The terrestrial biosphere (vegetation and soil) is an important source and/or sink for reactive air constituents contributing to chemical processes in the atmosphere. These relatively short-lived compounds include ozone, oxidized and reduced nitrogen and sulphur compounds, volatile organic compounds (VOC) as well as aerosols. They are important for air quality with potential impacts on ecosystems through dry and wet deposition (nutrients or toxic effect) or on human health. Some compounds also have a direct or indirect effect on the atmosphere radiative properties.
The exchange of reactive atmospheric compounds with the biosphere is more complex than for inert trace gases because it is influenced by biological, chemical (homogeneous and heterogeneous), surface sorption, and turbulent transfer processes within and above the vegetation canopy that can act on similar time scales. Due to these complex interactions as well as due to instrumental and methodological difficulties in concentration and flux measurements, there exist major uncertainties associated with the description, quantification and modelling of the processes controlling the surface-atmosphere exchange of reactive trace gases and aerosols.

The session is addressed to experimentalists and modellers working on land surface fluxes and exchange processes on the leaf, ecosystem, regional, and continental scale. It is open to a wide range of studies including the development and application of new devices, methods, and model approaches as well as field observations and process studies. Presentations concerning all types of reactive compounds and (semi-) natural or agricultural ecosystems are welcome.