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. Ozone pollution is enhanced by increased non-combustion anthropogenic volatile organic compound emissions during heatwaves, according to atmospheric measurements and modelling of ozone concentrations in a heatwave in Shanghai.