AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Detection and Quantification of Reactive Oxygen Species in Ambient and Laboratory-generated Organic Aerosols
MANABU SHIRAIWA, Andrea Arangio, Haijie Tong, Fobang Liu, Christopher Kampf, Ulrich Poeschl, Max Planck Institute for Chemistry
Abstract Number: 118 Working Group: Aerosol Chemistry
Abstract Reactive oxygen species (ROS) and other related free radicals exist widely in the atmospheric environment. They play multifunctional roles in atmospheric chemistry, influencing formation and chemical aging of organic aerosols and adverse health effects of particulate matter in air pollution. Recent studies have found that aerosol particles can contain stable radicals such as semiquinone radicals and long-lived reactive oxygen intermediates. However, little is known on formation and abundance of ROS within atmospheric aerosol particles.
In this study we have detected and quantified ROS and related radicals in ambient particles and laboratory-generated secondary organic aerosols (SOA). Ambient particles have been sampled with a 24 h time resolution using a rotatory multi-stage cascade impactor (MOUDI) on the roof of the Max Planck Institute for Chemistry in Mainz, Germany. SOA were formed in a 2 m long quartz flow tube reactor by ozonolysis of pinenes and limonene as well as OH photooxidation of naphthalene. The collected particles were analyzed using a continuous wave Electron Paramagnetic Resonance (CW-EPR) spectrometer, allowing non-destructive analysis of collected particle on filters. We found that ambient particles with diameter of 100 - 300 nm contain substantial amount of stable organic radicals with concentrations on the order of 1010-1011 spin/μg of particles. The EPR spectra of each sample have a broad signal indicating the presence of multiple radical species in the particle phase. Combined with a spin trap technique, the formation of OH and other related radicals were observed upon extraction of SOA particles in water. We found that such formation can be accelerated in the presence of iron ions due to the Fenton reaction. These results may have interesting implication on cloud processing of organic aerosols and multiphase chemical processes in the lung lining fluid upon deposition of organic aerosols.