Roadside atmospheric pollution: still a serious environmental problem in Beijing, China

China has made great efforts to reduce ambient atmospheric pollutant concentrations in the past few decades. The air quality in northern China has improved greatly. However, most research has focused on atmospheric pollution in non-roadside environments that have little influence from traffic flow and are impacted by less vehicle exhaust. In this study, hourly air quality monitoring data were collected at four traffic stations and four nontraffic stations in Beijing from June 2014 to September 2017 to analyze the spatial-temporal variations of atmospheric pollutants related to traffic. The traffic stations had higher concentrations of PM2.5, PM10, SO2, NO2, and CO but lower concentrations of O-3. Although the overall air quality in Beijing is improving, the pollution rates of PM2.5, PM10. and NO2 in the traffic stations were still high at 47.91%, 50.71%, and 61.22% concentrations, respectively. The air pollution levels in traffic environments are systematically higher than those in nontraffic environments, during both daytime and nighttime, except O-3. Furthermore, the traffic stations near ring roads with large numbers of diesel trucks were even more polluted, suggesting the influence of traffic emissions. Under adverse meteorological dispersion conditions, both the traffic and nontraffic stations had high pollution levels, but the pollution at the traffic stations was much higher. To reduce the air pollution level, a series of vehicle restriction rules have been imposed, including license plate restriction. Our analysis revealed obvious cycles associated with license plate restriction rules, suggesting the possibility for further improvement in vehicle restriction rules. The results from our study suggest that roadside environments with heavy traffic in Beijing, China, are still highly polluted and need further efforts to improve.