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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 : pansu@mpl.ird.fr
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
References ..................................................................................................... 283 Chronobibliography ...................................................................................... 284
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
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
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
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 8.08.6......................................................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
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 8.08.6.................................................................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
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
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
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
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
Mineralogical Analysis
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).
8 Mineralogical Analysis
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.
Water Content and Loss on Ignition 9
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
10 Mineralogical Analysis
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
Water Content and Loss on Ignition 11
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
12 Mineralogical Analysis
,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
Water Content and Loss on Ignition 13
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
Mineralogical Analysis
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
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