ESTIMATES OF NITROUS OXIDE EMISSIONS FROM MOTOR VEHICLES AND THE EFFECTS OF CATALYST COMPOSITION AND AGING Contract No. 02-313 STATE OF CALIFORNIA AIR RESOURCES BOARD Final Report Prepared by Arthur M. Winer, Ph.D. Principal Investigator Environmental Health Sciences Department and Environmental Science and Engineering Program School of Public Health University of California, Los Angeles, California, 90095 (310) 206-1278 Eduardo Behrentz, D.Env. Co-Investigator Environmental Science and Engineering Program School of Public Health University of California, Los Angeles June 10, 2005 N2O Emissions from Motor Vehicles DISCLAIMER The statements and conclusions in this report are those of the contractor and not necessarily those of the California Air Resources Board. The mention of commercial products, their source, or their use in connection with material reported herein is not to be constructed as actual or implied endorsement of such products. i N2O Emissions from Motor Vehicles ii N2O Emissions from Motor Vehicles ACKNOWLEDGEMENTS The contributions of the California Air Resources Board staff, particularly Paul Rieger, who made invaluable suggestions and contributions throughout the project, and Hector Maldonado who acted as our Project Officer, were greatly appreciated. We also thank Richard Ling of the Monitoring and Laboratory Division who collected all emissions data from the 16th Vehicle Surveillance Program and who provided on-site training and support. We thank Margo Eaddy for her participation during the data collection process. We wish to acknowledge valuable contributions from Jerry Ho and Robin Lang of the Mobile Source Operations Division who provided logistical support during vehicle testing and data collection. We especially appreciated Shane Michael, the project’s Test Engineer, of the Mobile Source Operations Division for his professionalism and willingness to assist us throughout the study. Many of his contributions were key elements in the rapid progress and evolution of our research. We gratefully acknowledge support for this research by the California Air Resources Board. This report was submitted in partial fulfillment of ARB Contract No. 02-313, “Estimates of Nitrous Oxide Emissions from Motor Vehicles and the Effects of Catalyst Composition and Aging,” by the University of California, Los Angeles, School of Public Health, Environmental Health Sciences Department, under the sponsorship of the California Air Resources Board. Work was completed as of June 10, 2005. iii N2O Emissions from Motor Vehicles iv N2O Emissions from Motor Vehicles TABLE OF CONTENTS 1. EXECUTIVE SUMMARY............................................................................................................................ 1-1 2. INTRODUCTION, BACKGROUND, AND OBJECTIVES...................................................................... 2-1 2.1. PREVIOUS RESEARCH .............................................................................................................................. 2-1 2.2. BACKGROUND ......................................................................................................................................... 2-3 2.3. THE CATALYTIC CONVERTER.................................................................................................................. 2-4 2.4. FORMATION OF NITROUS OXIDE ............................................................................................................. 2-5 2.5. FTIR SPECTROSCOPY.............................................................................................................................. 2-7 2.6. EXHAUST EMISSION STANDARDS ............................................................................................................ 2-7 2.7. STATEMENT OF THE PROBLEM................................................................................................................. 2-9 2.8. OBJECTIVES AND HYPOTHESES ............................................................................................................... 2-9 2.8.1. Overall Objectives ............................................................................................................................. 2-9 2.8.2. Specific Objectives............................................................................................................................. 2-9 2.8.3. Hypotheses......................................................................................................................................... 2-9 3. EXPERIMENTAL METHODS AND INSTRUMENTATION ................................................................. 3-1 3.1. SUMMARY OF APPROACH........................................................................................................................ 3-1 3.2. RECRUITMENT OF VEHICLES ................................................................................................................... 3-1 3.3. VEHICLE TESTING ................................................................................................................................... 3-2 3.3.1. Vehicle Preparation........................................................................................................................... 3-2 3.3.2. Vehicle Setup ..................................................................................................................................... 3-2 3.3.3. Dynamometer Unit........................................................................................................................... 3-12 3.3.4. Horiba Constant Volume Sampler Collection System...................................................................... 3-12 3.3.5. Dynamometer Testing...................................................................................................................... 3-14 3.3.6. Driving cycles .................................................................................................................................. 3-14 3.4. CATALYST STUDY MEASUREMENTS...................................................................................................... 3-18 3.5. INSTRUMENTATION ............................................................................................................................... 3-22 3.5.1. FTIR Spectrometer........................................................................................................................... 3-22 3.5.2. Chemiluminescence Analyzer .......................................................................................................... 3-23 3.5.3. Flame Ionization Analyzer............................................................................................................... 3-23 3.5.4. Infrared Analyzer............................................................................................................................. 3-23 3.5.5. Air-to-Fuel Ratio Analyzer .............................................................................................................. 3-23 3.5.6. Temperature Measurements ............................................................................................................ 3-23 3.6. ANALYSIS OF DILUTE EXHAUST SAMPLES BY FTIR.............................................................................. 3-23 3.7. FUEL CHARACTERISTICS ....................................................................................................................... 3-24 v N2O Emissions from Motor Vehicles TABLE OF CONTENTS (con't) 3.8. QUALITY CONTROL AND QUALITY ASSURANCE PROCEDURES.............................................................. 3-24 3.8.1. Quality Control................................................................................................................................3-25 3.8.2. Uncertainty in Dilute Exhaust Analyses .......................................................................................... 3-25 3.8.3. Linearity........................................................................................................................................... 3-26 3.8.4. Limit of Detection ............................................................................................................................ 3-27 4. PILOT STUDY RESULTS............................................................................................................................ 4-1 4.1. REGRESSION ANALYSIS........................................................................................................................... 4-1 4.1.1. Odometer Readings............................................................................................................................ 4-4 4.2. EFFECT OF CATALYST TYPE .................................................................................................................... 4-4 4.3. EFFECT OF PRE-CATALYST ...................................................................................................................... 4-6 4.4. EFFECT OF VEHICLE TYPE ....................................................................................................................... 4-6 4.5. EFFECT OF DRIVING CYCLE..................................................................................................................... 4-6 4.6. EFFECT OF PHASE AND CATALYST TEMPERATURE ................................................................................... 4-7 4.7. OTHER VARIABLES.................................................................................................................................