Nachweis von oxidierten Stickstoffverbindungen mit einem DOAS -Spektrometer der 2. Generation Abschlussbericht

The Differential Optical Absorption Spectroscopy (DOAS) has become a widely used method to measure trace gases in the atmosphere. DOAS-systems normally employ slotted disk arrangements, where a narrow slit scans the spectrum produced by a spectrometer. With photodiode array detectors (PDA) it is possible to record all wavelength in the observed interval simultaneously. But unfortunately these detectors show much higher residual structures. It was the aim of this project to eliminate these structures and thus make this kind of detectors useable for the measurement of atmospheric trace gases. It could be showned that the angular dependence of the PDA response is responsible for the higher residual structure. With the development of a quartz fiber mode mixer it was possible to eliminate the residual structure. Furthermore the possibility of the use of CCD-cameras have been tested in field and laboratory-measurements. A new algorithm for the analysis of atmospheric absorption spectra was developed. The algorithm corrects differences in the wavelength-pixel mapping of the spectra, caused by temperature changes of the spectrometer. It also estimates the errors of the concentrations considers the uncertainty of this correction and the influence of random residual structures. Thus it allows (1) much more sensitive measurements and (2) a realistic calculation of the error of these measurements. (orig.)Available from TIB Hannover: F97B254+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman