Although air quality in Beijing has improved year by year, regional heavy air pollution episodes still occur in autumn and winter. Investigating the characteristics, influencing factors, and causes of such typical regional-scale heavy pollution events is of great significance for formulating differentiated control strategies. This study focuses on Shijingshan District and analyzes three heavy pollution episodes that occurred in 2024, comparing them with non-pollution periods. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model was employed to calculate 72 h backward trajectories for source attribution, while real-time traffic flow monitoring was conducted on major local roads during the pollution episodes. In addition, meteorological factors such as wind speed and boundary layer height were analyzed to explore their correlations with pollutant concentrations. Results indicate that PM_2.5 was the dominant pollutant, with the three heavy pollution episodes increasing the monthly mean concentration by 30.8%-44.1%. NO₂ exhibited both pronounced evening peaks and stepwise declines, along with spatial variability. Regional transport pathways determined pollutant accumulation characteristics, with short-distance low-altitude transport contributing 77.0%. Wind speed and boundary layer height had significant dilution effects, showing stable negative correlations with NO₂, whereas PM_2.5 displayed stage-dependent relationships, reflecting uncertainties in the meteorological dilution effect. Although local vehicular emissions exerted some influence on air quality, they were not the dominant factor during heavy pollution episodes. Instead, regional pollutant accumulation, atmospheric transformation, and unfavorable dispersion conditions were identified as the main causes.

Fuel-powered construction machinery is widely used and numerous, and generates a large number of air pollutant and greenhouse gas emissions during fuel combustion process. The promotion and application of zero-emission machinery is the important path for collaborative control of carbon and air pollutant emissions. This paper quantifies and evaluates the environmental emission reduction benefits brought about by the use of zero-emission machinery, summarizes the promotion practices and experiences of zero-emission construction machinery at home and abroad, analyzes the difficulties and problems in promoting application in China, and generates insights into the future promotion and application of zero-emission construction machinery in cities. The results show that, compared with fuel machinery, the use of zero-emission machinery has a significant pollution reduction effect, in which CO₂ emissions are reduced by 99.8%, volatile organic compounds(VOCs) emissions are reduced by 99.0% to 99.5% and NO_x emissions are reduced by 93.2% to 93.9%. At present, both domestic and foreign regions have the experience of implementing economic and non-economic measures to promote the application of zero-emission machinery for the whole life cycle management of construction machinery. However, there are still problems such as low technical performance, high acquisition cost, immature market, incomplete supporting facilities and so on. It is recommended that energizing financial, improving product standards and clearing targets could be adopted to promote zero-emission construction machinery and achieve the goal of synergistic carbon pollution control.