Significance of hydrogen abstraction in the formation of highly oxygenated organic molecules in the OH oxidation of monoterpenes

Secondary organic aerosol (SOA), formed by oxidation of volatile organic compounds, significantly influence air quality and climate. Biogenic highly oxygenated organic molecules (HOM), particularly those formed from monoterpenes, play a key role in SOA formation and growth. As the most important daytime oxidant, hydroxyl radical (OH•) initiated HOM from monoterpenes is believed to be mainly formed via OH addition channel. However, for α-pinene and limonene, we found that the contribution of hydrogen abstraction channel by OH contribute a significantly to HOM formation. We will present our observations and theoretical calculations, showing the role of hydrogen-abstraction and alkoxy radicals for fast autoxidation leading to HOM formation. We also provide formation mechanisms of and yields of HOM, suggesting the non-negligible contribution of the hydrogen abstraction channel to ambient SOA, particularly in OH-rich areas.