[A-AS11] Atmospheric Chemistry

[AAS11-P17] Investigation of the Relationship Between Ozone Production and HOx Production Rate in Tsukuba in the Summer of 2022 Based on HOx Measurements

*Yosuke Sakamoto¹, Koichi Egami², Jiaru Li³, Yu Morino¹, Yoshihiro Nakashima⁴, Ayako Yoshino¹, Akinori Takami¹, Nanase Kohno⁵, Yasuhiro Sadanaga⁶, Yoshizumi Kajii⁷ (1.National Institute for Environmental Studies, 2.Kyoto University, 3.Tokyo Metropolitan University, 4.Tokyo University of Agriculture and Technology, 5.Kindai University, 6.Osaka Metropolitan University, 7.Qingdao University)

Keywords:tropospheric ozone, oxidant, short lived climate forcer, air pollutant

Tropospheric ozone (hereafter referred to as ozone) is both an air pollutant and a greenhouse gas, necessitating its reduction. However, despite the decline in concentrations of its precursors, volatile organic compounds (VOCs) and nitrogen oxides (NOx), ozone levels remain persistently high. The local ozone production rate is described as the product of ozone production efficiency (the number of ozone molecules produced per HOx radical) and the HOx radical production rate. While the dependence of ozone production efficiency on VOCs and NOx has been extensively studied, the dependence of the HOx radical production rate on its precursors remains complex and insufficiently understood. This study investigates the precursor dependence of the HOx radical production rate to gain insights into the persistent high ozone levels.
This presentation reports the results of an intensive observation campaign conducted in late August 2022 in Tsukuba. We determined the ozone production rate and ozone production efficiency using total OH reactivity measurements based on the laser-induced fluorescence (LIF) method and total peroxy radical measurements using the peroxy radical chemical amplification (PERCA) method. The HOx radical production rate was then estimated from the observed ozone production rate divided by the ozone production efficiency.
During the observation period, air masses alternately arrived from the southwest (metropolitan area) and the northeast (coastal area). Correlation analysis between the ozone production rate, ozone production efficiency, and HOx radical production rate revealed a stronger correlation with the HOx radical production rate. Furthermore, the ozone and formaldehyde photolysis-derived radical production could not fully explain the early morning ozone production rate. Although HONO and other OVOCs' photolysis are likely radical source, the lack of direct measurements in this observation prevents drawing a definitive conclusion.
Future research requires concurrent measurements of radical precursors to conduct a more detailed analysis.