AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Investigating the Formation of Quinonic Compounds from Aqueous-phase Reactions of Phenols
WENQING JIANG, Lu Yu, Shan Zhou, Alexander Laskin, Cort Anastasio, Qi Zhang, University of California, Davis
Abstract Number: 599 Working Group: Aerosol Chemistry
Abstract Quinones are a class of oxygenated derivatives formed from aromatic hydrocarbons such as polycyclic aromatic hydrocarbons (PAHs) and phenols. Quinones contain two carbonyl groups in a fully conjugated cyclic dione structure and are effective light-absorbing compounds. Quinonic compounds are also a concern for human health due to their ability to generate reactive oxygen species (ROS). Because of their low volatilities, quinonic compounds tend to exist in the particle phase, where they can affect the optical and toxicological properties of particles. Previous studies have observed the presence of quinones in wood smoke, which is a large source of phenolic compounds. In this study, we investigate the production of quinones through aqueous-phase oxidation of phenol and two methoxyphenols using high resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS) and nanospray desorption electrospray ionization mass spectrometry (nano-DESI MS). Formation of quinonic compounds was observed in the secondary organic aerosols formed through the aqueous reactions (aqSOA) of phenol, guaiacol, and syringol with the triplet excited state of an aromatic carbonyl (3C*) and the hydroxyl radical (·OH). Several HR-ToF-AMS tracer ions that can potentially represent quinones (e.g. C6H4O2+ and C12H8O6+ in phenol aqSOA and C6H4O2+, C14H12O7+ and C14H12O8+ in guaiacol aqSOA) have been identified in this study, allowing us to track the changes of quinonic concentrations during the course of the aqueous reactions. The relative abundances of quinones increase significantly in the first two hours of aqueous-phase photochemical oxidation, and then plateau or slightly decrease in the later hours. Although previous studies of our group find that fragmentation eventually dominates over oligomerization and functionalization in the photochemical evolution of phenolic aqSOA, our results here suggest that quinones may still play an important role even in the late periods of photochemical oxidation.