Our research activities focus on atmospheric chemistry, mainly aqueous phase chemistry (clouds, fogs and rain), atmospheric particulate matter and particle droplet interactions. We are also interested in the impact of particle and cloud chemistry on local, regional (public health, visibility, deposition fluxes) and global scale (effects on Earth's radiative budget). All our research relies largely on environmental analytical chemistry and involves field campaigns to collect samples and study processes in situ. Ongoing projects include: The characterization of aerosol, cloud and fog composition. We are especially interested in composition differences related to the droplet or particle size. The goal of these studies is to investigate the processing of atmospheric particles and gases by clouds and fogs: What particles/gases are scavenged? What happens to them in the aqueous phase? What is the net impact of these processes on the atmospheric composition? The characterization of organic matter in the atmosphere. Usually less than 20% of the carbonaceous material in atmospheric particles is known at a molecular lever. We work on developing new analytical techniques to enhance the speciated fraction. We are also characterizing bulk properties of organic matter including its size, its polarity and the presence of functional groups in order to predict the impact on aqueous phase chemistry and on physico-chemical properties like surface tension. Laboratory studies of aqueous phase chemistry involving organic compounds in atmospherically relevant conditions. We are currently evaluating atmospheric organic molecular marker stability. While organic molecular markers are widely used to apportion the source of carbonaceous particles in the atmosphere, surprisingly little is known about their stability and atmospheric lifetimes. Our research investigates the degradation of these molecules in laboratory experiments under conditions simulating atmospheric droplets (haze, clouds, fogs).