Formation of Reactive Oxygen Species in Irradiated Mixtures of Biomass Burning Compounds

LENA GERRITZ, Jinlai Wei, Sergey Nizkorodov, Manabu Shiraiwa, University of California, Irvine

     Abstract Number: 611
     Working Group: Aerosol Chemistry

Abstract
In recent years, the frequency and intensity of wildfires has increased, resulting in a need to understand the impact of biomass burning events such as the formation of reactive oxygen species (ROS) and organic radicals through the photochemical processes. Due to the complex composition of naturally formed biomass burning organic aerosol (BBOA) particles, previous research has limited understanding of the specific chemical reactions taking place within aqueous BBOA. The goal of this work is to use surrogate mixtures of benzoquinone and levoglucosan to elucidate the ROS formation kinetics and organic radical product composition from one reaction channel likely to be found in BBOA. The surrogate mixtures were prepared and then irradiated using a 100 W Mercury UV lamp and the ROS and organic radical formation was monitored using Electron Paramagnetic Resonance (EPR) spectroscopy over the time span of an hour. The mixtures were also analyzed using ultra-high-performance liquid chromatography coupled with high resolution mass spectrometry (UPLC-HRMS) to characterize the composition of the mixtures before and after irradiation at different concentrations of levoglucosan. We conduct further analysis by kinetic modeling to simulate the ROS formation kinetics. The ROS formed by benzoquinone reacted with levoglucosan to produce secondary free radicals. These results help interpret the transformation of BBOA compounds through cloud and fog processing.