Mechanism of the NO3 induced Oxidation of Terpenes in air: formation of Organic Nitrates and Secondary organic aerosol (MONOTONS)

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The nighttime oxidation of biogenically emitted terpenes is initiated to a large extent by reaction with the NO3 radical (itself mainly of anthropogenic origin) and is an important source of both organic nitrates and secondary organic aerosol (SOA). This coupling of emissions from the biosphere and anthropogenic pollutants therefore has an impact both on climate and human health. To date, a quantitative description of the complex reaction mechanisms that determine the yields of organic nitrates and secondary organic aerosol is missing for many terpenes and has not been studied experimentally in detail for multi-component systems in which more than one terpene is present, which is the situation in the real atmosphere. In order to improve our understanding of the oxidation of terpenes by the nitrate radical we propose a series of laboratory investigations using state-of-the-art analytical tools connected to a 1000 L simulation chamber. The experiments target terpenes for which data are sparse or non-existent and pairs of terpenes or terpene / isoprene mixtures for which no data is available. The experimental conditions will be varied to modify the fate of the intermediate nitrooxy-peroxy radicals formed and thus the final product distribution and yields of SOA. The two applicants, together with their working groups, have great expertise in this area and bring together a large suite of instruments to provide near-closure on the systems to be investigated including mass-spectrometric, optical and chromatographic tools for characterization of both the gas- and aerosol phases. The results obtained will give us new insight into the role of nighttime oxidation of biogenic emissions and will help analyze and interpret the data from existing field campaigns.