Observations of Atmospheric NO2 Using a New Low-Cost MAX-DOAS System

Abstract

This article describes the prototype of a new MAX-DOAS (multi-axis differential optical absorption spectroscopy) system built at “Dunarea de Jos” University of Galati (UGAL), Romania, and the first results of its use to observe NO2 content over Galati city (45.42° N, 28.04° E). The new equipment is a ground-based MAX-DOAS system capable of measuring the spatial distribution of DSCD (differential slant column densities) of several trace gases using horizontal and vertical observations. The new optic system, named UGAL-2-DOAS, is an in-house, low-cost, solution in comparison to the existing market of the MAX-DOAS systems. This paper describes the technical design and capabilities of the new MAX-DOAS instrument. The UGAL-2D-DOAS system was tested in April and June 2017 in Galati city. Measurements over three days were selected for the present manuscript. Full azimuthal (0–360°), local celestial meridian observations and other elevation angle sequence measurements (e.g., E–W) were performed. We found that the new MAX-DOAS system is able to detect diurnal variation and the local source emissions of NO2 from the urban environment. Also, we present concomitant zenith-sky car-DOAS observations measurements around the location of the new MAX-DOAS instrument. Comparing the horizontal scanning sequence of the new developed instrument with the mobile DOAS observations, we found that both systems can indicate and detect the same NO2 sources.

Assessment of NO2 Pollution Level during the COVID-19 Lockdown in a Romanian City

“…Galati city is located in the southeast of Romania, being in the top 10 Romanian cities by surface and population (~250,000 inhabitants distributed over 246.4 km 2 ). The main sources of atmospheric pollution in Galati city are local transportation (traffic) and some industrial activities, which contribute to local enhancements of the atmospheric NO 2 concentration [ 12 , 13 , 14 , 15 , 16 ].…”

“…The detection component of the mobile DOAS system is the spectrometer (Avantes ULS2048XL Starline, with a spectral resolution of 0.7 nm and a spectral domain ranging from 295 to 550 nm, manufactured by Avantes The Netherlands). The full specifications of the Avantes ULS2048XL Starline spectrometer and more technical details can be found in [ 12 , 13 , 14 , 15 , 17 ].…”

“…QDOAS is a free, cross-platform, and open-source software that performs DOAS retrievals of trace gases from spectral measurements (satellite, ground-based, mobile, or aircraft-based instruments). This software was validated through many DOAS applications and studies [ 5 , 12 , 13 , 14 , 15 , 16 , 21 ]. The result of the spectral analysis is a Differential Slant Column Density (DSCD).…”

Estimation of Atmospheric NO\(_2\) Volume Mixing Ratio in Hanoi Using Multi-axis Differential Optical Absorption Spectroscopy Technique

“…As a result, the detection and monitoring of the pollutant trace gases have attracted the attention of the scientific community, regulatory agency and the general public. For more than two decades the differential optical absorption spectroscopy (DOAS) method [1][2][3][4][5] has been widely used to retrieve the concentration and spatial distribution of trace gases in the atmosphere either on the ground or from space-based platforms. The DOAS technique relies on the identification and determination of minute absorption features of trace gases imprinted on the broad band continuum emission from an artificial light source such as Xenon lamp (active DOAS) or from natural light sources such as the Sun or the Moon (passive DOAS).…”

“…The spectrally resolved absorption features serve as finger prints to identify the presence of trace gases and allow the retrieval of their concentration with very high sensitivity, usually in the sub-ppb range, if the light path in the atmosphere is precisely known. More recently, the technique of multi-axis DOAS has become widely used and allowed the retrieval of vertical profiles of aerosol together with the trace gases in the atmosphere [2][3][4][5][6][7][8]. This technique relies on the measurement of the UV and visible sky spectrum representing scattered sun light at different elevation angles.…”