Aerosol acidity plays a critical role in many multiphase chemical processes in the atmosphere. Specifically, acid-catalyzed reactions of secondary organic aerosol (SOA) precursors, which partition to the particle phase, have been shown to occur rapidly at the pH values (0-3) models predict for ambient particles. However, despite the importance of acidity for multiphase chemistry, there are limited approaches to determine the acidity of aerosols in the atmosphere. Herein, two methods for directly determining the acidity of individual particles will be discussed and compared. This will include a recently-developed method for ambient measurements and expansion of a previously-developed Raman microspectroscopy approach. Together these methods reveal key properties, including size-dependent behavior. Challenges related to water content, the complex composition of atmospheric particles, and sampling will be discussed. Together these methods are providing are more detailed understanding of aerosol acidity and its implications for heterogeneous and multi-phase reactions involving atmospheric aerosols.<br/>

Integrating direct measurements of aerosol pH to improve understanding of acidity in the atmosphere

254th National Meeting (2017)

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