The physicochemical properties of atmospheric particles including morphologies and composition are directly related to their sources and formation mechanisms. However, most previous studies have been limited to a few sites and small numbers of particles. In this study, we employed computer-controlled scanning electron microscopy (CCSEM) to enhance measurement efficiency and enable long-term observations across multiple sites. To investigate properties and source variations of atmospheric particles in response to control measures before, during, and after the 2022 Winter Olympic Games (WOG) and Winter Paralympic Games (WPG), ambient particles were passively collected in 15 northern Chinese cities and automatically analyzed by an advanced CCSEM (IntelliSEM EPAS). Variations in particle numbers (PN), size distribution, elemental composition, and sources were comprehensively analyzed. Over one million particles were classified into mineral, carbonaceous, fly ash, sulfur-related, metal-containing, salt, and biological particles using the user-defined classification rules. The results showed that improved air quality was witnessed during the WOG with reduced PN and anthropogenic particles, but deteriorated during the WPG due to increased coarse-mode PN, mineral, and sulfur-related particles. Beijing and Zhangjiakou exhibited lower AQI, PN, and anthropogenic particles, while non-competition cities experienced higher levels of anthropogenic and sulfur-related particles. Notably, Taiyuan and Shijiazhuang showed distinct emission reductions during the WOG, while Baoding and Tangshan demonstrated less effective control with high levels of sulfur-related and anthropogenic Fe-rich particles. This study shows the capability of CCSEM to provide microscopic evidence of particle sources and behaviors, offering valuable insights into the efficacy of control measures during major events.

The adverse health effects of air pollution are being increasingly recognized as major causes of disease. Atmospheric particles, as a major component of air pollution, have been extensively studied in terms of their sources, physicochemical characteristics, transport in the atmosphere, and changes in particulate composition during their time in the atmosphere. The relationships between particles and diseases are complex, so research on the health effects and damage mechanisms of particulate matter (PM) is of significant importance. This study reviews the health effects of PM and provides an overview of the hazards of atmospheric PM to various human organs. In addition, this review explores the mechanisms of damage, summarizes the research methods used to determine the health effects, and discusses the influential health factors caused by PM. In combination with current Chinese and global research, the modern technologies and research trends on the health effects of particles are elucidated.

The COVID-19 pandemic emerging in early 2020 triggered global responses. In China, stringent lockdown measures were implemented to suppress the rapid spread of infection, resulting in substantial reductions in anthropogenic emissions. However, several atmospheric haze episodes still occurred. Previous studies have investigated the cause of these haze events predominantly based on the average concentration obtained from bulk analysis, while the micro-scale structure and composition of the haze particles remain poorly understood. In this study, we analyzed the morphology and elemental composition of individual airborne particles collected from an urban area of Beijing in early 2020 using high-resolution transmission electron microscopy equipped with Energy Dispersive X-ray Spectroscopy. The results show that sulfur-dominant, ultrafine, and mixed particles were the most abundant types during the pollution process. Reduced human activities corresponded with a lower percentage of anthropogenic-derived soot, organic particles, and metal-containing particles. Atmospheric aging analysis demonstrated that secondary aerosols were the most significant component during the haze events. The proportion of core–shell particles increased with the intensification of the pollution, while the core/shell ratio of the particles decreased, suggesting a substantial contribution of secondary aerosols to the haze formation. Despite reductions in anthropogenic emissions, larger proportions of secondary aerosol formation enhanced aerosol aging and thereby caused episodic haze pollution during the lockdown period.