Formation of Environmentally Persistent Free Radicals in Aromatic Secondary Organic Aerosols

CAITLYN CRUZ, Kasey Edwards, Lena Gerritz, Manabu Shiraiwa, University of California, Irvine

     Abstract Number: 638
     Working Group: Aerosol Chemistry

Abstract
Atmospheric particulate matter contains particle-bound free radicals, known as environmentally persistent free radicals (EPFR), that have a lifespan on the timescale of hours, days or longer. EPFRs are known to be redox active to generate reactive oxygen species (ROS) that may induce oxidative stress upon inhalation and respiratory deposition. Previous studies have shown that secondary organic aerosols (SOA) derived from oxidation of naphthalene and anthracene contain significant amounts of EPFRs. In this study, we generate SOA from aromatic precursors (naphthalene, toluene, indole) using an oxidative flow reactor. SOA generation and particle size distribution were monitored with a scanning mobility particle sizer (SMPS). We applied electron paramagnetic resonance spectroscopy to quantify concentrations of EPFRs. We varied several parameters such as volatile organic compound carrier VOC flow, relative humidity, and collection time to investigate their influence on EPFR yields. Preliminary results indicate that EPFRs can be generated from a single-ringed aromatic hydrocarbon and EPFR yields depend on precursors and SOA formation conditions.