Trace Metals in Aquatic Systems

440 Pages·2013·19.5 MB·English

by  Robert P. Mason(auth.)

Trace Metals in
Aquatic Systems
Trace Metals in
Aquatic Systems
Robert P. Mason
Departments of Marine Sciences and Chemistry
University of Connecticut Avery Point, Groton, CT, USA
A John Wiley & Sons, Ltd., Publication
This edition first published 2013 © 2013 by Robert P. Mason
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Library of Congress Cataloging-in-Publication Data
Mason, Robert P. (Robert Peter), 1956–
Trace metals in aquatic systems / Robert P. Mason.
pages cm
Summary: “The textbooks that currently exist do not deal with this particular subject in a
comprehensive fashion, and therefore this book is being proposed to full this gap” – Provided
by publisher.
Includes bibliographical references and index.
ISBN 978-1-4051-6048-3 (hardback)
1. Trace elements–Analysis. 2. Water–Analysis. 3. Water chemistry. I. Title.
QD142.M316 2013
553.7–dc23
2012038420
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1 2013
Contents
Preface, ix
About the companion website, x
1 Introduction, 1
1.1 A historical background to metal aquatic chemistry, 1
1.2 Historical problems with metal measurements in environmental media, 5
1.3 Recent advances in aquatic metal analysis, 9
References, 10
Problems, 12
2 An introduction to the cycling of metals in the biosphere, 13
2.1 The hydrologic cycle, 13
2.2 An introduction to the global cycling of trace metal(loid)s, 15
2.2.1 The sources and cycling of metal(loid)s in the biosphere, 15
2.2.2 Metal(loid) partitioning and solubility in natural waters, 16
2.2.3 Human influence over metal(loid) fate and transport, 19
2.2.4 Trace metal(loid) inputs to the atmosphere, 25
2.2.5 Metal(loid)s in the terrestrial environment and freshwater ecosystems, 26
2.2.6 The transport of metal(loid)s to the ocean, 30
2.2.7 Trace metal(loid)s in ocean waters, 33
2.2.8 Trace metal(loid) inputs from hydrothermal vents, 36
2.3 Global cycles of some important trace metals, 38
2.3.1 The global cycles of cadmium, copper, and zinc, 39
2.3.2 The global cycle of mercury and lead, 41
2.4 Chapter summary, 44
References, 44
Problems, 47
3 Chemical thermodynamics and metal(loid) complexation  
in natural waters, 49
3.1 Thermodynamic background for understanding trace metal(loid) complexation, 49
3.1.1 The relationship between free energy and the equilibrium constant, 51
3.1.2 Ionic strength effects, 52
3.1.3 Thermodynamic equilibrium, kinetics and steady state, 54
3.2 Bonding, electronic configuration, and complex formation, 55
3.2.1 Ligand Field Theory, 58
3.2.2 Thermodynamic effects of orbital splitting, 61
3.2.3 Inorganic chemistry and complexation of transition metals, 62
3.2.4 Inorganic chemistry and complexation of non-transition metals and metalloids, 65
3.3 Complexation of metals in solution, 67
3.3.1 Inorganic complexation, 67
3.3.2 An approach to determining metal(loid) speciation in solution, 68
3.3.3 The chemistry and speciation of metal-binding ligands, 72
3.3.4 The complexation of the major ions in solution, 77
3.3.5 Metal complexation with low molecular weight organic ligands, 79
3.3.6 Complexation to large molecular weight organic matter, 81
3.4 Trace metal interactions with the solid phase, 86
3.4.1 Precipitation and dissolution, 86
3.4.2 Adsorption of metals to aqueous solids, 90
3.4.3 Dissolved-particulate partition coefficients, 91
v
vi   Contents
3.4.4 Adsorption isotherms, 92
3.4.5 A complexation-based model for adsorption, 93
3.5 Redox transformations and thermodynamic calculations, 102
3.5.1 Electrochemistry and the equilibrium constant, 102
3.5.2 The range in electrode potential and the stability of water, 104
3.5.3 Equilibrium calculations involving redox reactions, 105
3.5.4 Environmental considerations and controlling reactions, 108
3.6 Chapter summary, 112
Appendix 3.1, 114
References, 120
Problems, 121
4 Modeling approaches to estimating speciation and interactions in aqueous 
systems, 123
4.1 Introduction, 123
4.2 The underlying basis and application of chemical equilibrium models, 126
4.3 Adsorption modeling, 131
4.4 Modeling interactions between cations and organic matter, and inorganic surfaces, 144
4.4.1 The WHAM modeling approach, 144
4.4.2 The NICA-Donnan modeling framework, 149
4.4.3 Modeling the adsorption of humic acids to surfaces and the interaction
with metal(loid)s, 151
4.5 Modeling redox transformations, 152
4.6 Modeling the kinetics of reactions, 155
4.6.1 Reactions in solution, 155
4.6.2 Adsorption/desorption kinetics, 160
4.6.3 Uptake kinetics for microorganisms, 160
4.7 Incorporating kinetics and thermodynamics into fate and transport
modeling, 161
4.8 Chapter summary, 162
Appendix 4.1, 162
Appendix 4.1a, 162
Appendix 4.1b, 163
References, 163
Problems, 165
5 Metal(loid)s in the atmosphere and their inputs to  
surface waters, 167
5.1 Introduction, 167
5.2 Atmospheric transport and deposition, 167
5.2.1 Dry deposition, 167
5.2.2 Aerosol distributions and metal(loid) concentrations, 172
5.2.3 Wet deposition, 177
5.2.4 Atmospheric deposition fluxes, 181
5.2.5 Source apportionment of atmospheric metal(loid)s, 185
5.2.6 Gaseous volatilization and gas exchange of metal(loid) compounds, 189
5.3 Atmospheric chemistry and surface water photochemistry of metals, 194
5.4 Solubilization of aerosol metal(loid)s in natural waters, 198
5.5 Focus topics, 200
5.5.1 Focus topic: Atmospheric inputs and atmospheric chemistry of iron, 200
5.5.2 Atmospheric chemistry and air–water exchange of mercury, 202
5.6 Inputs of atmospheric metals to the biosphere, 206
5.7 Chapter summary, 209
References, 209
Problems, 217
Contents   vii
6 Trace metal(loid)s in marine waters, 219
6.1 Introduction, 219
6.2 Metal(loid) partitioning in coastal and open ocean waters, 221
6.2.1 The mechanisms of partitioning, 221
6.2.2 Examination of metal speciation in the particulate phase, 227
6.2.3 Examination of the complexation of metals with natural ligands in the filtered
fraction, 232
6.2.4 Metal concentrations in coastal waters, 237
6.3 Metals in coastal and offshore sediments, 238
6.3.1 Metals in the bulk phase, 238
6.3.2 Metals in sediment porewater, 243
6.3.3 Modeling metal cycling in sediments, 249
6.3.4 Modeling of metal speciation in marine sediment porewaters, 255
6.3.5 The importance of sediment resuspension and extreme events in coastal metal
dynamics, 259
6.3.6 Deep ocean sediments and manganese nodules and accretions, 264
6.3.7 The biogeochemistry of metals in hydrothermal systems, 267
6.4 Metal distributions in open ocean waters, 270
6.4.1 Vertical distribution of metal(loid)s and controlling factors, 270
6.4.2 Coordinated ocean studies: GEOTRACERS and prior and related
programs, 275
6.4.3 Iron, manganese, and aluminum cycling in open ocean waters, 279
6.4.4 The biogeochemical cycling of zinc and cadmium in the ocean, 280
6.4.5 Copper, cobalt, and other nutrient transition metals in the oceans, 282
6.4.6 Anthropogenic metals – lead, silver, and mercury, 283
6.4.7 Metalloids and other oxyanion cycling in seawater, 290
6.4.8 Other transition metals, the lanthanides, and actinides, 292
6.4.9 Particulate metal fluxes to the deep ocean, 294
6.5 Chapter summary, 297
References, 298
Problems, 307
7 Trace metals in freshwaters, 310
7.1 Overview of metal cycling in freshwaters, 310
7.2 Trace element cycling in lakes, 313
7.2.1 Processes influencing metal(loid) fate and dissolved speciation in lakes, 314
7.2.2 Modeling the speciation and association of trace elements in stratified
systems, 327
7.2.3 Focus topic: Mercury cycling in lakes, 330
7.3 Trace elements in rivers and groundwater, 336
7.3.1 Trace elements in rivers, 336
7.3.2 Trace elements in groundwater, 345
7.3.3 Focus topic: Mining impacts and acid mine drainage, 348
7.3.4 Arsenic in surface water and groundwater, 350
7.3.5 Metal inputs from groundwater and margin exchange processes, 354
7.4 Human activities and their impact on trace metal(loid) concentrations in drinking water and
receiving waters, 356
7.4.1 Lead in drinking water, 357
7.4.2 Metal inputs from waste water treatment facilities and other industrial
discharges, 358
7.5 Metal stable isotopes and their use, 360
7.6 Chapter summary, 363
References, 364
Problems, 368
viii   Contents
8 Trace metals and organisms: Essential and toxic metals, organometallics, 
microbial processes, and metal bioaccumulation, 370
8.1 Introduction, 370
8.2 Mechanisms of metal accumulation by microorganisms, 372
8.2.1 The transport of metals across membranes, 372
8.2.2 Passive transport (diffusion), 373
8.2.3 Facilitated transport (accelerated diffusion), 377
8.2.4 Active uptake, 380
8.3 Essential trace metals, 381
8.3.1 An overview of essential trace metals, 381
8.3.2 Focus topic: Iron uptake by microbes in marine waters, 383
8.3.3 Focus topic: Transition metals and carbon fixation by microbes, 388
8.3.4 The biochemistry of metals and their presence in the early biosphere, 391
8.4 Organometallic compounds and microbial transformations of metals, 393
8.4.1 Mechanisms of metal methylation, 393
8.4.2 Less common organometallic compounds, 397
8.4.3 Alkylated mercury compounds, 399
8.4.4 Lead and tin compounds, 402
8.4.5 Organometallics of arsenic, antimony, and bismuth, 404
8.5 Bioavailability and bioaccumulation, 406
8.5.1 Introduction, 406
8.5.2 Trophic transfer of metals, 408
8.5.3 Exposure and bioaccumulation models, 410
8.6 Chapter Summary, 414
References, 415
Problems, 421
Index, 422
Preface
This book is an outgrowth of a number of courses I have While the book has almost 1000 references this is clearly the
taught over the last seven years at the University of tip of the publication “iceberg”. I have referred to the primary
Connecticut. While written as an upper level text, it should literature except in cases when there was a high quality
also be useful to environmental scientists interested in trace recent compilation chapter or review article. The reader is
elements in aquatic systems. Much of the information is encouraged to examine the references within these reviews.
derivative from a class in Environmental Chemistry that I I am sure that some readers may not understand why I did
introduced and later taught with Ron Siefert within the not cite their work, but I endeavored to remove bias in the
University of Maryland Center for Environmental Science. choice of citations. The book was an undertaking of many
Readers will see the influences of my graduate and post-doc years and so the citations reflect the order the chapters were
mentors, Bill Fitzgerald, Francois Morel and Harry Hemond, written, which was not totally chronological. Where possi-
in the book’s focus, and my exposure to books such as ble, I used examples from locations around the world.
Broecker and Peng Tracers in the Sea, Stumm and Morgan I thank Stan Wakefield and Ian Francis for helping me get
Aquatic Chemistry and Morel and Hering Principles and connected with the publisher about 6 years ago and for the
Applications of Aquatic Chemistry, and their related texts. These help of many people at Blackwell during the process of
excellent primary texts have been supplemented in recent publication. I thank the reviewers of the original book pro-
years by many other books, including compilations such as posal for their comments that helped frame the content. I
the Treatise on Geochemistry, but I always find myself con- especially thank two anonymous reviewers for their com-
stantly referring to the earlier works. In studies of trace ments on the first complete draft of the book. This was a tall
metals and metalloids one must always reflect on the under- order that they did with diligence and their comments were
lying principles which are easy to forget, especially if an very useful. I also thank those who read sections of the
element is studied in isolation. book, or helped with the editing, especially Elsie Sunderland,
Much of my graduate work focused on making precise Brian DiMento and Amina Schartup. Also, I acknowledge
and accurate measurements of mercury speciation in the support from the University of Connecticut Small Grant
ocean and freshwaters, which solidified my appreciation for Program for student support for the book compilation and
the care and rigor needed for environmental research. These also for funds to help cover the costs of obtaining permission
pursuits took me to the equatorial Pacific in late 1989, and to reuse figures. Obtaining permissions, and the associated
important research findings. Many other journeys, including costs, are an unfathomable detour along the road to publica-
oceanic cruises in the Atlantic and Pacific, and studies in tion even given the advances of the electronic age. I will
small and large lakes and in the atmosphere, are what deliv- endeavor in the future to make figures in my publications
ered me to where I am today, and the contents of this book. as clear as possible as even with electronic tools it is not
I acknowledge the many students who have helped me always easy to reproduce figures already in the literature.
refine my teaching approach and improve the delivery of I never thought it would take this long, but it did. This
the often complex messages relating to the biogeochemical lack of foresight is probably a good thing as I am sure my
cycling of elements in aquatic systems, which is reflected in wife Joan would have been less enthusiastic had she known
the book. There is obviously more emphasis on certain ele- the truth. I thank her for her support through the process.
ments over others, but I have endeavored to focus on a The book writing occurred in stages and that may be evident
particular topic because of its biogeochemical importance to the reader, and was interrupted by the realities of aca-
and potential impact on humans and the environment, demic life. For example, three of my PhD students have
rather than because of personal bias. I hope that I have suc- graduated since I started the book, and much new research
ceeded as it is not possible to cover all topics in detail within has come to light, which was an ongoing challenge to try
the page limits of the publisher, or in a book suitable as a and keep the text as current as possible. I hope to have suc-
one semester course. In this vein, I have chosen focus topics ceeded in this. Enjoy.
in the latter chapters as examples demonstrating chemical
principles and focusing on problems of global importance. Robert P. Mason
ix
About the companion website
This book is accompanied by a companion website:
www.wiley.com/go/mason/tracemetals
The website includes:
• Powerpoints of all figures from the book for downloading
• PDFS of tables from the book
• Answers to end of Chapter Problems
x
CHAPTER 1
Introduction
1.1 A historical background to metal  tion (weathering) of the terrestrial crust and the flow of
aquatic chemistry freshwater to the ocean transports these dissolved salts, as
well as suspended particulate matter, entrained and resus-
In terrestrial waters, much of the initial work by environ- pended during transport. However, the ratio of river to
mental engineers and scientists was aimed at understanding ocean concentration is not fixed for all dissolved ions [3, 4]
the processes of waste water treatment, and of the reactions as the concentration in the ocean is determined primarily
and impact of human-released chemicals on the environ- by the ratio of the rate of input compared to the rate of
ment, and on the transport and fate of radioactive chemicals. removal, which will be equivalent at steady state. Thus, the
This initial interest was driven by the need to understand ocean concentration of a constituent is related to its reactiv-
industrial processes and the consequences of these activities, ity, solubility or other property that may control its rates of
and the recognition of the potential toxicity and environ- input or removal [1, 5].
mental impact of trace metals released during extraction Many of the early investigations looked at the aquatic
from the Earth as well as during refining and use. Initial ecosystem as an inorganic entity or reactor, primarily based
interest in the chemistry of the ocean was driven by the on the assumption that aquatic chemistry was driven by
key question of why the sea is salty. Of course, it is now abiotic chemical processes and reactions, and that the impact
known that freshwaters, and even rainwater, contain a small of organisms on their environment was relatively minor.
amount of dissolved salts; and that the high salt content of In 1967, Sillen [6], a physical chemist, published a paper
the ocean, and some terrestrial lakes, is due to the buildup The Ocean as a Chemical System, in which he aimed at explain-
of salts as a result of continued input of material to a rela- ing the composition of the ocean in terms of various equi-
tively enclosed system where the major loss of water is due librium processes, being an equilibrium mixture of so-called
to evaporation rather than outflow. This is succinctly stated “volatile components” (e.g., H2O and HCl) and “igneous
by Broecker and Peng [1]: “The composition of sea salt rock” (primarily KOH, Al(OH)3 and SiO2), and other com-
reflects not only the relative abundance of the dissolved ponents, such as CO2, NaOH, CaO and MgO. His analysis
substances in river water but also the ease with which a was a follow-up of the initial proposed weathering reaction
given substance is entrapped in the sediments”. of Goldschmidt in 1933:
The constituents in rivers are derived from the dissolu-
0.6 kg igneous rock+~1 kg volatiles=1 L sea water
tion of rocks and other terrestrial material by precipitation (1.1)
+~0.6 kg ssediments+3 L air
and more recently, through the addition of chemicals from
anthropogenic activities, and the enhanced release of par- Sillen stated that “the composition may . . . be given by
ticulate through human activity. The dissolution of carbon well-defined equilibria, and that deviations from equilib-
dioxide (CO ) in rainwater results in an acidic solution and rium may be explainable by well-defined processes”, and
2
this solution subsequently dissolves the mostly basic con- proposed the box model shown in Fig. 1.1 [6]. However, he
stituents that form the Earth’s crust [2]. The natural acidity, also stated that this did not “mean that I suggest that there
and the recently enhanced acidity of precipitation due to would be true equilibrium in the real system”. In reality,
human-derived atmospheric inputs, results in the dissolu- the ocean composition is a steady state system where the
Trace Metals in Aquatic Systems, First Edition. Robert P. Mason.
© 2013 Robert P. Mason. Published 2013 by Blackwell Publishing Ltd.
1