My research interests are the chemical processes involving organic compounds in the Earth atmosphere and their role in the natural Earth system, in pollution events, or in climate. My activities include laboratory studies, the analysis of atmospheric samples, and sometimes field measurements, and often involve the development of new methods or techniques.
1. Volatile organic radicals and the oxidizing capacity of the atmosphere
The Earth atmosphere oxidizes all the compounds that are emitted into it, which is considered as a self-cleaning ability, but also results in many phenomena such as ozone and smog formation, secondary aerosol formation ... This oxidizing capacity is sustained by complex chemical cycles involving free radicals. These fundamental cycles are still ill-understood today, in particular those involving organic radicals , which are difficult to monitor as a multitude of different organic radicals are present in the atmosphere.
Observing and understanding the reactivity of these organic radicals is one of my main projects, for which I have received in 2020 an ERC advanced grant: project EPHEMERAL ("DEtection & SpEciation of Gas-PHasE AtMospheric PEroxy and CriEgee RAdicaLs") starting in April 2021. This project focuses on developping instruments to observe individually the different organic radicals in the atmosphere or other complex systems, and study their reactivity.
2. Surfactants and cloud formation in Earth atmosphere
The formation of cloud droplets in Earth's atmosphere is still not entirely understood and cloud formation can still not be predicted, leading to large uncertainties in many fields of activities such as weather forecasting but also in the climate budget. In Earth atmosphere cloud droplets can only form by the condensation of water onto atmospheric aerosol particles, most of which are sub-micron in size. The role of chemical composition in the ability of such small particles to produce cloud droplets is currently an important field of investigation. Yet, an important parameter, the presence of surface-reducing compounds (or surfactants) has hardly been explored over several decades. Over the last 10 years, with my group we have developed methods to extract such compounds from atmospheric aerosols, to evidence their presence and characterize their properties (surface tension isotherm, concentration ...).
I am currently involved in several projects on the subject, in collaboration with France and Switzerland. Our current objective is to develop new techniques, for instance based on electronic microscopy, to characterize the surface tension of individual sub-micron particles.
3. Organic reactivity and aerosol formation
The formation of secondary organic aerosols in the atmosphere is an important area of investigation, as the current knowledge of this processes, based on laboratory and smog chamber experiments, underestimates the organic aerosol masses observed in the atmosphere. My activities have focused on organic reactions catalyzed by inorganic salts that are abundant in atmospheric aerosols, which could increase the organic fluxes from the gas into the particulate phase, thus the aerosol mass. I have also studied the formation of conjugated, light-absorbing products from such reactions, which are important for the optical properties of the aerosols and their contribution to climate.