Environmental Electrochemistry In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002. In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002. ACS SYMPOSIUM SERIES 811 Environmental Electrochemistry Analyses of Trace Element Biogeochemistry Martial Taillefert, EDITOR Georgia Institute of Technology Tim F. Rozan, EDITOR University of Delaware American Chemical Society, Washington, DC In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002. Library of Congress Cataloging-in-Publication Data Environmental electrochemisty : analyses of trace element biogeochemistry / Martial Taillefert, editor, Tim F. Rozan, editor. p. cm.—(ACS symposium series; 811) Includes bibliographical references and index. ISBN 0-8412-3774-3 (alk. paper) 1. Environmental chemistry—Congresses. 2. Electrochemistry—Congresses. 3. Trace elements—Environmental aspects—Congresses. I. Taillefert, Martial, 1967 - II. Rozan, Tim F., 1964 - III. American Chemical Society. Division of Environmental Chemistry. IV. American Chemical Society. Meeting (220th: 2001 : Washington, D.C.). V. Series. TD193.E553 2002 628.01'54137—dc21 2001053392 The paper used in this publication meets the minimum requirements of American National Standard for Information Sciences—Permanence of Paper for Printed Library Materials, ANSI Z39.48-1984. Copyright © 2002 American Chemical Society Distributed by Oxford University Press All Rights Reserved. Reprographic copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Act is allowed for internal use only, provided that a per- -chapter fee of $20.50 plus $0.75 per page is paid to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. 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PRINTED IN THE UNITED STATES OF AMERICA In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002. Foreword The ACS Symposium Series was first published in 1974 to provide a mechanism for publishing symposia quickly in book form. The purpose of the series is to publish timely, comprehensive books developed from ACS sponsored symposia based on current scientific research. Occasion- -ally, books are developed from symposia sponsored by other organiza- -tions when the topic is of keen interest to the chemistry audience. Before agreeing to publish a book, the proposed table of contents is reviewed for appropriate and comprehensive coverage and for interest to the audience. Some papers may be excluded to better focus the book; others may be added to provide comprehensiveness. When appropriate, overview or introductory chapters are added. Drafts of chapters are peer- reviewed prior to final acceptance or rejection, and manuscripts are prepared in camera-ready format. As a rule, only original research papers and original review papers are included in the volumes. Verbatim reproductions of previously published papers are not accepted. ACS Books Department In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002. Preface Electrochemistry has been used extensively in the past three decades to determine the chemical composition of environmental samples from the water column, sediments, soils, biofilms, and microbial mats. These electrochemical methods have many advantages over other analytical techniques for environmental research: (1) the techniques are non-destructive, which minimize sample perturbation, (2) the data can be collected rapidly and reproducibly, (3) the detection limits have appropriate sensitivity for most environmental applications, (4) direct information on the chemical speciation can be obtained, (5) the instrumentation can be very compact, which is attractive for field deployment, and (6) the electrochemical sensors can be miniaturized, allowing for non-invasive in-situ sampling. For these reasons, electrochemical methods are extremely useful tools for understanding complex natural biogeochemical processes, however, the present literature lacks a comprehensive publication, which details the current multidisciplinary uses of electrochemistry in natural environments. The goal of this American Chemical Society (ACS) Symposium Series publication is to demonstrate the usefulness of electrochemical methods in environmental research. The chapters are based on a Symposium on Electrochemical Methods for the Environmental Analysis of Trace Element Biogeochemistry that was organized at the 200th ACS National Meeting in Washington, D.C. in August 2000. The chapters present instrumental designs and techniques currently being employed by researchers and cover a wide range of environmental applications including trace metal measurements in the water column of freshwater and marine environments, redox chemical species at hydrothermal vents, in anoxic water bodies, sediments and microbial mats, major cations and anions in extraterrestrial systems, metal complexing properties of natural waters, and mineral-water interface processes. The book is targeted to all scientist whose goal is to better understand trace element cycling in aquatic systems, including environmental chemists and engineers, geochemists, soil scientists, marine chemists, and environmental microbiologists who require tools to characterize the chemistry of microbial environments. To cover this wide array of interests we have divided the book's 19 chapters into six sections: (1) development and application of electrochemical techniques for in-situ measurements in the water column of lakes, rivers, and xi In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002. oceans; (2) development and application of electrochemical techniques for on- -line measurements in the water column of lakes, rivers, and oceans; (3) development and application of electrochemical techniques for in-situ measurements at the sediment-water interface in lakes and marine systems; (4) applications of electrochemical techniques for sediment and microbial mat measurements; (5) novel electrochemical technologies in development or destined to be utilized in extraterrestrial environments; and (6) recent applications of electrochemical techniques for metal complexation studies. Each section comprises a number of different research examples where a variety of analytical techniques (voltammetric, potentiometric, amperometric) have successfully been used to help understand biogeochemical processes in diverse environments. Chapters were categorized according to their main focus, and some may apply to more than one section. Therefore, we encourage the reader to consult each individual chapter. Acknowledgments The editors are grateful to the authors for their outstanding contributions, to the referees who contributed significantly to the quality of this book by reviewing each chapter, and finally to the acquisitions staff of the ACS Books Department. Special thanks to Anne Wilson and Kelly Dennis for their patience and support during the acquisition of this book and to Margaret Brown for editing and production. Martial Taillefert School of Earth and Atmospheric Sciences Georgia Institute of Technology Atlanta, GA 30332-0340 Tim Rozan College of Marine Studies University of Delaware Lewes, DE 19958-1298 xii In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002. Chapter 1 Electrochemical Methods for the Environmental Analysis of Trace Elements Biogeochemistry Martial Taillefert 1 and Tim F. Rozan 2 1 School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 221 Bobby Dodd Way, Atlanta, GA 30332 2 ColIege of Marine Sciences, University of Delaware, 700 Pilottown Road, Lewes, DE 19958 Since the 1970's, when the first in situ measurements of oxygen in the oceans were reported, the development of electrochemical methods for the analysis of trace element biogeochemistry in the environment has significantly improved. From conductimetry to measure salinity, to amperometric and potentiometric sensors that can measure a single analyte, to voltammetric sensors that can measure several species during the same scan, a variety of electrochemical techniques have been utilized to better understand biogeochemical processes in the environment. These techniques have been integrated into a variety of devices for laboratory experimentation and in situ deployment (or online measurements). The development of microsensors has significantly contributed to the application of these techniques in sediments, biofilms, and microbial mats, where data can now be collected at the micrometer scale. Electrochemical techniques have also been adapted to measure the chemical speciation of trace elements in natural environments following physical and chemical separations. Finally, the complexation properties of most naturally occurring ligands have been determined by electrochemical measurements performed on synthetic and natural samples. This first chapter is intended to familiarize the reader with the electrochemical terminology, techniques, current applications, and future directions in environmental chemistry and biogeochemistry research. 2 © 2002 American Chemical Society In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002. 3 Electrochemical Techniques and Sensors Potentiometry In potentiometry, the difference of potential between two electrochemical cells is measured with a high impedence voltmeter in the absence of appreciable currents. The difference in potential is measured between a reference electrode, usually a Ag/AgCl or a Hg/HgCl 2 electrode, and an indicator electrode. The boundary potential, or the difference in potential between the external and the internal solution at the indicator electrode, is sensitive to the activity of ions according to the Nernst equation. Potentiometric sensors commonly used in the environment include membrane electrodes to determine the pH (1-3), or S 2 " (4-6), molecular electrodes to determine pC0 2 (3, 7), and ion selective electrodes (ISEs) to determine N0 3 " (5-70), N0 2 " (10, 11), NH 4 + (10, 12), Ca 2+ (10), C0 3 2 ' (10), or free metal activities (13, 14). Unfortunately, interferences prevent the use of N0 3 " and NH 4 + electrodes in marine environments. Finally, the detection limits of ISEs are usually not suitable for the determination of free metals in natural environments, but the recent development of polymer membrane ISEs (75,16) is promising to increase their sensitivity. Coulometry Coulometry is based on the oxidation and reduction of an analyte for a sufficient period of time to assure its quantitative conversion to a new oxidation state. Two coulometric methods are used to analyze environmental samples: chronopotentiometry and chronoamperometry. In chronopotentiometry, an element is electrolytically preconcentrated at an electrode and the potential is recorded at a reference electrode as a function of time upon addition of a chemical reactant (17, 18) or application of a constant current (e.g., 19, 20). The first technique, called potentiometric stripping analysis (PSA), is usually used to analyze trace metals in freshwater (21) and seawater (22), as well as for metal complexation studies (23). The second technique, called constant current stripping analysis (CCSA), has been used to analyze trace metal concentrations in aquatic systems (19, 20). In chronoamperometry, an element is electrolytically preconcentrated at an electrode by applying a constant potential and the current of the reaction is simultaneously recorded at an auxiliary electrode as a function of time (24). To our knowledge, the application of chronoamperometry for the analysis of In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002. 4 environmental samples is limited. A chronoamperometric method has been used to measure organic compounds in the environment (25), and recently, a biosensor has been developed to determine NH 4 + by the intermediate of a chronoamperometric measurement of NADH involved with NH 4 + in the reduction of an enzyme (26). Amperometry In amperometry, the current is measured at an auxiliary electrode when a constant potential is applied between a reference electrode, usually silver/silver chloride, and the indicative electrode. The most common amperometric sensor is the oxygen electrode, or Clark electrode (27, 28), which has been routinely deployed to measure concentrations of oxygen in aquatic systems (e.g, 4, 28-34). Another amperometric sensor has been built to detect N 2 0 in biofilms (35). Recently, bioelectrochemical sensors have been developed to measure N0 3 " in marine sediments (36) and CH 4 in sediments and biofilms (37). These biosensors use a N 2 0 microelectrode (35) and an oxygen microelectrode (4), respectively, as indirect electrochemical detector. The N0 3 " biosensor contains a microbial community between a membrane and the N 2 0 electrode which reduces N0 3 " and N0 2 " to N 2 0. This biosensor does not suffer from chloride interference and can be used in marine environments. The CH 4 biosensor contains aerobic methane oxidizers which consume 0 2 . The decrease in 0 2 is inversely proportional to the CH 4 concentration. An amperometric microsensor has been developed for on-line measurements of H 2 S (38, 39). Dissolved sulfide is detected indirectly by measuring the reoxidation current of ferrocyanide produced by sulfide reduction of ferricyanide. In contrast to potentiometric sensors, this electrode does not suffer from oxygen interferences because oxygen does not react with ferricyanide. Voltammetry In voltammetry, the potential is ramped between a working electrode and a reference electrode. At a particular potential, the analyte is oxidized or reduced at the working electrode and the current resulting from this reaction is measured at an auxiliary electrode. Voltammetric techniques are attractive to measure chemical species in the environment because they can detect several analytes in the same potential scan, they have low detection limits, and generally do not suffer from matrix problems (e.g., high salinity) (40). Voltammetry in the environment is mostly used with mercury electrodes, because their analytical In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002. [...]... presented in Chapter 19 2 3 2 2 3 Future Directions Electrochemistry is a continuously growing field and new techniques and methods keep emerging from the literature As a result, environmental chemists, chemical oceanographers, and microbiologists are constantly improving their techniques to study biogeochemical and environmental processes With In Environmental Electrochemistry; Taillefert, M., et al.; ACS... documented in Chapter 14 and in microbial mats in Chapter 12 and 15 2 3 2 2 + 2 2 3 2 4 2+ 2 2 3 2 2 2+ 2 2+ (aq In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002 8 New technologies in electrochemistry New technologies in electrochemistry include the recent development and application of bioelectrochemical sensors to monitor chemical... cathodic stripping voltammetry: AdCSV) 2 2 8 2+ x aq 2 2+ 2 2 2 3 4 6 2+ 2 2 2 2 3 2 4 6 Environmental Applications In situ measurements in water bodies In situ measurements are needed to determine the chemical composition of water bodies because the chemical speciation can be altered when a sample is In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society:... 2583-2589 In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002 11 14 Mousavi, M F.; Sahari, S.; Alizadeh, N.; Shamsipur, M Anal Chim Acta 2000, 414, 189-194 15 Sokalski, T.; Ceresa, .; Zwickl, T.; Prestch, E J Am Chem Soc 1997, 119, 11347-11348 16 Bakker, E.; Pretsch, E Trends Anal Chem 2001, 20, 11-19 17 Jagner, D In Marine electrochemistry; ... control of the system components The main characteristics of the microsensors and probes are summarized and their analytical /environmental features illustrated with examples of laboratory characterization and in situ applications 16 â 2002 American Chemical Society In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002 17 Introduction... given stoichiometry Such measurements have been performed by ASV with Cu (e.g., 68-72), Cd (68-71), Pb (e.g., 69-71, 73), and Zn (69, 70) or by competitive ligand-exchange ASV (CLE-ASV) with In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002 9 Cu (69, 74, 75), Pb (75), Cd (76-77), and Zn (78) or competitive ligandexchange... Oceanogr 1991, 36, 1476-1480 34 Wieland, .; Kỹhl, M Mar Ecol Prog Ser 2000, 196, 87-102 35 Revsbech, N P.; Nielsen, L P.; Christensen, P B.; Sorensen, J App Environ Microb 1988, 54, 2245-2249 In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002 12 36 Larsen, L H.; Kjaer, T.; Revsbech, N P Anal Chem 1997, 69, 35273531 37 Damgaard,... Stierli, R.; Wehrli, B Limnol Oceanogr 1998, 43, 1728-1733 60 Brendel, P J.; Luther III, G W Environ Sci Technol 1995, 29, 751-761 61 Rickard, D.; Olroyd, .; Clamp, A Estuaries 1999, 22, 693-701 In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002 13 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87... Nelson, .; Mantoura, R F C J Electroanal Chem 1984, 164, 253-264 Croot, P L.; Moffett, J W.; Luther III, G W Mar Chem 1999, 67, 219232 Town, R M.; Filella, M J Electroanal Chem 2000, 488, 1-16 In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002 14 89 90 91 92 Van den Berg, C M G Analyst 1992, 117, 589-593 Filella, M.; Town,... Kogut, M B Mar Chem 2001, in press Buffle, J.; Altmann, R S.; Filella, M.; Tessier, A Geochim Cosmochim Acta, 1990, 54, 1535-1553 93 Town, R.; Filella, M Limnol Oceanogr 2000, 45, 1341-1357 In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002 Chapter 2 Submersible Voltammetric Probes for Real-Time Continuous Monitoring of . Environmental Electrochemistry In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002. In Environmental Electrochemistry; . In Environmental Electrochemistry; Taillefert, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2002. Library of Congress Cataloging-in-Publication Data Environmental . references and index. ISBN 0-8412-3774-3 (alk. paper) 1. Environmental chemistry—Congresses. 2. Electrochemistry Congresses. 3. Trace elements Environmental aspects—Congresses. I. Taillefert, Martial,