Direct thermal enhancement dominates over emission-mediated pathways in heatwave-induced O3 and SOA increases across China

Abstract

Heatwaves are major drivers of ozone (O3) and secondary organic aerosol (SOA) pollution. High temperatures directly accelerate photochemical reaction rates and concurrently enhance emissions of biogenic volatile organic compounds (BVOCs) and soil nitric oxide (SNO). However, the individual contributions of these direct and emission-mediated pathways to pollution formation remain poorly constrained. This study explicitly quantifies the distinct roles of these two pathways during heatwave events in China. Results show that high temperatures drive over 80 % (normalized) of the O3 and SOA increases nationally, primarily through favorable weather conditions and enhanced atmospheric oxidation capacity. The O3-temperature dependence is strongest in the Yangtze River Delta (0.66 ppb °C−1) and Pearl River Delta (0.95 ppb °C−1). Furthermore, high-temperature-induced BVOC emissions significantly exacerbate O3 in VOC-limited regions like the North China Plain. These findings underscore the importance of climate mitigation by illustrating its critical role in alleviating temperature-driven secondary pollution.