[Evolution Characteristics and Typical Pollution Episodes of PM and O 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） and ozone （O） levels becoming evident. To understand the complex pollution characteristics and evolution patterns of PM and O 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 and O in Bozhou City from 2017 to 2022 and subsequently analyze their causes and precursor sources. The results indicated that： ① PM-O complex pollution in Bozhou City mostly occurred under high-pressure weather conditions, with daytime high temperatures and low humidity promoting the formation of O pollution, whereas nighttime high humidity and atmospheric oxidative conditions promoted the generation of secondary components such as nitrates and ammonium salts in PM.