handbook of soil analysis

Marc Pansu Jacques Gautheyrou Handbook of Soil Analysis Mineralogical, Organic and Inorganic Methods

Marc Pansu Jacques Gautheyrou

Handbook of Soil Analysis

Mineralogical, Organic and Inorganic Methods

with 183 Figures and 84 Tables

Avenue Agropolis 911

France E-mail : [email protected]

Avenue de Marinville 6 94100 St. Maur des Fosss France Updated English version, corrected by Daphne Goodfellow. The original French book "L'analyse du sol, minralogique et minrale" 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 of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag. Violations are liable to prosecution under the German Copyright Law. Springer is a part of Springer Science+Business Media springer.com Springer-Verlag Berlin Heidelberg 2006 Printed in The Netherlands The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Cover design: E. Kirchner, Heidelberg Production: Almas Schimmel Typesetting: SPI Publisher Services Printing: Krips bv, Meppel Binding: Strtz AG, Wrzburg Printed on acid-free paper 30/3141/as 5 4 3 2 1 0

Dr Marc Pansu Centre IRD BP 64501

34394 Montpellier Cedex 5

Jacques Gautheyrou

FOREWORD

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

visible, 1 13

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, UV-

H-NMR, C- NMR, ESR, ICP-AES, ICP-MS, X-ray

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.

Alain Aventurier, Director of Analytical Laboratories of CIRAD1 2

3

1 CIRAD, Centre International pour la Recherche Agronomique et le

Dveloppement (France). 2 IRD, Institut de Recherche pour le Dveloppement (ex ORSTOM, France).

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

VI Foreword

others in related disciplines, such as, analytical physical chemistry,

Christian Feller, Director of Research at IRD

Pierre Bottner, Director of Research at CNRS

CONTENTS

PART 1 - MINERALOGICAL ANALYSIS

CHAPTER 1 Water Content and Loss on Ignition 1.1 Introduction ..................................................................................................3 1.2 Water Content at 105C (H2O) ....................................................................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 1,000C (H2O+) ..............................................................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-Khn 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

VIII Contents

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

Contents IX

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 NO3, NO2 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


X Contents

10.2.2 Organic Carbon by Wet Oxidation at the Temperatureof Reaction ................................................................335 ......................

10.2.3 Organic Carbon by Wet Oxidation at Controlled Temperature10.2.4 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 UVVisible 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

Contents XI

10.3.4 C and N Non-Destructive Instrumental Analysis..............................363

UVVisible, 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

XII Contents

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

Contents XIII

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

XIV Contents

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


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


.....................651 ................652

Contents XV

20.2.1 Measurement of pH0 (PZSE), Long Equilibrium Time20.2.2 Point of Zero Salt Effect (PZSE), Short Equilibrium Time

25.2.3 Procedure........................................................................................703 25.2.4 Remarks ..........................................................................................704


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 8.08.6......................................................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


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 8.08.6.................................................................753 Barium Chloride-Triethanolamine at pH 8.1 ............................................... 753

XVI Contents

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


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

Contents XVII

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 SO42-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 Na3-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


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


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

XVIII Contents

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 .

Part 1

Mineralogical Analysis

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 105C, 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 20C and

water that does not freeze at 78C. 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 100C and does not freeze at 78C.

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 soilwaterplant 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.

4

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


Tabl

e 1.

1 -

Appr

oxim

ate

corr

esp

onde

nce

mois

ture

s

pres

sure

diam

eter

of t

he

pore

s

type

s of

w

ater

and

crit

ical

poin

ts in

soi

ls wi

th

resp

ect t

o pl

ant

requ

irem

ents

5 Water Content and Loss on Ignition

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.

2

1.2.1 Principle

By convention, the term moisture is considered to be unequivocal.

Measurement is carried out by gravimetry after drying at a maximum

temperature of 105C. This increase in temperature maintained for a

controlled period of time, is sufficiently high to eliminate free forms of

water and sufficiently low not to cause a significant loss of organic matter

and unstable salts by volatilization. Repeatability and reproducibility are

satisfactory in the majority of soils if procedures are rigorously respected.

1.2.2 Materials

flat top cap.

Vacuum type 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 0.51C.

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 105C (H O )

50 30 mm borosilicate glass low form weighing bottle with ground

6 Mineralogical Analysis

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

measurements.

1.2.4 Procedure

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

desiccator and weigh the tare with the lid placed underneath: m0

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

mesh) in the tare box and note the new weight: m1

Place the weighing bottles with their flat caps placed underneath in a

ventilated drying oven for 4 h at 105C (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

the desiccator should be closed to avoid moisture input): m2

Again place the opened weighing bottles in the drying oven for 1 h at

105C and weigh under the same conditions; the weight should be

constant; if not, continue drying the weighing bottles until their weight

is constant

01

21

mm

mm

1.2.5 Remarks

The results can also be expressed in pedological terms of water holding

capacity (HC) by the soil:

02

21100HCmm

mm

=

The point of measurement at 105C with constant mass is empirical

(Fig. 1.1). A temperature of 130C makes it possible to release almost all

interstitial water, but this occurs to the detriment of the stability of

organic matter. The speed of drying should be a function of the

temperature, the surface of diffusion, the division of the solid, ventilation,

pressure (vacuum), etc.

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.

% water content at 105C = 100

This method can be considered destructive for certain types of soils

and analyses, as the physical and chemical properties can be transformed.

.

.

Water Content and Loss on Ignition 7

Fig. 1.1 - Theoretical diagrammatic curve showing water moved at a given temperature as a function of time (180C = end of H2O losses in allophanes)

2+

1.3.1 Introduction

As we have just seen, the reference temperature (105C) selected for the

determination of the moisture content of a dry soil represents only a

totally hypothetical state of the water that is normally referred to as H2O_

.

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

measured (DTADSC).2

peak appears that characterizes loss of H2O (dehydration), of OH_

(dehydroxylation), sublimation, or evaporation, or decomposition of

certain substances, etc.

peak appears that characterizes transformations of crystalline structures,

oxidations (Fe2+ Fe3+), etc.

2

1.3 Loss on Ignition at 1,000C (H O )

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 1,000C, oxides at 400C

or 500C, carbonates, halogens, sulphates, sulphides are broken down or

dehydrated between 300C and 1,000C, and free or bound organic

matter between 300C and 500C. The temperature of 1,000C 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 1,500C or even

2,500C.


1.3.2 Principle

The sample should be gradually heated in oxidizing medium to 1,000C

and maintained at this temperature for 4 h.

salts as a function of temperature in C

type name dehydrationa dehydroxylationb

clays 1:1 Kaolinitehalloysite 350 1,000

clays 2:1 smectites

montmorillonite

370 1,000

clays 2:1 Illite micas 350370 1,000

clays 2:1 vermiculite 700 1,000

clays 2:1:1 chlorite 600 800

fibrous clays Sepiolite

palygorskite

allophane

300

200

800900

9001,000

iron oxides

Hematite Fe2O3 (flat spectrum)

1,000

goethite FeOOH 100 370

magnetite Fe2O3 375 650

Al oxides gibbsite -Al(OH)3 100 350 Ca carbonate Calcitearagonite

CaCO3

9501,000

Mg carbonate magnesite MgCO3 710

CaMg

carbonate

dolomie

CaMg(CO3)2

800940

halogenous

compounds

sodium chloride

NaCl

800 (fusion)

sulphate gypsum CaSO4,

2H2O

300

sulphide pyrite FeS2 615

organic

compounds

free or linked organic

matter

300500

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

adsorbed water, organic matter, possibly volatile soluble salts (F, S2)

and carbonates (CO32, CO2). The use of an oxidizing atmosphere is

essential to ensure combustion of the organic matter and in particular

oxidation of reduced forms of iron, this being accompanied by an

increase in mass of the soils with minerals rich in Fe2+. A complete

analysis generally includes successive measurements of H2O and H2O

+

on the same sample.

1.3.3 Equipment

Platinum or Inconel (NiCrFe) crucible with cover, diameter 46 mm.

Analytical balances (id. H2O)

Desiccator (id. H2O)

Muffle electric furnace (range 1001,100C) with proportional

electronic regulation allowing modulation of the impulses with

oscillation of about 1C 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 1,000C and cool it in the desiccator with its

lid on: m0

Introduce 23 g of air-dried soil crushed to 0.1 mm: m1

Dry in the drying oven at 105C for 4 h

Cool in the desiccator and weigh: m2

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 6C per minute with a

20-min stage at 300C, then a fast rise at full power up to 1,000C with

a 4-h graduation step (the door of the furnace should only be closed

after complete combustion of the organic matter)

Cool the crucible in the desiccator and weigh: m3


1.3.5 Calculations

m1 m0 = weight of air-dried soil

m1 m2 = moisture at 105C

m2 m0 = weight of soil dried at 105C

m2 m3 = loss on ignition

H O % = 1002m m

m m

1 2

1 0

related to air-dried soil

H O % = 1002+ m m

m m

2 3

2 0

related to soil dried at 105C

1.3.6 Remarks

Knowing the moisture of the air-dried soil, it is possible to calculate the

weight of air-dried soil required to work with a standard weight soil dried

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

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

weigh:

wc100

100

Platinum crucibles are very expensive and are somewhat volatile at

1,000C, 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) Humidit dans les solides, liquides et gaz.

20, 3144

Am. Soc. Agronomy, pp. 111

ed. Am. Soc. Agronomy, Soil Sci. Soc. Am., pp. 493544


,oscillators for soil moisture measurement. Comput. and Electron. Agric.

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

Techniques de l ingnieur (P 3760)

1164

Lane PNJ, Mackenzie DH, Nadler AD (2002) Note of clarification about: Field

and laboratory calibration and test of TDR and capacitance techniques for

5551386

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) Dtermination de la teneur pondrale 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) Mthode de dtermination du volume, apparent, et du contenu

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

17891796

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


TDR and capacitance techniques for indirect measurement of soil. Aust. J. Soil Res., 39, 13711386

matire sche et en eau. In Qualit des sols, AFNOR, 1996, 517524

moisture measurement in sandy soils. Soil and Crop Science Society of Florida, 56, pp. 136139

Int. Agrophys., 14, 417426

NIR spectroscopy. Appl. Eng. Agric., 17, 241247

moisture measurement. Soil Sci. Soc. Am. J., 66, 728734

en eau des mottes. In Qualit des sols, AFNOR, 1996, 373384

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

(Hnin 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). 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, per-

meability, capillary movements, etc.).

analysis for various topics in pedology, agronomy, sedimentology, and other

16

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

(1987): 5 ranges; ISSS = International Soil Science Society (1966): 4 ranges; ASTM = American Society for Testing Materials (1985): 3 ranges

However, it should be noted that the terminology used does not provide

much information about the real nature of the classes; thus clay defined as

having a diameter equal to or less than 0.002 mm does not contain only

clay corresponding to this mineralogical definition but can also contain

sesquioxides, very fine silts, organic matter, carbonates, or compounds

without colloidal properties. In the same way, sands, which generally result

from fragmentation of the parent rock, can also include pseudo-sands, small

ferruginous concretions, small limestone or cemented nodules that are

resistant to dispersion treatments. The presence of these pseudo-sands can

render the conclusions of particle size analysis illusory.

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 Franaise de Normalisation

17

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 dEtude des Problmes de Pdologie Applique, AFES,

Grignon, France) includes 17 textural classes; the USDAs (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 gi

handbook of soil analysis

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