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Atmospheric Chemistry of Polyfluorinated Compounds: Long-Lived Greenhouse Gases and Sources of Perfluorinated Acids

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Atmospheric Chemistry of Polyfluorinated Compounds: Long-Lived Greenhouse Gases and Sources of Perfluorinated Acids ATMOSPHERIC CHEMISTRY OF POLYFLUORINATED COMPOUNDS: LONG-LIVED GREENHOUSE GASES AND SOURCES OF PERFLUORINATED ACIDS by Cora J. Young A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Department of Chemistry University of Toronto © Copyright by Cora J. Young 2010 Atmospheric chemistry of polyfluorinated compounds: Long-lived greenhouse gases and sources of perfluorinated acids Doctor of Philosophy Degree, 2010 Cora J. Young Department of Chemistry, University of Toronto ABSTRACT Fluorinated compounds are environmentally persistent and have been demonstrated to bioaccumulate and contribute to climate change. The focus of this work was to better understand the atmospheric chemistry of poly- and per-fluorinated compounds in order to appreciate their impacts on the environment. Several fluorinated compounds exist for which data on climate impacts do not exist. Radiative efficiencies (REs) and atmospheric lifetimes of two new long-lived greenhouse gases (LLGHGs) were determined using smog chamber techniques: perfluoropolyethers and perfluoroalkyl amines. Through this, it was observed that RE was not directly related to the number of carbon-fluorine bonds. A structure-activity relationship was created to allow the determination of RE solely from the chemical structure of the compound. Also, a novel method was developed to detect polyfluorinated LLGHGs in the atmosphere. Using carbotrap, thermal desorption and cryogenic extraction coupled to GC-MS, atmospheric measurements can be made for a number of previously undetected compounds. A perfluoroalkyl amine was detected in the atmosphere using this technique, which is the compound with the highest RE ever detected in the atmosphere. Perfluorocarboxylic acids (PFCAs) are water soluble and non-volatile, suggesting they are not susceptible to long-range transport. A hypothesis was derived to explain the ubiquitous distribution of these compounds involving atmospheric formation of PFCAs from volatile precursors. Using smog chamber techniques with offline analysis, perfluorobutenes and fluorotelomer iodides were shown to yield PFCAs from atmospheric oxidation. Dehydrofluorination of perfluorinated alcohols (PFOHs) is poorly understood in the mechanism of PFCA atmospheric formation. Using density functional techniques, overtone-induced photolysis was shown to lead to dehydrofluorination of PFOHs. In the presence of water, this mechanism could be a sink of PFOHs in the atmosphere. Confirmation of the importance of volatile precursors was derived from examination of snow from High Arctic ice caps. This ii provided the first empirical evidence of atmospheric deposition. Through the analytes observed, fluxes and temporal trends, it was concluded that atmospheric oxidation of volatile precursors is an important source of PFCAs to the Arctic. iii ACKNOWLEDGEMENTS Without the assistance and support of numerous people, it would have been impossible for me to produce this thesis. My words cannot express the gratitude I feel toward my collaborators, mentors, friends and family, but I will do my best to communicate my appreciation here. First and foremost, I would like to thank my supervisor, Scott Mabury, from whom I have learned so much—both within and outside the realm of chemistry. I am also grateful to my committee members, Jon Abbatt and Frank Wania, as well as Jamie Donaldson and Jen Murphy. Each of you has been so supportive in providing advice on specific scientific problems as well as career issues. This work was not mine alone, but consisted of contributions from collaborators and co- authors. I would particularly like to thank Tim Wallington and Mike Hurley who were integral to most of my publications and who taught me so much. Thanks also to Jamie for helping me to think outside the box of my planned dissertation and assisting me in producing work using molecular modelling. Finally, thanks to my Arctic collaborators, Vasile Furdui, James Franklin, Derek Muir, Dan Walsh and the late Roy “Fritz” Koerner. The project was a huge undertaking and could never have been accomplished without your contributions. Members of the Mabury group and environmental chemistry, both past and present, have been colleagues as well as friends. I feel so lucky to have been part of such a wonderful group of people. Dr. Monica Lam, my original Mabury group mentor—thank you for teaching me so much about conducting experiments and being efficient. Derek, the man who always knows the answer—I hope you will be available when I have questions in the future! Erin, thanks for being such an amazing friend and for all the “water breaks”. Amy, Holly, Anne, Pablito, Naomi and Sarah—thanks for being always there to bounce ideas and vent! My compatriots, Amila, Craig, Jessica, Tara and Zam—thanks for always providing support, advice, a shoulder to cry on or a glass of wine when the going got tough. Dr. De Silva (aka “Abrupt Spice”), my GC-MS and life guru—your daily advice sessions are missed already! Craig, I can’t imagine a time when I won’t be able to roll back my chair and talk to you or ask you a question—expect to hear from me multiple times per day! Jess, my doppelganger, thanks for teaching me so much about life attitudes and balance—I aspire to be more like you. Tara, thank you for always smiling and for only needing to drink two glasses of wine! Zam, thanks for the inappropriate questions and for always being so positive. iv Of course, thanks to my family: my parents and Teresa, who inspired my curiosity and interest in science and have believed in me from the very beginning. It’s impossible to articulate how much this has meant to me over the years. Thank you for the love and support and for always making sure I wasn’t going hungry! My “non-chemistry” friends, Subha, Andrea and Erin—thank you for supporting me, even when you had no idea what I was talking about. Trevor, last but not least! I am so lucky to have you in my life—without your love, encouragement and engineering and management skills, I would never have made it. v TABLE OF CONTENTS CHAPTER ONE – Polyfluorinated Compounds as Long-Lived 1 Greenhouse Gases 1.1 Introduction 2 1.2 Assessing climate impact 3 1.2.1 Radiative forcing 3 1.2.2 Radiative efficiency 3 1.2.3 Global warming potential 4 1.2.4 Importance of halogenated compounds as long-lived 5 greenhouse gases 1.3 International agreements affecting long-lived greenhouse gases 6 1.3.1 Kyoto Protocol 6 1.3.2 Montreal Protocol 6 1.3.3 Other agreements 7 1.4 Atmospheric measurements of halogenated long-lived greenhouse gases 7 1.4.1 Methods 7 1.4.2 Observed levels 7 1.4.3 Global networks and trends 8 1.5 Goals and hypotheses 9 1.6 Sources cited 10 CHAPTER TWO – Atmospheric Perfluorinated Acid Precursors: 12 Chemistry, Occurrence and Impacts 2.1 Introduction 13 2.2 Mechanisms of atmospheric formation of perfluorinated acids (PFAs) 15 2.2.1 Perfluorocarboxylic acids (PFCAs) 15 2.2.1.1 Mechanisms for atmospheric formation of perfluoroacyl 15 halides 2.2.1.1.1 Chemistry of Perfluoroacyl halides 15 2.2.1.1.2 Mixed halide mechanism 16 2.2.1.1.3 Perfluorinated radical mechanism 17 2.2.1.2 Mechanisms for direct atmospheric formation of 18 perfluorocarboxylic acids (PFCAs) 2.2.1.2.1 Perfluoroacyl peroxy radical mechanism 18 2.2.1.2.2 Perfluorinated aldehyde (PFAL) hydrate 21 mechanism 2.2.2 Perfluorosulfonic acids (PFSAs) 21 2.3 Chemistry of perfluorinated acid (PFA) precursors 22 2.3.1 Fluorotelomer and related compounds 22 2.3.1.1 Perfluorinated aldehydes (PFALs) 24 2.3.1.2 Fluorotelomer aldehydes (FTALs) 30 2.3.1.3 Fluorotelomer alcohols (FTOHs) 32 2.3.1.4 Fluorotelomer olefins (FTOs) 35 2.3.1.5 Fluorotelomer acrylate (FTAc) 37 vi 2.3.2 Perfluoroalkanesulfonamides 39 2.3.2.1 N-alkyl-perfluoroalkanesulfonamides (NAFSA) 39 2.3.2.2 N-alkyl-perfluoroalkanesulfamidoethanols (NAFSE) 41 2.4 Atmospheric sources and levels 43 2.4.1 Volatile fluorinated anaesthetics 43 2.4.1.1 Potential sources to the atmosphere 43 2.4.2 Hydrochlorofluorocarbons (HCFCs) 44 2.4.2.1 Potential sources to the atmosphere 44 2.4.2.2 Atmospheric concentrations 44 2.4.3 Hydrofluorocarbons (HFCs, non-telomer based) 44 2.4.3.1 Saturated hydrofluorocarbons (HFCs) 44 2.4.3.1.1 Potential sources to the atmosphere 44 2.4.3.1.2 Atmospheric concentrations 45 2.4.3.2 Hydrofluoroolefins (HFOs) 45 2.4.3.2.1 Potential sources to the atmosphere 45 2.4.4 Fluorotelomer compounds 45 2.4.4.1 Potential sources to the atmosphere 45 2.4.4.2 Atmospheric concentrations 46 2.4.4.2.1 FTOHs 47 2.4.4.2.2 FTOs 47 2.4.4.2.3 FTAcs 47 2.4.5 Perfluorosulfonamides 48 2.4.5.1 Potential sources to the atmosphere 48 2.4.5.2 Atmospheric concentrations 49 2.4.5.2.1 NAFSA 49 2.4.5.2.2 NAFSE 49 2.5 Impact of precursors on environmental perfluorinated acid (PFA) levels 49 2.5.1 Trifluoroacetic acid (TFA) 49 2.5.2 Perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid 51 (PFOA) and perfluorononanoic acid (PFNA) 2.5.3 Long-chained perfluorocarboxylic acids (PFCAs) 54 2.6 Goals and Hypotheses 55 2.7 Sources Cited 56 CHAPTER THREE – Atmospheric Lifetime and Global Warming 67 Potential of a Perfluoropolyether C.J. Young, M.D. Hurley, T.J. Wallington and S.A. Mabury Environ. Sci. Technol. 2006 40:2242-2246 3.1 Introduction 68 3.2 Experimental 69 3.2.1 Chemical preparation 69 3.2.2 Kinetics 69 3.3 Results and Discussion 70 3.3.1 Kinetics 70 3.3.2 Photolysis of PFPMIE 72 3.3.3 IR spectrum and global warming potential of PFPMIE 74 vii 3.4 Acknowledgements 78 3.5 Sources Cited 79 CHAPTER FOUR – Molecular Structure and Radiative Efficiency of 80 Fluorinated Ethers: A Structure-Activity Relationship C.J.
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