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AUTHOR:
CRUICKSHANK, L.
TITLE:
Development of novel lanthanide based particle tracers for rapid monitoring of soil erosion.
YEAR:
2016
OpenAIR citation:
CRUICKSHANK, L. 2016. Development of novel lanthanide based particle tracers for rapid monitoring of soil erosion. Robert Gordon University, PhD thesis. Held on OpenAIR [online]. Available from: https://openair.rgu.ac.uk
This work was submitted to- and approved by Robert Gordon University in partial fulfilment of the following degree: Doctor of Philosophy, Faculty of Design and Technology, School of Engineering _______________________________________________________________________________________________
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Development of novel lanthanide based particle tracers for rapid monitoring of soil erosion
Laura Cruickshank
A thesis submitted in partial fulfilment of the requirements of The Robert Gordon University, Aberdeen for the degree of Doctor of Philosophy
January 2016 This research programme was carried out in collaboration with The James Hutton Institute
ii
Dedication
For my Mum and Dad, who taught me to always aim for the stars.
And for Chloe and Euan, I hope in some small way this helps teach you the same.
iii
Declaration
I hereby declare that no portion of the work referred to in this thesis has been submitted in support for an application for another degree or qualification of this or another university or other institute of learning. This is an original piece of work undertaken by myself. All results and work other than my own are clearly cited and acknowledged.
iv
Acknowledgements
I wish to express my sincere thanks to the following: Firstly I wish to express my immense gratitude to my supervisors, Simon Officer, Marc Stutter and Pat Pollard for all the support and advice given throughout the project. A special thank you to all the staff and students in the centre for research, energy and the environment for many useful discussions and much encouragement. In particular to Morgan Adams who helped to remind me that research can be fun! Thank you to the staff of the analytical chemistry labs, and engineering workshop, who were always there to give advice whenever needed. Also, to everyone at the James Hutton Institute whose help was invaluable, particularly Samia Richards for guiding me patiently through a variety of new techniques, and Evelyne DelBois who helped obtain some of the SEM images included in this thesis. Funded by the Institute for Innovation, Design and Sustainability (IDEAS) at the Robert Gordon University. Finally I would like to thank my friends and family, particularly Neil, Chloe and Euan for providing endless encouragement, patience and support. You can finally get mummy back now!
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Abstract Soil erosion is a global problem, affecting much of the world’s agricultural land. As the world’s population increases, the pressures placed upon the land resource to provide space for food production, leisure, housing and industrial facilities also increases. Thus it is vital that the land resource is as productive as possible. As soil erosion is the major cause of soil degradation globally, it is vital that methods for accurately monitoring the degree of erosion from a site, and the effectiveness of any remediation attempts are available. Reported here is the development of a novel soil erosion particle tracer, based upon a lanthanide chelate complex doped silica particle. The luminescent lanthanide chelate complexes were comprised of 2-thenoyltrifluoroacetone (TTA) and 2-pyridinol-1-oxide (2PO) coordinated with either trivalent europium or terbium ions. These complexes were then doped into silica sol-gel particles using a core shell technique. This method resulted in the synthesis of two luminescent soil tracers, targeted to two of the key eroded soil fractions; fine silt (63-250 μm) and clay (< 1.2 μm). The behaviour of the tracers was analysed within three different soils obtained from the Glensaugh research station. They retained their luminescence when mixed with soil, and could be detected at concentrations of 10 mg tracer / kg soil using a standard benchtop fluorescence spectrometer (Perkin Elmer LS55B). Scanning electron micrographs indicated that the tracer particles interacted with the soil particles, whilst soil sedimentation experiments demonstrated that the tracer particles had a similar sedimentation pattern to natural soil particles. Soil microbial respiration studies were performed for the tracers and showed that the tracers did not significantly impact the soil microbial population. Studies of the luminescence stability of the tracer in soil over time showed that the tracer could be detected in the soil for one season (approximately 3 months). A prototype rainfall simulator, designed to simulate the kinetic energy of vi
raindrops on the surface of the soil, was developed, and used during a series of rainfall simulation experiments. These simulations were performed at two different rainfall intensities (30 and 90 mm.h-1) and both of these conditions resulted in movement of the tracer particles within the plot. This movement was both horizontal, in overland flow over the plot surface, and vertical, through the plot. The pattern of tracer movement reflected that of the soil mass moved, and as such indicated that the tracers exhibited similar transport behaviour during the erosion simulations performed. These initial simulations demonstrated that the tracers can be detected at low concentrations within the soil using standard laboratory equipment, and that they move with the eroded soil particles during simulated soil erosion experiments. As such, these tracers are excellent candidates for further study in larger scale erosion events.
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Abbreviations AGA –
amino G acid monopotassium dye
ANOVA –
analysis of variance
ATR -
attenuated total reflection
BLD -
below limit of detection
DMSO –
dimethyl sulfoxide
D2 O –
deuterium
DOE -
design of experiments
DSC –
differential scanning colorimetry
EDXA –
energy dispersive x-ray analysis
FTIR –
Fourier Transform Infrared
HMP –
sodium hexametaphosphate solution
HOPO –
hydroxy-pyridinones
HP-Ge –
high purity – germanium
HTTA -
free 2-thenoyltrifluoroacteone
ICP-OES –
inductively coupled plasma – optical emission spectroscopy
ICP-MS –
inductively coupled plasma – mass spectrometry
IR -
Infra-red
LC-MS –
liquid chromatography- mass spectrometry
Ln3+ -
trivalent ion of the lanthanide series
viii
LOD –
limit of detection
MRI –
magnetic resonance imaging
NMR –
nuclear magnetic resonance
PMT –
photomultiplier tube
REE
-
rare earth element
REETM -
rare earth element tracer method
SAXS -
small angle x-ray scattering
SEM
scanning electron microscope
-
SEPA –
Scottish Environmental Protection Agency
TEOS –
tetraethylorthosilicate
TGA –
thermogravimetric analysis
TMOS –
tetramethoxysilane
TTA –
coordinated 2-thenoyltrifluoroacetone
2PO –
2-pyridinol-1-oxide
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Table of contents DEDICATION
III
DECLARATION
IV
ACKNOWLEDGEMENTS ABSTRACT
V VI
ABBREVIATIONS
VIII
LIST OF FIGURES
XIV
LIST OF TABLES
XXII
PUBLICATIONS
XXIV
CHAPTER 1 - GENERAL INTRODUCTION AND LITERATURE REVIEW 1.1 SOILS AND SOIL STRUCTURE 1.2 SOIL EROSION
1 2
3
1.2.1 Water erosion
11
1.2.2 Wind erosion
13
1.2.3 Tillage erosion
14
1.3 SUSPENDED PARTICULATE MATTER
15
1.4 METHODS OF MONITORING SOIL EROSION 1.4.1 Sediment fingerprinting
16
1.4.2 Radioisotopes as erosion tracers
17
1.4.3 Rare earth elements
19
1.4.4 Applied ions
20
1.4.5 Dyes
21
1.4.6 Physical tracers
22
1.4.7 Applied particle tracers
22
16
1.5 LANTHANIDES AND LANTHANIDE CHELATE COMPLEXES
24
1.6 SILICA SOL-GEL PARTICLES
31
1.7 RESEARCH AIMS AND THESIS OVERVIEW
36
1.5.1 Lanthanide photochemistry
1.5.2 Luminescent lanthanide complexes 1.6.1 Lanthanide complex doped sol-gels
CHAPTER 2 – SYNTHESIS AND CHARACTERISATION OF LANTHANIDE CHELATE COMPLEXES.
25 28 35
39
x
2.1 INTRODUCTION
2.1.1 The hydroxy-pyridinones 2.1.2 Quantum yield
40
40 41
2.1.3 Fluorescence lifetimes
42
2.1.4 Aim and objectives
43
2.2 MATERIALS AND METHODS
45
2.2.1 Chemicals and reagents 2.2.2 Synthesis of lanthanide chelate complexes
45
45
2.2.3 Determination of lowest triplet state
46
2.2.3 Infra-red analysis of chelate complexes
46
2.2.4 Nuclear magnetic resonance spectroscopy and Flow injection analysis.
48
2.2.5 Thermogravimetric analysis and Karl Fisher titrations
48
2.2.6 Fluorescence emission and excitation
49
2.2.7 Quantum yield and fluorescence lifetime measurement
49
2.3 RESULTS AND DISCUSSION
2.3.1 Triplet state determination 2.3.2 Infra-red analysis
50
50 52
2.3.3 Nuclear magnetic resonance
58
2.3.4 Flow injection analysis – mass spectrometry
61
2.3.5 Determination of coordinated water
63
2.3.6 Fluorescence spectroscopy
65
2.3.7 Lifetime determination
67
2.3.8 Quantum yield
69
2.4 CONCLUSIONS
73
3.1 INTRODUCTION
74
CHAPTER 3 – SYNTHESIS AND CHARACTERIZATION OF SILICA SOL-GEL PARTICLES 3.1.1 Sol-gel synthesis 3.1.2 Lanthanides doped sol-gels 3.1.3 Aim and objectives 3.2 SOL-GEL SYNTHESIS
3.2.1 Chemicals and reagents 3.2.2 Methods for particle synthesis 3.2.3 Methods for analysis of synthesised particles
3.3 RESULTS AND DISCUSSION
70 74
74 75
76
76 76 78
81
xi
3.3.1 Synthesis of silica sol-gel particles in the colloidal clay size range (
