SAPHIR provides a platform for reproducible studies of the atmospheric degradation of biogenic and anthropogenic trace gases and the build-up of secondary particles and pollutants. SAPHIR is a National Facility of the Research Infrastructure ACTRIS.
The chemical and physical processes leading to secondary pollutants such as ozone and particulate matter are challenging to describe in chemical models. Such secondary pollutants are formed by the chemical transformation of emitted compounds from both biogenic and anthropogenic activities and involve a large number of highly reactive short-lived species. SAPHIR is a unique facility as it allows these reactions to be studied in a controlled environment using low concentrations of reactants, so that the competing of all relevant reaction pathways can be observed like in the real atmosphere. New chemical pathways, currently missing in chemical mechanisms, can be therefore probed and results can be included in models to improve our ability to make prediction about air quality and climate.
The outdoor chamber is of cylindrical shape (diameter: 5m, length: 18m, volume: 270m3) made of a double-wall Teflon film and has a shutter system that can be quickly opened and closed to expose the air mixtures to sunlight. The high purity of the air supply and the large volume to surface ratio allows running experiments at low, atmospheric concentrations of trace gases with only minor influences of chamber wall interactions, so that the transformation of trace gases and aerosol can be observed over a long period up to several days.
Experiments in SAPHIR can be used using single pre-cursor species that are emitted by biogenic or anthropogenic activities, but also realistic mixtures can be studied, such as emissions from plants (SAPHIR-PLUS) or ambient air that can be sampled from a 50m high inlet line (the JULIAC-tower). The SAPHIR chamber is also used for quality assurance of instruments serviced by ACTRIS Topical Centers such as CiGAS.
The SAPHIR chamber is equipped with a comprehensive, unique set of sensitive instruments for radicals, traces gases, aerosols, and physical parameters. It is the only chamber equipped with instruments to measure extremely short-lived intermediate species required to determine the formation rate of secondary pollutants.
These radicals are detected by differential optical absorption spectrometer (OH), which is worldwide the only absolute measurement device for OH radicals, laser induced fluorescence (LIF-FAGE for OH, HO2, RO2, and OH reactivity) and cavity ring-down spectroscopy (NO3, N2O5). Organic species including oxygenated species are measured by mass spectrometer instruments using different ionization methods including proton-transfer mass spectrometer (PTR-TOF-MS). In addition, organic species are measured by gas chromatography. Aerosol properties are characterized by a high-resolution aerosol mass spectrometer (WToF-AMS, size resolved chemical composition), CPCs, SMPS and cloud condensation nuclei counter. Inorganic species (NO, NO2, O3, HONO) and also physical parameters are permanently monitored.
Deputy Director of ICE-3
Senior Scientist Head of group "Photochemistry and Radicals"
