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

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 < 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.