Evaluating Vehicle Emission Control Policies using on-Road Mobile Measurements and Continuous Wavelet Transform: a Case Study during the Asia-Pacific Economic Cooperation Forum, China 2014

Abstract. Vehicle emissions are major sources of atmospheric pollutants in urban areas, especially in megacities around the world. Various vehicle emission control policies have been implemented to improve air quality. However, the effectiveness of these policies is unclear, due to a lack of systematic evaluation and sound methodologies. During the Asia-Pacific Economic Cooperation (APEC) Forum, China 2014, the Chinese government implemented the strictest vehicle emission control policy in the country's history, which provided an opportunity to evaluate its effectiveness, based on our recently developed method. To evaluate the vehicle emission reduction, we used a mobile research platform to measure the main air pollutants (PM_2.5, black carbon (BC), SO₂, CO, NO_x and O₃) on the 4th ring road of the city of Beijing, combined with a continuous wavelet transform method (CWT) to separate out "instantaneous emissions" by passing vehicles. The results suggested that our measurements captured the spatial distribution and variation of atmospheric pollutant concentrations on the 4th ring road. The "instantaneous concentration" decomposed by the CWT method represents on-road emissions better than other methods reported in the literature. With this method, we found that the daytime vehicle emission of CO and NO_x decreased by 28.1 and 16.3 %, respectively, during the APEC period relative to the period before APEC, and by 39.3 and 38.5 %, respectively, relative to the period after APEC. The nighttime vehicle emissions of CO and NO_x decreased by 56.0 and 60.7 %, respectively, during the APEC period relative to the period after APEC. Because vehicle emissions of NO_x and CO contribute considerably to the total emissions of these pollutants in Beijing, the vehicle emission control policy implementation was extremely successful in controlling air quality during APEC 2014, China.