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Pennsylvania State University, 415 Agricultural Sciences and Industries Building, University Park, PA 16802
(henrylin{at}psu.edu)
Edited by J.I. Drever. Treatise on Geochemistry. Vol. 5. Elsevier, 525 B Street, Suite 1900, San Diego, CA 92101-2004. 626 p. $89.00 hardbound. ISBN 0080437516.
At first, I was not sure why I wanted to carry this nicely bound, heavy volume. But its intriguing title relevant to hydropedology and an appealing cover image that shows beautifully water-rock-soil-biology interactions at Yellowstone Falls attracted me to read it. Soon I found the value of this book: a state-of-the-knowledge of aquatic geochemistry and its relation to weathering and soils; a comprehensive summary of the history, methodologies and tools, and fascinating developments of near-surface geochemistry; and modern applications of geochemical cycles, including water quality, the global carbon cycle, the importance of weathering and erosion in controlling global changes, geomicrobiology, human and land use impacts on the chemistry of surface and ground water, scale transfer from laboratory results (of chemical mass balance, equilibra, and kinetics) to the field, and the use of isotopes to determine flow rates and subsurface processes. This is Volume 5 of an impressive 10-volume series entitled Treatise on Geochemistry that covers nearly all aspects of geochemistry, ranging from the chemistry of the solar system to environmental geochemistry.
The Volume Editor, James Drever of the University of Wyoming, a former president of the Geochemical Society, has assembled a distinguished group of international scholars to write a series of chapters that together summarize the field. He has provided an excellent and concise overview of the volume in the introduction. His introductory essay "glues" together nicely the 18 chapters of the volume, and he gives readers an integrated perspective of the topics covered and highlights modern geochemistry developments. The Executive Editors' Foreword by H.D. Holland of Harvard University and K.K. Turekian of Yale University provides the "big picture" of the 10-volume series-how it came about and why it was needed. Thus, it gives readers the right perspective regarding the vast knowledge base of geochemistry. The Treatise on Geochemistry is clearly not meant to be an encyclopedia or a handbook; instead, emphasis has been placed on integrating individual chapters and several volumes.
Interestingly, the first chapter of this book is on soil formation and was written by Ron Amundson of the University of California at Berkeley; the last chapter is on Palesols (fossil soils) by Greg Retallack of the University of Oregon. These two chapters seem to close the loop of various (bio)geochemical processes discussed in this volume, although the book's main theme is centered on water-rock interactions. These front and end chapters of the volume have a strong focus on the role of soils in the global C cycle, suggesting the critical role of soil C in accounting for the "missing sink" of the global carbon budget. While the C cycle is discussed in detail in Volume 8 (Biogeochemistry) of the Treatise on Geochemistry, these two chapters clearly demonstrate the growing interest in soils among scientists outside agriculture, particularly geochemists, hydrogeologists, and ecologists. These two chapters rightly bring pedology back to its multidisciplinary origins. Chapter 1 lays down a good foundation of soil-forming theory, soil geography, mass-balance calculations, and mechanistic modeling of soil C processes. Chapter 18 describes the interesting record of past soils and global change through the long history of our planet with alternating greenhouse and icehouse times.
The sequence of the remaining chapters of the volume is a bit confusing to me, although one can tell that it goes from fundamental geochemical principles (Chapters 2 to 6) to the chemistry of surface water bodies (Chapters 7 to 9 and 13), important chemical tracers (Chapters 10 to 12), ground water geochemistry (Chapters 14 to 15), and deep fluids in the continents (Chapters 16 and 17). I found the Volume Editor's introduction a more meaningful way to connect various chapters in this volume, in which he summarizes (1) mass balance as a means of constraining chemical reactions, (2) chemical equilibra and kinetics, (3) chemistry of deep subsurface waters on the continents, (4) global fluxes and atmospheric carbon dioxide, and (5) biological processes.
Chapter 2 by D. Nordstrom outlines the main concepts and key developments in geochemical modeling for low-temperature environments. It starts with brief model concepts and definitions and follows with a short history of geochemical models, a discussion of databases, various codes that embody models, and recent examples of how these codes have been used in studying water-rock interactions. Like modeling in many other disciplines, sophistication for geochemical codes does not imply a parallel advance in the understanding of geochemical processes. The sophistication of software has outdistanced our capacity to evaluate the software over a range of conditions and outdistanced our ability to obtain the field data to constrain and test the software.
Chapter 3 by S. Brantley summarizes the general techniques of measuring dissolution and precipitation rates of rock-forming silicates and carbonates and discusses exclusively seven factors that cause the discrepancy between laboratory- and field-determined rates. While hydrological and biological factors are acknowledged as important factors, they were not included in this chapter. Quantitative extrapolation from laboratory samples to field systems remains difficult, and reaction transport modeling faces challenges in field applications, where dissolution-precipitation may be rate-limited by transport.
The short Chapter 4 by O. Bricker, B. Jones, and C. Bowser reviews the mass-balance approach to interpret weathering reactions in watershed systems, including methods of mass balance, mass-balance modeling, and the discrepancy of weathering rates determined in the field vs. in the laboratory. The concept of mass balance is one of the major modern approaches to understanding the chemistry of surface and ground water. Thus, to a large extent, many chapters of this book deal with issues related to this idea and its various uses.
The focus of Chapter 5 by A. White is on natural weathering rates of silicate minerals, which are equivalent to chemical fluxes in natural systems that span spatial-temporal scales from the microscopic mineral surface to the soil profile, small catchment, large river basin, continent, and globe. This complements well several other chapters in the volume that deal in greater detail with some of the specific weathering environments, e.g., soils, glacial environments, watersheds, and river systems. This chapter reviews the chemical, physical, and hydrologic processes that control silicate mineral natural weathering rates and summarizes the key factors involved. I found Chapter 5 particularly relevant to watershed hydropedologic studies. There is a fundamental need for connecting dissolution rates in lab experiments and the weathering rates in the field.
Chapter 6 by E. Berner, R. Berner, and K. Moulton elucidates the growing topic of biological factors in accelerated mineral weathering. Field studies evaluating the effects of higher plants on weathering are reviewed, and the key role plant evolution has on silicate rock weathering is linked to global cooling and the development of glaciers in the Carboniferous and Permian, thereby demonstrating the control of atmospheric carbon dioxide by plants over geological time. As geomicrobiology is currently the fastest-growing subfield of geochemistry, the exclusion of microbes in this chapter and the lack of a stand-alone chapter in this volume on the effects of microbiology on weathering is a weak aspect of this state-of-the-science book.
Chapters 7 to 9 and 13 cover the chemistry of various surface water bodies in relation to geochemical weathering, including glacial and proglacial environments (Chapter 7), rivers (Chapters 8 and 9), and saline lakes (Chapter 13). Chapter 7 integrates the ongoing research of geochemical weathering in largely frozen regions, and documents the factors leading to chemical erosion rates in glaciated terrains that are comparable to those of temperate catchments because of their unique hydrology. Chapter 8 covers the distribution of riverine major ions, C species, and silica over the continents, and the major factors that control their global distribution and yields (i.e., lithology, climate, and human factors). Chapter 9 reviews the recent literature on trace elements in rivers, in particular by incorporating the results from measurements of inductively coupled plasma mass spectrometry (ICP-MS). Chapter 13 summarizes the geochemistry of saline lakes throughout the world. After a theoretical background of the evolution of closed-basin waters, five field examples are selected to represent the major water types.
Chapters 10 to 12 introduce both weathering and hydrologic studies and are applicable to all components of the hydrologic cycle. The inclusion of dissolved organic matter and isotopic species represents a major advancement in modern geochemistry. These three chapters clearly indicate that the integration of chemical and isotopic data with complex hydrologic and geochemical models constitutes a frontier of hydrologic and (bio)geochemical research. Chapter 10 provides an inventory of dissolved organic matter in various freshwaters. After a brief review of the major areas of research since the early 1950s, this chapter is devoted extensively to a synthesis and analysis of the published literature on the chemical properties of organic matter in natural waters. Chapter 11 provides an overview of the use of naturally occurring stable isotopes to track water paths and reaction paths in hydrosystems. After describing water isotopes (H and O), solute isotopes of C, N, and S are emphasized for tracing the relative contributions of potential solute sources to surface and ground water. Chapter 12 is organized into three general areas in which radiogenic isotopes have the most significant contributions to the understanding of weathering and hydrology, i.e., identification of mineral dissolution reactions, differentiation of atmospheric- from weathering-derived cations in ecosystems, and tracing hydrologic flow paths and subsurface mixing.
Chapter 14 is an introduction to the principles of mass balance, equilibrium chemistry, and microbiology as applied to ground water geochemistry in a variety of geologic settings. It also reviews equilibrium and kinetic frameworks for documenting the spatial and temporal distribution of redox processes in ground water systems. It also gives a brief discussion on petroleum hydrocarbon and chlorinated solvent contamination in aquifers. Chapter 15 is another chapter particularly relevant to hydropedology and subsurface hydrology. After describing the nature of ground water flow systems and solute transport mechanisms in subsurface water, this chapter summarizes various ground water age tracers at the vadose zone, local, aquifer, and regional scales. Because measurement of certain geochemical constituents in water can define residence times and fluxes in subsurface systems, the authors suggest that the interpretation of the hydrogeochemical system, with adequate attention to issues of transport and mixing, will yield major advances for both geochemistry and quantitative hydrogeology.
Chapters 16 to 17 are sister chapters dealing with deep fluids in the continents and the interrelationships between hydrogeology and geochemistry. Chapter 16 focuses on sedimentary basins in the continental and transitional continental oceanic crust, with an emphasis on water below the zone of shallow meteoric ground water circulation and on the main processes responsible for the modifications of the chemical and isotopic compositions of these waters. Chapter 17 focuses on crystalline rocks, with a review of chemical and isotopic composition of ground water found in these rocks and their origin and evolution, followed by some examples from underground research sites found in crystalline environments.
A carefully listed subject index at the end of this book may come handy when searching for a specific topic in this large, compiled volume. In the index, a major discussion page is in bold and figures and tables are suffixed by f and t after page numbers. Numerous illustrative figures and tables throughout this book, mostly reproduced from published works, certainly make the reading of this highly technical volume more understandable and memorable. Many equations are also present throughout the book, suggesting the need of quantitative geochemistry.
I highly recommend this book to researchers and students who are serious about the latest developments in geochemistry, watershed hydrology, and the earth's Critical Zone. While this book is not designed to be a textbook, general readers may still find it interesting and informative to read, particularly for those who seek to bridge the disciplines among geochemistry, biogeochemistry, hydrogeology, hydropedology, pedology, soil science, hydrology, and biology.
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