Abstract
Abstract. We present a compact, affordable and robust instrument based on incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) for simultaneous detection of NOx, IO, CHOCHO and O3 in the 400–475 nm wavelength region. The instrument relies on the injection of a high-power LED source in a high-finesse cavity (F∼33 100), with the transmission signal being detected by a compact spectrometer based on a high-order diffraction grating and a charge-coupled device (CCD) camera. A minimum detectable absorption of 2.0×10-10 cm−1 was achieved within ∼22 min of total acquisition, corresponding to a figure of merit of 1.8×10-10 cm−1 Hz-1/2 per spectral element. Due to the multiplexing broadband feature of the setup, multi-species detection can be performed with simultaneous detection of NO2, IO, CHOCHO and O3 achieving detection limits of 11, 0.3, 10 ppt (parts per trillion) and 47 ppb (parts per billion) (1σ) within 22 min of measurement, respectively (half of the time is spent on the acquisition of the reference spectrum in the absence of the absorber, and the other half is spent on the absorption spectrum). The implementation on the inlet gas line of a compact ozone generator based on electrolysis of water allows for the measurement of NOx (NO+NO2) and therefore an indirect detection of NO with detection limits for NOx and NO of 10 and 21 ppt (1σ), respectively. The device has been designed to fit in a 19 in., 3U (5.25 in.) rack-mount case; weighs 15 kg; and has a total electrical power consumption of <300 W. The instrument can be employed to address different scientific objectives such as better constraining the oxidative capacity of the atmosphere, studying the chemistry of highly reactive species in atmospheric chambers as well as in the field and looking at the sources of glyoxal in the marine boundary layer to study possible implications on the formation of secondary aerosol particles.
Highlights
Free radicals are controlling the oxidative capacity of the atmosphere and contribute to the upholding of its chemical balance
The present paper describes a compact and affordable instrument based on the incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) technique, allowing for the simultaneous detection of nitrogen dioxide, iodine oxide, glyoxal and ozone (NO2, IO, CHOCHO and O3), with detection limits of 11, 0.3, 10 ppt and 47 ppb (1σ ), respectively, for a measurement time of 22 min
A compact, robust, affordable and highly sensitive IBBCEAS instrument for direct detection of NO2, IO, CHOCHO and O3 and indirect detection of NO is reported in this work
Summary
Free radicals are controlling the oxidative capacity of the atmosphere and contribute to the upholding of its chemical balance. Min et al (2016) proved a precision of 80 ppt in 5 s of integration at 455 nm using a spectrometer with a thermoelectric-cooled charge-coupled device (CCD) camera and very high-reflectivity mirrors This nonexhaustive list of works underline the need of robust, compact and transportable instruments allowing for direct multi-species detection and low detection limits for applications in remote areas such as Antarctica, where the expected mixing ratio of NO2 could be as low as a few tens of ppt. The present paper describes a compact and affordable instrument based on the IBBCEAS technique, allowing for the simultaneous detection of nitrogen dioxide, iodine oxide, glyoxal and ozone (NO2, IO, CHOCHO and O3), with detection limits of 11, 0.3, 10 ppt and 47 ppb (1σ ), respectively, for a measurement time of 22 min (half of the time is spent on the acquisition of the reference spectrum in the absence of the absorber, and the other half is spent on the absorption spectrum). IBBCEAS-NO2 and IBBCEAS-NOx, the later equipped with an ozone generator system
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