Phase State and Relative Humidity Regulate the Heterogeneous Oxidation Kinetics and Pathways of Organic-Inorganic Mixed Aerosol
CHUANYANG SHEN, Wen Zhang, Haofei Zhang,
University of California, Riverside Abstract Number: 343
Working Group: Aerosol Chemistry
AbstractHeterogeneous oxidation of organic aerosols is one of the most critical chemical aging processes that influence the organic particle’s chemical composition and subsequent physical properties. The inorganic species coexistent with atmospheric organic particles is thought to influence the reactive uptake of gas-phase oxidative species such as hydroxyl radicals (OH). However, very limited previous studies have explored the role of the inorganic salts on the heterogeneous oxidation of organic species in aerosols. This study examines the heterogeneous oxidation of OH radical, the predominant oxidant in the atmosphere, on varying fractions of glutaric acid-ammonium sulfate mixed particles under different RH conditions in a flow tube reactor. The oxidation kinetics and products are analyzed using a gas chromatography mass spectrometer and an ion mobility mass spectrometer for both phase-separated (low-RH) and well-mixed (high-RH) particles as a function of varying organic mass fraction (
forg). Results find that under both dry and humid conditions, the increased inorganic fraction will accelerate the oxidation rate of the organic material in aerosol particles. Analysis of the oxidation products also reveals that the enhanced water uptake by the inorganic under humid conditions will favor alkoxy radical fragmentation and inhibit its secondary chemistry.