Soils as a Key Component of the Critical Zone 3 Soils and Water Circulation

This book invites the reader to look differently at two seemingly mundane resources: soil and water. Water possesses extraordinary properties which form the foundations of life itself. Without water, there would be no life, and without soils, no terrestrial life. The interaction between soils and water is therefore fundamental to the habitability of Earth’s land surface.

Through in-depth analyses and experimentation, Soils as a Key Component of the Critical Zone 3 explores the circulation of water in soils. Through its properties, soil directs the path of water, leading it to wet soils or not, be absorbed by plants, infiltrate or runoff, concentrate in certain areas or flood. The potentially catastrophic consequences of such floods are often due to the absence or insufficiency of prevention measures.

This book thus shows the ways in which the relationship between water, life and soils is much more than a simple series of interactions or phenomena at interfaces and in fact constitutes a system with definite properties.

Guilhem Bourrié, a member of the Académie d'Agriculture de France, is a pedologist and geochemist.

Foreword xi
André Mariotti

Introduction xv
Guilhem Bourrié

Chapter 1. Physico-chemistry of the Soil–Water System 1
Guilhem Bourrié

1.1. The “abnormal” properties of water 1

1.1.1. The thermodynamic properties of pure water 3

1.1.2. The stability field of water according to the pH and pe 3

1.2. Properties of the water molecule 6

1.2.1. Geometry of the isolated water molecule 6

1.2.2. Water molecular orbitals 7

1.2.3. The first greenhouse gas: water 9

1.3. Pure liquid water 10

1.3.1. Dispersion forces 10

1.3.2. Hydrogen bonds 11

1.3.3. Associations of water molecules 11

1.3.4. The contribution of the density functional theory 12

1.3.5. A new vision for liquid water 12

1.4. Solutions properties 13

1.4.1. Goldschmidt’s ionic potential 13

1.4.2. The pseudoconcept of base cation 15

1.4.3 Jolivet’s model of partial charges 16

1.4.4. Application of the partial charge model to cations forms in water 21

1.4.5. The hydrophobic interaction and the biological role of water 23

1.4.6. The osmotic potential 23

1.4.7. The Gibbs–Duhem equation 24

1.4.8. The activity of dissolved salts 25

1.4.9. Activity coefficients 26

1.5. Calculation of activity coefficients 28

1.5.1. The Debye–Hückel theories 28

1.5.2. Pitzer’s model 30

1.5.3. The specific interactions theory 31

1.5.4. Practical implementation of models of calculation of activity coefficients 31

1.5.5. Application examples of activity calculations 33

1.5.6. Another approach: the lattice model 39

1.6. The matric potential 41

1.7. Osmotic potential and matric potential 44

1.8. Interaction with solid surfaces 44

1.9. Soil and microenvironment heterogeneity 46

1.10. Appendix: conditions for water stability 46

1.10.1. Water stability in acidic medium 46

1.10.2. Acidobasic neutrality 46

1.10.3. Water stability according to redox conditions 47

1.10.4. Water redox neutrality 48

1.11. Bibliography 49

Chapter 2. Soil Wettability 53
Philippe Beltrame

2.1. Introduction 53

2.2. Substrate wettability 54

2.2.1. Contact angle 54

2.2.2. Surface tension 55

2.2.3. Laplace pressure 56

2.2.4. Young–Dupré equation 57

2.2.5. Spreading parameter 58

2.3. Diffuse interface 59

2.3.1. Disjoining pressure 59

2.3.2. Pseudopartial wetting 61

2.4. Wetting dynamics 65

2.4.1. Paradox of the triple line 65

2.4.2. Contact angle hysteresis 66

2.4.3. Front instability 66

2.5. Capillarity 68

2.5.1. Capillary length 68

2.5.2. Capillary height and Jurin’s law 70

2.5.3. Capillary pressure 73

2.5.4. Darcy–Richards’ equation 75

2.6. Soil wettability: beyond capillarity 76

2.6.1. Hydrophobic soils 76

2.6.2. Wettability of a porous medium 79

2.6.3. Preferential flow genesis in micropores 80

2.7. Conclusion 81

2.8. Bibliography 82

Chapter 3. Water Uptake by Plants 85
Claude Doussan, Loïc Pagès

3.1. Introduction 85

3.1.1. A system with two main actors subjected to climate 85

3.1.2. Water flow from the soil up to the root collar of the plant is subjected to physical laws 86

3.1.3. Analysis of processes and their synthesis using simulation models 86

3.2. The cohesion-tension theory 86

3.3. Soil roles 87

3.3.1. Water storage and retention in soil 87

3.3.2. Water transport in the soil: notions of water potential and hydraulic conductivity 90

3.3.3. Water transfer from the soil to the root 92

3.4. Roles of roots 94

3.4.1. Development of an exchange and transport surface and the notion of root architecture 94

3.4.2. Root types 94

3.4.3. Developmental processes 95

3.4.4. Variation of root properties along the root 96

3.4.5. Other structures carried by roots 97

3.4.6. Strategies for root system development of various species 97

3.5. Soil/roots interactions 98

3.5.1. Soil modulates root development in various ways 98

3.5.2. Roots alter the surrounding soil: the rhizosphere 99

3.6. Soil/roots systems biophysical models 100

3.6.1. Description of water transport mechanisms in soil 100

3.6.2. Representation of root architecture dynamics 103

3.6.3. Transfer and hydraulic architecture representation in the root system: coupling with transfers in soil 104

3.6.4. Modulation of root hydraulic conductivity over time and processes related to aquaporins and embolism 109

3.6.5. Coupling of water transfer to and within the root system with transfers in soil 111

3.7. Conclusion 115

3.8. Appendix: demonstration of Equation [3.4] 115

3.9. Bibliography 116

Chapter 4. Preferential Flows 121
Yves Coquet, Ary Bruand

4.1. Water and solute transport 122

4.1.1. Water transport 122

4.1.2. Solute transport 125

4.2. Notion of “preferential flow” 128

4.3. Experimental study 129

4.3.1. Soil columns 129

4.3.2. Lysimeters 130

4.3.3. In situ tracing 131

4.3.4. Drained plots 132

4.4. Originating mechanisms 133

4.4.1. Role of macropores 135

4.4.2. Role of textural discontinuities 135

4.5. Models 138

4.5.1. The “mobile water/immobile water” (MIM) model 139

4.5.2. Dual permeability models 140

4.6. Bibliography 141

Chapter 5. Floods 145
Marcel Masson

5.1. When society programs disasters 145

5.2. From empiricism to modeling 147

5.2.1. The arduous evolution of flood forecasting 148

5.3. The naturalist alternative 150

5.3.1. The implicit rejection of rationality 153

5.4. The alluvial environment, a place for confrontations 154

5.4.1. The agricultural pressure 154

5.4.2. The pressure of urbanization 156

5.4.3. Protect and/or prevent? 157

5.4.4. Contradictions between the sovereign role of the State and logics of decentralization 161

5.5. Moving from a defensive–curative to a preventive–innovative approach 162

5.5.1. Alternative to urbanization in flood-prone areas 162

5.5.2. Creating synergy between issues: flood prevention and agrarian economy 163

5.6. Toward qualitative space management? 164

5.7. Bibliography 165

List of Authors 167

Index 169

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