EGU General Assembly 2020
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the Creative Commons Attribution 4.0 License.

The effect of NOx on formation of Highly Oxidized Multifunctional Molecules and SOA formation in photochemical system of α-pinene and β-pinene

Sungah Kang1, Thomas Mentel1, Iida Pullinen1,2, Monika Springer1, Einhard Kleist3, Sebastian Schmitt4, Cheng Wu5, Silvia Proff1, Luc Vereecken1, Jürgen Wildt1, and Astrid Kiendler-Scharr1
Sungah Kang et al.
  • 1Institute for Energy and Climate Research (IEK-8), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
  • 2Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
  • 3Institute of Bio- and Geosciences (IBG-2), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
  • 4TSI GmbH, 52068 Aachen, Germany
  • 5Department of Environmental Science, Stockholm University, 11418 Stockholm, Sweden

Highly oxygenated organic molecules (HOM) are formed in the atmosphere by autoxidation, i.e. peroxy radicals can undergo H-shift followed by O2 addition. A sequence of these very fast steps leads to highly oxygenated peroxy radicals (HOM-RO2) and finally to stable termination products with O/C>1.
As other RO2, HOM-RO2 are terminated by reactions with RO2, HO2 and NOx and in addition form efficiently stable accretion products. In this study, three noticeable effects on HOM formation were found by introducing NOx in the photochemical system of monoterpenes. One effect is formation of highly oxygenated organic nitrates (HOM-ON) with sufficiently low vapor pressures allowing significant contributios to SOA formation. The second one is dimer suppression, because of competing dimer pathway (HOM-RO2·+ RO2·) and organic nitrate pathway (HOM-RO2·+ NOx). Thirdly, the reaction between peroxy radicals and NO increases alkoxy radicals in the system. The fragmentation of alkoxy radicals produces volatile compounds that should result in decrease of SOA yield. However, the effect of fragmentation is offset: alkoxy radicals also undergo H-shifts that produce alkyl radicals and after O2 addition peroxy radicals, that eventually are higher oxygenated.

Because of their low volatility, HOM play a crucial role in new particle formation and secondary organic aerosol (SOA) formation. Suppression of dimers and increased degree of oxidation of the HOM monomer play together with the result of only a small reduction of the SOA yields.

How to cite: Kang, S., Mentel, T., Pullinen, I., Springer, M., Kleist, E., Schmitt, S., Wu, C., Proff, S., Vereecken, L., Wildt, J., and Kiendler-Scharr, A.: The effect of NOx on formation of Highly Oxidized Multifunctional Molecules and SOA formation in photochemical system of α-pinene and β-pinene, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8308,, 2020.


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