Abstract
Abstract. We report in situ measurements of total peroxy nitrates (ΣPNs) and total alkyl nitrates (ΣANs) in a forested–urban location at the top of the Kleiner Feldberg mountain in south-west Germany. The data, obtained using thermal dissociation cavity ring-down spectroscopy (TD-CRDS) in August–September 2011 (PARADE campaign) and July 2015 (NOTOMO campaign), represent the first detailed study of ΣPNs and ΣANs over continental Europe. We find that a significant fraction of NOx (up to 75 %) is sequestered as organics nitrates at this site. Furthermore, we also show that the night-time production of alkyl nitrates by reaction of NO3 with biogenic hydrocarbons is comparable to that from daytime OH-initiated oxidation pathways. The ΣANs ∕ ozone ratio obtained during PARADE was used to derive an approximate average yield of organic nitrates at noon from the OH initiated oxidation of volatile organic compounds (VOCs) of ∼ 7 % at this site in 2011, which is comparable with that obtained from an analysis of VOCs measured during the campaign. A much lower AN yield, < 2 %, was observed in 2015, which may result from sampling air with different average air mass ages and thus different degrees of breakdown of assumptions used to derive the branching ratio, but it may also reflect a seasonal change in the VOC mixture at the site.
Highlights
The gas- and aerosol-phase chemistry of the continental, tropospheric boundary layer is strongly influenced by reactive nitrogen oxides
NO undergoes a series of reaction steps that lead either to the formation of shortlived trace gases that can act as sinks for NOx (e.g. HNO3) or to the formation of longer-lived reservoir species that can be transported over long distances and act as a source of NOx (e.g. RONO2 and RC(O)OONO2) in locations that are remote from anthropogenic emissions
By measuring total organic nitrates NO, NO2, and NO3, we have shown that a significant fraction of NOx is sequestered as gas-phase organic nitrates at this forested site with urban influence
Summary
The gas- and aerosol-phase chemistry of the continental, tropospheric boundary layer is strongly influenced by reactive nitrogen oxides. Attempts to compare total reactive nitrogen NOy (where NOy = NOx + RO2NO2+ RONO2+ HNO3+ HONO ++) with the sum of individually measured species (Fahey et al, 1986; Buhr et al, 1990; Ridley et al, 1990) revealed that a substantial fraction of NOy was missing This phenomenon was addressed by the first measurements of total peroxynitrates ( PNs) and total alkyl nitrates ( ANs) by thermal dissociation coupled with laser-induced fluorescence detection of NO2 (Day et al, 2003). The results from the two campaigns are compared and differences are discussed in terms of annual and seasonal changes in meteorology and VOC (biogenic and anthropogenic)
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 call
