Aerosol chemical composition and sources during unexpected wintertime haze episodes in 2023 in urban Xuzhou of eastern China

Understanding the chemical composition and sources of aerosols during extreme haze episodes is essential for effective air quality management, particularly in rapidly industrializing regions. This study investigates the aerosol chemistry and sources during unexpected winter haze events in December 2023 in Xuzhou, Eastern China. Continuous online monitoring of fine particulate matter (PM2.5), combined with detailed chemical analysis and concentration weighted trajectory (CWT) analysis, was conducted to elucidate the sources and processes driving these pollution episodes. Positive matrix factorization identified five major PM2.5 sources: secondary nitrate-rich aerosols, vehicular emissions, industrial activities, dust emissions, and coal combustion. Nitrate was the dominant component during severe haze periods, whereas dust significantly contributed during dust storm episodes. CWT analysis highlighted substantial regional contributions, with industrial and dust-rich areas to the northwest and marine aerosols from coastal regions playing key roles. The findings suggest that nitrate formation and regional dust transport were the primary drivers of severe winter haze in Xuzhou. Effective mitigation strategies should prioritize nitrogen oxides emission control and dust management. This study underscores the necessity of regional collaboration and continuous monitoring to tackle complex air pollution challenges.