New insights into the boundary layer revolution impact on new particle formation characteristics in three megacities of China

The distribution and source of atmospheric particles significantly influence the atmospheric environment. This study examines changes in Particle Number Size Distribution (PNSD) and its relationship with Planetary Boundary Layer Height (PBLH), as well as nucleation trajectories during new particle formation (NPF) events in three major Chinese cities: Beijing (BJ), Guangzhou (GZ), and Shanghai (SH). The observation periods include July 2017 to October 2019 (408 effective observation days), November 2019 to March 2020 (127 effective observation days), and April to June 2020 (44 effective observation days) for BJ, GZ, and SH, respectively. The results show that BJ exhibits the highest Nucleation Mode Particle Number Concentration (PNC) at 2.05 × 10⁶ cm⁻³, while GZ records the highest NPF frequency at 25.98%. In contrast, SH has the lowest PNC at 6.27 × 10⁵ cm⁻³ and the lowest NPF frequency (18.87%). High background particle concentrations significantly impact NPF. The sources of PNSD at the three observation sites exhibit distinct trajectories on NPF days. The main source of pollutants in BJ is Mongolia, located to the northwest. In GZ, the contribution mainly comes from Jiangxi and Fujian provinces to the northeast, while in SH, the source lies to the northwest. NPF frequencies consistently exceed 25%, predominantly in the northern regions of each site, indicating higher NPF levels in the north compared to the south. Nucleation-mode particles at all sites originate from continental sources, rather than marine sources, during NPF events. This research provides valuable insights for developing strategies to manage the atmospheric environment.