RESEARCH ARTICLE

Unexpected fast radical production emerges in cool seasons: implications for ozone pollution control

¹ State Environmental Protection Key Laboratory of Formation and Prevention of Urban Air Pollution ComplexShanghai Academy of Environmental Sciences, Shanghai 200233, China
² State Key Joint Laboratory of Environmental Simulation and Pollution ControlCollege of Environmental Sciences and EngineeringPeking University, Beijing 100871, China
³ Wolfson Atmospheric Chemistry LaboratoriesDepartment of ChemistryUniversity of YorkYork YO1 7EP, UK

^* Corresponding authors (emails: k.lu@pku.edu.cn (Keding Lu); huangc@saes.sh.cn (Cheng Huang)))

Received: 21 August 2021
Accepted: 17 January 2022

Abstract

Ozone is a crucial air pollutant that damages human health and vegetation. As it is related to the photo-oxidation of the nitrogen oxides and volatile organic compounds, the summertime reduction of these precursors is the primary focus of current ozone mitigation strategies. During ozone pollution episodes in eastern China, an observed accumulation of daily total oxidants (O_x=NO₂+O₃) in cool seasons (spring and autumn: 60 ppb and winter 40 ppb) is comparable to that in summer (60 ppb), indicating fast photochemical production of secondary pollutants including ozone over the year. Unrecognized fast radical primary productions are found to counteract the increased termination of hydroxyl radical and unfavorable meteorological conditions to maintain the rapid total oxidant formations in cool seasons. Elucidating and regulating the primary radical sources may be critical for the secondary air pollution control in cool seasons.