AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Comparative Assessment of the Oxidative Potential of Daytime and Nighttime Secondary Organic Particles in Los Angeles
ARIAN SAFFARI, Sina Hasheminassab, Martin Shafer, James Schauer, Constantinos Sioutas, University of Southern California
Abstract Number: 193 Working Group: Urban Aerosols
Abstract Oxidative potential, induced following the interaction of reactive oxygen species (ROS) with cells, is known as one of the major pathways leading to the adverse health effects of exposure to particulate matter. Secondary organic species comprise a substantial fraction of fine and ultrafine particulate matter in the Los Angeles basin and therefore quantification of the toxicological properties of these particles is important from a public health perspective. Secondary organic aerosols can be formed through gas-phase photochemical reactions in the atmosphere followed by condensation of the products in the particle phase during daytime, as well as through aqueous-phase reactions in the nighttime. Differences in formation mechanism and chemistry of daytime and nighttime secondary organic aerosols can, potentially, lead to variations in their oxidative potential and thus toxic properties. In this study, fine and ultrafine particles were studied throughout the warm season (August through October) and cold season (December through February) in central Los Angeles, during episodes of daytime and nighttime secondary organic aerosol (SOA) formation. SOA concentrations were quantified based on the EC tracer method, by continuous monitoring of organic and elemental carbon. Moreover, physical properties of particles (including mass and number concentrations, total volume and condensational sink) were assessed and compared during these two periods by continuous measurement of particle size distributions. Parallel to the continuous monitoring, time-integrated fine and ultrafine samples were also collected using a hi-volume impactor sampler, in order to quantify the chemical composition, as well as the oxidative potential of particles during different episodes of SOA formation.