Geochemical and Hydrological Reactivity of Heavy Metals in Soils - Chapter 1

and Hydrological Heavy Metals Edited by William L. Kingery LEWIS PUBLISHERS A CRC Press Company Boca Raton London New York Washington, D.C. © 2003 by CRC Press LLC Library of Congress Cataloging-in-Publication Data Geochemical and hydrological reactivity of heavy metals in soils / edited by H. Magdi Selim, William L. Kingery. p. cm. Includes bibliographical references and index. ISBN 1-56670-623-8 (alk. paper) 1. Soils—Heavy metal content. 2. Havy metals—Environmental aspects. 3. Soil moisture. 4. Soil chemistry. I. Kingery, William L. II. Title. S592.6.H43S44 2003 628.5¢5—dc21 2002043282 This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. 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Visit the CRC Press Web site at www.crcpress.com © 2003 by CRC Press LLC Lewis Publishers is an imprint of CRC Press LLC No claim to original U.S. Government works International Standard Book Number 1-56670-623-8 Library of Congress Card Number 2002043282 Printed in the United States of America 1 2 3 4 5 6 7 8 9 0 Printed on acid-free paper © 2003 by CRC Press LLC Preface This volume aims at providing a coherent presentation of recent developments and understanding of heavy metal reactivity in soils. Such an understanding is necessary in addressing heavy metals concerns in the environment. The implicit framework of multiple reactivity acknowledges the widely known role played by the various colloidal surface functional groups in concomitant reactions. This overarching frame of reference allows unification between molecular structure-reactivity relationships at one scale and transport processes at the other. The broader concepts of geochemical and hydrological reactivities are coupled in the first three chapters. Chapter 1 addresses hydrological and geochemical pro-cesses controlling the fate and transport of low-level radioactive waste in a subsurface media comprised of fractured saprolite and interbedded fractured limestone and shale bedrock. Use is made of a wealth of observations using multiple tracer techniques in the field to explain the impact of transport processes on the nature and extent of secondary contaminant sources. The effect of colloid mineralogy on their capacity to mediate the transport of heavy metals is presented in Chapter 2 through a series of experimental results employing metal-contaminated suspensions of ex-situ soil colloids with montmorillonitic, illitic, and kaolinitic mineralogy applied to undis-turbed soil monoliths. Eluent, colloid, and metal recoveries varied with metal, colloid, and soil properties. Mechanisms responsible for colloidal involvement in metal mobility are discussed. Appearing in Chapter 3 is a description of the extension of a multireaction/transport simulation system from one-dimension to three-dimen-sional applications, using the alternating-direction-implicit numerical algorithm. Also discussed is its implementation in a web-based system with a user-friendly interface providing client-side and server-side computing applications and web-based visualization functionality. Chapters 4 through 10 collectively treat various aspects of geochemical reac-tivity on a variety of levels. Fundamental approaches using both experimental observations and theoretical analysis of mineral and organic colloidal surface complexation of contaminants are described in Chapters 4, 5, and 6, while micro-bial processes are the focus of Chapter 7. Chapter 4 points to mechanisms of metal binding at mineral–water interfaces through an examination of proton adsorption. The authors primarily center on the protonating-deprotonating properties of phyl-losilicate clays by stressing the key role played by lattice charges in determining sorption at both basal planes and particle edges. Results are given in Chapter 5 of attempts to combine computational chemistry and molecular modeling to pro-vide a molecular-scale picture of the relation between the complex structural framework of soil organic matter and metal complexation. In the process, the conceptual underpinnings of the application of quantum and classical mechanical © 2003 by CRC Press LLC simulations to the study of geochemical reactivity are provided. In Chapter 6, the author speaks to the current emphasis on the environmental significance of con-nections among inorganic species, mineral surfaces, organic molecules, and microbes. Employing the metalloid silicon, the second-most abundant element in the Earth’s crust, an examination is given of the possible existence of hypercoor-dinated silicon-organic ligand-silicon complexes in ambient aqueous solutions using classical electrostatic and solvation theory, crystal chemistry, thermodynam-ics, and ab initio molecular orbital calculations. The kinetics of biological Mn oxidation and the reactivity of biogenic Mn oxides are developed in Chapter 7. Biological Mn oxidation is important because it can exert an important influence on the cycling and bioavailability of trace metals. In addition, the authors describe details and implications of recent studies demonstrating the greater reactivity of biogenic Mn oxides as compared to those formed under abiotic conditions. Chapters 8 through 10 form a related series addressing geochemical reactivity in soils. In Chapter 8, the authors use a combination of analytical techniques, including x-ray diffraction, electron microscopy, and x-ray absorption, for speciation and quantification of Zn in a soil contaminated as a result of smelting operations. They unite these with chemical extraction and leaching experiments in order to relate metal speciation to bioavailability. Trace metal solubility is explained in Chapter 9 in terms of the release associated with soil Mn-oxides reduction and by an associated displacement of exchangeable metals by high solution concentrations of the dissolved Mn oxide. The authors describe the coupling of these processes using empirical relationships and ion exchange equilibria. The properties and behav-ior in soils of dissolved organic matter (DOM) and its effect on the environmental behavior of metals is given in Chapter 10. Here the authors discuss the relation of DOM hydrophilic and hydrophobic characteristics and the influence of DOM on trace metal sorption. The concept of hydrologic reactivity is emphasized in Chapters 11 and 12. In Chapter 11, problems associated with analytical techniques that lead to an inadequate assessment of a complex array of natural surfaces are discussed. The aim is to present some of the key instrumental analysis methods that have wide application to the study of mobile colloids, including light-scattering methods (i.e., photon correlation spectroscopy); acoustic/electroacoustic methods; field flow fractionation; and scan-ning and transmission electron microscopy. Chapter 12 presents a general-purpose transport model of the multireaction type to describe sulfate transport in forest soils. Discussion is provided on the use of various versions of the multireaction model (equilibrium and kinetic) in describing effluent results from different soil layers. In Chapter 13, a brief treatment is given of fluoride solubility in arid-zone soils con-taminated by a nearby phosphate fertilizer production plant. We wish to sincerely thank the contributors of this book for their diligence and cooperation in achieving our goal and making this volume a reality. We are most grateful for their time and effort in critiquing the various chapters, and in keeping with the focus on the reactivity of heavy metals in soils. Special thanks are due to the reviewers for their help in reviewing individual chapter contributions. Without © 2003 by CRC Press LLC the support of Louisiana State University and Mississippi State University, this project could not have been realized. We also express our thanks to Randi Cohen, Erika Dery, and the CRC staff for their help and cooperation in the publication of this book. H. Magdi Selim Louisiana State University William L. Kingery Mississippi State University © 2003 by CRC Press LLC ... - tailieumienphi.vn