ENVIRONMENTALSOILCHEMISTRY

Donald L. SparksDepartment of Plant and Soil SciencesUniversity of DelawareNewark, Delaware

ACADEMIC PRESSSan Diego New York Boston London Sydney Tokyo Toronto

CONTENTS

PREFACE xi

ENVIRONMENTAL SOIL CHEMISTRY: AN OVERVIEW

Evolution of Soil Chemistry 2The Modern Environmental Movement 3Contaminants in Waters and Soils 4Case Study of Pollution of Soils and Waters 11Soil Decontamination 19Suggested Reading 22

INORGANIC SOIL COMPONENTS

Introduction 23Pauling's Rules 25Primary Soil Minerals 30Secondary Soil Minerals 31Specific Surface of Soil Minerals 41Surface Charge of Soil Minerals 43Identification of Minerals by X-Ray Diffraction Analyses 47Use of Clay Minerals to Retain Organic Contaminants 48Suggested Reading 51

VII

viii CONTENTS

CHEMISTRY OF SOIL ORGANIC MATTER

Introduction 53Effects of Soil Formation Factors on SOM Contents 55Composition of SOM 57Fractionation of SOM 63SOM Structure 65Functional Groups and Charge Characteristics 67Humic Substance-Metal Interactions 69SOM-Clay Complexes 77Retention of Pesticides and Other Organic Substances

by Humic Substances 78Suggested Reading 79

SOIL SOLUTION-SOLID PHASE EQUILIBRIA

Introduction 81Measurement of the Soil Solution 82Speciation of the Soil Solution 84Ion Activity and Activity Coefficients 90Dissolution and Solubility Processes 92Suggested Reading 97

SORPTION PHENOMENA ON SOILS

Introduction and Terminology. 99Surface Functional Groups 100Surface Complexes 102Adsorption Isotherms 104Equilibrium-Based Adsorption Models 107Surface Precipitation 128Sorption of Metal Cations 130Sorption of Anions 131Points of Zero Charge 134Desorption 136Use of Spectroscopic and Microscopic Methods in Determining Mechanisms

for Sorption-Desorption Phenomena 138Suggested Reading 139

6 ION EXCHANGE PROCESSES

Introduction 141Characteristics of Ion Exchange 142

CONTENTS ix

Cation Exchange Equilibrium Constants and Selectivity Coefficients 143Thermodynamics of Ion Exchange 147Relationship between Thermodynamics and Kinetics of Ion Exchange 157Suggested Reading 158

KINETICS OF SOIL CHEMICAL PROCESSES

Rate-Limiting Steps and Time Scales of Soil Chemical Reactions 159Rate Laws 161Determination of Reaction Order and Rate Constants 163Kinetic Models 165Kinetic Methodologies 169Effect of Temperature on Reaction Rates 175Kinetics of Important Soil Chemical Processes 176Suggested Reading 185

8

10

REDOX CHEMISTRY OF SOILS

Oxidation-Reduction Reactions and Potentials 187Eh vs pH and pe vs pH Diagrams 191Measurement and Use of Redox Potentials 195Submerged Soils 196Redox Reactions Involving Inorganic and Organic Pollutants 196Suggested Reading 202

THE CHEMISTRY OF SOIL ACIDITY

Introduction 203Historical Perspective of Soil Acidity 206Solution Chemistry of Aluminum 207Exchangeable and Nonexchangeable Aluminum 210Soil Acidity 212Liming Soils 216Suggested Reading 216

THE CHEMISTRY OF SALINE AND SODIC SOILS

Introduction 219Causes of Soil Salinity 220Sources of Soluble Salts 221Important Salinity and Sodicity Parameters 222Classification and Reclamation of Saline and Sodic Soils 227

CONTENTS

Effects of Soil Salinity and Sodicity on Soil Structural Properties 229Effects of Soil Salinity on Plant Growth 230Suggested Reading 232

APPENDIX A 233APPENDIX B 236REFERENCES 237INDEX 259