Environmental and Low-Temperature Geochemistry

Environmental and Low-Temperature Geochemistry presents conceptual and quantitative principles of geochemistry in order to foster understanding of natural processes at and near the earth’s surface, as well as anthropogenic impacts and remediation strategies. It provides the reader with principles that allow prediction of concentration, speciation, mobility and reactivity of elements and compounds in soils, waters, sediments and air, drawing attention to both thermodynamic and kinetic controls. The scope includes atmosphere, terrestrial waters, marine waters, soils, sediments and rocks in the shallow crust; the temporal scale is present to Precambrian, and the spatial scale is nanometers to local, regional and global. This second edition of Environmental and Low-Temperature Geochemistry provides the most up-to-date status of the carbon cycle and global warming, including carbon sources, sinks, fluxes and consequences, as well as emerging evidence for (and effects of) ocean acidification. Understanding environmental problems like this requires knowledge based in fundamental principles of equilibrium, kinetics, basic laws of chemistry and physics, empirical evidence, examples from the geological record, and identification of system fluxes and reservoirs that allow us to conceptualize and understand. This edition aims to do that with clear explanations of fundamental principles of geochemistry as well as information and approaches that provide the student or researcher with knowledge to address pressing questions in environmental and geological sciences. New content in this edition includes: Focus Boxes – one every two or three pages – providing case study examples (e.g. methyl isocyanate in Bhopal, origins and health effects of asbestiform minerals), concise explanations of fundamental concepts (e.g. balancing chemical equations, isotopic fractionation, using the Keq to predict reactivity), and useful information (e.g. units of concentration, titrating to determine alkalinity, measuring redox potential of natural waters); Sections on emerging contaminants for which knowledge is rapidly increasing (e.g. perfluorinated compounds, pharmaceuticals and other domestic and industrial chemicals); Greater attention to interrelationships of inorganic, organic and biotic phases and processes; Descriptions, theoretical frameworks and examples of emerging methodologies in geochemistry research, e.g. clumped C-O isotopes to assess seawater temperature over geological time, metal stable isotopes to assess source and transport processes, X-ray absorption spectroscopy to study oxidation state and valence configuration of atoms and molecules; Additional end-of-chapter problems, including more quantitatively based questions. Two detailed case studies that examine fate and transport of organic contaminants (VOCs, PFCs), with data and interpretations presented separately. These examples consider the chemical and mineralogical composition of rocks, soils and waters in the affected system; microbial influence on the decomposition of organic compounds; the effect of reduction-oxidation on transport of Fe, As and Mn; stable isotopes and synthetic compounds as tracers of flow; geological factors that influence flow; and implications for remediation. The interdisciplinary approach and range of topics – including environmental contamination of air, water and soil as well as the processes that affect both natural and anthropogenic systems – make it well-suited for environmental geochemistry courses at universities as well as liberal arts colleges.

Table of Contents:
Preface xiii Acknowledgements xv 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 3 1.3 Atoms, Isotopes, and Valence Electrons 6 1.4 Measuring Concentrations 8 1.5 Periodic Table 12 1.6 Ions, Molecules, Valence, Bonding, Chemical Reactions 13 1.7 Acid–Base Equilibria, PH, K Values 18 1.8 Fundamentals of Redox Chemistry 20 1.9 Chemical Reactions 22 1.10 Equilibrium, Thermodynamics, and Driving Forces for Reactions: Systems, Gibbs Energies, Enthalpy and Heat Capacity, Entropy, Volume 23 1.11 Kinetics and Reaction Rates 31 Questions 35 References 36 2 Surficial and Environmental Mineralogy 39 2.1 Introduction to Minerals and Unit Cells 39 2.2 Ion Coordination, Pauling’s Rules, and Ionic Substitution 41 2.3 Silicates 46 2.4 Clay Minerals (1 : 1 and 2 : 1 Minerals, Interstratified Clays) 55 2.5 Crystal Chemistry of Adsorption and Cation Exchange 60 2.6 Low-Temperature Non-Silicate Minerals: Carbonates, Oxides and Hydroxides, Sulfides, Sulfates, Salts 64 2.7 Mineral Growth and Dissolution 68 2.8 Biomineralization 72 Questions 72 References 73 3 Organic Compounds in the Environment 75 3.1 Introduction to Organic Chemistry: Chains and Rings, Single, Double, and Triple Bonds, Functional Groups, Classes of Organic Compounds, Organic Nomenclature 75 3.2 Natural Organic Compounds at the Earth Surface 87 3.3 Fate and Transport of Organic Pollutants, Controls on Bioavailability, Behavior of DNAPLS and LNAPLS, Biodegradation, Remediation 88 3.4 Summary 96 Questions 96 References 97 4 Aqueous Systems and Water Chemistry 99 4.1 Introduction to the Geochemistry of Natural Waters 99 4.2 The Structure of Water – Implications of Geometry and Polarity 103 4.3 Dissolved versus Particulate, Solutions, and Suspensions 104 4.4 Speciation: Simple Ions, Polyatomic Ions, and Aqueous Complexes 106 4.5 Controls on the Solubility of Inorganic Elements and Ions 106 4.6 Ion Activities, Ionic Strength, TDS 113 4.7 Solubility Products, Saturation 115 4.8 Coprecipitation 116 4.9 Behavior of Selected Elements in Aqueous Systems 117 4.10 Eh–pH Diagrams 119 4.11 Silicon in Solution 123 4.12 Effect of Adsorption and Ion Exchange on Water Chemistry 123 4.13 Other Graphical Representations of Aqueous Systems: Piper and Stiff Diagrams 128 4.14 Summary 131 Questions 131 References 131 5 Carbonate Geochemistry and the Carbon Cycle 133 5.1 Inorganic Carbon in the Atmosphere and Hydrosphere 133 5.2 The Carbon Cycle 141 Questions 154 References 155 6 Biogeochemical Systems and Cycles (N, P, S) 157 6.1 Systems and Elemental Cycles 157 6.2 Elemental Cycles 159 Questions 178 References 178 7 The Global Atmosphere: Composition, Evolution, and Anthropogenic Change 181 7.1 Atmospheric Structure, Circulation, and Composition 181 7.2 Evaporation, Distillation, CO2 Dissolution, and the Composition of Natural Precipitation 190 7.3 The Electromagnetic Spectrum, Greenhouse Gases, and Climate 191 7.4 Greenhouse Gases: Structures, Sources, Sinks, and Effects on Climate 194 Questions 198 References 199 8 Air Quality: Urban and Regional Pollutants 201 8.1 Air Pollution: Definitions and Scope 201 8.2 Oxygen and its Impact on Atmospheric Chemistry 202 8.3 Free Radicals 202 8.4 Sulfur Dioxide 204 8.5 Nitrogen Oxides 206 8.6 Carbon Monoxide 209 8.7 Particulate Matter 209 8.8 Lead (Pb) 210 8.9 Hydrocarbons and Air Quality: Tropospheric Ozone and Photochemical Smog 211 8.10 Stratospheric Ozone Chemistry 213 8.11 Sulfur and Nitrogen and Acid Deposition 215 8.12 Organochlorine Pesticides, Mercury, and Other Trace Constituents in the Atmosphere 219 Questions 222 References 222 9 Chemical Weathering, Soils, and Hydrology 225 9.1 Chemical Weathering of Primary Minerals in Soils 225 9.2 Products and Consequences of Chemical Weathering 231 9.3 Soil Profiles, Nomenclature, Soil-Forming Factors 239 9.4 Soils and the Geochemistry of Paleoclimate Analysis 243 9.5 Effects of Acid Deposition on Soils and Aquatic Ecosystems 245 9.6 Soils and Plant Nutrients 248 9.7 Saline and Sodic Soils 249 9.8 Toxic Metals and Metalloids 251 9.9 Organic Soil Pollutants and Remediation (Fuels, Insecticides, Solvents) 254 Questions 256 References 256 10 Stable Isotope Geochemistry 259 10.1 Stable Isotopes – Mass Differences and the Concept of Fractionation 259 10.2 Delta (δ) Notation 261 10.3 Fractionation: Vibrational Frequencies, Mass, and Temperature Dependence 263 10.4 δ18O and δD 267 10.5 δ15N 273 10.6 δ13C 275 10.7 δ34S 278 10.8 Nontraditional Stable Isotopes 280 10.9 Summary 285 Questions 285 References 286 11 Radioactive and Radiogenic Isotopegeochemistry 289 11.1 Radioactive Decay 289 11.2 Radionuclide Tracers in Environmental Geochemistry 294 11.3 Radionuclides as Environmental Contaminants 295 11.4 Geochronology 301 11.5 Radioactive Decay Methods of Dating Sediments and Minerals 309 Questions 315 References 315 Appendix I Case Study on the Relationships among Volatile Organic Compounds (VOCS), Microbial Activity, Redox Reactions, Remediation, and Arsenic Mobility in Groundwater 319 I.1 Site Information, Contaminant Delineation 319 I.2 Remediation Efforts 320 I.3 Sources of PCE and ARSENIC 320 I.4 Mobilization of Arsenic 322 References 323 Appendix II Case Study of PFOA Migration in a Fractured Rock Aquifer: Using Geochemistry to Decipher Causes of Heterogeneity 325 II.1 Geologic Framework 326 II.2 Inorganic Chemistry of Groundwater 326 II.3 Stable Isotope Compositions of Groundwater 327 II.4 Groundwater Age-Dating 328 II.5 Conceptual Model for the Groundwater System 328 References 329 Appendix III Instrumental Analysis 331 III.1 Analysis of Minerals and Crystal Chemistry 331 III.2 Chemical Analysis of Rocks and Sediments: XRF 337 III.3 Elements or Compounds in Solution 338 III.4 Isotopic Analysis: Mass Spectrometry 339 References 340 Appendix IV Table of Thermodynamic Data of Selected Species at 1 ATM and 25 ∘C 341 References 344 Index 345

About the Author :
PETER RYAN is Professor of Geology and Environmental Studies at Middlebury College where he teaches courses in environmental geochemistry, hydrology, sedimentary geology and interdisciplinary environmental studies. 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 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.