FLY-ASH PARTICLES IN LAKE SEDIMENTS: EXTRACTION, CHARACTERISATION & DISTRIBUTION. Thesis submitted for the degree of Doctor of Philosophy in the University of London by Neil Leslie Rose University College London May 1991 1 ProQuest Number: 10609404 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 10609404 Published by ProQuest LLC(2017). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 ABSTRACT Fly-ash particles produced from the high temperature combustion of fossil-fuels are found in high concentrations in the lake sediments of regions of high acid deposition. The sediment record of these particles showing the onset of industrialisation correlates well with the record of acidification as indicated by diatom analysis. There are two types of fly-ash particle; spheroidal carbonaceous particles produced from the incomplete combustion of the fossil-fuel and inorganic ash spheres formed by the fusing of mineral inclusions present within the fuel. Procedures were developed to extract both types of particle from lake sediments. These involved selective chemical attack to remove unwanted sediment fractions thus enabling quick and accurate particle enumeration. A reference data-set of carbonaceous particle surface chemistries was produced using EDS measurements and a fuel-type characterisation developed using multivariate statistics. This characterisation allocated over 97% of the particles to the correct fuel-type. These methods were then applied to a series of sediment cores to study temporal changes in particle deposition and spatial trends over Scotland. The concentrations of both particle types in sediment cores correlate well to fossil- fuel combustion histories, and the characterisation of the carbonaceous particles from a 210Pb-dated core from a north London lake showed good agreement with the change in coal and oil use through time in the area. Spatial trends were studied using surface sediments from 94 lakes in Scotland and the north of England. These showed higher concentrations near industrial areas and generally good agreement with sulphur deposition data. Characterisation revealed two areas where above average concentrations of oil particles occurred, indicating source areas outside the country to the east and the south-west There is potential to extend this characterisation to other fossil-fuel types such as peat, lignite and brown coal and to apply the techniques to a range of environmental questions in Britain, Europe and on a global scale. 2 ACKNOWLEDGEMENTS. Many people have aided and abetted this project and I would especially like to thank all the members of the Palaeoecology Research Unit for their friendship and buying me drinks when necessary. In particular I would like to thank my supervisor Rick Battarbee for his encouragement and guidance throughout. I am also grateful to the following people: Don Monteith, Simon Patrick, Julie Simpson, Helen Bennion, Tim Allott, Viv Jones and Roger Flower for their help with the fieldwork; Steve Juggins for all his help and advice with the computing and statistics and for reading various versions of Chapter 3 and to Martin Munro and Tony Stevenson for their comments on computing matters; Peter Street (formerly of CERL at Leatherhead) for his useful advice in the very early stages; John Watt of Imperial College, London for all his time with the EDS analyses and for reading a few sections of this work; Annette Kreiser, Nigel Cameron, Paul Schooling and Bill Campbell for ’top tips’ in the use of MAPICS; Ingemar Renberg, Maria Wik and Judi Natkanski for discussing ideas; Cath Fletcher for, amongst other things, proof-reading the chapters; Tim Aspden, Robert Bradbrook and Louise Saunders of the Geography Department Cartographic Unit for drawing most of the diagrams; Messrs’ Page, Plant, Bonham and Jones for many hours company during particle counting. This project was partially funded by the Central Electricity Generating Board, and the Department of the Environment. Last but certainly not least, I would like to thank my parents for their continuing support and encouragement. 3 Title Page 1 Abstract 2 Acknowledgements 3 Contents 4 List of Figures 8 List of Plates 14 List of Tables 15 Chapter One Introduction. 18 1.1. Particle formation 18 1.2. Fly-ash particles in the environment 21 1.3. Fly-ash particles in lake sediments 24 1.4. Outline of the thesis. 25 Chapter Two Sites and Methods. 30 2.1. Site selection 30 2.1.1. Sites for spatial distribution studies 30 2.1.2. Sites for temporal distribution studies 32 2.2. Coring techniques 38 2.3. Laboratory methods 38 2.3.1. Sediment analysis 38 2.3.2. Dating techniques 38 2.4. A method for the extraction of carbonaceous 39 particles from lake sediment 2.4.1. Laboratory procedure 40 2.4.2. Density separations 41 2.4.3. Filtration 42 2.4.4. Counting 42 2.4.5. Repeatability 43 2.4.6. Recovery rate 44 2.4.7. Detection limit 45 2.4.8. Application to a sediment core 45 2.4.9. Discussion 47 2.5. An extraction technique for inorganic ash 47 spheres from lake sediments 2.5.1. Organic material 49 2.5.2. Biogenic silica 49 2.5.3. Carbonates 50 2.5.4. Mineral silica 50 2.5.5. Magnetic separation 50 2.5.6. Density separations 52 2.5.7. Laboratory procedure 52 2.5.8. Counting 53 4 2.5.9. Repeatability 54 2.5.10. Recovery rate 54 2.5.11. Detection limit 55 2.5.12. Application to a sediment core 55 2.6. Reference material 57 9 7 U » 1 • Energy Dispersive Spectroscopy (EDS) 57 2.7.1. Sample preparation 57 2.7.2. EDS of carbonaceous particles 58 2.8. Computer software 58 2.8.1. Manipulation of EDS generated data 58 2.8.2. Statistical techniques 59 Chapter Three Carbonaceous particle characterisation. 60 3.1. Introduction 60 3.2. Previous attempts at fuel type separations 61 3.2.1. External morphology 61 3.2.2. Internal structure using thin sectioning 61 3.2.3. Chemical parameters 62 3.3. Principles of Energy Dispersive Spectroscopy 63 (EDS) 3.4. Power station reference material 65 3.5. EDS of reference material 69 3.5.1. Element selection 69 3.5.2. Automated data acquisition 69 3.5.3. X-ray corrections 70 3.5.4. Setting the wave-form thresholds 72 3.5.5. Data output 74 3.5.6. Negative values in chemical data 78 3.6. The reference data-set 78 3.6.1. Removal of outliers using MIDAS 78 3.6.2. Basic statistics of the reference data-set 81 3.7. Preliminary data analysis of EDS data 93 3.7.1. MIDAS analysis using data from Lxmbridge, 93 Pembroke and Gweedore power stations 3.7.2. Multivariate analysis using data from Ironbridge 100 and Pembroke power stations 3.8. Multivariate analysis of the full reference 105 data-set 3.8.1. Principal components analysis 106 3.8.2. Discriminant analysis on die reference data-set 113 3.8.3. Probabilities of allocation 118 3.8.4. Derivation of a coal/oil discriminant function 121 3.9. Extensions to the characterisation technique 125 3.9.1. Power station allocation 125 3.9.2. Extension to other fuel types 127 Chapter Four Temporal distribution of fly-ash particles in 128 lake sediments. 4.1. Introduction 128 5 4.2. Temporal trends in carbonaceous particle 131 profiles in lake sediments 4.2.1. Scotland 131 4.2.2. Wales 148 4.2.3. Ireland 154 4.2.4. England 161 4.2.5. Sites in Norway and France 164 4.3. Characterisation of carbonaceous particles 170 extracted from lake sediments 4.3.1. Extending particle characterisation to 170 ’fossil’ material 4.3.2. Application of particle characterisation to 174 a sediment core 4.4. Trends in inorganic ash sphere profiles 179 4.5. Discussion 183 4.5.1. Trends in particle deposition 1800 - 1980 183 4.5.2. Causes of a decrease in particle deposition 185 4.5.3. Reasons for the delay in sediment response 187 to the decrease in atmospheric particle deposition 4.5.4. Dating 189 4.5.5. Particle allocations through time 197 Chapter Five Spatial distribution of fly-ash particles in 198 lake sediments 5.1. Introduction 198 5.2. The spatial distribution of fly-ash particles 199 in Scottish surface sediments 5.2.1. Carbonaceous particles 199 5.2.2. Inorganic ash spheres 210 5.3. The spatial distribution of carbonaceous 214 particles in Scottish surface sediments according to fuel-type. 5.3.1. Characterised carbonaceous particles and the 221 IA:CP ratio 5.4. The relationship between fly-ash particle 223 concentrations and sulphur deposition 5.4.1. The sulphur deposition data 224 5.4.2. Particle concentrations and modelled sulphur 225 deposition 5.4.3. Particle concentrations and measured sulphur 236 deposition 5.4.4. Logarithmic transformations of the data 239 5.4.5. Particle fluxes and sulphur deposition 241 5.5. The spatial distribution of carbonaceous 245 particles on a European scale 5.6. Discussion 246 5.6.1. Concentrations and fluxes 246 5.6.2. Characterisation 247 5.6.3. Fly-ash particles and sulphur deposition 248 6 Chapter Six Conclusions 250 6.1.