Day- and Night-time Formation of Organic Nitrates at a Forested
Mountain-site in South West Germany
Abstract. We report in-situ measurement of total peroxy-nitrates (ƩPNs) and total alkyl nitrates (ƩANs) 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–August 2015 (NOTOMO campaign), represent the first detailed study of ƩPNs and ƩANs over continental Europe. We find that a significant fraction of NOx (up to 75 %) is sequestered as organics nitrates at this site. Futher, we also show that the night-time production of alkyl nitrates by reaction of NO3 with biogenic hydrocarbons is comparable to that from day-time, OH-initiated oxidation pathways. The ƩANs-to-ozone ratio obtained during PARADE was used to derive an approximate, average yield of organic nitrates at noon time from the OH initiated oxidation of VOCs of 7 % at this site in 2011, which is comparable with that obtained from an analysis of VOCs at the site. A much lower yield,