Novel Insights into the Vertical Distribution Patterns of Multiple PM2.5 Components in a Super Mega-City: Responses to Pollution Control Strategies

The vertical profiles of PM2.5 chemical components are crucial for tracing pollution development, determining causes, and improving air quality. Yet, previous studies only yielded transient and sparse results due to technological limitations. Comprehensive analysis of component vertical distribution across an entire boundary layer remains challenging. Here, we provided a first-ever vertical–temporal continuous dataset of aerosol component concentrations, including sulfate (SO42−), ammonium (NH4+), nitrate (NO3−), organic matter (OM), and black carbon (BC), using ground-based remote sensing retrieval. The retrieved dataset showed high correlations with in situ chemical observation, with all components exceeding 0.75 and some surpassing 0.90. Using the Beijing 2022 Winter Paralympics as an example, we observed distinct vertical patterns and responses to meteorology and emissions of different components under strictly controlled conditions. During the Paralympics, the emissions contribution (51.12%) surpassed meteorology (48.88%), except SO42− and NO3−. Inorganics showed high-altitude transport features, while organics were surface-concentrated, with high-altitude inorganic(organic) concentrations 1.19(0.56) times higher than those near the surface. SO42− peaked at 919 m and 1516 m, NH4+ and NO3− showed an additional peak near 300–500 m, influenced by surface sources and secondary generation. The inorganics exhibited a transport-holding–sinking–resurging process, with NO3− reaching higher and sinking more. By contrast, organic components massified near 200 m, with a slight increase in high-altitude transport by time. The dispersion of all components driven by a north-westerly wind started 5 h earlier at high altitudes than near the surface, marking the end of the process. The insights gleaned highlight regional inorganic impacts and local organic impacts under the coupling of emission control and meteorology, thus offering helpful guidance for source attribution and targeted control policies.