Atmospheric Chemistry of Polyfluorinated Compounds: Long-lived Greenhouse Gases and ...

247 Pages·2009·10.44 MB·English

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
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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.
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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.
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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.

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TABLE OF CONTENTS

CHAPTER ONE – Polyfluorinated Compounds as Long-Lived 1
Greenhouse Gases

1.1 Introduction 2
1.2 Asesing climate impact 3
1.2.1 Radiative forcing 3
1.2.2 Radiative eficiency 3
1.2.3 Global warming potential 4
1.2.4 Importance of halogenated compounds as long-lived 5
grenhouse 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 agrements 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 2
2.3.1 Fluorotelomer and related compounds 2
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
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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) 4
2.4.2.1 Potential sources to the atmosphere 44
2.4.2.2 Atmospheric concentrations 4
2.4.3 Hydrofluorocarbons (HFCs, non-telomer based) 44
2.4.3.1 Saturated hydrofluorocarbons (HFCs) 4
2.4.3.1.1 Potential sources to the atmosphere 4
2.4.3.1.2 Atmospheric concentrations 45
2.4.3.2 Hydrofluorolefins (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 5
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 Discusion 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
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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. Young, M.D. Hurley, T.J. Wallington and S.A. Mabury
J. Geophys. Res. 2008 113:D24301

4.1 Introduction 81
4.2 Methods 83
4.2.1 Experimental details 83
4.2.2 Computational details 83
4.2.3 Determination of radiative eficiency 84
4.3 Results and Discusion 85
4.3.1 Experimental infrared cros-sections 85
4.3.2 Validity of computed spectra 8
4.3.3 Development and utility of the SAR 88
4.3.4 Radiative efficiency and molecular structure 93
4.4 Conclusions 96
4.5 Acknowledgements 97
4.6 Sources Cited 98

CHAPTER FIVE – Perfluoroalkyl Amines: A New Class of Long-Lived 101
Greenhouse Gases

C.J. Young, M.D. Hurley, T.J. Wallington and S.A. Mabury

5.1 Introduction 102
5.2 Methods 102
5.2.1 Infrared absorption measurements 102
5.2.2 Determination of radiative eficiency 103
5.2.3 Physical properties and use of multi-species model 103
5.2.4 Air sample collection and analysis 103
5.3 Results and Discusion 104
5.3.1 Infrared spectrum and radiative efficiency 104
5.3.2 Physical properties and impact of ionization 105
5.3.3 Atmospheric lifetime of PFAms 106
5.3.4 Atmospheric detection of PFBAm 107
5.4 Environmental Implications 109
5.5 Acknowledgements 1
5.6 Sources Cited 12

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CHAPTER SIX – Atmospheric Chemistry of Perfluorobutenes 114
(CF3CF=CFCF3 and CF3CF2CF=CF2): Kinetics and Mechanisms
of Reactions with OH Radicals and Chlorine Atoms, IR Spectra,
Global Warming Potentials, and Oxidation to Perfluorocarboxylic Acids

C.J. Young, M.D. Hurley, T.J. Wallington and S.A. Mabury
Atmos. Env. 2009 43:3717-3724

6.1 Introduction 115
6.2 Methods 15
6.2.1 Chemicals 15
6.2.2 Kinetics 16
6.2.3 Products 17
6.3 Results and Discusion 17
6.3.1 Kinetics of reactions with Cl atoms 117
6.3.2 Kinetics of reactions with OH radicals 119
6.3.3 Products of Cl atom- and OH radical-initiated oxidation of 121
CF3CF=CFCF3 and CF3CF2CF=CF2
6.3.4 Proposed oxidation mechanisms 125
6.3.5 Infrared spectra and radiative efficiency of CF3CF=CFCF3 126
and CF3CF2CF=CF2
6.4 Atmospheric Implications 128
6.5 Acknowledgements 130
6.6 Sources Cited 131

CHAPTER SEVEN - Atmospheric Chemistry of 4:2 Fluorotelomer Iodide 134
(n-C4F9CH2CH2I): Kinetics and Products of Photolysis and Reaction
with OH Radicals and Cl Atoms

C.J. Young, M.D. Hurley, T.J. Wallington and S.A. Mabury
J. Phys. Chem. A 2008 112:13542-13548

7.1 Introduction 135
7.2 Experimental 136
7.2.1 Smog chamber methods 136
7.2.2 Offline sample collection and analysis 137
7.2.3 UV Spectral measurements and photolysis rate calculations 138
7.3 Results and Discusion 138
7.3.1 Kinetics of the Cl + 4:2 FTI reaction 138
7.3.2 Kinetics of the OH + 4:2 FTI reaction 139
7.3.3 Products of Cl + 4:2 FTI reaction 141
7.3.4 UV spectra and photolysis kinetics 143
7.3.5 Photolysis Products 14
7.4 Atmospheric Implications 146
7.4.1 FTI lifetime 146
7.4.2 Oxidation and photolysis products 147
7.4.3 Formation of PFCAs 148
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7.5 Acknowledgements 150
7.6 Sources Cited 151

CHAPTER EIGHT – Overtone-Induced Degradation of Perfluorinated 154
Alcohols in the Atmosphere

C.J. Young and D.J. Donaldson
J. Phys. Chem A. 2007 111:13466-13471

8.1 Introduction 15
8.2 Methods 157
8.3 Results and Discusion 158
8.3.1 Alcohol-water complexes 158
8.3.2 Overall features of the reactions 160
8.3.3 Overtone-induced degradation 163
8.4 Atmospheric Implications 16
8.5 Acknowledgements 168
8.6 Sources Cited 169

CHAPTER NINE – Perfluorinated Acids in Arctic Snow: New 173
Evidence for Atmospheric Formation

C.J. Young, V.I. Furdui, J. Franklin, R.M. Koerner, D.C.G. Muir and S.A. Mabury
Environ. Sci. Technol. 2007 41:3455-3461. Featured on May 15, 2007 cover

9.1 Introduction 174
9.2 Experimental 175
9.2.1 Chemicals 175
9.2.2 Sample colection 176
9.2.3 Sample preparation and analysis 176
9.3 Results and Discusion 178
9.3.1 QA/QC 178
9.3.2 Dating Arctic Snow 178
9.3.3 Concentrations of PFAs in arctic snow 178
9.3.4 Efects of anual melting 181
9.3.5 Fluxes of PFAs to the Arctic 181
9.3.6 Sources of PFAs to the Arctic 182
9.4 Acknowledgements 186
9.5 Sources Cited 187

CHAPTER TEN – Summary and Future Directions 190

10.1 Conclusions 191
10.2 Future Directions 193
10.2.1 Perfluoroalkyl amines 193
10.2.2 Atmospheric chemistry of new long-lived greenhouse gases 193
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