Increased Urban Ozone in Heat Waves due to Temperature-Induced Emissions of Anthropogenic Volatile Organic Compounds.

Urban ozone (O) pollution correlates with temperature, and higher O often occurs during heat waves, threatening public health. However, limited data on how anthropogenic volatile organic compound (AVOC) precursor emissions vary with temperature hinders understanding their impact on O. Here, we show that the increase in non-combustion AVOC emissions (e.g., from volatile chemical products) during a heat wave in Shanghai contributes significantly to increased O, based on ambient measurements, emission testing, and air quality modelling. AVOC concentrations increase ~2× when the temperature increases from 25 °C to 35 °C due to air stagnation and increased emissions. During the heat wave, higher concentrations result in an 82% increase in VOC OH reactivity. Air quality simulations reveal that temperature-driven AVOC emission increases account for 8% (1.6 s) of this reactivity increase and enhance O by 4.6 ppb. Moreover, we predict a more profound (2×) increase in OH reactivity of oxygenated VOCs, facilitating radical production and O formation. Enhanced AVOC emissions trigger O enhancements in large cities in East China during the heat wave, 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 O pollution in urban environments during heat waves.