Environmental Chemistry

239 Pages·1985·6.56 MB·English

by  Peter O’Neill (auth.)

Environmental Chemistry
TITLES OF RELATED INTEREST
Formation of soil material
T. R. Paton
The interpretation of igneous rocks
K. G. Cox et af.
The inaccessible Earth
G. C. Brown & A. E. Mussett
Pedology
P. Duchaufour
Man-environment processes
D. Drew
Geology and man
1. Watson
Groundwater as a geomorphic agent
R. G. LaFleur (ed.)
Environmental systems
1. D. White et al.
Introducing groundwater
M. Price
Environmental magnetism
R. Thompson & F. Oldfield
Environmental
Chemistry
PETER O'NEILL
Principal Lecturer in Environmental Chemistry,
Department of Environmental Sciences,
Plymouth Polytechnic
London
GEORGE ALLEN & UNWIN
Boston Sydney
© P. O'Neill, 1985
Softcover reprint of the hardcover 1st edition 1985
This book is copyright under the Berne Convention. No reproduction
without permission. All rights reserved.
George Allen & Unwin (Publishers) Ltd,
40 Museum Street, London WClA lLU, UK
George Allen & Unwin (Publishers) Ltd,
Park Lane, Hemel Hempstead, Herts HP2 4TE, UK
Allen & Unwin Inc.,
Winchester Place, Winchester, Mass 01890, USA
George Allen & Unwin Australia Pty Ltd,
8 Napier Street, North Sydney, NSW 2060, Australia
First published in 1985
British Library Cataloguing in Publication Data
O'Neill, Peter
Environmental chemistry.
I. Environmental chemistry
I. Title
574.5 QD31.2
ISBN 978-94-010-9320-0 ISBN 978-94-010-9318-7 (eBook)
DOl 10.1007/978-94-010-9318-7
Library of Congress Cataloging in Publication Data
O'Neill, Peter.
Environmental chemistry.
Bibliography: p.
Includes index.
1. Environmental chemistry. I. Title.
TDl93.054 1985 628.5 85-11082
Set in 10 on 12 point Times by Mathematical Composition Setters Limited
7 Ivy Street, Salisbury, Wiltshire, England
and printed in Great Britain by Mackays of Chatham
PREFACE
The two terms 'environmental chemistry' and 'pollution' often
seem to go together, yet environmental chemistry is much more
than the study of the chemical effects of pollution. In this book I
have attempted to emphasise the natural mobility of the elements
and their compounds. Only by understanding these normal
movements can we begin to appreciate the changes - good or bad
- that human activities can bring about.
The breakdown of rock to form soils, the uptake of the mobi
lised chemicals by plants, and the return of the dead plant material
to the soil ready for further uptake has long been known as a
'biogeochemical' cycle (indicating the interaction of biology,
geology and chemistry). The biogeochemical cycle is only one part
of the general geochemical cycle in which material is moved from
the land to the sea, possibly having entered the atmosphere, and
then being reincorporated in the land mass. The elements move
through their cycles in fits and starts, with many variations in
chemical form occurring along the way. Environmental chemistry
attempts to explain why a specific change occurs and why a par
ticular pathway has been followed: of necessity, there is overlap
with biology, geology and physics. One possible definition of envi
ronmental chemistry is the study of the rOle of chemical elements
in the synthesis and decomposition of natural materials of all
kinds, including the changes specifically brought about by human
actions.
The selection of topics for inclusion in this book proved difficult.
The guiding principle has been to provide a broad survey
illustrating the operation of natural systems, with some diversions
to show how human activities can modify these systems. A four
part format has been chosen to allow the grouping together of
related environmental topics. At the same time this approach
allows theoretical concepts to be introduced as required; it is hoped
that the relevance of the theory to environmental problems is
clearly illustrated. Most readers will have at least a GeE O-level
knowledge of chemistry, but the text should be understandable
even to those without this. A glossary giving brief explanations of
terms and concepts used in the text is included. Bold type is used
to indicate first appearances of terms that are to be found in the
glossary or that are explained in the text. The book will have
achieved its objective if, after reading it, you have gained some
viii Preface
insight into the operation of chemical processes near the Earth's
surface, and discovered that environmental chemistry is an exciting
area of study.
The students for whom this book is designed will be taking first
year degree courses in environmental science or the various types
of modular degree courses involving chemistry, geology, biology,
ecology and physical-geography options. In addition some second
and third-year special courses will find material of interest, as will
science sixth-formers.
Part A sets the scene and provides an introduction to many of
the basic geological, geochemical and chemical ideas that are
essential for an understanding of geochemical cycles. The import
ance of oxygen to the chemistry of reactions occurring near the
Earth's surface is emphasised by dealing with this element first.
This importance applies to both biologically mediated and
inorganic reactions; systems depending upon these reaction types
are discussed in Parts Band C. Both differences and similarities
between animate and inanimate systems are reviewed; above all,
the application of general chemical concepts to what might appear
to be widely different reactions is illustrated. Because the mobility
of one element depends upon the other chemical species in a
particular environment, different aspects of certain topics of
concern (such as 'acid rain') are discussed in several chapters. In
Part D there is a brief examination of some of the effects of human
activities on elements that usually cycle naturally in small quan
tities. This final part further highlights the perturbation to natural
cycles caused by agricultural, industrial and social developments
with the consequent problems of environmental management.
There are many interesting and important topics that have,
regrettably, to be either only briefly dealt with or ignored in a short
book such as this. For example, the impacts of the use of synthetic
organic compounds and of nuclear-power production come into
this category: a reasonably detailed picture of the present state of
knowledge would require such an extensive review that this would
defeat the object of giving a broad overview of the natural
environment.
I would like to thank all those students and staff who have read
the manuscript either in full or in part. Their comments have proved
very helpful, as has the advice and guidance I have received from
the staff of the Publishers. However the responsibility for the
approach chosen and the views expressed remains with me.
P. O'Neill
CONTENTS
Preface page vii
List of tables xi
Part A The oxygen-rich planet 1
1 History of the Earth 5
1.1 Development of life 8
1.2 Distribution of the elements 12
1.3 Geochemical cycles 16
2 Oxygen 21
2.1 Chemical-compound formation 24
2.2 Molecular oxygen in the atmosphere 30
Part B Major elements found in living matter 39
3 Hydrogen 44
3.1 Isotopes of hydrogen 47
3.2 Water 50
4 Carbon 68
4.1 The carbon cycle 68
4.2 Aqueous systems 69
4.3 Photosynthesis and the formation of
carbon compounds 73
4.4 Energy 82
4.5 Geochemical accumulation of solar energy 86
5 Nitrogen 92
5.1 Natural transformation processes in the
nitrogen cycle 95
5.2 Nitrogen oxides in the atmosphere 99
5.3 Nitrogen fertilisers 101
5.4 Nitrate in water supplies 102
5.5 Balanced diet and food production 103
6 Sulphur 108
6.1 The sulphur cycle 108
6.2 The sulphur-dioxide problem 115
x Contents
Parte Major elements in the Earth's crust 125
7 Silicon 131
7.1 Silicate minerals 131
7.2 Weathering 132
8 Iron 139
8.1 Iron in natural systems 139
8.2 Iron in industrial systems 152
8.3 Corrosion 154
9 Aluminium 158
9.1 Aluminium in industrial systems 159
9.2 Aluminium in solution 161
10 Calcium and magnesium 164
10.1 Formation of calcareous rocks 166
10.2 Water hardness 167
10.3 Heart disease 169
11 Sodium and potassium 172
11.1 Clay minerals 173
11.2 Potassium fertilisers 177
11.3 Fluids in organisms 178
11.4 Radioactive potassium 180
Part D Minor elements and environmental
problems 181
12 Lead 191
13 Mercury 197
14 Zinc and cadmium 203
14.1 Sewage-sludge disposal 204
14.2 Toxicity of cadmium 208
14.3 Zinc 209
15 Phosphorus 210
Glossary 215
Index 225
LIST OF TABLES
page
A.l The ten major elements in the Universe, the Earth,
the Earth's crust, the ocean, the atmosphere (as dry
air), and the biosphere 2
2.1 Relationships between the radius ratio (radius of
cation: radius of anion), the co-ordination number
of the cation (number of surrounding anions) and
the geometrical arrangement of the structure 30
4.1 The laws of thermodynamics paraphrased 83
5.1 The amounts of essential amino acids in some foods 104
5.2 Vitamins, their recommended daily allowances
(RDAs), and possible effects of deficiency in human
diets 106
6.1 Classification of rock formations according to their
ability to neutralise acid 118
6.2 Soil sensitivity to acid precipitation, based on the
chemical characteristics of the top 25 cm of soil 119
8.1 Energy needed to produce 1 tonne of steel 154
8.2 Free energies of formation for the oxides of some
metals 155
11.1 Concentrations of cations in human intracellular
and extracellular fluids 178
14.1 Comparison of metal concentrations in dry sewage
sludge and soil 207
15.1 Trace-element concentrations in phosphate rock
compared with their concentrations in normal soil 211
PART A
The oxygen-rich planet
Although it could be argued that each planet in the solar system has
its own unique features, the dioxygen-rich atmosphere and the
presence of living matter make the Earth especially interesting. It
was the presence of water rather than oxygen that was crucial to the
development of life on Earth, but the present composition of the
atmosphere ensures that organisms that can make use of the oxygen
in energy-releasing reactions are dominant at the Earth's surface.
In Part A we shall look at (a) the geological development of the
Earth, (b) the development of life forms, and (c) the part oxygen
has played in these developments. The presence of free or
combined oxygen dominates the surface chemistry of the Earth
(Table A.I); for this reason oxygen is discussed in this introductory
part of the book. Knowledge gained about oxygen's chemistry can
then be applied when discussing the chemistry of the other major
elements in living systems (Part B) and of the other major elements
in the Earth's crust (Part C).
Any study of environmental chemistry soon reveals the
dependence of the reactions of anyone element on the reactions of
a number of other elements. Therefore, although some reactions of
oxygen are considered in Chapter 2, more detail is often given in
later chapters when other elements are being investigated. For
instance the problems of acid rain involve the reactions of oxygen
with compounds of sulphur and nitrogen to form products that
dissolve in water to form acidic solutions. These solutions can
interact with a wide variety of soils, rocks, buildings and so on, as
well as affecting plants, animals and fish. As a consequence various
aspects of acid-rain production and its effects are discussed in
Chapters 2-6 and 9.
Chemical reactions involve the production of new distributions