A broadband cavity enhanced absorption spectrometer for aircraft measurements of glyoxal, methylglyoxal, nitrous acid, nitrogen dioxide, and water vapor

Abstract

Abstract. We describe a two-channel broadband cavity enhanced absorption spectrometer (BBCEAS) for aircraft measurements of glyoxal (CHOCHO), methylglyoxal (CH 3 COCHO), nitrous acid (HONO), nitrogen dioxide (NO 2 ), and water (H 2 O). The instrument spans 361-389 and 438-468 nm, using two light-emitting diodes (LEDs) and a single grating spectrometer with a charge-coupled device (CCD) detector. Robust performance is achieved using a custom optical mounting system, high-power LEDs with electronic on/off modulation, high-reflectivity cavity mirrors, and materials that minimize analyte surface losses. We have successfully deployed this instrument during two aircraft and two ground-based field campaigns to date. The demonstrated precision (2σ ) for retrievals of CHOCHO, HONO and NO 2 are 34, 350, and 80 parts per trillion (pptv) in 5 s. The accuracy is 5.8, 9.0, and 5.0 %, limited mainly by the available absorption cross sections.

OH reactivity at a rural site (Wangdu) in the North China Plain: contributions from OH reactants and experimental OH budget

“…In addition, three custom-built instruments applied cavity-enhanced absorption spectroscopy (CEAS) for the detection of HONO. They were operated by the US National Oceanic and Atmospheric Administration (NOAA) (Min et al, 2016), by the Anhui Institute of Optics and Fine Mechanics (AIOFM), and by the University of Shanghai for Science and Technology (USST). A gas and aerosol collector (GAC), which is based on the wet denuder/ion chromatography technique, could also detect HONO (Dong et al, 2012).…”

Non-methane organic gas emissions from biomass burning: identification, quantification, and emission factors from PTR-ToF during the FIREX 2016 laboratory experiment

“…Wavelength-resolved gas-phase extinction was measured in two spectral regions, one in the UV (361 to 390 nm) and one in the blue (438-468 nm), and then fit using literature cross sections to retrieve the concentrations of NO 2 , HONO, methylglyoxal, and glyoxal (Min et al, 2016).…”

Development of a portable cavity-enhanced absorption spectrometer for the measurement of ambient NO<sub>3</sub> and N<sub>2</sub>O<sub>5</sub>: experimental setup, lab characterizations, and field applications in a polluted urban environment

“…In previous work, R(λ) had been determined through four different methods, including the detection of a stable trace gas compound with known concentrations (Venables et al, 2006), the differentiation of pure gases with distinct Rayleigh scattering cross sections (Chen and Venables, 2011;Washenfelder et al, 2016;Min et al, 2016), the usage of low-loss optics (Varma et al, 2009), and the determination of the phase shift or ring down time (Langridge et al, 2008;Schuster et al, 2009;Kennedy et al, 2011). In this study, R(λ) is determined through the differentiation of pure gases (N 2 and He) in the cavity (Eq.…”

“…CRDS has high temporal and spatial resolution with high sensitivity and accuracy. Cavity-enhanced absorption spectroscopy (CEAS) was proposed later by Fiedler et al (2003) and has been successfully deployed to measure a number of atmospheric trace gas compounds like HONO, H 2 O, IO, O 3 , O 4 , I 2 , IO, OIO, SO 2 , NO 3 , N 2 O 5 , glyoxal (CHOCHO), and methylgloxal (CH 3 COCHO; Washenfelder et al, 2008Washenfelder et al, , 2013Washenfelder et al, , 2016Thalman and Volkamer, 2010;Gherman et al, 2008;Axson et al, 2011;Kahan et al, 2012;Min et al, 2016). The measurement of NO 3 was shown to be successful in simulation chamber conditions with an open-path incoherent broadband CEAS setup (Venables et al, 2006;Varma et al, 2009), and shortly afterwards, the closed cavity type of IBBCEAS was successfully deployed on the ground (Langridge et al, 2008;Benton et al, 2010) and airborne (Kennedy et al, 2011) for measurements of both NO 3 and N 2 O 5 .…”