Day and night-time formation of organic nitrates at a forested mountain site in south-west Germany

Abstract

Abstract. We report in situ measurements of total peroxy nitrates ( PNs) and total alkyl nitrates ( ANs) 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 PNs and ANs over continental Europe. We find that a significant fraction of NO x (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 NO 3 with biogenic hydrocarbons is comparable to that from daytime OH-initiated oxidation pathways. The ANs / 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.

Chemical ionization quadrupole mass spectrometer with an electrical discharge ion source for atmospheric trace gas measurement

“…The line intensities increase with the voltage applied (≈ factor of 2.5 from 1500 to 3000 V), but the relative intensities do not change significantly. From the relative line intensities we calculate that the N 2 molecules have a vibrational temperature of ≈ 3000 K (Svarnas, 2013).…”

Characterization of nighttime formation of particulate organic nitrates based on high-resolution aerosol mass spectrometry in an urban atmosphere in China

“…Several direct methods have been developed to measure total organic nitrates (gas + particle) in the real atmosphere. For example, Rollins et al(2012) used a thermal-dissociation laser-induced fluorescence technique (TD-LIF) to observe total organic nitrates in the United States; Sobanski et al (2017) obtained organic nitrates in Germany using the thermal dissociation cavity ring-down spectroscopy (TD-CRDS). However, it is still difficult to identify and quantify the particle phase organic nitrates, which could contribute a large portion of secondary organic aerosol (SOA) (Rollins et al, 2012;Xu et al, 2015a;Fry et al, 2013;Ayres et al, 2015;Boyd et al, 2015;Lee et al, 2016), using these direct measurement methods.…”

Evidence of Nighttime Production of Organic Nitrates During SEAC4RS, FRAPPÉ, and KORUS‐AQ

“…A number of recent studies have shown that NO 3 oxidation can be a significant source of RONO 2 in regions dominated by biogenic VOC emissions. In forested regions of Colorado, Finland, and Germany, nighttime concentrations of RONO 2 were found to be comparable with daytime RONO 2 concentrations (Fry et al, 2013; Liebmann et al, 2019; Sobanski et al, 2017). Other studies have found NO 3 ‐initiated formation of isoprene nitrates to be competitive with OH‐initiated formation of isoprene nitrates in the Southeastern United States (Starn et al, 1998; Xiong et al, 2015), in an observationally constrained model of the eastern United States (Horowitz et al, 2007), and in a global model (von Kuhlmann et al, 2004).…”