Stable isotopes of carbon, hydrogen, and oxygen in atmospheric trace gases provide a powerful constraint on chemical, physical, and biological processes that affect our atmosphere. Measurement of stable isotope ratios is by now an established tool to gain insight into the processes determining the distribution, sources, and sinks of important atmospheric trace gases such as carbon dioxide, carbon monoxide, methane, hydrogen, nitrous oxide and ozone. Recently, first measurements of carbon isotope ratios in volatile organic compounds have been done. Meanwhile, a number of laboratory studies reported kinetic isotope effects in the reaction of VOC with OH, Cl, and ozone. Due to the broad spectrum of compounds with a large range of atmospheric life times, the recently developed isotopic hydrocarbon clock concept allows to get further information on chemical and physical processes in the atmosphere. Presently, these methods are also extended to investigate particulate matter, especially secondary organic aerosols. As a result, the combination of conventional and stable isotope techniques will significantly advance our understanding of the behaviour of trace compounds in the atmosphere.
The session is open to all contributions related to stable isotope studies of trace gases in the atmosphere, to field studies, laboratory and simulation experiments, technical developments, as well as modeling activities regarding stable isotopes as tracers of atmospheric processes.

Topics which should be addressed in this session are:
- Stable isotope ratios in atmospheric trace gases
- Kinetic isotope effects
- Field and simulation experiments
- Model studies including stable isotope ratios
- Stable isotope ratios in the formation of aerosols from biogenic and anthropogenic VOC
- Technical developments (sampling techniques, analytical techniques etc.)