UNIVERSITY OF CINCINNATI Date:___________________ I, _________________________________________________________, hereby submit this work as part of the requirements for the degree of: in: It is entitled: This work and its defense approved by: Chair: _______________________________ _______________________________ _______________________________ _______________________________ _______________________________ Composition and Formation Mechanism of Diesel Particulate Matter Associated with Various Factors from A Non-road Diesel Generator A dissertation submitted to the Division of Research and Advanced Studies of University of Cincinnati In partial fulfillment of the requirements for the degree of DOCTORATE OF PHILOSOPHY (Ph.D.) in the Department of Environmental Engineering of the College of Engineering 2006 by Fuyan Liang B.S. (Environ. Eng.), Tsinghua University, P.R. China, 2000 M.S. (Environ. Eng.), Tsinghua University, P.R. China, 2002 Committee Chair: Mingming Lu, Ph.D. ABSTRACT Diesel engines emit large quantities of fine particles to the atmosphere, on which numerous organic compounds are absorbed, such as PAHs, nitro-PAHs, and sulfur-containing PAHs. It is well established that exposure to PAHs and their derivatives may represent a high risk for human health. Considering its organic fractions and inhalable properties, diesel particulate matter (DPM) is considered a probable human carcinogen. The concerns of DPM health effects have simulated studies on DPM chemical composition and its formation mechanisms. This dissertation presents the results of an experimental investigation into the composition and formation mechanism of DPM at various engine operating conditions and fuel sulfur contents. The influence of sampling methods also was examined. High volume dilution sampling and ultrasonic assisted extraction methods were developed for collection and extraction of DPM. Gas chromatography/mass spectrometry (GC/MS) with selective ion chromatogram (SIC), tandem mass spectrometry (MS/MS) with selected ion monitoring (SIM), and gas chromatography with atomic emission detection (GC/AED) were applied for determination of numerous hydrocarbons and organosulfur species in diesel emissions. The results of the comparisons between DPM extracts, diesel fuel, and engine oil indicate that diesel fuel, engine oil, and combustion process were the three major sources of alkanes, organic acids, and PAHs and alkylated PAHs in DPM, respectively. As expected, the distribution of organic compounds between gas and particle phase diesel emissions was directly correlated with their vapor pressures. Adsorption of gas phase organics onto diesel particles was the predominant mechanism controlling the formation of diesel aerosols. This research revealed strong effects from engine operation conditions and sampling methods on the organic composition and formation mechanism of DPM, as well as the compound distribution. Higher engine loads caused the increase in DPM emission rate, its elemental carbon fraction, and the heavier components, which were pyrogenic species, formed during combustion processes, and may present greater health risks. The comparison between the results for dilution method and stack sampling method demonstrated that the dilution process significantly increased the organic fraction of DPM through the condensation of gas-phase organics. The research outcomes provide important knowledge for understanding DPM nature and formation mechanisms. ACKNOWLEDGEMENTS First and foremost, I would like to express my deepest gratitude to my advisor Dr. Mingming Lu for her guidance, support, and friendship throughout my Ph.D. study. I am in eternal debt to her for the various ways in which she supported me. I am also very grateful to Dr. Tim C. Keener, Dr. M. Eileen Birch, and Dr. George Sorial for serving on my committee and for providing me with very valuable comments and feedback. Although they did not serve as members of my committee, I would like to thank Dr. Soon-Jai Khang and Dr. Sumana Keener for their advice and support. I would like to acknowledge the National Institute for Occupational Safety and Health for the use of their instrument and facilities at the laboratory in Cincinnati, Ohio. In particular, I want to thank Dr. M. Eileen Birch for the loaning of the instrumentation used for my research, for her help, friendship, great advice, and technical support throughout the method development and sample measurements. This work is dedicated to my parents and my brother in China. They have always been so supportive and loving. Thank you very much. Because having you in mind, I could finish this mission. I hope one day I can reward you for all the time I was far from you. My acknowledgement is extended to my friends at UC: Zhangli Cai, Kai zhang, Qiang Zhang, Peng Jin, Qiuli Lu, Kessinee, and Phirun. I thoroughly enjoyed their friendship. To Zifei, for the help with sampling in cool and hot weathers, and for driving me wherever needed. To Jun, for his kindness and help with the GC/MS questions, problems, and skills. But most especially this work is dedicated to my dearest Hao, who always showed me the power of unconditional love. With him I have walked most of my path here in Cincinnati. I cannot thank him enough for his love, his friendship, his support in the worst moments, his help with my work and for feeding me with the most delicious food for so many years. Without you I would have never accomplished this task. Also I would like to thank the National Institute for Occupational Safety and Health for their financial support. TABLE OF CONTENTS Chapter 1 INTRODUCTION.................................................................................................... 1 1.1 BACKGROUND & MOTIVATION .......................................................................... 1 1.2 LITERATURE REVIEW......................................................................................... 4 1.2.1 Diesel Fuel Composition....................................................................... 4 1.2.2 Engine Oil Composition ....................................................................... 8 1.2.3 Overview of DPM Composition ........................................................... 9 1.2.4 DPM Formation .................................................................................. 11 1.2.5 DPM Measurement Methods .............................................................. 12 1.2.6 Effects of Testing Conditions on DPM............................................... 14 1.3 RESEARCH OBJECTIVES ................................................................................... 15 1.4 REFERENCES .................................................................................................... 17 Chapter 2 EXPERIMENTAL DESIGN AND METHOD.................................................... 24 2.1 EXPERIMENTAL DESIGN................................................................................... 24 2.2 SAMPLING METHOD......................................................................................... 26 2.2.1 EPA Method 5..................................................................................... 26 2.2.2 Natural Dilution .................................................................................. 28 2.2.3 High Volume Dilution Sampling........................................................ 30 2.3 EXTRACTION METHOD ..................................................................................... 35 2.4 ANALYTICAL METHOD .................................................................................... 37 2.4.1 OC/EC Analysis.................................................................................. 37 2.4.2 Hydrocarbon Analysis with GC/MS................................................... 40 2.4.2.1 Instrument and Operating Parameters.................................. 40 2.4.2.2 Compound Identification and Quantification ...................... 41 2.4.2.3 Standard Compounds........................................................... 43 2.4.2.4 Quality Assurance and Quality Control............................... 46 2.5 EXPERIMENT ON SOURCE CONTRIBUTION TO DPM COMPOSITION .................... 47 2.6 REFERENCES .................................................................................................... 50 i Chapter 3 THE ORGANIC COMPOSITION OF DIESEL PARTICULATE MATTER, DIESEL FUEL AND ENGINE OIL OF A NON-ROAD DIESEL GENERATOR........................................................................................................ 56 3.1 INTRODUCTION .................................................................................................. 56 3.2 EXPERIMENTAL METHOD ................................................................................... 57 3.3 RESULTS AND DISCUSSION ................................................................................. 57 3.3.1 Chemical Composition........................................................................ 58 3.3.2 Alkanes ............................................................................................... 65 3.3.3 PAHs and Alkylated PAHs................................................................. 67 3.3.4 Alkylbenzenes..................................................................................... 69 3.3.5 Organic Acids ..................................................................................... 70 3.3.6 Isomer Distribution ............................................................................. 71 3.4 CONCLUSIONS...................................................................................................