[Evolution Characteristics and Typical Pollution Episodes of PM 2.5 and O 3 Complex Pollution in Bozhou City from 2017 to 2022].

In China, atmospheric pollution exhibits a complex pattern, with simultaneous exceedances of fine particulate matter （PM _2.5 ） and ozone （O ₃ ） levels becoming evident. To understand the complex pollution characteristics and evolution patterns of PM _2.5 and O ₃ in Bozhou City, various methods such as weather classification, analysis of typical pollution processes, and investigation of precursor sources were employed to explore the pollution and variations of PM _2.5 and O ₃ in Bozhou City from 2017 to 2022 and subsequently analyze their causes and precursor sources. The results indicated that： ① PM _2.5 -O ₃ complex pollution in Bozhou City mostly occurred under high-pressure weather conditions, with daytime high temperatures and low humidity promoting the formation of O ₃ pollution, whereas nighttime high humidity and atmospheric oxidative conditions promoted the generation of secondary components such as nitrates and ammonium salts in PM _2.5 . ② During the pollution process, PM _2.5 in Bozhou City mainly originated from biomass burning, secondary generation, traffic pollution, coal combustion, and dust sources. Volatile organic compounds （VOCs） primarily emerged from plant sources, traffic pollution, oil and gas evaporation, solvent use, fossil fuel combustion, residential emissions, and industrial emissions. Biomass burning and traffic pollution made significant contributions to the pollution process. ③ Analysis of air mass trajectories and regional pollution situations indicated that the overlay of northern and southern air masses, along with local generation, were the main causes of the PM _2.5 -O ₃ complex pollution in Bozhou from October 18th to 27th, 2022.