A compact, high-purity source of HONO validated by Fourier transform infrared and thermal-dissociation cavity ring-down spectroscopy

Abstract

Abstract. A well-characterized source of nitrous acid vapour (HONO) is essential for accurate ambient air measurements by instruments requiring external calibration. In this work, a compact HONO source is described in which gas streams containing dilute concentrations of HONO are generated by flowing hydrochloric acid (HCl) vapour emanating from a permeation tube over continuously agitated dry sodium nitrite (NaNO2) heated to 50 ∘C. Mixing ratios of HONO and potential by-products including NO, NO2, and nitrosyl chloride (ClNO) were quantified by Fourier transform infrared (FTIR) and thermal-dissociation cavity ring-down spectroscopy (TD-CRDS). A key parameter is the concentration of HCl, which needs to be kept small (<4 ppmv) to avoid ClNO formation. The source produces gas streams containing HONO in air in >95 % purity relative to other nitrogen oxides. The source output is rapidly tuneable and stabilizes within 90 min. Combined with its small size and portability, this source is highly suitable for calibration of HONO instruments in the field.

A portable, robust, stable, and tunable calibration source for gas-phase nitrous acid (HONO)

“…environments, with levels up to 50 ppbv reported from gas stove cooking emissions (Collins et al, 2018;Gligorovski, 2016;Gómez Alvarez et al, 2012;Liu et al, 2019;Young et al, 2019;Zhou et al, 2018). There are a number of atmospheric HONO sources that have been reported: direct emissions (e.g., vehicles and biomass burning), gas-phase homogenous reaction of NO and OH, biological production in soils (Mushinski et al, 2019), and a number of heterogeneous surface reactions (Spataro and Ianniello, 2014, and references therein).…”

Development of a laser-photofragmentation laser-induced fluorescence instrument for the detection of nitrous acid and hydroxyl radicals in the atmosphere

“…This method requires the reaction chamber to be heated to 50 • C and can produce mixing ratios of HONO over a wide range (5-20 000 ppb) (Febo et al, 1995) that often require large dilution flows to reach typical outdoor atmospheric concentrations (Lao et al, 2020). Furthermore, the high HONO mixing ratios produced by this approach can disproportionate to form NO and NO 2 (Febo et al, 1995;Stutz et al, 2000;Gingerysty and Osthoff, 2020;Lao et al, 2020). As a result, this method typically requires an additional technique to verify both the purity and output concentration of HONO (Pérez et al, 2007;Gingerysty and Osthoff, 2020).…”

“…Elevated concentrations of HONO indoors are rele-vant not only due to the adverse health effects caused by inhalation (Beckett et al, 1995;van Strien et al, 2004;Jarvis et al, 2005), but also due to the potential for OH production indoors from HONO photolysis. OH concentrations were thought to be negligible indoors due to reduced light intensity, especially at short wavelengths and lower ozone mixing ratios, but several studies have indicated that photolysis of elevated indoor HONO can produce OH concentrations similar to those found outdoors, even at reduced photolysis frequencies (Gómez Alvarez et al, 2013;Bartolomei et al, 2015;Kowal et al, 2017).…”

Development of a Laser-Photofragmentation Laser-Induced Fluorescence instrument for the detection of nitrous acid and hydroxyl radicals in the atmosphere

“…Furthermore, the high HONO mixing ratios produced by this approach can disproportionate to form impurities such as NO and NO2 (Febo et al, 1995;Stutz et al, 2000;Gingerysty and Osthoff, 2020;Lao et al, 2020), and excessive amounts of HCl can result in the production of ClNO (Pérez et al, 2007;Gingerysty and Osthoff, 2020). As a result, this method typically requires an additional technique to verify both the purity and output concentration of HONO (Pérez et al, 2007;Gingerysty and Osthoff, 2020). While appropriate for a laboratory setting, these limitations, along with the long warmup times needed to ensure stability, can make this method less suitable for calibration in a field setting.…”

“…In addition to improving the sensitivity of the instrument and testing for potential interferences, future work will involve improving the stability of the beam overlap in order to improve the precision associated with the photofragmentation efficiency calibration method described above. In addition, the measured HONO sensitivity by the photofragmentation calibration method will be compared to that determined through the production of HONO by the reaction of gas-phase hydrochloric acid in a humidified gas stream with solid sodium nitrite (Febo et al, 1995;Gingerysty and Osthoff, 2020;Lao et al, 2020). While this calibration method is not as simple to implement in the field in addition to requiring quantification of the HONO produced, comparison of the instrument sensitivity derived from this calibration source in the laboratory would provide additional confidence in the calibration of the instrument by the photofragmentation method.…”