Investigation of Aerosol in the Southeastern U.S. during the SOAS Field Campaign: Cloud Condensation Nuclei Activity, Hygroscopicity, Droplet Activation Kinetics, and Volatility of Ambient and Water-Soluble Aerosol

It is well known that complexities of aerosol partitioning can impact a multitude of aerosol properties including cloud condensation nuclei (CCN) activity, hygroscopicity, volatility, and droplet activation kinetics as a result of changes in organic mass and composition, among other things. For many ambient measurements, combined biogenic and anthropogenic emissions make it difficult to deconvolute the properties of primary organic aerosol (POA) and semi-volatile organic aerosol (SOA) from different sources. In this study, aerosol were collected during the 2013 Southern Oxidant and Aerosol Study (SOAS) in rural Alabama, a strongly biogenic site with little anthropogenic influence, making it possible to investigate the major impacts of biogenic emissions on aerosol properties. During the 2013 SOAS field campaign, 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. Particles were either sampled directly from ambient or with a Particle Into Liquid Sampler (PILS), allowing for the investigation of water-soluble aerosol properties. The difference in key aerosol properties (e.g., activation kinetics, hygroscopicity, and volatility) between ambient aerosol and water-soluble aerosol components, primarily the oxidation state of the organic fraction, is investigated.