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BIOPHYSICO-CHEMICALPROCESSES OF HEAVYMETALS AND METALLOIDSIN
SOIL ENVIRONMENTS
Edited by
ANTONIO VIOLANTEPAN MING HUANGGEOFFREY MICHAEL GADD
A JOHN WILEY & SONS, INC., PUBLICATION
Innodata9780470175477.jpg
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BIOPHYSICO-CHEMICALPROCESSES OF HEAVYMETALS AND METALLOIDSIN
SOIL ENVIRONMENTS
-
BIOPHYSICO-CHEMICALPROCESSES OF HEAVYMETALS AND METALLOIDSIN
SOIL ENVIRONMENTS
Edited by
ANTONIO VIOLANTEPAN MING HUANGGEOFFREY MICHAEL GADD
A JOHN WILEY & SONS, INC., PUBLICATION
-
Copyright 2008 by John Wiley & Sons, Inc. All rights
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Published by John Wiley & Sons, Inc., Hoboken, New
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Wiley Bicentennial Logo: Richard J. PaciÞco
Library of Congress Cataloging-in-Publication Data:
Biophysico-chemical processes of heavy metals and metalloids in
soilenvironments / edited by Antonio Violante, Pan Ming Huang,
Geoffrey MichaelGadd.
p. cm. (Wiley-IUPAC series. Biophysico-chemical processes
inenvironmental systems)
Includes index.ISBN 978-0-471-73778-0 (cloth)
1. Heavy metalsEnvironmental aspects. 2. Soil pollution. 3.
SoilsHeavymetal content. I. Violante, A. (Antonio) II. Huang, P. M.
III. Gadd, GeoffreyM.
TD879.H4B55 2007628.55dc22
2007019078
Printed in the United States of America
10 9 8 7 6 5 4 3 2 1
http://www.copyright.comhttp://www.wiley.com/go/permissionhttp://www.wiley.com
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CONTENTS
CONTRIBUTORS ix
PREFACE xiii
SERIES PREFACE xv
ABOUT THE EDITORS xvii
PART I FUNDAMENTALS OF BIOTIC AND ABIOTICINTERACTIONS OF METALS
ANDMETALLOIDS WITH SOIL COMPONENTS 1
1 Impacts of PhysicochemicalBiological Interactions on Metaland
Metalloid Transformations in Soils: An Overview 3P. M. Huang
2 Transformation and Mobilization of Metals, Metalloids,and
Radionuclides by Microorganisms 53G. M. Gadd
3 Kinetics and Mechanisms of SorptionDesorption in Soils:A
Multiscale Assessment 97M. J. Borda and D. L. Sparks
4 Spectroscopic Techniques for Studying MetalHumicComplexes in
Soil 125N. Senesi and E. Loffredo
5 Factors Affecting the SorptionDesorption of TraceElements in
Soil Environments 169A. Violante, G. S. R. Krishnamurti, and M.
Pigna
v
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vi CONTENTS
6 Modeling Adsorption of Metals and Metalloids by SoilComponents
215S. Goldberg and L. J. Criscenti
PART II TRANSFORMATIONS AND DYNAMICS OF METALSAND METALLOIDS AS
INFLUENCED BYSOILROOTMICROBE INTERACTIONS 265
7 Biogeochemistry of Metals and Metalloids at the
SoilRootInterface 267P. Hinsinger and F. Courchesne
8 Biogeochemical Processes Controlling the Cycling of Arsenicin
Soils and Sediments 313S. Fendorf, M. J. Herbel, K. J. Tufano, and
B. D. Kocar
9 Microbial Oxidation and Reduction of Iron in the RootZone and
Inßuences on Metal Mobility 339S. C. Neubauer, D. Emerson, and J.
P. Megonigal
10 The Complexity of Aqueous Complexation: The Caseof Aluminum
and Iron(III)Citrate 373M. E. Essington
PART III SPECIATION, MOBILITY, AND BIOAVAILABILITYOF METALS AND
METALLOIDSAND RESTORATION OF CONTAMINATED SOILS 417
11 Chemical Speciation and Bioavailability of Trace Metals 419G.
S. R. Krishnamurti and R. Naidu
12 Fractionation and Mobility of Trace Elements in Soilsand
Sediments 467P. S. Fedotov and M. Miró
13 Sources and Mobility of Metallic Radionuclides in Soil
Systems 521S. Staunton, C.-S. Haudin, G. Wang, and G. Shaw
14 Remediation of Metal-Contaminated Soils: An Overview 565M.
Gräfe and R. Naidu
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CONTENTS vii
15 Phosphate-Induced Lead Immobilization in Contaminated
Soils:Mechanisms, Assessment, and Field Applications 607R. Melamed
and L. Q. Ma
INDEX 631
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CONTRIBUTORS
Michael J. BordaGolder Associates, Inc.200 Century Parkway,
Suite CMt. Laurel, NJ 08054USATel.: 856-793-2005, ext. 34323Fax:
856-793-2006E-mail: [email protected]
François CourchesneDépartement de GéographieUniversité de
MontréalC.P. 6128, succ. Centre-VilleMontréal, Québec H3C
3J7CANADATel.: 514-343-8027Fax: 514-343-8008E-mail:
[email protected]
Louise J. CriscentiGeochemistry DepartmentSandia National
LaboratoriesP.O. Box 5800, MS 0754Albuquerque, NM
87185-0750USATel.: 505-284-4357Fax: 505-844-7354E-mail:
[email protected]
David EmersonAmerican Type Culture Collection10801 University
BoulevardManassas, VA 20110USATel.: 703-365-2804Fax:
703-365-2790E-mail: [email protected]
Michael E. EssingtonDepartment of Biosystems
Engineering and Soil ScienceThe University of Tennessee2506 E.J.
Chapman DriveKnoxville, TN 37996-4531USATel.: 865-974-7266Fax:
865-974-4514E-mail: [email protected]
Petr S. FedotovVernadsky Institute of Geochemistry
and Analytical ChemistryRussian Academy of Sciences19 Kosygin
Street119991 MoscowRUSSIATel.: +7 (495) 1378608Fax: +7 (495)
9382054E-mail: fedotov [email protected]
ix
-
x CONTRIBUTORS
Scott FendorfDepartment of Geological and
Environmental SciencesStanford UniversityStanford, CA
94305USATel.: 650-723-5238Fax: 650-725-2199E-mail:
[email protected]
Geoffrey Michael GaddDivision of Molecular and
Environmental MicrobiologyCollege of Life SciencesUniversity of
DundeeDundee DD1 5EHScotlandUKTel.: +44 (0)1382 384765Fax: +44
(0)1382 388216E-mail: [email protected]
Sabine GoldbergGeorge E. Brown, Jr., Salinity
LaboratoryUSDA-ARS450 West Big Springs RoadRiverside, CA
92507USATel.: 951-369-4820Fax: 951-342-4962E-mail:
[email protected]
Markus GräfeRoss Street Building, Room 322Faculty of
Agriculture, Food and
Natural ResourcesThe University of SydneySydney, NSW
2006AUSTRALIATel.: +61(0)2-9036-6359Fax: +61(0)2-9351-5108E-mail:
[email protected]
Claire-Sophie HaudinAndra, 1-7 rue Jean Monnet92298
Chatenay-Malabry
FRANCEE-mail: [email protected]
Mitchell J. HerbelBioScreen Testing Services3904 Del Amo
BoulevardTorrance, CA 90503USATel.: 310-214-0043, ext. 113Fax:
650-725-2199E-mail: [email protected]
Philippe HinsingerINRASupAgroUMR 1222
Biogéochimie du Sol et de laRhizosphère
Place VialaF-34060 Montpellier cedex 1FRANCETel.: +33 (0)4 99 61
22 49Fax: +33 (0)4 99 61 30 88E-mail:
[email protected]
Pan Ming HuangDepartment of Soil ScienceUniversity of
Saskatchewan51 Campus DriveSaskatoon, SK S7N 5A8CANADATel.:
001-306-966-6838Fax: 001-306-966-6881E-mail:
[email protected]
Benjamin D. KocarDepartment of Geological and
Environmental SciencesStanford UniversityStanford, CA
94305USATel.: 650-723-4152Fax: 650-725-2199E-mail:
[email protected]
Gummuluru S. R. Krishnamurti313-855 West 16th StreetNorth
Vancouver, BC V7P 1R2CANADA
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CONTRIBUTORS xi
Tel.: 604-904-9168E-mail: [email protected]
Elisabetta LoffredoDipartimento di Biologia e Chimica
Agroforestale ed AmbientaleUniversità di BariVia Amendola
165/A70126 BariITALYTel.: +39-080-5442282Fax:
+39-080-5442850E-mail: [email protected]
Lena Q. MaSoil and Water Science DepartmentUniversity of
FloridaGainesville, FL 32611-0290USATel.: 352-392-9063, ext.
208Fax: 352-392-3902E-mail: Lqma@uß.edu
J. Patrick MegonigalSmithsonian Environmental
Research CenterP.O. Box 28647 Contees Wharf RoadEdgewater, MD
21037USATel.: 443-482-2346Fax: 443-482-2380E-mail:
[email protected]
Ricardo MelamedCETEM/MCTCenter for
Mineral TechnologyMinistry of Science and TechnologyAv. Ipe
900Ilha da Cidade UniversitariaRio de Janeiro 21941-590BRAZILTel.:
55 (21) 865-7222 or 865-7303Fax: 55 (21) 260-2837E-mail:
[email protected]
Manuel MiróDepartment of Chemistry
University of the Balearic IslandsFaculty of SciencesCarretera
de Valldemossa Km 7.5E-07122 Palma de MallorcaIlles
BalearsSPAINTel.: +34 971 259576Fax: +34 971 173426E-mail:
[email protected]
Ravendra NaiduCooperative Research Centre for
Contamination Assessment andRemediation of the Environment
SPRI Building, Room W2-34Mawson Lakes, South Australia
5095AUSTRALIATel.: 61 8 83025041Fax: 61 8 83025041E-mail:
[email protected]
Scott C. NeubauerBaruch Marine Field LaboratoryUniversity of
South CarolinaP.O. Box 1630Georgetown, SC 29442USATel.:
843-546-3623Fax: 843-546-1632E-mail: [email protected]
Massimo PignaDipartimento di Scienze del Suolo,
della Pianta e dellAmbienteUniversità di Napoli Federico IIVia
Università 10080055 Portici (Napoli)ITALYTel.: +39 081 2539176Fax:
+39 081 2539186E-mail: [email protected]
Nicola SenesiDipartimento di Biologia e Chimica
Agroforestale e AmbientaleUniversità di BariVia Amendola
165/A
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xii CONTRIBUTORS
70126 BariITALYTel.: +39 080 5442853Fax: +39 080 5442850E-mail:
[email protected]
George ShawDivision of Agricultural and
Environmental SciencesUniversity of NottinghamUniversity
ParkNottingham NG7 2RDUKTel.: 44 (0)115 95 13206Fax: 44 (0)115 95
16267E-mail:
[email protected]
Donald L. SparksDepartment of Plant and Soil SciencesUniversity
of DelawareNewark, DE 19717-1303USATel.: 302-831-8153Fax:
302-831-0605E-mail: [email protected]
Siobhan StauntonUMR Biogéochemie du Sol et de la
RhizosphèreINRAPlace VialaF-34060 Montpellier CedexFRANCETel.:
00 33 4 99 61 23 31Fax: 00 33 499 61 30 88E-mail:
[email protected]
Katharine J. TufanoDepartment of Geological and
Environmental SciencesBraun Hall, Building 320, Room 118Stanford
UniversityStanford, CA 94305USATel.: 650-723-4152Fax:
650-725-2199E-mail: [email protected]
Antonio ViolanteDipartimento di Scienze del Suolo,
della Pianta e dellAmbienteUniversità di Napoli Federico IIVia
Università 10080055 Portici (Napoli)ITALYTel.: +39 081 2539176Fax:
+39 081 2539186E-mail: [email protected]
Guo WangDepartment of Resources and
Environmental SciencesFujian Agriculture and Forestry
UniversityFuzhou, Fujian 350002PEOPLES REPUBLIC
OF CHINATel.: 0591-83789357Fax: 0591-83776849E-mail:
[email protected]
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PREFACE
Pollution induced by heavy metals and metalloids in soils is a
serious environ-mental problem because, in comparison with the
atmosphere and water, the soilenvironment has a much lower ability
to recover from toxic effects. In soil, traceelements potentially
toxic to plants and other living organisms are involved inchemical
and biological reactions such as solution and surface complexation,
pre-cipitation, sorptiondesorption, and oxidationreduction. These
elements interactwith a series of clay minerals, humic substances,
metal oxides, microorganisms,extracellular enzymes, biopolymers,
and other organic and inorganic ligands.Their behavior depends on
chemical and physicochemical as well as biologicalprocesses and
their interactions with microbial activities. These
physicochemi-calbiological interactions would inßuence the transfer
of these elements fromthe inorganic and organic soil constituents
to the soil solution and to plantsand contaminate the terrestrial
food chain, thus endangering human and animalhealth. Biogeochemical
processes operating in soil environments that affect thefate,
behavior, and bioavailability of metals and metalloids are
currently an areaof active research.
As a recognition of the importance of biophysico-chemical
processes of met-als and metalloids in soil environments, we
initiated the Þrst volume of theIUPACWiley book series
Biophysico-Chemical Processes in EnvironmentalSystems. This volume,
which consists of 15 chapters, is organized into threeparts:
Fundamentals of Biotic and Abiotic Interactions of Trace Metals and
Met-alloids with Soil Components; Transformations and Dynamics of
Metals andMetalloids as Inßuenced by SoilRootMicrobe Interactions;
and Speciation,Mobility, and Bioavailability of Metals and
Metalloids and Restoration of Con-taminated Soils.
This book, contributed by a multidisciplinary group of soil and
environmentalscientists, provides the scientiÞc community with a
critical evaluation of the stateof the art on the fundamentals of
reactions and processes of these elements insoil environments,
their speciation, mobility, bioavailability, and toxicity and
theirimpact on the development of innovative restoration
strategies. The book is an
xiii
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xiv PREFACE
important guide to scientists interested in environmental
sciences, soil chemistryand mineralogy, soil biochemistry, soil
microbiology, and plant nutrition andphysiology as related to
understanding the biophysico-chemical processes of thesepollutants
in soil environments. The latest advances in spectroscopy to
studyvarious aspects of heavy metal and metalloid interactions with
soil inorganicand organic components are also reviewed critically
and addressed clearly. Theauthors are scientists who are experts in
their Þelds and the chapters have beenreviewed critically by at
least two external referees. We wish to thank all of thereferees,
who generously contributed their time and talent to maintain the
highquality of this volume. We also express our thanks to the staff
of IUPAC and JohnWiley & Sons for their invaluable support and
cooperation in the publication ofthe book.
A. ViolanteP. M. HuangG. M. Gadd
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SERIES PREFACE
ScientiÞc progress is based ultimately on uniÞcation rather than
fragmentationof knowledge. Environmental science is the fusion of
physical and life sciences.Physical, chemical, and biological
processes in the environment are not indepen-dent but rather,
interactive processes. Therefore, it is essential to address
physical,chemical, and biological interfacial interactions to
understand the composition,complexity, and dynamics of ecosystems.
Keeping separate these domains, nomatter how fruitful, one cannot
hope to deliver on the full promise of modernenvironmental science.
The time is upon us to recognize that the new frontier
inenvironmental science is the interface, wherever it remains
unexplored.
The Division of Chemistry and the Environment of the
International Union ofPure and Applied Chemistry (IUPAC) has
recently approved the creation of anIUPAC-sponsored book series
entitled Biophysico-Chemical Processes in Envi-ronmental Systems to
be published by John Wiley & Sons, Hoboken, NJ. Thisseries
addresses the fundamentals of physicalchemicalbiological
interfacialinteractions in the environment and the impacts on (1)
the transformation, trans-port, and fate of nutrients and
pollutants; (2) food chain contamination and foodquality and
safety; and (3) ecosystem health, including human health.
The book Biophysico-Chemical Process of Heavy Metals and
Metalloids in SoilEnvironments is Volume I of this newly created
WileyIUPAC series. The trans-formation of metals and metalloids is
inßuenced by phsicochemicalbiologicalinterfacial interactions. The
impacts of these interactive processes are especiallyimportant in
the rhizoshpere, which is the bottleneck of the contamination of
theterrestrial food chain, and in the location near the
decomposition of biologicalresidues. In contrast to classical books
which focus largely on separate physical,chemical, and biological
processes, this book is unique in integrating the fron-tiers of
knowledge on both fundamentals and impacts of interfacial
interactionsof physical, chemical, and biological processes
pertaining to the transformation,transport, bioavailability, and
toxicity of metals and metalloids in soil environ-ments.
xv
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xvi SERIES PREFACE
This book can be used as an advanced reference book on
biophysico-chemicalprocesses of metals and metalloids in soils and
related environments for seniorundergraduate and graduate students
in soil and environmental sciences. It isan essential reference for
chemists and biologists studying environmental sys-tems. It will
serve as a useful resource book for instructors, research
scientists,professional consultants, and others working on
environmental and ecologicalsystems.
Series EditorsP. M. HuangN. Senesi
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ABOUT THE EDITORS
Antonio Violante is professor of soil chemistry at the
Department of Soil, Plantand Environmental Sciences, University of
Naples Federico II, Italy, where hehas been actively involved in
research and teaching since 1970. He receivedhis academic degree in
chemistry from the University of Naples in 1969. Hespent two
sabbatical years at the University of Wisconsin, Madison
(19761977)and the University of Saskatchewan, Saskatoon, Canada
(19811982) and wasinvited to serve as a visiting professor in the
Department of Soil Science atthe University of Saskatchewan in
1985, 1992, and 2003. He was Head of theDipartimento di Scienze
Chimico-Agrarie from 1994 to 1999 and is coordinatorof the Doctoral
School in Agrobiology and Agrochemistry.
Dr. Violante has taught courses in agricultural chemistry, soil
chemistry, andsoil fertility for undergraduate students and in
environmental biogeochemistryand soil mineralogy for Ph.D.
students. He has trained many M.S. and Ph.D.students and
postdoctoral fellows and has received visiting scientists
worldwide.Three of his students have received awards for their
theses in soil chemistry.
He has contributed to research on the interface between soil
chemistry andmineralogy and soil biology. His special areas of
research include the formationmechanisms of aluminum hydroxides and
oxyhydroxides, the surface chemistryand reactivities of
short-range-ordered precipitation products of Al and Fe,
theinßuence of biomolecules on the sorption and desorption of
nutrients and xeno-biotics on and from variable charge minerals and
soils, the factors that inßuencethe sorption and residual activity
of enzymes on phyllosilicates, variable chargeminerals,
organomineral complexes, and soils and the chemistry of arsenic in
soilenvironments.
Dr. Violante has served on many committees of the Italian
Society of SoilScience (president of the session on soil chemistry)
and the Italian Society ofAgricultural Chemistry. He is
vice-president and liaison ofÞcer of Gruppo ItalianoAIPEA. He has
been the scientiÞc chairman and chief organizer of internationaland
national congresses.
xvii
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xviii ABOUT THE EDITORS
Dr. Violante is the author or coauthor of 167 refereed research
articles andbook chapters and invited reviews, and has coedited six
books. He has alsopresented papers at many scientiÞc congresses and
symposia and has given invitedlectures at universities and research
institutes worldwide. He has internationalresearch and teaching
experience in Canada, the United States, Europe, China,and Chile.
He is a Fellow of the Soil Science Society of America and
AmericanSociety of Agronomy.
Pan Ming Huang received his Ph.D. degree in soil science at the
Universityof Wisconsin, Madison, in 1966. He is professor emeritus
of soil science at theUniversity of Saskatchewan, Saskatoon,
Canada. His research work has signiÞ-cantly advanced the frontiers
of knowledge on the formation chemistry and natureand surface
reactivity of mineral colloids, organic matter, and organomineral
com-plexes of soils and sediments and their role in the dynamics,
transformations,and fate of nutrients, toxic metals, and
xenobiotics in terrestrial and aquaticenvironments. His research
Þndings, embodied in over 300 refereed scientiÞcpublications,
including nine research papers published in Nature and others
inleading journals, book chapters, and books, are fundamental to
the developmentof sound strategies for managing land and water
resources.
He has developed and taught courses in soil physical chemistry
and miner-alogy, soil analytical chemistry, and ecological
toxicology. He has trained andinspired M.Sc. and Ph.D. students and
postdoctoral fellows, and has received vis-iting scientists from
all over the world. He has served on numerous national
andinternational scientiÞc and academic committees. He has also
served as a memberof many editorial boards, including those of the
Soil Science Society of AmericaJournal; Geoderma; Chemosphere;
Water, Air and Soil Pollution; Soil Scienceand Plant Nutrition; and
Pedosphere. He has served as a titular member of theDivision of
Chemistry and the Environment of the International Union of Pureand
Applied Chemistry and is the founding chairman of the Working Group
MO,Interactions of Soil Minerals with Organic Components and
Microorganisms,and the founding chair of Commission 2.5, Soil
Physical/Chemical/BiologicalInterfacial Reactions, of the
International Union of Soil Sciences. He receivedthe Distinguished
Researcher Award from the University of Saskatchewan andthe Soil
Science Research Award from the Soil Science Society of America.
Heis a Fellow of the Canadian Society of Soil Science, the Soil
Science Society ofAmerica, the American Society of Agronomy, the
American Association for theAdvancement of Science, and the World
Innovation Foundation.
Geoffrey Michael Gadd is an international leader in the Þeld of
metals andmicroorganisms and is well known for research that has
advanced understandingof cellular and physicochemical mechanisms
underlying microbialmetal trans-formations, and their environmental
and biotechnological signiÞcance, especiallyin relation to metal
and radionuclide geomicrobiology. He holds a personal chairin
microbiology at the University of Dundee and has served as Head of
theDepartment of Biological Sciences, Head of the Division of
Environmental and
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ABOUT THE EDITORS xix
Applied Biology, and as deputy research director of the School
of Life Sciences;currently, he is Head of the Division of Molecular
and Environmental Micro-biology. Several scientiÞc societies have
recognized Professor Gadds researchthrough speciÞc awards (e.g.,
the Berkeley Award of the British MycologicalSociety, the Charles
Thom Award of the Society for Industrial Microbiology),and he is a
Fellow of the Linnean Society, the Institute of Biology, the
AmericanAcademy of Microbiology, and the Royal Society of
Edinburgh. From 2004 to2006 he served as president of the British
Mycological Society (the Þrst to serve athree-year term of ofÞce)
and is currently convener of the Environmental Micro-biology Group
of the Society for General Microbiology. He has contributed tothe
vitality of his Þeld via signiÞcant contributions to many
professional societiesand national and international editorial
boards, advisory groups, and committees.Professor Gadd has
published over 190 refereed scientiÞc papers, over 40 editedbooks
(two as sole editor), and over 35 invited book chapters.
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PART I
FUNDAMENTALS OF BIOTIC ANDABIOTIC INTERACTIONS OFMETALS AND
METALLOIDS WITHSOIL COMPONENTS
1
-
1IMPACTS OFPHYSICOCHEMICALBIOLOGICALINTERACTIONS ON METAL
ANDMETALLOID TRANSFORMATIONSIN SOILS: AN OVERVIEW
P. M. HuangUniversity of Saskatchewan, Saskatoon, Saskatchewan,
Canada
1.1. Introduction 4
1.2. Mineralorganic mattermicroorganism interactions in soil
environments 61.2.1. Formation of short-range-ordered metal oxides
71.2.2. Formation of humic substances and organomineral complexes
91.2.3. Formation of aggregates and porosity 13
1.3. Solution complexation reactions of metals 16
1.4. Reductionoxidation reactions of metals and metalloids
17
1.5. Sorptiondesorption reactions of metals and metalloids
20
1.6. Precipitationdissolution reactions of metals and metalloids
23
1.7. Microbe-mediated metal and metalloid release from soil
particles 24
1.8. Microbial sorption and uptake of metals and metalloids
25
1.9. Biomineralization of metals and metalloids and Þne-grained
mineraldevelopment 27
1.10. Impacts on the terrestrial ecosystem 291.10.1. Global ion
cycling 291.10.2. Geomedical problems 301.10.3. Ecotoxicological
problems 301.10.4. Biodiversity 321.10.5. Risk assessment,
management, and restoration of soil environments 33
1.11. Conclusions and future directions 39
Biophysico-Chemical Processes of Heavy Metals and Metalloids in
Soil Environments,Edited by Antonio Violante, Pan Ming Huang, and
Geoffrey Michael GaddCopyright 2008 John Wiley & Sons, Inc.
3
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4 IMPACTS OF PHYSICOCHEMICALBIOLOGICAL INTERACTIONS
1.1. INTRODUCTION
Soil, geoderma, is the skin of planet Earth and the central
organizer of the ter-restrial ecosystem. It is a life-sustaining
material which is a structurally porousand biologically active
medium that has evolved over time on continental landsurfaces. This
material is formed and continues to develop through
weatheringprocesses driven by geological, biogeochemical,
topological, climatic, chrono-logical, and anthropogenic
inßuences.
Soils are complex interactive biogeochemical reactors,
reservoirs of organisms(microorganisms, protozoans, and nematodes),
and major compartments of theterrestrial ecosystem. Minerals,
organic components, and organisms are amongmajor solid components
of soils. These components are not separate entities butrather,
form a uniÞed system whose members are constantly in association
witheach other in the environment (Huang and Schnitzer, 1986; Huang
et al., 1995;BanÞeld and Nealson, 1997). The association of
microorganisms with soil mineraland organic colloids is depicted in
Figure 1.1. Interactions among the compo-nents have an enormous
impact on the physics, chemistry, and biology of soiland
surrounding ecosystems (Huang, 2002). However, physical, chemical,
andbiological processes are not independent but rather, interactive
processes in soilenvironments. A fundamental understanding of
physical, chemical, and biologicalinterfacial interactions in soil
is essential in restoring, enhancing, and sustainingecosystem
productivity, services, and integrity and for establishing soils
impacton human welfare. In view of the mineralorganic
componentorganism interac-tions and interactive physical, chemical,
and biological processes in the terrestrialecosystem, a commission
on Soil Physical/Chemical/Biological Interfacial Reac-tions was
created within the structure of the International Union of Soil
Sciencesin 2004.
The transformation of metals and metalloids in the environment
is inßuencedby physicochemicalbiological interfacial interactions.
The impact of these inter-active interfacial processes on metal and
metalloid transformations is especiallyimportant in the rhizosphere
(Huang and Germida, 2002; Huang and Gobran,2005) and near the
decomposition of plant residues (Huang and Schnitzer, 1986),where
the types and concentrations of substrates are different from those
of thebulk soil because of enhanced biological activity. In the
rhizosphere, root exuda-tion leads to colonization by various
populations of bacteria, fungi, protozoans,and nematodes. The
distribution of microorganisms with distance from the rootis
illustrated in Figure 1.2. Plantmicrobe interactions result in
intense biologicalprocesses in the rhizosphere. These intense
biological processes, in turn, affectphysicochemical reactions in
the rhizosphere. Physicochemical properties thatcan be different in
the rhizosphere include acidity, concentration of complex-ing
biomolecules, redox potential, ionic strength, moisture, and
nutrient status.In the rhizosphere, it is difÞcult to separate the
effects of microbial activity onthe chemistry of metals and
metalloids from the effects of plant root activity.Microorganisms
act in a fashion similar to that of plant roots in that they
canaccumulate metals and metalloids through uptake and adsorption
as well as mobi-lizing them through the action of microbial
exudates, diffusates, and excretions.
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INTRODUCTION 5
EPS material
bacterial cell
organic matter(humus)
sand particle
fungal hypha
clay crystal / platelet
capsule (EPS)
(a)
(c)
(b)
Mn+
−
+
−
silt particle
Figure 1.1. Interaction of bacteria and fungi with mineral
particles in a soil aggregate.Bacterial cells with a coat of
extracellular polysaccharides (EPSs) are enveloped by
clayparticles. The pore space where clays and bacteria interact,
bounded by silt- and sand-sizeparticles, is relatively enriched in
organic matter, including EPS residues. Fungal hyphaeare attached
to the outside surface of an aggregate. Inset shows an enlarged
view of abacterial cell with its complement of EPS. At normal soil
pH conditions, the cell has a netnegative surface charge. Most clay
particles adhere to the cell surface by bridging throughpolyvalent
cations, represented by Mn+ (a), although some may be attached
directly byelectrostatic interactions, either in face-to-face (b)
or edge-to-face (c) association. (FromTheng and Orchard, 1995.)
The total rhizosphere environment is governed by an interacting
trinity of thesoil, the plant, and the organisms associated with
the root (Lynch, 1990a,b), asillustrated in Figure 1.3.
Therefore, the role of physicochemicalbiological interfacial
interactions incontrolling the transformation, transport, fate, and
toxicity of metals and metal-loids in soil and surrounding
environments, especially the rhizosphere, which isthe bottleneck of
contamination of the terrestrial food chain, deserves increas-ing
attention. In this chapter we present an overview of this emerging
andextremely important area of science, to advance our knowledge of
the inter-face between physicochemical and biological reactions and
processes in theenvironment.
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6 IMPACTS OF PHYSICOCHEMICALBIOLOGICAL INTERACTIONS
10 20 30 40 50 60 700 800
200
150
100
50
0
400
300
200
100
Radial distance from root (mm)
Org
anis
ms
g−1
soll
× 10
−3
Fun
gig−
1
FungiBacteriaStreptomycetes
Figure 1.2. Distribution of organisms with distance from the
roots of 18-day-old lupin(Lupinus angustifolius L.). (From Rovira
and Davey, 1974.)
Plants
Rhizosphere
NutritionGrowth
Rhizodeposition
Organisms
GrowthInteractions
Nutrient Supply
Soil
NutrientsStructure
Water
Figure 1.3. Rhizosphere trinity. The total rhizospere
environment is determined by aninteracting trinity of the soil, the
plant, and the organism associated with the roots. (FromLynch,
1990a.)
1.2. MINERALORGANIC MATTERMICROORGANISMINTERACTIONS IN SOIL
ENVIRONMENTS
Interactions of soil minerals with organic matter and
microorganisms exert avital role in the formation of
short-range-ordered metal oxides, humic substances,mineral
colloidhumic complexes, aggregates, and the structure and porosity
ofsoils. These nonliving and living reactive components and the
structural stability
-
MINERALORGANIC MATTERMICROORGANISM INTERACTIONS 7
and associated nanoporosity of soils control the transformation,
transport, fate,and toxicity of metals and metalloids in the
environment.
1.2.1. Formation of Short-Range-Ordered Metal Oxides
Short-range-ordered Al and Fe oxides, especially nanoparticles,
are indeed amongthe most reactive components of acidic and neutral
soils (Bigham et al., 2002;Huang et al., 2002). In addition to
humic substances, biomolecules, which arepresent in root exudates,
microbial metabolites, and decomposition products ofbiological
tissues play a very signiÞcant role in inßuencing the formation
andtransformation of these metal oxides and the resulting
alteration of their surfaceproperties pertaining to the speciation,
transport, fate, and toxicity of metals andmetalloids in soil
environments (Huang and Violante, 1986; Schwertmann et al.,1986;
Sposito, 1996, 2004; Huang and Wang, 1997; Huang et al., 2002;
Violanteet al., 2002; Huang, 2004). Details of this issue are
treated by Violante et al., inChapter 5.
As the third most abundant element on Earths surface (after O
and Si), Alis a major element in all mineral soils. There are only
a few crystalline Aloxides, hydroxides, or oxyhydroxides, and only
one, gibbsite, occurs to any greatextent in soils. Aluminum,
however, also forms a series of highly reactive solublespecies and
poorly crystalline to noncrystalline mineral colloids (Figure
1.4).The mode depicted in the Þgure incorporates multiple reaction
paths. Reactionpath I is believed to be common when systems are
neutralized rapidly withinseconds or hours. Under these conditions,
little or no Al13 polynuclear species[AlO4Al12(OH)24(H2O)127+]
forms; the formation of Al(OH)3 nuclei is rapid, andgibbsite
appears within days or weeks of aging. Reaction paths II and III
bothinvolve the formation of Al13. Reaction path II is applicable
when systems areneutralized relatively slowly compared with
reaction path I. The individual Al13ions can remain in solution for
months to years, but eventually they transferby one of the three
pathways. If no Al13 nuclei are present, the soluble Al13ions can
slowly dissociate into Al3+ ions and deposit onto Al(OH)3 nuclei
(pathIIa). These soluble Al13 may also aggregate and form Al13
nuclei (path IIb). Ifsome Al13 nuclei are already present, the
remaining Al13 ions can be depositedon them within weeks and months
(path IIc). Path III is applicable when Al13forms under conditions
that promote the rapid formation of Al13 aggregates viaan anion
bridging mechanism (i.e., outer-sphere associations). These
aggregatesrearrange themselves rapidly into Al13 nuclei. The Al13
nuclei in paths IIb, IIc,and III then transform into a poorly
ordered phase, microcrystalline boehmite(pseudoboehmite), which
then transforms into gibbsite. The relative importanceof each
pathway depends greatly on reaction conditions. These soluble Al
speciesand poorly ordered to noncrystalline Al species formed in
the reaction pathwaysare highly reactive and thus important in
inßuencing reactions and processes in theenvironment. The
transformation of Al via the various pathways described aboveare
strongly inßuenced by the nature and concentration of solution
inorganicand organic ions and solid-state ions such as clay
minerals and humic substances
-
8 IMPACTS OF PHYSICOCHEMICALBIOLOGICAL INTERACTIONS
[Al(OH)3]nuclei
intermediate
gibbsite
(als
o ba
yerit
e)in
term
edia
te
poorly orderedphase
slowfastslow
[Al13] nuclei
[Al13]aggregates
[Al13]aggregates
[Al13] nuclei
very slow
llc
llb
lla
solubleAl13
fast
Al3+
+OH−
path
l
path ll
path lll
slowAl
3+
Figure 1.4. Reaction scheme proposed for Al hydroxide mineral
formation fromhydrolyzed Al solution. (ModiÞed from Bertsch and
Parker, 1996; Huang et al., 2002.)
(Huang and Violante, 1986, Huang, 1988; Bertsch and Parker,
1996; Krishnamurtiet al., 1999, 2004; Huang et al., 2002).
Organic substances such as fulvic acid (FA) and humic acid (HA)
and manylow-molecular-mass organic acids (LMMOAs) form stable
complexes with Aland disrupt the crystallization of Al hydroxides
and thus promote the forma-tion of short-range-ordered (SRO) Al
hydroxides (Kwong and Huang, 1975,1979a,b, 1981; Lind and Hem,
1975; Kodama and Schnitzer, 1980; Violanteand Huang, 1985; Singer
and Huang, 1990; Violante et al., 2002; Colomboet al., 2004).
Organics greatly inßuence the surface properties of Al
transfor-mation products. For instance, the presence of organic
acids during aging ofAl hydroxide gels for 40 days increases the
speciÞc surface of the precipitationproducts up to 30-fold over
that of the control and higher acid concentrationsresults in higher
speciÞc surfaces (Table 1.1). The surface charge characteristicsof
the precipitation products are also altered dramatically (Figure
1.5). TheseSRO transformation products of Al should thus exert
substantial inßuence on theadsorptiondesorption, transformation,
and dynamics of metals and metalloidsin the environment.
Interactions of soil minerals with organic substances and
microorganismshave a great impact on the formation and
transformation of SRO Fe oxides(Schwertmann et al., 1986; Cornell
and Schwertmann, 2003). Microorganismsmay inßuence Fe
transformation through reduction and oxidation reactions. Soil
