Relating Secondary Organic Aerosol Characteristics with Cloud Condensation Nuclei Activity
A study on secondary organic aerosol (SOA) was conducted with a focus on correlating the chemical and physical characteristics with aerosol's ability acting as cloud condensation nuclei (CCN). The work focuses on three types of aerosol: beta-caryophyllene ozonolysis SOA, aliphatic amine SOA, and cigarette environmental tobacco smoke. The work on beta-caryophyllene ozonolysis SOA enhances our understanding of the CCN activity of SOA formed with and without the presence of isoprene, by probing the effects of a series of environmental parameters on the formation and properties of SOA with more ambient-relevant precursor concentrations. This study demonstrates that aerosol formed from ozonolysis of a mixture of low and high molecular weight terpenes can be hygroscopic and can contribute to the global biogenic SOA CCN budget.
The aliphatic amine work explores the atmospheric behaviors of amines with typical atmospheric oxidants, e.g. nitrate radical, hydroxyl radical and ozone. This study shows that night time chemistry of aliphatic amines can produce secondary organic and inorganic aerosol mixtures, and the relative contribution of each component depends on the environment relative humidity. Thus, modelers need to include as much ambient data as possible in order to mimic the amine behavior in the real atmosphere. The hygroscopicity of aliphatic amine secondary aerosol is also investigated, focusing on the correlation between complex composition and aerosol CCN activity. Despite of measurement artifacts, primary aliphatic amine aerosol is composed of highly volatile components with high hygroscopicity.
The third part of the work characterizes the environmental tobacco smoke (ETS) from research cigarettes, with an emphasis on enhanced condensational growth (ECG), represented by CCN activity and droplet formation properties. Changes in smoke particle size, chemistry, and volatility are correlated to changes in droplet behavior from offline and online chemical and physical measurements. The study shows that reference cigarette ETS are hygroscopic and will have similar lung deposition rates despite source.