Effects of heat waves on ozone pollution in a coastal industrial city: Meteorological impacts and photochemical mechanisms

Surface ozone (O3) pollution triggered by extreme weather conditions is attracting increasing attention. Heat waves in summer of 2022 were chosen to explore the photochemical and meteorological impacts on O3 formation in the southeastern coastal industrial city of Quanzhou in China. The machine-learning (ML)-based weather normalization showed that the de-weathered O3 concentrations (increased by 6.69 mu g m- 3) in 2022 were higher than those from 2015 to 2021. Temperature is the most important variable (33.5%), followed by solar radiation (23.5%) and RH (10.1%), differing from the O3 pollution in inland cities. The Observation-Based Model (OBM) analysis results showed that hydroxyl radical (OH) was the predominant oxidant for daytime atmospheric oxidation capacity (AOC). And oxygenated volatile organic compounds (OVOCs), NO2, and CO were the dominant contributors to OH reactivity, accelerating the recycling of ROx radicals and O3 formation. The daytime reaction rate of HO2+NO during the O3 pollution episodes was 20.0 ppb h- 1, accounting for 65% of the total O3 production. The contribution of RO2+NO to the O3 production enhanced the possibility of the MDA8h O3 exceeding the Air Quality Standard of China. This study improves the understanding of O3 formation mechanisms in a coastal industrial city during heat waves, and the elevated contributions of meteorological conditions to O3 pollution become more challenge for the reduction of anthropogenic emissions controll.