Oxygenated Volatile Organic Compounds as Key Drivers of Ozone Formation: Insights From Field Measurements and Observation‐Based Modeling During the 19th Asian Games

Abstract Identifying the key drivers of O 3 formation requires accurate quantification of its precursors and detailed chemical analysis. Here we investigate the O 3 formation mechanisms around the 19th Asian Games (Hangzhou, China) when control measures were implemented to reduce pollutant emissions. With comprehensive field measurements and observation‐based modeling (OBM), we identify OVOCs as the most important O 3 precursors, accounting for about 64% of the ozone formation potential. The emission reduction in volatile organic compounds (VOCs) and NO x led to a 6.9% decrease in simulated MDA8 O 3 during the control period, contrasting with the upward trend in O 3 concentrations in most other emission control events. This is primarily because O 3 formation before and during the control was near the transition regime between VOC‐limited and NO x ‐limited regimes. Further analysis reveals that OVOCs are the primary contributors (42%) to free radicals (OH + HO 2 + RO 2 ). Additionally, we identify the most critical OVOC species for accurately simulating O 3 production in OBM. Without OVOC constraints, the model underestimates OVOC concentrations, peak ozone production rates (P(O 3 )), and atmospheric oxidative capacity by 71%, 16%, and 20%, respectively. Sensitivity tests on constraints of individual OVOCs revealed that the three most influential species on P(O 3 ) are formaldehyde, benzenediol, and acetaldehyde. Constraining these three species can reduce the simulation error of P(O 3 ) below 5%. Our work highlights the critical role of OVOC control in China's efforts to mitigate ozone pollution. It also facilitates policy development by determining the principal drivers of ozone formation and a set of atmospheric conditions under which emission control measures can be successful.