Soil and Environmental Chemistry-2012

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  • Soil and Environmental Chemistry

  • William F. BleamUniversity of Wisconsin, MadisonAMSTERDAM BOSTON HEIDELBERG LONDON NEW YORK OXFORD

    PARIS SAN DIEGO SAN FRANCISCO SINGAPORE SYDNEY TOKYO

    Academic Press is an imprint of ElsevierSoil and EnvironmentalChemistry

  • Academic Press is an imprint of Elsevier

    permission, further information about the Publishers permissions policies and our arrangementswith organizations such as the Copyright Clearance Center and the Copyright Licensing Agency,can be found at our website: www.elsevier.com/permissions.This book and the individual contributions contained in it are protected under copyright by the

    Publisher (other than as may be noted herein).

    NoticesKnowledge and best practice in this field are constantly changing. As new research and

    experience broaden our understanding, changes in research methods, professional practices, ormedical treatment may become necessary.Practitioners and researchers must always rely on their own experience and knowledge in

    evaluating and using any information, methods, compounds, or experiments described herein. Inusing such information or methods they should be mindful of their own safety and the safety ofothers, including parties for whom they have a professional responsibility.To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors,

    assume any liability for any injury and/or damage to persons or property as a matter of productliability, negligence or otherwise, or from any use or operation of any methods, products,instructions, or ideas contained in the material herein.

    Library of Congress Cataloging-in-Publication DataBleam, W. F. (William F.)Soil and environmental chemistry / William F. Bleam.p. cm.

    Reprinted with corrections.Includes bibliographical references and index.ISBN 978-0-12-415797-2 (alk. paper)

    1. Soil chemistry. 2. Environmental chemistry. I. Title.S592.5.B565 2012b631.41dc23

    2011028878

    British Library Cataloguing-in-Publication DataA catalogue record for this book is available from the British Library.

    For information on all Academic Press publications,visit our website: www.elsevierdirect.comTransferred to Digital Printing in 201230 Corporate Drive, Suite 400, Burlington, MA 01803, USAThe Boulevard, Langford Lane, Kidlington, Oxford, OX5 1GB, UK

    # 2012 Elsevier Inc. All rights reserved.No part of this publication may be reproduced or transmitted in any form or by any means,electronic or mechanical, including photocopying, recording, or any information storage andretrieval system, without permission in writing from the publisher. Details on how to seek

  • To Wilbert F. Bleam, my father and so much more.

  • develop problem-solving skills. Examples and problems rely on actual exper-

    imental data when available, supplemented by data gleaned from the USDA

    Natural Resources Conservation Service Soil Data Mart, the United States

    Environmental Protection Agency PBT Profiler and Integrated Risk Infor-mation System, and the National Atmospheric Deposition Program, to namea few. These examples are designed to develop key problem-solving skillsPreface

    The Earth, atmosphere, water, and living things abide intimately and insepar-

    ably in a place we call the soil. Any attempt to describe the chemistry of thispeculiar corner of the environment inevitably sets boundaries. Hydrology sits

    beyond the boundary for many soil chemists; but certain chemical processes

    take decades to develop, making residence time an important variable, to

    say nothing of belowground water transport. Again, soil microbiology may

    lay beyond the black stump separating chemistry from its cousin biology;

    yet respiratory processes drive redox chemistry wherever microbes are found

    in nature. Is there sufficient chemistry in risk assessment to warrant its inclu-

    sion despite differences in scientific dialect?

    Moving the boundaries outward to include Soil Moisture & Hydrology andRisk Assessment forces compensating choices. Herein Clay Mineralogy & ClayChemistry embraces layer silicates and swelling behavior, but demurs thebroader discussion of structural crystallography. Mineral weathering makes its

    appearance in Acid-Base Chemistry as the ultimate source of basicity, butdetailed chemical mechanisms receive scant attention. Ion exchange is strippedto its bare essentialsthe exchange isotherm and the factors determining its

    appearance. Natural Organic Matter & Humic Colloids adds content related tocarbon turnover and colloidal behavior, but does not take on the humification

    process or the primary structure of humic molecules. Water Chemistry down-plays algebraic methods in favor of model validation, reflecting my experience

    that students attain more success applying their chemical knowledge to validat-

    ing simulation results than slogging through mathematically complex and sym-

    bolically unfamiliar coupled equilibrium expressions. The hallmark of Acid-Base Chemistry is integrationpulling together water chemistry, ion exchange,and fundamental acid-base principles to develop an understanding of two chem-

    ically complex topics: exchangeable acidity and sodicity.

    Each chapter includes insofar as possible: actual experimental data plotted

    in graphic form, one or more simple models designed to explain the chemical

    behavior manifest in experimental data, and quantitative examples designed toxv

  • and to demonstrate methods for making sound estimates and predictions using

    basic chemistry principles, proven chemical models, and readily accessible

    soil, environmental, and chemical data.

    I wish to acknowledge several individuals who contributed to the planning,

    writing, and completion of this book. Philip Helmke and Phillip Barak, my

    chemistry colleagues at Madison, influenced uncounted choices of content

    and emphasis. Birl Lowery, John Norman, and Bill Bland, my soil physics

    colleagues, guided my choice to include hydrology. Robin Harris and Bill

    Hickey fed my interest and passion in environmental microbiology. Dr. Beat

    Muller of EAWAG (Das Schweizer Eidgenossischen Technischen Hochschulenund Forschung) was most helpful on all questions regarding ChemEQL. RobertW. Taylor, a friend dating from my Philadelphia days, exemplified encourage-

    ment. My graduate advisorsRoscoe Ellis, Murray B. McBride, and Roald

    Hoffmanguided my development as a young scientist, setting me on a course

    that ultimately led to writing this book. Edna J. Cash, a dear friend, diligently

    edited final drafts and proofs. Sharonmy wifewas always patient, always

    supportive.

    William F. Will Bleam,October 2010

    Prefacexvi

  • Elements: Their Origina

    Elements 16

    1.12 Estimating the Most Probable

    Concentration and

    Appendix 1F. The Estimate of

    Central Tendency and

    Variation of a Log-Normal

    Popular Science published an electronic version of the Periodic Table of the

    Elements in November 2006 (http://www.popsci.com/files/periodic_popup.html) that contained pictures of virtually all of the elements in pure form. Nota-

    bly absent are the radioactive elements: promethium Pm, astatine At, radon Rn,

    francium Fr, actinium Ac, protactinium Pa, and elem

    Soil and Environmental Chemistry.# 2012 Elsevier Inc. All rights reserved.Concentration Range Using Distribution 37

    1.1. INTRODUCTION1.11 Concentration Frequency

    Distributions of the

    Dilutions and the Law of

    Proportionate Effect 35nd Abundance

    Chapter Outline1.1 Introduction 1

    1.2 A Brief History of the Solar

    System and Planet Earth 2

    1.3 The Composition of Earths

    Crust and Soils 3

    1.4 The Abundance of Elements

    in the Solar System, Earths

    Crust, and Soils 3

    1.5 Elements and Isotopes 4

    1.6 Nuclear Binding Energy 6

    1.7 Enrichment and Depletion

    during Planetary Formation 8

    1.8 Planetary Accretion 9

    1.9 The Rock Cycle 12

    1.10 Soil Formation 13the Logarithmic

    Transformation 18

    1.13 Summary 21

    Appendix 1A.

    Factors Governing Nuclear

    Stability and Isotope

    Abundance 22

    Appendix 1B.

    Nucleosynthesis 25

    Appendix 1C. Thermonuclear

    Fusion Cycles 32

    Appendix 1D. Neutron-Emitting

    Reactions that Sustain the

    S-Process 34

    Appendix 1E. Random SequentialChapter 1ents beyond uranium U.

    1

  • Soil and Environmental Chemistry2There is a reason images of these elements are absent: every one of them is unsta-

    ble and, therefore, extremely rare. The Periodic Table of the Elements asserts that

    all elements exist in principle, but this particular table correctly implies that all ofthe elements from hydrogen to uranium exist on planet Earth. In fact, every sam-

    ple of water, rock, sediment, and soil contains every stable elementand proba-bly most of the unstable elementsfrom hydrogen to uranium.

    The Environmental Working Group published an article in October 2008

    entitled Bottled Water Quality Investigation: 10 Major Brands, 38 Pollutants

    (Naidenko, Leiba et al., 2008). Among the contaminants found in bottled water

    sold in the United States were the radioactive strontium isotope Sr-90 (0.02

    Bq L1), radioactive radium (isotopes Ra-286 plus Ra-288; 0.02Bq L1), boron(6090 mg L1), and arsenic (1 mg L1). These concentrations, combined with acommentary listing the potential and actual toxicity of these substances, can be

    alarming. The important question is not whether drinking water, food, air, soil,or dust contains toxic elements; it most certainly does! The important question

    is: is the level of any toxic element in drinking water, food, or soils harmful?

    The United States Environmental Protection Agency (USEPA) has estab-

    lished a maximum contaminant level (MCL) for beta emitterssuch as stron-tium-90 or radiumin public drinking water: 0.296 Bq L1 (8 pCi L1). Thecurrent USEPA drinking water MCL for arsenic is 10 mg L1; the mean arse-nic concentration in U.S. groundwater (based on over 20,000 samples) is

    2 mg L1. The USEPA does not have a drinking water standard for boron,but the World Health Organization (WHO) recommends boron levels in

    drinking water less than 500 mg L1, and in 1998 the European Unionadopted a drinking water standard of 100 mg L1. Typical boron concentra-tions in U.S. groundwater fall below 100 mg L1 and 90% below 40mg L1. Evaluated in context, the contaminants found in bottled water areless threatening and raise the question of whether it is reasonable to entirely

    eliminate trace elements from water and food.

    1.2. A BRIEF HISTORY OF THE SOLAR SYSTEM AND PLANETEARTH

    The gravitational collapse of a primordial cloud of gas and dust gave birth to

    the present-day Solar System. The conservation of angular momentum in the

    primordial dust cloud explains the rotation of the Sun (25-day rotation period

    at the equator) and a primordial accretion disk that spawned the planets and

    other bodies that orbit the Sun. The primordial gas and dust cloud was well

    mixed and uniform in composition. Gravitational accretion and radioactive

    decay released sufficient heat to melt the early Earth, leading segregation into

    a solid metallic core, a molten mantle, and a crystalline crust. Planetary for-

    mation and segregation altered the composition of Earths crust relative to

    the primordial cloud and imposed variability in the composition of each ele-ment as a direct consequence of each separation process.

  • Chapter 1 Elements 3Throughout its entire history, planet Earth has experienced continual trans-

    formation as plate tectonics generate new inner (oceanic) crust and shift plates

    of outer (continental) crust around like pieces of a jigsaw puzzle. Plate tecton-

    ics and the hydrologic cycle drive a rock cycle that reworks portions of the

    outer crust through weathering, erosion, and sedimentation. The rock cycle

    imposes a new round of geochemical separation processes that alters the com-

    position of the terrestrial land surface relative to the outer crust from which it

    derives. The rock cycle and soil development, much like planetary formation

    and segregation early in Earths history scale, impose additional variability in

    the composition of each element. Transformations in the overall compositionof planet Earth and the imposition of composition variability relative to theprimordial gas cloud are the central themes of this chapter.

    1.3. THE COMPOSITION OF EARTHS CRUST AND SOILS

    Most books on geology, soil science, or environmental science include a table

    listing the composition of Earths crust or soil. There are several reasons for

    listing the elemental composition of Earth materials. The composition of soil

    constrains the biological availability of each element essential for living

    organisms. Soils develop from the weathering of rocks and sediments and

    inherit much of their composition from the local geology. The most common

    elementsthose accounting for 9095% of the total composition

    determine the dominant mineralogy of rocks and materials that form when

    rocks weather (residuum, sediments, and soils).

    The soil at a particular location develops in starting or parentmaterialrockor sedimentsunder a variety of local influenceslandform relief, climate, and

    biological community over a period of decades or centuries. Not surprisingly,

    the composition of soil is largely inherited from the parent material. The rocks

    or sediments in which a soil develops are usually not the basement rocks that

    compose the bulk of Earths crust. Regardless of geologic history, virtually

    every rock exposed at the Earths terrestrial surface owes its composition to

    the crystalline igneous rock of the continental crust. The Earths outer crust

    inherits its composition from the overall composition of the planet and, by

    extension, the gas and dust cloud that gave rise to the Solar System as a whole.

    How much do the composition of soil, Earths crust, and the Solar System

    have in common? What can we learn about the processes of planetary forma-

    tion, the rock cycle, and soil development from any differences

    in composition? What determines the relative abundance of elements in soil?

    1.4. THE ABUNDANCE OF ELEMENTS IN THE SOLAR SYSTEM,EARTHS CRUST, AND SOILS

    We are looking for patterns, and, unfortunately, data in tabular form usually

    do not reveal patterns in their most compelling form. Patterns in the elementalabundance of the Solar System, Earths crust, and soils are best understood

  • 4when abundance is plotted as a function of atomic number Z. Astronomersbelieve the composition of the Suns photosphere is a good representation

    of the primordial gas and dust cloud that gave rise to the Solar System. Usu-

    ally the composition of the Solar System is recorded as the atom mole fraction

    of each element, normalized by the atom mole fraction of silicon.

    The composition of Earths crust and soil is usually recorded as the mass

    fraction of each element. If we are to compare the compositions of the Solar

    System, Earths crust, and soils, the abundance data must have the same units.

    Since atoms combine to form compounds based on atomic mole ratios, the

    atom mole fraction is the most informative. The atom mole fraction is found

    by dividing the mass fraction of each elementin crust or soilby its atomic

    mass and then normalized by the atom mole fra...

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