Exploring the Role of Hydroperoxyl Radical in the Multiphase Organic Aerosol Aging

WEN ZHANG, Haofei Zhang, University of California, Riverside

     Abstract Number: 261
     Working Group: Aerosol Chemistry

Abstract
Organic aerosols (OA) ubiquitously exist in the atmosphere and their heterogeneous oxidative aging can significantly impact air quality, climate change and human health. Hydroperoxyl radicals (HO2·) are important gas-phase oxidant in the troposphere along with hydroxyl radicals (·OH) and are known to play a key role in gas-phase organic compound oxidation chemistry. However, it is unclear how HO2· affect heterogeneous OA oxidation kinetics and the aerosol composition through aging. In this study, we carry out •OH-initiated heterogeneous aging of oxygenated OA model systems by using a flow tube reactor (FTR). HO2· concentrations are controlled in these experiments. We explore the heterogenous aging kinetics of OA model systems with the HO2·/·OH concentration ratios of 10-1 – 102 using a thermal desorption chemical ionization mass spectrometer (TD-CIMS). Besides, we use an ion mobility spectrometry mass spectrometer (IMS-MS) and a gas chromatography mass spectrometer (GC-MS) to characterize the aged OA chemical composition and detect key oxidation products under various HO2· conditions. Our results suggest that the presence of HO2· may affect both OA aging kinetics and composition through complex processes.