AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Hydroxyl Radicals from Isoprene Hydroxy Hydroperoxide (ISOPOOH) Decomposition Induced by Irons in Water
TING FANG, Pascale Lakey, Jean Rivera-Rios, Frank Keutsch, Manabu Shiraiwa, University of California, Irvine
Abstract Number: 375 Working Group: Aerosol Chemistry
Abstract The hydroxyl radical (OH) is one of the most important oxidants in the atmosphere. It reacts both in the gas phase and in clouds and it is involved in the secondary processing of the majority of organic species. It is also a key reactive oxygen species that play a crucial role in air quality and human health. Sources of OH like ozone (O3) and hydrogen peroxide (H2O2) are well studied but the kinetics and formation mechanisms of OH radicals by organic compounds are not well understood. In the present study, the isoprene oxidation product, isoprene hydroxy hydroperoxide (ISOPOOH), was synthesized in high purity to investigate its potential to form OH radicals in the presence of inorganic iron(II) and iron(III). Using electron paramagnetic resonance (EPR) spectroscopy with a spin-trapping technique, we find that OH and carbon-centered radicals are formed from the aqueous reactions of ISOPOOH with both iron(II) and iron(III) at room temperature. Kinetic modelling suggests that ISOPOOH can react with iron(II) via Fenton-like reactions leading to OH formation. Iron(III) is also found to react with ISOPOOH in a similar manner to generate OH radicals. In addition, the effects of metal-organic complexing on OH production were examined: oxalic acid largely affects the OH generated by ISOPOOH and iron reactions, likely due to oxalic acid forming a complex with iron. These findings contribute to our understanding and quantification of the role of organics and metals in ROS generation through atmospheric aqueous-phase chemistry.