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?
^mim*'mmfm
   U.S. ENVIRONMENTAL PROTECTION AGENCY

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          WATER POLLUTION COITTROL RESEARCH SERIES
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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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                              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

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 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

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                                                                    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-

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                                                                     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

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                                                                     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

-------
                                                                      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

-------
                                                                     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 git 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

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      LAKE MENDOTA
      1 mile
 Contour Intervals
 in Meters
                                                                   fC-IR,UR
                                                                   I1IR,  IVR
Figure 3.2  Bathmetry and Coring Locations for Lake Mendota.

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                                     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

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                                                                     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

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                                                                      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

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                                                                     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

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                                                                     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

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                                                                     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

-------
                                                                      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




-------
                                                                      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 125C  (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

-------
                                                                     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


27.5C + 0.5C 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


 (28-29C) 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.

-------
                                                                    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:  23C

             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   oranic
               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 - 31C           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  - 31C
                                              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

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                                                                   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

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                                                                    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

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                                                                  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

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                                                                    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

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                                                                   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

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                                                               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

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                                                                    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

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                                                                   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.

-------
                                                                  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

-------
                                                                     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

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                                                                    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)

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                                                                     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.

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                                                                      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

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                                                                     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.

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                                                                     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.

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                                                                     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

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                                                                     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

-------
                                                                      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

-------
                                                                   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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                                   226
                               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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                                                                   227







      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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                                                                    232







 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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                                                                    233
 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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                                                                    238
 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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                                                                    239







     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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                                                                    242
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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                                    243







                               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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                                                                    253
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-------
                                                                     254

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-------
                                                                    255
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                                                                      256
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                                                                    257
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-------
                                                                     258
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                                                                    259
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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

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                                                                                                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


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                          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

-------