[A-AS08] Atmospheric Chemistry

[AAS08-P57] Chamber study on the influence of aerosol particles on ozone production sensitivity

*Kei Sato¹, Yu Morino¹, Yosuke Sakamoto^1,2, Jiaru Li^1,2,3, Yasuhiro Sadanaga⁴, Yoshizumi Kajii^2,1,5, Takashi Imamura^1,6 (1.National Institute for Environmental Studies, 2.Kyoto University, 3.Japan Agency for Marine-Earth Science and Technology, 4.Osaka Metropolitan University, 5.Qingdao University, 6.Tokyo Metropolitan Institute of Environmental Sciences)

Keywords:

Heterogeneous reaction,Transition metal aerosol,Environmental chamber,Ozone reduction strategies,Air pollution

Simulations based on radical budget theory and air quality models suggest that uptake of hydroperoxy (HO₂) radicals by aerosol particles may influence ozone production regimes. However, these simulations assume constant uptake coefficients and do not account for degradation of uptake coefficients due to photochemical aging. To verify the accuracy of model predictions, chamber experiments were conducted on a VOCs-NO_x photooxidation system to measure ozone production sensitivity in the presence and in the absence of copper(II)-containing ammonium sulfate aerosol particles. A 2m³ Teflon bag equipped with a solar simulator was used as the batch reactor. The ozone production sensitivity (OPS) was determined by the difference between the total oxidant production rate after a small amount of NO or propene was added at a specific irradiation time [P(OX)] and the total oxidant production rate when no addition was made [P(OX)_ref], where total oxidant OX = O₃ + NO₂. Changes in OPS in the presence and the absence of aerosol particles, as well as changes in OPS with different precursor addition times, were measured. Furthermore, the experimental OPS results were compared with simulation results of the Master Chemical Mechanism (MCM) model, which incorporates the HO₂ uptake process assuming a constant uptake coefficient. Under conditions where ozone is produced in the transition regime, it was confirmed that the presence of aerosols shifts the ozone production mechanism to the NO_x-limiting regime. Experimental results were also explained by MCM simulations. These results that model simulations assuming a constant uptake coefficient during light irradiation can approximate the influence of aerosol particles on ozone production regimes.