The experimental investigation of atmospheric trace gas cycles with isotope techniques

Our group operates a large atmospheric chemistry laboratory dedicated to isotope ratio measurements on atmospheric trace species. The core analytical facilities are seven isotope ratio mass spectrometers (IRMS), including a high resolution isotope ratio mass spectrometer (253 Ultra high resolution IRMS), and in addition a cavity ring-down spectrometer (CRDS) for isotope measurements. These systems are high precision detectors for isotope ratio measurements that are coupled to a wide range of custom made preparation and extraction devices to determine the isotopic composition of various trace gases including CO₂, CH₄, N₂O, CO, H₂, some volatile organic compounds, some CFC's and aerosols. With this special expertise, our research group participates in many national and international projects, where we are often responsible for the isotope measurements. We analyze air samples that are collected at many different locations on the globe, including surface stations, aircraft, stratospheric balloon flights, but also air stored in polar firn and ice. We also carry out laboratory experiments to study isotope effects in specific reactions.

Trace species that are emitted from different sources usually have a slightly different isotopic composition that is characteristic for that source. Therefore, isotope measurements can be used to distinguish the emissions from the different sources. Also atmospheric removal reactions leave a fingerprint in the isotopic composition, which is characteristic for different removal process. Isotope measurements can thus provide information on the global and regional cycling of trace gases. They provide information on individual source and sink processes, which is often not achievable by measuring the concentration alone. Since this is a general property of isotope research, this approach has a very wide range of applications, also outside of atmospheric research.