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

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