Increased urban ozone in heatwaves due to temperature-induced emissions of anthropogenic volatile organic compounds

Abstract

Urban ozone (O₃) pollution correlates with temperature, and higher O₃ often occurs during heatwaves, threatening public health. However, limited data on how anthropogenic volatile organic compound (AVOC) precursor emissions vary with temperature hinders understanding their impact on O₃. Here we show that the increase in non-combustion AVOC emissions (for example, from volatile chemical products) during a heatwave in Shanghai contributes significantly to increased O₃, on the basis of ambient measurements, emissions testing and air quality modelling. AVOC concentrations increase ~twofold when the temperature increases from 25 °C to 35 °C due to air stagnation and increased emissions. During the heatwave, higher concentrations result in an 82% increase in VOC OH reactivity. Air quality simulations reveal that temperature-driven AVOC emissions increases account for 8% (1.6 s^–1) of this reactivity increase and enhance O₃ by 4.6 ppb. Moreover, we predict a more profound (twofold) increase in OH reactivity of oxygenated VOCs, facilitating radical production and O₃ formation. Enhanced AVOC emissions trigger O₃ enhancements in large cities in East China during a heatwave, and similar effects may also happen in other AVOC-sensitive megacities globally. Reducing AVOC emissions, particularly non-combustion sources, which are currently less understood and regulated, could mitigate potential O₃ pollution in urban environments during heatwaves.