Soil and Environmental Chemistry (eBook)

Front Cover 2
Soil and Environmental Chemistry 4
Copyright 5
Dedication 6
Contents 8
Preface 16
Chapter 1: Elements: Their Origin and Abundance 18
Dose-Response Distributions 429
Introduction 18
A Brief History of the Solar System and Planet Earth 19
The Composition of Earth's Crust and Soils 20
The Abundance of Elements in the Solar System, Earth's Crust, and Soils 20
Elements and Isotopes 21
Nuclear Binding Energy 23
Enrichment and Depletion during Planetary Formation 25
Planetary Accretion 26
The Rock Cycle 29
Soil Formation 30
Concentration Frequency Distributions of the Elements 33
Estimating the Most Probable Concentration and Concentration Range Using the LOGARITHMIC TRANSFORMATION 35
Summary 38
Factors Governing Nuclear Stability and Isotope Abundance 39
The Table of Isotopes and Nuclear Magic Numbers 39
Nuclear Magic Numbers 39
Nucleosynthesis 42
Nuclear Reactions 42
Nuclear Fusion 43
Neutron Capture 45
Cosmic Ray Spallation 47
Transuranium Elements 47
Thermonuclear FUSION Cycles 49
The CNO Cycle 49
The Triple-Alpha Process 50
Carbon Burning 51
Neutron-Emitting Reactions that Sustain the S-Process 51
Random Sequential Dilutions and the Law of Proportionate Effect 52
The Estimate of Central Tendency and Variation of a Log-Normal Distribution 54
Chapter 2: Soil Moisture and Hydrology 58
Introduction 58
Water Resources and the Hydrologic Cycle 59
Water Budgets 60
Residence Time and Runoff Ratios 60
Groundwater Hydrology 62
Water in the Porosphere 62
Hydrologic Units 64
Darcy's Law 65
Hydrostatic Heads and Hydrostatic Gradients 66
Intrinsic Permeability 71
Groundwater Flow Nets 73
Vadose Zone Hydrology 75
Capillary Forces 75
Soil Moisture Zones 77
The Water Characteristic Curve and Vadose Zone Hydraulic Conductivity 79
Elementary Solute Transport Models 79
The Retardation Coefficient Model 79
Plate Theory: Multiple Sequential Partitioning 82
Summary 88
Soil Moisture Recharge and Loss 88
The Water-Holding Capacity of a Soil Profile 89
Predicting Capillary Rise 92
Symbols and Units in the Derivation of the Retardation Coefficient Model of Solute Transport 93
Symbols and Units in the Derivation of the Plate Theory Model of Solute Transport 94
Empirical Water Characteristic Function and Unsaturated Hydraulic Conductivity 96
Chapter 3: Clay Mineralogy and Clay Chemistry 102
Introduction 102
Mineral Weathering 103
Mineralogy 103
The Structure of Layer Silicates 106
Coordination Polyhedra 107
The Phyllosilicate Tetrahedral Sheet 108
The Phyllosilicate Octahedral Sheet 109
Kaolinite Layer Structure 110
Talc Layer Structure 110
Mica-Illite Layer Structure 111
Chlorite and Hydroxy-Interlayered Smectite Layer Structure 113
Layer Structure of the Swelling Clay Minerals: Smectite and Vermiculite 114
Formal Oxidation Numbers 121
The Geometry of Pauling's Radius Ratio Rule 122
Bragg's Law and X-Ray Diffraction in Layer Silicates 126
Osmotic Model of Interlayer Swelling Pressure 126
Experimental Estimates of Interlayer Swelling Pressure 128
Chapter 4: Ion Exchange 134
Introduction 134
The Discovery of Ion Exchange 135
Ion Exchange Experiments 136
Preparing Clay Saturated with a Single Cation 136
Measuring Cation Exchange Capacity 137
Measuring the Cation Exchange Isotherm 137
Selectivity Coefficients and the Exchange Isotherm 139
Interpreting the Ion Exchange Isotherm 142
The Ion Exchange Isotherm for Symmetric Exchange 143
The Ion Exchange Isotherm for Asymmetric Exchange 144
Effect of Ionic Strength on the Ion Exchange Isotherm 146
Effect of Ion Selectivity on the Ion Exchange Isotherm 148
Other Influences on the Ion Exchange Isotherm 155
Summary 157
Thermodynamic and Conditional Selectivity Coefficients 159
Nonlinear Least Square Fitting of Exchange Isotherms 160
Equivalent Fraction-Dependent Selectivity Coefficient for (Mg2+, Ca2+) Exchange on the Libby Vermiculite 161
Chapter 5: Water Chemistry 168
The Equilibrium Constant 168
Thermodynamic Functions for Chemical Reactions 168
Gibbs Energy of Reaction and the Equilibrium Constant 169
Activity and the Equilibrium Constant 170
Concentrations and Activity 170
Ionic Strength I 171
Empirical Ion Activity Coefficient Expressions 171
Modeling Water Chemistry 173
Simple Equilibrium Systems 173
Water Chemistry Simulations 187
Modeling the Chemistry of Environmental Samples: Groundwater, Soil Pore Water, and Surface Water 196
Summary 204
ChemEQL Result Data File Format 204
Validating Water Chemistry Simulations 205
Validation Assessment for Examples 5.13 and 5.16 210
Example 5.13: Gypsum Solubility 210
Example 5.16: Gibbsite Solubility 211
Cinnabar Solubility in an Open System Containing the Gas Dihydrogen Sulfide 213
Simultaneous Calcite-Apatite-Pyromorphite Solubility 216
Simultaneous Gibbsite-Variscite Solubility 217
Apatite Solubility as a Function of pH 217
Effect of the Citrate on the Solubility of the Calcium Phosphate Mineral Apatite 218
Effect of the Bacterial Siderophore Desferrioxamine B on the Solubility of the Iron Oxyhydroxide Goethite 220
Chapter 6: Natural Organic Matter and Humic Colloids 226
Introduction 226
Soil Carbon Cycle 226
Carbon Fixation 227
Carbon Mineralization 229
Oxidation of Organic Compounds by Dioxygen 230
Soil Carbon 234
Carbon Turnover Models 234
Soil Carbon Pools 238
Dissolved Organic Carbon 240
Organic Acids 240
Amino Acids 241
Extracellular Enzymes 241
Siderophores 241
Biosurfactants 245
Humic Substances 246
Extraction and Fractionation 246
Elemental Composition 247
Chemical Composition 248
Humic Colloids 262
Summary 263
Hydroxamate and Catecholamide Siderophore Moieties 264
Surface Microlayers 267
Humic Oxygen Content and Titratable Weak Acids 269
Hydrophobic and Hydrophilic Colloids 269
Chapter 7: Acid-Base Chemistry 274
Introduction 274
Principles of Acid-Base Chemistry 275
Dissociation: The Arrhenius Model of Acid-Base Reactions 275
Hydrogen Ion Transfer: the Brønsted-Lowery Model of Acid-Base Reactions 276
Conjugate Acids and Bases 276
Defining Acid and Base Strength 277
Water Reference Level 278
The Aqueous Carbon Dioxide Reference Level 279
Sources of Environmental Acidity and Basicity 280
Chemical Weathering of Rocks and Minerals 282
Silicate Rocks 282
Carbonate Rocks 284
Sulfide Minerals 285
Evaporite Rocks 286
Atmospheric Gases 286
Carbon Dioxide: Above Ground 286
Carbon Dioxide: Below Ground 288
Sulfur Oxides 288
Nitrogen Oxides 290
Ammonia-Based Fertilizers and Biomass Harvesting 293
Charge Balancing in Plant Tissue and the Rhizosphere 295
Water Alkalinity 297
Carbonate Alkalinity 298
Silicate Alkalinity 298
The Methyl Orange End-Point 299
Mineral Acidity 300
Mechanical Properties of Clay Colloids and Soil Sodicity 300
Clay Plasticity and Soil Mechanical Properties 301
Clay Content and Granular Particle Contacts 303
Sodicity 305
Sodium-Ion Accumulation on the Clay Exchange Complex: ESP 306
Pore Water Electrical Conductivity ECW 309
Extreme Alkalinity: Soil pH> 8.4
Predicting Changes in Pore Water SAR 313
Exchangeable Acidity 315
Exchangeable Calcium and Soil Alkalinity 315
Gibbsite Solubility 315
The Role of Asymmetric (Al3+,Ca2+) Exchange 317
Neutralizing Exchangeable Soil Acidity 318
Summary 319
Buffer Index 320
Converting Mass Fraction to Sum-of-Oxides Composition 322
Saturation Effect: Atmospheric Conversion of Sulfur Trioxide to Sulfuric Acid 322
Bicarbonate and Carbonate Reference Levels 323
Calculating the pH of a Sodium Carbonate Solution 325
Calculating the Aqueous Carbon Dioxide Concentration in a Weak Base Solution 326
Ion Exchange Isotherm for Asymmetric (Ca2+, Al3+) Exchange 327
The Effect of (Na+, Ca2+) Exchange on the Critical Coagulation Concentration of Montmorillonite 330
Predicting Changes in SAR by Water Chemistry Simulation 333
Chapter 8: Redox Chemistry 338
Introduction 338
Redox Principles 339
Formal Oxidation Numbers 339
Balancing Reduction Half Reactions 341
Reduction Half Reactions and Electrochemical Cells 343
The Nernst Equation 344
Interpreting Redox Stability Diagrams 348
Environmental Redox Conditions 348
Measuring Environmental Reduction Potentials Using Platinum Oxidation-Reduction Electrodes 350
Pourbaix Stability Diagrams: Preparation and Interpretation 351
Water Stability Limits 351
The Solute-Solute Reduction Boundary 353
The Solute-Solute Hydrolysis Boundary 355
The Solute-Precipitate Boundary 356
The Solute-Precipitate Reduction Boundary 357
The Precipitate-Precipitate Reduction Boundary 358
Simple Rules for Interpreting Pourbaix Diagrams 360
Microbial Respiration and Electron Transport Chains 362
Catabolism and Respiration 364
Electron Transport Chains 366
Environmental Redox Conditions and Microbial Respiration 377
Summary 378
Assigning Formal Oxidation Numbers 379
Converting (pe, pH) Redox Coordinates into (EH, pH) Coordinates 380
Limitations in the Measurement of the Environmental Reduction Potential Using Platinum ORP Electrodes 382
Chapter 9: Adsorption and Surface Chemistry 388
Introduction 388
Mineral and Organic Colloids as Environmental Adsorbents 389
The Adsorption Isotherm Experiment 391
Hydrophobic and Hydrophilic Colloids 396
Interpreting the Adsorption Isotherm Experiment 396
The Langmuir Adsorption Model 397
Ion Exchange Adsorption Isotherms 399
Linear Adsorption or Partitioning Model 400
Variable-Charge Mineral Surfaces 404
The Adsorption Envelope Experiment: Measuring pH-Dependent Ion Adsorption 405
Adsorption Edges 406
Measuring pH-Dependent Surface Charge 407
Proton Surface Charge Sites 408
Valence Bond Model of Proton Sites 409
Interpreting pH-Dependent Ion Adsorption Experiments 411
Surface Complexes 412
Summary 416
Particle Sedimentation Rates in Water: Stokes's Law 417
Linear Langmuir Expression 418
Hydrolysis Model of Proton Sites 419
Chapter 10: Risk Assessment 426
Introduction 426
The Federal Risk Assessment Paradigm 428
Risk Assessment 428
Risk Management and Mitigation 428
Dose-Response Assessment 428
Dose-Response Distributions 429
The No-Threshold One-Hit Model 430
Low-Dose Extrapolation of Noncarcinogenic Response Functions 431
Estimating the Steady-State Body Burden 432
Reference Dose RfD 433
Low-Dose Extrapolation of Carcinogenic Response Functions 433
Exposure Pathway Assessment 436
Receptors 436
Exposure Routes 437
Exposure Points 439
Fate and Transport 440
Primary and Secondary Sources 441
Exposure Assessment 442
Intake Estimates 442
Averaging Time 442
Exposure Factors 444
Risk Characterization 445
The Incremental Excess Lifetime Cancer Risk 445
The Hazard Quotient 447
Exposure Mitigation 448
Summary 451
Chemical- and Site-Specific Factors that May Affect Contaminant Transport by Surface Water 452
Chemical- and Site-Specific Factors that May Affect Contaminant Transport by Groundwater 453
Chemical- and Site-Specific Factors that May Affect Contaminant Transport Involving Soils or Sediments 454
Chemical- and Site-Specific Factors that May Affect Contaminant Transport Involving Air and Biota 455
Water Ingestion Equation 455
Soil Ingestion Equation 458
Food Ingestion Equation 459
Air Inhalation Equation 459
Hazard Index-Cumulative Noncarcinogenic Risk 460
Cumulative Target Risk-Cumulative carcinogenic Risk 461
References 466
Index 480