[A-AS07] Atmospheric Chemistry

[AAS07-20] Effects of copper-doped aerosol upon the ozone formation during VOC/NO_x photooxidation

*Kei Sato¹, Ratih Dwi Fardilah², Jiaru Li², Yu Morino¹, Yosuke Sakamoto^2,1, Yoshizumi Kajii^1,2 (1.National Institute for Environmental Studies, 2.Kyoto University)

Keywords:Surface-level ozone, Hydrogen oxide cycle, Heterogeneous reaction, Uptake coefficient, Laboratory smog chamber

Recently, atmospheric modeling researchers suggested that the suppression of ozone due to HO₂ uptake explains increasing surface-level ozone concentration in China after the countermeasure of PM_2.5 (K. Li et al., 2018; Ivatt et al., 2022). However, to the best of our knowledge, no ozone formation model including the HO₂ uptake has been checked by laboratory chamber experiments. In this study, we conducted laboratory experiments on ozone formation during the VOC/NO_x photooxidation in the presence and absence of copper doped-ammonium sulfate aerosol. We used propene or mixed nine VOCs as the precursor of photochemical ozone. In a series of chamber experiments, the maximum ozone concentration decreased with increasing the initial aerosol surface concentration. When the initial aerosol surface concentration was 5-10 x 10⁸ nm² cm^-3, the maximum ozone concentration was about 1/2 of that measured in the absence of aerosol. Using a laser photolysis-laser induce fluorescence method (J. Li et al., 2022), the uptake coefficient of copper-doped aerosol was separately determined to be 0.49±0.02. We also compared the experimental ozone concentration with that predicted by a Master Chemical Mechanism (MCM) model calculations in which the uptake of HO2 is considered and the uptake coefficient was set to 0.5. Measured temporal profiles of ozone was largely reproduced with results of the MCM model. These results confirms that the existence of aerosol particles with a high uptake coefficient against HO₂ radicals suppresses the formation of photochemical ozone and the concentration of formed ozone is successfully explained when the uptake of HO₂ is considered in the model.

Acknowledgements: KS thanks to Kiyomi Tsukagoshi of National Institute for Environmental Studies (NIES) for the technical contribution to laboratory experiments. This study was supported by the Environmental Research and Technology Development Fund (JPMEERF20215002) and NIES Research Funding (Type A).