WATER POLLUTION CONTROL RESEARCH SERIES
16010EHR03/71
The Chemical Investigation
of Recent Lake Segments
from
Wisconsin Lakes and Their
Interpretation
M».TE A'«1li»!«f«&
YxiwaMI i\i Awi'tofi?
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U.S. ENVIRONMENTAL PROTECTION AGENCY
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THE CHEMICAL INVESTIGATION OF RECENT LAKE SEDIMENTS
FROM WISCONSIN LAKES AND THEIR INTERPRETATION
Gilbert Carl Bartleson
University of Wisconsin
Madison, Wisconsin 53706
for the
Environmental Protection Agency
Program #l6010 EHR
March 1971
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For sale by the Superintendent of Documents, U.S. Government Printing (Mice, Washington, D.C., 20402 - Trice *2.2
11
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Abstract
CHEMICAL INVESTIGATION OF RECENT LAKE SEDIMENTS
FROM WISCONSIN LAKES AND THEIR INTERPRETATION
Gilbert C. Bortleson
*
Under the Supervision of Professor G. Fred Lee
In most instances cultural eutrophication is an accomplished fact
because there are no data to document what a lake was like in precultural
times. The information needed to trace changing limnological and water-
shed conditions in a lake must come from a record preserved in lake sedi-
ments. The chemical composition of 1 m sediment cores fractionated into
5 cm intervals was used to trace the recent developmental history of Lakes
Mendota, Monona and Wingra (calcareous lakes in Dane Co., Wis.); Devils
Lake (a noncalcareous lake in Sauk Co., Wis.); Little St. Germain Lake,
Trout Lake, Lake Minocqua, Weber Lake and Little John Lake (noncalcareous
lakes in Vilas and Oneida Co., Wis.). The sediment cores were analyzed
for C, P, Ca, Mg, K, Al, Fe and Mn. Organic C and carbonate C were deter-
mined separately. Organic N, exchangeable ammonium and acid soluble P
determinations were performed on selected sedimentary profiles. Ambrosia
(ragweed) pollen was used to establish recent sedimentation rates and to
identify pre- and postcultural sediment in the core column.
Changes in the chemical stratigraphy of lake sediment cores are
traced to cultural activities in the watershed; these stratigraphic
changes are especially pronounced in the southern calcareous lakes. The
enrichment of P in the postcultural sediments of Lake Mendota is due not
only to an increase in supply of P from domestic drainage, but to an
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increase in P retentive capacity of the postcultural sediment and to an
increase of P deposition due to the concomitant increase in Fe, Mn4 K
and Al-containing compounds. The chemical stratigraphy of a 9.9 m Lake
Mendota core provided evidence that a long period of stable conditions
existed in the lake and watershed prior to the settlement period in
southern Wisconsin; the concentrations of organic C, P, Fe, Mn, Al, K,
Ca and ragweed pollen are all relatively constant over the interval 62
to 990 era. The estimated postcultural deposition rate of P (11.9 mg
2
P/CID 7100 yr) in the center of Lake Mendota is 5-8 times greater than
the precultural interval.
A trend which is common to all the northern Wisconsin noncaic.areo;is
lakes is an increase in organic C concentration with depth of stdiment.
The organic C concentration often shows an upward decrease before the
postcultural period is initiated; this is followed by a rapid decline in
organic C during the postcultural period.- The decrease in organic C is
usually accompanied by an increase in P, Fe, Mn and/or Al, K, Hg, Ca-
containing compounds. The P, Fe and Mn concentration profiles are
closely related in both the pre- and postcultural deposits. The con-
centration of P in the sediments is largely controlled by Fe and to s
lesser extent Mn deposition. In general, the aerobic sorption and de-
sorption of P studies indicate the sediment laid down postculturally is
a more favorable sorptive environment for P and a less favorable de-
sorptive environment for P than sediment laid down prior to cultural in-
fluences. This is due primarily to the concurrent increase in Fe in
the postcultural sediments for both calcareous and noncalcareous lakes.
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Only in the so^ci.-il ease of rate constant sediment accumulation can
a rate exprpssion be derived to estimate accurate!} n,i incremental change
in nutrients to the lake basin. The chemical stratigraphy of concentra-
tion-depth diagrams do, however, permit a qualitative evaluation of the
extent lakes have been influenced by man's activities.. The potentiali-
ties and limitations of using recent lake sediments to evaluate cultural
eutrophication of lakes are discussed.
APPROVED FOR PUBLICATION
>
'
/ \ / ' -''-^ ' '- -(.
' -£-'->/,>* >-
G. .Fred Lee
Professor of Water Chemistry
GRADUATE SCHOOL
JUL201970
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ACKNOWLEDGEMENTS
My appreciation is extended to several members of the Water
Chemistry program who have helped collect core and sediment samples.
Special gratitude is due to Professor G. Fred Lee for his advice and
assistance throughout this study; my wife Marlene, for encouragement,
patience and typing of the manuscript; J. Peterson and J. Delfino, for
exchange of analytical results and frequent assistance on sampling
trips; R. Plumb for frequent assistance on sampling trips; I. Sanchez
for Cu data on Monona core; R. Peters for technical lab assistance; Dr.
G. Hanson of the Wisconsin Geological and Natural Survey and Prof. D.
Clark of the Univ. of Wis. Geology Dept. for. core L-73 from Little St.
Germain.
This investigation was supported by the University of Wisconsin
Water Resources Center OWRR Project No. A-001-Wis., Training Grant No.
5T1-WP-22 from FWQA and a Research Grant from Wisconsin Wr.ter Resources
Center - FWQA. In addition, support was given to this project from the
office of Naval Research, University of Wisconsin Department of Civil
Engineering and Engineering Experiment Station.
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ii
TABLE OF CONTENTS
page.
Acknowledgements i
List of Figures iv
List of Tables , vi
Chapter I Introduction 1
Chapter II Literature Review 3
A. Natural Changes in Lakes 3
B. Cultural Eutrophication 6
C. Stratigraphic Distribution of Possible
Indicators of Eutrophication 8
D. Sedimentation Rate in Relation to a Depth-
Time Scale in Lake Deposits 18
E. Sedimentation Intensity 22
F. Mixing of Sediments 23
G. Changes in Lake Sediments After Deposition . 26
H. Sediment Properties Affecting Retention and
Release of Phosphorus 29
I. Other Wisconsin Lake Sediment Studies 40
J. Summary 41
Chapter III Experimental Procedures 43
A. Natural Environment 43
B. Field Sampling Methods 53
C. Analytical Procedures and Apparatus 54
D. Statistical Evaluation of Analysis 72
Chapter IV Experimental Results 74
A. Identification of Pre- and Postcultural
Sediments Using Ambrosia Pollen 74
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iii
B. Chemical Stratigraphy in Calcareous
Lakes in Southern Wisconsin 80
C. Chemical Stratigraphy of Noncalcareous
Northern Wisconsin Lakes and Devils Lake
in Southern Wisconsin 116
D. Estimation of Sedimentation Rates Using
Ambrosia Pollen 147
E. Postcultural Sedimentation Intensity 152
F. Sorption and Desorption of Added Inorganic
Phosphorus to Pre- and Postcultural
Sediments 159
G. Aerobic Leaching of Nitrogen and Phosphorus
from Lake Mendota Pre- and Postcultural
Sediment 167
Chapter V Discussion 172
A. Distribution of Carboi, 172
B. Distribution of Nitrogen 183
C. Distribution of Phosphorus 192
D. Distribution of Iron and Manganese 212
E. Distribution of Aluminum, Potassium
Magnesium and Calcium 222
Chapter VI Evaluation of the Relationship Between the
Chemical Composition of Lake Sediment Cores and
Lake Eutrophication and Suggestions for Further
Research 226
A. Potentialities and Limitations of Using
Lake Sediment Cores to Evaluate Eutro-
phication of Lakes 226
B. Guidelines for Future Lake Sediment
Coring Studies 239
Chapter VII Summary 243
Literature Cited 246
Appendix A Chemical Data on Lake Sediment Cores 260
Appendix B Mathematical Formulae Utilized During Investigation 278
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IV
LIST OF FIGURES
Figure Page
2.1 Distribution of Carbon, Chlorophyll and Sulfur with
Depth of Sediment for Esthwaite and Ennerdale Water
(after Gorham, 1961) 14
2.2 Hypothetical Comparison of Phosphorus Sedimentation In-
tensity Calculated from the Phosphorus Concentration
and Rate of Accumulation of the Sediment Matrix 24
3.1 State of Wisconsin Showing General Location of Lakes
Studied 44
3.2 Bathmetry and Coring Locations of Lake Mendota 47
3.3 Bathmetry and Coring Locations for Lake Monona 48
3.4 Bathmetry for Trout Lake and Coring Locations for Trout
and other Vilas County Lakes 50
3.5 Bathmetry and Coring Locations for uake Minocqua 51
3.6 Bathmetry and Coring Locations for Little St. Germain 52
3.7 Apparent P vs. Acidity at Different P Concentrations
Using Vanadomolybdophosphoric Yellow Color Method 59
4.1 Percent Solids (Dry Weight) with Depth of Sediment in
Lake Mendota Cores 84
4.2 Phosphorus Stratigraphy of Deep-water Lake Mendota Cores
Fractionated into 5 cm Intervals 86
4.3 Phosphorus Stratigraphy of Deep-Water Lake Mendota Cores
Fractionated into 2 cm IntervaTs and 8 cm Intervals 87
4.4 Chemical Stratigraphy of Lake Mendota Profile WC-89 91
4.5 Chemical Stratigraphy of Lake Mendota Profile WC-86,
University Bay 95
4.6 Chemical Stratigraphy of Lake Mendota Profile WC-84,
University Bay 96
4.7 Chemical Stratigraphy of Lake Mendota Profile WC-82,
University Bay 97
4.8 Chemical Stratigraphy of Lake Mendota Profile WC-92 101
4.9 Chemical Stratigraphy of Lake Monona Profile WC-101 104
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Figure Page
4.10 Chemical Stratigraphy of Lake Monona Profile WC-46 106
4.11 Chemical Stratigraphy of Lake Wingra Profile WC-92 ...... 109
4.12 Chemical Stratigraphy of Little St. Germain Profile
WC-92, West Bay 117
4.13 Chemical Stratigraphy of Little St. Germain Profile
WC-56, South Bay 120
4.14 Chemical Stratigraphy of Little St. Germain Profile
L-73, South Bay 123
4.15 Chemical Stratigraphy of Trout Lake Profile WC-59,
South Bay 126
4.16 Chemical Stratigraphy of Trout Lake Profile WC-60,
North Bay 128
4.17 Chemical Stratigraphy of Lake Minocqua Profile WC-51,
Northwest Bay 1 130
4.18 Chemical Stratigraphy of Lake Minocqua Profile WC-52,
Southwest Bay 132
4.19 Chemical Stratigraphy of Weber Lake Profile WC-66 135
4.20 Chemical Stratigraphy of Little John Lake Profile WC-67 . 137
4.21 Chemical Stratigraphy of Devils Lake Profile WC-75 140
4.22 Organic Carbon and Ragweed Pollen Profiles for Sparkling
Lake Core WC-65 142
4.23 The Effect of pH on the Phosphorus Sorptive Capacity for
a Lake Mendota Sediment 162
4.24 Aerobic Release of Inorganic Nitrogen and Soluble Phos-
phorus from Lake Mendota Precultural Sediment 168
4.25 Aerobic Release of Inorganic Nitrogen and Soluble Phos-
phorus from Lake Mendota Postcultural Sediment 169
5.1 Phosphorus Concentration and Sedimentation Intensity in
Gyttja and Marl Sediments of University Bay and the Deep-
water Area of Lake Mendota 200
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VI
LIST OF TABLES
Table page
3.1 Some Limnologic, Hydrologic and Morphemetrie Charac-
teristics of Study Lakes 45
3.2 Concentration of Caroon Observed in Sediment Using Peak
Height and Clock Integrator Methods r 56
3.3 Comparison of Carbonate Carbon Determinations on Lake
Mendota Core WC-86 . 63
3.4 Carbon Recovery of CaCO and Glucose After Low Tempera-
ture Ashing 65
3.5 Precision of Carbonate Carbon Determinations on Lake
Mendota WC-86 66
3.6 Mean, Standard Deviation and Relative Standard Error for
Chemical Analysis of a Calcareous and Noncalcareous Lakes . 71
4. i Ambrosia Pollen with Sediment Depth for Noncalcareous
Wisconsin Lakes 76
4.2 Ambrosia Pollen with Sediment Depth for Calcareous
Wisconsin Lakes 77
4.3 Lake Mendota Surface Sediment Data 81
4.4 Statistical Correlation Data for Relationship between
Depth of Sample Recovery and Element Concentration in Lake
Mendota 82
4.5 The Mean Concentration of Phosphorus in Pre- and Post-
cultural Lake Mendota Sediment 98
4.6 Mean Concentrations of Pre- and Posvcultural Sedimentary
Components for Calcareous Lakes 112
4.7 Comparison of Mean Concentration of Postcultural over Pre-
cultural Sedimentary Components in Calcareous Lakes 114
4.8 Mean Concentrations of Pre- and Postcultural Sedimentary
Components for Noncalcareous Lakes 143
4.9 Comparison of Mean Concentration of Fostcultural over Pre-
cultural Sedimentary Components in Noncalcareous Lakes.... 144
4.10 Estimated Sedimentation Rate in Lake Deposits Based on
Ambrosia Pollen Rise 148
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Vll
Table Page
4.11 Ragweed Counts in Sediment Matrix as a Relative Measure
of Sedimentation Rate in Pre- and Postcultural Sediment
of Noncalcareous Lakes < . . . 150
4.12 Sedimentation Intensity of Postcultural Sedimentary Com-
ponents for Calcareous Lakes 153
4. 13 Calculation of Sedimentation Intensity of Phosphorus for
Lake Mendota Core WC-89 154
4.14 Sedimentation Intensity of Postcultural Sedimentary Com-
ponents for Noncalcareous Lakes 156
4.15 Dry Sediment Accumulation below one Square Centimeter of
Mud Surface Since the Onset of the Postcultural Period . 158
4.16 Sorption and Desorption of Added Inorganic Phosphorus to
Pre- and Postcultural Sediments of Calcareous Lakes,
Woodland and Cultivated Soil in Lake Mendota Watershed . 160
4.17 Chemical Characteristics of Lake Mendota Watershed Soils 163
4.18 Sorption and Desorption of Added Inorganic Phosphorus to
Pre- and Postcultural Sediments of Noncalcareous Lakes 165
4.19 Chemical Characteristics of Lake Mendota Pre- and Post-
cultural Sediments Used in Aerobic Leaching Study 167
5.1 Organic Carbon to Organic Nitrogen Weight Ratio for Lakes
Mendota, Wingra and Trout Cores 184
5.2 Exchangeable Ammonium Concentrations in the Pre- and Post-
cultural Sediments of Lakes Mendota, Monona, Wingra and
Trout 187
5.3 Inorganic Nitrogen (N0~ + NH + NO - N) Released from
Lake Mendota Pre and Postcultural Sediments 189
5.4 Dissolved Inorganic Phosphorus Released from Lake Mendota
Pre- and Postcultural Sediments 199
5.5 Relationship Between Phosphorus, Iron and Manganese Sedi-
mentation Intensity in Noncalcareous Lakes 205
5.6 Comparison of Phosphorus Retentive Capacity and Chemical
Characteristics of Noncalcareous Pre- and Postcultural
Sediments 206
5.7 Iron to Phosphorus Ratio of the Noncalcareous Pre- and
Postcultural Sediments 210
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Vlll
Table Page
5.8 Mean Iron: Manganese Weight Ratio for the Pre- and
Postcultural Sediments of Calcareous Lakes 214
5.9 Mean Iron: Manganese Weight Ratio for the Pre- and
Postcultural Sediments of Noncalcareous Lakes 219
5.10 Sedimentation Intensity of Aluminum, Magnesium,
Potassium and Calcium in Noncalcareous Lakes in Northern
Wisconsin . 223
6.1 Average Percent Increase in Phosphorus Deposition in
Little John and Northwest Bay of Minocqua 233
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CHAPTER I
INTRODUCTION
In most instances cultural eutrophication is an accomplished fact
because there are no data to document what a lake was like in precultural
times. The information needed to trace changing limnological and water-
shed conditions in a lake must come from the record preserved in lake
sediments. Although several chemical studies have been performed on
postglacial sediments and interpreted on the basis of long-term trends,
few investigators have given sustained study to the most recent changes
in a lake's history. The chemical composition of 1 m sediment cores
fractionated into 5 cm intervals was used to trace the recent develop-
mental history of Lake Mendota, Lake Monona, Lake Wingra (calcareous
lakes in Dane Co., Wis.); Devils Lake (a noncalcareous lake in Sauk
Co., Wis.) and Little St. Germain Lake,--Trout Lake, Lake Minocqua, Weber
Lake, Little John Lake (noncalcareous lakes in Vilas and Oneida Co.,
Wis.). The calcareous lakes in southern Wisconsin are eutrophic and
the noncalcareous lakes in northern Wisconsin differ in their present-
day productivity status and patterns of cultural influence. By compar-
ing and contrasting the core profiles from the same geologic and geo-
graphic regions, certain conclusions can be made concerning chemical
sedimentation in lakes, particularly in regard to the effects man and
his civilization have had on the lakes and recent lake deposits. Lake
Mendota was the principal study environment and served as the primary
source of information.
If the lake sediments are considered as a part of the dynamic trophic
system, then it is worthwhile to consider not merely the reserve of
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nutrients in the sediments, but also how the change in the chemistry
of the sediments brought about by cultural activities has affected the
potential for release or retention of nutrients. The dynamic aspects
of nutrient enrichment of lakes (eutrophication) will continue into the
future, but the rates, dates and relative changes that have occurred as
a result of man's intervention will remain speculative until more data
are collected about the past chemical history of lakes. Frey (1969)
stated at the 1967 Eutrophication Symposium:
"There is really no need to apologize for the amount of
information in sediments; it is tremendous, although
still largely unappreciated. Some lines of investiga-
tion are already quite highly developed and are yield-
ing exciting results. Others are barely perceived,
much less explored. To a considerable extent, it is
not yet fashionable to study recent sediments. How-
ever, even the relatively few studies that have been
conducted make it clear that paleolimnology will have
a real impact on our eventual over-all understanding
of eutrophication and its effects on lake ecosystems."
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CHAPTER II
LITERATURE REVIEW
The change in biota and physicochemical conditions in many of the
world's lakes has been attributed to eutrophication. Of major concern
is the rate of eutrophication or the rate of change in the manifestations
of nutrient enrichment. There are no well defined units or quantitative
measures of trophic state. The trophic state of a lake is usually de-
fined by a variety of physical, chemical and biological indicators. For
example, some commonly used chemical indicators are sediment type, 0
deficit, dissolved solids, nutrient concentrations at spring maximum and
chlorophyll level.
Limnologists have long recognized that lake productivity is affected
by factors other than the concentration of nutrients in a body of water.
Rawson (1939) suggested many interrelationships among factors affecting
the trophic status of a lake. The nutrient and mineral load imposed on a
lake is a function of the geochemistry of its drainage basin, the hydrol-
ogy of the region, climate and other natural conditions. Superimposed on
these natural factors are a variety of human effects, e.g., urban and
agricultural runoff and the amount of domestic sewage disposed into the
lake. Other factors influence lake productivity primarily by affecting
the distribution, availability and the utilization of nutrients. Such
modifying factors include mean depth, littoral area, bottom conformation,
insolation, temperature, circulation and shoreline irregularity.
A. Natural Changes in Lakes
As a lake ages, it goes through a succession of biological, physical
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and chemical conditions and events. Most of the lakes in North Temperate
regions were formed by glacial action during the Pleistocene, roughly
10,000 - 12,000 years ago. In districts such as northern Wisconsin,
where many lakes were originally formed a good many of the small ones
have filled in completely and now consist of land occupied by terrestrial
vegetation. Under natural conditions lakes proceed toward geological
extinction at varying rates of eutrophication or bog formation (Hasler,
1969). Hutchinson (1941) states that three district factors are involved
in lake eutrophication: (1) the edaphic factor, representing the poten-
tial nutrient supply in the surrounding drainage basin; (2) the age of
the lake at any stage, indicating the degree of utilization of the nu-
trient supply; and (3) the morphometric character at any stage, dependent
on both the original morphornetry of the lake basin and the age of the
lake, presumably influencing the oxygen concentration. Hutchinson main-
tains true eutrophication takes place only in regions well supplied with
nutrients. The many points of view on the question of natural eutrophi-
cation and the trophic-dynamic aspect in succession are discussed by
Lindeman (1942).
The developmental history of lakes can be called ageing, but all age-
ing cannot be called eutrophication. Beeton (1966) and Brezonik et al.
(1969) proposed several possible lines of change for new lakes formed from
glacial origin. The classical scheme of lakes inevitably passing through
the evolutionary series of oligotrophy-mesotrophy-eutrophy has been
questioned by several recent studies (Goulden, 1964; Mackereth, 1965).
Mackereth (1965) theorized that lakes may be more productive in their
earlier stages (shortly after glaciation in this case) than later ones.
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On the basis of sediment core analyses in the English lake district,
Mackereth proposed that these lakes proceed from a eutrophic origin to-
ward an oligotrophic state unless other natural or human disturbance
alters their course. Lindemai? (1942) and Hutchinson and Wo Hack (1940)
also suggested the initial period of oligotrophy is relatively short after
glacial scour. Lindeman (1942) considered the early eutrophication period
to level off and a long period of relatively constant production to ensue
in a lake. This stable period is termed stage-equilibrium, during which
the sediments act as a nutrient reservoir or trophic buffer to maintain
high production. During the stage-equilibrium, sediments continue to
accumulate and the laRe approaches extinction. It may be instructive to
recognize Lindeman1s senescent stage as another major lake class. This
would represent the final evolutionary stage of a lake and would have the
characteristics described by Lindeman: shallowness, large littoral area,
high standing crop of macrophytes and low production per unit area. The
supposed irreversibility of eutrophication was questioned by Cowgill and
Hutchinson (1964), who reported a case of apparently reversible eutrophi-
cation during the time of the Roman Empire. Lag Monterosi rapidly became
eutrophic when the Roman road was built around the lake and later became
oligotrophic. The eutrophic period in the lake's history was recognized
by the kinds of diatoms found in the cores.
In summary, then, the following factors became major determinants
in the rate of development of the trophic character of the lake: geology
of the region, size and configuration of the lake basin, type and size
of watershed and latitude of the lake's location. It has not yet been
possible to estimate accurately the basic natural rate of eutrophication
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and the position of natural eutrophication in a lake's evolution.
B. Cultural Eutrophication
The influence of man in the lake's watershed can result in an in-
creased rate of nutrient influx to the lake which will bring about an
accelerated rate of undesirable chemical, physical and biological effects,
This process of lake fertilization has often been distinguished from
natural eutrophication. There is a general agreement among present
workers that cultural eutrophication is nutrient enrichment, but many
differences in opinion exist concerning details of the process and its
effects.
Over the past 50 years it has become clear that large-scale human
use of certain lakes has accelerated eutrophication. Most of the enrich-
ment of lakes and streams in Switzerland were caused by cultural activi-
ties of man, especially the discharge of sewage (Thomas, 1962). In the
U.S. similar cultural eutrophication has been noted for the Yahara lake
chain in Wisconsin, Lake Washington in Seattle, Lake Erie, Lake Tahoe and
others. The reader is referred to Stewart and Rohlich (1967) for case
histories of lakes in the world that have recently undergone changes.
Many case histories of changing lake conditions reviewed by Stewart and
Rohlich (1967) do not concern nutrients directly, but rather other in-
dices which the authors used to interpret changes that take place.
Increases in concentration of dissolved solids and/or certain ions,
such as chloride, have been observed in several lakes including the Great
Lakes (Beeton, 1965, 1966). Beeton (1966) suggested that these changes
might more appropriately be called environmental changes, which might not
indicate eutrophication. Nevertheless, Beeton explained they are due to
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man's use of the environment, and increases in the major ions probably
reflect what is happening to the nutrients.
Somewhat more controlled are situations in which lakes have been
fertilized deliberately with quantities of nutrients to increase produc-
tivity. For example, enough inorganic fertilizer was added to Bare Lake,
Alaska, to give 25 ppb P in the form of phosphate and five times the
amount of N in the form of nitrate (Nelson and Edmondson, 1955). Ferti-
lization was followed by a very great increase in the growth of algae.
According to Edmondson (1968), as far as experience goes, most lakes
appear responsive to fertilization most of the time. Edmondson (1968)
also recognized that because of the interaction of environmental factors
and the influence of size, shape, depth, exposure to wind, and rate of
replenishment of water on the ability of a lake to produce a crop of
organisms with a given supply of nutrients, different lakes will have
different sensitivity to enrichment. Ohle (1955, as cited by Stewart and
Rohlich, 1967) felt that the increased inflow of nutrients into an oligo-
trophic lake was not as noticeable as it was in the eutrophic lakes of
northern Germany. However, Ambuhl (1962, as cited by Stewart and
Rohlich, 1967) regarded oligotrophic lakes as the most sensitive to in-
creases in nutrients. Brezonik et al. (1969) studied the artificial
eutrophication of a small Florida lake by imposing a nutrient load at a
controlled rate. A lake with similar characteristics about 1/2 mi from
the one receiving the nutrient input served as the control. Brezonik
et al. (1969) concluded that qualitative classification based on chemical
and biological information was possible. However, the quantitative
classification was impossible since more than one criterion is required
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to define trophic state and because the relationships among the various
criteria remain undefined.
It would appear from the case histories of culturally eutrophic
lakes and the deliberate fertilization of lakes that increased input of
nutrients often causes measurable changes in biota and physicochemical
conditions. But, indicators of trophic state are only qualitative; it
is yet impossible to state specifically how much more eutrophic one lake
is than another or to express the rate of cultural eutrophication of a
lake, when using certain criteria of trophic status.
C. Stratigraphic Distribution of Possible
Indicators of Eutrophication
Biological Indicators. Biologists have long favored the use of in-
dicator organisms to detect changes in trophic state. Increases in the
abundance and changes in species composition of plankton and zooplankton
have been proposed as indicators of trophic state. Frey (1969) states
that lakes are sensitively responsive to any changes that affect their
water, energy and nutrient budgets. Therefore, long-term changes in
climate and edaphic conditions, including the phenomenon of eutrophica-
tion whether natural or accelerated by man, induce progressive changes
in the biota. Virtually all groups of animals occurring in inland
waters leave at least some morphological remains in sediments (Frey,
1964). The groups best represented in the sediments are the Cladocera,
midges, rhizopod Protozoa, ostracods, Turbellaria, Coleoptera and
molluscs (Frey, 1969). Among the algae, the diatoms and some green
algae, Chrysophyceae are represented in sediments.
Diatoms have been the plankton form studied most often as an indicator
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organism because of suitable preservation of siliceous frustules. Kendall
(1969) suggested, however, that the dissolution of diatom frustules
after death may explain fossil diatom trends for Lake Victoria, East
Africa in accordance to pH shifts of the water historically. Analysis
of diatoms in sediment cores have been made on a number of well studied
lakes. Notable among these are Pennington (1943) on Windermere, Patrick
(1943) on Linsley Pond, Nygaard (1953) on Lake Gribsd and Round (1961)
on Esthwaite Water. Stockner and Benson (1967) examined the diatom re-
mains in the recent sediment of Lake Washington. In the deeper sediment,
which was deposited prior to cultural enrichment, the relative composi-
tion of diatoms was constant. Correlated with the pattern of sewage dis-
charge into the lake, many of the species changed in accordance with
their ascribed trophic behavior as indicator species. Stockner and
Benson cautioned, however, that the indicator species approach to the
interpretation of sedimented diatoms leaves much to be desired because
of inadequate knowledge of nutritional physiology and of the ecology of
freshwater diatoms. Edmondson (1969) noted that many species substitu-
tions will also be effected by competition and predation, and not depend
on a simple and direct way on physiological tolerance or nutritional re-
quirements. Round (1964) found from the study of cores in the English
lakes that long-term changes in the diatom floras occur in a cyclical
sequence. He felt it was best to consider whole assemblage of species
and to take into account absence of species. Davis (1964) reviewed Lake
Erie phytoplankton data and reported changes from a centric-dominated
diatom assemblage in 1880 to one characterized by alternate pulses of
araphidinate- and centric-dominated assemblages. Charlton (1969)
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10
examined the ecological and sedimentologi cal history of Little St.
Germain, Wis. He concluded, based on the Centrales: Pennales diatom
ratio and the ecological requirements of the diatom species, that East
Bay, nearest the inlet, became eutrophic long before man's influence and
that South Bay, nearest the outlet, became eutrophic only in recent times.
A 19-inch core was collected from Lake Sebasticook, Maine, and several
1-inch segments of the core were examined to enumerate diatom skeletons
(FWPCA, 1966). High diatom counts occurred in the upper 12 inches of
deposits, and the authors attributed the change to recent nutrient en-
richment of the lake.
Lake sediments contain large numbers of microfossi1s of various
Cladocera zooplankters. Several investigators have suggested that the
type or quantity of cladoceran remains in the sediments reflects changes
in lake conditions or trophic level of the lake (Deevey, 1942; Goulden,
1964; Frey, 1964; Deevey, 1969; Goulden, 1969). The replacement of
Bosmina coregoni (longispina)by B. longirostris in lakes undergoing eutro-
phication has been observed in Lake Washington (Edmondson et al. 1956)
and in sediments of Linsley Pond (Deevey, 1942) and Esthwaite Water
(Goulden, 196^0. Deevey (1942) found a striking similarity in the shape
of the curves representing Bosmina content and total organic matter
plotted against depth, which, when plotted logarithmically against each
other, showed a linear relationship expressed by an empirical power
equation. That is, the growth and differentiation of Bosmina were com-
parable to the organic content of the sediments. The general sequence
of changes in Bosmina numbers followed periods of exponential rise, more
or less stable equilibrium and a decline which was probably due to changes
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11
within postsettlement times. Vallentyne and Swabey (1955) suggested
that the initial rise in productivity and the increase in Bosmina in the
early history of Linsley Pond were both dependent on climate. Based on
the distribution of Cladocera and midge remains in Esthwaite cores,
Goulden (1964) concluded that the lake was oligotrophic for most of its
development and only within the last 900 years became eutrophic under
the influence of man. Further, Goulden associated each of the four max-
imum Cladocera horizons with increased productivity due to climatic or
cultural changes in the drainage basin. Rather than an unidirectional
transition from an oligotrophic to an eutrophic condition, according to
Goulden, the midge and Cladocera evidence suggests that the lake alter-
nated between the two tendencies. After the examination of the Madison
lakes, Frey (1960) found that the quantities and species of Cladocera
remains in the sediments gave some indication of past production of
plankton. However, Harmsworth and Whiteside (1968) concluded that the
abundance of cladoceran microfossils from cores used to study lake his-
tory is not necessarily related to primary productivity and that numbers
of remains should not be compared from different lake systems.
The commonest insect remains in lake sediments are those of midges.
Stratified harmonic lakes have been classified on the basis of their
profundal chironomid fauna into oligotrophic Tanytarsus lakes, mesotrophic
Stictochironomus/Sergentia lakes and eutrophic Chironomus lakes (Stahl,
1969). In the profundal benthos, midges that require high oxygen con-
tent are replaced by those that can tolerate lower oxygen levels, and
they in turn by others that can tolerate still more taxing conditions.
The uses of chironomids and other midges in interpreting lake histories
-------
has been reviewed by Frey (1964) and Stahl (1969).
Chemical Indicators. The sediments of any basin contain clues to
the chemical history of that basin, but the interpretation of the sedi-
ment record is often difficult. The chemistry of the sediments is the
result of an involved series of precipitation, complexation, exchange
and sorption reactions covering a long period of time, between diverse
solids and complex solutions, both in the water column and in the sedi-
ments below. Nevertheless, investigators have made general inferences
about chemical events which have occurred in the historical past.
Organic matter in the sediments has often been used as a rough index of
past aquatic productivity.
In a comprehensive study on the sediment^ in the Lake District of
England, Mackereth (1966) examined the vertical distribution of Na, K,
Ca, Ng, Fe, Mn, S, C, H, N, P. Zn, Cu, Co and Ni. Mackereth felt that
the composition of sediments eventually reaching the lake bed could be
accounted for in terms of rates of erosion in the drainage basin rather
than in terms of the changing rates of organic productivity either on
the drainage basin or in the lake waters. He concluded although the
gross composition of the sediment is largely dependent on conditions in
the drainage system rather than in the lake waters, some deductions can
be made which indicate the availability of nutrients dissolved in waters
of lakes in past times. If the material is rapidly removed from the
drainage basin by erosion, nutrient elements are lost to the sediment
locked in the lattice of unleached mineral particles. If, however, the
rate of erosive removal of soil from the land surface is reduced, the
mineral particles are held in the soil column in a position which allows
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13
more efficient leaching of soluble components, which then become avail-
able to the populations of the lake.
Gorham (1961) examined the distribution of carbon, chlorophyll
derivatives and sulfur in cores from the fertile Esthwaite and unfertile
Ennerdale in England. Chlorophyll derivatives, S, and C exhibited simi-
lar trends in each of the sediment cores as shown in Figure 2.1. In
Esthwaite maximum levels of all three constituents were reached early in
the course of lake development, while in Ennerdale maxima were attained
much later. In the case of chlorophyll derivatives and S, the concentra-
tions were much lower in Ennerdale than Esthwaite. According to Gorham,
the higher levels of S and chlorophyll, and the high ratios to C, were
associated with strongly reducing conditions which were more likely to
occur in the surface sediments and bottom waters of productive lakes
such as Esthwaite than in those of infertile lakes like Ennerdale. In
Esthwaite all three constituents showed a rapid rise in profile distri-
bution deep in the mud column implying the lake became eutrophic early
in its history; the maximum percentages of C occurred only a little above
the glacial clay. In contrast to Esthwaite, maximum concentrations were
reached more slowly in Ennerdale and occurred in the upper half of the
mud column.
Hutchinson and Wollack (1940) determined Si, Al, Ti, Fe, Mn, Ca, Mg,
P, S, N and lignin from 13 levels of a A3 foot profile taken in the sedi-
ments below deep water in Linsley Pond. Considerable increase in the in-
organic content in the most recent unconsolidated sediment at the top of
the profile was taken to indicate recent erosion of cultural origin.
Silica and Al were essentially constant, except at the bottom of the core
-------
CD
O
O
JS
J-l
CH
Q
2 - -
6 -r
0
2 - -
4 --
6 - -
Carbon (% Dry Wt)
5
Chlorophyll Units/100 g (% Dry Wt)
10 0 50 100 0
Sulfur (% Dry Wt)
0.2 0.4
0.6
Organic Bands in
Glacial Deposit
Glacial Deposit
Figure 2.1 Distribution of Carbon, Chlorophyll and Sulfur with Depth of Sediment for Esthwaite
Water (ES) and Ennerdale Water (EN) [After Gorham, 1961].
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15
where the sediment was rich in clay from the erosion in the basin in
early postglacial time. The distribution of organic matter in the pro-
file was believed by Hutchinson to indicate a rapid change from oligo-
trophy to eutrophy, followed by a long period of approximate equilibrium
in eutrophic conditions.
Horie (1966), on the basis of an upward increase in sedimentary N
concentration ot Lake Yogo, Japan, concluded that the lake became more
eutrophic. Horie felt that the trophic stage might well be controlled by
changes in lake level which probably had fluctuated many times by both
crustal deformation and oscillations of climate. Apparently the lake had
repeated oligotrophic and eutrophic tendencies.
A 286 cm core of sediments was taken from the center of Potato Lake,
Arizona, (Whiteside, 1965). Pollen, chemical and physical analyses were
made on the sediment. It was assumed that the increase of organic matter
above 120 cm in the sediments occurred during eutrophication. The in-
crease in production corresponded to changing climatic conditions as in-
dicated by the pollen diagram. According to Whiteside, the variations of
Fe, Mn and Ca could be explained by lake succession from oligotrophic to
eutrophic conditions. Within the core two pollen zones were observed:
One extending from the surface to 120 cm and the other below this level.
The upper pollen zone was dominated by an abundance of pine pollen. Be-
low 120 cm, the most abundant tree species were believed to have accumu-
lated during a period of cool and moist climate different from modern con-
ditions .
In another investigation of lake sediments, Murray (1956), who
cored Lake Mendota and Trout Lake extensively, reported evidence for
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16
recent increases in clastic material. He determined organic matter,
carbonates and clastic material for several stations in each of the
lakes. Based on his study, he felt that an important change in the
sedimentation of Lake Mendota occurred at some time in the recent past.
The new sediment, the black sludge, differed from the older buff marl in
having a much higher clastic content and being correspondingly lower in
carbonate. The organic content of the marl and sludge was similar.
Murray demonstrated in his study that the best explanation for this
change was a large increase in clastic deposition with little or no
change in the. formation of carbonate; the clastic material thus masked
the carbonate giving a high clastic - low carbonate sediment. Murray
stated the mechanism for producing the sludge required a corresponding
increase in organic deposition to maintain a similar level of organic
content in both the marl and sludge. The increase in clastic content
was attributed to farming in the basin and shoreline development since
the mid 19th century.
Several investigators have analyzed plant pigments in lake sediments
to provide clues to the history of changing conditions in lakes. An in-
crease in the amount of chlorophyll degradation products or carotenoids
in sediment profiles has been considered indicative of a ..eriod of
greater productivity (Vallentyne, 1955; Fogg and Belcher, 1961). The
use of fossil pigments to measure historical productivity has many re-
strictions. Low pigment concentrations in sediments may not permit dis-
tinction between low productivity and rapid diagenesis or, conversely
between high productivity and little diagenesis (Brown, 1969). Also,
there is no simple relationship between pigment distribution and
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17
taxonomic units for identification of paleo-populations (Brown, 1969).
Griffiths et al. (1969) determined oscillaxanthin known to be pro-
duced by Oscillatoria rubescens and 0. agardhii in cores from Lake
Washington. The authors related the vertical distribution of oscillaxan-
thin within the sediments to the recent history of sewage enrichment of
the lake. Vallentyne (1955) has analyzed sediment cores from six lakes
for chlorophyll degradation products. Chlorophyll units and ignitable
matter followed similar trends in each of the cores. Low chlorophyll
was generally found at the bottom of each profile and was followed by a
steep rise in concentration to a near maximum level which remained more
or less constant throughout the upper sequence. As the carotenoid
myxoxanthophyll is restricted in distribution to blue-green algae, Zullig
(1960, as cited by Brown, 1969) was able to use its occurrence in lake
sediments as a selective indicator of the existence of former populations
of this algal. A review is given by Brown (1969) and Vallentyne (1969)
on the distribution of fossil pigments in sediment cores.
Increases in concentrations of sedimentary amino acids, carbohydrates
and pigments occur from a few centimeters to a meter or more below the
surface of man> lake and bog sediments (Swain et al. 1964; Rogers, 1965)
Swain (1965) concluded from a review of some quaternary lake sediments
of North America that residual organic substances in lake and bog sedi-
ments show at least a generalized relationship to trophic and climatic
history of the body of water. In the case of many organic substances,
the problem is complicated by possible postdepositional changes within
the lake sediments by microbial synthesis, sorption and other causes.
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e
18
Relative sequences of events in a lake's trophic history can be
lucidated by the stratigraphic observation of chemical and biologi-
cal indices. Even though the sediments provide a storehouse of informa-
tion regarding past events, the interpretation of a sedimentary sequence
in a lacustrine environment realizes formidable limitations. The follow-
ing four sections reflect upon several complications arising in the
observation of recent sedimentary profiles.
D. Sedimentation Rate in Relation to a
Depth-Time Scale in Lake Deposits
Unfortunately, the amount of information that can be extracted from
lake sediment core analyses is often limited by the lack of an absolute
depth-time scale for the deposits. To interpret the sediments in terms
of nutrient income and past conditions of a lake, it is desirable to have
some time scale to relate the age of sedimentary events or the rates at
which sedimentary deposits were formed. The determinations of the ele-
mentary composition of sediments are usually expressed as percentages of
the dried sample. Percentage diagrams suffer the deficiency that all
changes from one level to another are strictly relative. If numbers per
unit volume (or weight) of sediment are plotted against depth, the changes
from one level to another are absolute, providing that the rate of sedi-
mentation has remained constant. Over short time intervals this assump-
tion is reasonably valid, but over long time intervals it is not. The
2
ideal is to present the stratigraphy in absolute terms, i.e. mg/cm /yr.
For sediments within the age range of radiocarbon, a curve showing
the rate of sedimentation as a function of time (or depth) can be con-
structed from a series of C-lA dates within a core. The radiocarbon
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19
ages of 24 samples were plotted against their depths below the mud surface
to show the relationship between depth and age of sediment, by Davis (L967),
for Rogers Lake, Connecticut. A derivative of a second-degree polynomial
equation was found that approximated the lower portion of the core, and a
first-degree equation was found that approximated the younger sediment.
The dating of the Rogers Lake profile allowed Davis to estimate the accumu-
lation rate of pollen types as a variable independent both of changes in-
volving other pollen types, and of change in the rate of accumulation
of the sediment matrix. A series of C-14 dates were obtained by Ogden
(1967) from core samples from Seth's Pond, a soft-water lake in Massachu-
setts, and Silver Lake, a hard-water lake in Ohio. A fitted regression
curve of the form, Y = cX , was obtained for sample age, X, with sample
X
depth, Y , in order to calculate sedimentation rates. In both lakes, the
2\.
sedimentation rates for postcolonial time (above the sharp rise in
Ambrosia and European weed pollen) were considerably greater than they
were in the rest of the cores. Ogden discussed the limitations of the
radiocarbon technique in estimating the age of sediments because of dilu-
tion of atmospheric C-14 by "dead" carbon derived from Paleozoic lime-
stone and the introduction of C-14 into the atmosphere by nuclear test-
ing. The errors in the estimates of sedimentation rate are largely due
to uncertainity in the C-14 measurements. One source of uncertainity in
C-14 measurements is the well-known possibility of error through the ad-
mixture of older carbon in lacustrine materials or through contamination
of the sample with foreign carbon. Pennak (1963), on Colorado mountain
lakes, and Kendall (1969) on Lake Victoria, East Africa have also deter-
mined rates of sedimentation by a series of C-14 dates. Many other
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20
workers have determined from a single or a few C-14 measurements a con-
stant or average rate of sedimentation.
Livingstone (1957) considered banded and varved sediments to be of
the utmost value in dating sediments. If the annual increment of sedi-
ment remained as a discrete layer, one could count these layers, thereby
establishing an absolute chronology for the lake. In practice such
annual layers can seldom be discerned. A number of instances are known,
however, in which annual laminae occur. Vallentyne and Swabey (1955)
found a series of brown bands near the bottom of Linsley Pond deposits.
The bands probably reflected some event that occurred 2 or 3 times a
year, possibly the diatom maxima (Livingstone, 1957). The alternating
brown and black bands were used by Livingstone (1957) to determine the
2
Bosmina, organic and inorganic content per cm per year from the 44 to
32 foot level of a Linsley Pond core. Ludlam (1967) found the sediments
in the southern half of Cayuga lake were generally banded. The deposi-
tion of a couplet of a dark and pale band seemed to be controlled by the
annual variation in the supply of allochthonous organic detritus and
clastic sediment. There was close agreement between the couplet counts
of major bands and the years between 1935 and the dates of floods or
periods of high lake level; thus the sediment samples were dated by the
couplet counts. In two lakes in southern Ontario (Tippett, 1964), the
alternating calcareous and organic members have been shown to represent
annual deposits by differential analysis of pollen and diatoms.
Several investigators have determined sedimentation rates by other
means than using an indicator to give the age of a stratum. Some of the
early methods assumed either a constant or average rate of sedimentation
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21
of one component of the core sediment or an average rate of sedimenta-
tion for total core material. Toyoda et al. (1968) constructed a time
scale for Lake Biwa, Japan based on the assumption that silicon was de-
posited at a constant rate. Therefore, a change in the silicate concen-
tration in the core was taken to be indicative of a change in sedimenta-
tion rate. It is probably dangerous to assume a "constant" rate of
sedimentation for any component in the sedimentary column in inferring
dates. Char1 ton (1969) calculated the present day sedimentation rate
of Little St. Germain from the annual silica budget of the lake. In
estimating the sedimentation rate from the total supply of a sediment
component, the investigator assumes that the sediment is settled uniformly
over the entire basin. Hutchinson and Wollack (1940) constructed a
depth-time scale for Linsley Pond deposits based on a limiting assumption
that unit mass of ash was deposited in unit time. This was done by plot-
ting ash content per unit wet volume against depth and integrating plani-
metrically between the bottom and each depth. The depths were then
spaced from the bottom upwards at distances equal to the successive
values of the integral.
Several workers have used the recent rise in Ambrosia (ragweed)
pollen to calculate recent sedimentation rate since the onset of cultural
activities (Davis, 1968; Ogden, 1966; Ogden, 1967; Lewis and McNeely,
1967). Ogden (1967) found that because of the variability of near sur-
face sediments as a result of bomb-produced C-14, limnologists and pollen
stratigraphers need some calibration marker other than the present mud/
water interface for C-14 dating. He indicated that Ambrosia pollen
analysis can be used to establish a boundary, that can be dated for each
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22
site from historical records, whose variation in stratigraphic age is
less than the usual counting error by C-14 analysis. Also, ragweed
pollen provides a time marker for recent sediments which are not in
the age range of radiocarbon.
Most lacustrine dating has been done to establish a depth-time
scale for pollen or fossil analysis. Sample ages for chemical and bio-
logical sedimentary sequences have received little attention. Davis
(1967) points out that the results from Rogers Lake indicate that an
estimation of sedimentation rates by means of a ser-'^.s of C-14 dates is
feasible. But she questions whether such an expensive and laborious
method is worthwhile since, when the deposition rate is relatively uni-
form, the percentage diagram conveys almost all the information about
changes as the deposition rate diagram.
E. Sedimentation Intensity
Graphs of sediment age vs. wet sediment thickness may give a mis-
leading picture of deposition rates because compaction, as well as age,
increases with depth. In order to compare the rates of accumulation of
materials of differing composition, moisture content and compaction, it
is more meaningful to give the rate of sedimentation in units of weight
per unit of area and time, which can be called sedimentation intensity.
If the thickness per year, water content and density of the deposits are
known, sedimentation intensity can be calculated. The time represented
by a unit of sediment thickness can be estimated by a number of methods,
as discussed previously, from various levels within a core of lake sedi-
ment. The deposition time for a unit thickness of sediment varies, of
course, in different parts of the profile. This fact points to the
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23
importance of obtaining a series of dated stratum to reveal changes in
accumulation due to core compaction.
The additional information obtained by transforming chemical changes
in concentration in a sedimentary profile to sedimentation intensity is
demonstrated in Figure 2.2. In sample (1), the P concentration per unit
wet volume is five times greater than sample (2); however, the rate of
accumulation per cm takes 20 years for sample (1) and four years for
o
sample (2). Thus, the resultant yearly influx (mg P/cm /yr) for both
samples is the same. Often results based on the absolute rate of accumu-
lation can lead to vastly different interpretations than those based on
percentage diagrams (Davis and Deevey, 1964).
F. Mixing of Sediments
There are several lines of evidence that mixing in lake sediments
is taking place and that the surface sediments are being contaminated
by older materials. The extent of mixing, of course, will determine the
resolution of the chemical, biological or physical stratigraphy. In
other words, does the chemical record show changes of 10 years, 100 years
or 500 years for a given interval size? In dealing with long-term trends
with intervals spaced 5 cm or more apart, mixing may be advantageous in
that the resultant integration of old and recent sediment particles make
less necessary any effort to analyze more closely spaced intervals. On
the other hand, if the sedimentation rate is slow, the vertical mixing
layer deep, the interval small and the investigator interested in short-
term trends, the extreme is represented in the seriousness of mixing.
Mixing of sediments is suggested by the simple observation of bur-
rowing organisms and burrows at various depths in the sediment cores.
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VOLUME
PHOSPHORUS
CONCENTRATION
SEDIMENTATION
ACCUMULATION RATE
YEARLY PHOSPHORUS
INFLUX
Sample
1 cm~
10 mg
per cm"
20 years represented
by 1 cm thickness
1 cm |
20 years
2.5 mg P deposited on
a cm2 surface each year
Sample
(2)
1 cm'
2 mg ,
per cm"
A years represented
by 1 cm thickness
1 cm
4 years
2.5 mg P deposited on
a cm surface each year
X * *
Y .
Figure 2.2 Hypothetical Comparison of Phosphorus Sedimentation Intensity Calculated from the Phos-
phorus concentration and Rate of Accumulation of the Sediment Matrix.
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25
Cole (1953) found from ninety vertical core samples in Douglas Lake,
Michigan, that 93 percent of the ndcrobenthic forms were in the upperr
most 14 cm, with greatest concentrations in the upper 1-2 cm level. The
deepest penetration was the 20-24 cm stratum. Berg (1938, as cited by
Cole, 1953) stated that upwards of 90 percent of the macroscopic bottom
fauna were between 0-15 cm in several Danish lakes he investigated. How-
ever, depth of burrowing was found to vary from lake to lake--the softer
the bottom the deeper the burrowing. Kleckner (1967, as cited by
Griffith et al., 1969) has shown that the chironomids and tubificids can
cause appreciable transport of surface material to a depth ot about 3
cm. Vieth (1968) found that toxaphene applied to a lake for rough fish
control was mixed downward into the sediments a distance of 10 to 15 cm
in nine months. Twenhofel and McKeIvey (1941) argued that their in-
ability to detect laminations in Wisconsin lake sediment cores results
largely from intensive reworking of them by benthos. The thickness of
the homogeneous mixed layer, which is often associated with the oxidized
mud zone, probably varies considerably in different lakes. Hayes, Reid
and Cameron (1958) presented evidence that the real oxidized layer was
only one mm thick or less. Similar results were reported by Zicker
et al. (1956). Gorham (1958) reported that the thickness of the oxidized
microzone may depend upon the turbulent displacement of the uppermost
sediments due to wind currents. The reader is referred to Lee (1969),
Ogden (1967) and Davis (1967) for discussion on further evidence of
mixing of sediments.
Mathematical mixing models have been proposed by Berger and Heath
(1968) and Davis (1967). A simple conceptual model included a
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26
homogeneous layer of variable depth below the sediment-water interface
where the particles become thoroughly mixed with older deposits, and a
historical layer where particles come to rest. The vertical mixing in
sediments can be quantitatively described if several assumptions are
made. For example, in the models proposed, it is assumed that a particle
just deposited can reside with equal probability at any depth within the
homogeneous layer. In reality a decreased intensity of mixing with
depth below the surface probably occurs.
In the interpretation of the sedimentary record the assumption is
generally made that there has been essentially no movement of materials
upward or downward except in the biologically active layer near the sur-
face. A given interval size in the core column will contain the inte-
grated chemistry over a time span which is dependent on such factors as
sedimentation rate and depth of the mixing layer.
G. Changes in Lake Sediments After Deposition
The changes that can take place after deposition are an important
aspect in the interpretation of the chemistry of lake sediment cores.
Despite the great importance to the problem little is known about the
subject. According to Larsen and Chilingar (1967), diagenesis would
include all physical, biochemical and physicochemical processes which
modify sediments between deposition and lithification or cementation at
low pressures and temperatures. Recent sediments usually reveal only
early stages of diagenesis. The earliest diagenetic processes involve
consumption of oxygen by organisms below the depositional interface which
changes the environment from oxidizing to reducing (Allgeier, et a 1., 1941;
Mortimer, 1941; Armstrong, 1967). The redox potential is particularly
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27
affected by the zone of maximum bacterial activity (Zobell, 1946). The
extent of the bacterially active zone may be directly related to the
rate of sedimentation. Butkevich (1938, as cited by Bordovskiy, ]965)
has shown where sediments deposit rapidly, active bacteria occur in de-
posits of great depth, and where sediments accumulate relatively slowly,
active bacterial forms occur only in the uppermost layer of material.
According to Krumbein and Garrels (1952) the maximum effect of diagenesis
can be expected where fairly rapid deposition takes place under condi-
tions of positive Eh, with the entrapment of abundant organic material.
Conversely, the minimum effect should occur in an environment where
conditions are strongly reducing at the depositional interface, so that
burial produces no real change, and in deposits with little or no organic
matter.
Emery and Rittenberg (1952) studied the diagenesis of recent sedi-
ments off the southern California coast. Some changes they noted in
cores were as follows: (1) the water content markedly decreases with
depth of burial and is greatest in the finest sediments, (2) the pH of
the sediment surface is slightly higher than that of the bottom water
and generally increases with depth of sediment. The zone of lowest pH
occurs at a depth of maximum bacterial activity and where sulfates,
nitrates and CO- are formed by oxidation. Bacterial reduction of sul-
fates and possibly base exchange give rise to higher pH at depth, (3)
the lowering of Eh is due to the withdrawal of dissolved oxygen from the
interstitial solutions in the upper layers and to the action of sulfate-
reducing bacteria on dissolved sulfates at greater depth, (4) the ammonia
content is greatest at depth in the sediment and (5) the organic N and
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28
organic C both decrease with depth of sediment. In contrast to the
decrease of organic N and organic C with depth of burial noted by Emery
and Rittenberg in marine sediments, the organic C and organic N were
found to increase with depth of sediment over a one meter interval for
Trout Lake, Wis. (Murray, 1956; Bortleson, 1968). The lignin content of
the gyttja was determined by Twenhofel et al. (1945) for several cores
from Trout Lake. Twenhofel et al. had anticipated that the bacterial
decomposition would have led to a decrease in the nonligneous materials
and thus an increase of ligneous materials with depth. They concluded
that the fact such a decrease was not observed suggested that bacterial
activity ceased in the organic sediments of Trout Lake shortly after
burial. Hutchinson and Wollack (1940) believed the diagenetic loss of
organic matter was strictly limited to the unconsolidated modern mud in
Linsley Pond. According to Degens (1967), the early stages of diagenesis
involve microbial and chemical (hydrolysis) destruction of biochemical
macromolecules. Although the main function of bacteria is the decompo-
sition of organic matter, they also play an important part in its
synthesis. A review of the abundance, structural composition and sta-
bility during diagenesis of several organic components is given by
Degens (1967). Some aspects of changes and transformation of organic
matter in bottom marine sediments is presented by Bordovskiy (1965).
Changes after deposition seem to be more or less intimately con-
nected with the work of bacteria and other microorganisms. The bacterial
population is richest in the upper film of sediment; the numbers of
bacteria are greatly reduced below (Bordovskiy, 1965). The role of
anaerobic bacteria increases with depth of sediment. Sediment profile
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29
counts of bacteria were made by Henrici and McCoy (1938) for several
lakes in Wisconsin. The calculated total number of bacteria in the
bottom deposits was much greater than the number in the water in the case
of eutrophic and dystrophic lakes, and loxver in the case of oligotrophic
lakes. When the plate counts were plotted against sediment depth, there
was a general tendency for the curves to drop markedly at first, more
slowly beyond. According to Kuznetsov (1958) there is a definite depen-
dence between trophic status of a lake and the number of bacteria in
sediments. He found higher bacteria counts in eutrophic lakes than
oligotrophic lakes. Bordovskiy (1965) noted that the granulometric com-
position greatly affects the distribution of bacteria in sediments and
their physiological activity. A considerable portion of the bacteria in
fine-grained sediments are in an absorbed state, whereas in coarser-
grained sediments most bacteria are present in a free state between
particles and in solution. Supposedly, the physiological functions of
adsorbed bacteria are to some extent restricted in affecting changes in
the sediment environment compared to the free state bacteria (Bordovskiy,
1965).
In summary, changes and alterations in sediments may occur after
deposition to the extent which depends on the chemical environment,
bottom current, source of materials, sedimentation rate and biological
processes.
H. Sediment Properties Affecting Retention
and Release of Phosphorus
Any change in the composition or state of lake sediments could
affect the retention and release of P to the water phase. Livingstone
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30
and Boykin (1962) indicated that the high sedimentary P bound largely by
sorption reactions appeared to be the mechanism that limited the rate of
biological growth during the early phase of Linsley Pond history. The
distribution of P in Linsley Pond showed a marked resemblance to that
found in the English Lakes discussed by Mackereth (1966). Relatively
high concentrations of P occurred in the early postglacial deposits, fol-
lowed by a fall in concentration to the surface in a more or less irregu-
lar manner. Mackereth stated that the marked change in the sedimentary
P concentration at the clay/postglacial interface suggested that solution
followed by precipitation of P was an important mechanism in postglacial
time concurrent with the formation of a stable soil system in the drain-
age basin. At the time of glacial clay deposition, the migration and
precipitation of P was accomplished by direct removal and deposition of
fine rock particles.
Mackereth felt the two major processes involved in the sedimentation
of P were coprecipitation of P with oxidized Fe and Mn compounds and pre-
cipitation of P incorporated in the organic material synthesized in the
lake. In Ennerdale sediment the profiles of Fe and P concentrations were
inversely related as the sediment surface was approached; Fe rose stead-
ily in concentration, while P decreased. Mackereth explained that the
precipitation efficiency for P in the Ennerdale basin has not been in-
fluenced by variations in the Fe-Mn cycle, but the precipitation of P was
largely biological and relatively constant. On the other hand, Mackereth
believed that the P concentration was directly related to Fe and Mn dis-
tribution in the Windermere and Esthwaitc sediment and that the P minimum
in the core profile resulted directly from the loss of Fe from the lake
-------
31
basin at that time.
Factors Controlling Phosphorus Sorption and Desorption. MacPherson
et al. (1958) equilibrated P at different pH levels with sediments from
several lake types. Maximal uptake of P (minimal P left in the water)
occurred at pH 5.5 - 6.5. They found acid bog sediment released the
largest quantity of P, while productive, medium productive and unproduc-
tive lake muds followed in that order. The adsorption of P on the ]ake
sediments parallels that of a variety of solids (Carritt and Goodgal,
1954). A comparison with phosphoric acid dissociation curves indicates
that maximum uptake of P by solids occurs in the pH range in which H~PO,
ion is predominant. Murrman and Peech (1969) observed, for any given
soil, the amount of labile P in the soil and the concentration of P in
the soil solution both reached a minimum value at about pH 5.5 and in-
creased rapidly as the pH increased or decreased from this value. The
adsorption of P on sediments and soils is often represented by an empir-
ical adsorption isotherm. But as Carritt and Goodgal (1954) noted, the
adsorption isotherm expression gives a concise analytical expression for
the experimental facts, rather than a clear-cut picture of the mechanism
of adsorption.
The sorptive properties of soil minerals have been studied in con-
siderable detail by agronomists; they have been especially interested in
P fixation. Hsu (1965) noted that recent studies on P fixation describe
the mechanism as either precipitation or adsorption. According to Hsu,
whether the process is precipitation or adsorption is dependent on the
size of the polymer, which in turn is dependent on pH and the solution
P concentration. In common soils, because of the effect of pH, surface-
-------
32
reactive amorphous Al and Fe hydroxy-polymers dominate the process of P
+ 3 +3
fixation rather than discrete precipitation of Al or Fe compounds in
solution. For example, in slightly acidic or neutral medium (pH 6-7) of
dilute P solution (such as in sediments), amorphorus Al (or Fe) compounds
are stable and P is adsorbed on the surface. On the other hand, in an
acidic medium (pH 4) precipitation of Al might occur with a high concen-
tration of P (Hsu, 1965).
Based on the pH-solubility relationship of soil phosphates when com-
pared with those of known P 'minerals, it is generally accepted that the
inorganic P is dominantly bonded to Al and Fe in acid soils, and mainly
bonded to Ca in calcareous soils (Chang and Jackson, 1957; Hsu and
Jackson, 1960). Lindsay and Moreno (I960) developed a solubility diagram
for several pure Fe, Al and Ca compounds. Although the resulting solu-
bility diagram indicated the importance of pH on all the systems, Lindsay
and Moreno suggested that kinetic considerations during equilibration in
soils could more often than not preclude the obtaining of solubility data
which would correspond to any known solubility product. Hsu and Jackson
(1960) gave evidence that the transformations of P in soils were mainly
controlled by pH. Where strongly acidic, highly weathered soils under-
went an increase in pH by CaCO addition, a slow back-transformation to
Ca-P occurred while considerable Al-P and Fe-P persisted. They found
that reducing conditions in soils promoted the formation of Al-P instead
of Fe-P. The Ca, Al and Fe phosphates in soils and sediments are mix-
tures of compounds of some complexity. Hsu and Jackson (I960) plotted
the solubilities of these three compounds as a function of pH. On the
basis of solubility products, Al-P and Fe-P solubility approximately
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33
equaled Ca-P between pH 6 and 7. The solubilities also depended on the
activities of such other compounds as gibbsite, Al silicates, Fe oxides
and CaCO present. Above pH 6-7, Ca-P was more stable than either Fe-P
or Al-P especially in the presence of CaCO . Frink (1969) found that a
3
number of chemical changes occurred as sediment was transported from the
acid watershed to the neutral lake environment. The Al-P and Fe-P were
the major storage forms in the acid watershed soils, while there was a
shift towards Ca-P form in the neutral sediments. One effect of liming
on the form of P in soils is to favor the formation of Ca-P and to re-
lease P through the repression of Fe and Al compounds (Chang and Jackson,
1958) . Work on the sorption of phosphate by CaCO., was reported by Cole
et al. (1953). Their work demonstrated a surface sorption of P on CaCOo
particles at low concentrations of P in solution, and a precipitation
reaction at higher concentrations. Zicker et al. (1956) added CaCO to
the water phase of mud-water systems to reduce the amount of soluble P
in solution. However, Bailey (1968) noted that CaCO or the clay min-
erals, kaolinite and montmorillonite possess less capacity to fix P than
Fe(OH)3 and Al(OH) .
The possible formation of hydroxyapatite in the pH range of natural
waters by the conversion of CaCO to apatite was considered by Stumm
(1963). He calculated the equilibrium constant for such a reaction by
combining several reactions and then computed a free energy for the con-
version of CaCO into apatite. Stumm suggested that a negative A F
obtained from this reaction could be of significance in connection with
eutrophication of lakes, because it would suggest that the P distribution
in a lake can be interpreted as a heterogeneous distribution equilibrium
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34
between sediments and the lake, i.e., any addition of P would lead to a
progressive accumulation of P in sediments. However, the fact that
apatite can be present as inclusions in soil minerals instead of dis-
crete grains may exert a considerable influence on the availability of P
and on the rate and pattern of inorganic P transformations in soils and
sediments (Syers et al., 1967). Frink (1969) observed that Ca-P was
associated with the coarser fraction of sediment in a small eutrophic
lake in Connecticut and the Ca-P fraction decreased with increased water
depth.
The capacity of lake sediments for sorption of P was demonstrated
by Harter (1968). He used various concentrations of P in water and
mixed them for a short time with 0.1 gram ot sediment. Based on the
amounts of P extracted with NaOH and NH,F from the treated mud, Harter
4
found the addition of less than 0.1 rug P/g of sediment resulted in a
tightly bonded form of P occurring probably as Al-P. When mure than
0.1 mg P/g was added, the additional P was in a more loosely bond form
of P extractable in NH.F. Harter concluded that the capability of the
4
sediment to adsorb considerable loosely bound P means large influxes of
P into the lake may be held temporarily and subsequently released to
growing plants and algae. Hsu (1965) found when the surface of amorphous
Fe and Al compounds were nearly saturated with P, the adsorbed P may be
highly available to plants. On the other hand, the adsorbed P may be
less available when a small amount of P is retained by a large amount of
amorphous Fe and Al compounds. Carritt and Goodgal (1954) examined the
P-solids system in Chesapeake Bay sediments and suggested that low
salinity and pH and high turbidity of the fresh river water favored the
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35
formation of the P sorptive complex. In estuaries mixing of these waters
with sea water presents an environment of higher salinity, pH and con-
centration of competing ions, factors which favor the regeneration of
P. Carritt and Goodgal also suggested that during desorption of P, both
the amount of P and the rate of removal from the complex will depend
upon the length of time the complex has had to form. With a long contact
time a greater fraction of the P will have diffused into the solid and
so will be slower to return to solution when environmental conditions
change in a direction favoring desorption. Kafkafi et al. (1967)
studied the desorption of P on kaolinite. If the P was adsorbed in very
small increments, some of it was converted directly into a fixed form.
In the presence of large concentrations of P, all the adsorbed P became
exchangeable. Experiments were made on the effects of pH, P concentra-
tion, particle size, Fe and organic matter on the adsorption of phos-
phate by estuarine bottom deposits by Jitts (1959). The ability of the
sediment fractions to adsorb P showed an inverse relationship with par-
ticle size. While the presence of organic matter depressed P uptake,
the increase in concentration of Fe increased the sorption of P. Olsen
and Watanabe (1957) found that P sorption was closely related to sur-
face area. Acid soils retained more P per unit surface than alkaline
soils, and acid soils also held P with greater bonding strength than
alkaline soils. Isotopically exchangeable P as determined by isotopic
dilution is a useful index of active P in sediments. The extent to
which the P fraction undergoes isotopic dilution is taken as an estimate
of the fraction's surface activity. According to Tandon and Kurtz
(1968), the specific activities of the P fractions in widely different
-------
36
soils followed the sequence of A1-P^> Fe-P^> Ca-P. For instance, Ca-P has
more slowly exchangeable components than Al-P.
Oxidation-Reduction Effects. Rittenberg et al. (1955) observed from
the distribution of phosphate in the interstitial waters of cores from
the Santa Barbara and Catalina Basin that Eh played a major role in the
solubility equilibria. In the former sediment, which was strongly re-
ducing throughout, phosphate concentration increased rapidly from the
surface downward; in the latter, phosphate increased markedly only in the
zone of negative Eh which started about 80 cm below the surface of the
core. They found in the sediments investigated that deposition of P
took place in an environment of relatively low pH, low organic content
and an Eh near zero. Soluble P accumulated in an environment of low Eh
and relatively high pH and organic content. The presence of organic
compounds which form chelation complexes with Fe and Al ions are re-
ported to have the effect of decreasing the extent of phosphate precipi-
tation by these ions (Struthers and Sieling, 1950, and references cited
therein). Savant and Ellis (1964) noted, in submerged soil, the solu-
bility of soil P increased with the development of reducing conditions
when Fe-P was the main constituent of soil P. A negative linear rela-
tionship between available P and redox potential was distinct in slightly
acid silt loam soil, but the relationship was not as evident in the cal-
careous silt loam. Their experiments showed that organic matter in sub-
merged soil accelerated the rate of decrease of redox potential. Mortimer
(1941; 1942) proposed that the adsorbent properties of the oxidized mud
surface were largely due to the presence of colloidal ferric complexes
and -that removal of complexes on reduction of the mud surface liberated
-------
37
adsorbed ions, including phosphate, to the overlying waters. Al, unlike
Fe, does not respond to changes in redox potential and thus the stability
of Al-P in the sediments would be higher than similar Fe-P during periods
of reduction in stratified lakes.
Effect of Organics. Swenson et al. (1949) observed that several
organic anions were effective in preventing P from combining chemically
with Al and Fe.or by replacing the chemically combined P. Humus and
lignin were effective in replacing P from the basic Fe-P, probably be-
cause of the formation of stable compounds or complexes between active
Fe and humus or lignin. Struthers and Selling (1950) found each organic
acid investigated differed from the other in its effectiveness in pre-
venting P fixation by Fe and Al at different pH values. The organic
acids used by Struthers and Seiling occur in soils as a result of the
action of microorganisms on organic matter. The most effective sub-
stances were those that formed metal-organic complex molecules of great
stability: citrate, tartrate oxalate, malate, and lactate. The dominance
of active Fe or Al in the system will depend largely on pH, redox poten-
tial and stability of the ligands formed. In calcareous sediments the
decrease in P fixation with organic and carboxylic acids from the organic
matter would not be as important so long as solid-phase CaCO~ remained in
control of pH.
Only a minor part of the organic P of soils appears to be present
as nucleic acids and phospholipids. Inositol phosphate form a major
part of the soil organic P thus far identified (Bailey, 1968). Jackman
and Black (1951) found that Fe and Al salts of inositol phosphates were
very insoluble in an acidic medium. Because the pH solubility curves
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38
were very similar to the inorganic orthophosphates, organic compounds
such as phytin and their derivatives should be fixed in soils as insol-
uble Al, Fe and Ca salts.
Phosphorus Sorption and Release at Sediment-Water Interface. The
sorption and release of sedimentary P will depend to some extent upon
the depth to which P effectively exchanges with the water. The loss of
added P fertilizer to a small unstratified Scottish loch was studied by
Holden (1961). Mud core samples showed that P penetrated downwards
through the mud about 2 cm after 8 months and 3 cm in 48 months. Most of
the P removed (85 percent) remained in the upper aerobic zone of the mud
(2 cm below sediment-water interface) and was converted to organic forms,
presumably by bacteria. Zicker et al. (1956) found when radioactive
superphosphate fertilizer was placed at various depths below the mud
surface, the percentage as well as the amount of P released to the water
was small with no P released from depths greater than I/A inch below the
mud surface. Agitation by stirring the muds resulted in approximately
twice the concentrations of P in the water phase compared to undisturbed
systems. The depth of an oxidized microzone of ferric gels across the
mud-water interface was believed by Mortimer (1942) to be maintained by
molecular diffusion of oxygen into the mud, to a distance depending al-
most wholly upon reducing power of the sediment in a given lake.
Mortimer proposed that the thickness of the oxidized layer of mud during
water circulation e.g., after autumn overturn, could be related to the
productivity of a lake. Hayes et al. (1958) questioned whether the oxi-
dized layer is as thick as measurements suggest. Hayes presented evi-
dence that the real oxidized layer of sediments from eastern Canadian
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39
lakes is one mm or less thick, Hutchinson (1957) felt the seasonal
presence or disappearance of an oxidized microzone in the sediments could
be an important influence on the chemical classification of lakes. Gorham
(1958) presented evidence that the thickness of the oxidized microzone at
the surface of lake mud may depend upon turbulent displacement of the
uppermost sediments into the overlying aerated water. The sediments con-
taining Fe become oxidized and then settled to the surface muds forming
the oxidized microzone.
Biological Factors. Bottom dwelling organisms and the abundant
bacteria] flora exert an effect on the transformation of organic matter
and on the alteration of physicochemical properties in sediments which
in turn may influence sorption-desorption reactions of P. Aerobic bac-
teria are dominant in the upper layers, but below the upper layers the
role of anerobic bacteria increases. The redox potential of sediments
is particularly affected in the zone of maximum bacterial activity
(Zobell, 1946). Hayes and Phillips (1958), using both cores and shaken
bottom sediments, presented evidence that, in lakes, bacteria may com-
pete with the sediments for P, reducing the rate of exchange of P be-
tween wat^r and sediments, and retaining P in water as bacterial proto-
plasm. Pomei-oy et al. (1965) felt the exchange of sedimentary P that was
incorporated in bacterial protoplasm was small because the organisms in-
volved were beneath the surface of the sediments; however, the authors
thought the biological P would be exchanged with the water if the sedi-
32
ments were suspended. The distribution of P between mud and water was
studied by Hayes and Phillips (1958) who found the exchange of P with the
mud of natural and artifically prepared Jenkins cor*"- >--as the same. Thus,
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40
the destruction of natural physicochemical and biological layering of the
surface muds did not influence the exchange pattern.
I. Other Wisconsin Lake Sediment Studies
Surface Muds. Juday, Birge and Meloche (1941) analyzed the surface
muds of 18 lakes in northern Wisconsin and 3 lakes in southern Wisconsin
for Si, Fe, Al, Ca, Mg, P, S, carbonate and organic carbon. The same
components were measured by Black (1929) for several lakes in northern
Wisconsin. Steiner and Meloche (1935) determined the lignin content of
Wisconsin lake sediments and found the organic matter contained 30 to 48
percent lignin; higher percentages of lignin were found in northern than
southern Wisconsin lakes. Studies on the composition of the bottom muds
in Lake Mendota were made by Levihn (1951) and Kaneshige (1952). Samples
of the bottom muds were collected and analyzed for soluble and total P,
free ammonia, nitrate, organic N and total Fe. Results of these studies
were presented by Rohlich (1963). The oxidation-reduction potentials and
pH of lake waters and sediments were measured by Allgeier et al. (1941)
for several lakes in northern Wisconsin; the pH of surface muds measured
in si tu ranged from 5.6 to 6.8.
Cores. Twenhofel cored lakes in Wisconsin which included Mendota
(Twenhofel, 1933), Monona (Twenhofel, 1937), Devils (Twenhofel and
McKelvey, 1939), Crystal (Twenhofel and Broughton, 1939), Little Long
(Twenhofel and McKelvey, 1942), Grassy (Twenhofel et al., 1942) and
Trout (Twenhofel et al., 1945) lakes. Most often, Twenhofel and his co-
workers analyzed only the top, middle and bottom of each core; they noted
the physical characteristics and minerology and determined chemical com-
ponents such as inorganic and organic carbon, Si, Al, Fe, Mn, Mg and Ca
-------
41
in the sediment cores. Twenhofel et al. (1944) collected complete core
sequences of the postglacial sediments for several lakes; the maximum.
thickness of the sediments was 9.2 m for Grassy Lake, 4.7 m for Nebish,
5.9 m for Little John and 13 m for Allequash lake. In addition,
Twenhofel et al. (1945) and Twenhofel and Broughton (1939) observed the
thickness of sediments were 4.8 m for Trout Lake and 3 m for Crystal
Lake, respectively. Sawyer et al. (1944) obtained cores from Lake
Mendota as well as the three lower lakes. To evaluate the quantity of
N and P that could be released from the sediments, Sawyer et al. leached
one liter samples of surface mud cores from the lower Madison lakes with
Lake Mendota water. From the slope of the curves for nutrient release
after 50 or 60 days digestion, it appeared the release of nutrient
materials from bottom muds was very slow. Conger (1939) studied the
diatoms in the cores from Crystal Lake and found unexpected diversity
both in biological stratification and in the horizontal distribution of
diatoms. The diatom flora was more diverse at the bottom of the cores,
and several middle samples were dominated by Fragilaria construens, in-
dicating rich "blooms" of this species. Acid tolerant diatoms indicated
a change toward greater acidity in the upper sediments.
Studies on pollen chronology, bacteria and benthos of Wisconsin
lakes and bog sediments are discussed in a review paper by Frey (1963).
J. Summary
Although several chemical studies have been performed on postglacial
sediments and interpreted on the basis of long-term trends (Brown, 1969;
Gorhara, 1961; Horie, 1966; Hutchinson and Wollack, 1940; Kendall, 1969;
Livingstone and Boykin, 1962; Pennak, 1963; Vallentyne, 1969), few
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42
investigators have given sustained study to the most recent changes in
lake history. Additional studies are needed to examine the effect man
has played in causing changes in the sedimentary environment. Episodes
involving the dynamic aspects of lakes will continue into the future, but
the rates, dates and relative changes that have occurred will remain
speculative until more data are collected about the past history of lakes.
Studies need to be conducted on the P sorptive-desorptive capacity and
nutrient leaching potential of the pre- and postcultural sediments in
order to suggest limnological implications due to culturally-influenced
changes in chemica.1 composition of the sedimentary profiles. Closer
attention needs to be given to such complexities as - dimentation rates
mixing of sediments and replicate coring within the same lake in order to
better evaluate and interpret concentration vs. sedimentary depth profiles.
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43
CHAPTER III
EXPERIMENTAL PROCEDURES
A number of lakes in northern and southern Wisconsin were studied
in varying detail. This chapter describes the lakes, sampling locations,
laboratory techniques and procedures used in this endeavor. A general
view of the lakes studied is given in Figure 3.1. The lakes in Vilas
and Oneida counties are situated in stony, sand}', noncalcareous, glacial
drift. The upper ground water is notably soft. The soils of the Madison
lakes drainage basin are a silty loam which overlie sandstone and dolo-
mite. Devils Lake is situated in a quartzite region.
Some hydrologic, morphometric and chemical characteristics of each
of the study lakes are summarized in Table 3.1. Most of the hydrographic
and morphometric data was obtained from the Wisconsin Conservation Depart-
ment surface water resources reports (Poff and Threinen, 1962; Black
et al. 1963; Andrews and Threinen, 1966). The water chemistry data was
obtained by Water Chemistry students and staff in 1965-1967.
A. Natural Environment
The coring stations on subsequent lake maps are indicated by black
circles.
Lake Mendota is a hard-water eutrophic lake formed by morainic
damming of the preglacial Yahara River valley (Twenhofel, 1933). In
addition to several springs, three principal streams enter the lake.
The lake currently receives domestic drainage from agricultural lands,
urban runoff, and some municipal and industrial waste effluents contained
in entering streams. Four cores were taken from Lake Mendota in
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44
Area
County
Dane, Sauk
Vilas, Oneida
Lakes
Mendota, Monona
Wingra, Devils
Trout, Little St. Germain
Weber, Sparkling, Minocqua
Little John
Figure 3.1 State of Wisconsin Showing General Location
of Lakes Studied.
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Table 3.1 Some Limnologic, Hydrologic and Morphometric Characteristics of Study Lakes.
Productivity classification a
b
0 In hypo) imnetlc water
2
Alk. (mg CaCO /I
Cond. (>imlio*/c»/20° C)
c
Maximum depth (m)
Mean depth (m)
Shore 1 tne deve lopment
factor ufl
eutroph ic
0, deple t Ion
s u mme r a nd
winter
44-60
RO-150
D
5 1 200
18.3
...
3.68
Little St.
erma n
eutrophic
0^ depletion
summer and
winter
35-65
70-90
D
9350
9 59
17
3.P8
3.23
e t e o n
o 1 igo trophic me sot rophic-
e\jtrophlc
0, present some 0 dcplf-
summer and tion in winter
winter
3-6 33-52
6-20 73-100
S Spr
1 28 704
11 1 66
13.5 6.P
7.24 3.77
1.14 1.65
Spa rk 1 1 ng
o 1 i gi«t rnphic
mesot rt'ph Ic
stinte o, dfpU--
t ton i n suf'»Ti«'r
30-36
55-65
s
640
\ 27
19.5
11.3
1.31
b
d
11
Based un an observed aquatic weed and algal growth, 02 depletion in hypolImnion, alkalinity and conductance of lake water.
Water cht-mistry data represents a ranRC of valuea obtained from deep area of lakes during summer, fall and winter sampling trips in 1965-1967; values will depend on season of yrar,
depth of water, snow cover and location within lake.
D drainage lake has outlet and inlet. S seepage lake has no outlets and Inlets; intermittent outlet may be present; water level maintained by groundwater and basin seal.
Spr spring lake seIdom has inlet, but always has outlet of substantial flow.
^ 1" the ratio of the length of shoreline to the circumference of a circle equal to the area of the lake; the quantity can be regarded as a measure of the potential effect of
ittoral processes on the lake. With Increased littoral area greater biological product ivity can be expected.
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46
progressively deeper water following a transect from University Bay to the
center of the lake as shown in Figure 3.2. University Bay has two inlets:
an inlet coining from a pumping station of lowland drainage and a small
creek, University Creek, which serves as a storm sewer for urban Madison.
Lake Monona is the second in the series of morainic dammed lakes of
the Yahara River. During the periods of 1898-1936 and 1942-1950, Lake
Monona received the treated sewage from the City of Madison. Copper sul-
fate was systematically applied from 1925 through 1953 to control algae
blooms (Nichols et al. 1946). The pollutional history of the Madison
lakes is discussed by Stewart and Rohlich (1967), Sarles (1961) and Sawyer
et al. (1944). The bathymetry and coring stations of Lake Monona are
given in Figure 3.3.
Lake Wingra is a small, shallow, eutrophic lake. The present water
supply of Lake Wingra is provided by surface drainage, springs and storm
sewers. Many springs which provided Lake Wingra with a steady flow of
water have been replaced as sources of water by storm sewers (Noland,
1951). Nearly 200 acres of shrub and marsh land adjoin the lake. Some
1imnological aspects of Lake Uingra are reported by Tressler and
Domogalla (1931). A single core was obtained in the deep basin in the
east-central part of the lake in 3.4 m of water.
Devi1s Lake is an oligotrophic-mesotrophic lake of soft clear water.
The lake has only two small streams entering it and no streams leaving
it. Evaporation and seepage control the losses (Black, 1968). A single
core was taken from the southern basin in 13.1 m of water.
Trout Lake is a deep, clear, oligotrophic-mesotrophic lake situated
in state forest land. Four small streams flow into Trout Lake and one
stream flows out. There is considerable flow into the lake by seepage
-------
LAKE MENDOTA
1 mile
Contour Intervals
in Meters
fC-IR,UR
I1IR, IVR
Figure 3.2 Bathmetry and Coring Locations for Lake Mendota.
-------
LAKE MONONA
Contour Intervals
in Feet
Figure 3.3 Bathymetry and Coring Locations for Lake Monona.
co
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49
(Twenhofcl et al., 1945). Cores were taken from the central basin of both
North and South Trout Lake. A bathyinetric map and coring stations of Trout
Lake are shown in Figure 3.4. The map includes an insert of the Trout Lake
region showing the location of Sparkling, Weber and Little John lakes.
Hinocqua is a soft-water drainage lake having slightly acid, light-
brown water of moderate transparency. Aquatic vegetation and algae are
problems in parts of the lake basin. Fifteen resorts, four marinas, 271
dwellings and the town of Minocqua are located on the shores. Less than
4 percent of shoreline is public. During the period 1935-1964 the sewage
from a secondary treatment plant serving the town of Minocqua was dis-
charged to a small bay located near the town which then flowed to the
northwest bay of Lake Minocqua (F.H. Schraufnage 1, Personal Communication,
Wis. Dept. of Natural Resources, 1969). Water levels are maintained by
a water control structure with a 4-foot head on the outlet of Keweguesaga
Lake. A bathyinetric map and coring stations are shown in Figure 3.5.
Little St. Germain is a shallow eutrophic lake with an extensively
developed shoreline. On the 13 miles of shoreline there are 100 private
cottages and 46 resorts. Aquatic weed growth has been a problem on the
lake. The inlet and outlet streams are considered navigable water. A
5-foot dam maintains water levels, and the upper 22 inches is used for
water storage and low flow augmentation of the Wisconsin River. A bathy-
metric map and coring stations are shown in Figure 3.6.
Weber Lake is a small, oligotrophic, seepage lake, having slightly
acid water. There are no private or commercial developments on the
shoreline. The lake has been free of modifying activity of campers and
fishermen, but scientific studies involving the addition of fertilizer
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50
Contour Intervals
in Meters
1 mi le
TROUT LAKE
TROUT LAKE REGION
LITTLE JOHN LAKE
WC-59
Figure 3.4 Bathymetry for Trout Lake and Coring Locations for Trout
and Other Vilas County Lakes.
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51
MINOCQUA LAKE
WC-51
Inlet from
Kewaguesaga
Lake
WCD Map
N.W. Bay
Village of
Minocqua
Contour Intervals
in Feet
Figure 3.5 Bathymetry and Coring Locations for Lake Minocqua.
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East Bay
LITTLE ST. GERMAIN LAKE
WC-92
%x Lake Survey Map Pub-
lished by Little St. Germain
Lake Improvement Association
1750 ft
Contour Intervals
in Feet
Figure 3.6 Bathymetry and Coring Locations for Little St. Germain Lake,
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53
were carried out from 1932-1939. A core was obtained from the center of
the lake in 12.6 m of water.
Little. John Lake is a shallow spring-fed lake of high fertility.
There is a small outlet stream. Most of the shoreline is public frontage.
A core was obtained from the 5 m basin in the center of the lake.
Sparkling Lake is a oligotrophic-mesotrophic seepage lake surrounded
by forest. The shoreline is 87 percent in public ownership. A core was
obtained in the south-central basin in 18.8 m of water.
B. Field Sampling Methods
Sediment Collection. Surface sediments were collected from the
lakes by use of an Ekman dredge. Sediment core samples of one meter
length were collected by a piston-operated coring device of large diameter
(3.5 inch i.d.). The design and operation of the piston corer was de-
scribed in detail by Wentz (1967) and Bortleson (1968). A sampling plat-
form was provided by a converted Army Amphibious Dukw. A 10 m core from
Lake Mendota was taken using four connected 10-foot lengths of galvanized
1-1/2 inch (i.d.) pipe. The corer was piston-operated with 1-1/2 inch
(o.d.) plastic cellulose acetate liners inserted in the pipe. The cores
were extruded immediately in 5-cm lengths and placed in commercial poly-
ethylene "sandwich" bags. The samples were frozen until commencement of
the analysis.
TV-JO long cores were collected from Little St. Germain by the
University of Wisconsin Geology Department and the Wisconsin Geological
and Natural History Survey by using a modified Livingston peat sampler of
2-inch diameter up to one meter in length. Overlapping lengths of core
were taken to yield complete sequences of sediment. The cores were
-------
54
extruded, cut into five-inch segments, put into glass jars and later
refrigerated.
C. Analytical Procedures and Apparatus
Preanalysis of Sediments.
The steps that were followed to prepare the sediments for dry or
wet analysis are outlined below.
Drying and Grinding. After thawing, the samples were stirred in a
Waring blender to make each sample homogeneous. Samples needed for chemi-
cal analysis and percent solids determination were placed in petri dishes
and dried at 105 C for 12-16 hours in a Fisher Isotemp Oven. A simul-
taneous density measurement of the sediment was obtained by taking the
sample with a 50 cc, large orifice, plastic syringe. The sample was
ground with a porcelain mortar and pestle and passed through a 100-mesh
screen. After grinding, the samples were reintroduced into the oven for
3-4 hours at 105 C. For wet analysis, such as determining exchangeable
ammonium, samples were obtained and run immediately.
Digesting. The sediment was brought into solution using HF pre-
digestion followed by HC10.-HNO digestion. Sediment samples (0.500 g)
were placed in 35 ml polypropylene beakers and heated on a steam bath in
the presence of 5 ml of 48% HF. Polypropylene beakers were supported over
the steam bath by a Incite plate with holes for the beakers. After heat-
ing the solution for 10-12 hours, the residue was transferred to a 100 ml
Kjeldahl flask and digested with 10 ml of HC10 -HN03 (3 parts 607. HCIO^
and 5 parts concentrated HNO by volume) using an AMINCO (American
Instrument Company) 12-burner digester assembly set up in the fume hood.
Heating of the digestion mixture was continued until heavy white fumes of
-------
55
HC10/ appeared. A trap was provided to catch the HC10, fumes.
Filtering and Diluting. After the digestion, the samples were
cooled, filtered through Whatman #2 filter paper into 100 ml volumetric
flasks, diluted to volume and mixed. Aliquots v;ere taken from the 100 ml
dilution volume representing 0.500 g of sediment for total P, Fe, Mg, K, Ca,
Mn and Al.
Chemical Methods.
All reagents used were ACS grade chemicals.
Total carbon was determined by a dry combustion technique using a
LEGO (Laboratory Equipment Corporation, 1959) low carbon analyzer (Model
589-400) and LECO induction furnace. The CO released by combustion of
carbon compounds and decomposition of carbonate is measured by a thermal
conductivity cell. The sample in a carbon-free ceramic crucible contain-
ing iron and tin chip accelerator is combusted in 3 minutes at approxi-
mately 1500 C with an 0 flow rate of 1.5 liter/rain. The gases are
reacted with a catalyst to oxidize CO to CO . and with MnO to remove
22
sulfur and nitrogen oxides. The recovery of carbon by dry combustion of
pure compounds of glucose and CaCO was 98-100 percent.
A direct weighing of the high carbon-containing sediment samples was
not practical since the optimum working range for the low carbon analyzer
is 0.030 to 0.50 mg of carbon. In order to obtain at least a 30 mg
weighing, the sediment samples were diluted with powdered silica (140
mesh) 10:1 or 20:1. Several blank determinations containing powdered
SiO showed no detectable carbon. Homogeneity of the powdered silica and
sediment sample was effected by shaking and vibrating the mixture together
in a 1-oz bottle. A mixture of CaCO and SiO was checked for homogeneity
-------
56
using subsamples for carbon determination. The carbon recovery was 98-
100 percent (Bortleson, 1968). A calibration line was established using
either LECO standards or a CaCO -silica mixture containing 0.030, 0.15,
0.30, 0.45 and 0.54 mg carbon.
The output of the thermal conductivity cell was measured on an inte-
grator clock or a Moseley Autograf (Model 680) recorder. A comparison
of total carbon determinations using the integrator and peak height
methods is shown in Table 3.2.
Table 3.2 Concentration of Carbon Observed in Sediment Using Peak
Height and Clock Integrator Methods.
Mean +0- mg C/g Mean + a~ mg C/g
Sample Replicates Integrator Method Peak Height Method
L. Mendota - WC 82 5 149 + 1.6 a 145 +2.6
Section 5
L. Mendota - WC 82 5 113+3.3 114+3.2
Section 15
L. Mendota - WC 84 5 103+3.6 103+3.5
Section 4
L. Mendota - WC 84 5 153 +3.2 150+2.0
Section 14
a Standard deviation,
Organic Nitrogen. Organic nitrogen was determined by semimicro
Kjeldahl technique which involves three basic steps: 1) digestion of
the sample to transform the nitrogen to (NH )? SO , 2) distillation of
ammonia gas freed from the ammonium sulfate by NaOH and 3) measurement
of the distilled NH by titration. The procedure is outlined by Bremner
(1965) and described in detail by Bortleson (1968).
Exchangeable Ammonium. No generally accepted definition of
-------
57
exchangeable ammonium is available, but for analytical purposes in soils
literature it is usually defined as ammonium which can be extracted by
KC1 (or K SO ) solution at laboratory temperatures (Brenmer, 1965). The
extract from this treatment is analyzed by steam distillation methods.
Alternatively, a sample can be treated with 2 N KC1 and analyzed directly
by the same methods. The possibility of interference by organic soil N
compounds is clearly greater in this procedure than in those involving
extraction, but analyses of a large number of soils have shown that the
results by this direct procedure are in close agreement with those
obtained using extraction procedures (Bremner, 1965). The procedure in-
volves 1) steam distilling of a wet sample of sediment in the presence of
2 N KC1 and MgO and 2) titrating the distilled NH . A wet sample of mud
was placed in a 50 ml Erlenmeyer flask, stoppered and weighed. A separate
sample was taken for percent solids determination in order to base the
analysis on dry weight. After weighing, the sample was transferred to a
100 ml Kjeldahl flask to which was added 10 ml of 2 N KC1 and 0.1-0.2 g
of MgO. Small amounts of MgO were added to minimize the interference
from alkali-labile organic N compounds. The sample was steam-distilled
into an indicator boric acid solution and titrated with 0.01 N HC1.
Total Phosphorus. The P determination has two distinct phases:
first, the preparation of a solution containing the sediment P or fraction
thereof, and second, the quantitative determination of the P in solution.
Two methods were used in the preliminary L _riments to extract total P
from the sediments: 1) HC10 -HNO digestion and 2) HF predigestion
followed by HMO-H SO, digestion. A comparative evaluation of these acid
procedures for the determination of total P on Lake Mendota sediments is
reported by Bortleson (1968). Syers et al. (1968) have compared several
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58
fusion and acid procedures for the determination of total P in soils
and parent materials. The P in the digest was determined by the
vanadomolybdophosphoric (VM) yellow colorimetric procedure (Jackson,
1958). This method is well suited for sediment analysis because of its
lower sensitivity (1 to 20 ppm of P), color stability, freedom from
interferences with a wide range of ionic species up to 1000 ppm and
adaptability of HNO , HC1, H SO, and HC10 systems (Jackson, 1958).
3 2 ^ ^
Appropriate aliquots from the original digest (0.500 g in 100 ml)
were pipetted into 50 ml volumetric flasks. In order to control the
acidity which may vary with aliquot size and carbonate content of the
sediment, the pH was adjusted to the 2,6, dinitrophenol colorless end-
point (pH 2 colorless - pH 4 yellow). Ten ml of color-forming vana-
domolybdate reagent [25 g (NH^)6 Mo 0 ^ 4H 0, 1.25 g NH V03, and 250
ml of concentrated HNO diluted to 1 liter! was added to a 50 ml volu-
metric flask. The acidity obtained from the combined volumes and reagent
concentration was approximately 0.8 N. The acid concentration of the
determination is not critical, but the final concentration must be above
0.5 N and not over 1.0 N. The effect of acid concentration on the VM
yellow color intensity is shown in Figure 3.7. A plateau is observed in
which the color intensity is not affected by acid concentration. The
plateau also narrows as the P concentration increases and widens as it
decreases. After having allowed at least 20 minutes for full color
development, the absorbance was measured by a Beckman DU Spectrophometer
at 440 mu using a blue photocell. This wavelength is suggested by Jackson
for working concentrations from 2.0-15 ppm P, which is a typical range
obtained from a 5-35 ml aliquot diluted to 50 ml. A light maximum from
400 to 490 mu is used depending on the sensitivity needed, but ferric
-------
O.
CM
c
0)
!-i
oj
Q.
O.
20 --
16--
12 --
4 ..
Figure 3.7
Apparent P vs Acidity
at Different P
Concentrations Using
Vanadomolybdophosphoric
Yellow Color Method.
0.8
Acidity (N)
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60
ion causes interference with the lower wavelengths, particularly at 400 mu
(Jackson, 1958). Calibration curves were established for different cell
lengths as follows:
range, mg P/l cell length
0.2-2.0 10 cm
0.5-4.0 5 cm
1-10 2 cm
2-20 1 cm
Phosphorus standards and blanks were prepared by carrying the known
concentrations through the total P digestion procedure. Experiments
showed, however, that the total P standards which were not carried through
the procedure measured the same absorbance. This shows within limits, at
least, that the VM yellow color complex is not affected by changes in
acid and salt concentrations.
Wentz and Lee (1969a) have discussed the sensitivity, minimum detect-
able concentration, precision and working range for the VM yellow color
procedure.
Acid Soluble Phosphorus. This is an operationally defined procedure
for extracting P from lake sediments in a 1 N solution of HC1 (0.75 N) and
H SO, (0.25 N). Shah et al. (1968) compared the amount of inorganic P
2 4
extracted by IN H SO (P ) from a range of New Zealand soils with certain
2 4 a
forms of inorganic P determined by a fractionation procedure of Williams
et al. (1968). It would appear from their results that the P fraction
a
can, as a first approximation, be equated with the sum of acid extractable
Ca-P + NH F-P + NaOH-P.
4
Twenty ml of strong acid extractant was added to 0.200 g of sediment
in a 50 ml Erlenmeyer flask. The sediment solution was shaken for 15
minutes at 22 C,filtered through a prerinsed 0.45 p Millipore and diluted
to 50 ml. An appropriate aliquot of the filtrate was taken for P analysis
-------
61
using the VM yellow method.
Iron was determined by the orthophenanthroline colorimetric technique
(Olson, 1965) or by atomic absorption using a Perkin-Elmer (Model 303)
spectrophotometer. Iron standards were prepared ranging from 0.2 to 2.5
ppm and 1.0 to 10.0 ppm for the colorimetric and atomic absorption methods,
respectively.
Aluminum, calcium, magnesium, potassium and manganese analyses were
determined by atomic absorption. The manufacture's recommended instru-
ment settings and procedures were employed. A nitrous oxide-acetylene
flame was used for Al analysis. Appropriate aliquots of the original 100
ml digest solution were taken to make dilutions in the working range of
each of the determinations.
Sulfide sulfur was determined by a modified Standard Methods (1965)
iodometric titration. Potassium biniodate was substituted for iodine
solution and steam stripping of H S was used instead of CO stripping.
The determination was carried on the AMINCO steam distillation apparatus.
Ethanol was added to suppress foaming of acidified carbonate-containing
sediments.
Organic Carbon and Carbonate Carbon. For calcareous sediments the
analytical problem is to differentiate between the two forms. For the
noncalcare.ous sediments of the northern lakes, total C is considered to
be organic C. Total C can be determined by dry combustion as discussed
previously. With calcareous sediments, the choice is between determining
organic C on the sample after removal of carbonate C or computing organic
C by substracting carbonate C from total C. In all quantitative determin-
ations of CO -C, the CO released from the carbonates on treatment with
acid is measured volumetrically, titrimetrically or gravimetrically. The
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62
basic problem is to ensure complete decomposition of the carbonate with-
out hydrolyzing some forms of organic matter by the process of decarboxy-
lation.
A number of methods were evaluated for the determination of organic
C and carbonate C in calcareous sediments from Lake Mendota WC-86 as
shown in Table 3.3. Only the carbonate C is presented in Table 3.3;
organic C can be found by difference from total C. The methods used for
each of the determinations are as follows:
1. Acid Neutralization. Samples were acidified with excess 0.5
N HC1, boiled gently to drive out CO , then filtered and titrated to the
phenolphthalein endpoint with 0.25 N NaOFI (Allison and Hoodie, 1965).
This method of determining carbonate C may be high if other constituents
react with acid, or low if constituent?- (such as Fe) react with base.
2. Soluble Ca from HF-HNO-j-HClO^ Digestion. The Ca dissolved in
this acid system would include the carbonates as well as minerals. This
method assumes the Ca is present as carbonate and no measureable Ca is
bound to the silicate fraction. The Ca measured is converted to CO -C
equivalents. The assumption that additional Ca in the mineral structures
in a high-carbonate sediment (30-80%) would not be a measureable quantity
was tested in method 3.
3. Soluble Ca from HNCs-KClO^ Digestion. This digestion method
would dissolve all carbonates + exchangeable Ca + an undefined fraction.
The undefined fraction would not include Ca incorporated into the sili-
cate mineral structure. The Ca measured is converted to CO^-C equiva-
lents. A comparison of method 2 and 3 show less than 10 percent
difference throughout the core.
4. Acid Pretreatment. A 50 mg sediment sample (mixed 10:1 with
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63
Table 3.3 Comparison of Carbonate Carbon Determinations on Lake
Mendota Core WC-86.
Depth of
Core (cm)
0-5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
80-85
85-90
90-95
95-100
a Method 1
2
3
4
5
1
40.4
36.7
38.2
36.
37.
40.
40.
41.
41.
49.
60.
73.
83.
81.
80.
76.
75.
79.
78.
77.
7
9
7
5
4
0
3
2
7
8
5
2
9
0
0
3
1
2
31.
29.
30.
28.
28.
31.
31.
32.
32.
39.
47.
65.
76.
76.
75.
71.
72.
77.
75.
74.
mg
,8
4
3
2
2
8
8
7
4
0
7
4
5
5
0
4
0
6
9
8
Method a
3
co3-c/g
31,
27.
28.
26.
28.
31.
31.
33.
33.
39.
48.
60.
75.
73.
72.
68.
67.
73.
73.
72.
,8
3
.5
7
5
5
8
0
0
3
4
3
0
2
0
5
0
2
9
0
4
31.
28.
23.
31.
27.
34.
28.
38.
25.
43.
63.
58.
70.
69.
58.
56.
67.
65.
72.
63.
8
0
9
0
8
5
1
2
1
1
0
5
0
6
0
3
2
0
0
9
48
43
47
42
42
52
43
42
40
48
57
73
87
78
72
75
80
83
79
.5
.0
.2
.4
.3
.5
.0
.7
.3
.3
.5
.0
.6
.1
.8
.9
.0
.0
.0
5
(38)
(38)
(46)
(46)
(46)
(46)
(46)
(46)
(46)
(46)
(46)
(46)
(67)
(67)
(67)
(96)
(96)
(96)
(96)
- Acid neutralization
- Soluble
- Soluble
Ca from
Ca from
- Acid treatment
- LTA
numbers
HF-HN03-HC104
HN03-
prior
HC10.
4
to dry
di
digestion
gestion
combustion
in parenthesis
are hours
of LTA
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64
silica) was treated with 0.75 ml of 6 N HC1 and 0.25 ml of 5 percent solu-
tion of SnCl in a vicor crucible. The SnCl is used as an antioxidant
2 2
(Allison and Moodie, 1965). The sample was placed in a heated vacuum des-
iccator (Precision Scientific Co.) for 7 hours at room temperature and 2
hours at 55 C using full water aspiration for vacuum. The remaining or-
ganic matter was determined by dry combustion using the LEGO carbon analyzer.
5. Low Temperature Ashing (LTA). Sample ashing was performed in a
TracerLab LTA-600 to remove organic carbon (the remaining carbonate C was
determined by dry combustion using the LEGO carbon analyzer). Oxygen flows
into a common inlet manifold, and, at reduced pressure and low flow rate,
passes through five separate vertical tubes surrounded by a single radio
frequency (r.f.) coil. The r.f. coil 'generates a high frequency electro-
magnetic field in which the molecular 0 is converted to excited, very
reactive atomic and ionic species. Volatile products of combustion and
excess 0 are drawn into an exhaust manifold and removed by means of a
2
vacuum pump.
The sample weight in each ceramic combustion boat was 40 mg. The
chamber pressure was 1.0 mmHg or less; oxygen flow rate was 65-70 cc/min,
and the power to the coil was 240-250 watts. The instrument was not pro-
vided with a thermocouple to determine ashing temperature. However, it
was expected to be less than 125°C (Personal Communication, Tracer Lab,
1969). The time of ashing varied as shown in Table 3.3. Carbon recovery
was checked after LTA using various glucose and CaCO ratios. The LTA
removes organic carbon effectively in the presence of CaCO in a pure
system as shown in Table 3.4.
The standard deviation for each of the methods given is shown in
Table 3.5. The relative standard error is less than 5 percent for all
methods. Acid pretreatment and LTA methods gave the highest standard
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65
Table 3.4 Carbon Recovery of CaCO and Glucose After Low Temperature Ashing.
Sample
CaC03
Glu:CaCO
4:1 J
Glu:CaCO
1:4 3
Theoret
Sample
glu
--
320
80
ical C in
(mg C/g)
CaCO
3
120
24
96
Carbon after
48-56 hr (mg
119
27
99
LTA for
c/g)
deviation. The acid pretreatment method has the disadvantage of hydro-
lyzing some of the organic material upon acidification. Low temperature
ashing requires at . least 35 hours exposure to the excited 0 to obtain
2
complete oxidation of the organic material in sediments. The carbonate
carbon values in Table 3.3 appear to be high for the LTA method, thus in-
dicating incomplete oxidation of organic carbon. The mineralogy and com-
position of the sediment could change the acid and base reactions with
noncarbonate materials in the acid neutralization procedure.
Methods 2 and 3 were used in this study to determine CO -C for the
lakes in southern Wisconsin which contain 25-80 percent carbonate. The
Ca dissolved by HF-HNO -HC10 or HNO -HC10, acid systems was converted to
CO -C equivalents. From the practical standpoint, the CO -C determination
J J
by method 2 and 3 are the most rapid and reproducible to perform. A com-
parison of the two acid systems show no measurable Ca is added by HF
treatment. The extent to which dolomite contributes to the carbonate is
not known. It has been observed that the Mg profile does not increase in
the marl layers like the Ca profile. Therefore, some evidence is given
that Mg may be derived mostly from other mineral sources. However, a
-------
Table 3.5 Precision of Carbonate Carbon Determinations on Lake Mendota WC-86.
Method Section Analysis
1
2
3
4
5
5~
( cm)
- Acid neutralization 35-40 CO--C
80-85 CO -C
3
- Soluble Ca from HF-HNC^-HCIO^ 35-40 Ca
digestion
70-75 Ca
- Soluble Ca from HNO -HC10 35-40 Ca
*3 /
digestion J
70-75 Ca
- Acid pretreatment prior to 10-15 Org-C
combustion
- Low temperature ashing 85-90 CO -C
- standard deviation
_ volot-iiro c^ar^/^ar/-^ oT-rm- = y 1 DD
Replicates Mean
(mg/g)
3 41.4
5 75.0
5 109
5 250
5 110
5 241
5 68.5
5 79.9
cr e
+ 0.3 0.7
+ 0.3 0.4
+1.1 1.1
+ 0.7 0.2
+ 0.9 0.8
+ 2.5 1.0
+ 1.0 1.4
± 2'9 3'6
mean
-------
67
certain percentage of any dolomite would be accounted for in the soluble
Ca method. Turekian (1940) used a similar method to determine the car-
bonate content of deep sea cores. The Ca and Mg were dissolved in 6 N HC1,
measured by EDTA titration and converted to CaCO equivalents.
Pollen Analysis
Processing Lake Sediments for Pollen Analysis. Chemical treatment
of sediments with both mineral and organic fractions consists of deminera-
lization and solublization and/or chemical conversion of residual organic
matter to soluble products. The steps consist of removal of carbonates
with HC1, silicates with HE, solublization of humic material with KOH and
removal of cellulose with acetolysis solution. Aqueous alkaline solutions
are used to eliminate the large lignin-humus fraction of the sediments.
The dark-brown humic compounds are then washed free from the sample. The
acetolysis solution consists of concentrated H SO to bring about the
depolymerization of cellulose structures and acetic anhydride to convert
cellulose to cellulose triacetate. Cellulose triacetate is not soluble in
water but is soluble in glacial acetic acid. The following procedure was
used for processing the lake sediment for pollen analysis as modified from
Faegri and Iverson (1950), Anderson (I960), and Maher (1969):
o
1. Weigh 0.200 g of sediment (100 mesh, dried 105 C) in 100 ml beaker.
If sediment is calcareous, add 10-15 ml of 10% HC1; heat gently. Add acid
until effervescence stops.
2. Add 0.20 ml of internal standard (1 g of eucalyptus pollen in 500 ml
tertiary butyl alcohol). Stir with magnetic stirrer for 10-15 min to sus-
pend pollen before pipetting and adjust temperature of internal standard to
27.5°C + 0.5°C before pipetting.
-------
68
3. Swirl the sample and transfer to 12 ml centrifuge tube; centri-
fuge immediately, decant, wash with water, stir, centrifuge and decant.
The centrifuge used was International Clinical (Model CL).
4. Transfer sample to same 100 ml beaker and add 15-20 ml of 10%
KOH. Boil mixture gently on hot plate for 10 min and stir to prevent
bumping. Transfer to 12 ml centrifuge tube, centrifuge and decant (check
that solution is not turbid). Wash with water, stir, centrifuge and de-
cant. Repeat if necessary until supernatant water is fairly clear.
5. Transfer sample with 10-15 ml 48% HF to 100 ml teflon beakers.
Boil gently on hot plate in fume hood for 3 to 5 min (up to 10 min), then
cool and transfer sample to 12 ml centrifuge tube. Wash residue from
beaker with a fine jet of water, centrifuge and decant. If a white pre-
cipitate (CaF ) occurs, add 5-10 ml 10% HC1 and heat to boiling; immedi-
ately centrifuge and decant. Wash with water, stir, centrifuge and decant,
6. Wash with approximately 5 ml of glacial acetic acid, stir, cen-
trifuge and decant.
7. Add 5 ml acetolysis solution (make fresh each lab period by
adding 1 part concentrated H SO to 9 parts acetic anhydride in a small
2 4
graduated cylinder). Place tube in boiling water bath for 5 min. Remove
immediately, centrifuge and decant. Add 5 ml glacial acetic acid, stir,
centrifuge and decant.
8. Add 10 ml tertiary butyl alcohol, stir, centrifuge and decant.
Add 5 ml tertiary butyl alcohol, stir, centrifuge and decant. Repeat if
desired.
9. Add about 1.5 ml tertiary butyl alcohol, stir and pour concen-
trate into a 2.5 ml shell vial and flush tube with a fine jet of tertiary
butyl alcohol. Place shell vial into the centrifuge tube, centrifuge and
decant.
-------
69
10. Add enough silicone fluid (2,000 cs) to cover the pollen resi-
due (more can be added later), and allow the uncorked vial to stand over-
night in a dust-free environment to let the solvent alcohol evaporate.
Cork and label.
Counting Ragweed Grains. The prepared sediment sample was diluted
with additional silicone fluid and stirred well with a toothpick before
mounting on a glass slide. Identification of "Ambrosia-type" pollen were
made with high power magnification using a Bausch & Lcmb microscope. No
reference was given to a particular species of ragweed. The eucalyptus
pollen were easily identifiable triangular-shaped grains. Continuous
sweeps were made across the entire width of the preparation. The cover
slide during the counting was often tapped to turn or move grains to
facilitate their identification. In each sample 100 to 200 grains were
counted.
Leaching Studies
Aeration Experiment. Samples of wet mud were placed in Pyrex vessels
containing 20 1 of distilled water. Laboratory compressed air was passed
through cotton packing and a water trap, then into the bottom of each ves-
sel through an air diffuser. The air was bubbled at a rate sufficient to
keep the sediment in partial suspension throughout the experiment. A mag-
netic stirrer with a teflon coated bar was also used to maintain constant
mixing. The vessels were also covered to keep out the light.
Sample aliquots (350 ml) were removed by a siphon tube located at the
midsection of the vessel. Before and during siphoning the entire water-
sediment mass was throughly mixed with a long glass stirring rod to ensure
that a constant solid to solution ratio was maintained after each sampling.
-------
70
The saraples were centrifuged at 1800 r.p.m. for 20 minutes. Conductance,
pH and (KO^ + NO + NH )-N were determined on the supernatant. The
leachate was' filtered through a prerinsed 0.45 ju Millipore filter, then
soluble P and alkalinity were determined.
(Ammonium + Nitrate + Nitrite)-N was determined with steam distilla-
tion in the presence of MgO and Devarda alloy (Al, Zn, Cu) followed by
titration with 0.002 N HC1. Devarda alloy is used to reduce N0~ and NO"
to ammonia which is liberated by steam and collected in boric acid-
indicator solution (Bremner, 1965). This method of steam distillation is
not affected by various organic and inorganic substances which interfere
with colorimetric methods of determining ammoniuin, nitrate and nitrite.
An attempt was made to determine separately ammonia by nesslerization
(Standard Methods, 1965) and nitrate by the modified brucine procedure
(Jenkins and Medsker, 1964), but difficulty was encountered because of
apparent interferences. The accuracy and specifity of the MgO-Devarda
alloy methods for ammonia N liberation in the presence of NO , NO , NH
and organic compounds is illustrated by Bremner (1965).
Soluble P was determined by filtering the sample through a 0.45,u
Millipore and determining P by the molybdenum blue method using SnCl
reducing agent (Standard Methods, 1965).
pH was determined with a Beckman Electromate (Model 1009) or a
Expandomatic (Model 76) pH meter with a Beckman combination electrode.
Conductance was determined with a YSI (Model 31) conductivity bridge.
Adsorption and Desorption of Inorganic P on Sediments
The method followed was that of Williams et al. (1970) with various
modifications. Oven-dried sediment (0.400 g) was placed in tared 50 ml,
round-bottom, centrifuge tubes. Twenty ml of 0.2 N NaCl containing 0, 10,
-------
71
Table 3.6 Mean, Standard Deviation and Relative Standard Error for
Chemical Analysis of a Calcareous and Noncalcareous Lake.
Analysis N
X
Total -C 5 128
168
Org-N 5 7.08
NH.-N 5 0.073
0.21
0.20
P 5 0.538
0.507
0.742
Acid sol-P 5 0.284
0.
Fe 58.
7.
646
04
96
2.00
Mn 5 0.
0.
0.
562
622
276
Ca 5 233
318
Mg 5 10
9.
6.
K 55.
5.
0.
Al 5 31
30
8.
N = replicates
.2
10
02
67
45
53
.3
.5
2
Wingra
(WC-92)
e
7.0 5.5
8.6 5.1
0.36 5.1
0.009 12
0.014 6.7
0.040 20
0.0032 0.59
0.006 1.1
0.081 1.1
0.0010 0.35
0.0087 1.
0.
0.
0.
0.
0.
0.
4.
8.
0.
0.
0.
0.
0.
0.
0.
0.
0.
20
33
78
0
012
0
4
0
22
22
59
13
03
059
28
21
17
2.
4.
3.
0.
1.
0.
1.
2.
2.
2.
9.
2.
5.
11
0.
0.
2.
34
5
1
9
0
9
0
9
5
2
4
8
3
5
90
69
1
tf~ = standard dev
Trout, N. CWC-60)
x e?- e
145
220
2.15
1.44
-
46.3
36.7
1.
1,
2,
3.
3.
4.
4.
5.
23
31
iation,
72
12
32
61
32
03
12
41
.5
.4
N-l
4.9
5.3
0.035
0.022
5.
1.
0.
0.
0.
0.
0.
0.
0.
0.
0.
o.
9
9
025
Oil
13
21
32
23
099
20
29
22
3.4
2.4
1.6
1.5
12
5
]
]
5
5
9
5
2
3
1
0
.8
o
. Z_
.5
. 0
.6
.8
.6
.7
.4
. 7
.2
.7
degrees
of freedom
x = mean
c
-------
72
20, 50 and 100 ugP/ml (KH PO,) and 20 ml of distilled water were added to
2 A
make the water to sediment ratio 100:1. The sample tubes were agitated
on a Burrell wrist-action shaker for 40 +_ 4 hours at ambient temperature
(28-29°C) centrifuged for 20 minutes at 2400 r.p.m. and filtered through
a 0.45 p. Millipore to remove final turbidity. A 0.1 N NaCl system was
used to facilitate particle setting during centrifugation. After the
supernatant was removed the tubes were reweighed to determine the amount
of P entrapped in the residue. The correction for P entrapped in the res-
idue was applied to the subsequent desorption step. The P desorption step
involved adding 40 ml of 0.1 N NaCl, shaking the solution for 40 hours,
centrifuging and filtering as described previously. A control sample was
run to determine the P released from the sediment to which no P was added.
Phosphorus was determined by the VM yellow or the molybdate blue method
depending on the concentration of P added to the sediment and the adsorp-
tion or desorption capacity of the sediment. The pH of the centrifuged
solution was determined by a combination electrode after the adsorption
and desorption steps. Duplicate runs were made on each sediment.
D. Statistical Evaluation of Analysis
The results presented in Appendix I for the chemical analyses of
each core are mean values of two or five replicate determinations. A
standard deviation was calculated for each of the 5 replicate determin-
ations and presented in Appendix I with the chemical data. The standard
deviation, mean and relative standard error for the measured parameters
of a typical calcareous and noncalcareous lake are shown in Table 3.6 for
Lake Wingra and North Trout Lake, respectively. The relative standard
-------
73
error was less than 5 and 10 percent for 66 and 25 percent of the
analyses, respectively. The relative standard error for exchangeable
ammonium ranged from 6.7 to 20 percent. A precision and accuracy deter*
mination on a Florida phosphate rock obtained from the National Bureau
of Standards of the U.S. Department of Commerce was presented by
Bortleson (1968).
Duplicate pollen counts were made from each processed sample. In
the transition zone (high to low ragweed) triplicate counts were made.
Ten replicate counts were conducted on Lake Monona (WC-101) and Devils
Lake core section number 13 and 1, respectively. The mean ragweed
pollen counts and standard deviation were 39 +_ 5 and 43 +_ 7 for Lake
Monona and Devils Lake, respectively.
The results presented for the leaching of P and N and sorption
desorption of P studies represent the mean value for duplicate deter-
minations .
-------
74
IV. EXPERIMENTAL RESULTS
The experimental results from this investigation may be separated in-
to the following phases: 1) identification of the pre- and postcultural
deposits in the sedimentary column using Ambrosia (ragweed) pollen as an
indicator, 2) determination of the chemical stratigraphy of hard-water
lakes, Mendota, Monona and Wingra in southern Wisconsin, 3) determination
of the chemical stratigraphy of soft-water lakes, Little St. Germain,
Trout, Minocqua, Little John and Weber in northern Wisconsin and Devils
in southern Wisconsin, 4) estimation of recent sedimentation rates using
the sedimentary depth of Ambrosia pollen and historical records of the
Wisconsin settlement era, 5) determination of sedimentation intensity of
chemical components in the postcultural sediment using estimates on sedi-
mentation rates and dry solids content in core profiles, 6) determination
of leaching potential of inorganic N and P from Lake Mendota pre- and post-
cultural sediment and 7) determination of the sorptive-desorptive capacity
of P on selected sediment levels of pre- and postcultural sediments.
The results of the core analyses are presented in Appendix I. The tab-
ulated data are mean values of two or five replicate determinations for
each core interval. A standard deviation is calculated for each of the
5 replicate determinations.
A. Identification of Pre- and Postcultural
Sediments Using Ambrosia Pollen
Cores were taken from the upper 50-100 cm of sediment for most of
the lakes examined; this depth of accumulation was sufficient to include
deposits representing the presettlement period in Wisconsin. In order to
identify pre- and postcultural periods of deposition in the core column,
-------
75
Ambrosia (ragweed) pollen counts were performed, and the results were
interpreted with respect to historically known changes in vegetation,
including early settlement, lumbering and farming.
Ragweed occurs in relatively high percentages (5-40%) in surface
sediment samples from the deciduous forest region of the northeastern
and northcentral U.S.A.; the plant seems to have increased as a result
of disturbance and creation of open habitats through forest clearance
by European settlers (Ogden 1967; Davis, 1967; Wright, 1968). A short
core (50 cm) was taken from Frains Lake in Michigan by Davis (1968).
From its pollen content, sediment deposited at the time of land settle-
ment and forest clearance was identified. The change in vegetative
cover resulted in a sharp decline in tree pollen, especially oak, and
a sudden relative increase in pollen from weedy herbs. Ragweed pollen
was especially affected, increasing from less than 1 percent to about
30 percent of the total. Many profiles of small lake and bog sediments
in or near the Great Lakes drainage basin show a similar sharp in-
crease in the relative abundance of Ambrosia pollen near the tops of
cores (Ogden, 1966).
In Table 4.1 and 4.2 are shown the ragweed pollen counts with depth
of sediment for the noncalcareous and calcareous lakes, respectively.
The base of the cultural horizon in the cores is indicated by the
appearance and rapid build up to relatively high levels of Ambrosia
ragweed pollen. The appearance of these pollen grains provides a
stratigraphic horizon which can be dated from historical records show-
ing when man moved into the region and began modifying the ecology. A
later discussion will detail the use of Ambrosia pollen for estimating
-------
Table 4.1 Ambrosia Pollen with Sediment Depth for Noncalcareous Wisconsin Lakes.
Depth of Trout,
Sediment N.
( cm)
0-5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
80-85
85-90
Water depth(m)
Mean ragweed
for postcul-
tural period
Mean ragweed
for precul-
tural period
Trout, Minocqua, Minocqua, Little St.
S. N.W. S.W. Germain, W.
Little St. Little
Germain, S. John
Sparkling Weber
Devils
Ragweed Pollen/100 Eucalyptus Pollen (Eu)
59
36
52
63
33
36 *
18
15
4
9
14
n. d .
8
n. d .
5
n,d .
14
26
46
11
29
27
28
43
38
31
22
17*
3
2
n.d .
1
1
n.d.
0
n.d.
0
33.2
29
1
44
29
28*
15
14
11
13
14
20
16
10.7
34
15
37
42
27
24
20
16*
7
4
5
3
6
4
4
13.7
28
5
39
38
34
29
29
26
26
27*
11
6
6
n.d .
3
n.d.
9
n.d .
6
5
15.6
31
7
32
32
32
32
40
34
39
32
18*
10
8
12
12
8
2
2
1
7
32
7
36
36
41
56
46
50
45
42
21*
9
8
11
9
10
n.d .
13
n.d.
10
5
42
10
63
66
45*
20
17
20
22
14
16
9
10
13
15
19
12
4
5
16
18.8
60
14
74
67
37
34*
21
22
19
20
17
21
12
17
18
15
21
19
22
17
12.6
53
19
46
43
34*
19
13
10
17
14
19
7
9
16
15
10
6
12
6
9
13.1
41
12
* Horizon showing rise in ragweed pollen
No determination = n.d.
-------
Table 4.2 Ambrosia Pollen with Sediment Depth for Calcareous Southern Wisconsin Lakes
Depth of
Sediment
( cm)
0-5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
80-85
85-90
90-95
Water depth
Mean ragweed
postcultural
Mean ragweed
precu Rural
Wingra
Mo no n a
WC-101
Monona
WC -46
Mend ota
WC-89
Ragweed Pollen/ 100 Eucalv
30
22
23
28
28
20
19
20
25
21
30
17
20
14*
2
2
5
6
-
(m) 3
for 23
period
for 4
period
38
42
34
31
33
21
26
28
23
25
23
25
39
34
21
22
14
18
15
21
--
--
38
27
31
23
27
28
27
25
28
17
13 *
4
2
n.d.
5
n.d.
3
3
2
15.9
26
3
28
42
30
32
33
26
24
14*
3
4
2
4
n.d.
2
2
5
n.d.
n.d.
n.d.
23.2
29
3
Mendota
WC-86
ptus Pollen (Eu)
56
55
58
47
36
34
41
26
18*
14
4
4
n.d.
0
n.d.
7
n.d.
5
n.d.
18.3
42
7
Mendota
WC-84
24
28
30
31
31
28
33
28
39
21*
14
10
7
3
7
7
8
4
4
11.8
29
7
Mendota
WC-82
4
3
2
1
4
n.d.
0
0
0
1
0
n.d.
2
n.d.
2
n.d.
1
n.d.
1
3.8
--
--
* Horizon showing rise in ragweed pollen
No determination = n.d.
-------
78
the postcultural sedimentation rate. The horizon showing a marked in-
crease in ragweed abundance varies considerably between lakes. The
profileo of South Bay of Little St. Germain and Little John show a
rapid increase in ragweed at a depth of 40-45 cm. On the other hand,
the marked increase in ragweed abundance is found at the 10-15 cm level,
i
in the northwest bay of Minocqua, Sparkling and Devils lakes. The
change from low to high ragweed counts is deeper in the column for cal-
careous than noncalcareous lakes. The thickness of the unconsolidated
sediments produced during the postcultural interval may vary depending
on the rate of sediment accumulation, the moisture content, core com-
paction or grain size of the sediments. For instance, in the noncal-
careous lakes the sediments are less consolidated and have a higher
moisture content than the calcareous sediment. Thus, the thickness of
the postcultural wet sediment column in the noncalcareous lakes is
often about the same thickness as the calcareous lakes even though the
latter sediments are accumulating much faster based on dry solids con-
tent. In all lake cores examined, a low count of ragweed appears in
precultural sediments, and the increase in ragweed pollen in the upper
part of the cores changes rather abruptly, usually over a 5 cm interval.
The mean ragweed count for the postcultural sediment is about 4-6 times
greater in the postcultural than the precultural sediment for most lakes
investigated. If the surface sediments were mixed appreciably, then
such comparisons would be invalidated. However, it must be concluded
that the fairly abrupt profile changes in ragweed pollen suggest the
depth of mixing does not appreciably influence the stratigraphy of the
deposit. Where the transition zone from low to high ragweed counts
-------
79
is more gradual, the estimate on the horizon separating the pre- and
postcultural sediment is less accurate.
-------
80
B. Chemical Stratigraphy of Calcareous
lakes in Southern Wisconsin
Lake Mendota
Surface Sediments. Surface sediments from 32 stations were col-
lected by Ekman dredge from Lake Mendota by Delfino (1968) and were
analyzed for P, Fe, Mn, Mg, K, Na and Ca (Delfino, Bortleson and Lee,
1969). The purpose of this sampling was to assess the chemical compo-
sition of the sediments with respect to water depth and location with-
in the lake. As an aid in the interpretation of the analytical data,
statistical analyses were applied which compared the elemental concen-
tration (mg/g dry weight basis) with depth of sample recovery. The
elemental analysis of Lake Mendota surface sediment and the statistical
correlation data are shown in Table 4.3 and 4.4, respectively.
Manganese, Fe and P show a positive statistical correlation be-
tween concentration and sample depth. For example, the highest concen-
tration of total P is 1.8 mg/g from the deepest part of Lake Mendota
and the concentration of P decreases by about one-half of the above
amount in the shallower areas in the lake. A significant inverse cor-
relation is found for Mg and K. Statistical correlation does not neces-
sarily imply causation so that water depth and morphology need not be
the primary controlling factors bearing on elemental concentrations in
the sediments. Other unmeasured or unidentified variables could be in
operation and these might just as easily be responsible factors for the
findings reported (Delfino et al., 1969).
The occurrence of fine particle settling could explain the corre-
lations found in this work. Since higher concentrations of Mn, Fe, and
-------
Table 4.3 Lake Mendota Surface Sediment Data [After Delfino, Bortleson and Lee (1969)].
Sample
number"
1
1
1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
Depth of
recovery,
meters
22
22
22
22
19
15
12
9
18
9
17
22
15
9
10
23
10
12
21
21
19
23
23
22
21
20
21
18
18
18
23
18
19
23
24
Date of
recovery.
1967
June 12
June 19
June 21
June 22
June 12
June 12
June 14
June 14
June 14
June 15
June 15
June 19
June 19
June 19
June 19
June 21
June 21
June 21
June 21
June 22
June 22
June 26
June 28
June 28
July 5
July 5
July 5
July 6
July 6
July 6
July 12
July 12
July 12
Oct. 11
Nov. 6
Manganese
1.34
1.33
1.32
1.32
1.19
0.90
1.22
0.76
1.19
0.64
1.22
1.26
1.11
0.76
0.90
1.40
1.04
1.11
1.12
1.34
1.17
1.30
1.34
1.20
1.18
1.34
1.04
1.14
1.15
.15
.32
.00
.00
.43
.50
Total iron
22.4
22.8
22.8
23.6
21.2
19.1
23.0
20.8
24.2
21.2
21.4
24.4
22.3
20.8
16.0
25.6
19.5
20.8
24.8
25.2
24.4
23.4
23.4
23.2
25.0
25.0
24.8
21.2
21.4
22.3
24.0
21.2
23.0
22.8
26.7
Total
phosphorus
1.35
1.35
1.38
1.38
1.29
0.85
1.30
0.92
1.45
0,89
1.29
1.45
1.01
0.89
0.84
1.35
1.17
1.02
1.42
1.38
1.42
1.47
1.53
3.37
1.62
1.52
1.22
1.20
.25
.26
.50
.09
.15
.41
1.82
vrg./G."
Total
magnesium
12.5
13.2
13.5
13.4
17.0
17.8
14.9
15.3
13.2
15.7
14.0
11.6
15.9
16.4
26.0
13.0
15.2
12.7
12.3
11.8
12.8
13.0
16.0
12.1
11.1
12.6
10.9
13.7
12.9
11.4
14.6
11.8
13.0
12.2
Total
potassium
12.5
12.5
12.7
12.5
13.0
12.5
15.0
14.3
13.0
14.7
12.0
12.3
10.5
12.3
26.0
12.5
11.5
12.2
12.2
12.2
13.5
12.2
12.0
12.0
13.1
13.8
12.3
11.8
12.5
12.3
12.3
12.0
11.8
12.2
Total
sodium
14.2
14.6
14.9
14.7
15.5
15.6
16.5
16.7
15.1
16.4
14.8
15.0
16.4
16.6
13.6
14.6
14.6
14.4
14.3
15.1
14.7
18.4
14.2
15.0
15.2
15.1
16.4
16.8
15.5
15.8
15.0
15.0
Total
calcium
108
111
111
111
112
114
114
100
105
80
114
112
108
125
80
103
117
90
97
90
89
99
100
98
78
88
97
113
120
109
109
106
124
112
CO
» Samples 1-30 were collected during summer thermal stratification. Samples 31 and 32 were collected during the fall circulation period.
' Oven-dry weight (105° C.) basis.
-------
Table 4.4 Statistical Correlation Data for Relationship between Depth of
Sample Recovery and Element Concentration in Lake Mendota.
Element
Manganese
Iron
Phosphorus
Magnesium
Potassium
Sodium
Calcium
a
r
0.81
0.74
0.82
-0.59
-0.40
-0.15
0.04
b
P
0.001
0.001
0.001
0.025
0.025
e
e
c d
s n
0.13 30
0.98 30
0.22 30
2.29 29
2.34 29
f 27
f 29
Q
Linear correlation coefficient
Significance level of correlation
r*
Standard error of estimate
Degrees of freedom, n = N - 2
rt
Not significant
f M
Not computed
-------
83
P are found at deeper depths in Lake Mendota and since these deeper
depths are essentially in the middle or central part of the lake, a
relatively simple particle fractionation of tributary-borne suspended
matter may have occurred. Particle size analyses of the sediment sam-
ples were not conducted so that conclusive evidence is lacking. However,
four cores taken from Lake Mendota in progressively deeper water show
a percent solids decrease with increasing depth as shown in Figure 4.1.
This would indicate that there is a natural grading process occurring
in the lake during which finer solids are settling in the deeper zones.
Delfino and Lee (1968) reported that essentially all of the Mn in Lake
Mendota waters is soluble and passed through either 0.45, 0.22 or 0.10 p
pore size membrane filters. Thus, any residual suspended particulate
Mn would have to be on the order of less than 0.10 p in diameter. This
fact would require the suspended material and its associated elements
to be present in a very small colloidal form.
This interpretation is supported by studies of annual pollen de-
position per unit area measured in sediment traps at Frains Lake in
Michigan by Davis (1968). At Frains the ratio of deposition, as mea-
sured in traps, to net accumulation, as measured in sediment cores,
showed the pollen grains were deposited an average of two to four times
before being buried deeply enough to escape further disturbance. Davis
(1968) explained that the sediments in shallow water were apparently
stirred up and resuspended more frequently or more extensively than
sediment in deep water; the net result of repeated resuspension mainly
from shallow water sediment, followed by redeposition over the entire
basis, was movement of material from shallow to deep water. Nichols
-------
84
E
u
0)
o
03
14-1
(-1
0)
c
o
E
H
o
0)
co
0)
CQ
Q
0
10
20
30
40
50
60
70
80
90
100 -
0 Deep Area 23.2 m
A Univ. Bay 18.3 m
Q Univ. Bay 11.2 m
O Univ. Bay 3.8 m
10 20 30 40 50
Percent Solids
60
70
Figure 4.1 Percent Solids (Dry Weight) with Depth of Sediment in
Lake Mendota Cores.
-------
85
et al. (1946) noted that copper sulfate applied to the bay areas of
Lake Monona (1925-1944) was recovered in highest concentrations in the
deep portions of the lake. It seems that the natural grading process
carried the precipitated Cu compounds to the deeper waters. Frink
(1967) collected bottom samples from Bantam Lake, Conn., and found that
total P and N increased with water depth. The sediments in the deeper
water of Bantam Lake contained more P and an increasing proportion of
this P was readily exchangeable (Frink, 1967).
Reproducibi lity of Phosphorus Stratigraphy. If it is assumed that
cores taken from the deep area of Lake Mendota are more nearly represent-
ative of the depositional processes occurring over the entire basin,
it then becomes important to know the reproducibility of the distribu-
tion patterns for cores within the central area of the lake. Four
cores, approximately 75 cm long, were taken in 21.2 m of water in the
deep area of Lake Mendota over the ice 12-15 feet apart on the same day
in February, 1969. Phosphorus was chosen as the element to use to study
the variations in the core column because of the accuracy, precision
and other analytical attributes of the vanadomolybdate method for P
(Wentz and Lee, 1969a; Jackson; 1958).
The phosphorus profiles for replicate Lake Mendota cores IR-IVR
are shown in Figure 4.2 and 4.3 for 5 cm (2), 2 cm and 8 cm intervals.
The results indicate the basic P profile is reproduced for each core
taken at the same site, and the P profile compares well with the deep-
water core, WC-89 (not shown) taken in 1966. The concentrations of P
for the replicate cores are nearly the same, and maximum P concentra-
tions are at the surface level and at a level below the surface sediment.
-------
s
u
O)
u
(U
iJ
c
J-l
C
O)
6
TD
0)
'0)
pa
a,
0)
a
10
20
30
40
50
60
70
80
90
Core IR
Core IIR
I
0.4 0.8 1.2 1.6
Phosphorus (mg/g)
2.0 0 0.4 0.8 1.2 1.6 2.0
Phosphorus (mg/g)
10
20
30
40
50
60
70
80
90
Figure' 4.2 Phosphorus Stratigraphy of Deep-Water Lake Mendota Cores Fractionated
into 5 cm Intervals.
00
-------
0)
o
-------
88
Too much reliability cannot be placed on the exact level of a fluctua-
ting pattern in a core, since the maximum P shifts from the 10-15 cm
stratum to the 15-20 cm stratum. These changes may be due in part to
the imprecise nature of fractionating the core and to real differences
that may exist in the layers of sediment in the lake bottom. Replicate
cores taken may be compacted or expanded differently when the core is
cut and when the core is extruded. Errors may also exist in obtaining
the interval sizes fractionated at the same point in replicate core
columns.
As shown in Figure 4.2, the profiles for cores IR and IIR which
were fractionated into 5 cm intervals exhibit a slight difference in the
position of the maximum peak. In core I11R, which was fractionated into
2 cm intervals, the two maximum peaks become more pronounced as shown in
Figure 4.3. Undoubtedly, core IIIR taken in 2 cm intervals could be in-
terpreted with greater confidence than the other cores. As shown in
Figure 4.3, the P profile of core IVR fractionated into 8 cm intervals
shows a further smoothing out of the slight variations found in the
other cores, as might be expected with larger size intervals. However,
the two maximum peaks are still retained in core IVR. It would appear
that the general interpretation of the P distribution with depth would
be the same for cores fractionated into 5 cm or 8 cm intervals. How-
ever, the interpretation of core IIIR may be slightly different because
the variations are more pronounced, indicating that a more dramatic in-
crease of P deposition occurred over a short interval (28-22 cm), where-
as the P profiles of the other cores indicate a steady increase of P
deposition over a longer interval (35-15 cm). Greater resolution in
-------
89
following chemical sedimentary changes for Lake Mendota is achieved by
fractionating into less than 5 cm intervals. If mixing were deeper
than only the upper layers (ca. 2-5 cm) in Lake Mendota deep-water sedi-
ments, greater resolution would not be observed by taking 2 cm inter-
vals. To achieve the resolution obtained in the 2 cm interval fraction
would have involved considerably more analytical work. In this sense,
mixing may be advantageous because the resultant integration of old and
recent particles make less necessary any effort to analyze more closely
spaced intervals. The 5 cm interval size probably represents a compro-
mise on the amount of additional analytical work needed and the amount
of resolving detail achieved. Nevertheless, the gradual or abrupt ob-
servations in the percentage diagrams are also dependent on the interval
size used.
This type of study is of particular importance in light of evidence
for the mixing of sediments by burrowing organisms (Ogden, 1967; Davis,
1967) and by density currents (Bryson and Suomi, 1952). Since two max-
imum peaks and practically the same trends of P deposition are observed
in all cores, including core WC-89 taken in 1966, it appears from this
study that the solid phase component of sediment in the top layers is
not a fluid mass subject to vertical displacement over a short period
of time in the deep-water sediments of Lake Mendota. Over a long period.
changes may take place in the concentration of P in the upper layers be-
cause the depth of vertical mixing or the depth at which a sediment par-
ticle is incorporated into the motionless historical layer is not known.
Undoubtedly, vertical mixing of sediments by benthonic animals or
mechanical agents near the sediment-water interface is occurring, but
-------
90
the extent of mixing does not appear to laterally or vertically change
the overall distribution pattern of P in the deep-water area of Lake
Mendota.
Deep-Water Profile WC-89. (Note on the digestion procedures used:
It should be borne in mind by the reader that the digestion of the sed-
iment samples for Mendota core WC-89, Monona core WC-46 and Trout core
WC-59 was done without the preliminary HF treatment; therefore, the
concentrations of Al, Mg and K will be a fraction of the total. However
there is no detectable difference analytically in the sedimentary con-
centrations of Fe, P, Mn and Ca using either HF-HC10 -HNO or HC10,-
HNO digestion procedures (Bortleson, (1968) ). The chemical strati-
graphy of Lake Mendota core WC-89, obtained in 23.2 m of water, is
given in Figure 4.4. The upper 55 cm of sediment consists of a finely
divided, homogeneous, black mud, or gyttja, followed by a 15 cm tran-
sition zone to a buff-colored marl, which is dominant in the lower 25-
30 cm. Murray (1956) maintained the black color in the gyttja results
from the presence of ferrous sulfides deposited under conditions of
oxygen deficiency and not from the organic content. Berner (1964)
found that recent sediments containing fine-grained black FeS, even in
small concentrations, tend to be colored gray and black. Upon addition
of HC1 or on standing, the sediments show a noticeable color change as
the black material decomposes. The black gyttja contains 25-31 percent
CaCO , and the marl contains 47-50 percent CaCO . The rise in ragweed
pollen at the 35-40 cm interval separates the pre-and postcultural sed-
iment. The ragweed horizon is 25 cm above the gyttja-marl boundary,
thus it appears the black gyttja was deposited in the center of the
-------
(1.2 0.4 0.6 O.H 1.0 1.2 1.4 1.6 1.
P (mg/g)
Figure 4.4 Chemical Stratigraphy of Lake Mendota Profile WC-89 [Acid Soluble P Data After Wentz
and Lee (1969b) and Mn Data After Delfino (1968)].
-------
92
lake prior to the major disturbance by man in the Lake Mendota water-
shed. A radiocarbon age of the organic material at the 90-95 cm inter-
val dates less than 200 years before present (B.P.) according to Bender
(1969). However, considerable error may exist for radiocarbon dating of
recent sediments (Ogden, 1967). In all the calcareous lake cores, the
gyttja, the transition zone between the sediment types as well as the
marl are estiablished by the Ca profile or the COl-C values.
Organic C and organic N concentrations fluctuate with depth of sed-
iment; however, the mean concentration of organic C and organic N above
and below the ragweed horizon is approximately the same. Murray (1956)
also noted that the organic content was essentially the same in the
gyttja and marl layers. Concentrations of organic C and organic N
throughout the core are 54-90 mg/g and 6-10 mg/g, respectively. Maxi-
mum concentrations of organic C are observed in both pre- and post-
cultural sediment.
Exchangeable ammonium N (NH,-N) concentrations are higher in the
upper postcultural sediment ranging from 0.41-0.55 mg/g, whereas in
the precultural sediment the concentration is 0.34-0.41 mg/g.
The total P concentration remains constant at approximately 0.8-
0.9 mg/g within the marl and through the marl-gyttja transition zone
(70-60 cm). A gradual increase occurs thereafter (60-25 cm), yielding
a range of 1.0-2.0 mg P/g. The maximum peak at the 25-30 cm interval
is followed by a decline and rise in P content in the upper 30 cm of
sediment. Acid soluble P concentration, as determined and reported by
Wentz and Lee (1969 a,b), follows a trend similar to total P. The P
released with 0.075 N HC1-H SO extractant is an operationally defined
2 4
-------
93
o
fraction of the total which is desorbed at 20 C at pH ]-2 (Wentz and
Lee, 1969a). Presumably, the acid extractant would remove Ca-bound
forms of P plus an undefined fraction of Fe-P and Al-P. Acid soluble
P concentrations are 0.61-0.73 mg/g and 0.72-0.96 mg/g in pre- and
postcultural sediment, respectively (Wentz and Lee, 1969b). The ratio
of acid soluble P to total P decreases above the 55-60 cm level indi-
cating that the more recent sediment contains a greater fraction of P
which is not acid extractable.
Iron, Mn and K increase from a constant background concentration
of 7-8 mg/g, 0.4-0.5 mg/g and 2-3 mg/g, respectively, in the marl and
gyttja-marl boundary to 2-4 times these concentrations in the post-
cultural sediments. The initial rise in Fe, Mn and K concentrations
at 65-70 cm begins before the appearance of ragweed pollen. The sedi-
ment at the 65-70 cm level is estimated to be 165-200 years B.P. based
on the rise in ragweed at 100 years B.P. The Fe profile is similar
to the distribution pattern for total and acid-soluble Fe found by
Nriagu (1967-68) for a Lake Mendota deep-water core. Most of the Fe
was soluble in boiling IN HC1. Nriagu (1967-68) explained that the
fraction of acid-soluble Fe which was not tied up as a Fe sulfide was
coprecipitated with calcite.
The Mg profile presents no increasing or decreasing trend with
depth of sediment.
University Bay Profiles WC-82, -84 and -86. It is not known
whether substantial differences can be observed in the horizontal stra-
tification Lake Mendota sediments. The changes in chemical stratigraphy
below the sediment-water interface for three cores taken along a transect
-------
94
from the shallow area of University Bay towards the center of the lake
are shown in Figure 4.5, 4.6 and 4.7. Profiles WC-82, -84 and -86 were
taken in progressively deeper water of 3.8, 11.6 and 18.3 m, respec-
tively ,
The horizon showing a marked increase in ragweed pollen is progres-
sively deeper into the sediments for profiles WC-89, -86 and -84, re-
spectively. However, an increase from low to high ragweed counts is
not observed for the shallow-water core WC-82. Apparently, the pollen
is resuspended in the shallow-water areas and transported to deeper
water before final deposition. Since the ragweed pollen rise from low
to high counts occurs at greater sediment depth for WC-84 and WC-86 than
the deep-water core WC-89, a faster sedimentation rate or a greater
mixing depth is implied. For profile WC-84 and WC-86, the ragweed hor-
izon coincides with the top of the gyttja-marl transition zone as shown
by the Ca profiles. In core WC-82 the transition from low to high
CaCO content occurs at the 10-15 cm level. The short column of gyttja
indicates the nearness of core WC-82 to shoreline deposits where the
normal physiochemical conditions at this location may be greatly modi-
fied by vegetation, greater frequency of wind generated currents and
other shoreline phenomena. A one meter segment of sediment probably
represents a much greater time span than the other cores obtained from
University Bay.
There are similarities as well as differences in the organic C
distribution patterns of the University Bay cores and the deep-water
core. Profiles WC-84 and WC-89 show considerable similarities in the
distribution of organic C although the concentration of organic C in
-------
' ' J.I t I I
I I 1 ' i
i i 1 1 i i i i i i
1 ' ' '
55 63 75 »5
Orgonic C (mg/g|
0.2 0.4 0.6 0.8 1.0 1.2 l.i l.l,
P (nif./K)
12 15
Fe <
18 21 2U
' 10 20 30 ill 5(1
Pa^weed (cnuntB/100 fcu)
0.7
Mn (
345 6 7 8 9 10 11 12
Figure 4.5 Chemical Stratigraphy of Lake Mendota Profile WC-86, University Bay.
-------
5 10 15 20 25 30 35 40
Al (mg/g)
Figure 4.6 Chemical Stratigraphy of Lake Mendota Profile WC-84, University Bay.
-------
Figure 4.7 Chemical Stratigraphy of Lake Mendota Profile WC-82, University Bay.
-------
98
WC-84 is higher than WC-89 throughout the core. In both profiles, WC-
89 and WC-84, the mean concentration of the pre- and postcultural sed-
iment changes only slightly; however, in cores WC-86 and WC-82 the
organic C concentration is higher in the postcultural sediment.
The distribution of P increases upward in all the University Bay
cores examined with the highest concentration in the postcultural sedi-
ment. The change in mean concentration of P in pre- and postcultural
sediment is shown in Table 4.5 for each of the University Bay cores and
Table 4.5 The Mean Concentration of Phosphorus in Pre- and Postcul-
tural Lake Mendota Sediment.
Core
WC-89
WC-86
WC-84
WC-82 *
Water Depth
(m)
23.2
18.6
11.2
3.8
Mean Concentration
of Postcultural
Sediment (P )
a
1.68
1.26
1.12
0.787
Mean Concentration
of Precultural
Sediment (P, )
b
0.986
0.980
0.924
0.468
Pa/Pb
1.70
1.29
1.22
1.67
* High and low CaCO_ content used to identify pre- and postcultural
sediment, respectively
the deep-water core. The mean P concentration for the precultural marl
is about the same in cores WC-84, -86 and -89, but, for the same cores,
the P concentration increases more in the postcultural sediment the
deeper the water as shown by the mean P concentration of the post-
cultural sediment over the precultural sediment, P /P , in Table 4.5.
a b
The recent deposition of P in the center of the lake is probably
associated with the finer sediment fraction. Although the mean con-
centration of P in the postcultural sediment for WC-82 follows the trend
of increasing concentration with increasing water depth, the P /P ratio
a. b
-------
99
for the 3.8 m University Bay shallow-water core is about the same as
the deep-water core. The P /P ratio is high for core WC-82 because
a b
the concentration of P in the precul jral sediment is low.
In core WC-86 the acid soluble P extracted with 1 N HC1-H SO is
2 4
practically constant with depth of sediment, and the mean acid soluble
i
P fraction is 47 and 58 percent of the total P in the post- and precul-
tural sediments, respectively. In both cores, VC-86 and WC-89, a
greater proportion of P is not acid extractable in the postcultural sed-
iment. This fraction of P would probably be refractory P which is not
readily exchangeable.
There is considerable parallelism in the trends for Fe, Mn, Al
and K concentrations for WC-86 and WC-84. The sediments above the
gyttja-marl transition zone contain about 3-4 times more Fe, Al and K
and 2 times more Mn than the precultural sediment. Magnesium is nearly
constant with depth for both WC-84 and WC-86, but the concentration
profiles are somewhat irregular within a narrow range of 12-16 mg/g for
WC-86 and 15-17.5 mg/g for WC-84.
In core WC-82, the Fe, Mn, K ana Al concentrations are nearly con-
stant for the length of the core below the 10-15 cm level, but an upward
enrichment of these elements occurs above the 10-15 cm level. The Ca
profile forms a peculiar shape in WC-82. Minimum concentrations of Ca
are found at the bottom and top of the core, and maximum concentrations
of Ca are observed at the 30-45 cm strata.
In summary, although most of the chemical components show similar
trends for the cores taken in line from University Bay towards the cen-
ter of the lake, there are differences in order of magnitude of the
-------
100
concentrations as might be expected from the surface sediment correla-
tion data. Profile WC-82, taken in 3.8 m of water in University Bay,
shows the greatest departure from the other cores in chemical strati-
graphy. The individual trends for Fe, Mn, P, Mg and Ca in cores WC-84,
-86 and -89 are generally alike disregarding differences in sediment
depth of the postcultural sediment. Organic C reveals some similar
and dissimilar trends in stratigraphy between cores WC-84, -86 and -89.
The changes in order of magnitude of Fe, P and Mn concentrations with
water depth of core recovery agree with the surface sample correlation
data for the postcultural sediment. However, the concentrations of Fe,
P and Mn are rather uniform in the precultural sediment independent of
water depth, thus it appears historically the chemical composition of
Lake Mendota sediments was more uniform over a greater area in the lake
bottom than the recent postcultural sediments.
Long Core WC-95. The chemical stratigraphy of WC-95, a 990 cm
core obtained in 24 m of water, is shown in Figure 4.8. The 9.9 m core
was fractionated in 20 cm intervals and analyzed for various chemical
components at 20 selected intervals. The top 62 cm of sediment consists
of a black gyttja containing 22-28 percent CaCO ; below 62 cm to 990 cm,
the fine-grained, buff-colored marl deposits contain 46 to 57 percent
CaCO . There was no variation in appearance from 62 cm to 990 cm of
sediment. The depth of the postglacial marl deposits is unknown. The
core is exceptionally uniform in water content with depth of sediment
(see Appendix I data). Below 102 cm in the core the solids content
ranges from 15.6 to 20.8 percent throughout the core, thus the original
thickness of the recent sediment does not change dramatically with depth
-------
Figure 4.8 Chemical Stratigraphy of Lake Mendota Profile WC-95.
-------
102
of burial because of compaction.
The marked increase in ragweed abundance occurs upward of the
42-62 cm stratum. The low ragweed pollen deposited during the period
represented by 920 cm of sediment below the recent muds supports the use
of Ambrosia pollen as an indicator of the cultural base in a sedimentary
sequence. A ragweed maximum in pollen diagrams may not necessarily be
related to European-type settlement. At Silver Lake, Ohio and at Rogers
Lake, Conn., high ragweed pollen counts were found in core intervals
dated 5000-8000 years B.P. (Ogden, 1966; Davis, 1967).
Organic C concentration varies from 59 to 77 mg/g over the core in-
terval of 62-900 cm. This compares favorably with 55-73 mg organic C/g
found in the marl sediment of WC-89, a short deep-water core. The post-
cultural sediment contains 87-92 mg/g organic C.
Phosphorus concentration remains constant at 0.8-0.94 mg/g below
the ragweed horizon for a long period historically, then the P concen-
tration increases to 1.5-2.1 mg/g in the postcultural sediment.
The depth plot of Fe, Mn, K and Al concentrations is remarkedly
uniform below the ragweed horizon to 990 cm, but the postcultural con-
centrations of these elements increases 3-5 times that found in the pre-
cultural sediment. For all the above elemental concentrations a slight
minimum inflection is observed in the zone of 400-650 cm.
In summary, the chemical stratigraphy of the 9.9 m core indicates
that stable conditions existed in Lake Mendota and its watershed for a
long historical period before the settlement period in Wisconsin.
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103
Lake Monona
Deep-water Profile WC-101. The chemical stratigraphy of Lake Monona
WC-101, obtained in 21 m of water, is given in Figure 4.9. The entire
i m core is a black, homogeneous gyttja containing 22-30 percent CaCO .
Sanchez (1970) found high and low concentrations of Cu above and below
the 75-80 cm level, respectively. Copper sulfate was first applied to
Lake Monona to control algae growth in 1918 (Nichols et al., 1946).
Starting in 1925 and continuing for 29 years through 1953, copper sul-
fate was applied systematically to Lake Monona (Stewart and Rohlich,
1967). The depth of the Cu horizon indicates the sedimentation rate for
profile WC-101 is very high. Evidence of a high sedimentation rate is
also suggested by the lack of a break in the ragweed curve throughout
the depth of 100 cm.
The phosphorus concentration remains nearly constant with depth and
ranges from 1.3 to 1.7 mg/g. The periods of discharge of sewage efflu-
ent to Lake Monona do not seem to be reflected in the sedimentary p con-
centration profile. In 1936 the treatment of sewage at the Madison
Burke Plant was discontinued and the discharge of sewage effluent to
Lake Monona was stopped. However, in 1942 the Burke Plant was reused
temporarily by the U.S. Army and by the Madison Metropolitan Sewerage
District. The effluent was discharged to Lake Monona again and con-
tinued to be so discharged until 1950 (Stewart and Rohlich, 1967).
Nothing is detected in the sediments that can be referred to these
periodic high sources of phosphorus. However, the urban runoff to the
Monona basin (Sawyer, 1944), as well as the agricultural runoff, may
serve to mask any periodic high sources of phosphorus.
-------
1 . . ' . ' '
T r
6789
1.75 2.25 2.75
Sulflde S (mg/g>
0.6 0.8
0.6 0.7 0.8 0.9
Mn (mg/g>
20 25
Al <
30 35
12 14 16 18
Mg (mg/g)
0.1 0.2 0.3 0.4 0,5 0.6
Cu
-------
105
Organic C concentration decreases downward through most of the
core length (15-70 cm), but there are fluctuations in the organic C pro-
file at the top and base of the core reversing the long downward trend.
Organic C decreases from 107 mg/g at 15-20 cm to 86 mg/g at 70-75 cm.
Exchangeable ammonium N decreases with depth of sediment from the
surface to the 25-30 cm level and remains nearly constant with depth
thereafter.
Only slight inflections with depth of sediment are observed for Ca
and Mg concentrations. The only departure in the constant Mg concen-
tration with sediment depth is the enrichment in the top 15 cm of sedi-
ment .
Mn and sulfide-S concentrations are also nearly constant with
depth of sediment throughout the core. Most of the sulfide sulfur is
probably held as a form of FeS. The Fe content of the recent sediment
is greater than that required to hold all sulfur present as FeS; the
molar ratio of sulfide sulfur to iron varies from 1:7 to 1:4.
Iron, K and Al concentrations are constant throughout the profile
except a slight decrease in concentration is observed at the 90-100 cm
level.
In general, the chemical composition of the deep-water core WC-101
is strikingly uniform with depth of sediment.
Profile WC-46. The chemical stratigraphy of Monona core WC-46,
obtained in 15.9 m of water, is given in Figure 4.10. The top 35 m of
sediment is a black gyttja, followed by a 20 cm transition zone to a
buff-colored marl, which is dominant from 60-95 cm. The gyttja and marl
layers contain 27-30 percent and 47-60 percent CaCO , respectively.
-------
6 8 10 12 14 16 18 20
Fe (mfl.'g)
0.3 0.6 0.9 1,2 1.5 1.8 2.1 2.4
Al
-------
107
Ragweed pollen increases upward at the 50-55 cm horizon which coincides
with the transition zone from high to low Ca content.
The P concentration of 0.7-1.9 mg/g generally increases upward
from the 80-85 cm level to the surface sediment; below 80 cm, P con-
centration remains constant. The initial increase in P concentration
at the 80-85 cm interval, 30 cm below the ragweed horizon, is followed
by another rise in P concentration at the 45-50 cm interval correspond-
ing closely to the ragweed horizon. The P concentration increases to
a maximum peak at the 30-35 cm interval (ca. 50 years B.P.) and remains
high thereafter to the sediment surface.
Iron and Mn concentration profiles are very similar to the P dis-
tribution pattern. Below 60 cm, iron and Mn increase from a background
concentration of 5.2-7.8 mg/g and 0.37-0.46 mg/g, respectively, to 2-3
times these concentrations in the postcultur'al sediments.
Above 60 cm coinciding with the initial rise in ragweed (50-55 cm) ,
the Al and K increase rapidly to maximum concentrations at the 30-35 cm
interval and remain high thereafter to the sediment surface. From a
low background concentration in the precultural sediment, Al and K con-
centrations increase 3-4 times and 4-5 times in the postcultural sedi-
ment, respectively.
Calcium concentration increases upward from 190 to 240 mg/g over
the interval 105-60 cm. From 60 cm to the surface sediment the Ca pro-
file forms a mirror image to the K, Al, P, Fe and Mn concentration pro-
files.
On the other hand, Mg concentration changes only slightly with
depth but increases in the top 15 cm of sediment.
-------
108
The reai Its indicate that P, Fe, Mn and Ca concentrations of cores
WC-101 and WC-46 are the same order of magnitude upward of 35 cm in each
core sequence. The apparent uniformity in the elemental concentration
with water depth is in agreement with Twenhofel's observation (1937).
He collected core, samples from Lake Monona along a transect from Turville
Point to Southwest of the Yahara River and found from a profile of the
traverse that the percentages of CaCO , insoluble residue and loss on
ignition were regular and uniform over the main part of the traverse,
but fluctuated greatly in the shallow water.
Lake Wingra
The chemical stratigraphy of Lake Wingra core WC-92 is shown in
Figure 4.11. The top 60 cm consists of a gray marl deposit of 56-62
percent CaCO ; below 60 cm the gray marl is 68-80 percent CaCO
and contains many gastropod shells and shell fragments. The sediments
appear coarse because of the shell fragments, but the matrix between
the shells is fine-grained. Juday (1914) noted the large marl deposits
both on the bottom of Lake Wingra and along its margins. In some places
these deposits reached a thickness of 8 to 9 m according to Juday
(1914) .
The marked increase in ragweed abundance occurs upward of the 65-70
cm horizon. The depth of the ragweed horizon indicates the sedimenta-
tion rate for Lake Wingra is high.
The organic C and organic N concentration profiles are closely re-
lated. Even though the organic C is somewhat irregular, each irregu-
larity is duplicated by the organic N depth plot. A minimum concentration
-------
Al (irg/g)
5 10 15 20 25 30 35
r
Figure 4.11 Chemical Stratigraphy of Lake Wingra Profile WC-92.
-------
110
of 55-70 mg/g organic C is found from 55 to 25 cm in the postcultural
sediment, and a maximum concentration of 72-92 mg/g organic C is found
from 90 to 65 cm in the precultural sediment. There is a rise in
organic C and organic N in t,he top 20 cm of sediment which is estimated
to contain material deposited 20-30 years ago based on the ragweed rise
at 100 years B.P.
Exchangeable ammonium N concentration increases with depth of
burial throughout the postcultural sedimentary sequence; in the pre-
cultural sediment the exchangeable ammonium N concentration remains
nearly constant at 0.20-0.23 mg/g which is approximately four times
greater than the lowest concentration found in the uppermost 25 cm of
sediment.
Total P concentration fluctuates slightly with depth of sediment
ranging from 0.45 to 0.64 mg/g. Minimum P concentration (0.45-0.51
mg/g) corresponds to the minimum organic C and organic N concentration
at the 55-25 cm interval. Upward of 25 cm (ca. 35-40 years B.P.) phos-
phorus concentration increases slightly. Acid soluble P extracted with
1 N HC1-H SO, varies from 0.27 to 0.39 mg/g throughout the core. The
2 4
highest concentration of acid soluble P is found in the precultural
sediment which contains the larger fraction of CaCO and organic C and
3
the smaller fraction of Fe, Al, Mn and Mg. The proportion of acid
soluble P to total P varies from 43-69 percent to 66-81 percent in the
postcultural and precultural sediment, respectively. In other words,
the postcultural sediment contains a greater proportion of P which is
not acid extractable. Presumably, the more recent muds contain more P
which is refractory or not readily exchangeable to the overlying water.
-------
Ill
As a first approximation, the fraction of P released with 1 N acid in-
cludes inorganic P (Ca-P plus Al-P and Fe-P), but 1 N acid probably
would not extract organic P or occluded forms of Fe-P and Al-P (Shah
et al., 1968).
The chemical stratigraphy of profile WC-92 changes considerably
at the 65-70 cm boundary horizon. The precultural deposits below the
65-70 cm stratum contain low concentrations of Fe, Mn, Al, K and Mg.
These elemental concentrations increase sharply upward from 65-70 cm
into the postcultural sediment and level off above 55 cm to the surface
sediment. Iron, Mn and Al concentrations increase 3-4 times in the
postcultural sediment compared to the precultural sediment.
Comparison of Pre- and Postcultural Sediments in Calcareous Lakes
The mean concentration of various chemical components of the pre-
and postcultural sediments of Mendota, Wingra and Monona are given in
Table 4.5. A comparison of the mean concentration of postcultural over
precultural sediment is presented as a ratio, K, in Table 4.6. If K
is plus or minus 10 percent of unity, the notation of zero is given for
little or no decrease or increase in the mean postcultural over pre-
cultural concentration. Likewise, arbitrary notation is given for K
denoting increases or decreases of 20 and 50 percent in postcultural
over precultural sedimentary concentrations.
There is considerable uniformity in the individual distribution
patterns of P, Fe, Mn, Al, K, Mg and Ca between the Lake Mendota cores.
The postcultural sediments are enriched in P, Fe, Mn, Al and K compared
to the precultural sediment which is enriched in Ca only. Magnesium
concentration remains about the same throughout the core. Organic C is
-------
Table 4.6 Mean Concentrations of Pre- and Postcultural Sedimentary Components for Calcareous Lakes.
Core
Lake Mendota
* WC-89
WC-86
WC-84
** WC-82
WC-95
Lake Monona
WC-101
* WC -46
Lake Wingra
WC-92
a
b
a
b
a
b
a
b
a
b
a
b
a
b
a
b
Org-C
73.5
71.4
74.3
61.1
98.7
94.6
73.4
51.9
89. 1
64.8
97.1
__
_ H
--
68.9
80.7
P
1.68
0.986
1.26
0.976
1.11.
0.919
0.787
0.468
1.85
0.854
1.63
--
1.57
0.976
0.545
0. 490
Fe
21.2
10.9
20. 1
8.29
19.9
9.07
11.9
5.03
19.2
6.59
16.5
--
16.8
6.83
7.72
2.17
Al
mp/p
lllo' o
--
--
45.9
21.1
38.3
15.7
30.8
14.6
37.1
9.45
32.5
--
1.83
0.63
29.0
8.57
K
10. 1
5.40
11.5
4.32
11.0
4.77
9.18
4.82
10.3
2.01
8.81
--
2.58
0.73
5.06
0.66
Mg
11.1
10.3
14.3
13.7
16.8
16.3
15.5
15.6
--
13.2
--
11.4
10.6
9.53
6.14
Ca
112
159
102
228
94.0
214
122
199
102
210
101
--
131
207
238
310
Mn
1.16
0.485
0.762
0.460
0.644
0.486
0.500
0.382
1.04
0.364
0.790
--
0.723
0.400
0.571
0.288
a Mean concentration of postcultural sediment
b Mean concentration of precultural sediment
* HC10,-HN03 digestion (w/o HF), except K determination for Lake Mendota core WC-89
** High and low CaCO content used to identify pre- and postcultural sediment
-------
113
the only chemical component which deviates from the consistent pattern
in the horizontal stratification of the deep-water and University Bay
cores. The K values for organic C in cores WC-89 and WC-84.are z^ero,
whereas the other three Lake Mendota cores exhibit an increase in
organic C concentration in the postcultural sediment. In general, the
deposition is rather uniform horizontally between the deep-water and
University Bay cores. The ragweed pollen data suggest different rates
of deposition in each of the Lake Mendota cores.
The mean Ca concentration increases in the Lake Mendota post-
cultural sediment with increasing water depth from core WC-84 to WC-89.
This observation is in agreement with a comparison of the geographic
distribution of CaCO content of the gyttja and marl made by Murray
3
( 1956). He found that the gyttja contained higher concentrations of
CaCO and the marl contained lower concentrations of CaCO as the depth
3 3
of the water increased. Furthermore, this study indicates Mg concen-
tration decreases with increasing water depth for both the pre- and
postcultural sediments. Thus, it appears that prior to the deposition
of black gyttja sedimentary Ca and Mg concentration behaved similarly
with respect to water depth but in the postcultural sediment Ca and Mg
concentrations are inversely related with respect to water depth of
core recovery.
The postcultural sediment of Monona core WC-46 is enriched in P,
Fe, Mn, K and Al compared to the precultural sediment which is enriched
in Ca only. Magnesium concentration remains relatively constant through-
out the core. Similar trends are observed for Mendota.
The positive K_ values (see Table 4.7) for the chemical stratigraphy
-------
114
Table 4.7 Comparison of Mean Concentration of Postcultural over Pre-
cultural Sedimentary Components in Calcareous Lakes.
Core
Org-C
Fe
Al
Mg
Ca
Mn
Mendota
WC-89
WC-86
WC-84
WC-82
WC-95
n.d. +++ 0
+++ +++ 0
+++ +++ 0
0
n.d.
Monona
WC-46
n.d. +++ +++
Wingra
WC-92
* v - mean concentration of postcultural sediment
~ mean concentration of precultural sediment
(see Table 4.6)
Notation:
= 0 1. 1< K;£ 1. 2 = +
1.2< K^ 1.5 = ++
K >1.5 = +++
K< 0.5 = ---
n.d. = no determination
-------
115
of Wingra are similar to Mendota and Monona except for organic C, P
and Mg. In the Wingra sediments organic C increases in the precultural
sediment, while P remains constant with sediment depth and Mg increases
in the postcultural over the precultural sediment.
The order of magnitude of the various chemical components in the
postcultural sediment is very similar for Mendota and Monona. The
lower concentrations of P, Fe, Mn, Mg and Al in Wingra sediments may be
partially attributed to the high carbonate-containing sediment diluting
the above fractions. Nevertheless, organic C concentrations in the
post- and precultural sediment of Wingra are the same order of magni-
tude as found for Mendota and Monona.
-------
116
C. Chemical Stratigraphy of Noncalcareous
Northern Wisconsin Lakes and Devils Lake
in Southern Wisconsin
Cores were taken from two deep-water locations in Little St. Germain,
Minocqua and Trout lakes. The shoreline of these lakes is irregular, and
the lakes are separated into two or more bay areas. Single cores were
taken from the deep-water locations of the lakes with more or less symme-
trical basins--Devils, Little John, Weber and Sparkling lakes.
Little St. Germain
West Bay Profile WC-92. The chemical stratigraphy of Little St.
Germain core WC-92, obtained in the deep-water of the West Bay is given
in Figure 4.12. The sediment consists of a brown-black gyttja throughout
the 85 cm core. The abrupt rise in ragweed pollen at the 35-40 cm level
separates the pre- and postcultural sediment. The most striking feature
of the core is the change in chemical stratigraphy corresponding to the
initial rise in ragweed pollen.
Organic C concentration increases with depth of sediment. The
greatest change in organic C determination occurs at the 35-40 cm ragweed
boundary horizon. Below 35-40 cm in the precultural sediment organic C
concentration is 186-240 mg/g, and above 35-40 cm in the postcultural
sediment organic C decreases to 122-182 mg/g. The organic C profile is
closely related to Fe, Mn and P distribution.
Phosphorus concentration decreases in the postcultural sediments by
approximately one-half that of the precultural sediment. A minimum con-
centration of P (7.4-10.5 mg/g) occurs at the 15-35 cm strata which prob-
ably represents sediment deposited approximately 40-100 years ago. The
sediments laid down at this time were probably associated with the maximum
-------
80 90 100 110
Fe (n,g/g)
0.4
0.6 O.S
Cn (mg/g)
I 1 I
I 10 20 30 40
(counu/100 Eu)
2 3
Mn (mg/g)
1.4 1.8 2.2
Ms fn-Ji'8)
2.6 3.0
Figure A.12 Chemical Stratigraphy of Little St. Germain Profile WC-92, West Bay.
-------
118
disturbance in the watershed from deforestation in northern Wisconsin.
Phosphorus, Fe and Mn concentration profiles are closely related.
The close association is especially illustrated in the small minimum peak
followed separately by P, Fe and Mn at the 50-60 cm level. Presumably,
the depositional efficiency of P is influenced by the Fe-Mn cycle. Of
particular interest in connection with the P, Fe and Mn distribution is
Mackereth's (1966) interpretation of the postglacial sedimentation of
these elements in English lakes. Mackereth felt the two major processes
involved in the sedimentation of P were coprecipitation of P with oxidized
Fe and Mn compounds and precipitation of P incorporated in the organic
material synthesized in the lake. In the sediment of Ennerdale, an un-
productive lake, the profiles of Fe and P concentrations were inversely
related as the sediment surface was approached; Fe rose steadily in con-
centration, while P decreased. Mackereth explained that the precipitation
efficiency for P in Ennerdale basin has not been influenced by variations
in the Fe-Mn cycle, but the precipitation of P was largely biological and
relatively constant. On the other hand, Mackereth believed that the P
concentration was directly related to Fe and Mn distribution in the sedi-
ment of Esthwaite, a productive lake, and that the P minimum in the core
profile resulted directly from loss of Fe and Mn from the lake. Since the
P, Fe and Mn profiles are so closely related, it must be presumed that a
very important part is played by both Fe and Mn, not only in the deposi-
tion of P to the sediment but also its retention therein.
Calcium and Mg concentration profiles form a mirror image to P, Fe
and Mn distribution patterns, and maximum Ca and Mg concentrations occur
at the 10-30 cm strata in the postcultural sediment.
-------
119
Aluminum and K concentrations show a distribution pattern similar to
Ca and Mg. The greatest increase in Al and K coincides with the initial
rise in ragweed pollen at the 35-40 cm horizon. The maximum concentra-
tions of Al, K and Mg are probably associated with increased deposition
of eroded clay minerals.
Upward in the top 10 cm of sediment, P, Fe and Mn concentrations in-
crease and Ca, Mg, Al and K concentrations decrease. This recent trend
in the last 30-40 years may indicate a change toward the sediment condi-
tions of the precultural period.
South Bay Profile WC-56. The chemical stratigraphy of Little St.
Germain core WC-56, obtained in 7 m of water from the South Bay is
given in Figure 4.13. The greenish-black deposits contain macroscopic
fragments of undecomposed vegetation. The top three sections were com-
bined as a composite sample because of insufficient dry material in each
5 cm section.
The depth of the ragweed boundary is somewhat questionable. There
appears to be a secondary rise in ragweed at the 65-70 cm interval which
closely corresponds to the major change in chemical stratigraphy. If the
secondary rise in ragweed is accepted as the actual point in the core se-
quence where the major cultural influence took place, the cores from West
Bay and South Bay would be congruous. If the increase at the 40-45 cm in-
terval is considered the ragweed boundary rise, then it appears that consid-
erable changes in concentration of P, Fe, Mn and organic C occurred prior to
the major cultural influence of approximately 100 years B.P. There are three
possible reasons for accepting the rise at 65-70 cm as a marker of the
cultural influence. The small number of ragweed counts between 70-40
-------
0.3 0.1 0.5 0.6 0.7
t i i i i 1 I
I ' ' I I I I
1111
-J ' ' L
I.I I 1
5 6
7 H 9 10 11 12
P (n.R/R)
10 12 14 16 18 20 22
Al (inR/g)
.0 1.5 2.0 2.5
> in 20 30
(counts/loo Eu)
60 70
Figure 4.13 Chemical Stratigraphy of Little St. Germain Profile WC-56, South Bay.
-------
121
cm may have resulted from the dilution of pollen in the sediment matrix
by an increased sedimentation rate of mineral components. Second, the
ragweed pollen accumulated in the sediment may not have been as responsive
as the chemical changes manifested in the core sequence. Thus, a lag in
the pollen diagram compared to the chemical stratigraphy is observed.
Third, the sedimentation rate of South Bay could conceivably be higher
than West Bay because South Bay is a shallow bay with an extensive lit-
toral area which is highly productive in aquatic weed growth. South Bay
is also in line with the inlet-outlet system, whereas in West Bay the in-
coming material is from direct surface runoff, groundwater and rainfall.
With some reservation, the secondary rise in ragweed at 65-70 cm will be
taken as the cultural base in the South Bay of Little St. Germain.
Phosphorus, Fe and Mn distribution patterns are again similar to
each other; however, the concentrations are lower in South Bay than West
Bay. The importance of obtaining a core of sufficient length to include
the background precultural sediment is shown in profile WC-56. For ex-
ample, if the core were only 60 cm long, the interpretation might be
that P, Fe and Mn concentrations in the top 30 cm are enriched due to the
cultural influences. However, below 60 cm, P, Fe and Mn increase mark-
edly with depth of sediment to the 65-70 cm level. Thus, the impression
would be that the main cultural effect is represented by the 60-30 cm
interval in the core sequence and the top 30 cm of sediment deposited in
the last 35-40 years shows the P, Fe and Mn concentration shifting back
towards the levels found in the precultural sediment.
Aluminum and K concentration remain constant in the top 35 cm of post-
cultural sediment, but in the postcultural sediment (70-35 cm) an upward
-------
122
increase in Al and K is observed. The Ca and Mg profiles show trends sim-
ilar to Al and K.
Long Core L-73. The chemical stratigraphy of Little St. Germain
core L-73, obtained in 3.1 mof water near the outlet of the South Bay, is
given in Figure A.14. The 724 cm core obtained by Charlton (1969) pene-
trated the depth of the postglacial deposits; the generalized sequence of
sediment is a homogeneous organic mud, or gyttja, above clear quartz sand.
The organic mud recovered in the cores did not show any variation in
appearance with depth (Charlton, 1969). Ragweed pollen was not found
throughout the core sequence. This is probably best attributed to the
shallow-water recovery of the core. Apparently, ragweed pollen does not
settle to the bottom muds in regions of the lake where the water is mixed
to keep the pollen resuspended. The C-14 dates shown on Figure 4.14 were
obtained by Charlton (1969).
The change in organic C is quite pronounced during the early history
of Little St. Germain. Organic C increases from 215 mg/g at the base of
the core to 330 mg/g at the 400 cm level. Based on the C-14 date, this
increase occurred over a period of at least 6500 years. Above 400 cm to
the sediment-water interface, the change in organic C concentration sta-
bilizes and fluctuates only slightly from 333 mg/g to 391 mg/g. However,
in the most recent muds, upxvard of 38 cm, organic C concentration remains
high at 382-391 mg/g. A similar postglacial distribution pattern for
organic C has been observed in Windermere and Ennerdale Water in England
by Mackereth (1966) and in Linsley Pond by Hutchinson and Wollack (1940).
The distribution of organic matter in Linsley Pond profile was believed by
Hutchinson and Wollack (1940) to indicate a rapid change from oligotrophy
-------
Organic C
O Phosphorus
I I I I I ' i 1 L.
.1, . I 1 L.
MO
^
250
300
300 340 380
Organic C (n.«/g)
12 14 16 18
Fe (mg/g)
0.15 0.25 0.35
Hn (mg/g)
0.7 O.S 0.^ 1.0 l.| 1.2 1.3
Figure 4.14 Chemical Stratigraphy of Little St. Germain Profile L-73, South Bay
[Carbon-14 Data After Charlton (1969)] .
Ul
-------
124
to eutrophy followed by a long period of approximate equilibrium in
eutrophic conditions.
Maximum concentrations of organic C occur in the upper half of the
mud column for profile L-73. Gorham (1961) noted maximum concentrations
of chlorophyll derivatives, sulfur and carbon were reached slowly in
Ennerdale, an unproductive lake, but in Esthwaite, a productive lake, all
three constituents showed a rapid rise deep in the mud column, which
implies the lake became eutrophic early in its history.
Phosphorus distribution is parallel to organic C concentration through-
out the core sequence. The association of P, Fe and Mn with organic C is
characteristic of the Little St. Germain cores. However, throughout the
long core sequence of L-73 the distribution pattern of Fe and Mn is not
associated with P and organic C. Neither is there a close association of P,
Fe and Mn profiles to each other. Iron fluctuates with depth from 12-18.6
mg/g with no discernible increasing or decreasing trend. On the other hand,
Mn steadily increases with depth of sediment throughout late postglacial
period from the sediment-water interface to the 400 cm level; phosphorus,
organic C and Fe remain more or less constant throughout this period. Be-
low the 400 cm horizon Mn remains constant with depth of sediment.
Calcium, Mg, Al and K concentrations increase upward from the base of
the core to approximately 400 cm. Above the 400 cm level these elemental
concentrations remain constant or fluctuate only slightly to the sediment-
water interface. The basal enrichment of Al, Mg and K probably indicates
the sediment was rich in eroded clays and silts in early postglacial time.
Trout Lake
South Bay Profile WC-59. The chemical stratigraphy of Trout Lake core
-------
125
WC-59, obtained in the deep-water area of the South Bay is given in Figure
A.15. The sediment consists of a dark-greenish-gray to black gyttja. The
organic mud recovered in the cores did not show any variation in appearance
with depth of sediment. The ragweed pollen increases sharply upward at the
35-40 cm level separating the pre- and postcultural sediment. However, it
is noteworthy that there are shifts in the chemical composition of the 105
cm core sequence above and below the ragweed horizon boundary.
The profile of organic C concentration correlates almost exactly with
organic N. Even though the organic C profile is fluctuating, the overall
trend is an increase in organic C with depth of sediment. The minimum
organic C (135-187 mg/g) in the postcultural sediment is probably asso-
ciated with the maximum disturbance from deforestation in the watershed;
however, a minimum organic C peak also occurs at the 45-65 level in the
precultural sediment.
Exchangeable ammonium N increases with depth of burial. The general
increase in exchangeable ammonium N with depth may indicate that organic
materials are undergoing decomposition to ammonia. The ammonium N accumu-
lated may therefore be that formed _in situ. Although the exchangeable
ammonium concentration increases in the deeper layers, it makes up only a
small fraction of the organic nitrogen present.
Phosphorus, Fe and Mn concentration profiles are closely related
throughout the core sequence. The highest concentration of P (6.7-7.8
mg/g) is found in the top 10 cm.of sediment. Phosphorus and Mn concentra-
tions fall within a range of 4-6 mg/g and 2-3.5 mg/g, respectively, except
for departures at three intervalsminimum peaks at 90-95 cm and 35-40 cm
and a maximum peak at 0-10 cm. However, Fe concentration remains constant
-------
13 14 15 16 17 18 19 20
Organic N (m^
Figure 4.15 Chemical Stratigraphy of Trout Lake Profile WC-59, South Bay.
-------
127
below 50 cm in the precultural sediment and fluctuates considerably
above 50 cm.
Potassium and Mg concentration change only slightly with depth of
sediment. In contrast to the Little St. Germain cores, K and Mg con-
centrations do not increase in the postcultural sediment to form a
mirror image to organic C, which might be expected if sedimentation of
eroded clastic material increased concurrently to deforestation.
The oscillations in the chemical stratigraphy of South Trout,which
apparently do not necessarily correlate with the ragweed horizon, maybe
due to a phenomenon peculiar to Trout Lake. Bottom convection currents
along the steep bottom banks of South Trout may cause the sediments to
slump. Thus, sediment which is eroded from the steep slope and rede-
posited to the basin floor may account for the observed fluctuations in
the sedimentary profile. Gould and Budinger '(1958) point to convection
currents as being agents responsible for the observed inequalities in
limnic-peat sedimentation in Lake Washington which occupies a deep
narrow trough. Apparently, in Lake Washington convection currents
associated with winter overturn have extended to the deepest part of
the lake to erode and redeposit sediments.
North Bay Profile WC-6Q. The chemical stratigraphy of Trout Lake core
WC-60, obtained in the center of the North Bay in the deep-water area, is
given in Figure 4.16. The sediment consists of a dark-greenish gray to
black gyttja much the same as South Trout. The ragweed pollen increases
upward fairly abruptly at the 25-30 cm horizon. Contrary to South Trout,
some of the major changes in chemical stratigraphy of North Trout coincide
with' changes in the ragweed profile. Based on the ragweed pollen profile,
-------
Mn
lit) 16'.) ISO 20V 220 240
Organic C (mg/gl
Figure 4.16 Chemical Stratigraphy of Trout Lake Profile WC-60, North Bay.
CO
-------
129
the sedimentation rate of North Trout is less than South Trout.
Organic C concentration (134-167 mg/g) is lowest in the postcultural
sediment. The largest upward decrease in organic C occurs simultaneously
with the break in the ragweed curve. Even though organic C concentration
generally increases with depth, it appears that organic C deposition is
represented by the following three trends: (1) constant concentration
(95-65 cm), (2) an upward decrease (60-30 cm) and (3) an accelerated up-
ward decrease in the postcultural sediment.
Phosphorus, Fe and Mn distribution patterns again show a strong
association to each other and form a mirror image to organic C. For both
South and North Trout cores, P, Fe and Mn become enriched in the uppermost
10 cm. The concentration of P in the top 10 cm is 7.4-9.9 mg/g which is
approximately 4-5 times higher than the mean concentration of P found in
the precultural sediment. The top 10 cm of sediment is probably repre-
sented by sediments deposited 25-35 years B.P.
Calcium and Mg concentrations increase in the precultural sediment.
On the other hand, Al and K profiles fluctuate with depth of sediment. Un-
expectedly, the maximum concentrations of Al, K and Mg are found in the
precultural sediment at the 60-90 cm interval.
Lake Minocqua
Profile WC-51. The chemical stratigraphy of Minocqua core WC-51,
obtained in 10.7 m of water in the deep-area of the northwest bay is
given in Figure 4.17. The sediments consist of a homogeneous brown-black
gyttja. The rise in ragweed at the 10-15 cm level separates the pre- and
postcultural sediment.
Organic C generally "increases with depth of sediment throughout the
-------
Mn (mg/g)
0.5 0.6 0.7 0.8
10
20
30
v 40
50
10
20
30
40
50
150 170 190
Organic C (mg/g)
456
P (mg/g)
2 3
Ca (mg/g)
10
Mg (mg/g)
K (mg/g)
0 10 20 30 40 50
Ragweed (counts/100 Eu)
50
Fe (mg/g)
60
25
Al
30 35
(mg/g)
Figure 4.17 Chemical Stratigraphy of Lake Minocqua Profile WC-51, Northwest Bay.
-------
131
50 cm core, although from the sediment-water interface to the base of the
cultural horizon (0-15 cm), organic C concentration increases more rapidly
with sediment depth.
Phosphoi'us , Fe and Mn concentration profiles are closely related and
tend to form a mirror image to organic C. In the precultural sediment,
P, Fe and Mn remain constant or increase slightly in an upward direction.
In the top 15 cm of sediment these elements become enriched. For example,
the P concentration increases 2-3 fold in the postcultural deposits over
the P found in 35 cm of precultural sediment examined. The increase in P
concentration in the upper sediments may be partially attributed to the
discharge of sewage from a secondary treatment plant into the northwest
bay in 1935-1964.
Calcium, Mg and Al concentrations remain practically constant with
depth of sediment. However, K concentration decreases in the top 10 cm
of sediment.
Profile WC-52. The chemical stratigraphy of Minocqua WC-52, obtained
in 13.7 m of water in the deep-water area of the southwest bay, is given
in Figure 4.18. The increase from low to high ragweed counts occurs at
the 25-30 cm horizon. Based on the rise in ragweed pollen, the sedimenta-
tion rate in the southwest bay, which is fed by an inlet stream, is great-
er than in the northwest bay. In both Minocqua cores the rise in ragweed
coincides very closely with the major changes in chemical stratigraphy.
Organic C concentration remains constant in the precultural sediment
below 30 cm and generally decreases upward in the postcultural deposits
(30-0 cm). Concurrent with the decrease in organic C concentration most
of the other sedimentary components increase in concentration. Thus, it
-------
T 1 1 I I
T 1 1 1 r
1 r
50
i ii
n 1 1 r
1 I
I.'.D 161
0tganlc C
(mg/g|
6 7 H 9 10
P (mg/g)
1.2 1.4 1.6 1.8 2.0
Mn (mg/g)
1.0 1.5 2.0 2.5
Ca (mg/g)
I 1111
15 20 25 30 35
A) (mg/g)
i l I I 1
0 10 20 30 '*0
( counts/ 100 EAJ )
45
50 55 60
Fe (nig/jj)
65 70
1.5 2.0 2.5 3.0 3.5
MR (mg/g)
1 2 3 4 5 6
Figure 4.18 Chemical Stratigraphy of Lake Minocqua Profile WC-52, Southwest Bay.
U)
ro
-------
133
appears that organic C is effected by dilution of inorganic materials.
Phosphorus, Fe and Mn profiles in the southwest bay are not as closely
related as that in northwest bay. For example, phosphorus and Mn increase
in the top 15 cm of sediment, while Fe increases in the top 30 cm corres-
ponding to the ragweed rise. Maximum P concentrations (8-9.5 mg/g) are
found in the top and bottom of the core although the P in the postcultural
sediment is accompanied by a proportionally higher Fe and Mn content than
in the precultural sediment.
Magnesium, Al and K concentrations increase markedly at the 25-30 cm
horizon which corresponds exactly to the initial rise in ragweed pollen.
Calcium concentration remains nearly constant with depth.
The following observations can be made on profile WC-52. First, phos-
phorus does not increase in the postcultural over the precultural sediment
in relation to the increase in Fe, Mn, Al, K, and Mg compounds which should
provide a favorable sorption environment for P retention. Livingstone and
Boykin (1962) noted that in Linsley Pond high P binding capacity is corre-
lated with high mineral content of the lake mud. Thus, as the rate of
mineral sedimentation falls, so does the P content of the mud. It is
doubtful the rate of supply of P has decreased in recent times; therefore,
the P finally residing in Minocqua sediment may also depend on the rate of
loss of P from the sediment to the water phase and the rate of accumulation
of the whole sediment. Second, Al, K and Mg concentrations show pronounced
changes in the postcultural sediment in southwest bay, whereas these ele-
ments remain constant with depth in the northwest bay. Third, both a mini-
mum and maximum P concentration are found in the postcultural sediment. .
-------
134
Weber Lake
The chemical stratigraphy of Weber Lake core WC-66, obtained in the
center of the lake, is given in Figure 4.19. The sediment consists of a
black-brown organic mud, or gyttja. The most interesting feature of the
core is the pronounced fluctuation in chemical composition with depth of
sediment. Ragweed pollen increases sharply at the 15-20 cm level which in-
dicates the sedimentation rate of Weber Lake would be relatively low.
Organic C concentration varies from 246-367 mg/g throughout the core;
however, the mean concentration of organic C is greater in the precultural
deposits than in the upper 20 cm of recent sediment. A large maximum peak
of organic C is found deep in the precultural sediment at 55-70 cm.
Phosphorus concentration fluctuates considerably, but within a narrow
range of 2.8-3.9 mg/g P. Iron and Mn concentration profiles are not
closely related to P as shown for most of the other cores examined. Scien-
tific experimental studies involved the addition of superphosphate to the
lake from 1932-1936 to increase the productivity (Potzger and Van Engel,
1942); the annual addition of superphosphate fertilizer to water was as
follows: 1932 - 750 pounds; 1933 - 500 pounds and 1934 - 500 pounds. This
addition of fertilizer has no observable effect of increasing P concentra-
tion in the recent sedimentary column.
Iron concentration (10-11.5 mg/g) remains nearly constant throughout
most of the column (10-70 cm), but increases near the top and bottom of the
core.
Manganese and Mg concentrations remain more or less constant with
depth of sediment.
Aluminum and K concentrations fluctuate widely with depth of sediment
-------
30
240 2bO 2») 300 320 340 360
Orcnnic C
-------
136
although the two profiles show similar distribution patterns. A close in-
spection of the core sequence reveals that Fe, Al, K and Mg show the same
inflections (minimum and maximum peaks) and form a mirror image to organic
C. Weber Lake is the only northern Wisconsin lake studied in which Fe
appears to be closely related to Al, K and Mg concentration profiles. As
I
a comparison, Fe is always closely associated to the K and Al profiles in
the southern Wisconsin calcareous lakes.
The oscillations in the chemical stratigraphy were somewhat unexpected
in view of the slow sedimentation rate of Weber Lake. Theoretically, a slow
sedimentation rate should allow more time for the mixing of old and new
sediment layers thus producing an integrated sediment smoothing out exag-
gerated peaks. In order for the pronounced peaks to persist the depth of
the sediment mixing column must be short.
The overall Weber Lake sediment sequence shows few trends of increas-
ing or decreasing concentrations. The fluctuations may possibly be attri-
buted to changing lake level causing differential leaching and erosion of
the shoreline. A small seepage lake, such as Weber Lake, may be affected
easily by changing precipitation patterns^ which may in turn change the lake
level.
Little John Lake
The chemical stratigraphy of Little John WC-67, obtained in 5 m of
water in the center of the lake, is given in Figure 4.20. The core is about
twice the length of most cores obtained from the northern Wisconsin lakes.
The sediments were a flocculate brown-black gyttja throughout the 175 cm
core. Even though the entire core was fractionated in the field into 5 cm
intervals, chemical analyses were performed on every other section below
-------
Mn (fg/K)
0.6 0.6
Figure 4,20 Chemical Stratigraphy of Little John Lake Profile WC-67.
OJ
-------
138
100 cm in the core.
Some of the most pronounced changes in chemical stratigraphy corres-
pond to the initial rise in ragweed at the 40-45 cm level. The sedimenta-
tion rate based on the ragweed curve for Little John is high compared to
most of the northern lakes examined.
Organic C concentration shows a sharp decline above 40 cm to the sed-
iment-water interface. The decrease in organic C is accompanied by an in-
crease in concentration of P, Fe and Mn compounds. In the precultural
sediment from 40-150 cm organic C fluctuates between 308-364 mg/g. Below
140 cm the organic C tends to decrease.
Phosphorus, Fe and Mn concentrations increase upward throughout the
length of the core; however, above 40 cm in the postcultural sediment,?,
Fe and Mn shox^ an accelerated increase. For example, P increases from
approximately 1 to 1.6 mg/g in the precultural sediment from at least 300-
400 years B.P. to approximately 100 years B.P., then the P concentration
increases rapidly from 1.6 to 4.2 mg/g in the postcultural sediment. There
is considerable parallelism in the P, Fe and Mn profiles.
Calcium and Mg concentrations remain nearly constant within a range
of 1.7-3.6 mg/g and 3-4.6 mg/g for Ca and Mg, respectively. Aluminum and
K concentration remain nearly constant and fluctuate within a narrow con-
centration range throughout the core. Little John Lake is a spring-fed lake
with no inlet streams which may account for the fact that the concentration
of mineral products containing K and Al did not increase concurrently to
changes in ragweed pollen and several chemical components.
Devils Lake
.The chemical stratigraphy of Devils Lake core WC-75, obtained in 13.1
-------
139
m of water, is given in Figure 4.21. The sediments were a greenish-black,
unstratified gyttja throughout the 95 cm core. Nothing is known of the
thickness of the muds. A marked increase in ragweed abundance occurs at
the 10-15 cm horizon.
Organic C concentration generally increases with depth of sediment.
i
It appears that organic C deposition is represented by three trends: (1)
constant concentration (95-60 cm), (2) an upward decrease (60-15 cm and
(3) an accelerated upward decrease in the postcultural sediment.
Phosphorus, Fe and Mn concentration profiles are similar to each other
and form a mirror image to the organic C profile. The top 15 cm of post-
cultural sediment becomes enriched in P, Fe and Mn while organic C de-
creases markedly. The initial rise in P, Fe and Mn concentration at the
60 cm level is estimated to be at least 400-600 years B.P. based on the
sedimentation rate calculated from the recent rise in ragweed.
Calcium and Mg concentration profiles also develop a double break in
stratigraphy forming a mirror image to the organic C profile. The magni-
tude of change in concentration, however, is only slight with depth of
sediment.
The K concentration remains nearly constant with depth of sediment
except in the top 15 cm of postcultural deposits where K increases markedly.
Aluminum concentration increases generally throughout the entire core, but
the most pronounced increase in Al occurs at the 55-60 cm level which cor-
responds to the early break observed for P, Fe, Mn and organic C concentra-
tions .
Sparkling Lake
The organic C and ragweed profile of Sparkling Lake core WC-65,
-------
Hn
-------
141
obtained in the center of the southern half of the lake, is given in
Figure 4.22. The sediment consists of a black-brown organic mud, or
gyttja.
The only determinations made on WC-65 were organic C and ragweed
pollen counts. Ragweed pollen counts increase sharply at 10-15 cm separ-
ating the pre- and postcultural sediment. The ragweed curve indicates the
sedimentation rate for Sparkling Lake is low. Concurrent with the increase
in ragweed, organic C concentration decreases rapidly (15-0 cm). In the
precultural sediment below 15 cm, organic C concentration fluctuates be-
tween 225-278 mg/g. But the most dramatic decline in organic C occurs in
the postcultural sediment.
Comparison of Mean Concentrations in Pre- and Postcultural Sediments
in Noncalcarcous Lakes. The mean concentration of various chemical com-
ponents for pre- and postcultural sediments of Little St. Germain, Trout,
Minocqua, Weber, Little John and Devils lakes are shown in Table 4.8. A
comparison of the mean concentration of postcultural over precultural sed-
iment is presented as a ratio, _K, in Table 4,9.
Cores were obtained from separate bay areas in lakes with an irregular
shoreline. Considerable differences as well as similarities exist in the
mean concentration and the relative change of chemical components in the
pre- and postcultural sediment of cores from the same lake.
The cores from Little St. Germain West Bay and South Bay are very
similar to each other (accepting 65-70 cm ragweed boundary for South Bay).
Both cores show an increase in Al, K, Mg and Ca and a decrease in organic
C, P and Mn concentrations in the upper layers of sediment. In West Bay
the concentrations of P, Fe and Mn are higher than South Bay throughout
-------
180 200 220 240
Organic C (mg/g)
- 90
100
Figure 4.22
10 20 30 40 50 60
Ragweed (counts/100 Eu)
Organic Carbon and Ragweed Pollen Profiles for Sparkling Lake Core WC-65.
-------
Table A. 8 Mean Concentration of Pre- and Postcultural Sedimentary Components for Noncalcareous Lakes,
Core
Little St. Germain
W. , WC-92
* S. , WC-56
Trout
N. , WC-60
** S. , WC-59 *
Minocqua
S.W. , WC-52
N.W. , WC-51
Weber
WC -66
Little John
WC-67
Devils
WC-75
a
b
a
b
a
b
a
b
a
b
a
b
a
b
a
b
a
b
Org-C
145
217
210
235
145
223
155
189
127
151
161
181
282
317
288
333
81.0
129
P
8.85
14.1
6.15
10.6
5.73
1.81
5.43
4.71
7.33
7.24
5.80
3.01
3.06
3.23
3.14
1.65
1.68
1.02
Fe
89.2
96.2
49.5
52.3
52.1
40. 1
55.6
57.2
58.6
44.7
50.4
42.3
11.9
11.3
44.9
35.7
34.4
24.8
Mn
m t> / p
>u&' &
1.27
2.34
0.407
0.627
2.35
1.23
2.69
2.50
1.59
1.29
0.670
0.524
0.225
0.287
0.692
0.453
0.372
0.247
Al
15.0
9.38
16.1
9.37
25.9
29.2
--
--
35.6
15.0
28.8
29.8
29.0
28.4
22.0
25.9
92.7
74.2
K
3.54
2.08
3.64
1.54
4.55
4.96
1.33
1.32
6.55
3.59
8.45
9.08
6.64
5.95
4.86
5.21
13.4
9.09
Mg
2.44
1.63
2.17
2.11
3.24
3.75
2.44
2.56
3.33
1.97
3.54
3.74
2.46
2.21
3.71
4.25
4.81
3.84
Ca
0.63
0.50
1. 15
0.63
2.39
3.69
3.37
3.72
1.80
1.54
2.33
2.58
0,635
0.864
2.54
3.07
2.29
1.79
a Mean concentration of postcultural sediment
Mean concentration of precultural sediment
** HC104-HNO digestion (w/o HF)
* Mean concentration calculated using '65-70
cm horizon separating pre- and postcultural
sediments
-------
144
Table 4.9 Comparison of Mean Concentration of Postcultural over Pre-
cultural Sedimentary Components for Noncalcareous Lakes.
Core Org-C P Fe Mn Al K Mg Ca
K
Little St. Germain
W. , WC-92 -- -- 0 -- +++ +++ ++ ++
S. , WC-56 0 - ++ 0 ++ +++ +++ +++
Trout
N. , WC-60 -- +++ ++ +++ 0 - 0
S. , WC-59 - + 0 0 n.d.O 0 0
Minocqua
S.W. , WC-52 - 0 ++ ++ +++ +++ +++ +
N.W., WC-51 - +++ + ++ 0 0 0 0
Weber
WC-66 0 0 -- 0 + +
Little John
WC-67 - +++ ++ +++ _ 0 - -
Devi Is
WC-75 -- +++ ++ +++ ++ ++ ++ f+
mean concentration of postcultural sediment
K _ . __c _ _ (see Table 4.8)
mean concentration or precultural sediment
Notation: 1.1^K>0.9 = 0 1.11.5 = +++ K< 0.5 = ---
n.d. = no determination
-------
145
the cores.
In the cores from the North and South Trout Lake, considerable sim-
ilarity is noted in the order of magnitude of the mean concentration of P,
F<_, Mn and organic C in the postcultural sediments. Also as shown in Table
4.9, the K values for K, Mg, Ca are similar for the two Trout Lake cores.
The mean concentrations of Fe and Mn are higher in the postcultural than
the precultural sediments of North Trout, while Fe and Mn are almost con-
stant with depth of sediment in South Trout. Both Trout Lake cores show a
decrease in organic C and an increase in P in the postcultural sediments.
There are probably more differences than similarities in the concen-
tration profiles of the two Minocqua cores obtained from the southwest bay
and the northwest bay. The K value for Al, K, Mg and Ca is positive in the
southwest bay, which is connected to an inlet stream, and zero in the north-
west bay. The relative distribution of P concentration in the postcultural
over precultural sediments of the two bays is quite different. In the north-
west bay which received sewage effluent directly from the town of Minocqua,
the K value is positive, and in the southwest bay the K value is negative.
But the sedimentary concentration of P is greater in the southwest bay which
is further from the point of sewage discharge than in the northwest bay. The
Fe concentration is about the same in sedimentary profiles of the two cores.
Weber and Little John lakes which are seepage and spring-fed lakes, re-
spectively, contain the highest concentration of organic C of the lakes ex-
amined in both pre- and postcultural sediments. On the other hand, Weber
and Little John lakes contain low P and Fe compared to the other lakes. In
Weber Lake the K values are mostly zero or minus; potassium and Mg are the
only elements that increase in the postcultural sediment of Weber Lake.
-------
146
Phosphorus, Fe and Mn are the only elements that show a positive in-
crease in the postcultural sediments of Little John Lake.
In Devils Lake all the constituents except organic C show a positive
K value.
A trend which is common to all the northern noncalcareous lakes is
an increase of organic C with depth of sediment. With the exception of
organic C, in all the noncalcareous lake cores examined, the chemical
components do not display a consistent pattern of increasing or decreas-
ing concentration in the postcultural over the precultural sediment. In
nearly all the lake cores examined, P, Fe and Mn concentration profiles
are closely related both in the pre- and postcultural sediment. The
only exceptions to this observation are oligotrophic Weber Lake and the
shallow water core from the South Bay of Little St. Germain. A close
association of organic C with P, Fe or Mn profiles is found in the Little
St. Germain cores only. Generally organic C concentration profiles form
a mirror image to P, Fe and Mn.
-------
147
D. Estimation of Sedimentation Rates
Using Ambrosia Pollen
The horizon in a core sequence exhibiting a marked increase in
ragweed abundance provides an estimation of sedimentation rate as well
as an identification of postcultural and precultural sediment deposi-
tion. Historical records of deforestation in northern Wisconsin indi-
cate extensive logging commenced during the period of 1850-1870 and in-
creased to peak lumber production by 1899 (Curtis, 1959). Fires swept
through the slashings on most lumbered areas creating open lands (Roth,
1898). The southern part of the state was rapidly converted to farm
lands by the increasing tide of immigrant settlers. The population of
Wisconsin increased from 3,200 in 1830, to 305,000 in 1850 and to
1,315,000 by 1880; in the same intervals, the acreage devoted to crop
production increased from about 400,000 to 2,900,000 to 15,300,000
(Curtis, 1959). In order to compute sedimentation rate, one century
will be used as the time period since the major disturbance of defor-
estation and land clearing commenced in Wisconsin. After the time hori-
zon in each of the cores has been identified, the recent rate of depo-
sition can be calculated. This gives an estimation of the average
annual deposition since the commencement of cultural activities, as
shown in Table 4.10 for calcareous and noncalcareous lakes. The esti-
mated sedimentation rate for most of the noncalcareous lakes ranges
from 4.0-4.5 mm/yr to 1.0-1.5 mm/yr. Higher sedimentation rates of
3.5-4.0 mm/yr to 6.5-7.0 mm/yr are observed for the calcareous
lakes. The sedimentation rate for the deep-area of Lake Mendota is
3.5-4.0 mm/yr which is the lowest observed for the calcareous lakes.
Nriagu and Bowser (1970) found that the first appearance of magnetic
-------
148
Table 4.10 Estimated Sedimentation Rate in Lake Deposits Based on
the Depth of Ambrosia Pollen Increase in the Core Column.
Estimated Sedimentation
Rate in Noncalcareous
Lake Lakes in Order of
Decreasing Rate
(mm/yr)
Estimated Sedimentation
Rate in Calcareous Lakes
Lake i n Order of Decreasing
Rate
(mm/yr
Little St.
Germain, S.
Little John
Trout, S.
Little St.
Germain, W.
4.0-4.5
(6.5-7.0)'
4.0-4.5
3.5-4.0
3.5-4.0
Wingra
Monona (WC-46)
6.5-7.0
5.0-5.5
Mendota (WC-84) 4.5-5.0
Mendota (WC-86) 4.0-4.5
Mendota (WC-89) 3.5-4.0
Trout, N.
2.5-3.0
Minocqua, S.W. 2.5-3.0
Weber
1.5-2.0
Sparkling
1.0-1.5
Devils
1.0-1.5
Minocqua, N.W. 1.0-1.5
^Secondary rise in ragweed at 6.5-7.0 cm horizon
-------
149
spherules occurred at the 35-40 cm level in deep-water Mendota core.
They suggested that these spherules are flue products derived from in-
dustrial and domestic activities supplied to the lake through the
action of washing the atmosphere or as the detrital load from urban run-
off. The ragweed pollen increase corresponds exactly to the level of
increase for magnetic spherules in the Mendota deep-water core. Thus,
the appearance of these stratigraphic markers indicates the base of the
cultural horizon in the Mendota core.
A lake with a fast sedimentation rate should contain a small amount
of pollen in the enclosing sediment compared to a lake with a slow sedi-
mentation rate. To test this hypothesis, the mean ragweed count/100
3
eucalyptus grains (Eu)/cm (wet) was calculated for the postcultural
and precultural sediments for each northern lake. These values do not
represent absolute counts of ragweed grains but only relative counts to
the internal standard of eucalyptus pollen. The mean ragweed counts
o
per cm of wet sediment in the pre- and postcultural sediments are
arranged in increasing order in Table 4.11. This order generally con-
curs with the lakes arranged in order of their decreasing sedimentation
rates based on the break in the ragweed pollen profile. If the ragweed
3
counts/cm of mud is high, the pollen is not diluted by a high back-
ground matrix of sediment; therefore, the sedimentation rate of the
lake should be low. On the other hand, if the sedimentation rate is
high, the pollen should be diluted in the enclosing sediment to produce
a low ragweed count/cm in the mud. For instance, in both the pre- and
postcultural sediment, Weber, Sparkling and Devils lakes contain high
ragweed counts in the sediment matrix and show a loxv sedimentation rate
-------
150
Table 4.11 Ragweed Counts in Sediment Matrix as a Relative Measure
of Sedimentation Rate in Pre- and Postcultural Sediment
of Noncalcareous Lakes.
Lake
* Mean Ragweed
Count/100 EU/CJTI
for Postcultural
Sediment in In-
creasing Order
Lake
Mean Ragweed
Count/100 Eu/cnT
for Precultural
Sediment in In-
creasing Order
Little St.
Germain, S.
Trout, S.
Little John
7.25
8.25
8.34
Trout, S.
Minocqua, S.W.
Little St.
Germain, S.
0.39
18.6
21.7
Minocqua, S.W. 8.85
Little St. 8.91
Germain, W.
Little St.
Germain, W.
Little John
21.8
23.7
Minocqua, N.W. 10.8
Weber 11.9
Trout, N.
Sparkling
43.8
50.S
Sparkling
15.4
Weber
50.7
Trout, N.
15.5
Minocqua, N.W.
66.3
Devils
32.8
Devi Is
90.5
* Relative counts of ragweed in sediment matrix based on the formula:
ragweed counts/g dry sed. g dry sed. g wet sed.
(in each 5 cm core section) 1 g wet sed.
Cm wet
number of sections in postcultural (or precultural) sediment
-------
151
based on the increase of ragweed in the core column. On the other hand,
Little St. Germain and Little John lakes which have a high sedimenta-
tion rate also contain fewer ragweed in the sediment matrix. Since the
relative ragweed counts in the sediment matrix follow expected trends
based on the sedimentation rates calculated for various cores, it lends
support to the validity of estimating sedimentation rates from ragweed
profiles and known historical records.
-------
152
E. Postcultural Sedimentation Intensity
The profiles presented thus far are concentration-depth curves.
Graphs of concentration vs. wet sediment thickness do not give a com-
plete picture of deposition rates because compaction, as well as age,
increases with depth. If the thickness per unit time, water content
and density of the deposits are known, sedimentation intensity of a
2
chemical component (ing/cm /yr) can be calculated. This calculation can
be made for the postcultural column in each core using the ragweed
pollen as an estimate of the thickness of sediments since the onset of
the cultural period. To give the rate of sedimentation in units of
weight per unit area and time allows a comparison of lakes of differing
composition, moisture content and compaction.
Southern Calcareous Lakes. The data for sedimentation intensity
of several chemical components are given in Table 4.12 for lakes Monona,
Wingra and Mendota. An example calculation of sedimentation intensity
of P in Mendota core WC-89, is given in Table 4.13. It should be em-
phasized that the sedimentation intensity shown for the chemical com-
ponents may not be representative of the entire lake, but only for the
location in the lake where the cores were obtained. For example, the
sedimentation intensity of organic C is about 3 times less for the
Lake Mendota deep-water core than University Bay core K'C-84. The sedi-
mentation intensity of all chemical components investigated is higher
in University Bay than the deep-water area of Lake Mendota. Even
though the concentrations of P, Fe, Mn and Ca increase with water depth
from University Bay to the deep-water area, the deposition rate of these
-------
Table 4. 12 Sedimentation Intensity of Postcultural Sedimentary Components for
Calcareous Lakes.
Lake
Mendota *
WC-89
Mendota
WC-86
Mendota
WC-84
Wingra
Monona *
WC-46
Org-C P
526 1.1.9
825 14.0
1698 19.1
1137 8.98
1184 # 19.2
Fe
151
223
342
127
205
Mn
2
rag /cm / 100
8.30
8.45
11. 1
9.40
8.84
Ca
\TT
800
1130
1620
3920
1600
Mg
79.4
159
289
157
16 1#
Al
268 **
509
659
477
39 6 #
K
72.2
128
189
83.6
107 #
* HC104-HNO digestion (w/o HF)
** Assuming mean concentration of Al in postcultural sediments from WC-95
# Assuming mean concentration of organic C, Al, Mg and K from entire 105 cm column
of WC-101
U)
-------
Table 4.13 Calculation of Sedimentation Intensity of Phosphorus for Lake Mendota
Core WC-89.
Interval
Depth
(cm)
0-5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
Density
3
(g/cm )
1.07
1.11
1.11
1.05
1.07
1.07
1. 10
1.08
Dry Solids
Content
g dry wt .
g wet wt .
0. Ill
0.162
0. 194
0. 190
0. 173
0. 164
0.161
0. 163
Interval
Length
(cm)
5
5
5
5
5
5
5
5
Cone, of
P
mg
g dry wt.
1.79
1,79
1.31
1.64
1.68
1.96
1.74
1.55
Wt. of P
below Sed-
iment Sfc.
2
(mg/cm )
1.06
1.61
1.41
1.64
1.56
1.72
1.54
1.37
Cumulative Wt .
of P below
Sediment Sfc.
r\
(mg/-cm )
1.06
2.67
4.08
5.72
7.28
9.00
10.5
11.9 *
* Sedimentation intensity of postcultural P = 11.9 mg P/cm 7100 yr
Ln
-------
155
components on a weight per unit area and time basis decreases with
water depth. The higher-deposition rate of P, Fe, Mn and Ca in
University Bay is a function of a greater accumulation of sediment, as
shown by the depth of the ragweed profile, and a higher percentage of
dry solids in the University Bay cores than in the cepter of the lake.
o
Lake Wingra has a low P sedimentation intensity, 8.98 mg P/cm /
2
100 yr, compared to 11.9-19.1 mg P/cm /100 yr for Mendota and 19.2 mg P/
2
cm 7100 yr for Monona. The sedimentation intensity of Fe is also lower
in Wingra than Mendota or Monona, but the sedimentation intensity of Mn
is about the same for all three lakes. The deposition rate of organic
C in Wingra and Monona is about 2 times that found for the deep-area of
Mendota.
The sedimentation intensity of the chemical components from Monona
fall within the range of values found for Mendota.
Noncalcareous Lakes. The sedimentation intensity of the chemical
components from the profundal sediments of noncalcareous lakes is shown
in Table 4.14. It is difficult to generalize about trends in comparing
the sedimentation intensity of the various lakes.
The sedimentation intensity of organic C varies from 159-514 mg/
2 2
cm /100 yr which is lower than the calcareous lakes (526-1184 mg/cm /
100 yr). There appears to be little relation between the productivity
classification of a lake and the sedimentation intensity of organic C.
The sedimentation intensity of P is highest for Little St. Germain
2
(20.5 mg P/cm /100 yr) and lowest for the two oligotrophic lakes,
2
Devils and Weber (2.76-4.06 mg P/cm /100 yr). The P deposition rates
-------
Table 4.14 Sedimentation Intensity of Postcultural Sedimentary Components for Noncalcareous Lakes.
Lake
Little St. Germain
W. Bay, WC-92
Trout, N. Bay
WC -60
Trout, S. Bay
WC-59
Minocqua,
S.W. Bay, WC-52
Minocqua
N.W. Bay, WC-51
Weber
Little John
Devils
Org-C
338
293
358
255
159
255
514
196
P
20.5
11.6
12.6
14.7
5.75
2.76
5.59
4.06
Fe
207
106
129
118
49.8
10.8
80.0
83.4
Mn
.. mg/cm2/100
2.95
4.75
6.21
3.20
0.664
0.204
1.23
0.900
Ca
\7f
1.46
4.83
7.79
3.62
2.31
0.575
4.52
5.55
Mg
5.67
6.55
5.64
6.70
3.50
2.22
6.60
11.6
Al
34.8
52.4
__
71.5
28.6
26.2
39.2
224
K
8.21
9.20
3.08
13.2
8.36
6.00
8.65
32.5
* HC10 -HNO digestion ( w/o HF)
-------
157
of the two Trout Lake cores are similar to each other, but in the two
Minocqua cores the sedimentation intensity differs by 2-fold. The
2
deposition rate of P ranges from 2.76 to 20.5 mg/crn / 100 yr in the
noncalcareous lakes. The high end of this range is approximate to the
2
sedimentation intensity of 8.9-19.2 mg P/cm /100 yr found in calcareous
lakes. However, it is observed the sedimentation intensity of Fe and
Mn is always higher in calcareous lakes than noncalcareous lakes.
Dry Sediment Accumulation. Another way to examine sedimentation
is to follow the dry matter accumulation through time. The dry sedi-
ment accumulated is shown in Table A.15 for the postcultural sediment
from the noncalcareous and calcareous lakes. A comparison is given in
grams of dry sediment accumulated below one square centimeter since the
onset of the cultural period. The dry sediment accumulated varies
2 2
from 0.905 to 2.42 g/cm and from 7.15 to 17.2 g/cm for noncalcareous
and calcareous lakes, respectively. The postcultural accumulation of
dry sediment is approximately the same for the noncalcareous lakes
with the exception of Weber and the northwest bay of Minocqua. For the
calcareous lakes, University Bay core WC-84 and Wingra have the highest
2
dry sediment accumulation (17.2-16.5 g/cm ), and the deep-water core of
2
Mendota the lowest (7.15 g/cm ).
-------
158
Table 4.15
Dry Sediment Accumulated below One Square Centimeter of Mud
Surface Since the Onset of the Postcultural Period.
Lake
Dry Sediment Accumu-
lated in Postcultural
Sediments of Noncal-
careous Lakes in
Decreasing Order
2
g/cm
Lake
Dry Sediment Accumu-
lated in Postcultural
Sediments of Cal-
careous Lakes in
Decreasing Order
g/cm
Devils Lake
Little St.
Germain ,
W. Bay
Trout,
S.
Trout,
N.
Minocqua ,
S.W. Bay
Little John
Minocqua ,
N.W. Bay
Weber
2.42
2.32
2.31
2.02
2.01
1.78
0.990
0.905
Mendota
WC-84
Wingra
Monona
WC -46
Mendota
WC -8 6
Mendota
WC-89
17.2
16.5
12.2
11.1
7.15
-------
159
F. Sorption and Desorption of Added Inorganic
Phosphorus to Pre- and Postcultural Sediments
The capacity of lake sediments to retain or release P is undoubt-
edly one of the important factors which influence the concentration of
P in the lake water. The purpose of this laboratory study is to assess
the P sorptive characteristics on selected strata representing pre- and
postcultural sediments. If the chemical composition of the sediments
has changed historically, presumably the P sorptive and desorptive
capacity of the sediment will also be influenced.
The sediment capacity for sorption and desorption of P is illus-
trated in Table 4.16 for a representative pre- and postcultural stratum
in calcareous cores and for soil samples in a woodland and cultivated
region of the Lake Mendota watershed. Grab sediment samples were taken
at a depth of 4-5 inches below the soil surface from the woodland area
of Picnic Point and from the cultivated Eagle Heights garden area near
Second Point. For all the sediment and soil samples, the percent of
the total added P sorbed decreases as the initial level of added P in-
creases. The P desorbed as a percent of the added P sorbed generally
increases with higher initial levels of added P. The behavior of the
P sorptive complex will depend on variations in temperature, pH, ionic
strength and contact time. The samples were shaken for 40 +_ 4 hours at
ambient temperature in 0.1 N NaCl. The pH and temperature of the solu-
tions are presented with the results.
Lake Mendota. The aerobic sorption and desorption of P indicate
the postcultural gyttja is a more favorable sorptive and less favorable
desorptive environment for P than the precultural marl. In other words,
the sediment which sorbed the most P during the sorption step released
-------
Table 4.16 Sorption and Desorption of Added Inorganic Phosphorus to Pre- and Postcultural Sediments
of Calcareous Lakes, Woodland and Cultivated Soil in Lake Mendota Watershed.
Depth of
Lake Sediment
(cm)
*Mendota
(WC-89) 5-10
Mendota
(WC-89) 70-75
* Wingra
(WC-92) 5-10
Wingra
(WC-92) 85-90
Monona
(WC-101) 5-10
Monona
(WC-101) 95-100
Woodland
Soil
Cultivated
Soil
Added P
Sorbed as %
Total Added
5
90
76
23
33
80
63
29
24
10
66
37
14
23
67
48
13
9
25
44
23
10
16
41
33
8
3
Added P De-
of sorbed as % of
P Added P Sorbed
for Initial P Level (jig
50 5 10 25 50
30
13
6
11
30
23
1
4
2
42
57
44
18
12
49
29
17
36
57
41
11
25
58
61
29
38
63
42
17
26
72
100
27
47
61
47
18
24
88
96
Net t
Sorb!
Tota
P/ml)-
5
89
44
12
19
66
56
15
17
Added P
2d as % of
1 Added P **
10
56
29
6
13
60
37
5
3
25
34
14
4
9
34
24
2
0
50
22
8
2
6
25
20
0
0
pH after
sorption
7.8
7.9
7.9
8.4
7.9
8.0
6.1
6.6
Temper
pH after ature
desorption (°C)
8.2
8.3
8.1
8.5
8.0
8. 1
6.6
6.9
24-28
24-28
28-29
28-29
28-29
** Following sorption and desorption steps
* The lowest initial P level for Mendota (WC-89) and Wingra (WC-92) was 2.5
solution used
P/ml, 40 ml P
-------
161
the least P during the subsequent desorption. The net sorption (after
sorption and desorption) of added P, expressed as a percentage of total
added P, is higher for the postcultural sediment than the marl. Thus,
'it appears that the modern sediment has a greater capacity to retain P
than the sediments laid down for a long historical period.
The effect of pH on the sorption of P is shown in Figure 4.23 for
Mendota postcultural sediment. The maximum uptake of P occurs at pH
4-6.5. This data is in agreement with MacPherson et al. (1958) who
equilibrated P at different pH levels with sediments from several lake
types. Maximal uptake of P occurred at pH 5.5-6.5. The CaCO buffer-
ing of Lake Mendota sediments prevents maximal sorption of P.
Lake Wingra at the lowest level of P added to Wingra pre- and post-
cultural sediment only 33 and 23 percent is sorbed, respectively, which
is about 2-3 times less sorption than observed for Mendota sediments.
The sorption and desorption of P indicate the postcultural sediment is
a less favorable sorptive and more favorable desorptive environment for
P than the precultural sediment. The opposite effect with respect to
the pre- and postcultural sediment was observed for Mendota. The
capacity of Wingra sediments for P sorption is much less than Mendota
even though the marl sediment of Mendota and the top postcultural sedi-
ment of Wingra contain approximately the same concentrations of organic
C, Fe and CO"-C. At the lowest level of added P the net sorption is 19
and 12 percent for Wingra pre- and postcultural sediment, respectively.
Monona. Profile WC-101 of Monona contains entirely postcultural
sediment. However, there are differences in the sorptive-desorptive
capacity of the 5-10 cm stratum and the 95-100 stratum due to changes
-------
162
c
o
100
90
Sediment solution: 0.400 g of WC-89 (sect. 3)
in 40 ml of solution
containing 50 ^jg P/nil .
Temperature: 23°C
Time: 16 hours
pH ad jus line nt: HC 1
o
00
VI
D
ex
CO
O
J2
On
C
C!
O
80
70
60
50
Figure 4.23
The Effect of pH on Phosphorus Sorptive Capacity for
a Lake Mendota Sediment.
-------
163
in the chemical composition of these sediment layers. The sorption and
desorption of P indicate the upper stratum is more favorable sorptive
and less favorable desorptive environment than the lower stratum. The
5-10 cm level contains more Fe, Al and K than the 95-100 cm level, but
the CO -C and organic C concentrations of the two strata are practically
equal. The net added P sorbed onto the postcultural sediments is about
the same for Monona and Mendota.
Watershed Soils. The P sorptive capacity on both watershed soil
samples is less than Monona and Mendota sediments. Phosphorus is de-
sorbed more readily in the acidic watershed soils than the alkaline
lake sediments. The pH of the watershed soil solutions range from 6.1-
6.9 compared to a pH of 8.0-8.5 for the lake sediment solutions. The
difference in P sorptive-dcsorptive capacity in woodland soil and cul-
tivated soil appears minimal. The chemical characteristics of the
watershed soils are shown in Table 4.17. The woodland soil contains
Table 4.17 Chemical Characteristics of Two Lake Mendota Watershed
Soils.
Sample
Org-C
P
Fe
Ca Mg
mo / o
K
Al
Mn
e>' e>
Woodland
Cu 1 tivated
48.3
20.0
0.88
0.87
12.2
16.9
1.2
1.8
2.3
4.0
12.2
13.7
45.7
53.6
1.35
1.32
more than twice as much organic C as the cultivated soil. The Fe, Al
and K concentrations of the watershed soils are the same order of magni-
tude as found for Mendota sediments; therefore, the large differences
in the P sorptive-desorptive capacity of lake sediments and watershed
-------
164
soils can not be accounted for by differences in Fe and Al concentra-
tions. The Ca and organic C concentrations in the watershed soils,
however, are considerably less than the Mendota sediments. It appears
that the physical and chemical composition of Lake Mendota sediments
provide a net sorptive capacity (after sorption and desorption) which
is distinctly greater than these two watershed soils.
Noncalcareous Lakes. The sorption and desorption of added in-
organic P to pre- and postcultural sediments of noncalcareous lakes is
shown in Table 4.18. The pH of the sediment-water solutions vary from
4.6-7.5. In most of the sediment layers examined, the noncalcareous
sediments sorb at least 80 percent of the P at the lowest level of
added P (5 jug P/ml). The amount of added P desorbed from the sediment
is generally less than 10 percent.
Trout Lake. The sorptive-desorptive characteristics of the 10-15
and 100-105 cm horizons of the Trout Lake core are very similar. The
Trout sediment sorbs 94 and 89 percent of the P at the lowest level of
added P (5/ig/ml) in the top and bottom samples of the core, respec-
tively. The added P desorbed ranges from 4-14 percent. The similar
sorptive-desorptive characteristics of the Trout core samples are
apparently reflected by the similar chemical composition of the two
sediments. For example, the Fe concentrations are 52.5 and 58.4 mg/g
for the top and bottom of the core, respectively.
Lake Mi nocqua. In Minocqua core WC-52, the sorption of added P
(5-50 jaP/ml) ranges from 98-67 percent in the postcultural sediment to
93-54 percent in the precultural sediment. Although the native P con-
tent is about the same in the two sediments, Fe and Al concentrations
-------
Table 4.18 Sorption and Desorption of Added Inorganic Phosphorus to Pre- and Postcultural Sediments
of Noncalcareous Lakes.
Lake
Trout
(WC-59)
Trout
(WC-59)
Minocqua
(WC-52)
Minocqua
(WC-52)
Little John
Little John
Little St.
Germain
(WC-92)
Little St.
Germain
(WC-92)
Devi Is
Devils
Depth of
Sediment
(cm)
10-15
100-105
5-10
60-65
s i rPl
_} - L U /
15-20J
170-175
5-10
80-85
0-5
90-95
Added P
Sorbed as a % of
Total Added P
( fr
5
94
89
98
93
99
49
100
100
86
52
10
90
86
96
80
98
38
100
100
70
36
25
71
65
87
63
91
25
100
100
48
22
\ J- v_
50 "
54
51
67
54
64
16
98
99
27
16
Added P Desorbed Net
as 7» of Added P ed
Sorbed Tot
>r Initial P Level (ug P/ml)
5 10 25 50 5
4 6 10 13 91
5 7 12 14 88
2256 96
3 6 10 13 90
21 . 1.5 4.8 7.6 99
25 32 36 42 38
0.1 0.1 0.2 0.4 100
0 0.5 0.1 0.2 100
7.1 13 18 25 80
11 22 30 28 47
Added P Sorb-
as % of
al Added P
10
84
80
95
75
97
29
100
100
61
28
25
63
58
83
57
87
16
100
100
40
15
50
46
44
63
47
59
9
98
98
20
12
pH pH"
After After Temper
Sorp- Desorp- ature
tion tion (°C)
5.2
5.0
5.0
5.5
6.8
6.2
4.6
5.0
6.6
6.5
5.2
5-5
5.7
5.7
7.4
7.5
4.8
5.2
6.8
6.3
28-29
29-30
27-29
23-29
28-29
-------
166
are higher in the poslcultural sediment which probably accounts for the
simultaneous increase in P sorption. Although only a small amount of
P is desorbed in both sediment types, more P is released in the pre-
cultural sediment.
Little John Lake. There is a considerable difference in the sorp-
tivc-desorptive capacity of the top and bottom samples of core WC-67.
Over 90 percent of the added PC5-25 }ig P/ml) is sorbed by the top sam-
ple (the 5-10 cm and 15-20 cm sections mixed 1:1 by weight), whereas
in the bottom section the sorption ranges from 49-25 percent for the
same levels of added P. The Fe content is 4-5 times and Mn about 3
times greater in the top than the bottom core sample. On the other
hand, organic C and Al concentrations are greater in the precultural
sediment. The dominant influence in determining the P sorptive capac-
ity appears to be the Fe and Mn concentrations.
Little St. Germain Lake, West Bay. The net sorptive capacity of
P is 98-100 percent at all levels of added P for both the bottom and
top samples of Little St. Germain. The desorption of P is less than 1
percent. The high sorptive capacity of P is attributed to the high Fe
concentration (>100 mg/g) in both sediment samples. Even though there
is high iron in both the pre- and postcultural sediment of Little St.
Germain, the native P concentration is greater in the precultural sedi-
ment.
Devils Lake. The net sorption of added P (5-50 ^aP/ml) ranges from
80-20 percent in the top sediment (0-5 cm) to 47-12 percent in the
bottom sediment (90-95 cm). The more favorable sorptive and a less
favorable desorptive environment of P in the postcultural sediment
-------
167
appears to be associated with high concentrations of Fe, Al, K, Mg and
Mn compared to the precultural sediment.
G. Aerobic Leaching of Nitrogen and Phosphorus from
Lake Mendota Pre- and Postcultural Sediment.
Core samples of Lake Mendota wet gyttja (0-30 cm) and marl (65-85
cm) were placed in 20 1 of distilled water and continuously mixed and
aerated. The wet sediments were equivalent to 65.5 g of oven dried mud
o
(105 C). The results of the aeration studies in which conductance, pH,
alkalinity, soluble P and inorganic N were followed for a maximum period
of 58 days are shown in Figure 4.24 and 4.25 for pre- and postcultural
Lake Mendota sediments, respectively. Since the sediments are mixed with
a distilled water medium, an increase in dissolved N and P would be ex-
pected as the sediment-water mixture equilibrated. However, the impor-
tant observations will be the relative amounts and rates of N and P re-
leased from the pre-and postcultural sediments.
The chemical properties of the sediment before leaching are shown
in Table 4.19. The data is typical of chemical composition for the
Mendota cores presented previously.
Table 4.19 Chemical Characteristics of Lake Mendota Pre- and Post-
cultural Sediments Used in Aerobic Leaching Study.
Sample total or§anic
C C P Fe Mn Ca Mg Al K
mg/g
Postcultural 110 86.6 1.83 19.9 1.0 93.0 16.5 45.5 9.40
gyttja
Precultural 129 81.0 0.9] 8.3 0.40 192 12.0 10.0 1.80
marl
-------
00
E
0.10
0.09
0.08
0.07
0.06
0.05
o 0.04
0.03
0.02
0.01
2.8 -
2.6
2.4
23
Vo 2.2
X
I CN
O
IS
c
0)
00
o
2.0
1.8
1.6
z
u
£ 1.4
tfl
00
S-i
o
C i ?
>-H 1 . ^
1.0
0.80
Soluble P
OO Conductance
AA
Sediment:
% Solids:
PH:
Alk. :
Temp.-:
Distilled water - 481 g:20 1
13.6
8.0 - 8.5
44 - 58 mg/1 as CaCO
23 - 31°C 3
0
12 16
40 44
48
200
190
180
170
160
150
CJ
e
o
o
140 -i
3
01
130 ^
o
120 "g
o
u
110
100
90
52 56
20 24 28 32 36
Aeration Time, days
Figure 4. 24 Aerobic Release of Inorganic Nitrogen and Soluble Phosphorus from Lake Mendota Precultural
Sediment.
-------
oo
£
1.4
1.3
I CM
§ 1.2
+
n
aa
1.1
I CO
O'
c 1.0
o>
CO
o
2:
u
H
C
(13
CO
'M
O
C
0.9
0.8
0.7
0
Sediment: distilled water - 394 g:20 1
7» Solids: 16.7
pH: 8.0 - 8.3
Alkc: 47 - 101 mg/g as CaCO
Temp.: 23 - 31°C
Soluble P
O O Conductance
A A N0~ + NH + N(T - N
I I I i I
12
16
2 0
24
48
52
56
340
320
300
o
in
CM
280
E
u
260
240
o
.a
^
u
c
220
-a
o
200
180
160
140
0.3
0.2
CO
e
0.1
O
CO
28 32 36 40 44
Aeration Time, days
Figure 4.25 Aerobic Release of Inorganic Nitrogen and Soluble Phosphorus from Lake Mendota Postcultural
Sediment.
-------
170
Leaching of Precultural Sediment. The data reported in Figure
4.24 show a general increase in soluble P (0.005-.09 mg/1) throughout
the 42 day aeration period. The initial concentration of 0.83 mg/1
N03+NH +N02-N increases to 2.3 mg/1 in 36 days. After the 24-day sam-
pling period, NO +NH +NO -N concentration appears to level off at 2.0-
2.3 mg/1. Throughout the 53 day sampling period conductance steadily
2 o
increases from 107 to 200 jamhos/cm at 25 C. Concurrently, alkalinity
increases from 44 to 58 mg/1 as CaCO (curve not shown).
Leaching of Postcultural Sediment. A general increase is observed
for soluble P, NO + NH-+NO -N and conductance during the aeration period
as shown in Figure 4.25. For the first 6 days soluble P concentration
remains at a low level of 0.004-0.009 mg P/1. From the 6-day to the
47-day sampling period soluble P concentration increases from 0.004 to
0.34 mg/1. After 47 days there is no evidence that P concentration
levels off. After the second day NO +NH +NO -N concentration fluctu-
J J ^
ates throughout the aeration period at 0.92-1.4 mg/1. Throughout the
2
56 day sampling period conductance increases from 158 to 320 ju mhos/cm
o
at 25 C. At the same time, alkalinity increases from 47-101 mg/1
CaCO (curve not shown).
3
Comparison of Pre- and Postcultural Sediment. The initial and
final concentrations of inorganic N in the supernatant water from the
marl sediment is higher than in the leachate from the gyttja sediment,
the increase in concentration of the leachate per day is twice as great
in the marl as the gyttja sediment. On the other hand, after 10 days
the soluble P concentration in the leachate from the gyttja is 2-4 times
-------
171
greater than in the marl leachate, and the increase in concentration of
P in the leachate per day is 3 times as great in the gyttja as the marl
sediment. However, the amount of P which is potentially leachable is
greater in the gyttja since the concentration of P in the starting ma-
terial is twice that of the marl. Nevertheless, the gyttja releases a
greater proportion of the total P to the water phase than the marl. A
close inspection of the release curves shows that the gyttja sediment
do not respond until 6 days to a significant release of P, whereas the
marl sediment releases P very rapidly from the 2nd day to the 6th day.
After 8-10 days the gyttja and marl sediments both released P slower
than the initial rise.
The conductance and alkalinity of the gyttja sediment supernatant
are also higher than the marl sediment throughout the aeration period.
But the leachate from the marl was always a yellow color, whereas the
leachate from the gyttja was generally colorless. Iron in the leachate
was not detectable with tht orthophenanthroline test, and Al and Mn were
not detectable with atomic absorption.
It appears that in a intensely aerated system the pre- and post-
cultural sediments of Lake Mendota are capable of releasing N and P
to the water. It is not known to what extent biological mechanisms
have influenced the release rates.
-------
172
CHAPTER V
DISCUSSION
The purpose of this chapter is to discuss these results in compari-
son with previously reported work of others and also to discuss aspects
and implications concerning the study which could not be conveniently pre-
sented in Chapter IV. The major framework of this study involves the ob-
servation and interpretation of the chemical stratigraphy of the sediments
from calcareous and noncalcareous lakes in southern and northern Wisconsin,
respectively. By comparing and contrasting the core profiles from the same
geologic and geographic regions, certain conclusions can be made concerning
chemical sedimentation in lakes, particularly in regard to the effects man
and his civilization have had on the lakes and recent lake deposits. Lake
Mendota was the principal study environment and served as the primary
source of information.
A. Distribution of Carbon
Several investigators have examined the distribution of organic C with
sediment depth in order to measure trends in historical aquatic productivity
(Mackereth, 1966; Gorham, 1961; Hutchinson and Wollack, 1940; Horie, 1966).
Often the organic C profile has been used to explain lake succession from
oligotrophic to eutrophic conditions.
To discuss the factors believed to be controlling the deposition of
organic C, a review of various possible methods of organic C deposition in
lakes is necessary. The primary factors controlling the abundance of
organic C in the sediments are 1) production of organic C of autochthonous
origin, 2) sedimentation of allochthonous organic matter, 3) destruction
-------
173
of organic material by organisms or nonbiological processes and 4) vari-
ation in deposition rate of whole sediment. It is important to remember
that the concentration and the rate of deposition of organic constituents
in sediments are the result of differences between rates of formation and
decomposition. Sediment trap studies by Kleerekoper (1953) show at least
70-90 percent of the organic matter synthesized in a column of lake water
is decomposed prior to incorporation in surface sediments. This does not
take into account further breakdown within biologically active surficial
zone of sediments. Nevertheless, Mackereth (1966) and Hutchinson and
Wollack (1940) believed that the organic matter which becomes incorpor-
ated below the biologically surface-active layers of the English Lakes
and Linsley Pond reaches a state of considerable stability towards fur-
ther oxidation shortly after burial. The lignin content of the gyttja
from several cores in Trout Lake was determined by Twenhofel et al.
(1945). They had anticipated that bacterial decomposition would have
led to a decrease in the nonligneous materials, and thus an increase in
ligneous materials with depth. Twenhofel et al. (1945) concluded that
the fact such a decrease was not observed suggested that bacterial activ-
ity ceased in the organic sediments of Trout Lake shortly after burial.
Thus, the final concentration of organic C in the sediments will prob-
ably depend primarily on factors (1), (2) and (4) mentioned above.
Calcareous Lakes. In the Mendota cores the organic C content re-
mains nearly the same in the pre- and postcultural sediment, but the
organic C concentration in the Wingra sediments decreases in the post-
cultural over the precultural sediment. In the Monona core the organic
C concentration (86-107 mg/g) in the postcultural sediment is in the
-------
174
range of the Mendota and Wingra sediments, but the core depth was not
sufficient to penetrate the precultural deposits. The observed varia-
tion in the organic C content in the cores from Wingra, Monona and
Mendota is probably best attributed to the combined influence in the
rates of carbonate C, organic C and inorganic sedimentation since the
onset of extensive agricultural and urban activities in the Lake Mendota
watershed.
Some insight into the relative importance of the sedimentation of
carbonates, organic and inorganic material may be gained from Murray's
(1956) studies on Lake Mendota. The relationship of gyttja to marl as
suggested by Murray (1956) may be considered from the three possibili-
ties: 1) the gyttja is a diagenetic precursor of the marl, 2) the gyttja
is developed by leaching of the marl and 3) the gyttja and marl are
separate sedimentary units developed under different limnologic condi-
tions. Twenhofel (1933) postulated that the black gyttja was a diagen-
etic precursor of the marl and that the process of change was one of
removal of organic matter by bacteria and precipitation of CaCO at
depth in the gyttja, thereby the gyttja was converted to marl. Twenhofel
based his conclusion that the gyttja was a preliminary product in the
production of marl on the assumption that the color of the gyttja re-
sulted from the disappearance of organic matter with depth to produce
the light marl. This study shows that the mean concentration of organic
C in the pre- and postcultural sediment is essentially constant or in-
creases slightly in the postcultural sediment of Mendota cores. Further-
more, Murray (1956) argues that it is doubtful the gyttja might have re-
sulted from alteration of the marl by removal of carbonate since the
-------
175
deeper stagnated waters would be expected to develop leaching conditions
first and thus to a greater degree retain a lower carbonate content.But
in fact, the carbonate content is greater, the deeper the water (Murray,
1956). Murray thus concluded the gyttja is simply the most recent sed-
imentary unit to be deposited in the lake. According to Murray, the
fact that the gyttja is a universal deep-water sediment resting not only
on marl but on other varied sediment types suggests that it is a unit in
itself. The abrupt change in sedimentation from marl to gyttja was ex-
plained by Murray as being the result of increasing rates of clastic and
organic matter sedimentation superimposed on a constant carbonate deposi-
tional pattern. The reported (Murray, 1956) knife-sharp nature of the
contact between gyttja and marl was not observed in any of the cores used
in this study. In all the core sections examined, the gyttja passed
gradually into the marl zone marked by a gradual lightening of color.
Apparently the false impression of a knife-sharp contact was created by
either compression of the core sections during sampling or the manner of
fractionating the core column.
An inspection of the organic C concentration profile of the Mendota
long core provides further insight into the historically changing depo-
sitional process. The organic C concentration ranges from 59 to 77
mg/g over the core interval 62-900 cm. There is no overall decrease in
the organic C content, so diagenetic transformation of the organic mat-
ter is probably not an important process. The uniformity of the marl
muds suggests that conditions were very uniform throughout the period of
its formation; this deposit appears to represent a long period of equi-
librium conditions which took place at some unknown time after the final
-------
176
disappearance of the glacial influence. Since the entire depth of the
postglacial column is not represented (glacial till not found in sub-
stratum) , an estimate of the precultural sedimentation rate is lacking.
However, the depth of the marl sediments from Cedar Bog Lake, Minn, may
provide a rough estimate of a long term sedimentation rate expected in
a hard-water lake in an edaphic region similar to Lake Mendota. Lindeman
(1941) found the postglacial marl sediments to be 12 m in the deepest
part of this hard-water eutrophic lake. If it is assumed that the depth
of the Mendota deposits is 12 m, or no more than 1.5 times this depth,
the sedimentation rate of the postglacial deposits is in the order of
1.0 to 1.5 mm/yr. This calculation is based on a date of 12,000 years
B.P. since the readvance of the Lake Michigan ice lobe (Gushing, 1967).
The estimated sedimentation rate of 1.0 to 1.5 mm/yr may be an overesti-
mation. Ogden (1967) calculated a sedimentation rate of 0.43 mm/yr for
the early postglacial period and 0.61 mm/yr for the late postglacial
period of Silver Lake, Ohio, a hard-water lake. Serruya (1969) found an
overall sedimentation rate of 0.91-1.0 mm/yr (8000 years B.P. to present)
in Lake Geneva, Switzerland, a drainage lake containing 30-40 percent
CaCO . From the organic C, percent solids and density values of the
marl sediments of the long Mendota core and the estimated sedimentation
rate of 1.0 to 1.5 mm/yr, the sedimentation intensity for organic C can
2
be calculated and is equal to 117-175 mg/cm /100 yr. This value is
3-5 times less than the postcultural deposition rate of organic C de-
posited in the center of the lake. The postcultural increase in organic
C represents both an increase in supply of autochthonous and allochthorcus
organic matter. If the bottom waters and muds have become more reducing
-------
177
since the advent of domestic drainage to the lake, the perservation of
organic matter is favored. Belcher and Fogg (1964, as quoted by
Brown, 1969) reported that eutrophy and the associated hypolimnetic de-
oxygenation were considered .as major factors in favoring the preserva-
tion of pigments in cores from Windermere and Ennerdale Water. A rapid
rate of sedimentation would also favor the preservation of organic C,
since the period of time during which the organic substance is in con-
tact with the oxygen-bearing bottom water is reduced before being
buried. Thus, a portion of the increase in organic matter in Mendota
postcultural sediments may be the result of anaerobiosis favoring pre-
servation of organic molecules and a more rapid rate of sediment accumu-
lation. However, there are some compounds, such as DDT, which only
breakdown under anaerobic conditions (G. Fred Lee, Personal Communica-
tion, 1970); therefore, the overall effects of anaerobic conditions on
the breakdown of organic compounds are not known.
The carbonate C profile of the Mendota long core indicates uniform
deposition has occurred in the geological past. The constant deposi-
tion is interrupted during the cultural period to depress the carbonate
C concentration. Calcium carbonate precipitation initiated by plank-
tonic photosynthesis or physico-chemical precipitation has probably
not decreased in recent times as inferred directly by the concentration
profile of Ca. If photosynthetic uptake of carbon dioxide is the dom-
inant mechanism for carbonate precipitation, then an increase in CaCO.,
precipitation in recent times might be slightly favored with increased
productivity. However, increased biological respiration, bacterial
activity and chemical oxidation serve to decrease CaCO precipitation.
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178
Furthermore, Megard (1969) noted that it is unlikely the productivity
during the history of lakes can be inferred from the concentration of
carbonate in the sediment because a large proportion of the carbonate
formed in the epilimnion of productive lakes is dissolved in deep
water during periods of stratification. It appears that the most likely
/
explanation for the postcultural decrease in carbonate C concentration
is the masking of a somewhat constant (or increasing) carbonate deposi-
tion by the increased inorganic sedimentation.
The net effect of the cultural activities in the Mendota basin has
been to produce an increase in organic C and inorganic materials in
somewhat the same proportion. An increase in inorganic sedimentation is
evidenced by the increase in Fe, Mn, K, Al and P in the upper sediments.
If the organic C sedimentation rate was not high, it would be reflected
as a decrease in the concentration depth diagram the same as CaCO . The
postcultural sedimentation intensity for organic C is 1.6 and 3.2 times
greater in University Bay cores WC-86 and WC-84, respectively, than in
the deep-water core. The high organic C deposition rate in University
Bay is attributed to the proximity of University Creek inlet and the
high production of aquatic weeds in the shallow area of the lake. Both
of these sources undoubtedly supply allo- and autochthonous organic
detritus to the lake. The postcultural sedimentation intensity of
organic C in Wingra and Monona is 2.2 times greater than the deep area
of Mendota. If the supply of allochthonous organic matter is the same
for Mendota and Monona, the higher organic C deposition rate could also
be a reflection of the smaller Monona bottom area as well as a greater
internal production of organic matter. The evidence would seem to
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179
indicate internal production of organic C is quite high in Wingra since
the lake does not receive agricultural runoff which would probably con-
tribute heavily to the allochthonous organic C fraction.
Noncalcareous Lakes. The postcultural intensity of organic C
2
varies from 159 to 514 mg/cm 7100 yr which is lower than the calcareous
2
lakes (526-1184 mg/cm /100 yr). However, the concentration of organic
C is much greater in the noncalcareous lakes. The highest organic C
deposition rate is observed for Little John, a shallow, spring-fed, eu-
trophic lake, and the lowest organic C deposition rate is shown in the
northwest bay of Minocqua, a eutrophic drainage .lake. Thus, there is
not necessarily any relationship between the productivity classification
of a lake and the absolute amount and rate of accumulation or organic C
in the postcultural sediments.
In all of the noncalcareous lake cores examined with the exception
of South Bay of Little St. Germain, the highest organic C content occurs
in the precultural sediments and decreases upward in the postcultural
sediment. Often the decline of organic C concentration is contempor-
aneous with the rise in the ragweed pollen. The decrease in organic C
is usually accompanied by an increase in Fe and Mn and/or Al, K, Ca and
Mg concentration. Both K and Al are associated with the mineral fraction
of the sediment. Hackereth (1966) demonstrated the near linearity of
the relationship between the mineral content of the sediment and the
Na-K concentration. The concentration of Al and K (and other associated
elements) in the sediment may be regarded as being directly proportional
to the intensity of erosion. If the rate of organic C deposition remains
constant and the rate of inorganic sedimentation increases, the
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180
percentage of organic C will decrease. The cores from South and West
Bay of Little St. Germain, the southwest bay of Minocqua and Devils show
clear evidence of increased Al, K, Mg and Ca concentration in the post-
cultural over the precultural sediment concurrent to the decline in
organic C concentration. A close inspection of the Weber Lake core se-
quence reveals that Fe, Al, K and Mg show the same inflections (a mini-
j
mum and maximum peaks) and form a mirror image to organic C. If it is
assumed the biological productivity of oligotrophic Weber Lake has not
increased or decreased throughout its history as represented by 1 m of
sediment, the changes in the organic C profile are then inversely pro-
portional to the inorganic sedimentation rate.
Hutchinson and Wollack (1940) observed in Linsley Pond a consider-
able decrease in organic and an increase in inorganic content in the
most recent unconsolidated sediment at the top of the profile, as com-
pared to the levels immediately below. It was assumed by Hutchinson and
Wollack that the organic production in the lake remained constant, but
the rate of silting of the present mud was 2.6 times that occurring be-
fore the human agency became prevalent in the 18th century. Similarly,
a drastic reduction in the percentage of organic matter occurred in the
upper 20 cm of a core from Potato Lake, Arizona(Whiteside, 1965).
Whiteside (1965) explained that the transport of inorganic materials and
i-ts deposition in the upper sediments were increased due to logging and
grazing activities in the lake basin. The lacustrine record of Ennerdale,
Windermere and Esthwaite, England show either insignificant change or an
increase in organic matter concentration near the tops of cores repre-
senting deposits following the development of a fairly dense human
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181
settlement on the lake shores (Mackereth, 1966; Pennington, 1943). In
Lake Washington, near Settle, Edmondson (1969) observed that the organic
matter characteristically increases in the top 15 cm (representing
approximately 40-50 years). Although the concentration of organic
matter varied in Lake Washington within different parts of the lake.
Edmondson felt in general either the lake laid down richer organic sed-
iments or else decomposition was less during the era 1916 to 1958 than
before.
In South Trout, North Trout, West Bay of Little St. Germain,
in the northwest bay of Minocqua, Weber and Devils the organic C shows
a slight upward decrease before the postcultural period is initiated. It
appears that either a general increase in inorganic sedimentation rate
or a decrease in production of organic matter has occurred before the
major cultural influence from deforestation in the above named lakes.
The decline in organic C near the tops of the cores is often rapid, but
the influences causing the change in the physical and chemical environ-
ment before the cultural period are exemplified by gradual decrease in
organic C, perhaps indicating a climate episode. There is evidence of
a cold climate, "little ice age", during the period 1430-1850 A.D. (Lamb,
1963). A climate change may have influenced rates of erosion or lowered
the organic production in the lake prior to 1850 assuming the average
temperature of the water to be colder and the water levels higher than
post 1850. It seems unlikely, however, that mean temperature departures
from present-day conditions were sufficient enough during this epoch to
produce a detectable difference in organic C production in these lakes.
If the decline in organic C is accompanied by an increase in Fe and Mn
-------
182
and/or Al, K, Mg and Ca, the mechanism causing the decrease in organic
C before the cultural period is probably an increase in inorganic sedi-
mentation.
In summary, it appears that the organic C concentration depth pro-
files have been modified by cultural activities in the noncalcareous
lakes. This is marked almost always by a trend towards decreasing con-
centrations of organic C in the postcultural column. The primary con-
trolling factor in determining the final organic C concentration appears
to be the rate at which the sediment as a whole is deposited. The rate
of sedimentation appears to be inversely proportional to the organic C
content.
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183
B. Distribution of Nitrogen
Organic N determined by the Kjeldahl method was performed on cores
from lakes Mendota (WC-89), Wingra (WC-92) and Trout (WC-59). The dis-
tribution range of organic N is 5.7-10.0 mg/g, 6.6-10.6 mg/g and 13.8-
18.4 mg/g for Mendota, Wingra and Trout cores, respectively. In soils
and lake sediments organic N is the dominant form usually ranging from
95 to 98 percent of the total N (Bremner, 1965; Keeney et al., 1970) and
is a function of the amount of particulate organic matter deposited
(Bortleson, 1968). After deposition, the organic N-containing compounds
are modified by biological agents, chiefly bacteria, with the liberation
of part of the N in soluble forms. One of the most striking features of
the data is the close association between organic C and organic N curves;
in the three cores examined, almost every irregularity in the former is
reflected in the latter. Since organic C and organic N concentrations
show considerable association, the conclusions that were reached con-
cerning organic C depth profile patterns would also apply to organic N
distribution. Therefore, it would seem that there is little or no
relationship between the productivity classification of a lake and the
sedimentary concentration or intensity of organic N. However, Keeney et
al. (1970) pointed out from their sampling of northern Wisconsin lakes,
that the organic N content of sediments from eutrophic soft-water lakes
was much higher than from those lakes of lower fertility.
Carbon-Nitrogen Ratio. The organic C to organic N ratio with depth
of sediment for the three cores examined is shown in Table 5.1. The C/N
ratio fluctuates somewhat with depth of sediment in each of the cores;
in the Trout Lake core there is a trend of increasing C/N ratio with
-------
184
Table 5.1 Organic Carbon to Organic Nitrogen Weight Ratio for
Lakes Mendota, Wingra and Trout Cores.
Depth of
Sediment
(cm)
0-5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
80-85
85-90
90-95
95-100
100-105
C/N (mean)
Mendota
(WC-89)
C/N
7,38
8.85
8.80
8.32
9.69
8.89
8.68
7.22
8.61
7.90
9.98
9.63
11.4
8.00
6.70
7.95
8.07
8.51
8.50
8.55
Trout, S.
(WC-59)
C/N
8.85
9.36
9.02
10.2
10.1
10.2
10.6
10.4
10.6
10.3
10.6
10.7
10.7
11.4
11.4
11.6
11.3
11.8
11.1
11.2
10.3
10.5
Wingra
(WC-92)
C/N
8.56
9.04
9.95
9.56
9.05
7.82
8.19
8.65
9.95
9.85
8.46
9.37
8.36
8.50
8.68
8.07
7.90
8.34
_ _
--
--
8.79
-------
185
increasing depth. In lakes Mendota, Wingra and Trout, respectively, the
mean C/N ratio for the entire core is 8.55, 8.79 and 10.5. It is noticed
that the average C/N ratio is smaller for the two hard-water eutrophic
lakes than Trout Lake. The C./N ratio in these sediments is considerably
higher than the C/N ratio of approximately 5.7 for plankton (Emery and
Rittenberg, 1952), so the organic material must undergo much decomposi-
tion releasing N faster than C as it settles through the water column
and shortly after it reaches bottom. The increase in the C/N ratio with
depth in the Trout core indicates further decomposition of N-containing
compounds with aging. The smaller C/N ratio in. the top 15 cm of the
Trout core may indicate the full mineralization and stabilization of the
organic matter has not developed. Arrhenius (1950) presented results in-
dicating that C/N decomposition conditions are influenced also by the
dilution of organic matter with mineral matter in such a way that a high
dilution will favor a preservation of organic matter in its nitrogen
rich state. This may partially account for the low C/N ratio in the
calcareous lakes where the sediment accumulation (based on dry weight)
is much greater than Trout Lake. According to soils literature, under
ordinary circumstances when the C/N ratio of soils is low, the supply
of readily available energy material is limited, resulting in slow min-
eralization of nitrogen (Stevenson, 1964). Such an arrangement is ad-
vantageous in that the main N reserves of soil are held in an insoluble
form which cannot be leached away but which can be slowly mineralized
to support plant growth (Stevenson, 1964). The mineralization of N from
fresh organic residues is dependent on a number of physical and chemical
conditions of the soil. For example, according to Stevenson (1964) the
-------
186
adsorption of organic N compounds, particularly proteins on clay col-
loids, has a distinctively protective effect. Based on the foregoing
comments, the implication may be that Mendota and Wingra sediments con-
tain greater N reserves heldtin an insoluble form which cannot be
readily leached. Juday et al. (1941) have analyzed bottom deposits of
/
21 Wisconsin lakes for organic C and organic N, and the magnitude of
C/N ratio appears to be independent of lake types. The C/N ratios of
lake sediments found by Juday et al. (1941) range from 7.5 to 14.1. The
average C/N ratio of agriculturally important surface soils is approxi-
mately 11 (Mortensen and Himes, 1964).
Exchangeable Ammonium Nitrogen. In Table 5.2 is shown the concen-
+
tration range and mean concentration for exchangeable NH.-N in the pre-
and postcultural sediments of the four cores examined. The concentration
of exchangeable NH/-N generally increases with sediment depth for lakes
Wingra, Monona and Trout, but decreases slightly for Mendota. The general
+
increase in exchangeable NK -N with depth may indicate that organic ma-
terials are undergoing decomposition throughout most of the depth sam-
+
pled. The NH -N released could be contained in the interstitial waters
4
or incorporated in the adsorbing complex as exchangeable ammonium.
Emery and Rittenberg (1952) observed from California Basin sediments
that ammonia increased in the interstitial waters with sediment depth
which was correlated with greater decomposition of organic matter with
depth. The maximum rate of aiimonia production is probably at or near.
the surface, but if oxidizing conditions exist in the surface layers,
the nitrifying bacteria can convert the ammonia to nitrate. The low
ammonia concentration observed in the upper layers is, then, the
-------
187
Table 5.2 Exchangeable Ammonium Concentrations in the Pre- and
Postcultural Sediments of Lakes Mendota, Monona, Wingra
and Trout.
Lake
Precultural
range mean
NH-N (mg/g)
PostcuItural
range mean
NH-N (mg/g)
4
Mendota 0.34-0.49 0.41
(WC-89)
Monona
(WC- 101)
Wingra 0.20-0.23 0.22
Trout, S. 0.24-0.34 0.29
(WC-59)
0
0
0
0
.41-0
.20-0
.048-
.16-0
.54
.96
0.22
.26
0.49
0.74
0. 14
0.22
difference between that oxidized by the nitrifying organisms and that
formed in and brought into the layer from below. The increase in ex-
+
changeable NH-N with depth may also be due to the higher concentra-
tions of organic N which can be mineralized residing at lower sediment
depths. This may be especially true for lakes Wingra and Trout, since
organic N generally increases with sediment depth. The correlation be
+
tween organic N and exchangeable NH-N may best explain the rather
+
uniform concentration of NH -N with depth of sediment for Mendota.
4
Keeney et al. (1970) reported 0.185, 0.127, 0.032 and 0.179 mg/g
exchangeable ammonium N for the surface sediments of lakes Mendota,
Monona, Wingra and Trout, respectively. All of these values with the
+ +
exception of NH.-N for Trout Lake are below the exchangeable NH -N con
tent found in this study. In general, Keeney et al. (1970) found the
+
soft-water sediments possessed greater amounts of exchangeable NH-N
than hard-water lakes. This was attributed to the higher exchange
-------
188
capacity of the amorphous northern lake sediments. However, the higher
exchangeable NH -N concentration of the northern lakes could also be
attributed to the higher concentrations of original organic matter
which can be mineralized.
Inorganic Nitrogen Released from Lake Mendota Sediments. The pre-
and postcultural sediments of Mendota release increasing amounts of NO +
NH +NO -N throughout the 50 day aerobic incubation period. As shown in
Table 5.3 the release rate of inorganic N is 0.022 mg/I/day and 0.0098
mg/I/day for the pre- and postcultural sediments, respectively.Although
both the pre- and postcultural sediments of Lake Mendota release inor-
ganic N aerobically, the release rate of NO +NH_+NO,-N on a mg/I/day
basis is 2.2 times faster in the marl sediment, but the amount of inor-
ganic N released per gram of sediment N is only 1.6 times greater in
the marl than the gyttja. The hydrol^able organic N released as NO +
NH +NO -N for the gyttja and marl si.di ent at the end of the aeration
period is 5.3 and 8.2 percent, respectively. This calculation assumes
80 percent of the total organic N is hydrolyzable (Keeney et al., 1970)
and the organic C/organic N ratio is 8.55. The organic C concentration
(organic N determined by mean C/N ratio from Mendota core WC-89) in the
starting material for the two sediment types is approximately equal.
The initial inorganic N form produced by bacterial decomposition
of organic material is ammonia. Under certain conditions, a-nmonia is
converted to nitrite and then to nitrate by specific groups of bacteria.
Austin (1970) found that nitrate N was the dominant inorganic form re-
leased from well-mixed aerobic incubation studies of Lake Mendota muds.
After 170-200 days the ammonia concentration was practically reduced to
zero (Austin, 1970). 'Austin (1970) reported higher values than this
-------
Table 5.3 Inorganic Nitrogen (N0~ + NH + NOT - N) Released from Lake Mendota Pre- and Postcultural
Sediments . 3 3
*
Sediment Sed. in Organic N Percent Hydrolyzable Rates of Release of N0_ + NH, + N02 - N
Suspension in Sed. Organic N Released as
(g/1) (mg/g) NO" + NH + NO" - N (mg N/l/da) (mg N/g sed./da) (mg N/g sed. N/da)
Post- 3.29 10.1 5.30 0.0098 7.7 x 10"3 9.5 x 10"
cultural (8.10) (2-58 da)
Pre- 3.28 9.46 8.22 0.022 1.2 x 10"2 1.55
cultural (7.55) (1-53 da)
* Numbers in parenthesis used in calculation of release rates; assumes 80 percent of organic N hydrolyzable
N (see Keeney et al., 1970)
i
00
vo
-------
190
study for the rate of aerobic release of inorganic N (0.09 mg/I/day)
and the percent of hydrolyzable N released as inorganic N (20.7 per-
cent in 60 days) from Mendota gyttja. The conditions for the two
studies were essentially the same; however, Austin used different ana-
lytical procedures for the determination of inorganic N forms. Mortimer
(1941) noted a fall in alkalinity, nitrate and ammonia concentrations
in an aerated artificial mud-water system. The laboratory conditions
of Mortimer's studies were different than this or Austin's (1970) study.
Mortimer allowed a surface brown "oxidized layer" to form on the muds
before beginning the study and then kept the mud-water system quiescent,
the temperature at 14-20 C and exposed to the light. The small change
in dissolved substances in the aerated tanks was explained by Mortimer
as due to the strongly adsorbent properties of the oxidized surface
layers for bases such as ammonia. Sawyer (1944) also conducted an
aerobic quiescent N release study on Mendota mud and found approximately
-4
3.7 x 10 mg N/g sed/day (making assumption that solids content in 1 liter
of mud from Sawyer's study was 20 percent). This is considerably less
N release than found in this study. Sawyer does not comment on the N
forms analyzed. In an aerobic N release study on uncultivated marsh
soils (Shakey Marsh, Wis.), Bentley (1969) found a release of NO -N of
0.0165 mg/l/day. This value is slightly greater than the release of in-
organic N obtained for the Mendota postcultural sediment but slightly
less than the precultural sediment.
It would appear historically the sediment potential for the aerobic
release of inorganic N was similar to (or greater than) the postcultural
period. Although the release rates of inorganic N shown in this study
-------
191
represent maximum release conditions, it seems that laboratory condi-
tions might be correlated with mixed bottom muds from shallow bay
areas in the summertime.
-------
192
C. Distribution of Phosphorus
Total P analysis was performed on all cores investigated and acid
soluble P was determined on Mendota cores WC-89 and WC-86, Wingra core
WC-92, and Trout core WC-59. To discuss the factors believed to be
controlling the deposition of P, a review of the various possible
modes of P deposition in lakes is desirable. The migration and precip-
itation of P into the bottom muds may take place both by P incorporation
into plant and animal remains and by sorption or precipitation with in-
organic components. The final concentration of P residing in the sedi-
ment depends primarily on 1) the rates of supply of P in the form of
inorganic and organic P from inflowing waters 2) the efficiency at
which P is precipitated or sorbed with other chemical components such
as Ca, Al, Fe and Mn or sorbed onto particulate matter and carried in-
to the sediment, 3) the retentive capacity of the sediments for P and
4) the rate of accumulation of the whole sediment. Some insight is
given as to the importance of these factors in the sedimentation of P
in calcareous and noncalcareous lakes. The last factor mentioned will
not be discussed explicitly because it is understood from the previous
discussion of the role of this variable in the interpretation of a con-
centration-depth diagram.
Calcareous Lakes. In lakes Mendota and Monona the P concentration
increases in the postcultural over the precultural sediment; in Wingra
the mean P concentration of the pre- and postcultural sediments is
approximately the same.
Any of the observed increases in the concentration of sorbed or
precipitated P in the sediment could be attributed to an increase in
-------
193
the supply of P to the waters of a particular lake basin. The enrich-
ment of P in the postcultural sediments of Mendota is of particular
interest because the long core (9.9 m) provides a background concen-
tration of P that was deposited for a long period historically. The
interval from 990 to 62 cm presents the time prior to settlement
period in southern Wisconsin. During this time the concentration of
P, Fe, Mn, Al, K, Ca and ragweed pollen are all relatively constant
indicating long stable conditions existed in Mendota and its water-
shed. It probably can be assumed that all four factors mentioned in
controlling the distribution of P maintain a relatively constant ratio
to each other during this period. The chemical homogeneity of the
sediments is interrupted near the transition zone from high to low car-
bonates, whereby the components mentioned above are enriched in the
postcultural sediments. Phosphorus increases in concentration by
approximately 2-fold in the upper black gyttja. The sedimentation in-
2
tensity of P is estimated at 11.9 mg P/cra 7100 yr in the center of the
lake. The estimated precultural P deposition rate is 1.5 to 2.2 mg
2
P/cm /100 yr which is 5 to 8 times less than the postcultural deposi-
tion rate in the center of the lake. As a comparison, the post-
cultural sedimentation intensity of P for Monona and Wingra is 19.2
2
and 8.9 mg P/cm /100 yr, respectively. The deposition rate of P in
Wingra sediments is low in spite of the high sedimentation rate in the
Wingra basin. Wingra receives primarily urban runoff, but Mendota and
Monona receive a combination of urban and agricultural runoff plus
municipal sewage discharges. The accumulation rate of P in the sedi-
ments of Monona compare very well with that found by Ahlgren (1967) for
-------
194
Lake Norrviken, a eutrophicated Swedish lake. From a water balance and
2
P budget data, Ahlgren calculated a P deposition rate of 19.8 mg/cm 7100
yr.
Another interacting variable controlling the final concentration of
P in the sediments is the efficiency at which P is precipitated or
sorbed with other chemical constituents. In lakes Mendota and Monona
the P enrichment is concomitant with an increase in K, Fe, Mn and Al.
These elements with exception of P are also enriched in the post-
cultural sediments of Wingra. An increased influx of Fe and Mn hydrous
oxides, clay minerals and oxides and hydroxides of Al from domestic
drainage of urban and rural areas probably provides for increased
efficiency for P precipitation. Phosphorus may be taken from solution
by precipitated ferric and aluminum hydroxides or clay minerals (Carritt
and Goodgal, 1954; Hsu, 1965). In general, high P sorption by clays
is favored by a lower pH. A pH above 7 does not favor a strong fixa-
tion of P on clay minerals (Carritt and Goodall, 1954), but exchange
reactions between P and mineral constituents might occur, or being
accumulated on the surface, the P might move into the voids in the
structure of solids (Carritt and Goodall, 1954). An eroded colloidal
soil, low in P, might remove considerable amounts of P from the water
before final deposition. Wang and Brabec (1969) have shown
that the turbidity in Illinois River water was related to
particulate P, particulate Si and particulate Fe (III). With the in-
crease in runoff waters since the advent of agricultural practices in
the Mendota watershed, a particulate P-Fe-Si complex associated with
clay minerals similar to that proposed by Wang and Brabec may well have
-------
195
contributed to the P deposition increase since the cultural period.
The mode of P deposition which is favored in the calcareous lake system
is sorption or precipitation with CaCO (Frink, 1969; Wentz and Lee,
3
1969b). At low concentrations of P (lake water), sorption on CaCO is
3
favored over precipitation (Cole et al., 1953). Also Al-P and Fe-P
carried from the acidic watershed soils can be transformed to Ca-P
upon residence in a neutral or basic lake environment (Frink, 1969).
Wentz and Lee (1969b) found about one-half of total P is associated
with the carbonate portion of the sediment in Lake Mendota. They con-
cluded that the rate of increasing available (acid soluble) P deposi-
tion resulted from sorption onto clastic material or carbonate and
that the above mechanism of P deposition required an increase in P
concentration in the lake (Wentz and Lee, 1969b). This, they felt,
was probably sustained by an increasing P influx due to urbanization.
The acid soluble P extracted with 1 N HC1-H SO on Mendota core WC-86
2 4
and Wingra WC-92 indicates the postcultural sediment contains the
greater proportion of the total P which is not acid extractable. The
strong acid treatment extracts Ca-bound P and non-occluded P. The
non-occluded P includes P associated with Fe hydrous oxides and Al
hydroxides and oxides precipitated or sorbed on the sediment particles,
but 1 N acid probably would not extract organic P or occluded forms of
Fe-P and Al-P (Shah et al., 1968). Thus, the more recent muds contain
more P which is refractory or not readily exchangeable to the overlying
water, whereas the marl sediments contain primarily Ca-bound P with a
smaller proportion of the total P present as nonexchangeable P.
Williams et al. (1970) reported values indicating that 26 percent of
-------
196
the total P is organic P in Mendota and Monona surface muds, and about
38 percent is organic P in Wingra surface sediments.
The final concentration of P that resides in the sediment is also
dependent on the P sorptive and retentive capacity of the sediment.
The aerobic sorption and desorption studies of P indicate the post-
cultural gyttja is a more favorable sorptive and less favorable de-
sorptive environment for P than the precultural marl in Lake Mendota.
The higher concentration of Fe, Mn, Al, and K in the postcultural sedi-
ments than in the marl deposits probably accounts for the greater P
binding capacity. Thus, it appears that for a long period historically
the marl sediment was less capable of sorbing and retaining P, but
in recent lake history the muds are more capable of sorbing and re-
taining P which may be added to the lake. If the P retentive capacity
of the postcultural vs. the precultural muds were the sole influence
in controlling P availability to aquatic plant growth, the lake would
be in a phase of decreasing productivity. Livingstone and Boykin
(1962) noted that the productivity in a lake could be inversely propor-
tional to the sorptivt1 capacity of the mud. They found the P content
was highest in the deeper-lying samples of the sedimentary column of
Linsley Pond, which formed during oligotrophic stage in the lakes
history. In such a case, the P that had not been released from the
mud during the early history of the lake would still be trapped in the
sediment. The opposite trends that Livingstone and Boykin described
take place in Lake Mendota. Presumably, the lake was less productive
at the time of marl deposition, but the sorptive capacity and the P
content is less in the marl sediment.
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197
Wingra pre- and postcultural sediments sorb about 2-3 times less P
than Mendota. In Wingra the sorption and desorption of P indicate the
postcultural sediment is a less favorable sorptive and more favorable
desorptive environment for P than the precultural sediment. Both of
the above observations may partially account for low concentration of
P in Wingra sediments compared to Mendota as well as the P profile for
Wingra, which is rather uniform with depth. Since the P binding capac-
ity in the Wingra postcultural sediments is low, the P accumulation
is also low in the postcultural sediment. It appears that low Fe (8-
9 mg/g) and high CaCO (56-62 percent) content of the Wingra post-
cultural sediments accounts for the low P sorptive and high desorptive
capacity, but apparently, the precultural marl containing a higher per-
centage of CaCO (68-80 percent) enhances the sorption and reduces de-
3
sorption of P. Nevertheless, the CaCO and Fe content do not explain
3
the sorptive-desorptive behavior of P completely, because the capacity
of Wingra sediments for P sorption is much less than Mendota even
though the marl sediment of Mendota and the top sediment of Wingra con-
tain approximately the same concentrations of organic C, Fe, and CaCO .
The difference in the Wingra postcultural and Mendota precultural sed-
iment P sorptive-desorptive capacity may be due to physical character-
istics as well, i.e. particle size differences. Any addition of P to
Lake Wingra would be less capable of fixation by the recent muds than
muds laid down preculturally.
Even though the sorptive-desorptive characteristics of Mendota
postcultural muds favor an accumulation of P compared to the marl, the
aerobic leaching studies on the pre- and postcultural Mendota sediments
-------
198
indicate a slightly greater release of P from the gyttja in an aerobic
well-mixed system as shown in Table 5.4. The dissolved inorganic P re-
leased from Mendota pre- and postcultural sediments is 0.73 and 1.2 mg
P/g sediment P/day, respectively. The P release data from this study
agrees well with that of Spear (1970) who found that the surface sedi-
ment of Lake Mendota in an oxic system released 1.6 mg P/g sediment
P/day (average) compared to 1.2 mg P/g sediment P/day observed in this
study. The release rate of P based on a mg/l/day basis is about 3 times
faster for the gyttja sediment, but the amount of P released per gram
of sediment P is only 1.6 times greater in the gyttja than the marl. If
the Lake Mendota muds became more reducing in the postcultural period
as evidenced by the black coloration due to ferrous sulfides (Murray,
1956; Nriagu, 1967-68), the greater regeneration of P into the water
phase may be expected under bottom anoxia conditions. Spear (1970)
showed that about 5-12 times more P is released in Mendota surface sed-
iments under anoxic (in 10 days) than oxic conditions (in 50 days). It
is not known whether reducing conditions of the bottom muds would have
an effect on the net loss of P from the sediments in a stratified lake
on an annual basis.
The change in concentration and deposition rate of P in a horizon-
tal direction in pre- and postcultural sediments from the deep-water
area towards University Bay of Lake Mendota is depicted in Figure 5.1.
The comparative values for deposition rate and concentration of P at the
different core locations are calculated from a value of unity for the
Mendota postcultural P concentration and deposition rate. The net
effect of the cultural influence on the Mendota deep-water core profile
-------
Table 5.4 Dissolved Inorganic Phosphorus Released from Lake Mendota Pre- and Postcultural Sediments.
Sediment
P in
Sed.
Percent Sed.
P Released as
Rates of Release
Sed. in
Suspension
(g/1) (mg/g) Dissolved P (mg P/l/da.) (mg P/g sed./da.) (mg P/g sed. P/da.)
Postcultural 3.29
Precultural 3.28
1.83
0.91
5.63
3.04
6.2'x 10"3
2.2 x 10
-3
2.2 x 10
6.6 x 10
-3
1.19
0.73
-------
Univ. Bay
WC-82 (4 m)
Univ. Bay
WC-84 (12 m)
Univ. Bay
WC-86 (18 m)
Deep Hole
WC-89 (23 m)
cone. = concentration (+)
sed. int. = sedimentation intensity (#)
+ & # = unity in deep-water of Mendota
postcultural sediments
= ragweed boundary
conc.=
sed.
int.
0.59 +
0.13-0.18#
Figure 5.1 Phosphorus Concentration and Sedimentation Intensity in Gyttja and Marl Sediments of
University Bay and the Deep-water Area of Lake Mendota.
NJ
o
o
-------
201
is to produce a 2-fold change in P concentration in the gyttja sediment
over the marl. The concentration of P in the marl is fairly uniform
horizontally, but in the postcultural sediments the P concentration in-
creases towards the center of the lake. The sedimentation of P in the
center of the lake is probably associated with the finer sediment frac-
tion. Based on surface sampling of 32 stations in Lake Mendota, P, Fe
and Mn concentrations show a positive statistical correlation with
sample depth (Delfino et al., 1969); a linear correlation coefficient
of 0.82, 0.74 and 0.81 was found for P, Fe and Mn, respectively. Frink
(1969) found in eutrophic Bantam Lake, Connecticut, that the center of
the lake is enriched in clay, organic matter, and P when compared with
the sediments around the edge. The Fe-P and Al-P fractions were always
highest in the finer fractions towards the center of the lake, but Ca-P
decreased with increasing water depth in Bantam Lake and was associated
with the coarser fraction (Frink, 1969).
Nevertheless, the actual rate of P sedimentation increases toward
the shallow water of University Bay where the deposition rate of the
whole sediment increases as shown by the increasing depth of the rag-
weed boundary and the increasing dry solids accumulation. The depth of
the wet sediment thickness of the black gyttja increases with'water
depth, but the sediments contain less dry solids (see Figure 4.1).
Apparently, in the center of the lake the black gyttja was laid down
prior to major cultural influence as shown by the depth of the ragweed
profile.
Noncalcareous Lakes. The P profiles from a wide range of noncal-
careous lakes indicate that concentration of P in the underlying older
-------
202
sediments is less in relation to the postcultural sediments in most of
the cores examined (see Table 4.9). Nevertheless, in both West and
South Bay of Little St. Germain the P concentration decreases in the
upper postcultural deposits, and in the southwest bay of Minocqua and
Weber the mean P concentration in the pre- and postcultural sediments
remains unchanged. In eutrophic Minocqua and Little St. Germain lakes
in which the P is not enriched in the upper sediment, the concentrations
of Al, K, Mg and Ca increase in both the lakes usually by over 50 per-
cent in the postcultural over the precultural sediment. Thus, it
appears that rapid erosion due to the activities of man in the basin of
these drainage lakes caused an increase in the rate of inorganic diluent
resulting in a concomitant decrease in P concentration. As mentioned
previously, the general increase in inorganic sedimentation in the
northern Wisconsin region followed the period of deforestation. The
2
high sedimentation intensity of 14.7 and 20.5 mg P/cm /100 yr in the
southwest bay of Minocqua and West Bay of Little St. Germain, respectively,
is further evidence that the supply rate or depositional efficiency of
P in these two lakes has probably not decreased in recent times. These
values for sedimentation intensity of P are the highest found for the
noncalcareous lakes. As a comparison, the deposition rate of P men-
tioned above in the southwest bay of Minocqua and West Bay of Little St.
Germain are in the same range as the deposition rate of P in Monona and
2
University Bay of Mendota (14.0-19.2 mg P/cm /100 yr).
In nearly all the noncalcareous lakes examined, P, Fe and Mn con-
centration profiles are closely related both in the pre- and postcul-
tural sediments. It must be assumed that a very important part is
-------
203
played by both Fe and Mn compounds, not only in precipitation of P to
the sediment but also in its retention therein. Several investigators
have emphasized the significance of Fe and its hydrous oxides to the
precipitation and sorption of P (Mortimer, 1942; MacPherson et al.,
1958; Jitts, 1959); fewer investigators have emphasized the role of Mn
as a sorptive complex for P fixation (Mackereth, 1966). The Fe com-
pounds undoubtedly play a more dominant role than Mn because the average
lithospheric concentration is 50 mg/g Fe to 1 mg/g Mn (Rankama and
Sahama, 1949). Morgan and Stumm (1964) discussed the transformations
of Fe and Mn that are important to the geochemistry of lake waters. An
oxidized low pH environment would favor the binding of P, and a reduced
high pH environment would favor the release of P and colloidal stability
of Fe and Mn compounds. Spear (1970) demonstrated that increasing the
pH of the low pH Trout Lake sediments with NaCO or CaCO caused a sig-
nificant increase in P released under oxic conditions. Mackereth (1966)
attributed the maximum concentrations of P in Windermere and Esthwaite
to the high efficiency of coprecipitation of P with Fe and Mn compounds.
The results from this study on noncalcareous Wisconsin lakes would agree
with Mackereth1s observation. Invariably high or low Fe and Mn concen-
trations in the core profiles are concomitant with high and low P. This
is the case whether the sediments are of pre- or postcultural origin, so
the mechanism does not appear to have changed with the modifying activity
of man in the watershed. However, Mackereth (1966) observed that in
oligotrophic Ennerdale the Fe and P profiles were separated, and he con-
cluded that P deposition was not influenced by variations in Fe and Mn,
but the precipitation of P was largely biological and constant. Only in
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204
oligotrophic Weber Lake are the Fe, Mn and P concentration profiles not
related. This is the case whether the sediments are pre- and postcul-
tural origin, so the artificial additions of fertilizers to Weber Lake
have not affected the observation. The concentration of Fe and Mn in
both Weber Lake pre- and postcultural sediment is the lowest found in
the noncalcareous lakes examined. The Fe profile of Weber Lake
parallels that of Al, K and Mg indicating that the Fe is probably
associated primarily with clay minerals which would provide little
opportunity for P precipitation with Fe. The close relationship be-
tween the sedimentation intensity of P, Fe and Mn in the postcultural
sediments of the noncalcareous lakes is shown in Table 5.5. In
West Bay of Little St. Germain, southwest bay of Minocqua and
the North and South Trout show the highest postcultural sedimenta-
tion intensity for P, Fe and MnJ in Devils Lake and Weber Lake, Fe,
Mn and P deposition rate is lowest. It is also noticed that a high P
sedimentation intensity is not necessarily correlated to the productivity
classification of a lake. For example, the P sedimentation intensity
for North and South Trout Lake is high, but the lakes are oligotrophic-
mesotrophic.
The final concentration of P which resides in the noncalcareous
sediments is also dependent on the sorptive-desorptive capacity of the
sediments for P. In Table 5.6 is shown the net P retentive capacity
(after sorption and desorption steps) of the pre- and postcultural sed-
iments compared to some chemical characteristics of the sediments. The
lakes are arranged in the order of their decreasing P retentive capacity
in-the postcultural sediments. This order (with the exception of
-------
205
Table 5.5 Relationship Between Phosphorus, Iron and Manganese Sedimen-
tation Intensity in Noncalcareous Lakes.
Lake
Productivity
Classification
Postcultural Sedimen-
tation Intensity
: r\
1 (mg/cm /100 yr)
Fe
Mn
Little St. Germain, W. eutrophic
Minocqua, S.W.
Trout, S.
Trout, N.
Minocqua, N.W.
Little John
Devils
eutrophic
20.5 207 2.95
14.7 118 3.20
mesotrophic-oligotrophic 12.6 129 6.21
mesotrophic-oligotrophic 11.6 106 A.75
eutrophic
eutrophic-mesotrophic
5-75 49.8 0.664
5.59 80.0 1.23
mesotrophic-oligotrophic 4.06 83.4 0.900
Weber
oligotrophic
2.76 10.8 0.204
-------
Table 5.6 Comparison of Phosphorus Retentive Capacity and Chemical Characteristics of Non-
calcareous Pre- and Postcultural Sediments.
*
Net Added P
Sorbed as
% Total Added P
Little St. Germain, W.
Little John
Minocqua, S.W.
Trout, S.
Devils
a
b
a
b
a
b
a
b
a
b
Initial
500
100
100
99
38
96
90
91
88
80
47
P Level (ju
1000
100
100
97
29
95
75
84
80
61
28
2500
100
100
87
16
83
57
63
58
40
15
for
P/g)of
5000
98
98
59
9
63
47
46
44
20
12
organic
Fe
108
113
49.7
11.7
70.8
53.5
52.5
58.4
37.1
21.2
Mn
1.39
2.54
0.823
0.305
1.90
1.55
2. 13
2.50
0.454
0.217
Al
me/Ej
'"£>' 6
13.2
10.3
22.0
24.7
33.4
10.5
--
90.3
58.9
Ca
0.43
0.44
1.92
1.77
1.55
1.06
3.00
3.36
2.50
1.81
C
126
228
254
287
123
153
135
166
73.2
143
P
11.1
15.8
4.07
1.14
9.55
9.19
5.05
6.01
2.39
0.936
* After sorption and desorption
a Postcultural sediment
b Precultural sediment
ro
o
-------
207
Little John Lake) also concurs with that of decreasing Fe and P which
have accumulated in the sediments. The laboratory experiments show the
postcultural sediment of Little John has a higher potential for P sorp-
tion than would be predicted by the relatively low Fe and P content.
The organic C content of Little John sediments is twice as high as the
other lakes. Generally, the effect of organic anions is to repress
P fixation (Swenson et al., 1949; Struthers and Seiling, 1950). The
low P content of Little John sediments might be attributed to a low
supply of P available for sorption since Little John is a spring-fed
lake. In Little John, Devils and in the southwest bay of Minocqua
the precultural sediments retain less P than the postcultural sediments.
This is correlated with lower Fe and Mn content in the older sediments
in each case. The Fe content of the sediment appears to be the dominant
influence in the P sorptive capacity. For example, even though the Al
content is higher than Fe in Devils Lake sediments, the P sorption is
low corresponding to the low Fe content. The organic C content does
not have a discernable effect on the P retentive capacity in the pre-
sence of high concentrations of Fe.
The generally high P retentive capacity of the noncalcareous lakes
is probably due to the surface-reactive amorphous Al and Fe hydroxy-
polymers which have a marked ability to retain inorganic P (Hsu, 1965).
In common soils, because of the effect of pH, surface-reactive amor-
phous Al and Fe hydroxy-polymers dominate the process of P fixation.
For example, in slightly acidic or neutral medium (pH 6-7) of dilute P
solution (such as in sediments), amorphous Al (or Fe) compounds are
stable and P is adsorbed on the surface (Hsu, 1965).
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208
The oxic leaching studies by Spear (1970) also indicate the high Fe
content of Trout sediments is responsible for the extremely low quan-
tities of P in solution after an extended period of equilibration (ca.
900 hours) at approximately pH 5. The acid extraction (IN HC1-H SO )
releases 70-99 percent of the total P (mean 90 percent) throughout South
Trout core WC-59; the acid soluble P concentration follows the total P
profile. Williams et al. (1970) reported values for the inorganic P for
surface samples of several noncalcareous lakes. The percent inorganic P
was as follows:
lake station percent inorganic P
Trout 1 90.4
Trout 2 85.0
Minocqua 1 83.0
Minocqua 2 91.1
Little John 1 82.3
Devils 1 71.8 (Williams et al., 1970).
Thus, the high percentage of inorganic P ii the noncalcareous lakes is
further evidence that the mechanism controlling the P deposition is
largely nonbiological and is probably controlled to a large degree by
the iron reactions both in the pre- and postcultural sediments. The
acid soluble P profile in the South Trout core ir';icates no change in
trend of primarily inorganic P deposition with depth of sediment. It
would be interesting to know whether a high percentage of P in Weber Lake
is organic P, since it is the only lake examined in which the Fe, Mn and
P association is not closely related.
Since the noncalcareous sediments have a very high P retentive
capacity, it is difficult to attribute an enrichment of P due solely to
an increase in the supply of P. For example, if the postcultural
-------
209
sediments shown in Table 5.6 are arranged in the order of their de-
creasing Fe content, this order concurs exactly to decreasing amounts
of P found in the sediments. Likewise, if the precultural sediments
are arranged in the order of their decreasing retentive capacity, the
Fe and P content in the sediments also decrease. However, the Fe/P
ratio of the pre- and postcultural shown in Table 5.7 provides some
insight into the importance of the P supply increase vs. the Fe supply
increase. In North Trout, in the northwest bay of Minocqua, Little
John and Devils both Fe and P increase in the postcultural sediments,
and in these lakes the Fe/P ratio is larger in the precultural sedi-
ments. A low Fe/P ratio in the postcultural sediment and a high Fe/P
ratio in the precultural sediment indicates the P deposition increases
in a greater proportion than Fe since the onset of cultural activities
in the basin. This would imply that the P supply has increased in the
lake. The above hypothesis seems to correspond to what is known about
the P supply to the northwest bay of Minocqua. During the period
1935-1964 the treated sewage from the town of Minocqua was discharged
to the northwest bay of Minocqua causing an increase in supply of P
to the lake. As pi'edicted the Fe/P ratio decreases in the postcul-
tural over the precultural sediment. If the Fe/P were high and low
in the post- and precultural sediments, respectively, the implication
may be that the sedimentary P increase is due to greater depositional
efficiency with Fe-containing compounds, while the P supply remained
relatively constant. In the drainage lakes, South and West Bay
of Little St. Germain and in the southwest bay of Minocqua the Fe/P
ratio of the postcultural sediment increases over precultural sediment,
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210
Table 5.7 Iron to Phosphorus Ratio of the Noncalcareous
Pre- and Postcultural Sediments.
Lake Fe *K(Fe) K(P)
Little St. Germain, W.
Little St. Germain, S.
Trout, N.
Trout, S.
Minocqua, S.W.
Minocqua, N.W.
Weber
Little John
Devils
a
b
a
b
a
b
a
b
a
b
a
b
a
b
a
b
a
b
10.1 o
6.83
8.05 ++
4.94
9.08 ++ +++
22.2
10.2 o +
12. I
8.00 ++ o
6.20
8.69 + +++
14.1
3.89 o o
3:50
14.3 ++ +++
21.6
20.5 ++ +++
24.3
a Postcultural sediments
b Precultural sediments
K Mean Fe and Mn concentration of postcultural over precultural
sediments (see Table 5.9 for explanation of notation)
-------
211
thus, indicating the Fe supply in the recent sediments increases in a
greater proportion than the P. In Weber Lake there is no change in
Fe/P ratio with depth of sediments which indicates stable conditions
of Fe and P supply.
-------
212
D. Distribution of Iron and Manganese
Total Fe and Mn analyses were performed on all the cores investi-
gated. The distribution of Fe and Mn in the sediments may depend pri-
marily on 1) the supply rate of particulate and dissolved Fe and Mn 2)
the migration of Fe and Mn as influenced by redox conditions and 3)
rate of accumulation of the whole sediment.
Of particular interest in regard to the influence of redox condi-
tions in controlling Fe and Mn concentration is Mackereth's (1966) in-
terpretation of the Fe and Mn distribution in the postglacial sediments
of English lakes. Mackereth (1966) noted since Mn is reduced and mobil-
ized at a higher redox potential than Fe, the separation of Fe and Mn
is considerable depending on the redox conditions. During a progression
from oxidizing to reducing conditions in a lake, Mn loss from the sedi-
ments begins before Fe loss, and during the reverse process of a change
from reducing to oxidizing conditions, Fe begins to accumulate in the sedi-
ment before Mn does. Thermodynamic data predict the Fe compounds that should be
expected in a lake environment, such as Fe carbonate, sulfide, silicate
and hydroxide, are uniformly less soluble than the corresponding Mn com-
pounds, and that ferrous ion is more easily oxidized than manganous ion
under naturally occurring pH-Eh conditions (Borchert, 1965; Krumbein
and Garrels, 1952). Mackereth (1966) considers the reductive separation
of Fe and Mn both in the drainage system and in the lakes. For instance,
when the transport in the drainage system occurs by reduction to the
mobile manganous and ferrous forms, considerable separation of the two
elements may be expected, since the Mn is more easily reduced than Fe.
Mackereth postulated in Windermere the enrichment of Mn with respect to
-------
213
Fe in the sediments soon after the end of glaciation was brought about by
the onset of reducing conditions in the soils of sufficient intensity to
produce manganous ion but not intense enough to effect the large scale
reduction of iron to ferrous ions. Thus, Mn was preferentially removed
from the drainage soils and carried into solution to the oxidized lake
waters where deposited. Mackereth then postulated that the position of
the marked fall in Mn concentration in the early deposits of Esthwaite
represented the time of the first formation of an anaerobic hypolimnion,
since Mn is released from the sediments during thermal stratification
and carried into the epilimnion at the overturn and thereby removed
from the lake.
Calcareous Lakes. The Fe and Mn content generally increases by
2-4 fold in the postcultural sediments over the precultural sediments
in all the calcareous lakes examined. The postcultural deposition rate
of Fe increases from the deep-water area of Mendota towards University
2
Bay and varies from 151-342 mg Fe/cm /100 yr. The sedimentation inten-
sity of Fe for Monona is approximately the same as Mendota core WC-86,
2
while Wingra has the lowest deposition rate of 127 mg Fe/cm /100 yr.
The sedimentation intensity of Mn, however, is more or less the same
2
for all three lakes ranging from 8.3-11.1 mg Mn/cm /100 yr.
In Table 5.8 is shown the Fe/Mn ratio for post- and precultural
sediments in each lake. In all of the cores, with the exception of the
Mendota core WC-89, the Fe/Mn ratio in the postcultural sediments is
higher than the precultural sediment. "he Fe/Mn ratio in Mendota core
WC-89 probably did not fit the trend because Mn in the top 10 cm of the
core was particularly enriched, which reduced the Fe/Mn ratio considerably.
-------
214
Table 5.8 Mean Iron: Manganese Weight Ratio for the Pre- and Post-
cultural Sediments of Calcareous Lakes.
Mendota Mendota Mendota Mendota Monona Wingra
WC-95 WC-89 WC-86 WC-84 WC-46 WC-92
Water depth (m) (24 m) (23 m) (18 m) (12 m) (16 m) (4 m)
Mean Fe/Mn 20.3 18.4 25.6 31.0 23.2 13.4
Ratio for the
Postcultural
Sediment
Mean Fe/Mn 17.2 21.7 17.8 18.5 16.8 7.6
Ratio for the
Precultural
Sediment
However, the long Mendota core also taken in the deep water shows a
higher Fe/Mn ratio in the postcultural sediment; the mean Fe/Mn ratio for
the depth of the marl sediment (62-970 cm) is 17.2 which is close to the
mean Fe/Mn ratio found in marl sediment of the short Mendota and Monona
cores.
The general increase in Fe to Mn in the postcultural sediments of
calcareous lakes may be explained as due either to an increase in the
rate of Fe supply over Mn or to the greater loss of Mn than Fe from the
++
reduced bottom muds. In reduced bicarbonate-rich solutions Mn shows
a greater solubility than Fe' (Borchert, 1965), so the separation of
Fe and Mn could take place in proceeding from higher to lower oxidizing
conditions. Since the advent of domestic drainage to the lakes, lower
redox conditions of the bottom waters and muds presumably have devel-
oped. Thus, a greater net migration of Mn from the sediments results in
an increase in the Fe/Mn ratio. The higher Fe/Mn ratio in the post-
cultural sediments could also be due to a higher supply rate of Fe to Mn.
-------
215
It is noticed that Fe/Mn ratio also increases in the postcultural with
respect to the precultural sediment of Wingra which does not stratify
or develop reducing conditions. Therefore, the high Fe/Mn ratio in the
postcultural sediment cannot be attributed to the variation in redox
potential in Wingra, but instead to the increase in Fe with respect to
Mn supply. Although lower redox conditions favoring the loss of Mn over
Fe since the cultural period cannot be discounted in Mendota and
Monona sediments, it would appear that an increase in Fe over Mn supply
would be the dominant influence. The latter explanation is supported
by the fact that the postcultural deposition rate of Mn varies only
slightly between all the calcareous cores examined, whereas the Fe depo-
sition rate varies considerably between the different cores.
The Fe/Mn ratio in both the pre- and postcultural sediment of
Wingra is less than Monona and Mendota deposits. In lakes Monona and
Mendota the precipitation and re-solution of Mn oxides, hydrated oxides
or carbonates are also a function of the deoxygenated summer hypolim-
netic waters, whereas in the well-oxygenated waters of Wingra the pre-
cipitation of Mn compounds may be more efficient on an annual basis.
This may account for the enrichment of Mn relative to Fe in Wingra sed-
iments. It has already been concluded that the variation in redox con-
ditions is not the dominant influence in the separation of Fe and Mn
during the cultural period, but it may be that lakes Mendota and Monona
experienced oxygen deficiency before the cultural period enough to make
a contrast to the well-oxygenated waters of Wingra. Nriagu (1968)
suggested that prior to the change in sedimentation of Lake Mendota
associated with human activity, the lake had developed an oxygen
-------
216
deficiency intense enough to cause reduction of sulfates to sulfides
but was able to maintain its basin free of black muds by the process of
self-purification. Also Fruh et al. (1966) observed the rate of oxygen
depletion in the hypolimnion,of Mendota has not changed appreciably for
the past half-century.
i
Nriagu (1967) proposed from his studies of Fe and S in Lake Mendota
cores that the progressive upward enrichment of Fe in the sediments is
due either to the diagenetic migration of Fe in the interstitial waters
maintaining an upward diffusive flux or to increased efficiency of pre-
cipitation and retention of ferrous iron in the sediments as sulfides.
Nriagu (1967) found a positive relationship between Fe and sulfide S in
the cores. However, a feature shared by the gyttja and marl is that
the Fe content is greater than should be required to hold all the
sulfur as FeS (Nriagu, 1967). Several investigators (Lynn and Bonatti,
1965; Nussman, 1965) have attributed the relatively high content of Mn
found in the tops of sediment cores to the ionic or molecular diffusion
of Mn upward in pore water solution. The Mn dissolves upon burial in
reduced sediments, then slowly migrates and accumulates in the oxidized
upper strata (Lynn and Bonatti, 1965). Such migration of Mn could, there-
fore, cause an increase in the Fe/Mn ratio in the top layers. There is
a sharp upward enrichment of Mn evidenced by the low Fe/Mn ratio in the
top 10 cm of deep-water Mendota core WC-89; however, the Mn is not en-
riched in the top 0-10 cm of any other calcareous cores investigated.-
Thus, it appears that the upward migration of Mn does not exert an over-
all influence causing the increase in Mn concentration in the uppermost
layers of the postcultural sediments.
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217
The increase in Fe supply is probably associated with increased
runoff from the land. Wang and Brabec (1969) found the turbidity in
Illinois river water, to be related to the particulate P, Si and Fe
(III) concentrations. The molar ratio of Si to Fe (III) was 1:1.47.
Carroll (1958) found the association of Fe with clay minerals is an
important means whereby Fe is transported by rivers to lakes. According
to Carroll, Fe is associated with clay minerals 1) as an essential con-
stituent, 2) as a minor constituent within the crystal lattice and 3)
as iron oxide on the surface of mineral platelets. The close relation-
ships between the Fe, K and Al profiles in the calcareous lakes are
further evidence that Fe is mainly associated with the clay mineral
fraction. Analyses of the clay fractions of soils show that Fe is
mainly associated with the finest fractions (the clay and silt grades),
which have extremely large surface area (Carroll, 1958). This may
account for the high concentrations of Fe found in the center of Lake
Mendota.
Noncalcareous Lakes. In six of the nine noncalcareous lake cores
examined in this study, the mean Fe concentration increases in the post-
cultural sediments over the precultural sediments; however, in West Bay
of Little St. Germain, South Trout and Weber the mean Fe concentration
in the pre- and postcultural sediments remains unchanged. The post-
2
cultural sedimentation rate varies from 10.8 to 207 ing/cm /100 yr for
2
Fe and from 0.20 to 6.1 mg/cm 7100 yr for Mn (see Table 5.5). The highest
deposition rate for Mn was observed in Trout Lake. The high deposition
rate of Fe is usually accompanied by a high deposition rate for Mn. Even
though the concentrations of Fe and Mn in the noncalcareous lakes are
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218
higher than the calcareous lakes, the deposition rates of both Fe and
2
Mn are higher in the calcareous lakes (i.e. 151-342 mg Fe/cm /100 yr and
2
8.3-11.1 mg Mn/cm /100 yr).
In Table 5.9 is shown the Fe/Mn ratio for the pre- and postcultural
sediments in each lake. There are no uniform conditions for all the
lakes of increasing or decreasing Fe/Mn ratio in the postcultural over
the precultural sediments. Only in lakes Little St. Germain and Weber
is the Fe/Mn ratio higher in the postcultural over the precultural sed-
iment. In lakes Little John, North and South Trout and Devils, the Fe/Mn
ratio is higher in the precultural sediment, and in the northwest and
southwest bay of Minocqua, Devils and South Trout, the Fe/Mn remains un-
changed in the pre- and postcultural sediments. Apparently, the Fe/Mn
ratio does not indicate a change in redox conditions for the deep strat-
ified lakes which would favor a loss in Mn with respect to Fe as might
be expected if the bottom lake waters and muds are becoming more reduc-
ing. Only in Little St. Germain Lake where the Fe/Mn ratio is
higher in the postcultural sediments is the selective migration of Mn
out of the sediments under reduced lake conditions a plausible explana-
tion. The high to low Fe/Mn ratio in the pre- and postcultural sediments,
respectively, for North Trout and Little John, could be explained by
changing redox conditions in the watershed soils. If the land supported
lush vegetation in the precultural era, so that the Eh and pH of stream
and groundwater would be low, the reductive efficiency would lead to in-
creased migration and supply of Fe but little change in the rate of
supply of Mn. The increase rate of Fe supply would increase the Fe/Mn
ratio in the sediments. If the watershed soils after deforestation
-------
Table 5.9 Mean Iron: Manganese Weight Ratio for the Pre- and Postcultural Sediments of Noncalcareous Lakes.
Little St. Little St. Trout, Trout, Little Minocqua, Minocqua,
Germain, W. Germain, S. N. S. John Weber N.W. S.W. Devils
Water depth (m) (16 in) (7 m) (26 m) (33 m) (5 m) (13 m) (11 m) (14 m) (13 m)
Mean Fe/Mn ratio 70.6 117 23.3 21.0 66.6 52.6 76.4 37.3 93.7
for postcultural
sediment
Mean Fe/Mn ratio 46.1 87.1 32.6 23.1 78.3 39.9 80.9 34.3 101
for precultural
sediment
* K +++ ++ -- o __++ o o o
* mean Fe/Mn ratio of postcultural sediment
mean Fe/Mn ratio of precultural sediment
Notation: 1.1> K>0.9 = 0 1.1 < K £1.2 = + 0.9 > K>0.8 » -
_K > 1.5 = +++ _K< 0.5 = ---
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220
became more oxidizing, the Fe would become less mobile in the drainage
waters producing a low Fe/Mn ratio in sediments. In both of the above
cases it is assumed the stream and groundwater drain constantly into
oxidizing lake basins. If the Fe/Mn ratio remains unchanged, as in
four noncalcareous cores examined, this is probably an indication that
a variation in redox conditions in the soils or lake water is not a
primary influence. A constant Fe/Mn ratio with depth of sediment may
indicate as Mackereth (1966) has shown for Ennerdale, that the rate of
transport of Fe and Mn is influenced mainly by erosional conditions
which would not be expected to bring about a separation of the two
elements.
In summary, it would appear that a variation in redox conditions
in the lake basin or soils may account for the recent changes observed
in the Fe/Mn ratio in Little St. Germ n, Little John and North Trout,
but in the other lakes examined there was no change in the Fe/Mn ratio
with depth of sediment. However, in the lakes (with exception of South
Trout) in which there was no change in the Fe/Mn ratio with depth of
sediment, the Fe and Mn concentrations increase in the postcultural
sediments. The general upward increase in Fe and Mn in most of the
noncalcareous cores may possibly be brought about by an increase in the
supply of soluble and particulate Fe and Mn from the ash of forest fires
or by the exposure and leaching of the B horizon of the podzolic soils
of the cutover or burned forests. The period of maximum disturbance
from cutover forest occurred several decades ago (Curtis, 1959); there-
fore, other explanations are.probably needed to account for the increase
in Fe into the most recent upper layers of sediment. The changes in
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221
Fe (and P) profiles of South Trout Lake are quite abrupt and fluctuating
even though K, Mg and Ca concentration remains more or less constant in
both the pre- and postcultural sediments. Thus, it seems the Fe supply
to South Trout Lake is subject to fairly rapid changes in differential
leaching and erosion from the outwash and till surrounding Trout Lake.
The changes in sedimentary concentrations of Fe, Mn, P and organic C are
more pronounced in three noncalcareous lakes examined (Little John, North
Trout, and in the northwest bay of Minocqua) than changes in concentra-
tions of Mg, Al, K and Ca-containing compounds during (and after) the
deforestation period in northern Wisconsin.
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222
E. Distribution of Aluminum, Potassium
Magnesium and Calcium
Total Al, K, Ca and Mg analyses were performed on all the cores
investigated. The distribution of these elements may depend primarily
on 1) the rate of supply of dissolved and particulate mineral matter
2) the biological or chemical precipitation of carbonates and 3) the
variation in the accumulation of the whole sediment. Aluminum, Mg, Ca
and K may occur in a large variety of mineral structures such as feld-
spars, clay minerals and amorphous aluminosilicate gels. Mackereth
(1966) noted that Na, K and Mg were associated with the mineral fraction
of the sediment of English lakes, but Ca was not so clearly associated
with mineral erosion. Calcium was evidently more easily leached from
the soil than Mg. According to Mackereth, the Ca is abundantly pre-
deposited into the English lake sediments only at times of very intense
erosion when the rate of precipitation of clastic material is high
enough to prevent removal by leaching of much Ca. In the noncalcareous
Wisconsin lakes the Al, Mg, Ca and K profiles show a close relation-
ship. There should, on the grounds discussed above, exist a
direct relationship between Al, K, Mg and Ca content in the sediments
and erosion intensity of the drainage basin of the noncalcareous lakes.
In Table 5.10, the sedimentation intensity of Al is arranged in de-
creasing order for the northern Wisconsin noncalcareous lakes. The Mg
and K deposition rates almost exactly concur to the order shown for Al,
but the Ca deposition rate deviates somewhat from the order shown by
Al, K and Mg. The postcultural deposition rate of K increases from
the deep-water area of Mendota towards University Bay and varies from
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223
Table 5.10 Sedimentation Intensity of Aluminum, Magnesium, Potassium
and Calcium in Noncalcareous Lakes in Northern Wisconsin
Lake
Minocqua, S.W.
Trout, N.
Little John
Little St. Germain, W.
Minocqua, N.W.
Weber
Al
71."5
52.4
39.2
34.8
28.6
26.2
K
mg/cm 7100
13.2
9.20
8.65
8.21
8.36
6.00
Mg
yr
6.70
6.55
6.60
5.67
3.50
2.22
Ca
3.62
4.83
4.52
1.46
2.31
0.575
72 to 189 mg K/cm /100 yr. The sedimentation intensity of K is 107 and
2
83 mg K/cm /100 yr in Monona and Wingra, respectively. In the southern
calcareous lakes, the K and Al concentration is enriched by 2-5 times
in the postcultural over the precultural sediments. The magnitude of
the erosional activity since man has moved into the Madison lake region
has been quite intense compared to most noncalcareous lakes in northern
Wisconsin. The Ca (and Mg as dolomite) concentration in Mendota, Monona
and Wingra sediments is dominated by the carbonate deposition and will
not be discussed further here (see section on carbon distribution).
Noncalcareous Lakes. The area surrounding the northern lakes is
covered with second-growth coniferous and deciduous vegetation indicating
that fires or cutover forest have modified the ecology at one time, but
the area has since recovered from the period of maximum disturbance from
logging activity. Little St. Germain and the southwest bay of Minocqua
(both drainage lakes) were the only lakes examined in this study in
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224
which Mg, Al, K and Ca-containing compounds increase in the postcul-
tural over the precultural sediment. The increase of Mg, Al, K and Ca-
containing compounds is correlated to the increased runoff and leaching
of the soils during the deforestation period. The core profiles indi-
cate that runoff of erosional products reached a peak approximately 40-
80 years ago. The decline in erosional products after this period is
attributed to the regrowth of vegetation and timber. Bormann et al.
(1968) found the drainage water from a cutover forest showed net losses
of Ca, Mg, Na and K which were 9, 8, 3 and 20 times greater, respec-
tively, than similar losses from five undisturbed forest ecosystems.
Mackereth (1966) regarded the potential internal productivity of
a lake basin to be determined in part by erosion rate characteristics
in the drainage area. He maintained that in a regime of less intense
erosion the soil in the drainage area accumulates and is held in a suit-
able spatial position to allow leaching of various nutrient elements in-
to solution in a form which is available to the living populations of
the lake, whereas in a drainage area of intense erosion, the soil is re-
moved from the site of leaching and deposited in the sediment where it
is effectively protected from leaching. Thus, according to Mackereth,
periods of more intense erosion would then be unfavorable to high inter-
nal productivity in the lake, while periods of lower erosion intensity
would favor higher internal productivity. If the sedimentation rate has
generally increased in the postcultural period of the northern Wisconsin
noncalcareous lakes, then according to Mackereth's view, the internal pro-
ductivity of these lakes is not favored in recent times. The high sed-
imentation intensity of Al and K, as shown in Table 5.10, in oligotrophic-
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225
mesotrophic North Trout would tend to support Mackereth's contention.
On the other hand, the low sedimentation intensity of Al and K of Weber
Lake does not support this view. Nevertheless, the detection of
changes in erosion rates may be useful information to evaluate the
history of a lake. For instance, Cowgill and Hutchinson (1964) re-
ported the whole biological association was altered in Lago di
Monterosi near Rome at about 200 B.C. during a period of increased
erosion in the watershed. Cultural eutrophication was initiated not by
artificial liberation of specific nutrient elements into the water, but
by a rather subtle change in hydrographic regime.
In Devils Lake the Mg, Al, K and Ca-containing compounds increase
in the postcultural over the precultural sediments. The shoreline area
of Devils Lake has been modified by the development of recreational
areas, cottages and a railroad bed which probably accelerated the
erosional activity in the region. Twenhofel and McKelvey (1939) thought
the sources of sediment of greatest importance were not the quartzite
cliffs and talus near Devils Lake but rather the shore and shallow
bottoms composed of sands, silts and clays originally brought into the
region by the ice sheets. They also thought the two streams entering
Devils Lake were not contributing very large quantities of sediments,
particularly of clastic character. The postcultural sedimentation in-
tensity of Mg, Al, K-containing compounds is faster in Devils Lake than
any of the northern noncalcareous lakes.
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CHAPTER VI
EVALUATION OF THE RELATIONSHIP BETWEEN THE CHEMICAL
COMPOSITION OF LAKE SEDIMENT CORES AND LAKE EUTROPHICATION
AND
SUGGESTIONS FOR FURTHER RESEARCH
The purpose of this chapter is to discuss, based on the experience
gained from this study, the limitations and potentialities of using
lake sediment cores to describe eutrophication, to offer suggestions
for further research and to propose broad guidelines for other investi-
gators to follow in pursuing a similar project.
A. Potentialities and Limitations of Using Lake Sedi-
ment Cores to Evaluate Eutrophication of Lakes.
Attention has been directed in this study to examining the recent
changes in lake history through chemical analyses and interpretation
of lake sediment cores. A lake is responsive to changes in its water-
shed, whether these occur slowly by natural means or at an accelerated
rate through the intervention of man. The information needed to trace
changing limnological and watershed conditions of a lake must come
from a geologic record preserved in the lake sediments. The findings
from this study have indicated that changes in the chemical strati-
graphy of lake sediment cores can be traced to cultural activities in
the watershed; these stratigraphic changes are especially pronounced
in the southern calcareous lakes.
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Limitations in Using Lake Sediment Cores to Describe Eutrophica-
tion. The limitations and logical complexities facing a paleolimnolist
in attempting to describe past events of nature cannot be overlooked.
This is due largely to the relative lack of control over what can be
observed and the range in space and time the observed-variables occupy.
Nevertheless, a greater understanding of the changes from the past into
the present is needed to yield insight into the effects that man's ex-
ploding activities have had on lakes. The change in sedimentation of
Lake Mendota will be used to illustrate the constraints imposed in
attempting to reconstruct lake history. The estimated deposition rate
of P and organic C in the center of Lake Mendota is 5-8 and 3-5 times
greater, respectively, in the postcultural sediment over the precultural
sediment. However, if the same comparison was made in University Bay
these estimates would change to account for the higher deposition rate
of P and organic C at the University Bay location. Likewise, if core
samples were taken throughout the Mendota basin, the concentration, the
moisture content, density and sedimentation rate would vary; this would
be especially true in a drainage lake such as Mendota where the tribu-
taries of Yahara River, Six Mile Creek and Pheasant Branch Creek carry
runoff from urban and rural lands. Based on the core sampling of
University Bay and the deep-area of Mendota, it appears that the P con-
centration in the marl sediment is more uniform over the lake, but since
the advent of domestic drainage the influent materials have allowed
fractionation of sediment particles with water depth which has compli-
cated the sedimentation regime of the postcultural sediments. In the
northern noncalcareous lakes similarities as well as differences exist
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228
in the chemical stratigraphy of cores taken from separate bays within
the same lake. Thus, the sampling complexities impose a limitation on
making representative estimates of rate changes based on one or a few
cores taken within a lake. This does not, however, restrict the inves-
tigator from using a specified location in lake as a reference point to
compare recent and past sedimentation changes. The sampling dependency-
is then assumed to be a recognizable feature of the system. Limitations
are thus placed on using chemical criteria of trophic status in a quan-
titative expression that is representative of the entire basin. In this
study the center of the lake was chosen as a reference point to document
changes that have occurred in recent vs. past times. The sampling de-
pendency may vary considerably from lake to lake; drainage lakes situ-
ated in an agricultural region may represent the extreme in sampling
dependency. It would be advantageous for future investigators working
on these same lakes to use the same reference point. Further research
should be directed into establishing the extent to which lake morphology,
hydrologic regimes and geomorphology affect the reliability of using
one or more cores tc represent processes occurring in the entire basin.
If the deposition rate of P and organic C increases by several fold
in the postcultural over the precultural Mendota sediments, the observed
rate change may be accounted for by several processes acting to produce
a combined effect. For instance, it appears that the enrichment of P
in the postcultural sediments of Mendota and Monona is due not only to
the increase in supply of P from domestic drainage, but to the increase
in P retentive capacity of the postcultural sediment and to an increase
of P deposition due to the concomitant increase in Fe, Mn and Al-containing
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229
compounds. The increase in organic C deposition rate in Lake Mendota
represents both an increase in auto- and allochthonous organic C. An
increase in a lake's own total production of organic C becomes mixed
with and is indistinguishable from that of external origin. This again
illustrates the fact that the link between changes in-sedimentary chem-
istry and eutrophication is largely a qualitative expression. However,
the conditions of nutrient and organic supply and their resultant depo-
sition within a lake are of paramount importance, so lake sediment cores
which are dated can be used to express the amounts of materials depos-
ited to the lake bottom per unit time as a combined effect of several
operating processes.
A difficulty in interpreting the response of lakes to man's in-
fluence is that the time span involved is short; the thickness of the
sediments produced during postcultural interval is often less than 0.5 m
of unconsolidated sediment. In two of the noncalcareous lakes examined
in this study the depth of the postcultural column was only 15 cm thick-
ness. The short time span « 150 years B.P.) involved does not allow
C-14 measurements to be made with accuracy (see literature review);
therefore, other means such as ragweed pollen analyses must be used to
identify the base of the cultural horizon and to establish sedimentation
rates. This method does not allow the establishment of series of dates
Within the postcultural interval (absolute time scale). An absolute
time scale for postcultural lake sediments has never been constructed.,
co the author's knowledge, except by indirect methods. The concentra-
tion-depth diagrams are not completely satisfactory because of the con-
straint imposed by the method; the composition of sediment related to
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230
volume or weight does not take into account varying rates of sedimenta-
tion. Ideally the composition of sediments should be expressed both as
concentration and as sedimentation intensity. Research should be
directed toward estimating sedimentation rates for both pre- and post-
cultural sediments of the calcareous and noncalcareous lakes in
Wisconsin. To date there has not been a single well-dated core from any
Wisconsin lake. It is the author's opinion that this aspect of lim-
nology of Wisconsin lakes has been grossly neglected. Any dating
accomplished from the lakes (and core locations) examined in this study
would augment the data already produced.
The depth of sediment mixing will determine the resolution of the
chemical stratigraphy. In other words, does the chemical record show
changes of 5 years, 20 years or 50 years for a given interval size? If
the sediment record is obscured by the mixing of old and new deposits,
any rate expression derived to describe cultural eutrophication becomes
less accurate. The results from this study indicate greater resolution
is achieved in following sedimentary changes for P in Lake Mendota by
fractionating a core into 2 cm rather than 5 cm intervals. If mixing
were deeper than only the upper layers (ca. 2-5 cm) in Lake Mendota
deep-water sediments, greater resolution would not be observed by taking
2 cm intervals. In Weber Lake the changes in chemical stratigraphy were
quite pronounced in spite of the slow sedimentation rate. In order for
the pronounced peaks to persist, the depth of the sediment mixing column
must be short in Weber Lake. The evidence for the extent of mixing in
lake sediments is quite conflicting. Undoubtedly, the depth of mixing
of sediments would vary from lake to lake and locations within a lake.
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231
In the interpretation of the sedimentary record the assumption is gen-
erally made that there has been essentially no movement of materials
upward or downward except in the biologically active layer near the sur-
face. Replicate cores taken from the center of Lake Mendota indicate the
maximum P peak about 20 cm below the sediment-water interface can be
reproduced. Thus, the extent of mixing does not appear to laterally or
vertically change the overall distribution pattern of P in the deep-
water area of Lake Mendota. Research needs to be directed at determin-
ing the depth at which new and old deposits are mixed below the sediment -
water interface under various conditions and lake bottom types.
Finally, the primary materials that accumulate in the upper layers
of a sediment core can be altered by postdepositional changes brought
about by biological and chemical processes. The findings from this
study indicate that organic C once deposited in historical sediment
layers appears to resist further decomposition. In the Lake Mendota
long core organic C concentration remains constant within a range of
59-77 mg/g organic C over the core interval of 62-900 cm. Decomposition
of N-containing compounds with sediment depth is indicated by the C/N
ratio in the South Trout Lake core. Sustained study needs to be given
to the chemical transformations that occur in the recent unconsolidated
sediments.
Potentialities of Using the Chemical Composition of Lake Sediment
Cores to Describe Eutrophication. The composition of the sediments with
depth and, therefore, with time presents a pattern of change which docu-
ments the progressive increment of materials deposited to the lake
bottom. In most of the cores examined in this study, pronounced chemical
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changes occur contemporaneously with the break in the ragweed pollen
profile. Thus, changes in the chemical stratigraphy can be traced to-
man's activities in the watershed. If it is assumed that the sedimen-
tation rate throughout the period represented by the concentration-
depth diagram is constant, a calculation can be made showing the incre-
mental increase or decrease in concentration per unit thickness of sed-
iment (or per year if time is estimated). However, this study has re-
vealed that concentration-depth diagrams do not generally contain suf-
ficient information to estimate an incremental rate change in nutrient
concentration which accurately reflects changes in nutrient supply due
to man's activities in the watershed. The deposition rate of the whole
sediment imposes a constraint on the system which necessitates an ab-
solute time scale in the pre- and postcultural sediments. This thesis
is in good agreement with Mackereth's (1966) observation on English
Lakes in which he states, "The observed changes in composition of the
sediment can most easily be explained if the sediment is regarded as a
sequence of soils derived from the drainage areas of the lakes. The
composition of the residue eventually reaching the lake bed can then be
accounted for in terms of the rate of erosion of the drainage basin
rather than in terms of changing rates of organic productivity either
on the drainage basin or in the lake waters." In effect, the concentra-
tion profiles for organic C and other nutrient components are diluted by
allochthonous materials. This, in itself, is useful information because
in such a situation the sedimentation rate is usually fast and the con-
centrations of nutrient material in the enclosing sediment may be less,
which in turn may affect the dynamics of nutrient release rates from
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sediments. Nevertheless, if it can be shown by fact (or by deductive
reasoning) that the sedimentation rate is constant throughout the in-
terval in question, then the chemical data contained in the concentra-
tion-depth diagram conveys all the information about changes that is
contained in the deposition rate diagram. For example, in Little John
Lake and in the northwest bay of Minocqua the Al, K and Mg-containing
compounds (associated with erosional products) do not increase in the
postcultural sediments over the precultural sediments, so it will be
assumed the sedimentation rate is constant (see Table 4.9). It was
shown earlier from the Fe/P ratio in these lakes that the P supply has
increased in the postcultural sediments (see Table 5.7). In Table 6.1
is shown a rate expression (i.e. percent P increase/yr) for P in the
Table 6.1 Average Percent Increase in Phosphorus Deposition in Little
John and Northwest Bay of Minocqua.
Lake
Minocqua, N.W.
Little John
Average Percent Increase
of P (mg/g per 5 cm in-
terval)
a 42
b f^ zero
a 12
b /x/ zero
Average Percent Increase
P (mg/g per year)
1.3
/v zero
1. 1
*** zero
a) Postcultural sediment
b) Precultural sediment
pre- and postcultural sediments of Little John and in the northwest bay
of Minocqua. In both lakes the precultural sediment show a zero in-
crease in P per year, but in the postcultural sediments the P increases
at a rate of 1.3 and 1.1 mg/g P per year for the northwest bay of
Minocqua and Little John, respectively. Although such a rate expression
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234
is informative, it may not be a justified derivation for all the lakes
examined for the reasons stated above.
In this study the overall sedimentation rate of the postcultural
column was used to transform the chemical data based on concentration
to a deposition rate (see Table 4.12). This derivation then can be
used to estimate a discrete rate change in nutrient concentration which
can be related to eutrophication. For example, in the Lake Mendota long
core the overall precultural deposition rate of P was estimated and com-
pared to the postcultural interval. The P deposition rate increases 5-8
fold in the postcultural over the precultural interval in the center of
Lake Mendota. A knowledge of chemical deposition rates provides insight
into the overall understanding of eutrophication which cannot be re-
vealed by a static measurement of concentration. For instance, the use
of lake sediment cores elucidates the relationship between high concen-
trations of P in the sediments of the noncalcareous lakes and the low
concentrations of P in the noncalcareous lakes. Even though the concen-
trations of P are much higher in the noncalcareous lakes, the deposition
rate is usually about the same or less than in the calcareous lakes.
Likewise, the mean concentration of P in the postcultural sediment of
Lake Wingra is 3.1 times less than the deep-area of Lake Mendota, but
the deposition rate of P in Wingra is only 1.3 times less than the deep-
area of Lake Mendota. Eutrophication of a lake includes the accumula-
tion of sediments. Such a process is evolutionary in nature and all
lakes are affected to a greater or less extent by this phenomenon. The
dry sediment accumulated in postcultural sediment column varies from
22 2
0.905 g/cm to 2.42 g/cm and from 7.15 to 17.2 g/cm for the
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235
noncalcareous and calcareous lakes, respectively. The filling rate of
Lake Wingra is about 9 times faster than Little John Lake; both of these
lakes are shallow eutrophic lakes in their respective geological regions.
Except for the lower dry sediment accumulation rates of Weber Lake and
in the northwest bay of Minocqua Lake, the dry sediment accumulation is
more or less uniform for the profundal postcultural sediments of the
noncalcareous lakes.
The chemical composition of the sediment cores with depth and, there-
fore, with time presents a pattern of change in which the relationship
between different elements can be elucidated in both the pre- and post-
cultural sediments. In all the noncalcareous lakes examined, P, Fe, and
Mn concentration profiles are closely related. This is the case whether
the sediments are pre- or postcultural origin, so the mechanism does not
appear to have changed with the modifying activity of man in the water-
shed. In general, the aerobic sorption and desorption of P studies indi-
cate the sediment laid down postculturally is a more favorable sorptive
environment for P and a less favorable desorptive environment for P than
sediment laid down prior to cultural influences. This is due primarily to
the concurrent increase in Fe in the postcultural sediments for both cal-
careous and noncalcareous lakes. The generally high P retentive capacity
of the noncalcareous lakes is probably due to the surface-reactive amor-
phous Al and Fe hydroxy-polymers. However, Fe rather than Al content
appears to be the dominant influence in determining P retentive capacity
of the pre- and postcultural sediments. The acid soluble P profile in the
South Trout core indicates no change in trend of primarily inorganic P
deposition with depth of sediment. The mechanism for controlling the P
deposition is largely nonbiological and is probably controlled by the
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236
iron reactions both in the pre- and postcultural sediment. Oligotrophic
Weber Lake was the only noncalcareous lake examined in which 1) the Fe
profile was associated with Al, K and Mg-containing compounds and 2)
the Fe, Mn and P profile were not associated to each other. As a com-
parison, in all the calcareous lakes the Fe and Mn profiles bear a re-
lationship to the Al and K profiles indicating the Fe is probably
associated primarily with the clay mineral fraction. The Fe/Mn ratio
increases in the postcultural sediments over the precultural sediments
of the calcareous lakes. The changes in Fe/Mn ratio are thought to be
primarily the result of an increase in Fe relative to Mn supply in the
postcultural sediment of Mendota and Monona.
Analysis of past rates of change must be taken together with the
detection and measurement of recent man-induced changes. Therefore,
the chemical stratigraphy of lake sediment cores provides the under-
standing which is needed to detect a change as an acceleration; only by
detecting accelerations is it possible to distinguish between normal
and cultural processes. For example, in Devils Lake the P concentration
at 60 cm level (>400-600 years B.P.) begins to increase slowly from 1.0
mg/g to 1.24 mg/g; this change is followed by a rapid rise in P concen-
tration from 1.24 mg/g to 2.39 mg/g in the postcultural interval. Even
though Devils Lake is currently an oligotrophic-mesotrophic lake, the
sediments reveal that a natural process has occurred which produced a
slow change in the chemical composition of the sediment, and this was
followed by man-induced changes in the watershed which have accelerated
the process considerably. In North and South Trout, West Bay of Little
St. Germain and in the northwest bay of Minocqua, Weber and Devils
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237
Lake , the organic C shows a slight upward decrease before the post-
cultural period is initiated; this is followed by a rapid decline in
organic C during the postcultural period. In the long Mendota core the
"normal rate" of P change (before man's influence) with sediment depth
is nearly zero. The chemical stratigraphy of the Lake Mendota core in-
dicates that stable limnological and watershed conditions existed in the
lake for a long period historically. The initial rise in P concentra-
tion begins at the 55-60 cm level (ca. 140-170 years B.P.) before the
appearance of high ragweed pollen counts. At the 35-40 cm level cor-
responding to the break in the ragweed curve, the P concentration is
accelerated. A slow upward increase in P concentration below the break
in the ragweed curve is also observed for the Monona core. This trend
is followed by a rapid upward increase in P, but the periodic high
sources of P from the sewage effluent discharged to Monona do not seem
to be reflected in the upper sedimentary P concentration profile. Appar-
ently the P from these sources is masked by sources of P from urban and
agricultural runoff. In Little John, Devils, North Trout and the north-
west bay of Minocqua, the "normal rate" of P and Fe change is also
nearly zero (or increases upward slightly); this is followed by an
accelerated increase in P and Fe concentration in the postcultural sed-
iments.
Little St. Germain and the southwest bay of Minocqua (both drain-
age lakes) were the only lakes examined in this study in which Mg, Al,
K and Ca-containing compounds increase in the postcultural over the
precultural sediment. The increase of Mg, Al, K and Ca-containing
compounds is correlated to the increased runoff and leaching of the
soils during the deforestation period. The core profiles indicate that
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the runoff of erosional products reached a peak approximately 40-80
years ago. The decline in erosional products after this period is
attributed to the regrowth of vegetation and timber. In the other
northern lakes studied, including Trout Lake which is a drainage lake,
the evidence from the core profiles indicates that the changes in con-
centrations of Fe, Mn, P and organic C are more pronounced than changes
in concentrations of Mg, Al, K and Ca-containing compounds during (and
after) the deforestation period.
Lake sediment cores are a particularly useful tool in assessing
how changes in the chemical composition or state.of sediment may have
affected the retention and release of nutrients historically in the
lake. If the lake sediments are considered as a part of the dynamic
trophic system, then it is worthwhile to consider not merely the reserve
of nutrients in sediments, but also how the change in chemistry brought
about by cultural activities has affected the potential for release or
retention of nutrients. For instance, the leaching studies on the Lake
Mendota marl and gyttja indicate that inorganic N release is favored in
the marl over the gyttja sediments. The limnological implication would
be that the potential existed for the oxic release of inorganic N in
precultural sediments which is similar to (or greater than ) the recent
sediments. The retentive capacity of P has increased in the postcultural
sediments of Mendota, but the aerobic release of P is slightly favored
in the gyttja over the marl sediments. The release rate of P is about. 3
times faster for the gyttja sediment, but the absolute amount of P re-
leased per gram sediment is only 1.6 times greater in the gyttja than
the marl.
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Finally, the chemical stratigraphy of lake sediment cores can
serve as a record for future investigators to follow changes 20, 50 or
100 years from now. Since the overall chemistry has been performed on
the cores from several lakes, future investigators can judiciously
select intervals along a core column to perform analyses corresponding
to certain changes.
B. Guidelines for Future Lake Sediment Coring Studies
Coring Location. The center of the lake is probably the most con-
venient reference point. The mixing of bottom sediments and the inflow
of detrital materials from the shore regions may be minimal at the cen-
tral location in a lake. Deep, closed basin lakes with flat bottom con-
tour lines probably provide the best type of coring site--i.e. Devils
Lake. In order to effectively evaluate changes in recent sediments of
drainage lakes and lakes with multiple bay areas, more than a single
core needs to be taken. Core traverses should be made in lakes whenever
possible.
Coring Apparatus. A large diameter (3^ inches) piston-operated
corer of 1 meter length provides for minimum disturbance of the core
material, sufficient sample for chemical analyses and sufficient depth
to penetrate the pre- and postcultural sediments. The reader should
refer to Wentz (1967) and Bortleson (1968) for details of the coring
apparatus used in this study.
Fractionation. The optimum interval size depends on the sedimen-
tation rate and the depth of sediment mixing. The resolution expected
in a sediment core can be estimated by making a preliminary analyses of
a given component along the core column using smaller and smaller
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240
interval sizes until the smallest interval used shows no difference in
the inflection of the profile peaks. In general, a 2-5 cm interval size
should allow sufficient detail of the chemical stratigraphy of the post-
cultural sediments. It is wise, however, to sample in as small inter-
vals as practical. The investigator always has the option to use
selected intervals and to combine sections at a later stage depending
on the physical and chemical characteristics of the core and the amount
of sample needed for analyses. The reader is referred to Davis (1967)
for techniques in sampling cores at intervals as small as 4 mm. If long
cores penetrating the depth of the postglacial column are taken, they
should be at the same site as the shallow cores in order to directly
compare the post- and precultural chemical composition and sedimentation
rates. The fractionation of the long cores should be taken in relatively
small intervals (10-20 cm).
Storage. The core samples should be stored in glass bottles at
4 C until the physical parameters such as percent moisture, bulk density
grain specific gravity and wet chemical analyses are measured or per-
formed. The investigator may consider freezing the samples for long-
term storage after the above analyses are completed. If the investi-
gator is determining various forms of an element which comprise a
fraction of the total, special precaution muse be taken to properly store
the samples. For instance, the analysis of various forms of nitrogenous
compounds may vary depending on the storage and handling of soil or
sediment samples (Bremner, 1965). Since it is not often possible to
predict changes upon storage, the best technique is to conduct tests to
determine the analytical difference between storage under certain
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241
conditions vs. immediate analysis. The reader is referred to soils
literature (Jackson, 1958) for information concerning the preservation
of samples.
Chemical Analyses. The following chemical analyses may be of
interest in evaluating the overall effects of eutrophication:
1) the biophile elements - C, N and P
2) elements influenced by redox conditions - Fe, Mn and S
3) Ca and Mg
4) elements associated with clay minerals - i.e. Al, Si and K
5) trace elements - i.e. Cu, As, Pb and Zn
6) extractable forms of cations, anions and nutrients
7) cation exchange capacity
8) pH and redox potential.
Dating Cores. Dating of recent sediments as discussed previously
is problematic; however, more research should be directed into using
tracers such as ragweed pollen, magnetic iron spherules, and man-
introduced contaminants such as Cu, As and Pb. In addition, techniques
such as Pb-210 dating and X-ray radiography need to be explored. The
reader is referred to Kendall (1969), Davis (1967), Ogden (1967) for
discussion on C-14 dating techniques. In order to arrive at a meaning-
ful first approximation of sedimentation rates, a series of C-14 dates
needs to be performed on a single core. It should be emphasized that
dates are meaningless unless accompanied by physical data of sediment
density and percent moisture.
Other Investigators. Paleolimnology as a whole is too vast a sub-
ject to be dealt with by one individual or with the view of one discipline.
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It is recommended at the start of a coring program to involve other in-
dividuals. Although reports are not yet available, various investi-
gators have obtained Lake Mendota core samples for pollen, ostracod,
diatom, trace elements and Pb,-210 dating. It is felt that the informa-
tion that these investigators will obtain will provide additional in-
sight into the use of the chemical composition of lake sediment cores
to estimate the current degree and rate of eutrophication of lakes.
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CHAPTER VII
SUMMARY
The chemical composition of 1 m sediment cores fractionated into 5
cm intervals was used to trace the recent developmental history of Lakes
Mendota, Monona and Wingra (calcareous lakes in Dane Co., Wis.); Devils
Lake (a noncalcareous lake in Sauk Co., Wis.); Little St. Germain Lake,
Trout Lake, Lake Minocqua, Weber Lake and Little John Lake (noncalcareous
lakes in Vilas and Oneida Co., Wis.). The sediment cores were analyzed
for C, P, Ca, Mg, K, Al, Fe and Mn. Organic C and carbonate C were de-
termined separately. Organic N, exchangeable ammonium and acid soluble
P determinations were performed on selected sedimentary profiles.
Ambrosia (ragweed) pollen was used to establish recent sedimentation
rates and to identify pre- and postcultural sediment in the core column.
Changes in the chemical stratigraphy of lake sediment cores are
traced to cultural activities i'n the watershed; these stratigraphic
changes are especially pronounced in the southern calcareous lakes. The
enrichment of P in the postcultural sediments of Lake Mendota is due not
only to an increase in supply of P from domestic drainage, but to an in-
crease in P retentive capacity of the postcultural sediment and to an
increase of P deposition due to the concomitant increase in Fe, Mn, K
and Al-containing compounds. The chemical stratigraphy of a 9.9 m Lake
Mendota core provided evidence that a long period of stable conditions
existed in the lake and watershed prior to the settlement period in
southern Wisconsin; the concentrations of organic C, P, Fe, Mn, Al, K,
Ca and ragweed pollen are all relatively constant over the interval 62
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244
to 990 cm. In Lake Mendota the "normal rate" of P change (before man's
influence) with sediment depth is nearly zero. At the 35-40 cm level
corresponding to the break in the ragweed curve, the P concentration is
accelerated upward to sediment-water interface. The estimated post-
2
cultural deposition rate of P (11.9 mg P/cm 7100 yr) In the center of
Lake Mendota is 5-8 times greater than the precultural interval.
A trend which is common to all the northern Wisconsin noncalcareous
lakes is an increase in organic C concentration with depth of sediment.
In several of the lakes the organic C shows a slight upward decrease be-
fore the postcultural period is initiated; this .is followed by a rapid
decline in organic C during the postcultural period. The decrease in
organic C is usually accompanied by an increase in P, Fe, Mn and/or Al,
K, Mg, Ca-containing compounds. The postcultural period is usually
marked by an increase in inorganic sedimentation rate. Changes in sed-
imentary concentrations of Fe, Mn, P and organic C are more pronounced
in three noncalcareous lakes than changes in concentrations of Mg, Al, K
and Ca-containing compounds during (and after) the deforestation period
in northern Wisconsin. The P, Fe and Mn concentration profiles are
closely related in both the pre- and postcultural deposits. The con-
centration of P in sediments is largely controlled by Fe and to a lesser
extent Mn deposition. In general, the aerobic sorption and desorption
o'f P studies indicate the sediment laid down postculturally is a more
favorable sorptive environment for P and a less favorable desorptive
environment for P than sediment laid down prior to cultural influences.
This is due primarily to the concurrent increase in Fe in the post-
cultural sediments for both calcareous and noncalcareous lakes. The
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245
postcultural sedimentation rate P (and Fe) is highest for the eutrophic
drainage lakes West Bay of Little St. Germain Lake and the southwest bay
2
of Lake Minocqua (20.5 and 14.7 mg P/cm /100 yr, respectively) and lowest
for the two oligotrophic lakers, Devils Lake and Weber Lake (2.76 and 4.06
2
mg P/cm 7100 yr, respectively).
Only in the special case of rate constant sediment accumulation can
a rate expression be derived to estimate accurately an incremental
change in nutrients to the^ lake basin. The chemical stratigraphy of
concentration-depth diagrams do, however, permit a qualitative evaluation
of the extent lakes have been influenced by man's activities. The poten-
tialities and limitations of using recent lake sediments to evaluate
cultural eutrophication of lakes are discussed.
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246
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260
APPENDIX A
Chemical Data on Lake Sediment Cores
The following information is prefaced to eliminate repetitive in-
formation in the tables and to acknowledge contributions from other in-
vestigators .
Notation on Tables
1. Depth of Sediment is depth below sediment-water interface.
2. Mean Density is the summation of the densities for all sections
divided by numbers of sections in the core.
3. Standard Deviation is derived from 5 replicate samples using N-l
degrees of freedom.
4. Percent Solids is oven-dried sediment at 105 C.
Processing Sediment
All core samples are digested by HF-HNO -HC10 except Mendota
(WC-89), Trout (WC-59) and Monona (WC-46) which were digested with
HC10 -HNO .
4 3
Acknowledgements
Determination Core Investigator
Acid Soluble P WC-89 Wentz (1967)
Mn WC-89 Delfino (1968)
Cu WC-101 Sanchez (1970)
-------
LAKE'MENDOTA (WC - 89)
Date Collected: 26 October 1966 Location: 23.2m of Water, Center Deep Basin
Depth of
Sect.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Mean
Sediment
(cm)
0- 5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
,0-55
55-60
60-65
65-70
70-75
75-80
80-85
85-90
90-95
Density
%
Solids
11.1
16.2
19.4
19.0
17.3
16.4
16.1
16.3
14.9
14.2
11.9
12.9
13.0
12.9
13.9
13.2
12.9
13.1
13.7
1.08
Total
C
118
127
114
93.5
99.0
97.0
99.0
109
112
119
121
122
114
113
113
126
128
123
122
Org-C
80.5
89.5
82.2
63.3
67.2
64.3
66.9
74.2
76.0
81.5
88.3
83.9
70.8
62.0
54.3
68.4
72.2
62.7
66.3
co3-c
37.5
37.5
31.8
30.2
31.8
32.7
32.1
34.8
36.0
37.5
J2.7
38.1
43.2
51.0
58.7
57. v,
55.8
60.3
55.7
Org-N
9.95
9.38
8.73
7.01
6.49
6.65
7.06
8.15
8.20
8.44
8.38
8.13
5.74
7.00
7.31
8.05
7.10
6.82
7.16
NH.-N
4
__»
0.41
0.46
0.54
0.52
0.49
0.49
0.49
0.47
0.50
0.40
0.34
0.41
0.35
0.41
0.39
0.35
0.40
'P
1.79
1.79
1.31
1.64
1.68
1.96
1.74
1,55
1.23
1.16
1'.09
0.99
0.89
0.90
0.92
0.97
0.87
0.85
0.87
Acid
Sol.
P
__
0.88
0.82
0.72
0.86
0.98
0.88
0.96
0.70
0.73
0.64
0.59
0.60
0.61
0.65
0.60
0.61
0.62
0.59
Fe
18.9
18.9
22.8
24.4
22.8
22.3
21.0
18.2
16.4
16.4
15.5
13.8
12.3
9.83
8.50
5.90
7.50
6.82
6.30
Mn
1.50
1.28
1.08
1.12
1.12
1.20
1.04
0.96
0.72
0.72
0.64
0.56
0.48
0.44
0.40
0.32
0.34
0.38
0.34
Ca
125
125
106
101
106
109
107
116
120
125
109
128
144
1-7-0
196
192
186
201
186
Mg
13.4
12.0
10.5
10.4
ID. 6
10.6
10.9
10.7
10.6
10.3
9.70
10.4
11.2
12.1
10.4
9.00
9.55
8.90
10.6
K
WM.
9.85
10.3
11.2
10.6
10.5
9.93
8.77
8.83
8'. 60
8.53
7.70
7.43
6.13
3.00
2.75
2.10
1.99
2.30
a\
-------
LAKE MENDOTA (WC - 86)
Date Collected: 8 October 1966 Location: 18.3m of Water, University Bay
Sect.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Depth of
Sediment
(cm)
0- 5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
80-85
85-90
90-95
95-100
%
Solids
11.2
24.7
25.0
23.5
24.2
22.8
23.1
27.9
22.9
22.6
24.1
23.1
18.8
17.8
17.8
18.1
18.8
19.1
18.2
15.5
Standard Deviation
Standard Deviation
Total
C Org-C
110 78.2
106 76.6
92.5 62.2
91.5 63.3
109 80.8
111 79.2
108 76.2
119 86.3
104 71.6
106 67.0
119 71.3
153 76.5
146 69.5
126 51.0
128 56.6
136 64.0
130 52.4
131 55.1
128 53.2
94.0
162.4
Acid Sol.
co3-c
31.8
29.4
30.3
28.2
28.2
31.8
31.8
32.7
32.4
39.0
47.7
65.4
76.5
76.5
75.0
71.0
72.0
77.6
75.9
74.8
P
1.60
1.32
1.42
1.17
1.21
1.13
1.30
1.13
1.10
1.00
1.02
1.11
0.945
1.11
1.01
0.815
0.787
0.949
1.07
0.963
90.017
160.017
P
0.770
0.583
0.556
0.591
0.587
0.548
0.548
0.543
0.529
0.529
0.532
0.605'
0.567
0.569
0.593
0.540
0.538
0.571
0.594
90.011
160.055
Fe
22.3
23.4
21.9
22.0
21.0
20.1
17.2
16.6
16.2
14.3
12.5
9.21
5.80
7.55
8.08
7.15
7.15
6.45
6.39
6.60
90.40
160.36
Mn
mg/g
1.06
0.880
0.867
0.780
0.705
0.737
0.655
0.605
0.570
0.534
0.512
0.521
0.460
0.453
0.430
0.435
0.437
0.420
0.420
0.437
90.016
160.010
Ca Mg
106 13.7
98 14.3
101 14.0
94 13.3
94 15.1
106 14.9
106 14.3
109 14.7
108 14.7
130 14.8
159 16.8
218 16.8
255 13.4
255 12.9
250 12.6
238 12.8
240 13.0
259 12.8
253 12.7
249 12.5
Q Q
yl.l y 0.17
16i.i 16 o.o
Al
46.2
50.4
47.9
47.8
46.4
45.6
43.6
43.2
42.3
39.8
37.2
29.1
15.9
15.2
14.7
17.9
17.8
14.8
16.0
14.0
9 2.3
16 0.32
K
11.3
11.9
12.1
12.0
11.7
11.2
11.1
10.9
11. 1
9.50
6.53
6.53
3.04
3.10
2.71
3.67
3.57
3. 10
2.80
3.00
90.14
160.06^
-------
LAKE MENDOTA (WC-84)
Date Collected: 8 October 1966 Location: 11.2m of Water, University Bay
Sect.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Depth of
Sediment
(cm)
0- 5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
80-85
85-90
90-95
95-100
%
Solids
27.1
28.7
31.0
35.1
34.3
30.2
31.6
34.0
34.3
29.4
29.4
29.0
25.6
27.0
25.6
27.5
23.9
25.2
26.0
28.2
Standard Deviation
Sf-;inrl;
irrl DnvLlt]
'on
Total
C
128
122
109
103
127
132
136
134
130
148
154
148
147
150
155
167
167
165
163
173
43.2
144.0
Org-C
100
94.3
82.6
78.7
99.6
102
106
105
100
119
120
102
91.5
89.0
91.4
89.0
88.0
88.8
92.5
94.0
co3-c
28.0
27.7
26.4
24.3
27.4
29.6
29.9
29.4
29.8
29.4
34.5
46.2
55.5
61.0
63.6
78.0
79.0
76.2
70.5
77.0
P
mg/g
1.19
1.18
1.10
1.09
1.13
1.10
1.12
1.05
1.05
1.06
1.06
0.990
0.976
0.968
0.928
0.908
0.886
0.818
0.820
0.838
30.039
130.017
Fe
20.1
20.5
20.0
21.5
21.3
20.2
19.8
19.2
19.0
17.0
15iO
12.9
11.0
9.35
8.93
6.70
6.25
6.33
7.38
6.85
30.38
130.27
Mn
0.626
0.626
0.602
0.602
0.644
0.667
0.714
0.703
0.667
0.588
0.524
0.506
0.497
0.488
0.486
0.450
0.454
0.447
0.506
0.501
30.0010
130.0020
Ca
93.3
92.3
87.8
81.0
91.5
98.5
99.8
98.0
99.5
98.0
115
154
185
203
212
260
263
254
235
257
30.63
13 22
Mg
17.5
17.4
17.5
17.4
17.6
16.3
16.5
16.1
15.9
15.3
15.2
16.5
17.1
16.5
16.9
15.8
16.2
15.9
16.1
16.5
3 0.16
13 0.95
Al
38.5
38.2
41.3
43.0
40.8
38.2
37.0
36.5
36.4
33.0
30.5
26.7
19.8
16.6
15.6
9.80
9.40
9.04
9.52
9.61
30.37
130.20
K
10.6
11.0
11.7
12.6
11.7
10.5
10.7
10.3
10.6
9.90
8.90
8.15
6.77
5.20
5.13
2.83
2.73
2.60
2. '60
2.78
30.05i
130.54
-------
LAKE MENDOTA (WC-82)
Date Collected: 8 October 1966 Location: 3.8 m of water, University Bay
Depth of
Sect.
No.
1
2
3
'4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Sediment %
( cm)
0-5
5-10
10-15
15-20
20-25
25-30
30-35
55-40
;+0-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
80-85
85-90
90-95
95-100
Solids
26.6
34.4
29.8
27.1
31.6
38.6
38.2
33.6
33.8
34.1
45.3
53. 1
48.3
43.1
44.4
52.4
52.3
53.5
59.5
61.8
Total
C
105
106
119
134
145
122
121
125
123
126
108
--
102
119
114
93.4
96.2
91.0
81.8
86. 1
Org-C
77.0
79.2
64.0
69.2
76.6
55.5
43.0
43.9
48.9
65.7
44.2
--
45.4
55.9
54.5
46.4
56.0
46.7
37.8
42.6
CO -C
3
28.0
26.8
55.0
64.8
68.4
66.5
78.0
81. 1
75.1
60.3
63.8
37.4
56.6
63.1
59.5
47.0
40.2
44.3
44.0
43.5
P
0.806
0.868
0.688
0.518
0.550
0.560
0.632
0.416
0.454
0.490
0.410
0.394
0.455
0.472
0.470
0.468
0.428
0.408
0.392
0.440
Fe
13.1
13.1
9.52
4.80
4.??
5.03
3.98
3.80
4.27
4.73
4.85
6.0,4
5.55
5.17
5. 17
5.42
5.80
5.78
5.05
5.91
Mn
mp/p
0.510
0.500
0.491
0.492
0.459
0.422
0.400
0.386
0.374
0.374
0.366
0.344
0.378
0.410
0.397
0.368
0.364
0.342
0.306
0.315
Ca
93.3
89.5
183
216
228
222
260
271
251
201
213
--
189
211
198
157
134
148
147
145
Mg
17.6
15.3
13.5
10.8
10.6
13..5
13.5
12.0
12.9
11.8
17.3
18.2
18.7
15.4
16.1
17.4
16.2
19.5
20.0
21.1
Al
34.4
34.4
24.7
11.0
10.7
12.5
12.5
10.7
12.2
12.2
15.3
19.3
16.3
13.5
14.0
17.0
17.0
18.0
17.7
19.1
K
10.7
10.3
6.55
2.95
2.37
3.74
3.33
2.57
3.15
3.22
4.81
7.25
5.59
3.96
4.59
6.27
6.66
7.07
7.05
7.42
*i
Standard Deviation
Standard Deviation
3.0
'0.019
0.23
0.0011
'4.3
15
3.2
13
0.011
13
0.0028
13
0.0028
13
13
4.5
0.54
!
0.48
0.34
13
0.0
0.39
13
0. 11
-------
LAKE MENDOTA (WC-95)
Date Collected: 14 November 1968 Location: 23 m of Water, Center Deep Basin
Total
C Org-C C03-C
Fe
Mn
Ca
Mean Density
1.08
14.
Standard Deviation 6.4
Al
52
51
50
49
48
47
43
41
39
35
31
27
23
18
14
12
10
6
3
1
0-11
11-22
22-42
42-62
62-82
82-102
157-177
197-217
237-257
312-332
394-414
474.494
554-574
639-659
718-738
758-778
798-818
880-900
935-950
970-990
12.4
20.7
15.1
15.8
12.3
12.8
15.6
16.1
17.2
17.5
16.9
16.5
17.4
17.9
20.7
19.9
19.2
17.9
16.3
20.8
122
122
117
121
133
130
127
123
136
141
133
131
123
131
136
132
122
118
119
108
92.4
88.7
87.4
88.0
75.4
65.0
62.1
59.5
68.5
77.2
68.9
66.9
61.5
69.9
68.2
66.9
59.0
63.5
50.6
53.0
29.6
33.3
29.6
33.0
57.6
65.0
64.9
63.5
67.5
63.8
64.1
64.1
61.5
61.1
67.8
65.1
63.0
54.5
68.4
55.0
"&' t
1.86
2.06
1.99
1,47
0.940
0.880
0.913
0.878
0.873
0.875
0.834
0.801
t
0.820
0.866
0.852
0.870
0.825
0.806
0.806
0.820
22.0
16.3
10.0
9.25
7.75
7.75
6.80
5.73
5.10
5.13
5.20
6.15
5.95
6.00
5.73
6.60
5.45
6.90
1.09
1.12
1.23
0'.712
0.433
0.400
0.365
0.402
0.370
0.338
0.332
0.330
0.330
0.352
0.395
0.364
0.332
0.328
0.400
0.360
98.5
111
98.5
110
192
217
216
212
225
213
214
214
205
204
226
217
210
182
228
183
10.8
10.8
10.8
8.78
3.11
2.23
2.43
2.20
2.01
2.01
1.68
1.55
1.27
1.79
1.69
2.09
2.00
2.30
1.68
2.04
38.2
38.5,
41.5
30.0
13.0
10.4
11.4
10.8
11.7
10.4
8.00
7.25
6.55
8.05
8.00
8.80
8.55
9.85
8.25
10.2
ro
-------
266
MONONA (WC - 46)
Collected: 30 June 1966
Location: 15.9m of Water, North Central Basin
Depth of
Section Sediment
Number (cm)
P
Fe
Mn
. Ca
mg/g
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
0- 5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
80-85
85-90
90-95
95-100
100-105
1.83
1.71
1.51
1.60
1.66
1.77
1.92
1.44
1.34
1.33
1.17
1.17
1.22
1.23
1.12
1.06
0.910
0.785
0.756
0.744
0.764
18.5
17.0
17.4
20.3
20.0
20.1
19.3
16.5
13.2
12.0
10.9
10.0
7.70
7.80
7.33
7.23
6.50
5.30
5.53
5.20
5.73
0.760
0.717
0.673
0.720
0.740
0.812
0.882
0.784
0.695
0.707
0.494
0.477
0.458
0.433
0.418
0.383
0.376
0.364
0.377
0.372
0.376
113
114
122
121
114
108
106
144
172
157
172
1.82
239
220
223
219
212
204
191
187
191
Mg
14.0
12.7
11.4
11.0
11.0
10.5
10.4
12.2
11.5
11.0
11.5
11.5
12.1
11.0
11.2
11.0
10.6
10.2
9.55
9.35
9.55
K
2.97
2.77
2.69
2.85
2.89
3.04
3.31
2.57
1.76
1.76
1.80
1.19
0.82
0.76
0.67
0.71
0.69
0.63
0.62
0.60
0.64
Al
1.90
1.86
1.86
1.91
2.06
2.26
2.44
1.84
1.30
1.37
1.37
1.09
0.63
0.59
0.58
0.58
0.57
0.54
0.52
0.50
0.69
-------
LAKE MONONA (WC - 101)
Date Collected: 10 June 1969 Location: 21 m of Water, Deep Area
Depth of
Sect. Sediment
No. (en)
1 0-5
2 5-10
3 10-15
4 15-20
5 20-23
6 25-30
7 30-35
8 35-40
9 40-43
10 45-50
11 50-55
12 55-60
13 60-65
14 65-70
15 70/-75
16 75-80
17 80-85
18 85-90
19 90-95
20 95-100
Mean Density
Standard Deviation
Standard Deviation
X
Solids
11.8
14.9
15.0
15.8
17.9
19.1
19.2
21.9
23.0
22.7
22.4
23.2
22.8
23.6
22.1
20.6
22.2
23.7
22.7
1.09
Total
C
136
133
131
136
139
136
129
124
124
125
127
123
125
120
113
121
118
120
133
136
62.4
160.90
Org-C
101
99.0
102
107
107
102
98.6
97.4
94.5
96.6
98.2
97.0
95.6
93.1
86.1
92.2
86.0
91.9
97.2
101
COj-C
35.4
34.0
29.5
29.1
32.1
33.6
30.4
26.6
29.5
28.4
28.8
26.0
29.4
26.9
26.9
28.8
32.0
28.1
35.8
.35.2
P
1.74
1.76
1.67
1.71
1.67
1.65
1.60
1.63
1.64
1.58
1.70
1.70
1.51
1.77
1.83
1.48
1.32
1.45
1.69
1.43
30.030
Fe
18.2
17.8
17.6
17.4
13.6
16.6
17.8
17.6
15.9
16. 1
17.2
15.9
16.2
17.5
17.8
17.4
16.7
15.7
13.1
10.9
30.73
Hn
0.807
0.809
0.742
0.709
0.714
0.737
0.752
0.770
0.809
0.802
0.852
0.857
0.818
0.883
0.832
0.793
0.702
0.764
0.865
0.734
30.0038
130.0070
Cft
118
113
98.2
97.0
107
112
102
88.7
98.3
94.5
96.0
86.5
98.1
89.5
89.5
95.6
107
93.7
120
118
3 4.5
1312
*
17.4
16.0
14.5
13.1
12.7
13.3
13.1
12.3
12.5
12.2
13.0
11.5
13.2
13.1
13.3
12.8
12.9
11.9
12.4
11.7
30.59
131.5
K
9.04
9.05
9.24
8.67
8.20
8.26
8.56
9.26
9.13
8.98
9.13
9.20
9.29
9.84
9.90
9.08
9.04
9.06
7.05
6.21
30.066
130.91
Al
31.4
31.1
32.2
31.2
29.8
31.1
32.2
33.9
33.1
32.8
35.2
35.8
35.0
37.0
37.2
34.3
34.5
33.8
25.0
22.2
30.29
130.042
s"-s
2.36
2.22
2.32
1.98
2.50
1.50
1.59
2.04
1.97
2.39
2.58
--
«U-,
0.22
0.30
0.20
0.62
0.67
0.67
0.84
0.81
0.83
0.86
0.88
0.83
0.87
0.94
0.88
0.93
0.96
0.90
170.050
Cu
0.246
0.271
0.260
0.357
0.410
0.633
0.588
0.358
0. 106
0.055
0.040
0.039
20.0038
170.0059
NJ
-------
LAKE WINGRA (WC - 92)
Dote Collected: 10 May 1968 Location: 3.4 m of Water
Depth of
Sect. Sediment
No. (cm)
1 0-5
2 5-10
3 10-15
4 15-20
5 20-25
6 25-30
7 30-35
8 35-10
9 40-45
10 45-50
11 50-55
12 55-60
13' 60-65
14 65-70
15 70-75
16 75-30
17 80-85
18 85-90
Mean Density
Standard Deviation
Standard Deviation
Standard Deviation
:
Solids
8.8
16.1
20.1
21.7
21.2
22.3
23.1
23.4
23.8
24.7
23.7
23.8
21.1
17.5
16.8
18.6
18.4
20.5
1.13
Total
C
144
148
146
144
134
125
128
132
137
134
142
138
145
169
177
168
174
176
57.0
168.6
Org-C
71.4
78.0
78.5
74.4
64.0
55.0
59.0
57.5
67.0
65.0
67.5
69.0
70.5
37.5
92.0
72.5
78.1
80.5
co3-c
72.6
70.0
67.5
69.6
70.0
70.0
69.0
74.5
70.0
69.0
74.5
69.0
74.5
81.5
85.0
95.5
95.9
95.5
Org-N
8.34
8.17
7.90
7.77
7.08
7.03
7.20
6.63
6.74
6.60
7.96
7.36
8.44
10.3
10.6
8.98
9.88
9.65
50.36
N1IA-N
0.092
0.048
0.061
0.073
0.077
0.14
0.14
0.18
0.15
0.18
0.21
0.21
0.18
0.22
0.20
0.21
0.23
0.23
40.009
U0.014
150.040
P
«E/E
0.633
0.641
0.578
0.619
0.538
0.486
0.480
0.461
0.450
0.482
0.507
0.596
0.534
0.576
0.539
. _
0.461
0.470
50.0032
U0.006
160.031
Acid
Sol-P
0.277
0.283
0.312
0.302
0.284
0.283
0.300
0.294
0.311
0.311
0.359
0.373
0.396
0.381
0.394
.
0.371
0.364
50.0010
160.0087
Fe
8.82
8.70
8.22
8.25
8.04
7.82
7.70
0.26
7.85
8.05
7.96
7.75
6.69
3.95
2.50
2.00
1.89
2.30
50.20
n0.33
160.078
tin
0.560
0.568
0.548
0.562
0.562
0.578
0.578
0.57S
0.572
0.607
0.622
0.637
0.625
0.400
0.312
0.276
0.287
0.275
50.0
no.ni2
16o.o
Ca
242
233
225
232
233
233
230
248
233
230
248
230
248
272
283
318
319
318
54.4
168.0
Mg
10.9
10.8
10.5
10.6
10.2
9.30
9.75
9.43
9.43
9.55
9.10
0.84
8.00
7.05
6.15
6.02
6.00
6.40
50.22
U0.22
160.59
K
5.54
5.54
5.23
5.50
5.67
5.45
5.48
5.38
5.18
5.22
5.45
5.23
4.41
1.55
O.S2
0.53
0.52
0.76
50.13
U0.030
160.059
Al
29.9
30.6
30.9
32.0
31.3
30.2
30.0
31.0
30.4
30.4
30.5
29.2
25.7
14.1
9.0
0.2
3.0
9.1
50.2H
U0.21
160.17
CO
-------
Date Collected:
DEVILS LAKE (WC-75)
13 August 1966 Location: 13.1 m of Water, Center of South Basin
Org-C
Fe
Mg
K
16
3.5
4.7
0.023
0.94
0.0023
0.087
0.17
0.45
Al
1
2
3
.4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
0-5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
80-85
85-90
90-95
14.6
15.2
15.9
14.4
13.3
17.7
14.1
14.8
17.5
18.3
14.7
12.7
12.3
12.2
15.7
12.6
11.9
11.9
13.3
73.2
__
88.8
121
118
109
108
102
120
115
118
128
150
139
134
141
158
152
143
2.39
1.41
1.24
1.24
1.17
1.12
. ..
1.11
1.05
1.06
1.02
1.00
0.894
0.904
0.934
0.924
0.984
0.988
0.936
37.1
33.8
32.2
27.5
28.2
26.5
25.4
27.7
28.7
27.6
27.9
24.6
21.8
22.7
23.4
22.4
21.6
20.2
21.2
0.454
0.351
0.312
0.296
0.283
0.276
0.284
0.265
0.260
0 . 258
0.261
0.237
0.221
0'. 220
0.227
0.216
0.216
0.209
0.217
o
2.50
2.18
2.20
1.95
1.91
1.99
2. 13
1.82
1.91
1.52
1.85
1.58
1.25
1.60
1.70
1.87
1.78
1.91
1.81
4.75
4.85
4.84
4.18
4.13
4.28
4.32
4.33
4.19
4.20
4.31
3.79
3.41
3.35
3.51
3.37
3.37
3.32
3.41
13.9
13.9
12.5
8.98
8.92
10.1
10.6
9.96
9.24
9.23
8.66
8.93
8.57
8.61
8.61
9. 10
8.50
8.65
8.78
90.3
92.4
95.4
89.2
86.0
87.4
86.3
82.5
82.4
82.4
82.6
74.6
65.3
63.5
65.4
62.7
58.5
58.7
58.9
4.2
ro
o>
vO
-------
TROUT
Date Collected: 9 August 1966
LAKE (WC-59)
Location: 32.6 m of Water, South Bay
Sect.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Depth of
Sediment
(cm)
0-5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
80-85
85-90
90-95
95-100
100-105
%
Solids
3.05
4.05
4.29
6.06
6.47
6.64
6.78
6.17
5.99
6.34
6.65
6.79
7.61
7.42
7.35
7.73
8.05
8.18
8.02
8.32
8.24
Org-C
161
148
135
141
144
147
175
187
194
155
170
183
179
202
202
208
202
211
203
180
166
Org-N
18.2
15.8
15.0
13.8
14.2
14.4
16.5
18.0
18.4
15. 1
16.1
17. 1
16.7
17.8
17.7
17.9
18.2
17.9
18.3
16.1
16.1
NH -N
^
0.24
0. 16
0. 18
0. 18
0.23
0.25
0.26
0.24
0.24
0.24
0.29
0.27
0.29
0.30
0.31
0.34
0.33
0.33
0.31
0.22
P
7.88
6.73
5.05
5.37
5.00
5.21
5.20
2.96
2. 15
4.40
6.70
5.18
5.40'
4.30
4.50
4.50
5.50
4.07
3.00
5.50
6.01
Acid
Sol.
P
mp/r>
7.00
5.81
4.55
5.20
4.26
4.69
4.85
2.80
1.93
4.35
6. 10
4.68
4.93
3.55
3.93
4.43
5.05
2.85
2.33
5.35
5.80
Fe
66.3
57.2
52.5
51.3
50.7
53.7
61.8
51.0
44. 1
43.0
60.0
60.5
60.0
58.8
62.8
59.3
64.5
58.1
54.0
60.0
58.4
Mn
4.02
3.46
2. 13
2.37
2.30
2.58
2.69
1.94
1.59
2.37
3.25
2.58
2.72
2.43
2.58
2.62
2.90
2.13
1.97
2.90
2.50
Ca
3.52
3. 10
3.00
2.98
2.98
3.10
4.30
4.00
4.46
2.93
3.86
3.36
4.85
4.62
3.60
3.35
3.46
3.46
3.33
3.70
3.36
Mg
2.50
2.72
2.58
2.65
2.28
2.20
2.30
2.27
2.31
1.73
2.23
2.49
2.66
2.72
2.72
2.82
2.93
2.90
2.70
2.56
2.51
K
1.47
1.67
1.42
1.70
1.22
1.06
1.02
1.04
1. 10
0.80
0.98
1.22
1. 16
1.30
1.39
1.52
1.68
1.56
1.48
1.48
1.47
Mean Density
1.04
-------
Date Collected:
TROUT LAKE (WC-60)
9 August 1966 Location: 26 m of Water, North Bay
Sect.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Depth of
Sediment
(cm)
0-5
5-10
10-15
15-20
20^25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
80-85
85-90
90-95
95-100
%
Solids
4.18
6.63
6.85
7.54
7.27
7.08
6.67
7.40
7.48
7.57
7.66
7.37
8.40
8.06
8. 10
8. 13
7.80
8.26
8.54
7.78
Org-C
144
134
142
135
145
167
209
200
203
200
217
226
237
232
228
220
229
240
240
234
P
9.94
7.43
4.78
4.33
4.25
3.65
2. 15
2.08
1.78
2.68
2.14
1.55
1.44
1.16
1.36
1.67
1.55
1.27
2.98
1.46
Fe
69.5
58.9
47.3
45.8
46.3
44.8
42.3
41.0
38.7
48.9
50.0
44.3
36.7
32.5
34.3
42.5
36.1
34.4
43.9
36.0
Mn
mp / P, .
3.85
2.86
1.96
1.98
1.72
1.70
1.34
1.30
1. 18
1.51
1.38
1.21
1.12
1.03
1.05
1.23
1.21
1.07
1.56
1.09
Ca
2.26
2.49
2.31
2.19
2.32
2.79
3.35
3.29
3.74
3.29
3.39
3.45
3.61
4.25
3.60
4.19
3.99
3.90
3.85
3.72
Mg
3.01
3.31
3.15
3.29
3.32
3.35
2.93
3.16
3.22
3.31
3.64
4.00
4.03
4.17
4.33
4.24
3.95
3.89
4.00
3.69
K
4.34
4.95
4.74
4.98
4.12
4. 19
3.76
3.69
3.89
3.82
4.33
5.14
5.41
5.85
6.20
5.79
5.84
5.55
5.40
4.80
Al
25.8
26.8
26.5
27.0
23.5
25.5
23.0
22.5
23.9
23.7
26.7
30.5
31.4
36.0
37.0
34.5
32.5
30.3
29.5
27.0
Mean Density
Standard Deviation
Standard Deviation
1.02
16
'4.9
5.3
0.035
5.9
13
0.022
13
0.025
0.011
0. 13
0.21
0.32
0.099
13
13
0.20
0.29
13
0.22
ro
-vl
-------
LITTLE ST. GERMAIN (WC - 92)
Date Collected: 12 March 1967 Location: 15.6 m of Water, Center of West Bay
Sect.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Depth of
Sediment'
(cm)
0- 5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
80-85
85-90
%
Solids
2.45
5.06
6.15
6.19
6.46
*.56
6.15
6.52
5.85
5.53
5.49
6.13
6.09
6.32
6.26
6.36
6.49
6.80
Org-C
143
126
123
141
143
150
151
183
222
210
191
185
218
224
231
225
228
240
P
10.1
11.1
9.20
7.36
7.60
7.12
7.80
10.5
14.7
13.9
10.8
11.7
14.5
15.1
16.5
16.3
15.8
15.4
Fe
102
108
99.3
81.7
77.5
73.5
83.0
88.5
102
106
89.0
97.3
108
109
117
116
113
107
Mn
1.61
1.39
1.39
1.27
1.07
0.90
1.15
1.41
2.09
2.19
1.76
1.80
2.55
2.34
2.74
2.80
2.54
2.60
Ca
mg/g
0.48
0.43
0.67
0.70
0.73
0.87
0.62
0.54
0.55
0.56
0..53
0.54
0.44
0.50
0.55
0.42
0.44
0.46
Mg
2.04
1.91
3.13
2.77
2.54
2.86
2.26
2.02
1.69
1.51
1.87
1.42
1.51
1.61
1.61
1.44
1.78
1.87
K
3.15
3.04
4.09
3.87
3.80
3.95
3.65
2.80
1.93
1.85
2.08
1.83
1794
2.20
2.15
1.88
2.30
2.65
Al
13.8
13.2
16.9
15.7
15.7
16.2
16.1
12.3
9.15
8.65
8.94
8.17
8.64
9.62
9.68
8.75
10.3
11.9
Mean Density 1.02
Standard Deviation
'2.2
18
0.13
18
0.0
18
0.011
18
0.014
18
0.079
18
0.016
18
0.091
-------
LITTLE ST. GERMAIN (WC - 56)
Date Collected: 9 August 1966 Location: 7.0 m of Water, South Bay
Solids Org-C
Fe
Mn
Ca
Mg
Mean Density
Standard Deviation
1.02
12
2.8
11
0.22
11
0.75
11
0.0083
11
0.71
11
2.0
K
11
0.080
Al
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
80-85
3.10
3.84
4.23
4.39
5.44
6.05
6.66
6.17
5.68
5.73
6.38
5.90
6.28
6.21
6.28
215
223
226
236
232
210
202
212
212
198
215
233
232
237
235
7.46
7.45
7.50
6.42
4.31
4.83
3.88
3.88
4.13
4.61
6.79
9.88
10.1
9.65
12.1
67.7
64.4
65.0
56.0
40.6
39.1
34.5
34.0
32.7
31.3
42.1
50.7
51.2
49.5
56.2
0.540
0.506
0.514
0.414
0.306
0.284
0.270
0.270
0.273
0.287
0.377
0.571
0.672
0.562
0.648
1.19
1.18
1.73
1.71
1.47
1.10
1.54
0.921
0.910
0.765
0.682
0.620
0.724
0.631
0.532
2.43
2.43
2.48
2.62
2.70
2.35
2.16
1.89
1.82
1.68
1.71
1.20
1.20
1.07
1.06
4.02
4.09
4.15
4.18
4.51
4.27
3.58
3.51
3.07
2.84
3.09
1.60
2.05
1.26
1.31
16.8
16.8
17.9
17.9
17.9
18.6
16.6
16.4
14.1
14.1
14.1
10.7
9.60
9.50
9.00
11
0.0
-------
LAKE MINOCQUA (WC-51)
Date Collected: 8 August 1966 Location: 10.7 m of Water, N. W. Bay
Mean Density
Standard Deviation
Solids Org-C
Fe
Mn Ca
i°§/g
Mg
1.04
3.7
K
Al
1
2
3
4
5
6
7
8
9
10
0- 5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
5.06
6.89
7.09
7.93
8.75
8.68
8.54
8.40
8.57
8.71
148
160
171
173
180
170
J87
186
179
189
7.94
5.77
3.68
2.84
2.94
3.38
3.01
2.75
3.16
3.00
54.4
50.9
45.8
43.6
44.3
43.5
41.8
41.1
41.1
40.9
0.804
0.665
0.540
0.495
0.503
0.567
0.542
0.506
0.544
0.512
2.09
2.42
2.49
2.49
2.64
2.60
2.65
2.66
2.57
2.45
3.37
3.67
3.58
3.55
3.52
3.73
3.92
3.92
3.84
3.73
7.42
8.70
9.24
9.24
9.41
9.72
8.87
8.83
9.05
8.46
26.2
30.2
30.0
29.4
29.4
30.2
29.6
29.6
30.3
30.2
-------
LAKE MINOCQUA (WC-52)
Date Collected: 8 August 1966 Location: 13.7 m of Water, Middle of S.W. Bay
Sect.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
Depth of
Sediment
(cm)
0- 5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
%
Solids
5.00
6.45
6.66
7.41
7.62
7.80
7.80
7.28
7.19
7.59
7.31
6.64
7.24
Org-C
139
123
119
125
131
143
153
154
150
151
156
146
153
P
9.23
9.55
7.07
5.18
5.60
6.40
5.82
6.21
7.02
6.74
8.06
8.49
9.19
Fe
60.3
70.8
61.5
51.0
49.3
47.8
40.8
40.0
41.3
39.3
46.3
48.8
53.5
Mn
mg/g>
1.97
1.90
1.59
1.26
1.23
1.30
1.25
1.20
1.21
1.24
1.38
1.20
1.55
Ca
1.58
1.55
T.79
2.05
2.04
2.06
2.13
1.49
1.52
1.35
1.30
1.32
1.06
Mg
3.36
3.30
3.32
3.34
3.31
2.71
2.09
2.05
1.88
1.72
1.85
1.65
1.78
K
5.20
5.86
6.96
7.39
7.32
7.31
3.68
3.39
3.20
3.02
2.89
2.58
2.64
Al
30.5
33.4
37.5
38.1
38.3
26.0
16.4
15.2
15.3
13.3
13.0
10.5
10.5
Mean Density
Standard Deviation
1.02
3.8
N5
-v)
Ln
-------
WEBER LAKE (WC-66)
Date Collected: 11 August 1966 Location: 12.6 ra of Water, Center of Lake
Sect.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Depth of
Sediment
(cm)
0- 5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
80-85
85-90
90-95
%
Solids
3.82
4.82
4.12
5.11
5.30
5.42
5.69
4.75
.5.25
5.00
4.82
4.91
5.38
6.01
5.14
5.54
5.44
5.44
Org-C
246
269
312
299
264
289
322
320
329
325
310
367
362
337
299
300
300
319
P
2.85
2.83
3.40
3.15
3.14
3.27
3.38
3.39
3.81
3.95
3.09
2.71
2.90
3.20
3.26
2.89
3.09
3.09
Fe
14.2
12.6
9.87
10.9
11.7
11.3
10.2
10.5
11.3
10.5
10.6
10.2
10.3
11.4
12.7
12.9
12.9
12.1
Mn
mg/g
0.253
0.228
0.209
0.210
0.224
0.234
0.256
0.290
0.314
0.300
0.300
0.320
0.318
0.320
0.286
0.286
0.292
0.290
Ca
0.830
0.656
0.502
0.552
0.595
0.589
0.680
0.730
0.838
0.678
0.845
1.08
1.26
1.12
0.951
0.860
0.947
0.920
Mg
2.90
2.63
1.91
2.38
2.66
2.56
2.07
1.95
1.87
2.18
2.58
1.99
2.10
2.29
2.89
2.80
1.43
1.61
K
8.15
7.31
5.11
6.00
6.95
6.64
5.75
5.47
5.65
5.29
6.33
4.75
4.97
5.51
6.65
6.66
6.68
5.97
Al
33.0
30.1
24.0
28.8
32.6
26.5
22.6
21.9
23.9
26.8
31.5
25.0
25.1
28.8
34.7
33.0
34.2
30.7
Mean Density
Standard Deviation
Standard Deviation
1.02
13
14
'3.9
0.029
0.26
0.0
0.038
'0.16
0.13
0.71
-------
277
LITTLE JOHN LAKE (WC - *»7)
Dtte Collected; 11 August 1966 Location; 5 of Water, Center "f '^ke
Sect.
No.
1
2
1
4
5
6
7
1
10
11
12
13
15
16
17
18
15
21
23
25
27
29
31
33
35
Depth of
SedUent
(cm)
0- 5
5-10
10-15
15-20
20-25
25-30
30-35
40-45
*5-50
50-55
55-60
60-65
70-75
75-80
80-85
»5-»0
100-105
110-115
120-125
130-135
14O-145
150-155
160-165
170-175
Hun Penalty
Standard Deviation
I
Solids
3.10
3.54
J.85
3.51
4.20
4.46
3.87
3.96
4.19
3.71
3.74
4.10
5. JO
5.23
5.28
4.75
4.52
5.32
5.60
6.51
5.81
6.01
6.13
6.17
7.00
1.03
Standard Deviation
Ort-C
232
240
260
268
268
296
334
345
347
364
364
349
351
326
310
320
309
306
334
353
338
346
320
269
155
287
56.6
255.5
r
4.23
4.26
4.08
3.89
3.12
2.44
2.00
1.99
2.21
1.16
1.6*
1.79
1.71
1.32
1.52
1.50
2.03
1.68
1.47
1.52
1.35
1.19
1.02
0.920
1.17
1.14
360.032
Fe
59.3
57.9
49.7
41.5
38.6
40.5
37.1
*4.3
34.9
35.3
28.6
36.*
34.9
40.1
32.8
38.1
42.6
35.9
32.0
34.5
25.5
21.0
22.4
14.4
It. 8
11.7
Mn
1.03
0.903
0.820
0.744
0.656
0.570
0.512
0.500
0.496
0.464
O.US
0.450
0.439
0.*32
0.432
0.457
0.522
0.434
0.430
0.470
0.4*1
0.369
0.368
0.30*
0.282
0.305
360.002«
Ca
n/t
2.10
1.76
1.76
2.08
2.73
2.72
3.28
3.18
3.25
3.41
2.98
3.27
2.78
3.14
3.63
2.92
2.67
2.84
3.03
2.94
2.90
2.57
2.84
2.39
2.3*
1.77
360.072
"I
3.*0
3.01
3.28
3.59
3.73
3.9*
*.55
3.95
3.95
3.79
4.10
*.59
4.1*
4.58
4.25
4.42
4.03
4.32
4.11
4.14
4.29
3.88
4.18
3.57
3.48
3.19
^O.O??
K
4.44
4.10
4.30
5.05
5.26
5.30
5.56
4.96
4.74
4.40
4.36
5.29
5.21
5.63
5.36
5.98
5.52
5.53
5.36
5.44
5.28
5.82
5.51
5.84
5.55
360.17
Al
18.8
19.9
21.5
24.2
24.9
23.6
22.6
21.1
21.0
22.3
22.7
24.2
23.2
27.6
27.4
27. 2
29.3
29.1
24.3
21.2
24.4
23.5
23.8
25.7
24.7
34 2.8
Sectlo
Ho.
67
66
63
»3
62
il
60
59
58
57
56
55
53
52
51
48
45
42
39
36
33
30
27
24
22
20
18
16
is
12
11
Mea
Sta
Depth of
a Sediateat
<»>
0-13
13-25
25-38
31-64
64-7S
76-89
89-102
1C2-114
114-127
127-140
140-152
152-165
178-191
191-203
203-216
241-25*
279-292
318-330
356-368
39*- 406
*32-4*5
470-483
50S-52I
546-559
572-584
597-610
622-635
648-660
6fr3-673
699-711
711-724
n Density
ndard Deviation
twt< Collected: 1967 Location: 3
1
Solid.
2.26
1.99
2.06
2.31
2.68
2.66
2.95
3.12
2.95
3.19
3.28
3.36
3.22
3.74
3.45
3.57
3.75
4.45
4.60
5.61
6.20
6.37
7.60
».56
7.90
8.52
10.3
11.3
10.9
14.6
17.9
1.02
Ori-C
185
391
382
357
350
368
332
335
314
351
344
344
336
358
361
359
356
340
364
331
304
315
282
282
314
306
270
2*8
268
223
215
518.3
157.7
P
1.25
1.16
1.13
1.12
1.13
1.16
1.18
1.06
1.06
1.06
1.07
1.05
0.914
1.05
0.933
1.02
1.04
1.06
1.07
0.945
1.01
0.935
0.904
0.870
0.895
0.805
0.785
0.755
0.795
0.846
0.790
U0.01
Fe
1J.2
13.1
13.9
16.4
15.5
17.1
17.0
13.7
1*.*
14.6
13.7
16.4
13.5
15.6
12.2
_
12.5
15.3
15.6
14.1
15.1
13.1
15.4
14.1
15.9
13.1
14.4
12.8
13.5
17.3
15.6
11 0.28
. 1 of Water. South lay
Mn
8/8
0.175
0.170
0.176
0.192
0.218
0.212
0.221
0.224
0.22*
0.238
0.258
0.262
0.251
0.260
0.252
0.244
0.244
0.270
0.299
0.318
0.321
0.334
0.340
0.314
0.326
0.335
0.333
0.351
0.134
0.327
0.309
"0.0033
Ca
1.55
1.55
1.62
1.63
1.38
1.40
1.03
1.16
1.34
1.51
2.00
1.50
1.65
1.61
1.91
2.13
1.66
1.19
1.42
1.47
1.42
1.46
1.63
1.46
1.47
1.45
1.66
2.30
2.26
2.43
2.85
U0.23
"8
2.15
2.08
2.11
2.48
2.82
2.35
2.27
2.17
1.78
2.00
1.67
1.85
1.90
1.99
1.57
1.61
1.77
2.20
1.95
2.85
3.23
2.56
3.16
3.09
2.90
2.99
3.21
3.52
3.66
4.24
4.45
U0.2*
I
2.65
2.69
2.90
3.57
4.25
3.78
3.54
3.35
2.70
2.65
2.59
2.59
2.54
3.40
2.16
2.08
2.18
2.78
2.82
3.79
5.44
3.78
4.76
4.76
4.92
5.33
6.28
6.2*
6.66
8.«5
10.6
"0.3S
Al
10.6
11.3
11.3
12.3
15.2
12.8
19.3
16.2
13.5
14.7
13.3
13.5
13.0
15.7
12.2
10.5
15.8
10,5
13.1
23.1
17.3
20.5
20.3
20.2
21.8
22.5
29.2
29.9
28.9
32.5
39.9
1J0.67
-------
278
APPENDIX B
Mathematical Formulae Utilized During Investigation:
1. Standard Deviation
N-l
2. Relative Standard Error
a
e =
X
3. Linear Correlation Coefficient
N7XY-ZXY
r =
V/NZX2-(ZX)2 -\/NZY2-(ZY)
4. Significance Level of Correlation based on "t" tables from
the equation
r2(H-2)
1-r2
5. Standard Error of Estimate
- V-2
s = V ZY - (aZY + bZXY)
a = standard deviation X,Y = variables
e = relative standard error N = number of observations
r = linear correlation coefficient
t = significance level of correlation
s = standard error of estimate
a = Y intercept
b = slope
-------
1
5
Accession Nurr.brr
^ Ktibjerl Fn'Id &, Group
02K
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization
Wisconsin Univ, Madison, Water Resources Center, Water Chemistry Laboratory
Title
CHEMICAL INVESTIGATION OF RECENT LAKE SEDIMENTS FROM WISCONSIN LAKES AND THEIR
INTERPRETATION,
10
Authors)
Bortleson, Gilbert C
1 JL Project Designation
16010 EHR
21 N
22
Citation
Thesis submitted to the Graduate School of the University of Wisconsin, Madison,
in partial fulfillment of the degree of Doctor of Philosophy, August 1970.
23
Descriptors (Starred First)
*Sediments, *Lakes, *Chemical analysis, Stratigraphy, Cores,
Lake soils, Evaluation, Sedimentary petrology, Wisconsin, Eutrophication,
Chemical stratification, Nutrients, Inorganic compounds, Nitrogen, Phosphorus,
Carbon, Calcium, Magnesium, Potassium, Aluminum, Iron, Manganese
25
Identifiers (Starred First)
*Calcareous lakes, *Noncalcareous lakes, Lake Mendota (Wis),
Madison lakes (Wis), Post cultural lake sediments, Precultural lake sediments,
Organic carbon
27
Abstract
To trace the effects of cultural eutrophication, one meter sediment
cores were used to determine the history of calcareous and noncalcareous Wisconsin
lakes. Cores were analyzed for carbon, phosphorus, calcium, magnesium, potassium,
aluminum, iron, and manganese. Determination of organic nitrogen, exchangeable
ammonium and acid soluble phosphorus were made on selected sedimentary profiles.
Recent sedimentation rates and identification of pre- and postcultural sediments
were determined by ragweed pollen. Enrichment of phosphorus in postcultural Lake
Mendota (Wis) sediments is not only the effect of increased phosphorus supply from
domestic sexrage but also due to increase in phosphorus retentive capacity of post-
cultural sediment and increase of phosphorus deposition due to concomitant increase
of iron, manganese, potassium, and aluminum-containing compounds. Evidence indicates
long, stable, conditions existed in this lake and watershed prior to human habitation,
when phosphorus deposition rate multiplied 5-8 times over the precultural interval.
Phosphorus concentration is largely controlled by iron and to a lesser extent by
manganese deposition. Chemical stratigraphy of concentration-depth diagrams permit
a qualitative evaluation of cultural activities. Potentialities and limitations of
using recent lake sediments to evaluate eutrophication are discussed. (Auen-Wisconsin)
Abstractor
V. S. Auen
WR: 102 IREV JULY 1969)
Institution
Wisconsin Univ, Madison
U-S DEPARTMENT OF THE INTERIOR
WASHINGTON. D C 20240
. GOVERNMENT PRINTING OFFICE: 1972 484-482/32 1-3
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