Reduction potential of vehicular emission in Chengdu, China: A case study of COVID-19

Abstract

The spread of coronavirus disease 2019 has significantly reduced human activities worldwide, providing a unique opportunity to assess the emission reduction potential. The impact of the lockdown on vehicular emission and traffic-related monitoring data in Chengdu, located in the Sichuan Basin, still needs to be clearly understood. In this study, we evaluated the influence of the lockdown in traffic flow, vehicular emission, and roadside environments in Chengdu based on the newly developed dynamic traffic emission inventories with high spatial and temporal resolutions and the observed pollutant concentrations at the traffic-related roadside stations. The pollutant emission intensities were highest in the central districts, and unexpectedly, the highest reduction of traffic flows and vehicular emissions occurred in the suburban areas, indicating that vehicular control in the suburban areas cannot be negligible and emission reduction in the central districts is limited. The reduction potential of vehicular CO, HC, NOx, and PM emissions in the entire Chengdu city was as high as 62%, 67%, 76%, and 71%, in which the NOx reduction potential is most significant under the extreme lockdown scenario. The vehicular emission reduction made CO, NO2, PM10, and PM2.5 concentrations decline by 57%–60%, 48%–61%, 44%–66%, and 36%–45% while O3 increase by 84%–380% at the three traffic-related roadside stations, and the increased O3 concentrations might be related to the weakened titration of NO in the VOC-limited O3 formation regime. Our study will provide novel insights into the potential of emission reduction and the development of vehicle emission control in urban areas.