AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Heterogeneous Oxidation of Organic Coatings on Submicron Aerosol Particles
CHRISTOPHER LIM, Eleanor Browne, Rebecca Sugrue, Jesse Kroll, MIT
Abstract Number: 360 Working Group: Aerosol Chemistry
Abstract Heterogeneous oxidation of organic aerosol (OA) can significantly transform the chemical and physical properties of particulate matter in the atmosphere, potentially leading to volatilization of oxidized volatile organic compounds and/or changes to particle composition. It has become increasingly apparent that the heterogeneous oxidation kinetics of OA depend strongly on the viscosity and morphology of the particles. However, the impact of particle morphology on the evolution of the chemical composition of OA resulting from chemical aging remains poorly characterized. In this work, squalane (C$_(30)H$_(62)), a model compound for primary OA, is coated onto 200 nm dry ammonium sulfate particles at various thicknesses (2-20 nm) and exposed to hydroxyl radical (OH) in a flow tube reactor. The resulting changes in chemical composition are monitored online with an Aerodyne High Resolution Time-of-flight Aerosol Mass Spectrometer (AMS). We show that thin organic coatings can undergo dramatic changes in oxidation state and lose a significant amount of organic mass after relatively low OH exposures (the equivalent of hours to days in the atmosphere). This implies that for morphologically complex particles, heterogeneous oxidation has the capability to greatly alter the surface composition and properties of atmospheric OA.