AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Gas-Phase Oxidation Impacts the CCN Activation of a 100nm Particle
Ashley Vizenor, AKUA ASA-AWUKU, University of California, Riverside
Abstract Number: 298 Working Group: Aerosols, Clouds, and Climate
Abstract Our current knowledge of cloud condensation nuclei (CCN) activity and the hygroscopicity of secondary organic aerosol (SOA) depends on particle size and composition, explicitly, the thermodynamic properties of the aerosol solute and subsequent interactions with water. Here, we examine the CCN activation of 3 SOA systems (2 biogenic single precursor and 1 mixed precursor SOA system) in relation to gas-phase decay. Specifically, the relationship between time, gas phase precursor decay and CCN activity of 100 nm SOA are studied. The studied SOA systems exhibit a time-dependent growth of CCN activity at an instrument supersaturation ~0.2%. As such, we define a critical activation time, t50, above which a 100 nm SOA particle will activate. The critical activation time for isoprene, longifolene and a mixture of the two precursor SOA are 2.01 hours, 2.53 hours and 3.17 hours, respectively. The activation times are then predicted with gas-phase kinetic data inferred from measurements of precursor decay. The gas-phase prediction of t50 agrees well with CCN measured t50 (within 0.05 hours of the actual critical times) and suggests that the gas-to-particle phase partitioning may be more significant for SOA CCN prediction than previously thought. We also provide evidence that this is not attributed to doubly-charged aerosol effects.