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Investigating urban atmospheric chemistry using a time of flight chemical ionisation mass spectrometer A thesis submitted to the University of Manchester for the degree of Doctor of Philosophy in the Faculty of Science and Engineering 2018 Michael Priestley School of Earth and Environmental Sciences Blank page Contents Abstract ........................................................................................................................... 1 Declaration ...................................................................................................................... 2 Copyright Statement........................................................................................................ 3 Acknowledgements ......................................................................................................... 4 Alternative format thesis overview ................................................................................... 5 1. Introduction .............................................................................................................. 7 1.1. Climate and air quality ....................................................................................... 7 1.2. The urban atmosphere .................................................................................... 10 1.2.1. Volatile organic compounds (VOCs) ........................................................ 12 1.2.2. Oxidants ................................................................................................... 15 1.2.3. Oxidation .................................................................................................. 20 1.3. Air quality in the UK ......................................................................................... 24 1.4. Measuring the chemical composition of the urban atmosphere ....................... 28 1.4.1. Mass spectrometry ................................................................................... 29 1.4.2. Data acquisition and analysis ................................................................... 33 2. Aims and Objectives .............................................................................................. 46 3. Paper 1. Observations of isocyanate, amide, nitrate and nitro compounds from an anthropogenic biomass burning event using a ToF‐CIMS ............................................. 48 4. Paper 2. Observations of organic and inorganic chlorinated compounds and their contribution to chlorine radical concentrations in an urban environment in Northern Europe during the wintertime ......................................................................................... 50 5. Paper 3. Detection of highly oxidised molecules from the reaction of benzene + OH under different NOx conditions ....................................................................................... 53 6. Conclusions ........................................................................................................... 54 6.1. Future work ..................................................................................................... 58 Bibliography .................................................................................................................. 63 Appendix A. Co-authorship in peer reviewed publications ............................................. 74 Word count: 51,590 Blank page Abstract Atmospheric reactive trace gases perturb the climate system and air quality through many direct and indirect effects. The poor air quality they propagate is amplified in large urban centres where emissions and processing are highly variable, and large populations are exposed. Many chemical processes are poorly understood due to the highly complex interactions and variable composition of the urban atmosphere. These drive the development of new atmospheric measurement instruments that can reliably measure reactive trace gases of very low concentration with high temporal resolution. The iodide time of flight chemical ionisation mass spectrometer (ToF-CIMS) is one such instrument that is able to probe reactive atmospheric systems due to its high linearity of response, reproducibility, and its selectivity and sensitivity towards inorganic species, including chlorinated and brominated species, and multifunctional oxygenated organic species, all of which are of relevance for the study of urban air. An iodide ToF-CIMS was deployed at the University of Manchester for a two week period in October and November 2014 to assess its ability to detect trace gases relevant to climate and air quality. A biomass burning event (Guy Fawkes Night) was sampled, from which markers of combustion (HCN and HNCO) and other newly detected nitrogen containing species (amides) were quantified and their emission ratios (NEMR) to CO calculated. The HCN NEMR of 1.11 ± 0.62 ppt ppb-1, whilst low, is of a comparable order to other biomass burning studies. Chlorinated organics were also identified throughout the sample period. Their contribution to the steady state Cl radical budget was quantified and compared with the contribution from inorganic Cl species also measured. The detection of day time Cl2 suggests a photochemical mechanism is the cause of production and is a significant source of Cl throughout the day (74%), more so than ClNO2 (23%) when the shortwave (sw) radiation flux is large. The newly detected ClOVOCs are a negligible source of Cl under both low and high sw flux conditions (3%). The iodide ToF-CIMS was also deployed at the Jülich plant chamber where many products of benzene oxidation by OH under different NOx conditions were identified. These measurements were contrasted with a nitrate ToF-CIMS that exhibits a different compound detection selectivity. Detection overlap between instruments was observed, however different O:C ratios for species with the same carbon number were found. Products identified by iodide ToF-CIMS in the chamber were identified in the Manchester urban ambient dataset, if they contained 6 carbon atoms and had high N:C (0.3 - 0.5) and O:C ratios (1.5 – 2.0). This suggests the chamber may not be representative of ambient conditions. 1 Declaration No portion of the work referred to in the thesis has been submitted in support of an application for another degree of qualification of this or any other university of other institute of learning. 2 Copyright Statement i. The author of this thesis (including any appendices and/or schedules to this thesis) owns certain copyright or related rights in it (the “Copyright”) and s/he has given The University of Manchester certain rights to use such Copyright, including for administrative purposes. ii. Copies of this thesis, either in full or in extracts and whether in hard or electronic copy, may be made only in accordance with the Copyright, Designs and Patents Act 1988 (as amended) and regulations issued under it or, where appropriate, in accordance with licensing agreements which the University has from time to time. This page must form part of any such copies made. iii. The ownership of certain Copyright, patents, designs, trademarks and other intellectual property (the “Intellectual Property”) and any reproductions of copyright works in the thesis, for example graphs and tables (“Reproductions”), which may be described in this thesis, may not be owned by the author and may be owned by third parties. Such Intellectual Property and Reproductions cannot and must not be made available for use without the prior written permission of the owner(s) of the relevant Intellectual Property and/or Reproductions. iv. Further information on the conditions under which disclosure, publication and commercialisation of this thesis, the Copyright and any Intellectual Property and/or Reproductions described in it may take place is available in the University IP Policy (see http://documents.manchester.ac.uk/display.aspx?DocID=24420), in any relevant Thesis restriction declarations deposited in the University Library, The University Library’s regulations (see http://www.library.manchester.ac.uk/about/ regulations/) and in The University’s Policy on Presentation of Theses. 3 Acknowledgements I would like to express my immense gratitude to Prof. Carl Percival for his supervision and dedication to me and my work despite moving on to pastures new. I would also like to thank Prof. Hugh Coe for his supervision and guidance during the latter part of my time at Manchester. I would like to thank the National Environment Research Council (NERC) for the Doctoral Training studentship I received to fund my work. I also wish to thank past and present members of the Percival Group, Asan Bacak, Mike le Breton, Tom Bannan, Kimberly Leather, Stephen Worrall and Archit Mehra for their unyielding guidance and friendship. Thank you Ernesto Reyes-Villegas, Yu-Chieh ‘Danny’ Ting, Gillian Young, Nick Marsden, Hazel Jones and Waldemar Schledewitz. I am grateful to have shared on office with others who made the daily grind so much more enjoyable. Finally, thank you to my parents, for their constant support and encouragement, and to Hannah Josey for your ever present optimism and selfless dedication. 4 Alternative format thesis overview Measurements of trace gases relevant to air quality using a time of flight chemical ionisation mass spectrometer (ToF-CIMS). What species can the ToF-CIMS Which species can the ToF-CIMS detect under ambient conditions? observe that are relevant to urban oxidation? Observations of isocyanate, Observations of organic and amide, nitrate and nitro

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