In this study, we investigate the planetary boundary layer height (PBLH) using micro-pulse lidar (MPL) and microwave radiometer (MWR) methods, examining its relationship with the mass concentration of particles less than 2.5 µm in aerodynamic diameter (PM_2.5) and its chemical compositions. Long-term PBLH retrieval results are presented derived from the MPL and the MWR, including its seasonal and diurnal variations, showing a superior performance regarding the MPL in terms of reliability and consistency with PM_2.5. Also examined are the relationships between the two types of PBLHs and PM_2.5. Unlike the PBLH derived from the MPL, the PBLH derived from the MWR does not have a negative correlation under severe pollution conditions. Furthermore, this study explores the effects of the PBLH on different aerosol chemical compositions, with the most pronounced impact observed on primary aerosols and relatively minimal influence on secondary aerosols, especially secondary organics during spring. This study underscores disparities in PBLH retrievals by different instruments during long-term observations and unveils distinct relationships between the PBLH and aerosol chemical compositions. Moreover, it highlights the greater influence of the PBLH on primary pollutants, laying the groundwork for future research in this field.

Understanding the seasonal behavior of fine particles (PM_2.5) 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 PM_2.5 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 PM_2.5 chemical components based on year-round field measurements (December 2020–November 2021) at Nanjing University of Information Science and Technology. Annual mean PM_2.5 mass concentration is $\mathrm{30.0}\pm \mathrm{18.5}\mathrm{\mu }\mathrm{g}{\mathrm{m}}^{-\mathrm{3}}$ , with winter peaks (48.3 µg m⁻³) and summer lows (20.4 µg m⁻³). Organic aerosol dominates PM_2.5, followed by sulfate in warmer seasons and nitrate in winter. Stable meteorological conditions promote the accumulation of primary aerosols and nitrate. The accumulation of SOA and sulfate remains substantial under elevated PBLH conditions, owing to strong photochemical production, rendering them relatively insensitive to PBLH variations. In contrast, during cold and humid winters, shallow PBLH promotes nitrate buildup, which subsequently suppresses boundary layer development, forming positive feedback that accelerates nitrate concentration growth. Source apportionment reveals that the contrasting seasonal sources, shaped by both local chemistry and regional transport, emphasize the need for seasonally adaptive and region-specific emission control measures.

Understanding the seasonal behavior of fine particles (PM_2.5) 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 PM_2.5 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 PM_2.5 chemical components based on year-round field measurements (December 2020–November 2021) at Nanjing University of Information Science and Technology. Annual mean PM_2.5 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 PM_2.5, 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 PM_2.5 pollution in the YRD.

Understanding the seasonal behavior of fine particles (PM_2.5) 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 PM_2.5 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 PM_2.5 chemical components based on year-round field measurements (December 2020–November 2021) at Nanjing University of Information Science and Technology. Annual mean PM_2.5 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 PM_2.5, 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 PM_2.5 pollution in the YRD.

Understanding the seasonal behavior of fine particles (PM_2.5) 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 PM_2.5 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 PM_2.5 chemical components based on year-round field measurements (December 2020–November 2021) at Nanjing University of Information Science and Technology. Annual mean PM_2.5 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 PM_2.5, 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 PM_2.5 pollution in the YRD.