Significant concentrations of nitryl chloride observed in rural continental Europe associated with the influence of sea salt chloride and anthropogenic emissions

Abstract

We present the first measurements of nitryl chloride (ClNO2) over continental Europe. Significant quantities of ClNO2, up to 800 pptv, were measured at a mountaintop field site in Hessen, southwest Germany. ClNO2 was detected during the majority of nights between the 15th August and 16th September 2011, its largest mixing ratios being associated with air masses influenced by sea salt and anthropogenic NOx emissions. ClNO2 persisted in measurable quantities until early afternoons on days with low photolysis frequencies. As a consequence, early morning production rates of Cl atoms could significantly exceed the production of OH via ozone photolysis, likely leading to increased O3 production.

Production of N<sub>2</sub>O<sub>5</sub> and ClNO<sub>2</sub> in summer in urban Beijing, China

“…These results indicated ubiquitously observed ClNO 2 in the NCP, although high ClNO 2 mixing ratios have also been previously observed in both marine and continental environments in North America, Europe, and Asia Mielke et al, 2011;Thornton et al, 2010;Phillips et al, 2012;Tham et al, 2014). The average nitrate radical production rate p(NO 3 ) was 2.8 and 3.6 ppbv h −1 during P1 and P2, respectively, which are both higher than those during P3 and P4 (1.7-2.6; Table 1).…”

“…Phillips et al (2012) also reported large variability in N 2 O 5 and ClNO 2 correlations and ClNO 2 /N 2 O 5 ratios in air masses from continental or marine origins due to the changes in particle Cl − . In this study, ClNO 2 was well and positively correlated with N 2 O 5 during all four nights (Fig.…”

“…A large amount of ClNO 2 was first observed in polluted coastal regions owing to the abundant chloride from sea salt aerosol, for example in the Gulf of Mexico and the Los Angeles basin Riedel et al, 2012;Kercher et al, 2009). High levels of ClNO 2 from anthropogenic chloride sources were also reported in some inland areas (Thornton et al, 2010;Mielke et al, 2011;Phillips et al, 2012Phillips et al, , 2016Bannan et al, 2015). More recently some studies in Hong Kong Brown et al, 2016a;Wang et al, 2016) and in the North China Plain (NCP; Tham et al, 2016;Wang et al, 2018) observed consistently high mixing ratios of N 2 O 5 and ClNO 2 .…”

“…Although NO 3 and N 2 O 5 levels can be suppressed by the rapid titration of NO 3 against NO and volatile organic compounds (VOCs) in urban areas (Brown et al, 2003b), heterogeneous uptake by aerosol particles, fog, and cloud droplets is often found to be the major pathway for direct N 2 O 5 removal (Bertram and Thornton, 2009;Wagner et al, 2013;Brown et al, 2006;Chang et al, 2011;Thornton et al, 2003). N 2 O 5 can produce nitryl chloride (ClNO 2 ) on chloride-containing aerosols, which serves as an important reservoir of NO x (Finlayson-Pitts et al, 1989;Thornton et al, 2010;Phillips et al, 2012). It has been found that levels of particulate nitrate formed through the hydrolysis of N 2 O 5 at nighttime were comparable to those produced from the reaction of NO 2 with the OH radical during daytime (Geyer et al, 2001).…”

Direct measurement of NO<sub>3</sub> reactivity in a boreal forest

“…ClNO 2 ) resulting from the heterogeneous reactions of N 2 O 5 with chloride containing particles (Osthoff et al, 2008;Thornton et al, 2010;Phillips et al, 2012;Ammann et al, 2013;Phillips et al, 2016).…”