(442a) Measurement of Organic Aerosol Hygroscopicity and Oxidation Level As a Function of Volatility

Hygroscopicity, oxidation level, and volatility are three of the most important properties of atmospheric organic aerosol (OA). Many studies have been dedicated to the determination of these properties individually and chemical transport models (CTMs) use the corresponding results to simulate atmospheric OA, but often struggle to reproduce what is measured in the atmosphere. Cain and Pandis (2017) developed and evaluated a measurement and analysis technique to determine OA hygroscopicity and oxidation level as a function of volatility. Furthermore, Louvaris et al. (2017) combined thermodenuder and isothermal dilution measurements in order to better constrain OA volatility distributions over a large range. This study combines these two techniques and applies them in smog chamber experiments focusing on secondary OA production from the ozonolysis of various volatile organic precursors.

The synthesis of the two techniques resulted in hygroscopicity and oxidation level distributions that spanned a large range of volatility (around 6-8 orders of magnitude) for each OA system. These distributions not only provide a quantitative approach to understanding OA behavior to different perturbations (temperature changes, dilution, etc.), but they can also be converted into the two-dimensional volatility basis set framework to allow for easier implementation into CTMs. The successful combination of these two techniques provides an experimental and analysis framework that can be applied to ambient OA in order to determine a concrete relationship between these three properties, which can be used to update CTMs accordingly.

Cain, K. P., and Pandis, S. N.: A technique for the measurement of organic aerosol hygroscopicity, oxidation level, and volatility distributions, Atmos. Meas. Tech., 10, 4865-4876, 2017.

Louvaris, E. E., Karnezi, E., Kostenidou, E., Kaltsonoudis, C., and Pandis, S. N.: Estimation of the volatility distribution of organic aerosol combining thermodenuder and isothermal dilution measurements, Atmos. Meas. Tech., 10, 3909-3918, 2017.