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Contents

Authors x

Preface to the Second Edition xii

Preface to the First Edition xiii

Part One: Basic Concepts for Earth System Science 1

1 Introduction: Biogeochemical Cycles as Fundamental Constructs for Studying

Earth System Science and Global Change 3

1.1 Introduction 3

1.2 History 5

1.3 Evidence for the Coupled Nature of the Earth System 6

1.4 Philosophy of Using the Cycle Approach to Describe Natural Systems on Earth 9

1.5 Reservoir Models and Cycles - Some Definitions 9

1.6 The Philosophy of Integration as a Basis for Understanding the Earth System 11

1.7 The Limitations and Challenges of Understanding Earth Systems 12 References 12

2 The Origin and Early Evolution of the Earth 14

2.1 Introduction 14

2.2 Pre-Solar Evolution: The Origin of the Elements 14

2.3 The Origin of the Solar System 19

2.4 Condensation 20

2.5 Accretion of the Planets 23

2.6 Early Evolution of the Earth 25

2.7 Earth and the Development of Life 27 References 28

3 Evolution and the Biosphere 29

3.1 The Origin of Life on Earth 29

3.2 The Machinery of Life 31

3.3 Evolutionary Mechanisms 35

3.4 The Diversity of Living Organisms 42

3.5 The Ecological Organization of the Living World 46

3.6 The Impact of Life on Biogeochemical Cycles 48

3.7 How Biogeochemical Cycles Affect Life 53 References 55 Appendix 57

4 Modeling Biogeochemical Cycles 62

4.1 Introductory Remarks 62

4.2 Time Scales and Single Reservoir Systems 62

4.3 Coupled Reservoirs 67

4.4 Fluxes Influenced by the Receiving Reservoir 73

4.5 Coupled Cycles 73

4.6 Forward and Inverse Modeling 74

4.7 High-Resolution Models 74

4.8 Transport Processes 76

4.9 Time Scales of Mixing in the Atmosphere and Oceans 81 Questions 83 References 83

5 Equilibrium, Rate, and Natural Systems 85

5.1 Introduction 85

5.2 Thermodynamics 85

5.3 Oxidation and Reduction 91

5.4 Chemical Kinetics 96

5.5 Non-Equilibrium Natural Systems 101

5.6 Summary 103 Questions 103 References 104

Part Two: Properties of and Transfers between the Key Reservoirs 107

6 Water and the Hydrosphere 109

6.1 Introduction 109

6.2 Global Water Balance 112

6.3 Hydrologic Variability 119

6.4 Water and Climate 124

6.5 Water and Biogeochemical Cycles 127

6.6 Water and the Tectonic Cycles 128

6.7 Anthropogenic Influences 128

6.8 Conclusion 129 References 130

7 The Atmosphere 132

7.1 Definition 132

7.2 The Vertical Structure of the Atmosphere 133

7.3 Vertical Motions, Relative Humidity, and Clouds 136

7.4 The Ozone Layer and the Stratosphere 137

7.5 Horizontal Motions, Atmospheric Transport, and Dispersion 138

7.6 Composition 142

7.7 Atmospheric Water and Cloud Microphysics 144

7.8 Trace Atmospheric Constituents 146

7.9 Chemical Interactions of Trace Atmospheric Constituents 150

7.10 Physical Transformations of Trace Substances in the Atmosphere 152

7.11 Influence of Atmospheric Composition on Climate 153

7.12 Chemical Processes and Exchanges at the Lower and Upper Boundaries of the Atmosphere 156

References 158

8 Soils, Watershed Processes, and Marine Sediments 159

8.1 Introduction 159

8.2 Weathering 160

8.3 Soils 164

8.4 Watershed Processes 177

8.5 Marine Sediments 184

8.6 Soils, Weathering, and Global Biogeochemical Cycles 189 Questions 190 References 190

9 Tectonic Processes and Erosion 195

9.1 Introduction 195

9.2 Erosion, a Capsule Summary 196

9.3 Soils and the Local Weathering Environment 198

9.4 Slope Processes and the Susceptibility of Lithologies to Erosion 202

9.5 Landforms, Tectonism, Sea Level, and Erosion 206

9.6 Erosion in Tectonically Active Areas 212

9.7 Erosion of the Cratons 216

9.8 The Effects of Transients: Continental Ice Sheets and Human Technology 220

9.9 Conclusion 223 Questions 224 References 224

10 The Oceans 230

10.1 What is the Ocean? 230

10.2 Ocean Circulation 232

10.3 Biological Processes 246

10.4 Chemistry of the Oceans 255 Questions 273 References 273

Part Three: Biogeochemical Cycles 279

11 The Global Carbon Cycle 282

11.1 Introduction 282

11.2 The Isotopes of Carbon 283

11.3 The Major Reservoirs of Carbon 284

11.4 Fluxes of Carbon between Reservoirs 297

11.5 Models of the Carbon Cycle 302

11.6 Trends in the Carbon Cycle 303 References 309

12 The Nitrogen Cycle 322

12.1 Introduction 322

12.2 Chemistry 322

12.3 Biological Transformations of Nitrogen 325

12.4 Anthropogenic Nitrogen Fixation 328

12.5 Atmospheric Chemistry 329

12.6 The Global Nitrogen Cycle 331

12.7 Human Impacts 334 Questions 339 References 340

13 The Sulfur Cycle 343

13.1 Introduction 343

13.2 Oxidation States of Sulfur 344

13.3 Sulfur Reservoirs 346

13.4 The Atmospheric Cycle of Sulfur 347

13.5 Hydrospheric Cycle of Sulfur 354 Questions 358 References 358

14 The Phosphorus Cycle 360

14.1 Occurrence of Phosphorus 360

14.2 Sub-Global Phosphorus Transfers 364

14.3 The Global Phosphorus Cycle 367 Questions 373 References 374

15 Trace Metals 377

15.1 Introduction 377

15.2 Metals and Geochemistry 377

15.3 An Overview of Metal Ion Chemistry 381

15.4 Observations on Metals in Natural Systems 402

15.5 Examples of Global Metal Cycling 406

15.6 Summary 414 Questions 415 References 416

Part Four: Integration 419

16 The Acid-Base and Oxidation-Reduction Balances of the Earth 421

16.1 Introduction 421

16.2 A Hierarchy of Acid-Base Balances 422

16.3 Oxidation-Reduction Balances of the Earth System 428

16.4 Conclusion 437 References 437

17 The Coupling of Biogeochemical Cycles and Climate: Forcings, Feedbacks, and Responses 439

17.1 The Climate System 439

17.2 The Dynamics of the Climate System: Forcings, Feedbacks, and Responses 442

17.3 Forcings of Climate 446

17.4 Feedbacks 450

17.5 Climatic States and Responses References

18 Ice Sheets and the Ice-Core Record of Climate Change

18.1 Introduction

18.2 Quaternary Climate Change

18.3 Ice Sheets as Paleoclimate Archives

18.4 Some Lessons in Environmental History References

19 Human Modification of the Earth System: Global Change

19.1 Global Climate Change

19.2 Acid Precipitation

19.3 Food Production

19.4 Stratospheric Ozone Depletion

19.5 Large-Scale Eutrophication

19.6 Oxidative Capacity of the Global Troposphere

19.7 Life and Biogeochemical Cycles

19.8 Conclusion References

Answers to Questions Index

Color Plates are located between pp. 194^-195

Authors

Theodore L Anderson, Department of Atmospheric Sciences, University of Washington, Box 351640, Seattle, WA 98195-1640, USA

Sharon E. Anthony, Evergreen State College, 2700 Evergreen Parkway NW, Olympia, WA 98505, USA

Mark M. Benjamin, Department of Civil and Environmental Engineering, University of Washington, Box 352700, Seattle, WA 981952700, USA

Edward J. Brook, Department of Geology, Department of Environmental Science, Washington State University, Vancouver, WA 98686, USA Donald E. Brownlee, Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195-1580, USA Stephen J. Burges, Department of Civil and Environmental Engineering, University of Washington, Box 352700, Seattle, WA 981952700, USA

Samuel S. Butcher (retired), PO Box 54,

Willow Creek, MT 59760, USA Robert J. Charlson, Department of Atmospheric Sciences, University of Washington, Box 351640, Seattle, WA 98195-1640, USA Kurt M. Cuffey, Department of Geography, 501 McCone Hall, University of California, Berkeley, CA 94720, USA Steven Emerson, School of Oceanography, University of Washington, Box 357940, Seattle, WA 98195-7940, USA Rolf O. Hallberg, Geologiska Institutionen, Stockholms Universitet, S-106 91 Stockholm, Sweden

Patricia C. Henshaw, Northwest Hydraulic Consultants, 16300 Christenson Road, Suite 350, Seattle, WA 98188, USA Kim Holmen, Meteorologiska Institutionen,

Stockholms Universitet, S-106 91 Stockholm, Sweden

Bruce D. Honeyman, Laboratory for Applied and Environmental Radiochemistry, Environmental Science and Engineering Division, Colorado School of Mines, Golden, CO 80401, USA

Michael C. Jacobson, Department of Laboratory Medicine, University of Washington, Box 357110, Seattle, WA 98195-7110, USA Daniel A. Jaffe, University of Washington-Bothell, 22011 26th Avenue SE, Bothell, WA 98021, USA

Richard A. Jahnke, Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, GA 31411, USA Russell E. McDuff, School of Oceanography, University of Washington, Box 357940, Seattle, WA 98195-7940, USA David R. Montgomery, Department of Geological Sciences, University of Washington, Box 351310, Seattle, WA 98195-1310, USA

James W. Murray, School of Oceanography, University of Washington, Box 357940, Seattle, WA 98195-7940, USA Gordon H. Orians, Department of Zoology, University of Washington, Box 351800, Seattle, WA 98195-1800, USA Henning Rodhe, Meteorologiska Institutionen, Stockholms Universitet, S-106 91, Stockholm, Sweden Henri Spaltenstein, University of Lausanne,

Valentine 18,1400 Yverdon, Switzerland James T. Staley, Department of Microbiology, University of Washington, Box 357242, Seattle, WA 98195-7242, USA Robert F. Stallard, US Geological Survey, 3215

Marine Street, Boulder, CO 80303, USA Fiorenzo C. Ugolini, Dipartimento di Scienza del Suolo e Nutrizione della Pianta, Universita degli Studi, Piazzale delle Cascine 15, 50144 Firenze, Italy Gordon V. Wolfe, College of Oceanic and Atmospheric Sciences, 104 Ocean Adminis tration Building, Corvallis, OR 97331-5503, USA

Darlene Zabowski, College of Forest Resources, University of Washington, Box 352100, Seattle, WA 98195-2100, USA

Preface to the Second Edition

Nearly 23 years have passed since Bert Bolin visited the University of Washington and lectured on the question, "Can mankind change the composition of the atmosphere?" and it has been seven years since the first edition of this book appeared. Between the mid 1970s and the early 1990s, the study of biogeochemical cycles emerged as a means to integrate large areas of environmental science. The first edition offered this approach in 1992, and has been used widely as both a text and reference book. Its success, measured in the distribution of over 5000 copies, indicates a widespread appreciation for this integrative approach.

The second edition contains virtually all of the material from the first edition in an updated and edited form. The second edition deliberately extends the integrative approach into three new chapters (16, 17, and 18) on the acid-base and redox balances of the Earth, the coupling of biogeochemical cycles and climate, and the paleorecords of environmental chemistry as deduced from studies of ice cores. This new, fourth section of the book thus gives examples of what we call the Earth system approach. Each of these chapters examines an integrative topic. A new chapter has also been added on water and the hydrologic cycle, which was never specifically treated in the first edition. Along with these new chapters, the original chapters covering the sediments and the pedosphere have been merged into a single chapter because of the strong connection between the two sub jects. Besides the addition of several new coauthors, the list of editors has changed. All of the editors of the first edition - Samuel S. Butcher, Robert J. Charlson, Gordon Orians, and Gordon Wolfe - still appear as co-authors of their respective chapters.

As a consequence of the extension into integration, the title has been changed to Earth System Science: From Biogeochemical Cycles to Global Change. However, despite this new title and new chapters, this book is still about fundamental science; it is not issue oriented. This edition conveys the same philosophy as the earlier one, and the first edition preface (following) still conveys these basic principles around which the book is organized. This edition is more clearly divided into four sections, each with its own introductory summary. The reader is urged to read these summaries in order to gain the perspective that we have attempted to present.

Once again, this book would not have been possible without the contributions of the chapter authors and the very important work of those who prepared the manuscript and illustrations. Much of the typing was done again by Sheila Parker, and Kay Dewar prepared all of the new figures. Michele Kruegel and Monte Lapka provided additional graphics and computer support. A generous gift from the Ford Corporation allowed Michael Jacobson the needed time as a post-doctoral scientist to perform the tasks of chief editor.

Preface to the First Edition

Human activity is affecting the global environment in a profound way. Some of these changes are due to high rates of additions of materials to the environment. Other changes result from losses of habitat and the associated extinctions of species. Many of these human interventions now occur on a scale capable of changing the global biogeochemical cycles upon which life and the Earth's climate depend.

Biogeochemical cycles describe the transformation and movement of chemical substances in a global context. This text is designed for courses intended to present an integrated perspective on biogeochemical cycles. Courses focusing on this subject are offered at advanced undergraduate and graduate levels in many colleges and universities. These courses are usually presented by a person with a specialty in one of the conventional scientific disciplines, supplemented by guest lecturers and readings in other areas. Our goal has been to provide a comprehensive treatment under one cover so that the components are integrated and the need for additional reading is reduced.

The text has its roots in courses on biogeochemical cycles offered at the University of Washington and at the University of Stockholm. The course at the University of Washington was started by two of the authors (Charlson and Murray), and an essential part of the course has been visits by faculty from other disciplines. Many of the chapters in this text spring from materials prepared for those presentations. Some of the authors are former students in this course.

Much of the work important to the study of biogeochemical cycles is done in traditional disciplines - ranging from astronomy to zoology. Many disciplines that have developed fairly recently (such as chemical oceanography)

also play very important roles. This is likely to continue to be the case. Nonetheless, given the nature of biogeochemistry, specialists need to understand what their disciplines can bring to the subject and what are the needs of the other disciplines. To fully comprehend these cycles, a person must also integrate material from several disciplines.

Although our goal has been to be comprehensive, adjustments have had to be made. In managing the compromise between depth of coverage and maintaining a reasonable size for a textbook, many topics are given only limited space. We hope that readers will nevertheless gain an appreciation of the scope of biogeochemical cycles and will be adequately prepared to understand the growing literature in the field.

This book is about fundamental aspects of the science of biogeochemistry. As such, and while it is relevant to the major issues of global change, it is not issue oriented. Not does this book attempt to review all of the research on these topics. It does, however, emphasize fundamental aspects of the physical, chemical, biological, and Earth sciences that are of lasting importance for integrative studies of the Earth.

We assume that our readers have a background in science attainable by completing a university level course in introductory chemistry. We also expect our readers to be involved in one of the disciplines integral to the study of biogeochemical cycles. This includes appropriate subdisciplines of chemistry, biology, and geology, and the sciences that deal with soils, atmospheres, and oceans.

Bert Bolin's visit to the University of Washington in 1976 provided a major stimulus for thinking about biogeochemical cycles at the university. Active work on this text began with a grant from the Rockefeller Foundation to the Institute for Environmental Studies at the University of Washington in 1978. Rockefeller assistance made it possible to bring several scientists to the University of Washington to discuss the role of their specialty in biogeo-chemical cycles. Visits from M. Alexander, P. L. Brezonik, P. J. Crutzen, R. A. Duce, R. O. Hallberg, H. D. Holland, M. L. Jackson, G. E. Likens, F. T. Mackenzie, S. Oden, H. Rodhe, and H. J. Simpson played important roles in shaping our approach to the text.

Several individuals played important roles during the final preparation of the manuscript. Most of the typing was done by Sheila Parker. Drafting of figures was done by Kay Dewar and April Ryan. Last but not least, we owe thanks to the many students at the University of Washington and the University of Stockholm who explored this subject initially without a textbook and then with draft chapters. Their enthusiasm for the subject and their comments and criticism have helped maintain our interest in this manuscript over almost a decade.

Part One

Basic Concepts for Earth System Science

The first part of this book is designed to provide background information that is useful when studying the rest of the text.

Chapter 1 is an introduction to the emerging discipline of Earth system science, covering the history and philosophy of this field. The key to understanding this book and this field is to first realize that the Earth is materially a closed, dynamic system. Because the Earth is not a closed system with respect to energy (i.e., solar radiation), there is a constant cycling of the elements through the various parts of the planet. The movement and transformation of major elements (C, N, S, P, and trace metals) are described individually, using the concept of biogeochemical cycles, which describe the flux of material in and out of the various geospheres (atmosphere, hydrosphere, pedosphere, lithosphere) and the chemical and physical transformations that occur there. Each cycle is studied more or less individually, to allow a way of simplifying the Earth system into a series of smaller, more manageable subsystems. Humans have modified the natural cycling of these elements in a variety of ways, which has lead to chemical and physical changes on Earth on the planetary scale. Using biogeochemical cycles to study the Earth system is one of the major themes of this book.

In order to understand the Earth's character as a planet, it also is helpful to have an understanding of how the elements in our solar system were formed. Chapter 2 starts with the Big Bang theory and continues with how very small grains eventually came together and accreted to form the beginnings of what would eventually become the Earth and other planets, about 4.5 x 109 years ago (4.5 Gyr). The initial processes of the Earth's evolution involved heat generated from radioactive decay and kinetic energy of projectiles impacting the infant planet, causing chemical differentiation of the Earth's interior into a core, mantle, and crust. As we will see in Part Two of the book, the movement of tectonic plates that arose because of this differentiation is necessary for the continuation of life and the biogeochemical cycling of the elements.

Probably the most important characteristic of Earth from a human perspective is its abundant life. It is the only planet we know of that supports a biosphere. The distribution of the elements on the planet were initially controlled by the physical and chemical processes that are described in Chapter 2, but biological processes have been at work in affecting chemical dispersal ever since life first appeared about 3.5 x 109 years ago (3.5 Gyr). In Chapter 3 we investigate the beginnings and evolution of life on Earth, as well as the principal biochemical systems which affect distribution of the elements. The diversity of life on the planet is due to a large number of factors, especially evolutionary agents that can change a population of organisms over time. Evolution of species can alter the ways in which the organisms consume nutrients and energy, which eventually impacts the surrounding environment by altering the elemental cycles. These environmental changes can themselves act as evolutionary agents and affect the genetic code of future generations. It is important for us to have a basic understanding of these biological processes so we understand their effect on the rest of the system, and how the Earth came to be in the state it is in today. Since we, as humans, are also part of the biosphere, we also have a personal interest in how changes to the Earth system affect biological processes on the planet.

Earth System Science ISBN 0-12-379370-X

Copyright i: 2000 Academic Press Limited All rights of reproduction in any form reserved

The ultimate goal in studying Earth systems is to understand the system well enough that we can explain past changes (e.g., why did the ice ages start?) and predict the future of the system (e.g., what will the concentration of atmospheric C02 be in 100 years?). This is possible only if the system can be accurately modeled. Armed with the material in Chapter 4, the reader should be able to develop a feeling for how robust a model prediction presented in the popular press is likely to be. Modeling also provides a way of evaluating what remains poorly understood in a system. Since modeling is such an integral part of studying Earth systems, and biogeochemical cycles in particular, we have included Chapter 4 as a basic modeling primer. The simplest types of models are box models, which describe movement of material between compartments or reservoirs. These models are introduced in this chapter, and used again in Part Three, which covers the individual elemental cycles. This chapter also introduces basic concepts such as residence time, turnover time, response time, and steady-state conditions, which are fundamental in discussing a biogeochemical cycle. It also provides an inventory of the basic information needed about global systems in order to be useful. The recent development of fast computers has dramatically expanded our ability to use the modeling concepts presented in this chapter.

The last chapter in this introductory part covers the basic physical chemistry that is required for using the rest of the book. The main ideas of this chapter relate to basic thermodynamics and kinetics. The thermodynamic conditions determine whether a reaction will occur spontaneously, and if so whether the reaction releases energy and how much of the products are produced compared to the amount of reactants once the system reaches thermodynamic equilibrium. Kinetics, on the other hand, determine how fast a reaction occurs if it is thermodynamically favorable. In the natural environment, we have systems for which reactions would be thermodynamically favorable, but the kinetics are so slow that the system remains in a state of perpetual disequilibrium. A good example of one such system is our atmosphere, as is also covered later in Chapter 7. As part of the presentation of thermodynamics, a section on oxidation-reduction (redox) is included in this chapter. This is meant primarily as preparation for Chapter 16, but it is important to keep this material in mind for the rest of the book as well, since redox reactions are responsible for many of the elemental transitions in biogeochemical cycles.

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