EGU21-11130
https://doi.org/10.5194/egusphere-egu21-11130
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Investigating the NO-dependent photooxidation of limonene by OH and O3 using the atmosphere simulation chamber SAPHIR

Yat Sing Pang1, Martin Kaminski1,3, Anna Novelli1, Philip Carlsson1, Ismail-Hakki Acir1,4, Birger Bohn1, Changmin Cho1, Hans-Peter Dorn1, Andreas Hofzumahaus1, Xin Li1,5, Anna Lutz2, Sascha Nehr1,6, David Reimer1, Franz Rohrer1, Ralf Tillmann1, Robert Wegener1, Astrid Kiendler-Scharr1, Andreas Wahner1, and Hendrik Fuchs1
Yat Sing Pang et al.
  • 1Institue of Energy and Climate Research, IEK-8: Troposphere, Forschungszentrum Jülich GmbH, Jülich, Germany
  • 2Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
  • 3now at: Federal Office of Consumer Protection and Food Safety, Department 5: Method Standardisation, Reference Laboratories, Resistance to Antibiotics, Berlin, Germany
  • 4now at: Institute of Nutrition and Food Sciences, Food Science, University of Bonn, Bonn, Germany
  • 5now at: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, China
  • 6now at: European University of Applied Sciences, Brühl, Germany

Limonene is the fourth-most abundant monoterpene in the atmosphere, which upon oxidation leads to the formation of secondary organic aerosol (SOA) and thereby influences climate and air quality.

In this study, the oxidation of limonene by OH at different atmospherically relevant NO and HO2 levels (NO: 0.1 – 10 ppb; HO2: 20 ppt) was investigated in simulation experiments in the SAPHIR chamber at Forschungszentrum Jülich. The analysis focuses on comparing measured radical concentrations (RO2, HO2, OH) and OH reactivity (kOH) with modeled values calculated using the Master Chemical Mechanism (MCM) version 3.3.1.

At high and medium NO concentrations, RO2 is expected to quickly react with NO. An HO2 radical is produced during the process that can be converted back to an OH radical by another reaction with NO. Consistently, for experiments conducted at medium NO levels (~0.5 ppb, RO2 lifetime ~10 s), simulated RO2, HO2, and OH agree with observations within the measurement uncertainties, if the OH reactivity of oxidation products is correctly described.

At lower NO concentrations, the regeneration of HO2 in the RO2 + NO reaction is slow and the reaction of RO2 with HO2 gains importance in forming peroxides. However, simulation results show a large discrepancy between calculated radical concentrations and measurements at low NO levels (<0.1 ppb, RO2 lifetime ~ 100 s). Simulated RO2 concentrations are found to be overestimated by a factor of three; simulated HO2 concentrations are underestimated by 50 %; simulated OH concentrations are underestimated by about 35%, even if kOH is correctly described. This suggests that there could be additional RO2 reaction pathways that regenerate HO2 and OH radicals become important, but they are not taken into account in the MCM model.

How to cite: Pang, Y. S., Kaminski, M., Novelli, A., Carlsson, P., Acir, I.-H., Bohn, B., Cho, C., Dorn, H.-P., Hofzumahaus, A., Li, X., Lutz, A., Nehr, S., Reimer, D., Rohrer, F., Tillmann, R., Wegener, R., Kiendler-Scharr, A., Wahner, A., and Fuchs, H.: Investigating the NO-dependent photooxidation of limonene by OH and O3 using the atmosphere simulation chamber SAPHIR, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11130, https://doi.org/10.5194/egusphere-egu21-11130, 2021.

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