AF2OM

Monoterpenes are massively emitted by vegetation and undergo rapid gas-phase oxidation by OH, O₃, and NO₃. Their oxidation generates first-generation oxygenated oxidation products (FGTOP), which, being semi-volatile, are likely to form secondary organic aerosols (SOA) or condense onto preexisting surfaces. These FGTOPs themselves can react with atmospheric oxidants in both the gas phase and the condensed phase. Due to their reactivity, FGTOPs can impact air quality through the formation of ozone and SOA.

How do FGTOPs contribute to the SOA/O₃/NOₓ/HOₓ budget, climate change, and cloud formation?

To address these questions, AF2OM proposes to determine the kinetic parameters as a function of temperature and the oxidation mechanisms by O₃, OH, and NO₃ of FGTOPs in the gas phase. The formation yields and chemical composition of SOA formed will be determined following the oxidation of FGTOPs by NO₃ and O₃. The kinetic and mechanistic data will be used in the GECKO-A model, and exploratory simulations will be performed to examine the contribution of FGTOPs to the SOA/O₃/NOₓ/HOₓ budget under typical atmospheric conditions.

The partitioning of FGTOPs between the gas phase and a quartz surface will be determined. Then, heterogeneous reactivity toward ozone and OH radicals will be examined in terms of kinetics and mechanisms for quartz surfaces coated with FGTOPs and levitated FGTOP particles. The lifetimes of gaseous or condensed FGTOPs will be compared to determine whether FGTOPs lead to local photochemical pollution or are likely to be transported over long distances in their particulate state. Finally, determining the hygroscopic and radiative properties of SOA will help assess their contribution to Earth’s radiative balance.