Suspended Matter in the Aquatic Environment

323 Pages·1993·7.08 MB·English

by  Professor Dr. Doeke Eisma (auth.)

D. Eisma
Suspended Matter
in the
Aquatic Environment
With 135 Figures
Springer-Verlag
Berlin Heidelberg New York
London Paris Tokyo
Hong Kong Barcelona
Budapest
Professor Dr. DOEKE EISMA
Netherlands Institute
for Sea Research (NIOZ)
P.O. Box 59
1790 AB Den Burg
Texel, The Netherlands
ISBN- 13 :978-3-642-77724-0 e-ISBN- 13 :978-3-642-77722-6
001: 10.1007/978-3-642-77722-6
Library of Congress Cataloging·in·Publication Data. Eisma, D., Dr. Suspended matter in the
aquatic environment / Doeke Eisma. p. cm. Includes bibliographical references and index.
ISBN-13:978-3-642-77724-0 \. Sediment, Suspended. I. Title. GB 1399.6.E37
1992 55\.46'01-dc20 92-27025
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Preface
The purpose of this book is to give an introduction to the most
important aspects of suspended matter in the aquatic environment:
its origin and composition, the concentration distribution, transport
and deposition, and the most important physical-chemical-bio
logical process that affects suspended matter: flocculation. In Chap
ter 1 the development of suspended matter observation and study
throughout history is given, with the coming of a more modern
approach during the 19th century and the first half of the 20th
century, and the development of the present science of suspended
matter after 1945. The sources of suspended matter in rivers, lakes,
estuaries, and the sea are discussed in Chapter 2, which includes the
supply of detrital particles as well as the formation of new particles in
the water (organic matter, carbonate, opal). The concentration
distribution of suspended matter in rivers, lakes, estuaries, tidal
areas, lagoons, and in the sea is discussed in Chapter 3, to which is
added a discussion on the sampling of suspended matter and on
methods to determine its concentration. Particle composition is
treated in Chapter 4, to which is added a section (4.6) on the
compositional analysis of suspended particles. Also included is a
discussion on particle surface characteristics and the adsorption of
elements and compounds onto particles. In Chapter 5, the transport
of suspended matter by currents and waves is discussed, which
includes the initiation of particle motion (scour, erosion, resuspen
sion) and particle settling, as well as transport and deposition in
stratified waters and autosuspension. This is preceded by a short
introduction on turbulence (Sect. 5.1), which is the principal agent in
bringing and keeping suspended particles in suspension. Particle size
and flocculation are discussed in Chapter 6, with a section (6.4) on
measuring suspended particle size. A more integrated description of
the behavior and fate of suspended matter in natural aquatic envir
onments (rivers, lakes, estuaries, intertidal areas, fjords, and the sea)
is given in the last Chapter (7).
By necessity this book has certain limits. The physical, chemical,
biological, and sedimentological background is not treated exten
sively but is referred to, or considered to be known. Also the complex
details of the various processes involved have been left out: an
VI Preface
extensive reference list is provided. In all this the emphasis is on
processes where they affect the particulate matter in suspension. The
reverse - the influence that suspended particles have on chemical and
biological processes in particular-is treated in only a general way.
The reader who wants to understand more is referred to the various
publications cited in the text where these processes form the central
theme.
During writing and publishing I received much help from G.c.
Cadee, R.W. Duck, K. Dyer, L. Maas, R.H. Meade and W. Salomons
who read the manuscript, or parts of it, critically. Mrs. 1. Hart and
Mrs. J. Schroder I thank very much for typing the manuscript and
Mr. B. Aggenbach and Mr. B. Verschuur for preparing the figures
and photographs.
Texel, 1992 D. Eisma
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1
1.1 Suspended Matter Observations in History. . . . . . .. 2
1.2 Development of a More Quantitative Approach .... , 4
1.3 Suspended Matter Transport Studies. . . . . . . . . . .. 5
2 Sources of Suspended Matter . . . . . 9
2.1 Suspended Matter in Rivers. . . 9
2.1.1 Storage of Sediment ................. , 12
2.1.2 Particulate Organic Matter in Rivers. . . . . . .. 14
2.2 Suspended Matter in Lakes. . . . . . . . . . . . . 15
2.2.1 River Supply and Primary Production . . . . 16
2.2.2 Calcite Particles. . . . . . . . . . . . . . . . . . 18
2.2.3 Opal Particles. . . . . . . . . . . . . . . . . . . 19
2.2.4 Resuspended Particles. . . . . . . . . . . . . . . .. 19
2.3 Suspended Matter in Estuaries . . 20
2.3.1 Supply of Biogenic Material 22
2.4 Suspended Matter in the Sea 23
3 Concentration Distribution
and Sampling of Suspended Matter 29
3.1 Concentration Distribution . . . . 29
3.1.1 In Rivers. . . . . . . . . . . . 29
3.1.2 In Lakes . . . . . . . . . . . . . . . . .. 33
3.1.3 In Estuaries, Tidal Channels,
and Coastal Lagoons. . . . . . . . . . . . . . . 36
3.1.4 In the Sea . . . . . . . . . . . . . . . . . . . . . 38
3.2 Sampling Suspended Matter and Determination
of Suspended Matter Concentration . . . . . . . . . . .. 45
3.2.1 Water Sampling and Filtration. . . . . . . . . . .. 46
3.2.2 Light Scattering and Radiation Measurements. .. 48
3.2.3 Acoustic Methods. . . . . . . . 49
3.2.4 Remote sensing . . 49
3.3 Sediment Traps . . . . . 50
VIII Contents
4 Particle Composition. 52
4.1 Mineral Particles 52
4.2 Biogenic Particles . 55
4.3 Adsorbed Elements and Compounds. 60
4.4 Stable and Radioactive Isotopes . . . . . . . 65
4.5 The Scavenging Process . . . . . . . . . . . . 69
4.6 Determination of Suspended Particle Composition 73
4.6.1 Analysis of Suspended Matter Composition . 74
4.6.1.1 Bulk Analysis. . . . . . . . 74
4.6.1.2 Single Particle Analysis. 76
5 Transport of Suspended Matter. . 78
5.1 Turbulence . . . . . . . . . . . 78
5.1.1 Statistical Description. 82
5.1.2 Size of Turbulent Eddies. 82
5.1.3 Diffusion by Turbulence. 83
5.2 Transport of Suspended Matter. . . 83
5.2.1 Estimating Suspended Matter Transport . . . 90
5.2.2 Other Approaches
to Suspended Matter Transport . . . . . 93
5.2.2.1 The Energy Model. ....... . 93
5.2.2.2 The Gravitational Theory . . . 94
5.2.2.3 Stochastic Models . . . . . . . . 94
5.2.2.4 Three-Dimensional Models ... . ..... 97
5.3 Initiation of Particle Motion
(Scour, Erosion, Resuspension) 98
5.4 Transport by Surface Waves. 111
5.5 Particle Settling . . . . . . . . . 117
5.6 Particle Deposition . . . 122
5.7 Stratification ...... . 124
5.7.1 Density Gradients 125
5.7.2 Internal Waves 129
5.8 Autosuspension . . . . . 129
6 Particle Size. . . . . . . . . . . 131
6.1 Flocculation of Suspended Matter . 133
6.1.1 Salt Flocculation ....... . 138
6.1.2 Particle Collision . . . . . . . . 140
6.1.3 Floc Formation by Bubbles .. 143
6.1.4 Coatings . . . . . . . . . . . . . . 145
6.1.5 Flocculation by Organisms ... 146
6.1.6 Floc Breakup . . . . . . . . . . . 147
6.1.7 Floc Structure: Floc Types ... 150
6.1.8 Final Remarks on Flocculation. 152
Contents IX
6.2 Floc Density and Settling Velocity ............. 154
6.3 Grain Size in Relation to Particle Size: Size Sorting. . . 159
6.3.1 Size Spectra in the Ocean ............... 159
6.3.2 Size Spectra of Constituent Grains .......... 161
6.4 Measuring Particle Size .................... 164
7 Transport Systems and Fluxes of Suspended Matter. ..... 167
7.1 In Rivers ............................ 167
7.2 In Lakes ............................ 174
7.3 Transport and Fluxes in Estuaries ............. 180
7.3.1 Constraints on Particle Transport
Through Estuaries ................... 181
7.3.2 Saltwedge Estuaries. .................. 185
7.3.3 Tidally Mixed Estuaries. . . . . . . . . . . . . .. 189
7.3.4 Estimates of Particle Flux Through Estuaries
from Numerical Models. . . . . . . . . . . . . .. 199
7.3.5 Tracer Studies in Estuaries .............. 201
7.3.6 Sediment Balance Estimates. . . . . . . . . . . . . . 203
7.4 Intertidal Areas . . . . . . .................. 211
7.5 Fjords. . . . . . . . . . . . . . . . . . . . . . . . . . . ... 218
7.6 The Continental Shelf. . . . . . . . . . . . . . . . . . . .. 224
7.6.1 Dispersal of River-Supplied Suspended Matter .. 228
7.6.2 Dispersal of Suspended Matter from Coasts
(Beaches, Inlets, Eroded Coasts) ........... 238
7.6.3 Suspended Matter and Mud Deposits
on the Inner and Middle Shelf . . . . . . . . . . . . 239
7.6.4 Suspended Matter on the Outer Shelf. . . . .... 244
7.6.5 In-Situ Measurements and Modeling ........ 246
7.7 Suspended Matter in Canyons
and Along the Continental Slope. . . . . . . . . . . . . . 248
7.8 Suspended Matter in the Ocean ............... 251
7.8.1 Particle Transport in the Ocean ........... 253
7.8.2 The Vertical Particle Flux ............... 256
7.8.3 Particle Fluxes in Relation
to Organic Production. . . . . . . . . . . . . . . . . 260
. 7.8.4 Compositional Changes . . . . . . . . . . . ..... 262
Postscript on Sediments. . . . . . . . . . . . . . . . . . . . . . . . 264
References . . . . . . ...... 265
Author Index. . . . . .. .... 300
Subject Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
Index of Geographical Names ................... 313
1 Introduction
By convention, particulate matter in suspension is defined as the material that is
retained on a 0.4 to 0.5 /lm pore size filter. Smaller material is considered to be
"dissolved" but actually it may be colloidal or particulate: particles as small as
0.02/lm have been observed in natural waters (Gordon 1970; Harris 1977;
Eisma et al. 1980), although it is not certain that such particles are not artifacts
produced out of larger particles during sampling. As very little is known about
such particles in natural waters, particles smaller than 0.4 to 0.5 /lm, colloids,
large or small molecules, and ions, although chemically important and of
possible importance for the flocculation of suspended matter, remain outside the
scope of this book.
The upward size limit of particulate matter in suspension is not fixed.
Relatively large and heavy particles like sand grains and gravel sink rapidly to
the bottom, but very large low-density structures can remain in suspension for
quite a long time. Because of gravity, all suspended material with a density
greater than the surrounding water will eventually sink to the bottom unless
there is a force that keeps it suspended. Normally this force is the drag provided
by the turbulent motion in the water: whether the material remains in suspen
sion or not is closely related to the intensity of the turbulence, as well as to the
size, density, and shape of the particles involved. In strong turbulence even
heavy and large sand grains can go into suspension and remain suspended for
some time, as happens in rapidly flowing streams or in the heavy surf along
beaches. This can also happen when sand is suspended in high concentrations of
fine mud: the settling of the sand grains is hindered by the large number of fine
particles. Particles containing gas (air) or low-density organic material can be
buoyant and move predominantly upwards through the water.
Deposition of suspended matter usually results in a fine-grained deposit
("mud") with a grain size less than ca. 100 /lm. When the suspended material
contains large amounts of relatively large hollow biogenic particles such as
foraminifera tests or diatom frustules, an "ooze" is formed that contains particles
much larger than 100 /lm. In lakes and reservoirs behind dams, deposition of
suspended material supplied by a fast-flowing stream also can result in a
relatively coarse-grained deposit.
The fine-grained material in suspension has a large specific surface (surface
area per unit weight), whiGh is larger when the particles are finer. Because
organic matter is usually fine-grained, and forms coatings on the particles, while
the fine mineral particles in suspension are mostly clays, the fine-grained
2 1 Introduction
suspended material is highly surface-active. This implies that dissolved or
colloidal material is easily adsorbed onto the particle surfaces. A partitioning
takes place between material that is adsorbed and material that remains in
solution, which depends on the concentrations and specific properties of both
the dissolved substances and the particles in suspension. During the past ca. 125
years this property has had - and still has -large consequences for the dispersal
of polluting substances such as trace metals and a number of synthetic organic
compounds. In this way, pollutants also can become concentrated and buried in
sediments. Pollutants that are discharged in fine-grained particulate form
(organic waste, fly-ash, gypsum), also end up in mud deposits, in so far as they
are not dissolved (gypsum) or mineralized (organic matter) on the way before
being deposited.
In other fields, too, suspended matter plays an essential role. Particulate
organic matter often has a high nutritional value and thus can be a major source
of food for many aquatic organisms, but mineralization of accumulated partic
ulate organic material can result in very low dissolved oxygen values and even in
a high mortality of aquatic fauna when anoxia occurs. Both processes have
consequences for the abundance of aquatic life, including fish and large mam
mals, and are of great interest to fisheries. Sedimentary geologists have an
interest in the formation ofrecent fine-grained deposits from suspension in order
to understand how, and under what conditions, fine-grained mudstones or
shales in the geological record have been formed. The organic matter in such
sediments has been a basis for the formation of oil and natural gas. An early
interest from engineers and soil scientists came from the accumulation of mud in
coastal areas, which leads to siltl;ltion of harbors and shipping channels, but also
to the formation of new land (marshes, flats) that can be reclaimed.
Suspended matter is present in all natural waters of the world. It may be a
very small amount, as in the crystal-clear waters in caves and in some parts of
the ocean, but microscopic inspection up to now has always indicated the
presence of at least some suspended particulate material. Because of this
ubiquitous presence, and because of the physical and chemical properties of the
particulate material itself, the suspended matter forms an integral part of the
worldwide geochemical, biological, and geological cycles in the aquatic environ
ment.
1.1 Suspended Matter Observations in History
The interest in suspended matter and the realization of its importance are quite
recent. In Antiquity, the interest was mainly restricted to the effects of large
rivers carrying (suspended) sediment into the coastal sea, causing extensive
siltation in embayments and filling up the shallow straits between some islands
and the shore (Berger 1903; Forbes 1963). The Nile and the Don were the classic
examples (Aristoteles Meteor I.XIV; Herodotus II, 10-12) but also for other