Environmental Isotopes in the Hydrological Cycle
Principles and Applications
VOLUME IV: GROUNDWATER
SATURATED AND UNSATURATED ZONE
by Mebus Geyh Niedersächsisches Landesamt für Bodenforschung Hannover
Contributing Authors
F.D´Amore, G.Darling, T.Paces, Z.Pang, J.Šilar
Preface
CONTENTS
1 HYDROGEOLOGY AND AQUIFER CHARACTERISTICS 1
1.1 Definitions 1
1.2 Occurrence of groundwater in rocks 1
1.3 Geohydraulic parameters 2
1.3.1 Porosity 2
1.3.2 Storage, storage coefficient 4
1.3.3 Permeability and hydraulic conductivity 5
1.3.4 Flow nets 5
1.4 Hydrogeology 8
1.4.1 Hydrogeological properties of rocks 8
1.4.1.1 Igneous rocks 8
1.4.1.2 Metamorphic rocks 9
1.4.1.3 Consolidated sedimentary rocks 9
1.4.1.4 Unconsolidated sediments 10
1.4.2 Hydrogeological structures - groundwater regimes 10
1.4.3 Crystalline regions 11
1.4.3.1 Volcanic rocks 11
1.4.3.2 Folded sequences of sedimentary rocks 11
1.4.3.3 Karstified rocks 12
1.4.3.4 Platform sediments 12
1.4.3.5 Alluvial plains, fans, river deltas, glaciofluvial, sediments 13 2 TRACERS AND TRANSPORT 15
2.1 Types of tracers 15
2.2 Types of tracer experiments 16
2.3 Isotopes in groundwater 17
2.3.1 Stable isotopes 17
2.3.2 Radioactive isotopes 18
2.3.3 Chemicals 20
2.3.4 Colloids 21
2.3.5 Noble gases 22 3 GEOHYDRAULIC ASPECTS 25
3.1 Steady-state groundwater flow 26
3.1.1 Darcy velocity and tracer velocity 26
3.1.2 Principle groundwater flow models 27 3.1.3 Considerations about modelling 32
3.1.4 Groundwater discharge 32
3.1.4.1 Springs 33
3.1.4.2 Production wells 34
3.1.4.3 Well construction and sampling of water from wells 35
3.2 Non-steady state groundwater flow 36
3.2.1 Palaeoclimatic causes 36
3.2.2 Anthropogenic causes 37 4 WATER-ROCK INTERACTIONS 41
4.1 Anion exclusion-adsorption: physical absorption 42
4.2 Chemical absorption 42
4.3 Exchange of ions 43
4.4 Chemical interaction between solutes 43
4.4.1 Carbonate-CO2 system 43
4.4.2 Reactions with organic matter 44
4.4.3 Fate of dissolved sulphur compounds 45
4.4.4 On the isotopic composition of strontium 48 5 APPLICATIONS TO LOW-TEMPERATURE SYSTEMS 49
5.1 Unsaturated zone 49
5.1.1 Principal soil parameters of the unsaturated zone 49
5.1.2 Geohydraulic aspects 50
5.1.2.1 Steady-state flow 50
5.1.2.2 Movement of solutes 51
5.1.2.2.1 Convection and advection 51
5.1.2.2.2 Dispersion 51
5.1.2.2.3 By-pass flow (dual flow) 53
5.1.3 Solute transport 53
5.1.4 Application 54
5.1.4.1 Recharge rate determination by mass balance 54
5.1.4.2 Recharge rate determination by tracer peak displacement 55
5.1.4.3 Evaporation rate 59
5.1.4.4 Water loss by plant extraction 65
5.2 Saturated zone 65
5.2.1 Origin of groundwater 65
5.2.1.1 Oxygen (18O/16O) and hydrogen (2H/1H) 65
5.2.1.2 Carbon (13C/`12C) 72
5.2.1.3 Nitrogen (15N/14N) 75
5.2.1.4 Sulphur (34S/32S) 79
5.2.1.5 Chlorine (37Cl/35Cl) 89
5.2.1.6 Boron (10B/11B) 89
5.2.1.7 Strontium (87Sr/86Sr) 93
5.2.2 Groundwater dating 95
5.2.2.1 Tritium 96
5.2.2.2 3H/3He and 3He methods 99
5.2.2.3 Radiocarbon 100
5.2.2.4 Silicon-32 107
5.2.2.5 Chlorine-36 107
5.2.2.6 Argon-39 110
5.2.2.7 Krypton-81 111
5.2.2.8 Krypton-85 111
5.2.2.9 Iodine-129 113
5.2.2.10 Uranium/Helium and K/Ar methods 113
5.2.2.11 Radium/radon dating method 114
5.2.2.12 234U/238U dating method 115 6 APPLICATIONS TO HIGH-TEMPERATURE SYSTEMS 119
6.1 Natural processes 121
6.1.1 Water-rock interaction at high temperature 123
6.1.2 Isotopic geothermometry 125
6.1.3 Tracing the origin and history of fluids 130
6.1.4 Mixing with geothermal fluids 130
6.2 Anthropogenic processes 134
6.2.1 Steam loss 134
6.2.2 Underground liquid-vapour separation processes 138
6.2.3 Isotope techniques in re-injection studies 141
6.2.4 Variability of the isotopic composition in geothermal fluid 143 7 PLANNING AND PERFORMANCE OF MULTIPLE ISOTOPE STUDIES 151
REFERENCES 155 LITERATURE 175 IAEA PUBLICATIONS 177 CONSTANTS 180 GLOSSARY 181 SYMBOLS 189 SUBJECT INDEX 191
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