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UP: Fachverband Umweltphysik
UP 4: Poster Session
UP 4.4: Poster
Tuesday, March 8, 2016, 16:00–17:30, Foyer H41
Development of a 3-channel CE-DOAS system — •Miriam Reh, Martin Horbanski, Stefan Schmitt, Denis Pöhler, and Ulrich Platt — Institut für Umweltphysik, Heidelberg
Halogens, despite their low concentration, influence the atmosphere in a number of ways, e.g. broadening of the ozone hole. Due to their high reactivity, measurements become difficult. A sensitive, contact-free method to measure small concentrations is Differential Optical Absorption Spectroscopy (DOAS), separating narrow band absorption structures of the trace gas species from the broad band absorption of aerosols.
Our aim is to develop a Cavity Enhanced DOAS (CE-DOAS) system, using an open resonator of a length of 2m and a new calibration technique, called Integrated Calibration by means of Optical Modulation (ICOM). Here ICOM is an optically direct method to retrieve the path length L(λ) of the light passing through the resonator. By the usage of phase modulation measurements the hurdle of low time resolution spectrometers (typically ms) is overcome.
To measure the concentration of several trace gas species, 3 systems, each with a different high power LED and thus suitable for different trace gases (BrO, OClO, IO, OBrO, NO2, I2, OIO), are combined. This allows for simultaneous concentration determination, which is needed to follow the interaction of different halogen species.
Finally the instrument could be used in atmospheric simulation chambers to study chemical transformation in volcanic plumes and for experimentation on halogen gas flux across the sea ice boundary.