Stable isotopes in atmospheric gases and aerosols and other novel tracers such as COS provide powerful constraints on chemical, physical and biological processes that interact with our atmosphere. Measurement of stable isotope ratios is an established tool for investigating the processes that determine the distribution, sources and sinks of important atmospheric gases such as carbon dioxide, carbon monoxide, methane, hydrogen, nitrous oxide, sulphur dioxide and ozone. Recently, the first measurements of carbon isotope ratios in volatile organic compounds (VOCs) have become available. Meanwhile, a number of laboratory studies reported kinetic isotope effects in the reactions of VOCs with OH, Cl, and ozone. Due to the broad spectrum of compounds with a large range of atmospheric lifetimes, the recently developed isotopic hydrocarbon clock concept allows investigation of chemical and physical processes in the atmosphere. These methods have been extended to investigate particulate matter, especially secondary organic aerosols. Moreover, the discovery of non-mass dependent isotope fractionation processes in the laboratory and in nature have revolutionised the way stable isotope measurements are applied. Previously neglected minor isotope ratios such as 17O/16O, 33S/32S, 36S/32S, etc. are establishing themselves as vital tools.

The session is open to all contributions related to studies of gases in the atmosphere, field studies, laboratory and simulation experiments, novel sampling or analytical techniques, and modelling activities.

Topics addressed in this session include:
- Stable isotope ratios in atmospheric gases and aerosols
- Stable isotope ratios in the formation of aerosols from biogenic and anthropogenic VOC
- Kinetic isotope effects
- Non-mass dependent isotopic fractionation and related isotope anomalies
- Poly-substituted isotopocules ("clumped isotopes")
- Stable isotope ratios in the past, present and future atmosphere
- Novel tracers such as carbonyl sulphide (COS) as analogue to carbon dioxide and tracer of one-way fluxes
- Biosphere-atmosphere interactions using tracers (natural abundance and label) at the soil-plant-atmosphere interface