Kinetics and impacting factors of HO<sub>2</sub> uptake onto submicron atmospheric aerosols during the 2019 Air QUAlity Study (AQUAS) in Yokohama, Japan

Abstract. HO2 uptake kinetics onto ambient aerosols play pivotal roles in tropospheric chemistry but are not fully understood. Field measurements of aerosol chemical and physical properties should be linked to molecular-level kinetics; however, given that the reactivity is low, traditional analytical techniques unable achieve this goal. We developed an online approach precisely investigate lower-limit values (i) reactivities gases (ii) coefficients (γ) during 2019 Air QUAlity Study (AQUAS) Yokohama, Japan. identified effects individual components on γ. The results were verified laboratory studies components: transition metals a key role processes, indirectly influence such processes (i.e., by altering surface or providing active sites), with smaller particles tending yield higher γ than larger owing limitation gas-phase diffusion being micrometer distribution depleting species as metal ions mostly distributed accumulation mode aerosol. modeling utilized derived previous studies, further confirming our conclusion. However, high NO concentrations peroxy radical loss submicron has negligible impact O3 production rate sensitivity regime.