AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Formation of Hydroxyl Radical from Photolysis of Aqueous Secondary Organic Aerosol Material
SHOUMING ZHOU, Katie Badali, Dana Aljawhary, Maria Antiñolo, Crystal Chen, Appana Lok, Emma Mungall, Jenny Wong, Ran Zhao, Jonathan Abbatt, Univerisity of Toronto,Canada
Abstract Number: 206 Working Group: Aerosol Chemistry
Abstract A considerable number of lab and field studies have focused on the formation pathways and chemical composition of SOA. However, less attention has been paid to its reactive properties and photochemical aging processes. Although it is known that the photolysis of SOA contributes to its atmospheric aging, it is unclear whether the photochemical aging occurs through only primary reactions or secondary reaction of SOA with radicals produced from a primary photolysis of SOA materials.
In this work, using benzoic acid as OH radical trap, the OH formation rates from ultraviolet photolysis of aqueous SOA, collected from ozonolysis of α-pinene and limonene in an environmental chamber, have been determined by the formation rate of p-hydroxybenzoic acid, measured using offline HPLC analysis. To evaluate whether the OH is formed by photolysis of H2O2 or organic hydroperoxides (ROOH), the peroxide content was measured using the horseradish peroxidase-dichlorofluorescein assay. The experimental results indicate that the OH formation from SOA is likely due to photolysis of ROOH species that are part of the SOA material. Relative to the peroxide level in the SOA, the quantum yield for OH generation from α-pinene SOA is reported to be close to unity.