Spatial Distribution Similarities and Differences of Atmospheric PM2.5 Chemical Components in Typical Cities of Central and Southern China
To characterize the spatial variability of PM2.5 chemical components at the urban scale, ambient PM2.5 samples were collected from eight sites across Changsha, China. Samples were analyzed using ion chromatography, elemental carbon/organic carbon (EC/OC) analysis, and X-ray fluorescence (XRF) spectroscopy. Results showed that PM2.5 concentrations in urban areas were significantly higher than in suburban locations, with notably elevated levels at Changsha New Railway Station and Mapoling. Across different PM2.5 pollution levels, the eight sites exhibited pronounced spatial differences in concentration while sharing similar chemical compositions. Source apportionment identified secondary nitrate, vehicle emissions, and secondary sulfate as major contributors to PM2.5. The spatial distribution of these sources varied distinctly: secondary nitrate showed lower contributions in central areas but higher in western and southeastern regions; secondary sulfate was more prominent in the southeast, while vehicle emissions contributed more in the southeast and less in the west. Additionally, aerosol liquid water content promoted the secondary formation of nitrate and sulfate, exacerbating PM2.5 pollution. Secondary organic carbon was elevated in areas with high pedestrian density, suggesting enhanced secondary organic aerosol formation under intensive human activity. The study provides insights for targeted pollution control strategies in Changsha and similar cities.