Title Details

Peter Crowley Ryan is Professor of Geology and Environmental Studies at Middlebury College where he teaches courses in environmental geochemistry, hydrology, sedimentary geology and interdisciplinary environmental science. He received a Ph.D. in geology at Dartmouth College, an M.S. in geology from the University of Montana and a B.A. in earth sciences from Dartmouth College. He has served as Director of the Program in Environmental Studies and as Chair of the Department of Geology at Middlebury College. His research interests fall into two main areas: (1) understanding the geological and mineralogical controls on trace-element speciation, particularly the occurrence and mobility of arsenic and uranium in bedrock aquifers; and (2) the temporal evolution of marine terrace soils in the tropics, with emphasis on mechanisms and rates of mineralogical reactions, nutrient cycling and application of soil geochemical analysis to correlation and geological interpretation.

Acknowledgements xii

About the Companion Website xiii

1 Background and Basic Chemical Principles: Elements, Ions, Bonding, Reactions 1

1.1 An overview of environmental geochemistry – history, Scope, Questions, Approaches, challenges for the future 1

1.2 The naturally occurring elements – origins and abundances 2

1.3 Atoms and isotopes: a brief review 6

1.4 Measuring concentrations 8

1.4.1 Mass-based concentrations 8

1.4.2 Molar concentrations 9

1.4.3 Concentrations of gases 10

1.4.4 Notes on precision and accuracy, significant figures and scientific notation 10

1.5 Periodic table 11

1.6 Ions, Molecules, Valence, Bonding, chemical reactions 14

1.6.1 Ionic bond strength 14

1.6.2 Covalent bonds 16

1.6.3 Electronegativity 17

1.6.4 Metallic bonds, hydrogen bonds and van der Waals forces 18

1.7 Acid–base equilibria, pH, K values 19

1.8 Fundamentals of redox chemistry and chemical reactions 21

1.9 Chemical reactions 23

1.10 Equilibrium, thermodynamics and driving forces for reactions: systems, gibbs energies, enthalpy and heat capacity, Entropy, volume 23

1.10.1 Systems, Species, phases and components 24

1.10.2 First law of thermodynamics 26

1.10.3 Second law of thermodynamics 27

1.10.4 Enthalpy 27

1.10.5 Heat capacity 29

1.10.6 Gibbs free energy 30

1.10.7 Gibbs free energy and the equilibrium constant 31

1.11 Kinetics and reaction rates: distance from equilibrium, activation energy, metastability 33

1.11.1 Reaction rate, reaction order 34

1.11.2 Temperature and the Arrhenius equation 36

Review questions 37

References 37

2 Surficial and Environmental Mineralogy 39

2.1 Introduction to minerals and unit cells 40

2.2 Ion coordination, Pauling’s rules and ionic substitution 42

2.2.1 Coordination and radius ratio 42

2.2.2 Bond-strength considerations 45

2.2.3 Pauling’s and Goldschmidt’s rules of ionic solids 45

2.3 Silicates 48

2.3.1 Nesosilicates 49

2.3.2 Inosilicates 50

2.3.3 Phyllosilicates 52

2.3.4 Tectosilicates 58

2.4 Clay minerals (T–O minerals, T–O–T minerals, interstratified clays) 58

2.4.1 Smectite 59

2.4.2 Smectites with tetrahedrally derived layer charge 60

2.4.3 Smectites with octahedrally derived layer charge 60

2.4.4 Vermiculite 62

2.4.5 Illite 62

2.4.6 Chlorite and Berthierine 63

2.4.7 Kaolin (kaolinite and halloysite) 63

2.4.8 Interstratified clay minerals 64

2.4.9 Trace metals and metalloids in clay minerals 64

2.5 Crystal chemistry of adsorption and cation exchange 64

2.5.1 Cation exchange 66

2.5.2 Double-layer complexes 68

2.6 Low-temperature non-silicate minerals: carbonates, oxides and hydroxides, Sulphides, Sulfates, salts 70

2.6.1 Carbonates 70

2.6.2 Oxides and hydroxides 71

2.6.3 Sulfides and sulfates 72

2.6.4 Halide and nitrate salts 74

2.7 Mineral growth and dissolution 74

2.8 Biomineralization 78

Review questions 79

References 80

3 Organic Compounds in the Environment 82

3.1 Introduction to organic chemistry: chains and rings, Single, Double, and triple bonds, functional groups, classes of organic compounds, organic nomenclature 82

3.1.1 Definition of organic compounds 82

3.1.2 Hybridization of carbon atoms in organic compounds 83

3.1.3 Alkanes 84

3.1.4 Alkenes 86

3.1.5 Functional groups 86

3.1.6 Aromatic hydrocarbons and related compounds 88

3.1.7 Nitrogen phosphorus and sulfur in organic compounds 92

3.1.8 Pharmaceutical compounds 93

3.2 Natural organic compounds at the earth surface 94

3.2.1 Fossil fuels 95

3.3 Fate and transport of organic pollutants, controls on bioavailability, behavior of DNAPLs and LNAPLs, Biodegradation, remediation schemes 96

3.3.1 Solid–liquid–gas phase considerations 96

3.3.2 Solubility considerations 97

3.3.3 Interactions of organic compounds and organisms 98

3.3.4 Adsorption of organic compounds 99

3.3.5 Non-aqueous phase liquids (NAPLs) in the environment 103

3.3.6 Biodegradation 104

3.3.7 Remediation 105

3.4 Summary 106

Questions 106

References 106

4 Aqueous Systems – Controls on Water Chemistry 108

4.1 Introduction to the geochemistry of natural waters 108

4.1.1 Geochemistry and the hydrologic cycle 108

4.2 The structure of water – geometry polarity and consequences 113

4.3 Dissolved versus particulate: examples of solutions and suspensions 114

4.3.1 Dissolved vs. particulate vs. colloidal 115

4.4 Speciation: simple ions, polyatomic ions and aqueous complexes 116

4.5 Controls on the solubility of inorganic elements and ions 117

4.5.1 The ratio of ionic charge: ionic radius and its effect on solubility 119

4.5.2 Reduction–oxidation reactions 120

4.5.3 Half-cell reactions 120

4.5.4 Redox reactions in the environment 122

4.5.5 pH and acid–base consideration 123

4.5.6 Ligands and elemental mobility 124

4.6 Ion activities, ionic strength, TDS 125

4.6.1 Ion activity product 126

4.6.2 Ionic strength 126

4.6.3 Total dissolved solids 126

4.7 Solubility products saturation 127

4.8 Co-precipitation 128

4.9 Behavior of selected elements in aqueous systems 129

4.9.1 Examples of heavy metals and metalloids 129

4.9.2 Eh–pH diagrams 132

4.9.3 Silicon in solutions 136

4.10 Effect of adsorption and ion exchange on water chemistry 137

4.10.1 Ionic potential, hydration radius and adsorption 138

4.10.2 Law of mass action and adsorption 138

4.10.3 Adsorption edges 140

4.10.4 Adsorption isotherms 142

4.11 Other graphical representations of aqueous systems: piper and stiff diagrams 143

4.12 Summary 146

Questions 147

References 147

5 Carbonate Geochemistry and the Carbon Cycle 149

5.1 Carbonate geochemistry: inorganic carbon in the atmosphere and hydrosphere 149

5.1.1 Atmospheric CO₂, carbonate species and the pH of rain 150

5.1.2 Speciation in the carbonate system as a function of pH 151

5.1.3 Alkalinity 152

5.1.4 Carbonate solubility and saturation 155

5.1.5 The effect of CO₂ partial pressure on stability of carbonate minerals 157

5.1.6 The effect of mineral composition on stability of carbonate minerals 157

5.2 The carbon cycle 158

5.2.1 Oxidation states of carbon 158

5.2.2 Global-scale reservoirs and fluxes of carbon 159

5.2.3 Fixation of carbon into the crust 161

5.2.4 Rates of flux to and from the crust 164

5.2.5 The ocean reservoir 166

5.2.6 Fixation of C into oceans 166

5.2.7 Long-term viability of oceans as C sink 168

5.2.8 The atmospheric reservoir 171

5.2.9 Sequestration 174

Questions 175

6 Biogeochemical Cycles –N, P, S 177

6.1 The nitrogen cycle 180

6.1.1 Nitrogen valence, nitrogen species 181

6.1.2 Processes operating within the nitrogen cycle 182

6.1.3 Global scale reservoirs and fluxes of nitrogen 184

6.1.4 Human perturbation of the nitrogen cycle and resulting environmental impacts 186

6.2 The phosphorus cycle 190

6.2.1 P cycling in soils 191

6.2.2 The global phosphorus cycle 193

6.2.3 Phosphorus and eutrophication 194

6.3 Comparison of N and P 195

6.4 The sulfur cycle 196

6.4.1 Sulfur valence, sulphur species 196

6.4.2 The global S cycle 197

6.4.3 The marine S cycle 198

6.4.4 Soils and biota 200

6.4.5 Atmosphere 200

6.4.6 River flux 201

6.5 Integrating the C, N, P and S cycles 202

Questions 203

References 203

7 The Global Atmosphere: Composition, Evolution and Anthropogenic Change 206

7.1 Atmospheric structure, circulation and composition 206

7.1.1 Structure and layering of the atmosphere 207

7.1.2 Geological record of atmospheric composition 208

7.1.3 Climate proxies 209

7.1.4 Orbital control on C 210

7.1.5 Composition of the current atmosphere 213

7.1.6 Air circulation 214

7.2 Evaporation, Distillation, CO₂ dissolution and the composition of natural precipitation 218

7.3 The electromagnetic spectrum, greenhouse gases and climate 219

7.3.1 Electromagnetic spectrum 219

7.3.2 Re-radiation from earth surface 219

7.3.3 Greenhouse effect and heat trapping 222

7.4 Greenhouse gases: structures, Sources, sinks and effects on climate 223

7.4.1 Molecular structures and vibrations of greenhouse gases 223

7.4.2 Greenhouse gases, radiative forcing, GWPs 224

7.4.3 Global warming 227

Questions 228

References 228

8 Urban and Regional Air Pollution 230

8.1 Oxygen and its impact on atmospheric chemistry 231

8.2 Free radicals 232

8.3 Sulfur dioxide 234

8.4 Nitrogen oxides 237

8.5 Carbon monoxide 238

8.6 Particulate matter 240

8.7 Lead (Pb) 242

8.8 Hydrocarbons and air quality: tropospheric ozone and photochemical smog 242

8.9 Stratospheric ozone chemistry 245

8.10 Sulfur and nitrogen gases and acid deposition 249

8.11 Trace elements in atmospheric deposition: organochlorine pesticides, mercury and other trace elements 252

8.11.1 Pesticides in air 252

8.11.2 Hg in air 253

8.11.3 As, Cd and Ni 254

Questions 255

References 256

9 Chemical Weathering and Soils 258

9.1 Primary minerals, mineral instability, chemical weathering mechanisms and reactions, soil-forming factors, and products of chemical weathering 258

9.1.1 Goldich stability sequence 259

9.1.2 Weathering rates 260

9.1.3 Chemical weathering 261

9.1.4 Consequences of chemical weathering: dissolved species and secondary minerals 264

9.1.5 Geochemical quantification of elemental mobility in soil 265

9.1.6 Quantifying chemical weathering: CIA 267

9.1.7 Soil profile 268

9.1.8 Soil-forming factors 268

9.1.9 Soil classification – soil orders and geochemical controls 273

9.2 Secondary minerals, controls on their formation, and mineral stability diagrams 275

9.2.1 Factors controlling soil mineralogy 275

9.2.2 Mineral stability diagrams 276

9.3 Soils and the geochemistry of paleoclimate analysis 281

9.4 Effects of acid deposition on soils and aquatic ecosystems 282

9.4.1 Increased solubility of Al in acidic soil solution 283

9.4.2 Displacement of adsorbed nutrient cations 284

9.4.3 Leaching of base cations enhanced by increased NO₃ and SO₄ 285

9.4.4 Decrease of soil buffering capacity and base saturation 286

9.4.5 Acid deposition and heavy metals 287

9.5 Soils and plant nutrients 287

9.6 Saline and sodic soils 289

9.7 Toxic metals and metalloids 290

9.8 Organic soil pollutants and remediation (fuels, Insecticides, solvents) 294

Questions 295

References 296

10 Stable Isotope Geochemistry 299

10.1 Stable isotopes – mass differences and the concept of fractionation 299

10.2 Delta (δ) notation 302

10.3 Fractionation: vibrational frequencies, temperature dependence 304

10.3.1 Stable isotopes and chemical bond strength 305

10.3.2 Temperature-dependent stable-isotope fractionation 305

10.3.3 Equilibrium and non-equilibrium isotope fractionation 307

10.4 δ¹⁸O and δD 309

10.4.1 Paleotemperature analysis using oxygen and hydrogen isotopes 314

10.4.2 Oxygen and hydrogen isotopes as tracers in the hydrologic cycle 314

10.4.3 Application of oxygen and hydrogen isotopes to paleosol climate records 316

10.5 δ¹⁵N 316

10.6 δ¹³C 318

10.6.1 Carbon isotope analysis of paleoenvironment 320

10.6.2 Carbon isotopes in hydrology and chemical weathering 321

10.7 δ³⁴S 321

10.7.1 Fraction of sulphur isotopes 322

10.8 Non-traditional stable isotopes 324

10.8.1 δ^65/63Cu 325

10.8.2 δ^56/54Fe 326

10.8.3 δ^202/198Hg 326

10.8.4 δ²⁶Mg and δ^44/42Ca 328

10.8.5 δ^37/35Cl 330

10.9 Summary 330

Questions 331

11 Radioactive and Radiogenic Isotope Geochemistry 335

11.1 Radioactive decay 335

11.1.1 Decay mechanisms and products 336

11.1.2 Half-lives, decay rates and decay constants 337

11.2 Radionuclides as tracers in environmental geochemistry 341

11.2.1 ²⁰⁶Pb/²⁰⁷Pb 341

11.2.2 ⁸⁷Sr/⁸⁶Sr 342

11.3 Radionuclides as environmental contaminants 342

11.3.1 Controls on U, Th and their decay products 342

11.3.2 Refined uranium ores and associated nuclear wastes 346

11.3.3 Geological disposal of high-level radioactive wastes 349

11.4 Geochronology 350

11.4.1 ¹⁴C, cosmogenic radionuclides and earth-surface dating techniques 350

11.4.2 Common radioactive decay methods of dating sediments and minerals 359

11.4.3 ²³⁴U/²³⁸U and ²³⁴U disequilibrium 364

Questions 367

References 367

Appendix I Case Study on the Relationship of Volatile Organic Compounds (VOCs), Microbial Activity, Redox Reactions, Remediation and Arsenic Mobility in Groundwater 371

I.1 Site information, contaminant delineation 371

I.2 Remediation efforts 372

I.3 Sources of PCE and As 374

I.4 Mobilization of arsenic 374

References 377

Appendix II Instrumental Analysis 378

II.1 Analysis of minerals and crystal chemistry 378

II.1.1 Electron microscopy (SEM, TEM and many other acronyms) 378

II.1.2 X-ray diffraction 379

II.1.3 FTIR 382

II.1.4 Elements in solution by ICP-AES, ICP-MS, AAS 384

II.1.5 XRF 385

II.1.6 X-ray absorption spectroscopy (XAS) techniques (EXAFS, XANES) 385

II.1.7 Isotopic analysis: mass spectrometry 387

II.1.8 Chromatography 389

Appendix III Table of Thermodynamic Data of Selected Species at 1 Atm and 25^°C 390

Index 394

“A useful acquisition for libraries serving undergraduate and graduate earth science programs.  Summing Up: Recommended. Upper-division undergraduates, graduate students, and faculty.”  (Choice, 1 December 2014)