Soils as a Key Component of the Critical Zone 5 Degradation and Rehabilitation

One third of the world's soils have already been degraded. The burden on the land continues to grow under the combined pressures of demography, urbanization, artificialization and mining, and there are increased demands on agricultural land: changing dietary preferences, land speculation, as well as new demands for agroenergy, fiber, green chemistry, and more. Resulting issues such as soil crusting, water and wind erosion, soil salinization and soil acidity therefore constitute a major threat.

The authors of this book present the main processes and factors of soil degradation, different ways to prevent it and methods of rehabilitation. The book also deals with the origin and processes of metallic and organic soil pollution as well as methods of phytoremediation and restoration. It is one of the few books to explore the issue of soil artificialization and urban soil management and to highlight how agricultural and urban waste can be used to amend and fertilize cultivated soils.

Christian Valentin is an agronomic engineer and soils specialist at l’Institut de Recherche pour le Développement, France. With 40 years of soil erosion and conservation research experience behind him, he teaches at Sorbonne University, France, and Hanoi, Vietnam, and is Deputy Director of l'Institut d'Ecologie et des Sciences de l'Environnement de Paris. He is the coordinator of the Soils Group of the French Academy of Agriculture.

Foreword xi

Chapter 1. The State and Future of Soils 1
Christian VALENTIN

1.1. Soils as a key component of the critical zone 1

1.1.1. Definitions 1

1.1.2. Soil functions and services 1

1.1.3. Soil and land degradation, desertification 3

1.2. The difficult assessment of the state and kinetics of soil degradation or enhancement 3

1.2.1. Global assessment 4

1.2.2. Forms of degradation 5

1.2.3. Main factors of soil degradation 8

1.2.4. What’s the trend: degradation spiral or U-curve? 9

1.2.5. The necessity for monitoring mechanisms 12

1.3. Conservation, restoration, rehabilitation and compensation 12

1.3.1. Definitions 12

1.3.2. Implementation 13

1.3.3. Concept of neutrality in terms of land degradation 14

1.4. Conclusions 15

1.5. References 16

Chapter 2. Soil Surface Crusting of Soil and Water Harvesting 21
Christian VALENTIN

2.1. Surface conditions and surface crusts 21

2.2. Crust types and formation processes 23

2.2.1. Structural crusts 23

2.2.2. Gravel crusts 24

2.2.3. Erosion crusts 24

2.2.4. Depositional crusts 25

2.2.5. Saline crusts and efflorescence 25

2.2.6. Biological soil crusts (or Biocrusts) 26

2.3. Crusting factors and principles for improving aggregate stability 26

2.3.1. Soils 26

2.3.2. Rain 26

2.3.3. Slope 27

2.3.4. Cover 27

2.3.5. Agricultural practices 28

2.4. Consequences of surface crusting 29

2.4.1. Hydrological: Hortonian flow 29

2.4.2. Ecological: example of the tiger bush 30

2.4.3. Agronomic: water harvesting 32

2.5. Conclusions 33

2.6. References 34

Chapter 3. Erosion and Principles of Soil Conservation 39
Christian VALENTIN and Jean Louis RAJOT

3.1. Definitions 39

3.2. The importance of erosion 40

3.2.1. On a global scale 40

3.2.2. Effects of erosion 41

3.3. Processes and factors 45

3.3.1. Splash detachment 45

3.3.2. Sheet erosion (also called inter-rill erosion) 47

3.3.3. Linear erosion 52

3.3.4. Mass movements 54

3.3.5. Tillage erosion 55

3.3.6. Wind erosion 56

3.4. Erosion: a question of scale 60

3.4.1. Space scales 60

3.4.2. Time scales 61

3.4.3. Space scales 62

3.4.4. Particulate and soluble transport 63

3.4.5. Aeolian dust 63

3.5. Modeling 64

3.5.1. Statistical approaches 65

3.5.2. Physically based models 65

3.5.3. Hybrid models 66

3.6. Principles of soil conservation 66

3.6.1. Field level: limiting detachment 66

3.6.2. Catchment scale: slowing runoff and promoting deposition 69

3.7. Population density, economic contexts and public policies 70

3.8. Conclusions 72

3.9. References 73

Chapter 4. Soil Acidity and Acidification 83
Étienne DAMBRINE

4.1. Acidity 83

4.2. Definitions of acidification and its evolution 85

4.3. Illustration: long-term theoretical evolution of the acidity of a limestone loess 87

4.4. Acidifying processes 88

4.5. Involvement of large biogeochemical cycles in soil acidification 89

4.5.1. Nitrogen cycle 89

4.5.2. Carbon cycle 89

4.5.3. Absorption of cations/anions by plants 89

4.5.4. Acid or alkaline deposits 90

4.5.5. Other cycles: P, S, Fe, Mn 90

4.6. Neutralization of acidification 90

4.7. Biogeography of acidity 91

4.8. Physical and biological consequences of soil acidity 92

4.9. References 93

Chapter 5. Soil Salinization and Management of Salty Soils 97
Jean-Pierre MONTOROI

5.1. Introduction 97

5.2. Natural salty environments 97

5.2.1. Salts, dissolved particulate entities 97

5.2.2. Typical landscapes 98

5.2.3. Continuous movement of salts 99

5.2.4. Ecosystemic services 100

5.3. Characterization and functioning of salty soils 102

5.3.1. Diagnosis of the degree of salinization 102

5.3.2. Intrinsic physical–chemical processes 102

5.3.3. Chemical concentration and evolution pathways of soil water 105

5.3.4. Mineralogy of saline efflorescences 107

5.4. Typology of salty soils 108

5.4.1. Soil characteristics 108

5.4.2. Vertical distribution of salinity 109

5.4.3. Spatial distribution of salinity 110

5.4.4. Classification of salty soils 110

5.4.5. Worldwide distribution of salty soils 112

5.5. Secondary soil salinization 112

5.5.1. Anthropogenic input of salts in soils 112

5.5.2. Salinization of irrigated systems 113

5.5.3. Control of salts in irrigation 114

5.5.4. Use of non-conventional waters 115

5.6. Agricultural development of sodic soils 116

5.6.1. Historical context 116

5.6.2. Effects of soil salt water on plants 116

5.6.3. Agronomic solutions 117

5.6.4. Macroeconomic solutions 119

5.6.5. Social and political solutions 120

5.7. Conclusions 120

5.8. References 122

Chapter 6. Metal Pollution 127
Denis BAIZE

6.1. General information 127

6.1.1. Definitions: trace elements 127

6.1.2. Risks and hazards: exposure and transfer routes 129

6.1.3. Different forms and locations of trace elements in soils 132

6.1.4. Measurement and estimation methods available 133

6.1.5. How should the pollution level of soil be assessed? 135

6.2. Famous polluted sites (France) 141

6.2.1. Metaleurop at Noyelles-Godault 142

6.2.2. Mortagne-du-Nord 144

6.2.3. Pierrelaye plain (polymetallic pollution) 145

6.3. Locally polluted sites and diffuse contamination 147

6.3.1. Pole treatment site polluted by copper in podzol context 147

6.3.2. Soil contamination by sewage sludge 147

6.3.3. Copper contamination in vineyard soils 153

6.3.4. Copper and zinc soil contamination from repeated spreading of pig manure 155

6.3.5. Atmospheric deposition of lead since antiquity 156

6.3.6. Metal nanoparticules 157

6.4. Impacts of metal pollution 158

6.4.1. Bio- and phytoavailability – absorption routes 158

6.4.2. Mobility 158

6.4.3. Mobility and bioavailability estimation 159

6.4.4. The importance of soil properties for speciation, bioavailability and mobility 159

6.5. What should be done about metal polluted soils? 160

6.5.1. Strategies without treatment 161

6.5.2. Stripping polluted horizons 161

6.5.3. In situ immobilization and phytoremediation 161

6.5.4. An example: the Maatheide-Lommel site (Belgium) 163

6.6. References 166

Chapter 7. Organic Pollution and Soil Rehabilitation 169
Corinne LEYVAL, Aurélie CÉBRON and Pierre FAURE

7.1. Organic pollution: its origins and diversity 169

7.2. Origin and distribution of PAHs in soils 170

7.3. Characteristics, properties and toxicity of PAHs 171

7.4. Fate and impact of organic pollution in soils: tools and approaches 173

7.4.1. Sorption of PAHs in soils 173

7.4.2. Bioavailable form and ageing of PAH contamination in soils 175

7.4.3. Biodegradation and the microorganisms involved 176

7.5. Fate of PAHs in the plant rhizosphere 177

7.6. Remediation techniques: limitations and constraints 179

7.7. From remediation to restoration 181

7.8. Conclusions 182

7.9. References 183

Chapter 8. Urban Soils: Artificialization and Management 189
Laure VIDAL-BEAUDET and Jean-Pierre ROSSIGNOL

8.1. Introduction 189

8.2. Soil urbanization 190

8.2.1. History and origin of urban soils 190

8.2.2. Artificialization and sealing 192

8.3. Soil characteristics in urban areas 193

8.3.1. Typology of urban soils 194

8.3.2. The properties of artificialized urban soils 196

8.4. Urban soil classification and mapping 197

8.4.1. Classification 197

8.4.2. Mapping 199

8.5. Fertile soils for vegetated areas 202

8.5.1. Reconstituted soils 203

8.5.2. The particular case of aggregate structural soil 204

8.5.3. Soils built from the “waste” from cities 205

8.6. Conclusions 206

8.6.1. The “brown belt” 206

8.6.2. Urban soil value and protection 207

8.7. References 208

Chapter 9. Recycling Organic Waste Products in a Tropical Context 211
Frédéric FEDER

9.1. Definition, typology and main characteristics of organic waste products 211

9.1.1. Definition of organic waste products and associated issues 211

9.1.2. Typology of organic waste products 212

9.2. Analytical characterizations of organic waste products 215

9.2.1. Chemical elements of agronomic interest (C, N, P, K) 216

9.2.2. Specific analyses of organic properties 216

9.2.3. Organic and metallic trace contaminants 217

9.3. Agricultural interests and environmental risks 218

9.3.1. Fertilizing aspects of organic waste products 218

9.3.2. Amending aspects of organic waste products 220

9.3.3. Metallic, organic and biological contaminants 223

9.3.4. Other environmental impacts 224

9.4. Examples of recycling organic waste products in tropical contexts 226

9.4.1. In weakly intensified systems 226

9.4.2. In intensive systems 227

9.5. References 231

List of Authors 235

Index 237

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