An IBBCEAS system for atmospheric measurements of glyoxal and methylglyoxal in the presence of high NO<sub>2</sub> concentrations

Abstract

Abstract. A system based on incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) has been developed for simultaneous measurement of nitrogen dioxide (NO2), glyoxal (GLY), and methylglyoxal (MGLY). In this system, the measured light absorption at around 460 nm is spectrally resolved. The concentration of absorbers is determined from a multicomponent fit. At an integration time of 100 s, the measurement sensitivity (2σ) for NO2, GLY, and MGLY is 18, 30, and 100 ppt, respectively. The measurement uncertainty, which mainly originates from path length calibration, sampling loss, and uncertainty of absorption cross sections is estimated to be 8 % for NO2, 8 % for GLY, and 16 % for MGLY. When deploying the instrument during field observations, we found significant influence of NO2 on the spectra fitting for retrieving GLY and MGLY concentrations, which is caused by the fact that NO2 has a higher absorption cross section and higher ambient concentration. In order to minimize such an effect, a NO2 photolytic convertor (NPC), which removes sampled NO2 at an efficiency of 76 %, was integrated on the IBBCEAS system. Since sampled GLY and MGLY are mostly (≥95 %) conserved after passing through the NPC, the quality of the spectra fitting and the measurement accuracy of ambient GLY and MGLY under NO2-rich environments could be improved.

Advances in High-Precision NO2 Measurement by Quantum Cascade Laser Absorption Spectroscopy

“…The ∆NO 2, CAPS day/night time variations are stronger during the first part of the campaign that is impacted by higher ozone mixing ratios, which is a sign for stronger photo-chemistry. Previous studies have shown that dialdehydes absorb light in the wavelength range used by the CAPS instrument to detect NO 2 [48,49]. The dominant ones in the troposphere, glyoxal and methyl-glyoxal, are produced by photo-chemical oxidation of hydrocarbons (mostly isoprene [50]), which is the same mechanism that drives the formation of ozone during daytime.…”

Reply on RC1

“…The CEAS system has been described in detail in previous literature (Duan et al, 2018;Fiedler et al, 2003;Gherman et al, 2008;Jordan and Osthoff, 2020;Jordan et al, 2019;Langridge et al, 2006;Liang et al, 2019;Liu et al, 2019;Min et al, 2016;Tang et al, 2020;Ventrillard-Courtillot et al, 2010;Wang et al, 2017a;Yi et al, 2016), so there is a brief introduction to the principle of the instrument. NO2 molecules have a specific absorption structure in the wavelength range of 400-500 nm (Fig.…”

“…The fitting shift is constrained within ±0.2 nm. Glyoxal has strong absorption in the same optical window (Liu et al, 2019;Min et al, 2016;Thalman et al, 2015;Thalman and Volkamer, 2010;Washenfelder et al, 2008), but here we do not take into consideration in spectrum fitting. Fig.…”

A compact incoherent broadband cavity-enhanced absorption spectrometer for trace detection of nitrogen oxides, iodine oxide and glyoxal at levels below parts per billion for field applications

“…in min) is challenging and puts stringent constraints on the instrument sensitivity, time response, energy consumption and compactness. Among the various techniques that have so far been developed, chemiluminescence detection (CLD) (Maeda et al, 1980;Ryerson et al, 2000), long-path differential optical absorption spectroscopy (LP-DOAS) (Lee et al, 2005(Lee et al, , 2008Pikelnaya et al, 2007) and multi-axis differential optical absorption spectroscopy (MAX-DOAS) (Platt and Perner, 1980;Sinreich et al, 2007;Wagner et al, 2010) have been used to detect nitrogen species and halogen oxides. The CLD technique, using the chemiluminescence reaction occurring between O 3 and NO after the reduction of NO 2 into NO, is widely used for air quality measurements with sensitivities better than 100 ppt (Ryerson et al, 2000).…”