Molecular composition and volatility of multi-generation products formed from isoprene oxidation by nitrate radical
- 1Institute of Energy and Climate Research, Troposphere (IEK-8), Forschungszentrum Jülich GmbH, 52428 Jülich, Germany
- 2College of Environmental Sciences and Engineering, State Key Joint Laboratory of Environmental Simulation and Pollution Control, Peking University, 100871, Beijing, China
- 3Department of Chemistry and Molecular Biology, University of Gothenburg, 41296, Gothenburg, Sweden
- 4Department of Atmospheric and Oceanic Sciences & Institute of Atmospheric Sciences, Fudan University, 200438, Shanghai, China
- 5Atmospheric Chemistry Department, Max Planck Institut für Chemie, 55128 Mainz, Germany
- 6Institut de Combustion, Aérothermique, Réactivité et Environnement (ICARE), UPR CNRS, 45071 Orléans, France
- 7Department of Chemistry, Reed College, Portland, OR 97202, USA
- 8Department of Atmospheric Sciences, University of Washington, Seattle, WA 98195, USA
- 9NOAA Chemical Sciences Laboratory, Boulder, CO 80305, USA
- 10Department of Chemistry, University of Colorado, Boulder, CO 80309, USA
- apresent address: SOLIDpower GmbH, 52525 Heinsberg, Germany
Abstract. Isoprene oxidation by nitrate radical (NO3) is a potentially important source of secondary organic aerosol (SOA). It is suggested that the second or later-generation products are the more substantial contributors to SOA. However, there are few studies investigating the multi-generation chemistry of isoprene-NO3 reaction, and information about the volatility of different isoprene nitrates, which is essential to evaluate their potential to form SOA and determine their atmospheric fate, is rare. In this work, we studied the reaction between isoprene and NO3 in the SAPHIR chamber (Jülich) under near atmospheric conditions. Various oxidation products were measured by a high-resolution time-of-flight chemical ionization mass spectrometer using Br− as the reagent ion. They are grouped into monomers (C4- and C5-products), and dimers (C10-products) with 1–3 nitrate groups according to their chemical composition. Most of the observed products match expected termination products observed in previous studies, but some compounds such as monomers and dimers with three nitrogen atoms were rarely reported in the literature as gas-phase products from isoprene oxidation by NO3. Possible formation mechanisms for these compounds are proposed. The multi-generation chemistry of isoprene and NO3 is characterized by taking advantages of the time behavior of different products. In addition, the vapor pressures of diverse isoprene nitrates are calculated by different parametrization methods. An estimation of the vapor pressure is also derived from their condensation behavior. According to our results, isoprene monomers belong to intermediate volatility or semi-volatile organic compounds and thus have little effect on SOA formation. In contrast, the dimers are expected to have low or extremely low volatility, indicating that they are potentially substantial contributors to SOA. However, the monomers constitute 80 % of the total explained signals on average, while the dimers contribute less than 2 %, suggesting that the contribution of isoprene NO3 oxidation to SOA by condensation should be low under atmospheric conditions. We expect a SOA mass yield of about 5 % from the wall loss and dilution corrected mass concentrations, assuming that all of the isoprene dimers in the low- or extremely low-volatility organic compound (LVOC or ELVOC) range will condense completely.
Rongrong Wu et al.
Rongrong Wu et al.
Rongrong Wu et al.
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