Handbook of soil analysis

Water Content and Loss on Ignition 1.1 Introduction Schematically, a soil is made up of a solid, mineral and organic phase, a liquid phase and a gas phase.. 1.2.3 Sample It is essentia

Jacques Gautheyrou

Handbook of Soil Analysis

Mineralogical, Organic and Inorganic Methods

with 183 Figures and 84 Tables

Updated English version, corrected by Daphne Goodfellow The original French book

"L'analyse du sol, minéralogique et minérale" by Marc Pansu and Jacques Gautheyrou, was published in 2003 by Springer-Verlag , Berlin Heidelberg New York

Library of Congress Control Number: 2005938390

ISBN-10 3-540-31210-2 Springer Berlin Heidelberg New York

ISBN-13 978-3-540-31210-9 Springer Berlin Heidelberg New York

This work is subject to copyright All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks Duplication

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Jacques Gautheyrou

F OREWORD

This new book by Marc Pansu and Jacques Gautheyrou provides a synopsis of the analytical procedures for the physicochemical analysis of soils It is written to conform to analytical standards and quality control

It focuses on mineralogical, organic and inorganic analyses, but also describes physical methods when these are a precondition for analysis It will help a range of different users to choose the most appropriate method for the type of material and the particular problems they have to face The compiled work is the product of the experience gained by the authors in the laboratories of the Institute of Research for Development (IRD) in France and in tropical countries, and includes an extensive review of the literature The reference section at the end of each chapter lists source data from pioneer studies right up to current works, such as, proposals for structural models of humic molecules, and itself represents a valuable source of information

IRD soil scientists collected data on Mediterranean and tropical soils in the field from West and North Africa, Madagascar, Latin America, and South East Asia Soil materials from these regions are often different from those found in temperate zones As their analysis brought new problems to light, it was essential to develop powerful and specific physicochemical methods Physicists, chemists and biologists joined forces with IRD soil scientists to contribute knowledge from their own disciplines thereby widening its scope considerably This work is the fruit

of these experiments as applied to complex systems, involving soils and the environment

The methodological range is particularly wide and each chapter presents both simple analyses and analyses that may require sophisticated equipment, as well as specific skills It is aimed both at teams involved in practical field work and at researchers involved in fundamental and applied research It describes the principles, the physical and chemical basis of each method, the corresponding analytical procedures, and the constraints and limits of each The descriptions are practical, easy to understand and implement Summary tables enable a rapid overview of

Principle

fluorescence, EDX or WDX microprobe, neutron activation analysis), diffractograms (XRD, electron microdiffraction), thermograms (DTA, DTG, TGA), chromatograms (GPC, HPLC, ionic chromatography, exclusion chromatography), electrophoregrams, ion exchange methods, electrochemistry, biology, different physical separation techniques, selective dissolutions, and imagery

the data Complex techniques are explained under the heading

and concrete examples of methods include: spectra (near and far IR,

The book will be valuable not only for researchers, engineers, technicians and students in soil science, but also for agronomists and ecologists and

geology, climatology, civil engineering and industries associated with soil It is a basic work whose goal is to contribute to the scientific analysis of the environment The methodologies it describes apply to a wide range of bioclimatic zones: temperate, arid, subtropical and tropical

As with the previous books by the same authors (Pansu, Gautheyrou and

represents a reference work for our laboratories We are confident its originality and ease of use will ensure its success

2 3

CNRS, Centre National de la Recherche Scientifique (France)

Loyer, 1998, Masson, Paris, Milan, Barcelona; Pansu, Gautheyrou and Loyer, 2001, Balkema, Lisse, Abington, Exton, Tokyo), this new book others in related disciplines, such as, analytical physical chemistry,

Christian Feller, Director of Research at IRD

Pierre Bottner, Director of Research at CNRS

PART 1 - MINERALOGICAL ANALYSIS

CHAPTER 1 Water Content and Loss on Ignition

1.1 Introduction 3

1.2 Water Content at 105°C (H 2 O−) 6

1.2.1 Principle 6

1.2.2 Materials 6

1.2.3 Sample 6

1.2.4 Procedure 7

1.2.5 Remarks 7

1.3 Loss on Ignition at 1,000°C (H 2 O + ) 8

1.3.1 Introduction 8

1.3.2 Principle 11

1.3.3 Equipment 11

1.3.4 Procedure 11

1.3.5 Calculations 12

1.3.6 Remarks 12

Bibliography 12

CHAPTER 2 Particle Size Analysis 2.1 Introduction 15

2.1.1 Particle Size in Soil Science 15

2.1.2 Principle 17

2.1.3 Law of Sedimentation 18

2.1.4 Conditions for Application of Stokes Law 24

2.2 Standard Methods 26

2.2.1 Pretreatment of the Sample 26

2.2.2 Particle Suspension and Dispersion 31

2.2.3 Pipette Method after Robinson-Köhn or Andreasen 35

2.2.4 Density Method with Variable Depth 42

2.2.5 Density Method with Constant Depth 47

2.2.6 Particle Size Analysis of Sands Only 48

2.3 Automated Equipment 50

2.3.1 Introduction 50

2.3.2 Method Using Sedimentation by Simple Gravity 51

2.3.3 Methods Using Accelerated Sedimentation 53

2.3.4 Methods Using Laser Scattering and Diffraction 54

2.3.5 Methods Using Optical and Electric Properties 55

2.3.6 Methods Allowing Direct Observations of the Particles 55

2.3.7 Methods Using Conductivity 56

References 56

Bibliography 58

Generality 58

CHAPTER 3 Fractionation of the Colloidal Systems

3.1 Introduction 65

3.2 Fractionation by Continuous Centrifugation 66

3.2.1 Principle 66

3.2.2 Theory 69

3.2.4 Procedure 75

References 81

Bibliography 81

CHAPTER 4 Mineralogical Characterisations by X-Ray Diffractometry 4.1 Introduction 83

4.1.1 X-Ray Diffraction and Mineralogy 83

4.1.2 Principle 86

4.1.3 XRD Instrumentation 87

4.2.1 Overview of Preparation of the Samples 90

4.2.2 Preparation for Powder Diagrams 90

4.2.3 Preparation for Oriented Diagrams 94

4.2.4 Pretreatment of Clays 99

4.2.5 Qualitative Diffractometry 113

4.3.1 Interest 118

4.3.2 Quantitative Mineralogical Analysis by XRD 118

4.3.3 Multi-Instrumental Quantitative Mineralogical Analysis 124

References 126

Bibliography 127

General 127

Saturation of Clays by Cations 129

Saturation, Solvation, Intercalation Complex, Dissolution 129

Preparation of Iron Oxides 130

Quantitative XRD 130

CHAPTER 5 Mineralogical Analysis by Infra-Red Spectrometry 5.1 Introduction 133

5.1.1 Principle 133

5.1.2 IR Instrumentation 135

5.2.1 Equipment and Products 138

5.2.2 Preparation of the Samples 139

5.2.4 Quantitative Analysis 152

Pre-treatment 58

Pipette Method 61

Hydrometer Method 62

Instrumental Methods 62

3.3 Pretreatment of the Extracted Phases 79

4.2 Qualitative Diffractometry 90

4.3 Quantitative Mineralogical Analysis 118

5.2 IR Spectrometry in Mineralogy 138

5.2.3 Brief Guide to Interpretation of the Spectra 146

Preparation of Oriented Aggregates on Porous Ceramic Plate 128

3.2.3 Equipment and reagents 73

CHAPTER 6 Mineralogical Separation by Selective Dissolution

6.1 Introduction 167

6.1.1 Crystallinity of Clay Minerals 167

6.1.2 Instrumental and Chemical Methods 169

6.1.3 Selective Dissolution Methods 172

6.1.4 Reagents and Synthetic Standards 174

6.2 Main Selective Dissolution Methods 180

6.2.1 Acid Oxalate Method Under Darkness (AOD) 180

6.2.2 Dithionite-Citrate-Bicarbonate Method (DCB) 187

6.2.4 Pyrophosphate Method 196

6.3 Other Methods, Improvements and Choices 206

6.3.1 Differential Sequential Methods 206

6.3.2 Selective Methods for Amorphous Products 210

References 215

CHAPTER 7 Thermal Analysis 7.1 Introduction 221

7.1.1 Definition 221

7.1.2 Interest 223

7.2 Classical Methods 226

7.2.1 Thermogravimetric Analysis 226

7.2.2 Differential Thermal Analysis and Differential Scanning Calorimetry 235 7.3 Multi-component Apparatuses for Thermal Analysis 246

7.3.1 Concepts 246

7.3.2 Coupling Thermal Analysis and Evolved Gas Analysis 247

References 249

Chronobibliography 250

CHAPTER 8 Microscopic Analysis 8.1 Introduction 253

8.2 Preparation of the Samples 254

8.2.1 Interest 254

8.2.2 Coating and Impregnation, Thin Sections 255

8.2.3 Grids and Replicas for Transmission Electron Microscopy 261

8.2.4 Mounting the Samples for Scanning Electron Microscopy 263

8.2.5 Surface Treatment (Shadowing, Flash-carbon, Metallization) 265

5.3.2 Coupling Thermal Measurements and FTIR Spectrometry of Volatile Products 158

5.3.3 Infrared Microscopy 159

References 161

Chronobibliography 162

5.3 Other IR Techniques 156

5.3.1 Near-infrared Spectrometry (NIRS) 156

5.3.4 Raman Scattering Spectroscopy 159

6.2.3 EDTA Method 192

6.2.5 Extraction in Strongly Alkaline Mediums 201

6.3.3 Brief Overview to the Use of the Differential Methods 214

CHAPTER 9 Physical Fractionation of Organic Matter

9.1 Principle and Limitations 289

9.1.1 Forms of Organic Matter in Soil 289

9.1.2 Principle 289

9.1.3 Difficulties 291

9.2 Methods 293

9.2.1 Classification 293

9.2.2 Extraction of Plant Roots 293

9.2.3 Dispersion of the Particles 296

9.2.4 Separation by Density .309

9.2.5 Particle Size Fractionations 314

9.2.6 Precision of the Fractionation Methods 320

9.3 Conclusion and Outlook 321

References 322

CHAPTER 10 Organic and Total C, N (H, O, S) Analysis 10.1 Introduction 327

10.1.1 Soil Organic Matter 327

10.1.2 Sampling, Preparation of the Samples, Analytical Significance 330

10.2 Wet Methods 333

10.2.1 Total Carbon: General Information 333

340

10.2.7 Kjeldahl N, Titration by Spectrocolorimetry 349

10.2.9 Mechanization and Automation of the Kjeldahl Method 353

10.2.10 Modified Procedures for NO 3 , NO 2 and Fixed N 354

10.3 Dry Methods 355

10.3.1 Total Carbon by Simple Volatilization 355

10.3.2 Simultaneous Instrumental Analysis by Dry Combustion: CHN(OS)356 10.3.3 CHNOS by Thermal Analysis 362

PART 2 - ORGANIC ANALYSIS 8.3 Microscope Studies 267

8.3.1 Optical Microscopy 267

8.3.2 Electron Microscopy, General Information 270

8.3.3 Transmission Electron Microscopy, Micro-diffraction 271

8.3.4 Scanning Electron Microscopy 279

8.3.5 Ultimate Micro-analysis by X-Ray Spectrometry 282

References 283

Chronobibliography 284

10.2.2 Organic Carbon by Wet Oxidation at the Temperature of Reaction .335

10.2.3 Organic Carbon by Wet Oxidation at Controlled Temperature 10.2.4 Organic Carbon by Wet Oxidation and Spectrocolorimetry 342

10.2.5 Total Nitrogen by Wet Method: Introduction .342

10.2.6 Total Nitrogen by Kjeldahl Method and Titrimetry 344

10.2.8 Kjeldahl N, Titration by Selective Electrode 351

11.2.3 Precision and Correspondence of the Extraction Methods 383

11.3 Further Alternatives and Complements Methods 392

11.3.1 Alternative Method of Extraction 392

11.3.2 Fractionation of the Humin Residue 392

References 395

CHAPTER 12 Characterization of Humic Compounds 12.1 Introduction 399

12.1.1 Mechanisms of Formation 399

12.1.2 Molecular Structure 400

12.2 Classical Techniques 401

12.2.1 Fractionation of Humic Compounds 401

12.2.2 Titration of the Main Functional Groups 408

12.2.3 UV–Visible Spectrometry 410

12.2.4 Infra-Red Spectrography 413

12.3 Complementary Techniques 415

12.3.1 Improvements in Fractionation Technologies 415

12.3.2 Titration of Functional Groups 418

12.3.3 Characterization by Fragmentation 419

12.3.4 Nuclear Magnetic Resonance (NMR) 424

12.3.5 Fluorescence Spectroscopy 433

12.3.6 Electron Spin Resonance (ESR) Spectroscopy 435

12.3.8 Microscopic Observations 440

12.3.9 Other Techniques 441

References 442

Molecular Models 442

Fractionation, Determination of Molecular Weights and Molecular Sizes 443

Functional Group of Humic Compounds 445

Spectrometric Characterizations 446

Nuclear Magnetic Resonance 447

11.2 Main Techniques 375

11.2.1 Extraction 375

11.2.2 Quantification of the Extracts 379

10.3.5 Simultaneous Analysis of the Different C and N Isotopes 364

References 365

Bibliography 367

CHAPTER 11 Quantification of Humic Compounds 11.1 Humus in Soils 371

11.1.1 Definitions 371

11.1.2 Role in the Soil and Environment 373

11.1.3 Extractions 374

11.2.4 Purification of Humic Materials 389

Humic Materials 395

Extraction, Titration, Purification and Fractionation of Humic Materials 396

12.3.7 Measurement of Molecular Weight and Molecular Size 437

10.3.4 C and N Non-Destructive Instrumental Analysis 363

UV–Visible, IR, Fluorescence, ESR Spectrometries 446

13.3 Complementary Techniques 475

13.3.2 Carbohydrates by Liquid Chromatography 475

13.3.3 Fractionation and Study of the Soil Lipid Fraction 478

13.3.4 Measurement of Pesticide Residues and Pollutants 483

References 492

CHAPTER 14 Organic Forms of Nitrogen, Mineralizable Nitrogen (and Carbon) 14.1 Introduction 497

14.1.1 The Nitrogen Cycle 497

14.1.2 Types of Methods 499

14.2 Classical Methods 500

14.2.4 Potentially Available Nitrogen: Biological Methods 513

14.2.5 Potentially Mineralizable Nitrogen: Chemical Methods 521

14.2.6 Kinetics of Mineralization 526

14.3 Complementary Methods 531

14.3.1 Alternative Procedures for Acid Hydrolysis 531

532

535

14.3.4 Proteins and Glycoproteins (glomalin) 538

14.3.5 Potentially Mineralizable Nitrogen by EUF 538

13.2.4 Titration of Sugars by Gas Chromatography 467

13.2.5 Quantification of Total Lipids 472

13.2.6 Quantification of the Water-Soluble Organics 474

CHAPTER 13 Measurement of Non-Humic Molecules 13.1 Introduction 453

13.1.1 Non-Humic Molecules 453

13.1.2 Soil Carbohydrates 453

13.1.3 Soil Lipids 456

13.1.4 Pesticides and Pollutants 457

13.2.1 Acid Hydrolysis of Polysaccharides 458

13.2.2 Purification of Acid Hydrolysates 462

13.2.3 Colorimetric Titration of Sugars 464

Methods of Characterization by Fragmentation 449

13.2 Classical Techniques 458

Other Methods (Microscopy, X-ray, Electrochemistry, etc.) 451

Soil Carbohydrates 492

Soil Lipids 494

Aqueous Extract 495

Pesticides and Pollutants 495

14.2.1 Forms of Organic Nitrogen Released by Acid Hydrolysis 500

14.2.3 Urea Titration 511

13.3.1 Carbohydrates by Gas Chromatography 475

509

14.2.2 Organic Forms of Nitrogen: Simplified Method

14.3.3 Determination of Amino Sugars

14.3.2 Determination of Amino Acids

.

CHAPTER 15 pH Measurement

15.1 Introduction 551

15.1.1 Soil pH 551

15.1.2 Difficulties 553

15.1.3 Theoretical Aspects 554

15.2 Classical Measurements 556

15.2.1 Methods 556

15.2.2 Colorimetric Method 557

15.2.3 Electrometric Method 560

15.2.4 Electrometric Checking and Calibration 564

15.2.5 Measurement on Aqueous Soil Suspensions 565

15.2.6 Determination of the pH-K and pH-Ca 567

15.2.7 Measurement on Saturated Pastes 567

15.2.8 Measurement on the Saturation Extract 568

15.2.9 Measurement of the pH-NaF 569

15.3 In Situ Measurements 570

15.3.1 Equipment 570

15.3.2 Installation in the Field 570

15.3.3 Measurement on Soil Monoliths 572

References 574

Bibliography 575

Appendix 576

Appendix 1: Table of Electrode Potentials 576

Appendix 2: Constants of Dissociation of Certain Equilibriums 577

Appendix 3: Buffer Solutions 577

Appendix 4: Coloured Indicators 579

CHAPTER 16 Redox Potential 16.1 Definitions and Principle 581

16.2 Equipment and Reagents 583

16.2.1 Electrodes 583

16.2.2 Salt Bridge for Connection 584

16.2.3 System of Measurement 584

16.2.4 Calibration Solutions 585

Determination of Amino Acids 541

Determination of Amino Sugars 542

Glomalin 542

Urea Titration 543

Potentially Mineralizable Nitrogen: General Papers 543

Potentially Mineralizable Nitrogen: Biological Methods 544

Potentially Mineralizable Nitrogen: Chemical Methods 545

Potentially Mineralizable Nitrogen by EUF 545

Mineralization Kinetics 546

References 540

Organic Nitrogen Forms: General Articles 540

Nitrogen Forms by Acid Hydrolysis and Distillation 541

Improvement of Acid Hydrolysis 541

PART 3 - INORGANIC ANALYSIS – Exchangeable and Total Elements

17.2.2 Volumetric Measurement by Calcimetry 596

17.2.3 Acidimetry 599

17.3 Titration of Active Carbonate 601

17.3.1 Principle 601

17.3.2 Implementation 601

17.3.3 Index of Chlorosis Potential 603

References 604

CHAPTER 18 Soluble Salts 18.1 Introduction 605

18.2 Extraction 606

18.2.1 Soil/solution Ratio 606

18.2.2 Extraction of Saturated Paste 607

18.2.3 Diluted Extracts 608

18.2.4 In Situ Sampling of the Soil Water 609

18.2.5 Extracts with Hot Water 610

18.3 Measurement and Titration 610

18.3.1 Electrical Conductivity of Extracts 610

18.3.2 In Situ Conductivity 613

18.3.3 Total Dissolved Solid Material 614

18.3.4 Soluble Cations 615

18.3.5 Extractable Carbonate and Bicarbonate (Alkalinity) 616

18.3.6 Extractable Chloride 618

18.3.7 Extractable Boron 620

18.3.8 Titration of Extractable Anions by Ionic Chromatography 622

18.3.9 Expression of the Results 625

References 626

CHAPTER 19 Exchange Complex 19.1 Introduction 629

19.2 Origin of Charges 630

19.2.1 Ionic Exchange 630

16.3.5 Measurement of Oxygen Diffusion Rate 588

16.3.6 Colorimetric Test of Eh 589

References 589

Bibliography 590

CHAPTER 17 Carbonates 17.1 Introduction 593

17.2 Measurement of Total Carbonates 595

17.2.1 Introduction 595

16.3 Procedure 585

16.3.1 Pretreatment of the Electrode 585

16.3.2 Measurement on Soil Sample 586

16.3.3 Measurement on Soil Monolith 586

16.3.4 In Situ Measurements 587

18.3.7 Extractable Sulphate, Nitrate and Phosphate 620

CHAPTER 21 Permanent and Variable Charges

21.1 Introduction 657

21.2 Main Methods 661

21.2.1 Measurement of Variable Charges 661

21.2.2 Determination of Permanent Charges 662

References 664

Bibliography 665

CHAPTER 22 Exchangeable Cations 22.1 Introduction 667

22.1.1 Exchangeable Cations of Soil 667

22.1.2 Extracting Reagents 668

22.1.3 Equipment 669

22.2 Ammonium Acetate Method at pH 7 671

22.2.1 Principle 671

22.2.2 Procedure 671

22.3 Automated Continuous Extraction 674

References 674

Bibliography 676

CHAPTER 23 Exchangeable Acidity 23.1 Introduction 677

23.1.1 Origin of Acidity 677

23.1.2 Aims of the Analysis 678

23.2 Method 680

23.2.1 Principle 680

23.2.2 Reagents 680

23.2.3 Procedure 681

23.3 Other Methods 683

References 684

Chronobibliography 685

CHAPTER 20 Isoelectric and Zero Charge Points 20.1 Introduction 645

20.1.1 Charges of Colloids 645

20.1.2 Definitions 647

20.1.3 Conditions for the Measurement of Charge 649

20.2 Main Methods 651

References 655

19.2.2 Exchange Complex 631

19.2.3 Theory 633

References 636

Chronobibliography 637

651

652

20.2.1 Measurement of pH0 (PZSE), Long Equilibrium Time

20.2.2 Point of Zero Salt Effect (PZSE), Short Equilibrium Time

25.2.3 Procedure 703

25.2.4 Remarks 704

References 705

Chronobibliography 706

CHAPTER 26 Cation Exchange Capacity 26.1 Introduction 709

26.1.1 Theoretical Aspects 709

26.2 Determination of Effective CEC by Summation (ECEC) 718

26.2.1 Principle 718

26.2.2 Alternative Methods 718

26.3 CEC Measurement at Soil pH in Not-Buffered Medium 719

26.3.1 Principle 719

26.3.2 Methods Using Not-Buffered Metallic Salts 719

26.3.3 Procedure Using Not-Buffered Organo Metallic Cations 722

26.4 CEC Measurement in Buffered Medium 730

26.4.1 Buffered Methods — General Information 730

26.4.2 Ammonium Acetate Method at pH 7.0 732

26.4.3 Buffered Methods at pH 8.0–8.6 738

26.4.4 Buffered Methods at Different pH 743

References 745

Bibliography 750

Barium Method at soil pH 751

Buffered Method at pH 7.0 751

Cobaltihexamine CEC 752

Silver-Thiourea 753

24.2.3 Procedure 691

24.2.4 Remarks 692

References 693

Chronobibliography 693

CHAPTER 25 Exchange Selectivity, Cation Exchange Isotherm 25.1 Introduction 697

25.2 Determination of the Exchange Isotherm 702

25.2.1 Principle 702

25.2.2 Reagents 702

CHAPTER 24 Lime Requirement 24.1 Introduction 687

24.1.1 Correction of Soil Acidity 687

24.1.2 Calculation of Correction 688

24.2 SMP Buffer Method 690

24.2.1 Principle 690

24.2.2 Reagents 691

26.3.4 Not-Buffered Methods Using Organic Cations 728

CEC General Theory 750

CEC with Organic Cations (Coloured Reagents) 753

Buffered Methods at pH 8.0–8.6 753

Barium Chloride-Triethanolamine at pH 8.1 753

26.1.2 Variables that Influence the Determination of CEC 711

28.2.2 Separation by Micro-Diffusion 770

28.2.3 Colorimetric Titration of Ammonium 773

28.2.4 Colorimetric Titration of Nitrites 775

28.2.5 Colorimetric Titration of Nitrates 778

28.2.6 Extracted Organic Nitrogen 779

28.3 Other Methods 780

28.3.1 Nitrate and Nitrite by Photometric UV Absorption 780

28.3.2 Ammonium Titration Using a Selective Electrode 782

28.3.3 Measurement of Nitrates with an Ion-Selective Electrode 785

28.3.4 In situ Measurement 788

28.3.5 Non-Exchangeable Ammonium 790

References 791

Bibliography 792

CHAPTER 29 Phosphorus 29.1 Introduction 793

29.2 Total Soil Phosphorus 794

29.2.1 Introduction 794

29.2.2 Wet Mineralization for Total Analyses 795

29.2.3 Dry Mineralization 798

29.3 Fractionation of Different Forms of Phosphorus 799

29.3.1 Introduction 799

29.3.2 Sequential Methods 800

29.3.3 Selective Extractions – Availability Indices 804

29.3.4 Isotopic Dilution Methods 813

29.3.5 Determination of Organic Phosphorus 814

29.4 Retention of Phosphorus 818

29.4.1 Introduction 818

29.4.2 Determination of P Retention 819

28.1 Introduction 767

28.1.1 Ammonium, Nitrate and Nitrite 767

28.1.3 Sampling Problems 768

28.1.4 Analytical Problems 768

28.2.1 Extraction of Exchangeable Forms 769

CHAPTER 27 Anion Exchange Capacity 27.1 Theory 755

27.2 Measurement 758

27.2.1 Principle 758

27.2.2 Method 760

27.3 Simultaneous Measurement of AEC, EC, CEC and net CEC 760

27.3.1 Aim 760

27.3.2 Description 761

References 763

CHAPTER 28 Inorganic Forms of Nitrogen 28.2 Usual Methods 769

30.2.8 Sulphate Titration by Colorimetry with Methyl Thymol Blue 850

30.2.9 Total Sulphur by Automated Dry CHN(OS) Ultimate Analysis 853

30.2.10 Titration of Total SO 42–-S by Ionic Chromatography 855

30.2.11 Total S Titration by Plasma Emission Spectrometry 857

30.2.12 Titration by X-ray Fluorescence 857

30.2.13 Titration by Atomic Absorption Spectrometry 857

30.2.14 Analytical Fractionation of Sulphur Compounds 858

30.2.15 Titration of Organic S bound to C 859

30.2.16 Titration of Organic S not bound to C 861

30.2.17 Extraction and Titration of Soluble Sulphides 863

30.2.18 Titration of Sulphur in Pyrites 865

30.2.19 Titration of Elementary Sulphur 867

30.2.20 Titration of Water Soluble Sulphates 869

30.2.21 Titration of Na 3 -EDTA Extractable Sulphates 871

30.2.22 Titration of Jarosite 873

30.2.23 Sequential Analysis of S Forms 876

30.3 Sulphur of Gypseous Soils 878

30.3.1 Gypseous Soils 878

30.3.2 Preliminary Tests 879

30.3.3 Extraction and Titration from Multiple Extracts 881

30.3.4 Gypsum Determination by Acetone Precipitation 882

30.4 Sulphur and Gypsum Requirement of Soil 883

30.4.1 Introduction 883

30.4.2 Plant Sulphur Requirement 884

30.4.3 Gypsum Requirement 886

References 888

Chronobibliography 890

30.2.4 Titration of Total Sulphur 842

30.2.5 Total S Solubilisation by Alkaline Oxidizing Fusion 843

30.2.6 Total Solubilisation by Sodium Hypobromite in Alkaline Medium 844

30.2.7 S titration with Methylen Blue Colorimetry 845

CHAPTER 30 Sulphur 30.1 Introduction 835

30.1.1 Sulphur Compounds 835

30.1.2 Mineralogical Studies 838

30.2.1 Characteristics of Fluviomarine Soils 839

30.2.3 Testing for Soluble Sulphur Forms 841

29.5 Titration of P in the Extracts 821

29.5.1 Introduction 821

29.5.2 Titration of Ortho-phosphoric P by Spectrocolorimetry 823

29.5.4 Titration of Different Forms of P by 31P NMR 828

29.5.5 Separation of P Compounds by Liquid Chromatography 829

References 830

Chronobibliography 833

29.6 Direct Speciation of P in situ, or on Extracted Particles 830

30.2 Total Sulphur and Sulphur Compounds 839

30.2.2 Soil Sampling and Sample Preparation 840

29.5.3 P Titration by Atomic Spectrometry 828

31.3.1 Method 952

31.3.3 Neutron Activation Analysis 962

References 969

INDEX ……….975

PERIODIC TABLE OF THE ELEMENTS 993

31.2.11 Analysis by Flame Atomic Absorption Spectrometry 932

31.2.12 Analysis of Trace Elements by Hydride and Cold Vapour AAS 937

941

31.2.15 Analysis by Inductively Coupled Plasma-Mass Spectrometry 946

31.2.3 Acid Attack in Open Vessel 906

31.2.4 Acid Attack in Closed Vessel 911

31.2.5 Microwave Mineralization 913

31.2.6 Alkaline Fusion 915

31.2.7 Selective Extractions 920

31.2.8 Measurement Methods 925

CHAPTER 31 Analysis of Extractable and Total Elements 31.1 Elements of Soils 895

31.1.1 Major Elements 895

31.1.2 Trace Elements and Pollutants 897

31.1.3 Biogenic and Toxic Elements 899

31.1.4 Analysis of Total Elements 900

31.1.5 Extractable Elements 901

31.2 Methods using Solubilization 901

31.2.1 Total Solubilization Methods 901

31.2.2 Mean Reagents for Complete Dissolutions 903

31.3 Analysis on Solid Medium 952

Contents XIX 31.2.9 Spectrocolorimetric Analysis .927

31.2.10 Analysis by Flame Atomic Emission Spectrometry 931

31.2.13 Analysis of Trace Elements by Electrothermal AAS 940

31.2.14 Analysis by Inductively Coupled Plasma-AES

31.3.2 X-ray Fluorescence Analysis 954

P art 1

Water Content and Loss on Ignition

1.1 Introduction

Schematically, a soil is made up of a solid, mineral and organic phase, a liquid phase and a gas phase The physical and chemical characteristics of the solid phase result in both marked variability of water contents and a varying degree of resistance to the elimination of moisture

For all soil analytical studies, the analyst must know the exact quantity

of the solid phase in order to transcribe his results in a stable and reproducible form The liquid phase must be separate, and this operation must not modify the solid matrix significantly (structural water is related

to the crystal lattice)

Many definitions exist for the terms “moisture” and “dry soil” The water that is eliminated by moderate heating, or extracted using solvents, represents only one part of total moisture, known as hygroscopic water, which is composed of (1) the water of adsorption retained on the surface

of solids by physical absorption (forces of van der Waals), or by chemisorption, (2) the water of capillarity and swelling and (3) the hygrometrical water of the gas fraction of the soil (ratio of the effective pressure of the water vapour to maximum pressure) The limits between these different types of water are not strict

“Air-dried” soil, which is used as the reference for soil preparation in the laboratory, contains varying amounts of water which depend in particular on the nature of secondary minerals, but also on external forces (temperature, the relative humidity of the air) Some andisols or histosols

in comparison with soils dried at 105°C, and this can lead to unacceptable errors if the analytical results are not compared with a more realistic that are air dried for a period of 6 months can still contain 60% of water

reference for moisture.1 Saline soils can also cause problems because of the presence of hygroscopic salts

It is possible to determine remarkable water contents involving fields of force of retention that are sufficiently reproducible and representative (Table 1.1) These values can be represented in the form of capillary potential (pF), the decimal logarithm of the pressure in millibars needed

to bring a sample to a given water content (Table 1.1) It should be noted that because of the forces of van der Waals, there can be differences in state, but not in form, between water likely to evaporate at 20°C and water that does not freeze at –78°C The analyst defines remarkable points for example:

component of the total potential becomes more significant than the gravitating component; this depends on the texture and the nature of the

mineral and approaches field capacity which, after suitable drainage,

corresponds to a null gravitating flow

water film becomes monomolecular and breaks

– The points of temporary and permanent wilting where the pellicular

water retained by the bonding strength balances with osmotic pressure;

in this case, except for some halophilous plants, the majority of plants can no longer absorb the water that may still be present in the soil

environment as this requires considerable energy, hygroscopic water evaporates at temperatures above 100°C and does not freeze at –78°C

– The water of constitution and hydration of the mineral molecules can

only be eliminated at very high pressures or at high temperatures, with irreversible modification or destruction of the crystal lattice

These types of water are estimated using different types of measurements to study the water dynamics and the mechanisms related to the mechanical properties of soils in agronomy and agricultural engineering, for example:

easily available in soil–water–plant relations

etc.)

1 It should be noted that for these types of soil, errors are still amplified by the ponderal expression (because of an apparent density that is able to reach 0.3) this is likely to make the analytical results unsuitable for agronomic studies

– The water holding capacity, water content where the pressure

– The hygroscopic water which cannot be easily eliminated in the natural

–

–

usable reserves (UR), easily usable reserves (EUR), or reserves that are

thresholds of plasticity, adhesiveness, liquidity (limits of Atterberg,

– The capillary frangible point, a state of moisture where the continuous

T Approximate correspondence moistures – pressure – diameter of the pores – ty

This brief summary gives an indication of the complexity of the concept of soil moisture and the difficulty for the analyst to find a scientifically defined basis for dry soil where the balance of the solid, liquid and gas phases is constant

1.2.2 Materials

flat top cap

– Vacuum type Ø 200 mm desiccator made of borosilicate glass with removable porcelain floor, filled with anhydrous magnesium perchlorate [Mg(ClO4)2]

– Thermostatically controlled drying oven with constant speed blower for air circulation and exhausting through a vent in the top of oven – temperature uniformity ± 0.5–1°C

– Analytical balance: precision 0.1 mg, range 100 g

1.2.3 Sample

It is essential to measure water content on the same batch of samples prepared at the same time (fine earth with 2 mm particles or ground soil) for subsequent analyses It should be noted that the moisture content of the prepared soil may change during storage (fluctuations in air moisture and temperature, oxidation of organic matter, loss or fixing of volatile substances, etc.)

1.2 Water Content at 105°C (H O )

Samples dried at 105°C should generally not be used for other measurements

1.2.4 Procedure

– Dry tared weighing bottles for 2 h at 105°C, let them cool in the

– Place about 5 g of air-dried soil (fine earth sieved through a 2 mm

– Place the weighing bottles with their flat caps placed underneath in a ventilated drying oven for 4 h at 105°C (the air exit must be open and the drying oven should not be overloaded)

– Cool in the desiccator and weigh (all the lids of the series contained in

– Again place the opened weighing bottles in the drying oven for 1 h at 105°C and weigh under the same conditions; the weight should be constant; if not, continue drying the weighing bottles until their weight

is constant

0 1

2 1

m m

m m

2 1

100HC

m m

m m

Respecting the procedure is thus essential:

– For andisols and histosols, the initial weighing should be systematically carried out after 6 h

– For saline soils with large quantities of dissolved salts, the sample can

be dried directly, soluble salts then being integrated into the “dry soil”

or eliminated beforehand by treatment with water

1.3.1 Introduction

As we have just seen, the reference temperature (105°C) selected for the determination of the moisture content of a “dry soil” represents only a

When a sample undergoes controlled heating and the uninterrupted ponderal variations are measured, curves of “dehydration” are obtained whose inflections characterize losses in mass at certain critical temperatures (TGA) If one observes the temperature curve compared to

a thermically inert substance (Fig 1.2), it is possible to determine changes in energy between the sample studied and the reference substance, this results in a change in the temperature which can be

(dehydroxylation), sublimation, or evaporation, or decomposition of certain substances, etc

peak appears that characterizes transformations of crystalline structures,

If the temperature decreases compared to the reference, an endothermic

If the temperature increases compared to the reference, an exothermic

TGA thermogravimetric analysis; DTA differential thermal analysis; DSA

differential scanning calorimetry (cf Chap 7)

1

Fig 1.2 - Schematized

example of thermal

analysis curves

TGA (solid line) and

DTA (dashed line)

The simultaneous analysis of the gases or vapours that are emitted and X-ray diffraction (cf Chap 4) of the modifications in structure make it possible to validate the inflections of the curves or the different endo- and exothermic peaks

As can be seen in the highly simplified Table 1.2, the most commonly observed clays are completely dehydroxyled at 1,000°C, oxides at 400°C

or 500°C, carbonates, halogens, sulphates, sulphides are broken down or dehydrated between 300°C and 1,000°C, and free or bound organic matter between 300°C and 500°C The temperature of 1,000°C can thus

be retained as a stable reference temperature for loss on ignition, the thermal spectra then being practically flat up to the peaks of fusion which generally only appear at temperatures higher than 1,500°C or even 2,500°C

1.3.2 Principle

The sample should be gradually heated in oxidizing medium to 1,000°C and maintained at this temperature for 4 h

salts as a function of temperature in °C

type name dehydrationa dehydroxylationb

clays 1:1 Kaolinite–halloysite 350 1,000

clays 2:1 smectites –

montmorillonite

370 1,000 clays 2:1 Illite – micas 350–370 1,000

clays 2:1 vermiculite 700 1,000

fibrous clays Sepiolite–

palygorskite allophane

300

200

800–900 900–1,000

iron oxides Hematite α Fe2O3 (flat

– 800–940

halogenous

compounds

sodium chloride NaCl

a Dehydration: loss of water adsorbed on outer or inner surfaces, with

or without reversible change in the lattice depending on the types of

atoms or around exchangeable cations

b dehydroxylation (+ decarbonatation and desulphurization reactions),

loss of water linked to lattice (OH−), irreversible reaction or

destruction of the structure, water present in the cavities, O forming

the base of the tetrahedrons

Table 1.2 Dehydration and dehydroxylation of some clays, oxides and

clay, water organized in monomolecular film on surface oxygen

Loss on ignition is determined by gravimetry It includes combined water linked to the crystal lattice plus a little residual non-structural

essential to ensure combustion of the organic matter and in particular oxidation of reduced forms of iron, this being accompanied by an

on the same sample

1.3.3 Equipment

– Platinum or Inconel (Ni–Cr–Fe) crucible with cover, diameter 46 mm

electronic regulation allowing modulation of the impulses with oscillation of about 1°C around the point of instruction; built-in ventilation system for evacuation of smoke and vapour

– Thermal protective gloves

– 300 mm crucible tong

1.3.4 Procedure

– Tare a crucible, heat it to 1,000°C and cool it in the desiccator with its

– Dry in the drying oven at 105°C for 4 h

– Adjust the lid of the crucible so it covers approximately 2/3 of the crucible and put it in the electric furnace

– Programme a heating gradient of approximately 6°C per minute with a 20-min stage at 300°C, then a fast rise at full power up to 1,000°C with

a 4-h graduation step (the door of the furnace should only be closed after complete combustion of the organic matter)

1.3.5 Calculations

m 2 m 0 = weight of soil dried at 105°C

at 105°C, thus simplifying calculations during analyses of the samples

To obtain the equivalent of 1 g of soil dried at 105°C, it is necessary to weigh:

wc

− 100

100

Platinum crucibles are very expensive and are somewhat volatile at 1,000°C, which means they have to be tared before each operation, particularly when operating in reducing conditions

Combustion of organic matter with insufficient oxygen can lead to the formation of carbide of Pt, sulphides combine with Pt, chlorine attacks Pt, etc

Bibliography

Campbell GS, Anderson RY (1998) Evaluation of simple transmission line

Chin Huat Lim, Jackson ML (1982) Dissolution for total elemental analysis In

Dubois J, Paindavoine JM (1982) Humidité dans les solides, liquides et gaz

oscillators for soil moisture measurement Comput and Electron Agric

Dixon JB (1977) Minerals in soil environments Soil Sci Soc Am

Techniques de l ingénieur (P 3760)

1–164 Lane PNJ, Mackenzie DH, Nadler AD (2002) Note of clarification about: Field and laboratory calibration and test of TDR and capacitance techniques for 555–1386

Henin S (1977) Cours de physique du sol: l'eau et le sol tome II., Editest, Paris:

indirect measurement of soil water content Aust J Soil Res., 40,

wc = % water content of air dried soil

with

.,

Methods of Soil Analysis, Part 2, Page A.L., Miller R.H., Kenny D.R ed

Gardner WH (1986) Water content In Methods of Soil Analysis, Part 1, Klute

Lane PNJ, Mackenzie DH (2001) Field and laboratory calibration and test of

NF ISO 11465 (X31-102) (1994) Détermination de la teneur pondérale en

Skierucha W (2000) Accuracy of soil moisture measurement by TDR technique Slaughter DC, Pelletier MG, Upadhyaya SK (2001) Sensing soil moisture using Walker JP, Houser PR (2002) Evaluation of the Ohm Mapper instrument for soil X31-505 (1992) Méthode de détermination du volume, apparent, et du contenu

Yu C, Warrick AW, Conklin MH (1999) Derived functions of time domain 1789–1796

Rankin LK, Smajstrla AG (1997) Evaluation of the carbide method for soil

TDR and capacitance techniques for indirect measurement of soil Aust

NIR spectroscopy Appl Eng Agric., 17, 241–247

moisture measurement Soil Sci Soc Am J., 66, 728–734

en eau des mottes In Qualité des sols, AFNOR, 1996, 373–384

reflectometry for soil moisture measurement Water Resour Res., 35,

2

Particle Size Analysis

2.1 Introduction

2.1.1 Particle Size in Soil Science

Determination of grain-size distribution of a sample of soil is an important

fields such as road geotechnics

Soil texture has an extremely significant influence on the physical and mechanical behaviours of the soil, and on all the properties related to water content and the movement of water, (compactness, plasticity, thrust

Particle size analysis of a sample of soil, sometimes called “mechanical analysis”, is a concept that has been the subject of much discussion (Hénin 1976) Soil is an organized medium including an assemblage of mineral and organic particles belonging to a continuous dimensional series The first difficulty is to express the proportion of these different particles according to a standard classification, which is consequently somewhat artificial

One classification scale was proposed by Atterberg (1912) Today this scale is recognized at different national and international levels and includes two main fractions: fine earth (clay, silts and sands with a grain diameter <2 mm) and coarse elements (gravels, stones with a grain diameter >2 mm) The particle size series (Fig 2.1) for fine earth is generally expressed after analysis in three size fractions (clay fraction less than 0.002 mm, silt fraction from 0.002 to 0.02 mm, and sand fraction from 0.02 to 2 mm) In some countries, or for the purpose of a particular type of pedological interpretation, a more detailed scale of classes is sometimes used, for example five fractions: fine clays, silts, coarse silts or very fine sands, fine sands, and coarse sands (Fig 2.1)

force, slaking, holding capacity, moisture at different potentials, meability, capillary movements, etc.)

Fig 2.1 Ranges of particle size used for soils (NC number of classes; FSi fine

silts, CSi coarse silts; FS, VFS, CS fine, very fine and coarse sands, respectively; FC fine clays; FG, CG fine gravels and coarse gravels), from top to bottom: (CSSC) Canadian Soil Survey Committee (1978): 10 particle size ranges < 2 mm; France (before 1987): 8 ranges; USDA United States Department of Agriculture (1975): 7 ranges; AFNOR

Another difficulty appears with the fractionation of elementary particles by dissociating them from their original assembly Here too analytical standards exist, but it should be recognized that in certain cases the rupture of all the forces of cohesion is not complete (the case in hardened cemented soils), or on the contrary the forces are too energetic Lastly, particle size analysis accounts for the size but not for the shape

of the particles, or their nature If necessary, these are the subject of

Association Française de Normalisation

specific morphoscopic and mineralogical analyses The result of particle size analysis is expressed in classes of which the relative proportions can

be summed up in the form of a triangular diagram enabling the texture of

a sample, a horizon, or a soil to be defined Depending on the school, there are several different types of triangles that represent textures:

GEPPA (Groupe d’Etude des Problèmes de Pédologie Appliquée, AFES,

Grignon, France) includes 17 textural classes; the USDA’s (United States Department of Agriculture) includes 12 classes (Gras 1988); others are simplified to a greater or lesser extent depending on the pedological or agronomic purpose of the study Starting from these results, different interpretations are usually made in terms of pedogenesis (comparison of the vertical sand percents to check the homogeneity of a given material in

a given soil profile, calculation of different indices of leaching, clay transport, etc.); others are more practical (definition of the relation of

texture to hydric characteristics for the initial calculation of the amounts

and frequencies of irrigation, or for the choice of machinery for cultivation

2.1.2 Principle

Particle size analysis is a laboratory process, which initially causes dissociation of the material into elementary particles; this implies the destruction of the aggregates by eliminating the action of cements But this action should not be too violent to avoid the creation of particles that would not naturally exist; the procedure of dispersion must thus be sufficiently effective to break down the aggregates into individual components, but not strong enough to create neo-particles

Measurements (Table 2.1, Fig 2.2) then will link the size of the particles to physical characteristics of the suspension of soil after

dispersion (cf Sect 2.1.3) These measurements may be distorted by the

presence of some compounds in the soil: organic matter, soluble salts, sesquioxides, carbonates, or gypsum The latter compound can be particularly awkward because it can result in two opposing actions (Vieillefon 1979): flocculation due to soluble calcium ions (relative reduction in clay content), and low density of gypsum compared to other minerals (increase in clay content) Particle size analysis thus generally starts with a pre-treatment of the sample that varies with the type of soil; the characteristics of different soils are given in Table 2.3

Fig 2.2 Particle size ranges of some automated particle-measurement instruments

2.1.3 Law of Sedimentation

After possible pretreatment (cf Sect 2.2.1), the sample is suspended in

aqueous medium in the presence of a dispersant (cf Sect 2.2.2) During

sedimentation, the particles are then subjected to two essential forces: a force of gravity that attracts them to the bottom, and a force of viscous resistance of the medium in the opposite direction to their displacement

(dynes) is expressed by:

ρf = density of the liquid of dispersion in g cm–3;

–

–

– –

from which their drop speed can be estimated according to the law

originally established by Stokes (1851):

For calculations, the average density of the solid particles in

particle-size distribution of soils (Gee and Bauder 1986):

The constant of Stokes for the medium can thus be defined by:

C = 2 (ρs – ρf ) g/9 η

Equation (2.1) shows that the falling speed is proportional to the

square of the particle radius and remains constant throughout

sedimentation if certain conditions are strictly respected (cf Sect 2.1.4)

The speed can also be defined by V = h/t where T is the time (s) spent by

the particle of radius r(cm) to fall a height H(cm) Either the depth of its

sedimentation over a given period, or the time needed for sedimentation

to a given depth is determined by:

Table 2.1.

Coulter Quantimat 720 Micro- Videomat (Zeiss) Integramat (Leitz)

separation techniques used – measurement

monochromatic light or laser)

laser: high intensity

measurement of densimeter depth

densimeter (Casagrande, ASTM )

fractionation: one static liquid phase – one solid mobile phase, no deformation, no reaction w

particles, effective surface charge

Particle size analysis by sedimentation consists in determining the content of particles below or equal to a given threshold Known volumes

of solution (pipette method) are generally used for the depth and time of sedimentation chosen as the threshold for a cut point After drying the pipette sample, weighing and correcting the volume, the content of particles that are smaller than the selected threshold can be determined In the example in Table 2.2, a pipette sample at a temperature of 20°C, a depth of 10 cm and 8 h 08 min of sedimentation will give the content of

In the densimetry method, the relation between the size of the particles

(radius r) and the time of sedimentation t can be expressed by:

where S is the parameter of sedimentation Taking into account (2.3), it can be expressed by:

represents the effective measurement depth of the particles of radius r

2.1.4 Conditions for Application of Stokes Law

The formula of Stokes is theoretically only valid for particles with a diameter of less than 0.1 mm, but according to Mériaux (1954), it can be used up to 0.2 mm or even 0.05 mm Above this value, it is advisable to apply the formula of Oseen; however, particles more than 0.1 mm in diameter can be more precisely sorted by sieving

For particle size analysis, sedimentation cylinders are used whose walls slow down the falling speed of the particles by friction Thus, for 0.05 mm quartz spheres, the falling speed at a distance of 0.1 mm from the walls is reduced by 12%, and disturbance becomes negligible at 1 mm (0.28%) In practice, it may be advantageous to use sedimentation tubes (cylinders) with a rather large diameter, at least 5 cm

In addition, the constant of Stokes is established for minerals with an average density of 2.60 or 2.65, whereas soil materials can contain illite with a density of 2.1 – 2.7, montmorillonite with a density of 1.7 – 2.6 and so on But the main difficulty is the fact that the particles are neither spherical, nor smooth, which obliges the analyst to introduce the concept

of equivalent radius