Measurement report: Insights into seasonal dynamics and planetary boundary layer influences on aerosol chemical components in suburban Nanjing from a long-term observation

Abstract. Understanding the seasonal behavior of fine particles (PM2.5) and its chemical components is critical for improving air quality in the Yangtze River Delta (YRD), a densely populated and polluted region in China. While previous studies have addressed PM2.5 mass trends, the role of planetary boundary layer height (PBLH) in modulating chemical composition remains insufficiently explored. This study investigates seasonal variations and PBLH effects on PM2.5 chemical components based on year-round field measurements (December 2020–November 2021) at Nanjing University of Information Science and Technology. Annual mean PM2.5 mass concentration is 30.0 ± 18.5 μg m-3, with winter peaks (48.3 μg m⁻3) and summer lows (20.4 μg m⁻3). Organic aerosol dominates PM2.5, followed by sulfate in warmer seasons and nitrate in winter. PBLH strongly influences component dynamics: low PBLH in winter enhances nitrate and primary aerosol accumulation, while high PBLH in summer promotes secondary organic aerosol and sulfate formation via photochemistry. Nitrate is most sensitive to PBLH changes, showing rapid buildup under stable conditions. The potential source contribution function analyses identify seasonal source regions: southern combustion for primary organic aerosol in warm seasons, northern industrial and rural areas in winter, and biogenic and coal combustion sources for secondary organic aerosol. Sulfate and nitrate exhibit shifts between local and regional origins. These findings highlight the need for season-specific emission control strategies, such as targeting volatile organic compounds in summer and reducing industrial nitrogen oxides in winter, to effectively mitigate PM2.5 pollution in the YRD.