Monitoring of atmospheric nitrogen dioxide by long-path pulsed differential optical absorption spectroscopy using two different light paths

Abstract

Measurements of the local distribution of atmospheric nitrogen dioxide (NO(2)) by long-path pulsed differential optical absorption spectroscopy (LP-PDOAS) in Tokyo during August 2008 are presented. Two LP-PDOAS systems simultaneously measured average NO(2) temporal mixing ratios along two different paths from a single observation point. Two flashing aviation obstruction lights, located 7.0 km north and 6.3 km east from the observation point, were used as light sources, allowing spatiotemporal variations of NO(2) in Tokyo to be inferred. The LP-PDOAS data were compared with ground-based data measured using chemiluminescence. Surface wind data indicated that large inhomogeneities were present in the spatial NO(2) distributions under southerly wind conditions, while northerly wind conditions displayed greater homogeneity between the two systems. The higher correlation in the NO(2) mixing ratio between the two LP-PDOAS systems was observed under northerly wind conditions with a correlation factor R(2) = 0.88. We demonstrated that the combined deployment of two LP-PDOAS systems oriented in different directions provides detailed information on the spatial distribution of NO(2).

Simultaneous Monitoring of Nitrogen Dioxide and Aerosol Concentrations with Dual Path Differential Optical Absorption Spectroscopy

“…The measurements employed two independent DOAS paths having optical path lengths of 5.5 and 3.5 km that cover different areas in the central part of Chiba City, located along the eastern coast of the Tokyo Bay. The use of such dual light paths in DOAS has recently been reported for an urban air pollution study in Tokyo [14] as well as for the monitoring of volcanic gas concentration [15]. In addition, the novel aspect of the present paper is the simultaneous measurement using a Doppler wind lidar [22], which can provide more direct information on the wind field as compared with the weather station data.…”

Near-infrared open-path measurement of CO_2 concentration in the urban atmosphere

“…Visible or near ultraviolet spectral regions have usually been exploited for conventional DOAS measurements of pollutant gases [11][12][13][14][15]. In contrast, the present Letter describes the application of near-infrared (NIR) spectroscopy for the DOAS-type open path measurement of CO 2 concentration in an urban environment.…”

“…The data analysis procedure is similar to the case of standard DOAS analysis [11][12][13]. Only the outline of the derivation process is described here.…”