The objective of the OLFA-ROA project is to provide a better description of the chemical mechanisms of terpene and catechols ozonolysis from the initial steps in the gaseous phase to the formation of secondary organic aerosols in the course of the oxidation processes. More specifically, the project aims at answering the following scientific questions:
What are the first mechanistic steps in the chemical oxidation of terpenes by O3 leading to SOA production? The understanding of the initial stages and the identification of first reaction intermediates are of higher interest, albeit often difficult to carry out in “traditional” environmental chamber experiments because reaction time is continuously increasing. Furthermore, these first steps are followed by nucleation processes which are still poorly described in the atmosphere.
What are the first mechanistic steps in the chemical oxidation of catechols by O3 leading to SOA production? The understanding of the initial stages and the identification of first reaction intermediates leading to the formation of the first nano-particles are known even less than for terpene ozonolysis.
What is the influence of the ambient conditions, in particular the presence of ammoniac, alcohols and NOx on the formation of SOA? The environmental conditions in which semi-volatile organic compounds are formed in the atmosphere are known to influence considerably the subsequent formation of SOA. Ammoniac (basic compound) and alcohols are frequently observed in the environment together with terpenes while NOx and catechols species (arising from combustion processes) are often emitted together in urban areas. Nucleation thresholds, aerosol mass yields and chemical composition will be particularly investigated. This way, the presence of these contaminants could impact the formation of local SOA.