroscopicity parameter, kappa, is on average approximately 0.2, there are apparent trends in kappa during SOA formation and aging. In addition, we use Threshold Droplet Growth Analysis (TDGA), comparing the size of activated droplets against a standard of uninhibited activation such as ammonium sulfate, as well as a CCNC instrument model to investigate aerosol kinetics of size-selected SOA. By operating the CCNC in Scanning Flow CCN Analysis (SFCA) mode, we are able to investigate both the condensation and evaporation kinetics of aerosol. Aerosol condensation kinetics are similar to that of ammonium sulfate.