AEROSOL CONTRIBUTIONS TO SPELEOTHEM GEOCHEMISTRY Jonathan Dredge A thesis submitted to the University of Birmingham for the University of Birmingham and University of Melbourne joint degree of DOCTOR OF PHILOSOPHY School of Geography, Earth and Environmental Sciences College of Life and Environmental Sciences University of Birmingham April 2014 University of Birmingham Research Archive e-theses repository This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder. Abstract There is developing interest in cave aerosols due to the increasing awareness of their impacts on the cave environment and speleothems. This study presents the first multidisciplinary investigation into cave aerosols and their potential contribution to speleothem geochemistry. Aerosols are shown to be sourced from a variety of external emission processes, and transported into cave networks. Both natural (marine sea-spray, terrestrial dust) and anthropogenic (e.g. vehicle emissions) aerosol emissions are detected throughout caves. Internal cave aerosol production by human disruption has also been shown to be of importance in caves open to the public. Aerosols produced from floor sediment suspension and release from clothing causes short term high amplitude aerosol suspension events. Cave aerosol transport, distribution and deposition are highly variable depending on cave situation. Cave morphology, ventilation, and environmental conditions will influence how aerosols are distributed through cave networks. Aerosol deposition monitoring in Obir Cave, Austria has shown the significance of cave chamber size in aerosol transport, with large open chambers presenting higher levels of deposition. Modern monitoring of suspended aerosol concentrations, CO2 and temperature in Gough’s Cave, Cheddar Gorge have presented a strong relationship with cave ventilation processes. Temporal variations of aerosol levels have demonstrated the ability of aerosol monitoring to record seasonal ventilation shifts, beyond anthropogenic influences. Aerosol minima (based II on 24 hours) provide a representation of natural aerosol baseline conditions without diurnal anthropogenic influences. Aerosols have shown a quicker recovery to natural background levels when compared to CO2 and T, making aerosols a sensitive and effective monitoring tool. When used in combination with more established monitoring methods, suspended aerosol monitoring is a beneficial addition to cave environmental studies. Theoretical modelling and calculations based on modern aerosol monitoring have established that aerosol contributions are highly variable. In some instances, modern aerosol supply is sufficient to account for speleothem geochemistry concentrations entirely. Aerosol contributions are of greatest significance under slow growth or hiatus scenarios and high aerosol deposition scenarios. Geochemical and stratigraphical analysis of a flowstone core from Gibraltar has highlighted the importance of hiatus events for future aerosol studies. Hiatus events provide a unique opportunity to investigate the type and amount of aerosol deposition and accumulation. Marine aerosol contributions have been quantified in the Gibraltar flowstone core and account for 18.5% of speleothem Sr. Sr isotopic analysis has confirmed the significance of marine aerosol contributions. Flowstone analysis has also demonstrated the ability of speleothems to record shifts in the supply of highly radiogenic terrestrial dust. Bio-aerosol deposits and bacterial colonisation have been identified as a potential source of trace element bioaccumulation and flowstone coloration in Yarrangobilly Caves, Australia. Bio-aerosols have shown to be deposited throughout cave networks. Inorganic aerosol deposition may provide a nutrient supply to cave surfaces allowing for, and sustaining microbial colonisation. III Acknowledgments Firstly, I would like to thank my supervisors Ian Fairchild and Roy Harrison at the University of Birmingham, as well as Jon Woodhead and John Hellstrom at the University of Melbourne. Further special gratitude goes to Ian for his extensive help and communication in developing the data analysis and writing of my thesis. Also, thank you to Frank McDermott and James Bendle for their comments. So many people have helped in field work, sampling and chemical analysis during my PhD. I would like to thank: Angel Fernandez-Cortes, Sergio Sanchez-Moral and Valme Jurado for field work and sampling in Spain; Christoph Spötl and Harald Langer for aerosol sampling in Obir Cave, Austria; John Gunn and Cheddar Gorge and Cave Longleat Enterprises Limited Team for field work and guidance in Goughs Cave; Dave Mattey and the Gibraltar Ornithological & Natural History Society Caving group for fieldwork assistance, caving guidance and hosting me; Pauline Treble for organising and welcoming me to field campaigns in Yarrangobilly Caves, Australia; Regina Roach, Andy Spate, George Bradford and the Yarrangobilly Kosciuszko National Park team for guidance, assistance with field work and aerosol sampling in Yarrangobilly Caves. My gratitude goes out to everyone that helped with laboratory work, training and guidance: Roland Maas, Alan Grieg, and Robyn Pickering at the University of Melbourne; Chris Stark for PAH analysis and training, and Gillian Kingston and Eimear Orgill for assistance in the Public Health department laboratories at the University of Birmingham. Neil Holloway, IV Wolfgang Müller, David Lowry, Matthew Thirlwall, Nathalie Grassineau and Sue Hall at Royal Holloway, University of London; Roberta Zangrando, Carlo Barbante, and those that assisted with Organic analysis at the Institute for the Dynamics of Environmental Processes, Venice; Rich Boden from the University of Plymouth for Yarrangobilly bacterial analysis. I would like to credit Carol Tadros for Yarrangobilly drip water data and Peter Wynn and Andrew Smith for aerosol distribution data. I would like to thank everyone involved from the University of Birmingham, University of Melbourne and Universitas 21 for help in setting up the joint PhD. Research for this thesis was supported by the Natural Environment Research Council (grant number: NE/I 528226/1) and the University of Birmingham. Additional support was provided by a Cave Science and Technology Research Initiative grant from the British Cave Research Association (BCRA). Finally, thanks to everyone at the University of Melbourne who made the transition and my time there so comfortable. A shout out to everyone from Office of 425, present and past, for their contributions to my thesis and mental well being. A big thank you to my Mum Adriana Dredge, and my family. Props to Megan Renoir for her unfaltering support, for which I traded way more knowledge on aerosols and speleothems than she ever wanted. V Thesis contents Chapter 1. Introduction 1.1. Aerosol processes ........................................................................................................... 1 1.1.1. Aerosol sampling ..................................................................................................... 4 1.1.2. Aerosol characterisation .......................................................................................... 4 1.2. Flowstones ...................................................................................................................... 8 1.2.1. Flowstone formation ................................................................................................ 9 1.2.2. Flowstone geochronology ..................................................................................... 12 1.2.3. Flowstone (speleothem) palaeoenvironmental proxies ......................................... 12 1.3. Previous flowstone studies ........................................................................................... 17 1.3.1. Flowstone palaeoclimate reconstructions .............................................................. 17 1.3.2. Flowstone archaeological importance ................................................................... 18 1.4. Thesis aims and objectives ........................................................................................... 20 1.6. Thesis structure ............................................................................................................ 20 Chapter 2. Cave aerosols: distribution and contribution to speleothem geochemistry 2.1. Introduction .................................................................................................................. 24 2.2. Methods ........................................................................................................................ 31 2.2.1. Sampling ................................................................................................................ 32 2.2.2. Extraction and analysis .......................................................................................... 37 2.3. Cave aerosol processes ................................................................................................ 42 2.3.1. Cave aerosol sources