CHARACTERIZING ON-ROAD VEHICULAR EMISSIONS AND THEIR IMPACTS ON NEAR-ROADWAY AIR POLLUTION A Dissertation Presented to the Faculty of the Graduate School of Cornell University In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy by Xing Wang August 2011 © 2011 Xing Wang CHARACTERIZING ON-ROAD VEHICULAR EMISSIONS AND THEIR IMPACTS ON NEAR-ROADWAY AIR POLLUTION Xing Wang, Ph. D. Cornell University 2011 Traffic emission is a major source of urban air pollution. Vehicle is a significant contributor of carbon monoxide (CO), nitrogen oxides (NOx), black carbon (BC) and ultrafine particle (UFP) on-road and near-roadways. People living and working near roadways are facing health risks due to the exposure of elevated pollutant concentration. In order to develop cost-efficient strategies to mitigate near-road air pollution for protecting public health and promoting sustainable growth, it is imperative to characterize on-road traffic emission and its impacts on near-road air quality. On-road chasing method was used in this study to investigate on-road vehicle emissions. This is the first application of this method in China. The method was developed and improved during a four-year field campaign and is an efficient approach to characterize emissions of a large number of on-road vehicles. Fleet average and individual emission factors (EF) are derived and reported. The large sample size significantly expands the database of real world Chinese vehicle emissions. Some of the results are reported for the first time in China: BC and UFP number EF of vehicles by type; EF of buses linked with emission standard; EF distribution based on large sample size; contribution of “heavy emitter” to entire on- road emission; spatial variance of UFP number concentration at on-road, roadside and ambient environments. My work suggests that diesel trucks are a major source of summertime BC in Beijing. Furthermore, “heavy emitter” accounts for a significant portion of BC emissions in Beijing and Chongqing. I also observed a clear downward trend of BC EF of diesel trucks in Beijing from 2008 to 2010, and of buses with more tighten emission standard. These observations indicate the effectiveness of traffic emission control measures (i.e. improvement of fuel quality in Beijing and enforcement of stringent emission standards) on BC EF reduction of diesel vehicles. However, comparison works between BC and NOx EF did not show NOx EF improvement as that of BC. The results and conclusions in this dissertation provide support for policy makers to evaluate and modify current traffic related air pollution control measures and propose future work. BIOGRAPHICAL SKETCH Xing Wang joined Sibley School of Mechanical and Aerospace Engineering of Cornell University in 2006. Prior to that he was at Tsinghua-BP Clean Energy Research and Education Center of Tsinghua University in Beijing, where he earned his Master of Science degree in 2006. His M.S. thesis focuses on the topic of the biomass energy utilization strategy in China. As a member of energy group, Mr. Wang participated the project of “Sustainable Urban Mobility” sponsored by BP in 2005. Mr. Wang earned his Bachelor of Science degree in Engineering in 2004, at the Department of Thermal Engineering of Tsinghua University in Beijing. His B.S thesis title is “Potential CO2 Sequestration and Utilization Opportunities in China”. Mr. Wang earned “Excellent Graduates Award of Tsinghua University” in 2004 to regard his excellent academic performance during his undergraduate life in the Department of Thermal Engineering. iii ACKNOWLEDGMENTS I would like to sincerely thank my advisor, Dr. Ke Max Zhang for supervising me for all these years as an academic mentor. I would like to give my special acknowledgement to Dr. Dane Westerdahl for helping me to conduct my research and solve tremendous problems I met. I would like to thank the US Environmental Protection Agency (USEPA), Lehman Fund for Scholarly Exchange, for funding support for my studies. I would like to thank Tony Hansen of Magee Scientific, US and Beijing staff of TSI and Beijing staff of Vaisala for technical assistance. I would like to thank my colleagues in China, who provided me tremendous supports to carry out my research at Beijing and Chongqing: Dr. Ye Wu, Dr. Liu Yang, Mr. Shaojie Song and Mr. Zhenhua Li at Tsinghua University; Dr. Jingnan Hu at Chinese Research Academy of Environmental Sciences (CRAES); Dr. Xiaochuan Pan, Dr. Tong Zhu, Dr. Xinhua Wang and Dr. Yuming Guo at Peking University. I am really grateful for the warm and comprehensive supports of my parents, who make me feel blessed every single day. iv TABLE OF CONTENTS BIOGRAPHICAL SKETCH ......................................................................................... iii ACKNOWLEDGMENTS ............................................................................................. iv TABLE OF CONTENTS ............................................................................................... v LIST OF FIGURES ...................................................................................................... vii LIST OF TABLES ........................................................................................................ ix LIST OF ABBREVIATIONS ........................................................................................ x 1. CHAPTER 1 INTRODUCTION ............................................................................... 1 2. CHAPTER 2 CHARACTERIZATION OF ON-ROAD VEHICLE EMISSION FACTOR AND MICRO-ENVIRONMENTAL AIR QUALITY ............................. 6 2.1 Introduction .............................................................................................. 6 2.2 Experimental Methods .............................................................................. 9 2.2.1 Monitoring sites ................................................................................ 9 2.2.2 Sampling period and traffic interventions ....................................... 10 2.2.3 Instrumentation and methodology ................................................... 11 2.3 Results and Discussion ........................................................................... 13 2.3.1 On-road emission factors of gasoline and diesel vehicles in Beijing 13 2.3.2 Micro-environmental Air Quality in Beijing .................................. 20 2.3.3 The impacts of traffic reduction experiment in summer 2007 ........ 24 2.3.4 Limitations ...................................................................................... 26 2.4 Conclusions ............................................................................................ 27 3. CHAPTER 3 EVALUATING THE AIR QUALITY IMPACTS OF BEIJING 2008 OLYMPIC GAMES: ON-ROAD EMISSION FACTORS AND AMBIENT BLACK CARBON .................................................................................................. 29 3.1 Introduction ............................................................................................ 29 3.2 Traffic control and other emission control measures ............................. 31 3.3 Methodology ........................................................................................... 33 3.3.1 Ambient Monitoring ........................................................................ 33 3.3.2 On-road Monitoring ........................................................................ 34 3.3.3 Emission Factors (EF) ..................................................................... 37 3.4 Results and Discussion ........................................................................... 39 3.4.1 Emission factors .............................................................................. 39 3.4.2 Community BC observations at 6m and 20m elevation .................. 42 v 3.4.3 Comparison of BC concentrations on traffic restriction and non restriction days ...................................................................................................... 47 3.4.4 Comparison of BC concentrations in 2008 and previous years ...... 48 3.5 Conclusion .............................................................................................. 51 4. CHAPTER 4 ON-ROAD EMISSION FACTOR DISTRIBUTIONS OF INDIVIDUAL DIESEL VEHICLES IN AND AROUND BEIJING, CHINA ....... 54 4.1 Introduction ............................................................................................ 54 4.2 Methodology ........................................................................................... 55 4.2.1 On-road measurements .................................................................... 55 4.2.2 Data analysis ................................................................................... 60 4.3 Results and discussion ............................................................................ 65 4.3.1 Sampled vehicle statistics ............................................................... 65 4.3.2 Observations from on-road measurements ...................................... 67 4.3.3 Emission Factors ............................................................................. 68 4.3.4 Factors affecting the EFs calculation and method limitations ........ 79 4.4 Conclusion .............................................................................................. 80 5. CHAPTER 5 NITROGEN OXIDES AND BLACK CARBON EMISSION FACTOR DISTRIBUTIONS OF INDIVIDUAL ON-ROAD DIESEL VEHICLES IN TWO CHINESE CITIES ...................................................................................