Abstract
Abstract. We present measurements of isoprene-derived organic nitrates (ISOP-NITs) generated in the reaction of isoprene with the nitrate radical (NO3) in a 1 m3 Teflon reaction chamber. Detection of ISOP-NITs is achieved via their thermal dissociation to nitrogen dioxide (NO2), which is monitored by cavity ring-down spectroscopy (TD-CRDS). Using thermal dissociation inlets (TDIs) made of quartz, the temperature-dependent dissociation profiles (thermograms) of ISOP-NITs measured in the presence of ozone (O3) are broad (350 to 700 K), which contrasts the narrower profiles previously observed for, for example, isopropyl nitrate (iPN) or peroxy acetyl nitrate (PAN) under the same conditions. The shape of the thermograms varied with the TDI's surface-to-volume ratio and with material of the inlet walls, providing clear evidence that ozone and quartz surfaces catalyse the dissociation of unsaturated organic nitrates leading to formation of NO2 at temperatures well below 475 K, impeding the separate detection of alkyl nitrates (ANs) and peroxy nitrates (PNs). The use of a TDI consisting of a non-reactive material suppresses the conversion of isoprene-derived ANs at 473 K, thus allowing selective detection of PNs. The potential for interference by the thermolysis of nitric acid (HNO3), nitrous acid (HONO) and O3 is assessed.
Highlights
Understanding the atmospheric fate of nitrogen oxide (NO) and nitrogen dioxide (NO2) is critical as both trace gases have a great impact on air quality and human health (Crutzen and Lelieveld, 2001; Lelieveld et al, 2015)
In the presence of O3 we find that ISOP-NIT does not behave like the saturated analogue isopropyl nitrate (iPN) in our quartz TD inlet and we characterized the processes that lead to the observed behaviour
We examined the potential role of surfacecatalysed dissociation of HNO3 and nitrous acid (HONO) to NO2 as well as the effect of humidity as a potential bias to measurements of peroxy nitrates (PNs) and alkyl nitrates (ANs)
Summary
Understanding the atmospheric fate of nitrogen oxide (NO) and nitrogen dioxide (NO2) is critical as both trace gases have a great impact on air quality and human health (Crutzen and Lelieveld, 2001; Lelieveld et al, 2015). Several instruments using thermal dissociation inlets consisting of fused silica (quartz) with residence times between tens to hundreds of milliseconds have been described in the literature (Day et al, 2002; Paul et al, 2009; Wild et al, 2014; Sobanski et al, 2016; Thieser et al, 2016; Keehan et al, 2020) In these instruments, quantitative conversion of PAN is reported for temperatures between 375 and 420 K. We generated ISOP-NITs by reacting isoprene and NO3 in a Teflon simulation chamber and used a custom-built, five-channel cavity ring-down spectrometer (CRDS) (Sobanski et al, 2016) to analyse the organic nitrates formed. We examined the potential role of surfacecatalysed dissociation of HNO3 and nitrous acid (HONO) to NO2 as well as the effect of humidity as a potential bias to measurements of PNs and ANs
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
