Short lifetimes of organic nitrates in a sub-urban temperate forest indicate efficient assimilation of reactive nitrogen by the biosphere

Abstract. Alkyl nitrates (ANs) and peroxycarboxylic nitric anhydrides (PANs) are important reservoirs of reactive nitrogen that contribute significantly to the rate of formation and growth of secondary organic aerosols and support the transport of reactive nitrogen from polluted areas to remote areas. It is therefore critical to understand their sources and sinks in different environments. In this study we use measurements of OH, O₃, NO₃ reactivity, VOCs, ∑ANs and ∑PANs during the ACROSS campaign to investigate different production and loss processes of ANs and PANs in a temperate forest. At daytime OH-initiated processes were the dominant source of ANs (69–72 %) followed by NO₃ (18–20 %) and O₃ (8–12 %). At nighttime the contribution from OH decreased to 43–53 %, and NO₃ increased to 26–40 % with that of O₃ largely unchanged. Of the measured ∑PANs, 48–78 % was modelled to be peroxyacetic nitric anhydride (PAN). Physical loss (e.g. deposition) was an important sink for both ANs and PANs and contributed significantly to the very short lifetimes of 1.5 ± 1 h for ANs and 0.08–1.5 h for PANs observed during the campaign.