Simultaneous measurements of atmospheric trace gases and atmospheric visibility by DOAS system

Abstract

A Long Path Differential Optical Absorption Spectrometer (LP-DOAS) system has been developed to measure simultaneously atmospheric trace gases concentration and spectral extinction coefficient in the visible region over a few hundred meter. Concentrations of atmospheric gases; SO 2 , NO 2 , and O 3 are evaluated from the differential optical absorption spectra measured by system. Performance of the system was tested in the field over a 1500 m path length. The Differential Optical The field measurements were carried out and compared with those of a fixed monitoring system. The results show very good correlation, R 2 > 0.7, for two gas species: NO 2 , and O 3 . Atmospheric visibility is estimated by integrating the measured spectral extinction coefficient over the visible region, at 550 ± 3 nm by considering the stability of xenon lamp and transmitted light intensity. During the measurement, average exctinction is 0.51/km and average visual range is 10.1 km. The amount of PM10 and the relative humidity affect the extinction. Because of the alignment of the optic system in DOAS system all measured data did not have quantitatively significant extinction coefficients.