Motivation Fundamental understanding of surface chemical processes in the atmosphere Assessment of the impact of human activities and natural processes on human health, environment and climate

Highlights of ongoing research

Processes on Ice and in Snow
Chemical reactions in the snow cover and in ice clouds have the capacity to modify the composition of the snow or ice, as well as of the surrounding or over-laying air. In our research, we mainly focus on the exchange of trace gases between the two phases. Using radioactively labeled molecules -produced at PSI's PROTRAC facility- we look at adsorption of trace gases on the ice surface, bulk diffusion and gas-phase diffusion in the interstitial air of snow. We also use X-Ray Spectroscopy tools to get a molecular level picture of structural and chemical properties of the ice surface as affected by adsorption of trace gases.

Reactions driven by light
Light is an important driver of chemical reactions in the atmosphere. In several joint laboratory campaigns with the University of Wuppertal and the University in Lyon we investigated how condensed organic matter reacts with atmospheric trace gases such as nitrogen dioxide under irradiation with visible light. This is of importance as the product of this reaction, HONO, has an influence on air quality.

Reactions with aerosol particles
The aging of aerosol, that is how the composition and properties of aerosol change with time, is of interest as both influence the radiative properties of the atmosphere. Aging can be invoked, for example, by interaction of aerosol with atmospheric trace gases such as ozone and nitrogen dioxide. In our research we focus on determining the rates of these reactions. Another aspect of our research is the phase state and morphology of aerosol under atmospheric conditions. To tackle these questions we use an aerosol flow tube reactor and X-ray microscopy.