NOTICE

    s  proceedings document   has not  been
    r   reviewed  by   the  USEPA  and
   iicial   endorsement should  be  infer
   3   This research  has been funded as
   rt  of the National Acid  Precipitation
program by the USEPA.  CR-811631.


      PROCEEDINGS OF A WORKSHOP ON
      PALEOLLMNOLOGICAL STUDIES OF THE
      HISTORY AND EFFECTS OF ACIDIC
      PRECIPITATION   May 23-25,  1984
                              of a Workshop on
                          leal ! l-ud es  o1  l-he -   hot y  am  E1 fects
                           of Acidic Precipitation
                           Held on May 23-25, 1984
                                Samoset Hotel
                               Rock I and, Maine
                                Organized by

                              Stephen A. Norton
                             Geological Science
                        University of Maine at Orono

                                Sponsored by

                    U.S. Environmental Protection Agency
                     Dr. Charles Powers, Project Officer
                          Project # CR-811631-01-0
                              December, 1984

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                                              600R841O9
                    Proceedings
                 of a Workshop on
PaleolImnologlcal Studies of  the History and Effects
              of Acidic Precipitation
              Held on May 23-25,  1984
                   Samoset Hotel
                  Rock I and,  Maine
                   Organized  by

                 Stephen A. Norton
                Geological  Science
           University of Maine at Orono

                   Sponsored  by

        U.S. Environmental  Protection Agency
         Dr. Charles Powers, Project Officer
             Project # CR-8II63I-OI-0
                  December,  1984

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                         E.P.A. - Paleolimnology Workshop
                                    Attendees
Mr. Denis Anderson
Dept. of Botany
University of Maine at Orono
Orono, ME  04469

Ms. Linda Bacon
Dept. of Botany
University of Maine at Orono
Orono, ME  04469

Prof. Richard W. Battarbee
University College London
26 Bedford Way
London
ENGLAND WCIOAP

Dr. Michael BInford
Dept. of natural Science
The Florida State Museum
Museum Road
University of Florida
GalnesvM le, FL  3261 I
Ms. Geneva Blake
Dept. of Geological
University of Maine
Orono, ME  04469
Sciences
at Orono
Dr. Jan Bloemendal
Dept. of Oceanography
University of Liverpool
Liverpool L69 3BX
ENGLAND

Prof. David Brakke
Watershed Studies
Western Washington University
Bel Iingham, WA  98225

Prof. S.R. Brown
Queen's University
Dept. of Biology
Kingston, Ontario
CANADA  K7L 3N6

Prof. Peter CampbelI
I.N.R.S.-Eau
Unlverslte du Quebec
Case Postage 7500
Salnte-Foy, Quebec
CANADA GIV 4C7
Dr. Richard Carlgnan
I.N.R.S.-Eau
Unlverslte  du Quebec
Case Postage 7500
Salnte-Foy, Quebec
CANADA GIV 4C7

Dr. Donald Charles
Dept. of Biology
Jordan Hal I
Indiana University
Bloomlngton, IN  47405

Prof. Ronald B. Davis
Dept. of Botany and Inst. for
  Quaternary Studies
Deer Ing Hal I
University of Maine at Orono
Orono, ME  04469

Dr. Daniel Engstrom
Dept. of Geology
PI IIsbury Hal I
University of Minnesota
Minneapolis, MN  55455

Dr. R. Douglas Evans
Trent University
Peterborough, Ontario
CANADA  K9J 7B8

Prof. Steve Elsenrelch
Dept. of Civil  & Mineral Eng.
University of Minnesota
Minneapolis, MN  55455

Dr. Jesse Ford
Ecosystems Research Center
Corson Ha 11
Cornell University
Ithaca, NY   14850

Dr. Paul J. Garrison
Dept. of Natural Resources
State of Wisconsin
3911  Fish Hatchery Road
Madison, Wl  53711

Dr. Merr11 I He It
U.S.  Dept. of Energy
Env.  Measurements Lab.
376 Hudson Street
New York, NY  10014

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Dr. Ron Hites
School of Public & Env. Affairs
410 SPEA Bldg.
Indiana University
Bloomington,  IN   47405

Dr. Wolfgang Hofmann
Max Planck  Inst. Der Limnologie
Plon/Horstein
West Germany

Prof. Rich Holdren
Dept. of Geological Sciences
University of Rochester
Rochester, NY    14627

Prof. George Jacobson
Dept. of Botany
Deer ing Hal I
University of Maine at Orono
Orono, ME  04469

Prof. Gerry Mattlsoff
Dept. of Geological Sciences
Case Western Reserve
Cleveland, OH  44106

Prof. Myron J. MItchelI
Dept. of Env. & Forest Biology
SUNY-CESF
Syracuse, NY   13210

Ms. Marilyn Morrison
Dept. of Geological Sciences
University of Maine at Orono
Orono, ME  04469

Prof. Stephen A. Norton
Dept. of Geological Sciences
University of Maine at Orono
Orono, ME  04469

Dr. Jerome Nriagu
National  Water Research Institute
Box 5050
Burlington, Ontario
CANADA L7R 4A6

Dr. David Parkhurst
School of Public and Envir. Affairs
355 SPEA Bldg.
Indiana University
Bloomington, IN 47405
Dr. Charles Powers
Environmental Research Lab.
U.S.E.P.A.
200 SW 35th Street
Corval Us, OR  97330

Prof. Ingemar Renberg
Dept. of Ecological Botany
University of Umea
S-901 87 Umea
SWEDEN

Prof. John Smol
Queen's University
Dept. of Biology
Kingston, Ontario
CANADA  K7L 3N6

Dr. Pam Stokes
Institute for Environmental Studies
University of Toronto, Haul tain Bldg.
Toronton, Ontario
CANADA M55 IA6

Dr. Al Swain
Center for ClImat Ic Research
1225 W. Dayton Street
University of Wisconsin
Madison, Wl  53706

Dr. Baruch Weingarten
Dept. of Geology
Morrill Science Center
Amherst, MA  01003

Dr. Donald Whitehead
Dept. of Biology
Jordan Hal I
Indiana University
Bloomington, IN  47405

Dr. Mark Whiting
Dept. of Botany
University of Maine at Orono
Orono, ME  04469

Ms. Margery Winkier
3415 Blackhawk Drive
Madison, Wl  53705

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                                TABLE OF CONTENTS

                                                                        Page


E.P.A. - PaleolImnology Workshop Attendees	     I

Introduction	  i f i

Acknow Iedgments 	    v

The Lake Ecosystem and Its Record of Lake, Watershed, and
  Atmospheric Phenomena   -  George L. Jacobson, Jr	     I

Tube Coring   -  Ronald B. Davis 	    6

Freeze Coring  -   Ingemar Renberg 	    8

Chronostratlgraphlc Markers  -  Ronald B. Davis 	    15
                                710
Dating Lake Sediment Cores with    Pb  -  Michael W. Binford 	    17

Other RadionuclIdes:   Plutonium - With Some Comments About    Cs
  Chronologies In Freshwater Sediments  -  Merrill Helt et al	    34

Varved Sediments In Chronology  -  Ingemar Renberg	    78

The  Interpretation of Metal Chemistry  -  Stephen A. Norton  	    86

Dynamics of Partlculate Metals  In Lakes of Northern Ontario  -
  Jerome Nrlagu 	  106

Site-Specific Vs. Whole-System Measurements of Trace Metals  In
  Sediments  -  R. Douglas Evans and Peter J. Dillon 	  128

Use of Sulfur  In PaleolImnologlcal Analyses  -  Myron J. Mitchell  ....  151

Sulfur DI agenesis  -  George R. Holdren 	  177

Trace Metal Diffusion Across the Sediment-Water  Interface:
  Implications In the Chronological  Interpretation of Dated
  Trace metal Sediment Profiles  -  Richard Carlgnan 	  198

Stable  Isotopes-  Gerald Mat Isoff  	  201

PaleolImnologlcal Approaches to the Study of Acid Deposition:  Metal
  Partitioning In Lacustrine Sediments  -  Peter G.C. Campbell and
  Andre Tess ler	  234

Diatom Analysis  -  Richard W. Battarbee  	  275

Chrysophyceae  -  John Smol 	  298

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                                                                       Page

Cladocera  -  David F. Brakke	  308

Invertebrates In Sediments  -  Wolfgang Hofmann 	  328

Contributions of Plant Pigments to PaleolImnology  -
  Seward R. Brown 	  345

Sedimentary Humic Materials  -  Daniel R. Engstrom 	  349

Polycycllc Aromatic Hydrocarbons  -  Ron HItes 	  363

Carbonaceous Particles (Soot) from Fossil Fuel Combustion  -
  I ngemar Renberg 	  376

Accumulation and Processing of Chlorinated Hydrocarbons  In Lake and
  Bog Sediments:  Relationship to Atmospheric Deposition  -
  S.J. Eisenreich et al	  387

Magnetic Measurements of Atmospheric Partlculates and Ombrotrophlc
  Peat:  A Review  -  F. Oldfleld, J. Boemendal (presenter) et al. ...  409

Variability and Errors In PaleolImnology  -  David Parkhurst  	  442

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                                Introduction







     Because of rapid changes In technology (and thus our ability to



measure substances), Increased awareness of man's Influence on



btogeochemlcal cycles of elements (e.g. S), and the discharge of man-made



pollutants Into our surroundings, chemical monitoring of our environment



has become Imperative.  Unfortunately, these monitoring efforts span only



the most recent years, making measurement of surrogate parameters of



critical Importance.



     Paleolimnology is the study of historical changes in lakes and their



watersheds, as recorded In sediment stratigraphy.  As lake sediments



accumulate, they Integrate various types of Information related to  limnic



conditions, watershed activities, and atmospheric chemistry.  As such, they



are useful  in reconstructing changes  in climate, land use, vegetation, and



the chemical environment.  Increased  deposition of pollutants from  the



atmosphere Is one such change that can be monitored through the study of



lake sediments.  Whereas sediments may not directly reflect acid-load Ing



from the atmosphere, the effects of this acidity (and related pollutants)



can be detected In the chemical characteristics and fossil biota of the



sediments.   If the age of strata can  be determined In core sub-samples, a



chronology of chemical changes  In the environment can be evaluated.  Thus,



the assessment of the accuracy of dating methods Is critical to



paleolImnology.  This chronological record may be modified by biological,



chemical, and physical processes rendering the record less faithful.



     There  Is strong national  interest  In the history of acidic



precipitation and Its effects.  The U.S.E.P.A. expressed an  Interest  in



ascertaining  (a) what type of evidence  Is available from a study of



sediments and (b) how reliable the sediment record Is in reconstructing the

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history of acidic precipitation and its effects.  This workshop was the



result of that Interest.



     The workshop was run as a plenary session, covering two complete days.



Each of the speakers was charged with discussing the state of art In



respective fields of expertise.  Speakers were chosen on the basis of



having been responsible for developing specific techniques/tools for



paleolimnological analyses and Interpretation.



     The sequential arrangement of the chapters Is, as it was at the



workshop:



      I.  Introduction



     2.  Obtaining sediment samples



     3.  Dating of sediments



     4.  The inorganic chemistry of sediments



     5.  Biological remains in sediments



     6.  Other airborne pollutants found In sediments.

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                               Acknowledgments








     Although the title of this report Implies Its contents. It does not



Indicate the complexities associated with gathering together 50 researchers



from the U.S., Canada, Western Europe, and Scandinavia.  These logistics



were overseen by Ms. Brenda Cote.   In the aftermath, Brenda also typed and



retyped countless versions of oral and written transcripts.  As one



colleague stated, "Your secretary should be knighted!"  She was assisted by



Ms. Judy Polyot.  The presence of Marilyn Morrison and Geneva Blake at the



workshop assured that the gathering was comfortable and productive.  After



the workshop, Jeffrey Kahl, Drs. Terry Haines, Ronald Davis and Ivan



Fernandez contributed a day-In-the-field to show off the Tunk Mountain



Watershed—our  local mini-acidified lake district.



     Prof. David Brakke encouraged me to proceed with the workshop.  Dr.



Charles Powers  (U.S.E.P.A.) provided the funding for the workshop, but



equally importantly, encouraged the concept before, during and after the



workshop.  He also allowed us to be late with our report because of busy



contributors.



     Special thanks are owed to alI  of the participating authors who



contributed valuable time, ideas, and  In many cases unpublished data.  The



participants not making presentations contributed significantly to the



depth, breadth, and liveliness of all of our discussions.  Comparison of



the chapter authors and the  list of attendees reveals that many people have



contributed to  this report although they were unable to participate  In the



workshop.  Their professional generosity Is greatly appreciated.

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                  The Lake Ecoysystem and its Record of Lake,
                      Watershed, and Atmospheric Phenomena


                            George L. Jacobson, Jr.

                    Dept. of Botany and Plant Pathology, and
                        Institute For Quaternary Studies
                              University of Maine
                              Orono, Maine 04469


    The lake as an ecosystem has been recognized and studied for nearly a
century.  In recent decades attention has been focused increasingly on the
interactions of lake, watershed, and atmosphere.  Well-controlled biogeocheraical
studies have now provided fundamental details of ecosystem structure and
functioning.  Calibrated watersheds have been used successfully at Coweeta,
Hubbard Brook, and now several other locales to measure inputs, outputs, and
rates of movement of substances through specific systems.  Flow diagrams (Fig. 1
is a general form) such as those developed from studies at Hubbard Brook
(Bormann and Likens, 1979) give ecologists a basis on which to predict the
consequences of human or natural perturbations in similar ecosystems.

    Within the past decade, the work of Slinn (1976), Lindberg et al. (1979),
and others has demonstrated the importance of dry depostion as a factor in the
interaction of the atmosphere, watershed, and lake.  Those studies have shown
that dry deposition can, in many cases, account for inputs similar in magnitude
to those from wet depostion.

    Continuously accumulating sediments in lake basins provide an integrated
record of the changing conditions within that lake and its associated watershed
(Oldfield, 1977).  Paleolimnological research has for many years explored the
history of such changes; in the process the studies have provided an important
baseline against which to compare the effects of modern disturbances (see
Brugam, 1984, for an excellent review).  Studies such as those of Whitehead and
Crisman (1978), Brown (1969), and Gorham and Sanger (1976) have used various
kinds of data to reconstruct lake productivity over periods of 10^ years.  Other
research has been directed towards reconstructing the changes in chemistry of
the lake, the watershed, and the atmosphere.  Paleolimnological data have even
been used as indirect evidence for climatic change during the Holocene (see, for
example, Winter and Wright, 1977).

    Paleoecological studies that cover time periods of 1CH years have for the
most part relied for chronology on a combination of radiocarbon dating and
regional correlations of dated pollen profiles.  Rarely have those chronologies
provided adequate resolution in time scales of 10^ to 10^ years, however.
In a few cases, varved sediments have been found throughout sections that span
the Holocene (Craig, 1972).

    Recent interest in the effects of industrial pollutants has stimulated the
development of dating techniques that can be used to give highly resolved
chronologies for the past several centuries.  These methods include evaluation
of radiometric decay of 210pb an
-------
sediments have proven to be especially revealing.  Pioneering work on such
sediments by Craig (1972) and Swain (1973) has led to significant advances in
subsequent studies of fire history (e.g.  Cwynar, 1978, and others).  Simola
(1977) has measured within-year succession of diatom populations in varved
sediments from a Finnish lake (Fig. 2).  His recent work provides valuable data
on the population biology of those algae for the last 600 years.

    In addition to advances in dating, the past decade has produced considerable
gains in knowledge of how the sedimentary record can be used to infer (1)
past water chemistry, (2) the quality and quantity of wet and dry deposition
from the atmosphere to lake and watershed, (3) the effects of pollutants
on biota of the lake, (4) the geochemistry of the sediments, and (5) the effects
of diagenesis and dissolution on the sedimentary record of diatoms, pigments,
and other biological and physical materials.

    Even with many recent positive developments in paleolimnological methods and
knowledge, there remain several problems that confound interpretation and
inference from raw data.  These problems result from fundamental characteristics
of the sediments and the ecosystems in which they originate.  First,
sedimentation is the culmination of processes that integrate (in both time and
space) the evidence of phenomena that have occurred in the atmosphere, the
watershed, the lake, and the lake sediments.  Second, the biogeochemical
processes active in the lake-watershed system act as filters that transform and
limit the evidence left by events such as fire, acidic deposition, or other
disturbances.  While both the integrative properties of sedimentation and the
filtering properties of the ecosystem have the potential to be used to advantage
by paleolimnologists, they clearly require careful analysis and study.

    The critical challenges for research now involve clarification of the
processes and mechanisms that constitute the ecosystem "filter".  Models of
inference about environmental phenomena must continually be improved so that any
"transfer function" approaches are based on understanding of ecosystem processes
and not merely statistical correlations.  Biologists must gain additional
insights into the autecology of those organisms whose remains occur in the sedi-
ments, as well as into the nature of ecological interactions between organisms.
Geochemists can add to current knowledge of physical and chemical processes and
mechanisms.  Geochronologists continue to provide better and more precise
methods for dating sediments.

    This conference brings together leading scientists in many of the key
sub-disciplines of paleolimnology.  Collectively they report on excellent
progress in developing techniques for understanding how the biology and
biogeochemistry of lake and watershed are recorded in lake sediments.

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                                                The Northern Hardwood Forest   35
3. The small-watershed technique coupled with measurement of internal features according to the
  Hubbard Brook Nutrient Flux and Cycling Model. (After Bormann and Likens 1967, Likens and
  Bormann 1972.)
      INPUT
  METEOROLOGIC
  VECTOR
   gases, sonds in
   water and air
 Mineral Formation


• — Intrasystem Cycle
                                                               .J
                                                                          OUTPUT
                                      METEOROLOGIC
                                      VECTOR
                                          gases
                                                                      GEOLOGIC VECTOR
                                                                        solids in stream-
                                                                        water
             Additional potential for biogeochemical study

             1.  Annual nutrient uptake by living taiomass
             2.  Nutrient accretion in living and dead biomass
             3.  Estimates of leaching, exudation, and decomposition
             4.  Estimates of nutrient input by gaseous uptake, impaction, and nitrogen fixation
             5.  Mora complete estimate of weathering
  Fig.  1.    Generalized  flow  diagram.
                Reproduced  from Bormann  and  Likens  (1979)

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   LAKE LOVOJARVI, Finland
        0          50                   50        20  10   10     20     20        20
Fig.  2.   The annual diatom succession in Lake Lovojarvi, Finland, preserved in annually laminated sediments. The
  values are numbers of objects in successive horizontal microscope fields of view ISO urn wide across the adhesive tape.
  (After Simola, 1977.)

  Reproduced  from  Birks  and Birks  (1980).

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                                References Cited
Birks, H.J.B. and Birks, H.H.  1980.  Quaternary Paleoecology.   Arnold. 289 pp.

Bormann, F.H. and Likens, G.E. 1979.  Pattern and Process in a  Forested
     Ecosystem.  Springer-Verlag.  New York.  253 pp.

Brown, S.R. 1969.  Paleolimnological evidence from fossil pigments.  Mitt.  Int.
     Verein.  Limnol., 17, 95-103.

Brugam, R.B. 1984.  Holocene paleolimnology.  pp. 208-221 in Wright, H.E. (Ed.)
     Late-Quaternary Environments of the United States,  v.2.  The Holocene.
     Univ. of Minnesota Press.

Craig, A.J. 1972.  Pollen influx to laminated lake sediments:  a pollen diagram
     from northeastern Minnesota .  Ecology, 53, 46-57.

Creer, K.M., Thompson, R., Molyneux, L., and Mackereth, F.J.H.  1972.
     Geomagnetic secular variation recorded in the stable magnetic remanence of
     recent sediments.  Earth Planetary Science Letters, 14, 115-127.

Cwynar, L. 1978.  Recent history of fire and vegetation from laminated sediment
     of Greenleaf Lake,  Algonquin Park, Ontario.  Canadian Journal of Botany.
     56, 10-21.

Gorham, E. and Sanger, J.E. 1976.  Fossilized pigments as stratigiophic
     indicators of cultural eutrophication in Shagawa Lake, northeastern
     Minnesota.  Bulletin of the Geological Society of America, 87, 1638-1642.

Lindberg, S.E., R.C. Harriss, R.R. Turner, D.S. Shriner, and D.D. Huff..  1979.
     Mechanisms and rates of atmospheric deposition of selected trace elements
     and sulfate to a deciduous forest watershed.  Oak Ridge National Lab.,
     Environmental Sciences Division, Pub. # 1299.

Oldfield, F. 1977.  Lakes and their drainage basins as units of sediment-based
     ecological study.  Progress in Physical Geography, 1, 460-504.

Simola, H. 1977.  Diatom succession in the formation of annually laminated
     sediments in Lovojarvi, a small eutrophicated lake.  Ann.   Bot.  Fenn., 14,
     143-148.

Slinn, W.G.N.  1976.  Some approximations for the wet and dry removal particles
     and gases from the atmosphere, pp. 857-894 in  Proc. of the First
     International Symposium on Acid Precipitation and the Forest Ecosystem.
     USDA Forest Service Tech. Report NE-23, 857-894.

Swain, A.M. 1973.  A history of fire and vegetation in northeastern Minnesota as
     recorded in lake sediments. Quaternary Research, 3, 383-396.

Whitehead, D.R. and Crisman, T.L. 1978.  Paleolimnological studies of small New
     England (U.S.A.) ponds.  I.  Late-glacial and postglacial  trophic
     oscillations.  Pol. Arch. Hydrolist., 25, 471-481.

Winter, T.C. and Wright, H.E. 1977.  Paleohydrologic phenomena recorded by lake
sediments.  Eos, 58, 188-196.

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                                   TUBE CORING



                        (for top  ca.  1  m of lake sediment)



                                    R.B. Davis








I.    Equipment



     A.    Types of corers (general)



          1.   Tube corers versus  freeze "corers"



          2.   Piston versus no piston



          3.   Push rods versus self-contained drive



     B.    Corers (specific)



          1.   Construction and materials



          2.   Depth sensors



          3.   Dimensions (sample  size & core length)



          4.   Portability (hike-to versus drive-to or fly-to lakes)



     C.    Boats and platforms



          1.   Winter versus summer



          2.   Portability (hike-to versus drive-to or fly-to lakes)



I I.   Techniques



     A.    Getting to lake



     B.    Getting onto lake



     C.    Finding coring spot, sounding, and stabilizing platform



     D.    Using Davis-Doyle corer



     E.    Sectioning; transporting core or sections



     F.    Storage



III. Disturbances of sediment



     A.    Platform InstabM ity



     B.    Coring technique



     C.    Gas bubbles



     D.    Field evidence of bioturbation

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IV.   Summary



     THE  RESULTS  ARE  AS  BAD AS  THE  CORE



     THE  CORE IS  AS GOOD AS THE CORERS  (CORER = EQUIPMENT + PERSON



       OPERATING  IT)

-------
FREEZE CORING


Ingemar Renberg
Department of Ecological Botany
Umea University
S-901 87  UMEA
SWEDEN
The sediment coring is of great importance to any paleolimnological
investigation. Errors caused by a poorly performed coring  and  sub-
-sampling can not be repaired by refined analyses. Several gravity
corers give fine cores of surface sediments, but it  is difficult  to
sub-sample such cores in a satisfactory manner to obtain uncontamina-
ted and quantitative samples. Furthermore, it is impossible to make
detailed visual observations of the micro-stratigraphy of  the  cores,
at least, when the sediment is loose. Here lies the  strength of the
freeze coring technique.

A freeze corer is simply a kind of metal container filled  with a
freezing medium, usually a mixture of crushed solid  C02 and some  al-
cohol. The corer is lowered into the sediment and left there for
10-15 minutes to allow the sediment to freeze on the sampler casing.
This sampling technique was introduced by Shapiro (1958) and several
models have been developed since then.

Different models of freeze corers

The following figures show five types of freeze corers and the main
differences between them.
                '   _S
— bolt
               2 ft
                             weight

                              .-— rubberstopper
                             opening
                           — metal Jacket
                           —metal funnel

                        —metal tube
Fig. 1.  The freeze corer introduced by Shapiro  (1958).  The  freezing
mixture is put into a container formed by a metal  jacket mantled
around a metal tube. The sediment freezes in the tube. Figure  from
Shapiro (1958).

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                 rope
            polyethylene tube
                   metal tube


                       weight
                          plug
Fig. 2.  The  'frozen  finger1,  a freeze corer designed by H.E. Wright
Jr. In this sampler the  freezing mixture is filled in the tube and  the
sediment freezes on the  outside of the tube. The sampler is described
by Saarnisto  (1979) and  by  Wright (1980). Figure from Saarnisto  (1979).
                           ball valve   socket
                          /    cover    B    c
   rubber fastener
       wire handle

     freezing panel
    plywood tray


[3>> steel spring
                                         -keel
                                                 weight
Fig. 3.  The so-called  'box  freezer'  designed by Huttunen & Merilainen
(1978). The sampler  is  flat-sided and filled with blocks of dry-ice.
The sediment freezes on one  side of the sampler. Figure from Huttunen
& Merilainen (1978).

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                                                                               10
          MIRK-CABLE, FOR
          l-OHtRINC AND RAISING —
          THE SAMPLER
          III-MUVAIILE ATTACIIUKNT
          WHICH ALLOWS tlEMOVAL
          On AUDITION OK THE
          MUIUIITS
          [RON TUUINO
          IRON WKICHTS, THE
          NUMUKM OF WHICH CAN
          UK VAKILD ACCORDING
          fU Till: MtNLHAL CON-
          Tfirr OK Tut: SEUINLHT
           llUCII IS riLLLD UtT
           iuLlU Coj AND SOME
           il'IIANOL
i
       STOP-DEVICE, COR ATTACHING TO Tilt WtHC-
       CABLC TO PREVENT TOO DLL'P PLNLTRATION OF
       Tilt SAMPLER INTO THE SUHCACt SFUlMtNT
                                       MATEH-TICIIT HUBKER CASKKT
Fig.  4.  A  wedge-shaped  freeze  corer designed by Renberg  (1981).  On
this  model  the weights are placed on the top  of the  casing.  This  detail
combined with the  shape  of the  sampler makes  it very easy  to melt loose
the frozen  sediment. Another great advantage  with  this sampler, as well
as the 'box-freezer', is the flat-sided samples provided.  Figure  from
Renberg (1981).
               pressure reducer
                   gas cylinder
        liquid nitrogen container- ij:
                        weight'
        gas volume meter
        nitrogen siphon
        tube
                                             cooling coil
                                             vacuum jacket
                                             heating elements
Fig.  5.  Pachur  et al.  (1984)  presents  a freeze corer which uses  liquid
nitrogen as  the  freezing  medium.  In  this case the  sediment freezes in-
side  the tube. Figure from Pachur et  al. (1984).

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                                                                     n
 How to operate a freeze corer - an example

•To be able to take undisturbed freeze cores  of unconsolidated recent
 sediments  it is almost necessary to work from the ice-cover of a lake.
 Fig.  6 illustrates freeze  coring with the wedge-shaped corer designed
 by Renberg (1981).
 Fig.  6.   Photographs showing some important steps in operating the
 freeze corer.  Two holes in the ice are required, one for measuring
 the water depth with a load line and one for the sampling.

 a) The casing is filled with crushed dry-ice and about half a litre
 ethanol  is added.
 b) The upper section with the weights, rubber-tubing and wire is
 mounted  to the casing.
 c) The sampler is lowered with the wire. When the sampler is about
 half  a metre above the sediment surface it is wise to stop for some
 15 seconds.  The sampler is then slowly lowered into the sediment.
 The stopdevice mounted on the wire allows the sampler to penetrate
 into  the sediment to a pre-determined depth.
 d) After being left some fifteen minutes in the sediment the sampler
 is pulled up and the upper section is dismounted.
 e) The sediment sample is cleaned by scraping away the loose unfrozen
 sediment with a knife.
 f) Finally the sample is melted away from the sampler by pouring warm
 water into the casing. The sample can be wrapped into plastic for
 further  transportation to the laboratory and the sampler is ready to
 be used  again.

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                                                                     12
Advantages with freeze coring

Compared to fresh cores, taken with a perspex-tube equipped corer,
frozen cores have several advantages:

1. The micro-stratigraphy can be observed. Varves can be counted.

2. Different cores are easy to connect to each other. In most lakes
   there are some kind of microstratigraphic marker horizons, mineral
   layers, colour changes etc.

3. Clean, uncontaminated, sub-samples can be cut out from the frozen
   core.

4. A series of closely spaced sub-samples can be cut out.

5. It is possible to make a quantitative sub-sampling which makes it
   easy to calculate annual net accumulation values (influx values)
   of sediment components.

6. Frozen cores are easy to store.

The points 1 and 5 are most important. Point 5 might need some further
explanation.

The procedure of sub-sampling a frozen sediment core is schematically
shown with a few drawings in Fig. 7.
Fig. 7.  Sub-sampling of a frozen sediment core.

a) The outside of the sample is planed clean.
b) One broadside is sawn out and its inside is planed until the disturbed
sediment is removed.
c) The core is ready to be sectioned. If small samples are needed the core
can be divided using a saw.
d) Sub-samples comprising a known number of years or a certain height
e.g. 0.5 cm can be cut out using a knife (the type with a disposable
blade is recommended). At this moment of the work a natural size photo-
graph is very useful if it is a varved core.

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                                                                      13
When we have a frozen  core  it  is simple to cut out sub-samples which
represent a known area of the  lake bottom and which comprise a known
number of years. If  the sediment is varved it is no problem to deter-
mine how many years  we have in the sub-sample but if we are dealing
with an ordinary non-varved sediment we have to determine the number
of years by a detailed dating  of some other kind. Finally, if we de-
termine the total number of a  subfossil or the total content of a metal
in the sub-sample we can make  a reliable calculation of the annual net
accumulation rate of the subfossil or metal according to this formula.
                         D = annual net accumulation rate

                         n = number of a subfossil or the total metal content

                         v = number of years

                         a = area of the lake bottom
                         .   	1          ( to adjust for varying
                          " 1-(0.0008 W)"      water C0ntent W=W)
Problems

In spite of the many  advantages  provided by the freeze corers, especially
for sampling loose  surface  sediments,  there are, however, some problems
to be considered.

- All existing freeze corers  demand an ice-sheet to work from for a
successful sampling.  It  is, however,  certainly possible to design a
corer with legs to  allow coring  from a boat.

- All samplers are  rather thick  and to some extent they all distort the
sediment stratigraphy. It should be possible to construct a thin freeze-
-plate corer using  liquid nitrogen as  freezing medium.

- The freezing may  affect water  soluble substances in the sediment. A
detailed chemical comparison  between fresh and frozen cores is proposed.
References

Huttunen, P. & Merilainen,  J,  1978.  New freezing device providing large
   unmixed sediment samples from lakes.  - Ann. Bot. Fennici 15, 128-130.

Pachur, H.-J. 1984. Paper  in print in Catena.
Renberg, I. 1981. Improved methods  for sampling, photographing and
   varve-counting of varved  lake  sediments.  - Boreas 10, 255-258.

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                                                                      14
Saarnisto, M. 1979. Studies of annually laminated lake sediments. In:
   Berglund, B.  (ed.) Palaeohydrological changes in the temperature zone
   in the last 15000 years. IGCP 158b. Lake and mire environments. Pro-
   ject guide 2: Specific methods,  61-80. Lund.

Shapiro, J. 1958.  The core-freezer  - a new sampler for lake sediments.
   - Ecology 39, 758.

Wright, H.E., Jr.  1980. Cores of soft lake sediments. - Boreas 9,
   107—114.

-------
                                                                               15
                           CHRONOSTRATIGRAPH 1C MARKERS
            (for lake sediment deposited during the historical period)
                                    R.B. Davis
A.   Characteristics of good chronostratigraphic markers

     1.   No delay in deposition

     2.   Immobility and good preservation In sediment

     3.   Ease of recognition and analysis

     4.   Availability of historical Information or chronological

            calI brat Ion

B.   Brief survey of types of chronostratigraphic markers

     1.   Inputs from atmosphere

          a.  RadlonuclIdes  including    Cs (see Robbins & Heit)

          b.  Po11 en

          c.  Charcoal

          d.  Soot and magnetic particles (see Renberg & Bloemendal)

          e.  Trace metals (see Nriagu & Dillon)

          f.  OrganIcs (see Hites & Eisenreich)

          g.  Other

     2.   Inputs from watershed

          a.  Land and water retention and mobility of inputs from

                atmosphere

          b.  Substances  introduced directly to watershed (Including

                directly to  lake)

          c.  Geochemical and biological  Indicators of perturbations

                In watershed

C.   Indicators of watershed erosion

     1.   Erosion-producing events

     2.   Geochemical  Indicators  In sediment

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                                                                               16
     3.   Progressive erosion of soil profiles and indications in



            sediment



D.   Pollen as a chronostratigraphic marker



     1.   Vegetation and landscape changes affecting pollen rain



     2.   Sources and distances



     3.   Analytical techniques



     4.   History and chronology



     5.   Art versus science?



E.   Charcoal as a chronostratigraphic marker



     1.   Sources and distances



     2.   Analytical techniques



     3.   History and chronology, and problems of Interpretation



F.   Concluding comments

-------
                                                                 17
                                              210
              Dating Lake Sediment Cores with    Pb


                               by


                       Michael W. Binford

                      Florida State Museum

                      University o-f Florida

                      Gainesville, FL 32611


           facto  study  of  limnological  processes  depends  on

accurate  dating  o-f  sediment cores.   Demonstration  that  lake

acidification  has  occurred  contemporaneously  with    increased

atmospheric  loading of anthropogenic pollutants is a  necessary,

although  not  sufficient condition for arguments concerned  with

causes and effects of acid deposition.

     A  number of methods are available for  dating  cores.    The

primary  method that is generally applicable is to use the  decay

of naturally occurring radionuclides as a continuous time marker,

or  the  occurrence of man-made radionuclides as horizon  markers.
          210       137
Assays of    Pb and    Cs in sediments are examples of the former

and latter uses,  respectively.  The remainder of this section is
                                                    210
concerned with:   1) The generation and movement of    Pb in   the
                                     210
environment; 2) The incorporation of    Pb into the sediments; 3)

The  two major models used for dating cores;  4) The sources   and

magnitude  of statistical error in calculation of dates,  and  5)

Recommendations for research designed to resolve questions raised

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                                                                 18
in the -first 4 topics.  This report is a very brief summary  of  an
                                              210
extensive body of work.  Anyone interested in    Pb dating should

be  familiar  with  several papers  (Robbins  1978,  Appleby and

Old-field 1978, 1983, Oldfield and Appleby 1984).  No dating

can   be   done  properly  without  an  understanding  of    these
                               137
discussions.  I do not discuss    Cs dating.
     ,   ,                      r~  •
     210Pb is a member of the 238LJ decay series  (Figure  1),   with
                                                 226
a  half-life  of  22.3  years.   The  precursor     Ra   is   found
                                           226             222
everywhere in rocks, soils, and seawater.     Ra decays  to    Rn,
                                222
which  is  a gas.   Much of the    Rn escapes to  the  atmosphere
                                                             222
where  an  atom has a mean residence time  of  3-4  days.       Rn
                                                           210
decays  through  a series of very short—lived isotopes to     Pb.
           210
The  solid    Pb adsorbs onto atmospheric  particulates,  and   is

quickly  scavenged from the air in rainfall.   Once deposited in

the  lake,   the  particulates  remain in the water column  for  a

usually short time relative to lakewater residence  time.    After
                                  210
incorporation into the sediments,    Pb seems to be unaffected  by

chemical  changes  and  probably  does  not  diffuse  vertically.
                                                     210
However, physical mixing can translocate particulate     Pb.

     The  foregoing discussion is concerned only with sedimentary
210
   Fb  derived from atmospheric fallout.   A certain fraction   is
                                         226
produced i_n situ by decay of sedimentary    R'a.  The intermediate
oor*
   Rn may diffuse vertically,  but upon decay forms an   additional
             210
increment of    Pb.    The fraction derived from the atmosphere  is
                     210
called "unsupported"    Pb, while that produced i_n si_tu  is called
             210
"supported"     Pb.    Other  sources,   such as erosion   from the

drainage  basin or supply by tributaries appear to be  negligible

-------
                                                           19
u
92
Po
91
Th
90
Ac
89
Ro
88
-r
87
Rn
86
At
85
Po
84
Bi
83
Pb
82
Tl
81
Hg
80
S,

o
/S
Th234
24 d












Po254





'










u"*
2.S«iO?»
Q
a
Th230
7.5*i04y
1-
RO226
I622y
a
Rn222
3.8 d
a
Po218
3m
o
Pb214
27m















At218
Q i
ia
Bi214'
20m
/3 '
10
1
Tl210'
1.3 m














Po214
2il6*»
0 \
r
pb210
0 !
t
Hq206
9m













Bi210'
5d
4
n i
\
Tl206
4.3m
0













Po2'0
a
'i/ui/i7//ft
>S table/
^



           238
Figure 1.
U decay series  (-from  Robbins 1978)

-------
                                                                  20

 in   most   cases.    See -figure 2 -for a  diagram  o-f  environmental
                          210
 pathways  -for  delivery o-f     Pb to lake sediments.

      There are  a  number  o-f  ways to measure the speci-fic activity
     210
 o-f     Pb.    Direct gamma counting is the easiest,  but  requires

 specialized and  expensive instrumentation not usually available  to

 1 imnologists.    Preparation   -for  counting beta activity  of  the
                 214
 daughter  product     Bi is exceedingly tedious, and the e-f-fects o-f

 planchette geometry  and assumptions o-f  complete  recovery  can

 o-ften lead to under-measurement.   The most popular method now is
                                     210
 alpha-spectrometry  of the daughter    Po,  with a pre-processing
          208
 spike of    Po added for  calibration.

      Under ideal conditions  of constant sedimentation rate and no
                                            210
 compaction,   the   vertical distribution of    Pb in a core should

 be  a monotonic,  exponentially declining curve (Figure  3).   The

 asymptotic level is non-zero because of the activity of supported
 210
    Pb.    Supported  levels are estimated in one of two ways.   If

 radioactive   equilibrium   is assumed,  the measured  activity  of
 226                                 '                      210
    Ra  is   set    equal   the  activity   of   supported      Fb.

 Alternatively,   the  downcore  asymptote  can  be  designated  as

 supported activity at other  levels, with an assumption of uniform

 distribution  (dotted line on Figure 3).

      Real cores from real lakes are never ideal.   The  specific
            210
 activity  of    Pb  at any  one level can be altered by  compaction,

 bioturbation  or  physical  mixing, decomposition of organic matter,

 and  variable rates  of  sediment  accumulation.    Compaction  is

-considered differently  by  the different dating  models  and  is

 discussed later.    Mixing  can  be explicitely included  in  the

 models by introduction of an additional term.   Decomposition  of

-------
                                         210
Figure  2.   Environmental   pathways of    Pb (-From Old-Field   and

Appleby 1984).

-------
LJ
O
O
a.
UJ
o
Figure


The dot
             Pb-210 ACTIVITY
                                     22
ted 1
 " 22
 Ideal distribution o-f   Pb in a sediment  profile.
                21C
i ne represents supported  F'b .

-------
                                                                 23
organic  matter has not been considered previously as a source  o-f

bi as.

     Various  models,  which  provide  mathematical  methods  for

calculating  dates  and sediment accumulation  rates,  have   been

proposed.   Each  model requires assumptions about the manner   of

incorporation into the sediment and post-deposi tional behavior  o-f
210
   Pb.  At two ends of a continuum are the Constant Activity  (CA)

or  Constant Initial Concentration  (CIO model and  the   Constant

Flux   (CF) or Constant Rate of Supply  (CRS) model.   The  CA model
                                       210
assumes  that the specific activity of    Pb in sediments at  the

mud-water   interface  is  constant.    As   sedimentation   rate
                                  210
increases,   the  scavenging  of     Pb  from  the  water column

increases,  also.   Each  unit  mass of sediment  adsorbs   a   unit
             210                                        210
activity  of    Pb.   The CF model assumes that flux of    Pb   to

sediments  is  a constant,  and is independent  of  sedimentation

rate.    If  bulk  sedimentation  rate  increases,  the   specific
            210
activity of    Pb declines as it is diluted.

     Dates are calculated from the CA model by the relationship:

                         -1
                    t = k   In  (C(0)/C(X»               (1)

                                                    210
where  t=time in years,  k is the decay constant  of    Pb (.03114
  -1                  '                    210
yr   ),  and  C is the specific activity of    Pb  at core  depth   X.

The slope   of   the   regression  line  describing   the  age-depth

relationship is the mean sediment accumulation rate.

     The CA model fails if the activity-depth curve deviates  from

an exponential form,  for whatever reason.  Several examples  from

the    literature  describe  typical  failures.    Figure   4a    is

-------
                                                                                       24
                                      OCCESS pa-ao
                          ?      •   ,	 .  t	f
                      I  •
                        Unsupported "°Pb concenlir'ioni v» ace
             0 20   60   !(/)   140   0  :0    60    100   I4O  0  20    60   100    I-U   ISO
                                            Age (yr)
.3Lire    4.     E.;ai7ipl..?s of  failures of  the CA  model.     Figure 4a  i

-^m  '/',~n  Damm  «t  .:, 1 .  (1979)  and  4b  is  from  Appleby et  al.   (1979)

-------
                                                                 25


apparently caused by a slumping event which brought  several  cm  of

sediment  to the coring site,  and resulted in  a  thick   layer   of

constant   activity.    Figure  4b  is  the  result   o-f   changing

sedimentation  rates as the pro-files are composed o-f  varves,   or

annual layers.   The latter figure argues against the  assumption

o-f  constant  initial  concentration,  and was  one o-f  the   early

reasons -for the development o-f the CF model.

     Dates are calculated from the CF model by  the relationship:
                              -1
                         t = k   In  (A<0)/A(X))
                                   210                    -2
where  A is the total,  integrated    Pb  activity  (pCi/cm  )   below

                     •«
depth X, or
                         A(X) = J p C(X)  dx                    (3)
                                0
The  new term,  p,  is the amount of  dry-phase  sediment  per  unit

volume  of wet sediment.   Changing sedimentation  rate and  down-

core  compaction  are  both   included in   the   equation   by  this

formulati on.

     The  CF model fails if the  sediments  are either  mixed to  an

appreciable  depth,  or have  been disturbed  by  slumping,   both of

which  may occur  in the Mirror Lake core  (Figure 4a).    A  mixing

term can be included in the model.    However,   the lower boundary

of the mixing zone must be set either subjectively or by means of

other,  independent  evidence.   Other evidence is  usually  very

difficult, if not impossible, to obtain.

     The conditions for failure  of the CF  model also cause the CA

-------
                                                                 26
model  to -fail.   Should all assumptions  of  the  CA model  be  met,

both   models   will  result  in  the  same   date   and    sediment

accumulation  rates.   Their  di-f-Ferences lie in  the  assumption
                                        210
about the mechanism o-f incorporation of    Pb

    As an interesting note, proponents o-f the two  models  work in

qualitatively  different systems.   The CA model has been applied

successfully  in very large,  deep  lakes  as  well  as  reservoirs.

The CFr model works best in medium-sized or small lakes.    Because

the  fundamental  difference between the  two models is related to
                           210
mode   of  scavenging  of     Pb  from  the    water   column,   the

applicability of one model over another may  be system-dependent.

     Large,  deep  lakes  and reservoirs  may have  an  essentially
                       210
infinite   supply  of     Pb  in  the  water   column.     Increased
                                 210
sedimentation  can scavenge more    Pb because more than  enough  is

avail able.   Conversely, smaller lakes have  a smaller total pool,
                           210
and  the residence time of    Pb will be  much  shorter.    There  is
                 210
always a lack of    Pb in the water column to be scavenged.

     Criteria  for correct application of a  particular model have

been discussed in the primary literature  as  cited  earlier.   Until

more  is understood about the relationships   between  atmospheric

flu:;,   water  concentration,   mode  of   scavenging,   and  bulk
                        210
sedimentation  .rates of    Pb in various  lake types,  choice of the

appropriate model must be subjective, and based  on expert opinion

instead of objective criteria.

     The uncertainties associated with a  date calculated  from any

of  the models are not well understood.    First  of  all,   factors
                                  210
affecting  the  distribution  of     Pb   in   sediments  are   known

-------
                                                                 27

incompletely  (Table  9.8  in  Robbins 1978 lists  more  than  25

speci-fic  -factors).   Secondly,  the natural variation  of  other

sedimentary  features  is  unknown.   Third,  the biases  of  the

various  dating  models  are  not  well   known.    Fourth,   the

statistical  properties  of  the models  are  unspecified.   Many-

authors have presented error bars  in age-depth diagrams, but none

have ever been explicit as to how  the errors were calculated.

     Fundamentally,  two components of uncertainties are accuracy

and  precision.   Accuracy is a function of adequacy of  sampling
                                                              210
design, measurement, and model specification.  In the case of    Pb

dating,  accuracy  can be assessed only by comparison with  other

stratigraphic  markers of known age.   The use of many  lines  of

evidence  is  an absolute requirement in paleolimnology,  and  no

single line,  no matter how quantitative or rigorous,  can  stand

alone.   Qther  appropriate evidence is discussed in every  other

section of this report.

  Precision  is  described  by  statistical  error  because  each

analysis  of  each  level  in  each core is  a  sample  from  the

naturally variable population of all cores in a lake.  All  terms

in all dating models are subject to statistical error, except the

constant  k.   The error of C(X) in the CA and CF models includes

sampling error of the dry mass determination,  sampling error  of
210
   Pb activity,  and the counting  error inherent in any measurement

of  radioactivity.   If  the true  or estimated variance  of  each

measurement is known,  then uncertainties of a date calculated by

the CA model are calculated in a straightforward manner.    If the
                 210
distribution  of    Pb is truly exponential,  then the fitting of  a

regression   line   can   provide  a   first   approximation   of

-------
                                                                 28
uncertainties.

     Statistical  errors o-f dates calculated  by  the  CF model   are

more  problematical.   Errors  are  propagated   during  numerical
               210
integration o-f    Pb activity.   That  is,   the error o-f a date at a

single  level  is dependent on the errors  of  all  other  levels.

Several  investigators  are currently  working on an   analysis  o-f

propagation  of errors in the CF model,  but  no  calculation method

is available now.

     The question o-f uncertainties in  dating  is  critical -for  both

pure and applied paleolimnology.  Until  very  recently, inadequate

attention has been paid to the question,   perhaps because it   has

been only recently that paleolimnology has been  viewed as a valid

way  to  approach topics o-f immediate  environmental  and  economic

concern.



RECOMMENDATIONS



     The  recommendations  o-f  this  section  o-f   the  report   are

presented under three topics:  1) Procedural  recommendations  outline

steps -for routine dating o-f cores.   2)  Research needs point   out
                                                         210
gaps  in basic understanding  of the biogeochemistry  of     Pb.   3)

Institutional  standards suggest some  services  that  the EPA might

provide  the research community.   The research  needs  are  aimed

only  at studies concerned with timing of  events,  and not whole-

lake  material  fluxes.   A more extensive coring program  in  a

single  lake is required for  such whole-lake  studies as  nutrient

budgeting or studies of ecosystem material cycling.

-------
                                                                 29
Procedural Recommendations

     1.    In every lake o-f interest,  multiple cores  (at least 3)

    should  be  taken  at every site.   Multiple  cores  are  not

    necessary  for  determination of  time-specific   events,  but

    provide  for 2 items.   First,  back-up material  is available

    in  case  the  first core analysed  is  inadequate  for  some

    reason.    Second,   secondary  cores  provide  material  for
                                                             210
    measurement  of total residual  (atmospherically-derived)    Pb,

    an   important  parameter  used  for  determination  of   the

    appropriate model.



    2.  Apply several dating models  (CA,  CF,  CA with mixing, CF

    with mixing,  etc.) to each core, and present all the results

    in any reports.  The results should include estimates of both

    accuracy and precision,  and explicit description of how they

    were derived.


                                      210
     3.   Measure  atmospheric flux  of    Pb by  independent  means.

    Cores  from nearby,  undisturbed soils are a very good way to

    measure fallout rates  (Nozaki et al.  1977).    Nearby fallout

    collectors  are also appropriate,  but difficult  to  maintain

    and not always available.  Comparison of measured atmospheric

    flux with that calculated from  total residuals  indicates  the

    adequacy  of the core and the appropriate dating  model.   If

    the  values  are nearly the same,  the CF model   is  probably

    appropriate,  and  in addition the cores are probably taken in

    an area not subject to sediment  focusing or erosion.  If they

-------
                                                                 30
    are   different,    the   core  still  may  be  adequate    -for

    establishing times of events,  but dates calculated by the CA

    model  should be given greater credence.



     4.  Analyze  many  other lines of  evidence.    The   land-use

    history  o-f the drainage basin is essential  to   discriminate

    between  local  and  regional phenomena and  to   provide   time

    horizons -for erosion events,  input o-f substances such .as by-

    products  o-f industries on the lakeshore  (layers o-f   sawdust,

    pine  resin,  plastic beads,  and animal hair have all   been

    reported  in  lake  sediments).   Atmospheric  deposition  o-f

    combustion products  (PAH's,  soot particles,  ash -from -forest

    fires,  etc.) has been recorded for other  purposes, and  o-ften

    provides a strong signal in  lake sediments.

         I  include  in this section the  appearance,  peak,   and

    disappearance  of man-made   radionuclides.   Distribution  in
               137
    cores  o-f     Cs -from atmospheric testing  o-f nuclear  weapons

    has  been  used  extensively as  a  dating   tool,  and   other
                            239
    radi onucl i des  such  as    Pu -from the power source o-f a  re-

    entering  satellite can also serve as valuable horizons.



Research Needs

    1.   The  most  pressing  need  is  an  understanding  o-f   the
                             210
    processes o-f movement o-f     Pb from the air  to the water  to the

    sediment.  Specific questions that must be answered are:
                                           210
     a.  What is the magnitude of input of     Pb from tributaries  or

    overland  transport from the drainage basin?   How does   the

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                                                                31


    extra-lacustrine  source in-Fluence supported and  unsupported

    acti vi ti es?

     b.    What is the nature of the scavenging process that leads
                           210
    to  incorporation  of     Pb  into  sediments?  •  This  is  the

    fundamental question dividing the CF from the CA model.

     c.    How  are  the  processes  of the  first  two  questions

    affected   by  lake  hydrology  and  morphometry?    How  does
                      210                                      210
    residence time of    Pb,  and the total lakewater pool of     Pb,

    affect the scavenging process?


                                                         210
    2.  The  processes  of post-depositional behavior of    Pb  are

    relatively unknown.  Appropriate questions are:
                                                          210
     a.   What  is  the magnitude of vertical movement of     Pb  by

    physical,  chemical, or biological means?  How does lake-type

    influence sedimentary mixing processes?

     b.    What  is  the  effect  of  sediment  focusing,  or  any
                                 210
    horizontal redistribution of    Pb, on dating  procedures?
    2.   The statistical properties,  both of natural variablility

    within a lake's sediments and of the various models used  for

    dating,  must  be  described  in order to  define  meaningful

    uncertainties around dates.
Finally,  The EPA can provide services to standardize measurement
   210
of    Pb from laboratory to laboratory:

    1.  Publish  recommended chemical extraction  and  analytical

    techni ques.
                                  210
    2.  Establish  and maintain a    Pb standard of known  activity

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                                                                 32
    that can be obtained easily by any laboratory.

    3.  Sponsor a series of inter-laboratory comparisons  that  will

    enable  each  lab  to verify its own particular   methods   and

    establish intra-laboratory measurements of variability within

    samples.
                           REFERENCES

Appleby,  P.G. and F. Oldfield.  1978.  The  calculation  of  lead-210

     dates  assuming  a  constant rate of  supply   of   unsupported
     210
        Pb to the sediment.  Catena  5:1-8.

                                                        210
Appleby, P.G. and F. Oldfield.  1983. The assessment of    Pb data

     •From   sites  with  varying  sediment  accumulation    rates.

     Hydrobiologia 103:29-35.

Appletay,  P.G.,  F.  Oldfield,   R.   Thompson,  P.  Huttunen, and K.
                      210
     Tolonen.  1979.     Pb  dating  of annually   laminated  lake

     sediments from Finland. Nature  280:53-55.

                                                            210
Oldfield,  P.G. and F. Appleby.  1984.  Empirical  testing of    Pb-

     dating  models  for lake  sediments.   pp.   94-124   i_n  E.  W.

     Haworth  and  J.  W.  G.   Lund  (eds.).   Lake  Sediments  and

     Environmental Histories.  Univ.  Leicester  Press.

Nozaki,  Y.-,  D.J. Dedaster, D.M. Lewis and K.K.  Turekian. 1977.
                  210
     Atmospheric     Pb  fluxes determined  from   soil  profiles.

     Journal of Geophysical  Research.  83:4047-4051.

Robbins,  J.A.  1978. Geochemical and  geophysical  applications of

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                                                                 33

     radioactive lead, pp 285-393   in J.O.   Nriagu  (ed.).  Biogeochemistr


     Lead in the Environment. Elsevier.  Holland.

Von Damm,  K.L.,  L.K.  Benninger,  and  K.K.   Turekian.  1779.  The
     210
        Pb chronology o-f a core -from Mirror  Lake,   New  Hampshire.

     Limnol. Qceanogr. 24:434-439.

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                                                                       34
     "OTHER RAOIONUCLIDES: PLUTONIUM- WITH SOME COMMENTS ABOUT CSSIUM-137
           CHRONOLOGIES IN FRESHWATER SEDIMENTS".
Merrill Halt* Kevin M. Millar, Philip W. 1C ray, Donald 3ogen and
                        Herbert Fealy
                U.S. Department of Energy
                Environmental Measurements Laboratory
                376 Hudson Street
                NY, NY 10014

I- PLUTONIUM AMD OTHER RADIONUCLIOcS -


     When I was first asked to give this presentation, on the use of so-  called

"other   radionuclides"   (other   than   Pb-210   and   Cs-137)  for  obtaining

geochronologias, my first thoughts mar a to talk about the use of Th, Be, Ru  and

Pu isotopes.  Upon further examination, it became apparent that only Pu isotopes

merited discussion.  The information tnat  could  be  obtained  from  the  other

radionuclides utas redundant and generally added little information to that which

could be obtained from Cs-137/Pb-Z10/Pu-isotopes.  For  example,  the  ratio  of
                                                 *
rh-228/Th-232  has been used to determine if the the surface sediment is present

in a core.  Since the Th-228/Th-232 ratio is in equiliorium, "1, after 8  years,

the theory is that if the surface layer ratio is not > 1, it can be assumed that

the surface of the core mas lost during sampling.  However, the same information

can  be  obtained  from examination of the Cs-137 profile as can the presence of

discontinuities in the distribution of Pb-210.  Similarly, Be-7 and Ru-106, uiith

respective  half-lifes of 53 and 368 days, have bean used by some researchers to

determine nixing rates in aquatic systems.  Again* we can  tell  if  a  core  is

disturbed, i.«.  mixed, by using Cs-137 without thesa additional analyses.


     Because  of  these  factors,  the  discusssion  of  the  use   of   "otner"

radionuclides  to  obtain  geochronologies  mill  be  limited  to  Pu  isotopes.

Furthermore, the discussion will  be  limited  to  freshwater  systems  with  an

emphasis  on  sediments  since we are concerned with acertaining recant Clast <*0

years) pollution histories for acidifi?d soft water ecosystems.   It  should  oc

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                                                                       35
noted that there are significant differences in the behavior of Pu in freshwater




systems and marine/estuarine systems due to the presence of  different  chemical




species.






     As shown in Table lt Pu occurs in several isotopic  forms  with  halt-lives




ranging  from 3 years for Pu-236 to 376t300 years for Pu-242.  Decay is by alpha




release for all of the isotopes with the exception of Pu-241 which  is  by  beta




emission.  It is by measurement of the different alpha energies emitted by these



radionuclides that separation and radiological identification is possible.  This




is  true for the identification of all of the alpha emmitters with thc> exception




of Pu-239 and Pu-240 which have almost identical  decay  energies.   Because  of




this? when only alpha spectrometry is used for Pu isotopic identificat iont these




two  isotopes  are  listed  together  as  Pu-239/240.   Pu-239   can   only   be




distinguished from Pu-240 t>y mass spectrometry.






     The EML method of extracting and measuring Pu in sediments is summerized in



Table  2  and  consists  of  several  steps.   It  should be emphasized that the




procedure is not "cookbook" in that care and skill are required for success.






     There are several sources of Pu in the  environment;   atmospheric  weapons



testing.  satellite  re-entry* controlled discharge and accidents.  Sinca we are




concerned toith  the  use  of  Pu  for  establishing  gaochronologies  in  remote




acidified ecossystems only the first two sources are of interest here.






     The history of Pu inputs into  the  atmosphere  from  weapons  testing  and



satellite  re-entry  is  shown  in  Table  3.   Pu  was  first released into the




atmosphere In the period 1945-1949 at the close  of  World  War  II  and  during



testing in the Pacific.  Howeveri little dabris from these events is believed to




have affected the mainland U.S..  Consequently? fallout from this time period is



not  considered  to  be  of significance for obtaining recent geocnronologies in

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                                                                       36
mainland U.S.  lakes.  In 1951, atmospheric testing began  at  the  Nevada  Test




Site  (NTS)  in  southern Nevada.  Tasting continued at this facility and in the




Pacific through 1958.  It mas  during  this  time  period  that  weapons  debris




entered  the  stratosphere  and  global  fallout  of  anthropogenict radioactive



species occurred.  Major tasting of weapons occurred in 1957 and 1958.  In  1959



and  I960 a noratoriun on atraopheric testing of nuclear weapons was agreed to by




the U.S.  and U.S.S.R..  The moratorium was broken in 1961 and 1962 during which




time   massive  atmospheric  testing  occurred.   In  1963  a  treating  banning




atmospheric testing between  the  U.S.   and  U.S.S.R.   was  agreed  to.   This




resulted  in  a  dramatic  decline  in the levels of fallout radionuclides being




deposited in the environment as a result of atmospheric weapons testing.  In the




years following the test ban treaty atmospheric weapons testing was conducted on




a significantly smaller scale Uy France and the Peoples Republic of  China.   As




shown  in  Figure 1, the period of testing prior to the moratorium was dominated



by the U.S.  while the post moratorium testing was dominated by U.S.S.R..  It is



oelieved  that  the  post  moratorium  weapons  were  characterized ay a greater




neutron flux than the premoratorium tests* and subsequently  produced  different




Pu-isotopic  "signatures"  wnich  may  be used for sediment dating purposes.  In



1964, a U.S.  satellite, SMAP-9A, released a significant amount of Pu-239 during




reentry  into  the  atmosphere  of the southern hemisphere.  The Pu-238 from the



SNAP-9A was first deposited on the surface of the northern hemisphere in 1966.






     EML (formerly known as the U.S.   Atomic  Energy  Commission's  Health  and




Safety Laboratory, HASL) has shown that fallout, i.e.  Sr-90 and Cs-137, follows




closely the pattern of atmospheric weapons testing.  This is shown in  Figure  2



uihere  the  quarterly  deposit  of  Sr-90  in  New York City from 1954 until the



present is shown.  Significant periods of deposition are noted as  occurring  in



1963  and  1959,  reflecting the major atmospheric weapons testing that occurrotl

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                                                                       37
during this time.  Cs-137 has bean shown to follow the deposit of Si—90.  It  is

the  reconstruction of tnese Cs-137 fallout patterns in sediments that allows us
                                                                           /
to reconstruct the time frame for pollution chronologies.  Hence  in  a  parfect


sediment  core  from  a  mainland  U.S.   lake* the Cs-137 profile would closely


follow the atmospheric weapons testing fallout history.  Such a  core  mould  be

characterized as follows:  The core has two peaks* a major peak representing the


significant fallout from 1963 with a secondary peak occurring somewhat deeper in

the  sediment*  representing  fallout  from  1953-59.   The  Cs-137  activity in

sediments younger than 1963 rapidly declines as did fallout since the signing of

the  test  ban  treaty.   There is no Cs-137 downward  tailing below the depth at


which 1950 makes chronological sence.  The  integrated  Cs-137  deposit  in  the


sediment  core  is  equal to the integrated terrestrial deposit from atmospheric

weapons testing.
                                          *

     Me have found that the distribution of  plutonium  in  sediments  generally

follows  that  of  Cs-137.  This is not unexpected since tney ara both primarily

derived from weapons testing.  This is clearly shown   in  Figure  3*  where  the


Cs-137  and  Pu-239/240 activities versus depth are clearly shown to follow each


other in a sediment core from Cayuga Lake* Ithaca* NY.  There are  however  some

exceptions.   For  example  in  Figure  4* the Pu-239/240 at the 65-75 cm depth*


slightly precedes the deposit of Cs-137 in  a  sediment  core  from  Deer  CreeK


Reservoir*  Provo,  UT.   This  is believed to be the  result of Pu entering this

watershed from a source other than glooal  fallout*  namely  material  from  the

Nevada Test Site.  These rasults illustrate the significance of local sources of


radionuclides and how the absence of knowledge about these events  may  lead  to

faulty interpretation of the events in a particular .watershed.

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                                                                       38
     I will riotv discuss the use of Pu isotopic ratios for establishing pollutant




chronologies,,   This  is  the main reason for measuring Pu in sediments since it




provides additional chronological "markers" to that of  Cs-137  and  Pb-210  for




establishing the age of sediments.






     The first example of the use of tnese ratios is that of  Pu-238/Pu-239+240.



In  1964  a  U.S.   satellite  known  as SNAP-9A CSysteras for Nuclear Auxilliary




Pouter) uhich used Pu-238 as a heat source for generating power* burned  up  upon



entering  the  atmosphere  of the southern hemisphere.  As a result* there was a




sharp rise in the level of Pu-233 relative to Pu-239+240 in 1964 in the southern



hemisphere.   The  pulse of Pu-238 from SNAP-9A did not reach the surface of tne




northern hemisphere until 1966 at which time a three fold rise in the  ratio  of




Pu-238  to  Pu-239+240 occurred.  It is the increase in this ratio which is used




as a geochronological marker for establishing the year 1966 in a sediment  core.



This is clearly shown in Figure 5 where the Pu-238/Pu-239+240 ratio dramatically




increases between 13 and 11.5 cm in a sediment core from Cayuga Lake,  NY.   The



year  1966  is  then  assigned  to  11.5 cm which agrees very well with the year




assigned to this depth froi the use of Cs-137 which  peaks  at  13.5  cm.   (The




Cs-137  predicts a sedimentation rate of 0.75 cm/yr, i.e.  1963 is assigned to a




depth of 13.5 cm ,13.5 cm/18 yrs = 0.75 cm/yr, while  the  SNAP-9A  predicts  an




almost identical sedimentation rate of 0.77 cm/yr, 11.5 cm/15 yrs = 0.77 cm/yr.)




It must be emphasized that these two radionuclides have independant  sources  in



the  environment  and  as  such, the excellent agreement in chronologies between



th<»se two methods, provides us with confidence that the dating of this  core  is




valid.

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                                                                       39
      Another   ratio  that  can  oe  used   for  assigning  dates  is  the   ratio




Cs-137/Pu-239+240«   As  shown  in Table 4, there is a significant difference in




the Cs-137/Pu-239+240 ratio in the years preceding and following the atmospheric




weapons  testing  moratorium.  Prior to the moratorium* the ratio taas between 23




and 42 for Cayuga Lake, NY and Lake Ontario, NY.  In the post moratorium period,




the   ratio  at these same locals was found to  be significanly higher, 72-74.  Me




believe  that  this change in the ratio reflects a change in the type  of  weapons



that  oere  used  prior to and after the moratorium with tne premoratorium tests




dominated by  the US and the post moratorium period dominated by  the USSR.  It is



these  ratio   differences that may be used to  obtain the sediment geochronology.




Thus  sediments dating from the period 1952-1959 mould  be  expected  to  have   a




ratio  of  <50 while sediments dating from the early through mid 1960"s would be



expected to have a ratio of > 70.  A failure to achieve these ratio  differences




would  suggest that  the  sediment  core  in question  is mixed or other-wise not




useful for establishing recent geochronologies.






      It  should be emphasized that when we  talk about "Acid Rain" and its related




effects  ae   are really interested in what has happened in the period from about




40 years ago  to the present.  In this regard,  the ratios of PU   described  herin




do infact help to provide chronologies within  this critical time frame.






      The use  of another Pu ratio, Pu-240/239,  for establishing   geochronologies,




.is  shown  in  Table  5.   (It  should be  remembered that a mass spectrometer is




required to separate and measure Pu-239 and Pu-240.) If one were to examine only




polar  region  premoratoriuro (0.24-0.33) and post moratorium (0.09-0.19) ratios,




one could infer that  such  differences   may  be  used  to  distiguish  between



sediments  deposited  in the 1950*s and those  deposited in the 1960's.  However,



we, EML, have found that such differences  do   not  occur  between  premoratorium




(0.11-0.21)   and post moratorium (0.17-0.21) sediments in Cayuge* Lake.  This may

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                                                                       40
be explained by the fact that  Cayuga  lake*  located  on  the  U.S.   mainland*




received  pronoratorium  fallout from different sources than those affecting the




polar regions.  This illustrates the important point that to properly  interpret




Pu  ratios  Cor for that matter any pollutant measured in the environment) it is




critical that all potential  sources  of  Pu  be  considered;   be  they  local*




regional*  or  hemispheric.   For  example* the mainland U.S.  is subject to the




influence of weapons tested at the Nevada Test Site (NTS) in the 1950*3  whereas



samples  taken  in  the  southern  hemisphere would be significantly affected by




deans from tests by Great Britain and Franca* all of which would be expected to




have  different  radionucli.de  "signatures".   Failure  to  take these different




sources  into  account  may  result  in   potential   errors   in   establishing




geochronologi.es.






     I will now summarize aspects of the geochemistry of Pu in  the  environment



which  may  influence its distribution in aquatic ecosystems.  Pu can exist in 4




oxidation states in the environment  and  undergo  several  types  of  reactions



including  hydrolysis*  conplexation  and polymerization.  Such interactions may




influence tho geochronology by altering the rate at which PU is  deposited  into




the sediments.






     Presently* correlations between Pu and pH remain unclear although there  is




some  evidence  that  highly  alkaline  waters Calkalinity > 350 mg/1) have more



dissolved Pu then would have been predicted.  This would suggest that not all of




the  Pu  is  deposited  in  the  sediment in such alkaline systems and hence the




geochronology may be misleading.  Such a situation would have little  impact  in




acidified ecosystems.

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                                                                       41
     There are also reports of  correlation  between  organic  complexation  and




increased dissolved Pu.  If this is true* then one may speculate that soft watar




lakes having elevated levels of hmnic materials*  e.g.   Sagamore Lake in  the  NY




Adirondacks*  may  bind Pu in the water column.  Such  a mechanism could delay or




significantly reduce Pu deposition into the sediments, resulting in a  erroneous




chronology.   Anoxic  Fe-Hn  reducing  waters have also been reported to contain




higher than expected levels of Pu.  It is thus possible  that  some  Pu  may  be




leaving  the  sediments under reducing conditions uhicn could also result in the



establishment of a misleading geochronology.






     In summary* Pu may  serve  as  a  very  useful  tool  for  dating  recently




deposited  sediments.   Pu  can  provide  the  marker   year  1966?  which is not



available with any other radionuclide dating technique.  Ue  strongly  recommend



that  Pu  be used in conjunction witn Cs-137, Pb-210 and as many other "markers"




as available so that one can obtain as a reliable a chronology as possible.

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                                                                       42
II- PART fl: COMMENTS ON THE USEFULNESS OF CS-137 FOR EVALUATING SEDIMENT CORE



            QUALITY.






     I will now discuss soi« aspects of our CEML)  experience  using  Cs-137  to




date  lake  sediments  and offer comments on a "tentative" method for evaluating




the quality of sediment cores  for  obtaining  clear  and  meaningful  pollutant




geochronologies.






     Our concern is  not  with  which  radioactive  methodCs)  CCs-137t  Pb-210»



Pu-isotopes)  are  correct*  but  rather  "IF* slow sediraanting* soft-water lake




sediments  cam  be  accurately  dated  and  meaningful   "pollution*   histories




established.   There  is  no  doubt that W9 can date the age of sediments on the




long term * i.e.  thousand*? of years* but in general,  THE  ACCURATE  DATING  OF




RECENTLY  DEPOSITED « 100/ears old) SEDIMENTS FROM SOFT WATER LAKtS IS FAR FROM



CERTAIN.  Until this situation is clarified*  we*  EML*  have  dacided  only  to




reconstruct   pollution   histories   in   lakes   which   have   tha  following



characteristics:




        A3 A clear 1963 Cs-137 peak with a sharp falloff, eg. little




           "rat-tailing" of Cs-137 downward.



        3) Tha "zero* point for Cs-137, ie. 1952 */- 2 yrs, is in good




           agreement with the sedimentation rate estimated from other "markers"




           such as Pb-210* organics, pollen etc.






     It should be noted that we have not met these criteria in  any  soft-water,




natural  lakes  that  we  have so far sampled in the NY Adirondack Preserve.  We




have, nowever, mat these criteria in several lakes witn  sedimentation  rates  >




0.5  cm/yr  in  locations as diverse as the NY Finger Lakes * The GA/NC/TN Smoky



Mountains* Tha CO Rocky Mountains*  and  the  UT  Wasatch  mountains.   However*



sedimentation  rates  of  this  magnitude  or greater by no means guarantee that

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                                                                       43
useable cores can be obtained.  We have had several failures from lakes which me




considered to be prime candidates for providing useful sediment chronologies.






     The following two tables, Table 6  and  Table  7  illustrate  the  type  of




problems me often encounter in dating soft-water, slow sedimenting lakas.  Table




6 shows the difference in  tne  age  of  sediment  layers  from  t-jio  soft-water




Adirondack  lakes  determined  by  Pb-210 and Cs-137.  The differences are quite




dramatic for Woods Lake at the 6-7 cm.   increment  where  the  age  assignments




differ  by  65  years.   A  similar situation was found for Sagamore lake at the




10-11 cm.  increment.  The proulem is how can  Cs-137  be  present  in  sediment




older  than  1945  since  this radionuclide is a fission product and as such can




only be present in the environment from atmospheric atomic explosions?  Some may




argue  that  the  Cs-137 is obviously diffusing or mixing and as such is carried




downward to an earlier time.  We do not disagree.  WE 00, HOWEVER, DISAGREE WITH




THOSE  WHO  CLAIM  THAT  THE  Cs-137  MAY  BE THE ONLY CONSTITUENT MOVING IN THE




SEDIMENT COLUMN.  WE BELIEVE THAT IF THE CS-137  IS  MOVING  IN  SEDIMENTS  TH4T




THERE  IS A HIGH PROBABILITY THAT OTHER POLLUTANT AND TRACER CONSTITUENTS IN THF




SEDIMENT ARE ALSO IN FLUX INCLUDING OTHER METALS SUCH AS Pb-210 AND THAT EFFORTS




TO  ASSIGN  MEANINGFULL  CHRONOLOGIES TO SUCH CORES ARE FROUGHT WITH UNCERTAINTY




ANU MAY INFACT BE "GUESTIMATES".






     An example of this situation is shown in Table 7 where the age at wnich DDE




(a  "beakdown  product"  of  the  chlorinated  pesticide  DDT)  first appears in




sediment from South Lake, an acidic soft-water  lake  in  the  N.Y.   Adirondack




preserve, is compared using the dating techniques of Cs-137 and Pb-210.  DDE mas




first detected in the sedivent at a depth of 9-10cra.  Pb-210 assigns a  date  of




1938  to  this  sediment  increment.   Since  Cs-137  is  first detected in this




sediment layer, it is assigned the date 1950.  DOT, nowever, was not used to any-




great  extent  until World War II.  Since we find both Cs-137 and OOr present in

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                                                                       44
the  Pb-210  "1938"  sediment  layer,  which  is  clearly   impossible   if   no



diffusion/mixing ware occurring , these data would support our statement that if




Cs-137 is moving so are other constituents.  This situation  must  be  rectifiad




before  we  can have confidence in any projections of future pollutant trends in




the environment or the establishment of clear cut time frames for the  onset  of




acidification in such aquatic ecosystems.






     This situation of conflicting chronologies does not occur  in  lakes  where




the  Cs-137  distribution  in the sediments follows that predicted by the global




fallout history.  An example of this is shown in Figure 6 where  the  stable  Pb




and fluoranthene Ca PAH produced by incomplete combustion) concentrations versus




sediment depths dated by both Cs-137 and Pb-210 are shown for Cayuga  Lake,  NY.




It  is  clear  from this Figure that the time frames? i.e.  sedimentation rates,




determined independently by  these  tao  methods'  of  dating  are  in  excellent



agreement.   It is also clear from this Figure that the Pb and fluoranthane have




different distributions in the sediment with the  former  peaking  in  the  late



1960*s  and  the  latter  by trie early 1950s.  This indicates that the sediments



from this lako are not mixed or diffused to any  great  extent  and  that  clear




pollutant  trends can be established.  It should be noted that inadaition to the




Cs-137 and Pb™210» the Pu-isotopes, Ambrosia rise* and other  dating  techniques




are  also  in  excellent  agreement for this lake*  These results amphasiza that




when tnere is good agreement between Cs-137 and Pb-210, one  can  be  reasonably



confident that, the pollution chronologies are also raasonabla.  Again, we at 6ML



have not had this success in slow sedimenting soft-wat»r lakes and as yet do not




feel 'assured  that  such  lakes  can  provide  the required temporal resolution



required for determining recant deposition  histories.   This  problem  must  *3e



addressed.

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                                                                       45
     I think it is appropriate at this point to mention how me at EML  take  our



sediment cores.  We use a 21 cm.  diameter sphincter cor«r which is Lowered from




a specially designed 22* X 12' Catamaran.  The  Catamaran  is  portable  in  the




sense  that  it  is  assembled  in  tha  field  but  due  to its waight* must be




transported to close proxiaity with the lake to be sampled.  It cannot be  taken




very  remote  sites unless it is used in conjunction uith a helicopter.  It doas




however, provide an excellent stabile platform for taking sediment  cores.   The




prima  advantage  of  the  EML Catamaran coring sytem is that you can take large



volume* large diameter cores* and have enough sediment at each 1 cm.   increment



to  measure  several  classes  of  pollutants including trace alamants* organics




radionuclides* pollen* diatoms* charcoal* etc.






     In regard to quality control* we think that it is very important to take at




least  duplicate  cores  from  each sampling site.  It is also critical that the



sediment cores be taken from appropriate locations.  Wa  define  an  appropriate




location  as  a  site which is not likely to be influenced by sediment focusing*



slumping or depletion.  Such appropriate sites are usually found in  lakes  with



rather  large uniform basins in which the cores are taken away from any areas of




discharge or inflow into the laka.  In order to find the most appropriate  sites




it  is quite useful* perhaps critical that the bathymetry of the basin ba known.




We accomplish this with  the  use  of  depth  recording  equipment  onboard  our




Catamaran.  It has been our experience to find that not all lakes* even with the




most carafull forethought and planning will yield acceptable sediment cores.  We




have also found that when we get excellent cores* we get all excellent coras and



'unfortunatly*  when  we  get  unacceptable  cores  they   are   invariably   all




unacceptable.This  leads  us to believe that it is not the equipment that we use



that may be causing chronological  problems  but  rather  the  dynamics  of  the




sediments  in  the  lakes.   Figure  7  is  given as an example of the potential

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                                                                       46
raproducibility of our method of coring.  Shown are the Cs-137 profiles CmCi/km2



versus  depth)  for  two  cores  from  Cayuga  Lake* A and B, taken within a fo*



hundred meters from each other in 130 ra.  of  mater.   It  is  clear  from  this




figure  that tne two cores are almost identical in their Cs-137 distributions as




well as total integrated deposit of Cs-137.  To date* we have taken a  total  of




12  cores  from  Cayuga  Lake*  over  a  distance  of  24 km., all of which show




excellent agreement between their integrated Cs-137 deposits  and  sedimentation



rates.






     The Cs-137 integrated deposit may be defined as the total  Cs-137  activity



per  unit  area  in  the sediment core.  The units that me use are mCi/km2.  The




Cs-137  integrated  deposit  is  an  important  concept  since  it  can  provide




information  on  watershed  dynamics.   A  sediment core having a perfect Cs-137




integrated deposit would be one in which tne deposit in the  core  is  equal  to




that  found  in  an  undisturbed  terrestrial  location  in the watershed or the




equivalently documentented fallout from atmospheric weapons testing  Cif  it  is



available  for that particular area of the U.S., from EML (formerly known as the




U.S.  Atomic Energy Commission Health  and  Safety  Laboratory  or  HASD).   It




should be noted that if the former method is used for determining the integrated



deposit for the watershed* great care must be taken in the selection of the site




since  many  locations  that  appear to be undistrurbed in fact are not.  If the




integration in the sediment core equals that deposited on the land*  this  would




indicate  that  the sediment is little influenced by shoreline runoff and all of



the deposit is atmospheric.  Unfortuately* this is  rarely  the  case  for  
-------
                                                                       47
the expected terrestrial deposit.  Such a situation suggests that only a portion




of the atmospheric deposit  is  reaching  the  sediment.   The  causes  of  this




situation  are severalt all of tuhich may decrease our ability to establish clear




pollution geocnronologies.  Among the possibilities are:




        1- Sediment focusing in which sediment from one portion of the lake




           is being transported to another.




        2- Sediment slumping in which case the core was probably taken on a




           slope and with continued buildup the sediment collapses and "rolls"




           to another location.




        3- Storms or floods transporting sediment into or out of the




           system.




        4- Ice on the lake for a good portion of the year with a flushing of




           the material deposited on the ice by currents during the time of




           melt (We think that such a mechanism may be operating in several




           soft-water lakes in the Adirondacks where tne integrated




           deposits are far below the expected.).




        5- Biological uptake and resuspension by plankton blooms. (Such a




           mechanism as been used to explain this phenomena in soft-mater




           lakes in Australia).




        7- Anthropogenic disturbances such as dredging or channndlization.






     We now present a  TENTATIVE  method  for  evaluating  core  quality  solely




through  use  of  the  Cs-137  distribution  its  total integrated deposition in




sediment.  We believe that this  method  may  be  very  useful  for  determining




whether  a  particular  sediment  core  may be successfully used for determining




recent polllution geochronologies.  This method classifies the  cores  by  group




with  outstandining  "A**  cores at the top and useless "F" cores at the botton.




For each group we have enclosed examples of one or more  Cs-137  profiles  which

-------
                                                                       48
are    representative    of    each   "core   type".     Also   shown   are   the




requirements/characteristics for placement  in  each   group  and  the  kinds  of




information that may provided.

-------
                                                                       49
1- -A*" CORES CS«« Figure 3, Cayuga Lake. Ithaca* N.Y.)
        Requireraen ts«




        1- Cs-137 profile closely follows the atmospheric weapons testing




           fallout history. The core has too peaks* a major peak




           representing the significant fallout from 1963 with a secondary




           peak representing fallout from 1958-59. The Cs-137 activity in




           the sediment younger than 1963 rapidly declines as did the weapons




           testing since the test ban treaty between the U.S. and U.S.S.R..




           (This illustrates that the core is not mixed since mixing could




           result in a sediment core in which material from the 1963/1959




           period would be united with that from more recent times resulting




           in a pattern in which the Cs-137 does not decrease in the manner of




           fallout history, CSae Cora type "C", Figure 12, Bear Lake). There




           is no Cs-137 downward tailing balow the depth at whicn 1950 makes




           chronological sense. (This indicates that the core is not diffused




           since diffusion of Cs-137 would result in a tailing effect with the




           Cs-137 peakCs) remaining stationary. See Core type "0", Figure 13»




           Dart Lake).




        1- The integrated Cs-137 deposit is within a factor of two of the




           terrestrial deposit.




        USE:




        1- Obtain the true geochronology within a time resolution of 1-2




           years.




        2- Obtain a good " astiraate" of the atmospheric pollutant flux to the




           land/shore. Obtain accurate measurements of the combined




           (atmospheric + natershed) pollutant flux to the sediments. (Note:




           to obtain an accurate and precise assessment of the relationship of

-------
                                                              50
   the flux to the  sediment (composed of atmospheric and watershed




   inputs)  compared to  the atmospheric flux to land/shore,  it is




   critical that the integrated deposits for the pollutants in question




   »i.e.  polycyclic aromatic hydrocarbons*  PAH* ate.,  be measured in




   undisturbed sites within the watershed.  This is because  one cannot




   be certain that  such pollutants will behave in the  same  manner as



   Cs-137»  i.e. they may not be transported through the oiatershed to




   the sediments with efficiencies identical to Cs-137. Hencat while




   Cs-137 may provide a "yardstick" for comparative purposes* actual




   terrestrial measurements of the pollutants in question are




   required before  one  can have unequivical "faith", even in "A*"




   sediment cores*  for  obtaining true measurements of  atmospheric flux




   and integrated pollutant deposits.



3- Obtain a good "estimate" of the atmospheric integrated deposits of




   anthropogenically derived pollutants such as trace  metals (TM) and



   PAH to the sedinents. (Note: the same warning applied to the




   accurate and precise determination of atmospheric flux to the



   sediments* see above* is appropriate here.) Obtain  accurate




   measurements of  pollutant deposit (atmospheric + watershed) to the




   sediments .

-------
                                                                       51
2- "A" CORES (See Figure 9» Deer Creek Reservoir, Provo UT).
        Requirements:

        1- Same as for "A*" cores aiith the following exception;

           The integrated Cs-137 deposit is greater than a factor of two of tha

           terrestrial (land/shore) deposit.

        USE:

        1— Same as for "A-*" cores aith the following exception:

           Since the integrated Cs-137 deposit is greater than a factor of

           too of the terrestrial deposit, the potential error in any estimates

           of atmospheric flux and integrated deposition of pollutants to

          ' the land/shoreline will be greater than for the "A+" cores.

           Measurements of combined (atmospheric •*• watershed) pollutant flux
                                           «
           and combined integrated deposition to the sediments are unaffected

           and remain accurate.

-------
                                                                       52
3- «3+" CORES CSee Figure 10t  Grand Laket Granby, CO.)
        Requirements:




        1- Sam« as for "A" coras with the following exception:




           The Cs-137 curva shows some suggestion of sediment mixing (the




           drcpoff of Cs-137 in post 1963 material is not as sharp as it




           should be according to fallout history) and/or diffusion Cthe Cs-137




           detaction depth shows some downward tailing).




        Use:




        1- Obtain a geochronology within a time resolution of greater




           than 1-2 years but less than 5 years.




        2- Obtain an estimate* with some uncertainty (due to the ralatively




           minor amount of mixing/diffusion in such cores) of combined



           pollutant flux to the sediments (atmospheric + watersned). Since




           there is evidence of mixing and or diffusion, the potential arror



           in any estimates of atmospheric pollutant fiux to the land/shoreline



           will be potentially greater than for the "A* cores.



        3- Obtain accurate measurements of the combined integrated deposits



           (atmospneric «• watershed) to the sediments of pollutants such TM and




           PAH.

-------
                                                                      53
- "B" CORES CSee Figure 11, Echo Rseservoir, Coalville, UT)
       Requirements:




       1- Same as for "A" cores with the following exceptions:




          The Cs-137 curVe shows only a single peak which is a combination




          of the 1959 and 1963 peaks. Little evidence of sediment diffusion




          or mixing.



       2- The integrated Cs-137 deposit is greater than a factor of two of tha




          terrestrial Cs-137 deposit.



       Use:



       1- Same as for "A" cores witn the following exceptions:




          Obtain tha geoc hronology within a time resolution of about  5



          years.




       2- All estimates of atmospheric flux to the land/shoreline,




          as well as combined (atmospheric * watershed) flux to the sediments



          have considerable potential error due to the 5 year chronological




          resolution of such cores. (This is the lowest class in our  hierarchy



          of core types that can be used for such estimates.)




       3- Obtain accurate measurements of the contained (atmospheric +




          watershed) integrated deposits to trie sediments of pollutants such




          as TM and PAH.

-------
                                                                       54
5- "C" CORES (Sea Figure 12.  Bear Lake, Logan. UT.)
        Requirements:




        1- The Cs-137 profile foilous the fallout history up to a point*




           There is a only a single peak* as for type "B" cores* but there is




           clear evidence of sediment mixing and/or diffusion. In this




           regard, the Cs-137 activity in sediments younger than 1963 does not




           rapidly decline as 'did the fallout from weapons testing since the




           test ban treaty between the US and USSP. In addition, there



           may be tailing of Cs-137 below tha depth at which 1950 makes




           chronological sense.




        2- The integrated Cs-137 deposit is aqual to or greater than the




           terrestrial deposit.



        Use:




        1- Obtain the geochronology within a time resolution of about 10-20



           years.




        2- Meaningful estimates of atmospheric polllutant flux to the



           land/shore are not possible. Estimates of the combined




           (atmospheric * watershed) flux to the sadiments are "rough




           gue stimates" at best.



        3- Obtain an acceptable measurement of the combined



           (atmospheric + watershed) integrated deposits of pollutants such as




           TM and PAH to the sediments.

-------
                                                                       55
6- "D" CORES (See Figure 13, Cart Lake, Inlet NY)

**************************************************

        Requireraen ts:

        1- The same as for "C* type cores with tne following exceptions:

           The integrated Cs-137 deposit is significanly less than the

           integrated deposit found at local, undisturbed, terrestrial

           site(s) or the expected "EML/HASL" value. The dates assigned by

           Cs-137 dating clearly do not agree with those from Pb-210  dating,

        Use:

        1- Obtain the geochronology within a time resolution of about

           50-100 years.

        2- The combined (atmospheric + watershed) flux, as well as

           integrated deposits of pollutants to the sediments cannot  be
                                            *
           measured or even estimated with any confidence.

-------
                                                                       56
7- "F" CORES (See Figure 14-15,  Woods Lake* Woods Lake* NY, and Pineview



            Reservoir,  Ogdant  UT)
        Requirements: CThere are two catgories of "F" cores.)




        Category 1. (Woods Lake* Woods Lake,  NY)




        1- The same as for "0" type cores with the following exceptions;




           the highest activity of Cs-137 is  located in the surface layer




           of sediment followed by a tailing  downward.




        Category 2. (Pine View Reservoir, Ggden* UT)



        1- The Cs-137 activity never reaches  "zero" to the bottom of tne core.



        Use:




        1- Neither category of "F" cores may  be used to obtain a pollutant




           geochronology or any estimate of pollutant flux or integrated




          deposition with any confidence.

-------
                                                                        57
TASLe 1- SOME PROPERTIES OF PLUTONIUM








        ISOTOPE         HALF-LIF£Ctl/2)           DECAY           ENERGIES  CMeV)
        Pu-236               3 yrs.              Alpha            5.77  (69?)




                                                                 5.72  C31?)




        Pu-238              87 yrs.              Alpha            5.50  C72*)




                                                                 5.46  C28X)




        Pu-239          24,131 yrs.              Alpha            5.16  C38*)




                                                                 5.11  Cll*)




        Pu-240           6t570 yrs.              Alpha            5.17  C76?)




                                                                 5.12  (24?)




        Pu-24l              13 yrs.              Beta             0.021 max




        Pu-242         376,300 yrs               Alpha            4.90  (76*>




                                                                 4.36  C24?)

-------
                                                                       58
TABLE 2- EHL METHOD OF EXTRACTION AND ANALYSIS OF PLUTONIUM IN SEDIMENTS



«*$*?*«$ ««*#****];:««£$#«*«#«*$* ******:




1) 10-20 5 of dry sediment required.




   Pu-236 is used as a tracer to determine yield.




   (Minimal contamination of Pu-239/?u-240)




2) Mineral acid decomposition with HCL/HN03.




   Require a complete decoaposition of all organic material.




   Pu recovery is very sensitive to organic ligand complexation.




   Combustion above can 450 C result in highly insoluble Pu oxides.




3) Collection step! Co-precipitation of Pu using Ferric hydroxide etc.




   leaving the remaining bulk matrix in solution.




4) Anion exchange separation: removes all of the natural contamination




   present in the precipitate* i.e. U and Th.




5) Electro-deposition on Pt disks for radiometric assay.




6) Measurement by alpha spectrometry using multi-channel analyzer:




   9 EML: Pu-238, 239/240, 236.




   (Require Pu-236 yields of 50-75?, with resolution of the alpha 50-60 keV




   a 1/2 width full max.)




7) Mass-spectrometry is required for the atom ratio of Pu-239/240.

-------
                                                                       59
TABLE 3 - Pu INPUTS INTO THE ATMOSPHERE FROM WEAPONS TESTING  AND  SATELLITES




#*****************************************************************************




1945-1949   1951	1958     1959-60       1961-62     1963       1966     1964-8









    I         I         I           I            I          I          I         I




    ?        NTS     Major    Moratorium    Major    Test  San  SNAP-9A     Mine




                     Tests                  Tests.     Treaty               Test




***********************************************************<^*^
TABLE 4- Cs-l37/Pu-239+240  RATIOS  WHICH  MAY  BE  USED AS GEOCHRONOLOGICAL TOOLS




*********************************************************************^





                                                                 LOCATION




                                                                **************




  PRE-MORATORIUM





                                                                LAKE ONTARIO




                                                                CAYUGA LAKE




   POST-MORATORIUM





                                                                CAYUGA LAKE




                                                                LAKE ONTARIO
YEAR
******
1952-54
1951-58
1965
19S5
RATIO
*****
25
23-42
74
72
SOURCE
********
EML/WHOI
EML
EML
WHOI

-------
                                                                       60
TABLE 5 - Pu-240/Pu-239 RATIOS WHICH MAY BE USED AS GEOCHRONOLOGICAL TOOLS
                        YEAR
  PRE-MORATORIUM
   POST-MORATORIUM
RATIO
*****
 SOURCE
********
1952-53
1951-58
1961-1973
1950-1979
0.24-0.33
0.11-0.21
0.09-0.13
0.17-0.21
SCRIPPS
EML
SCRIPPS
EML
 LOCATION
******* *******

POLAR ICE CAPS
CAYUGA LAKE

POLAR ICE CAPS
CAYUGA LAKE
* ATOM RATIOS

-------
TA3LE - 6       TIME FRAME FOR SAGAMORE AND WOODS LAKES
                APPROXIMATE AGE RELATIVE TO SURFACE
SEDIMENT        SAGAMORE LAKE            WOODS LAKE




DEPTH CcnO      Pb-210  Cs-137          Pb-210  Cs-137
 6-7            1953    1961            1890    1955



10-11           1890    1951            	     	
                                                                       61

-------
                                                                        62
TA6LE 7 - ODE DISTRI3UTIQN  IN  SOUTH  LAKE SEDIMENT




        c:M:****3**************5




        ODE            Cs-137




        DEPTH           DEPTH                           DOT




        FIRST           FIRST           Pb-210         FIRST




        DETECTED        DETECTED          DATE        WIDELY USED
        8-10 cm.        9-1D cm,          1938          '1945




                        C1950)



4*4***********4^**4***#:re^

-------
-
                 V=«?SUS
                                                  63
                FRANCE
                RR. CHINA
        1950
1960
  YEARS
                                        1970
1975

-------
QUARTERLY DEPOSITION OF STRONTIUM - SI
              YORK CITY
.
1963

      1959

                  91
                  5;
                  1

-------
FIJL.st  3- CS-lj? VERSUS  PU-239*2*0 , CAYU5A LAK£.
                           CAYUGA  LAKE -  CORE A - 1981
      CT)
     CJ
      CL
     CD
      I
      in
     CJ
10

DEPTH
                                                 15
                                              (cm)
20
                                                                                o
                                                                                •^r
                                                                                CXJ
                                                                                +
                                                                                CD
                                                                                OJ
                                                                                 i
25
                                                                                  en
                                                                                  in

-------
iu-'i 4- :S-1;7
             PU-239*2'»0, OEfR C3E5K RfSERVLIR.
CJ
CL
en
 I
 en
CJ
                DEER  CREEK  RESERVOIR  - CORE 0  - 1982
               10      20
                                 30     40     50

                                   DEPTH  (cm)
60     70      BO
                                                                          O\

-------
    5- ?U-2 3fc/P J-239+240 rtATIO Vr»SUS CS-137  AND PU-  239*2*0.

                   OEcR CI?E=K RESERVOIR.
                        CAYUGA LAKE  -  CORE A -  1981
      2. 5 1 — i
 en
 CL
en
-c-l
 i
in
CJ
                                                            0.25 .2
PU-23B/PU-230+240 RATIO
                                  10           15

                                   DEPTH  (cm)
                                            20
25

-------
                    Pb CONCENTRATIONS  versus YEAR  (CS-137)

                                  CAYUGA  LAKE C
                                                                                                               68


                                                                               Pb CONCENTRATIONS  versus YEAR  (PB-2I0)

                                                                                             CAYUGA  LAKE 'C
 
-------
FIGURE 7- COMPARISON OF Cs-137 DISTRIBUTION VERSUS DEPTH IN DUPLICATE CORES.
              40 1 — i  i  t  i
              30-
          ru
          CJ
             20
          en
           i
          en
          CJ
                                      CAYUGA LAKE
4 — i — i — | — i — ii  i — | — • — t
                                CORE A



                               , CORES
                                            -JT
                                                                     i i
                                        H	1	\	1	1	1—I	1	1	1 ' "t 1 I'"""1	1—4	H
                                  10
               15
20
25
30
                                      DEPTH  (cm)
                                                     en
                                                     10

-------
         -i.lTIVlTf VE^S'JS CfPTH, CAYUGfl LAKE, NY.
     3 0,	H
     2 5--
OJ
     2 0--
     1 5--
cn
 I
 CD
C_3
     1 0--
                          CORE  A    LAKE  CAYUGA
H	1	1	1	1	1	1	1	1	1	1	1	1	»——I	1	1	1	1	1	H
              I=lBBmCi/kmt2
            i   i—i—|	1—i-
                               _T
                                10            15

                                DEPTH  (cm)
                                                              i
                  H	1	1	1	1	1	1	1	1	1	1	1	»-
                                         20
25

-------
    ,- Ci-u7  t:i;viir /tssus  CEPTH, OC;R C*E=K  RESERVOIR. UT,


                             CORE  0     DEER  CREEK
      2 5
     2 0--
OJ
      i 5--
CJ
r--
co
T-H
 I
en
CJ
       5--

 I I I I I t I I I I I I I I I HJ I I I \ I I I I I I I I t I I I > I I I I I I I I I I I I I I I I I 1 I I I I I I I I
                  1=469 mCi/kmt2
                                              I
                               1
       01 i t i i i r i M I M > i i > i t i I i t i i i i i i i I i i i i t i i i t-f-i i t i t i i i i I i i i i i i i i i I i i i i i i i t i I i i t i irl-t
                10
20
30
40
50
60
70
80
                                   DEPTH  (cm)

-------
   10- C--137 ACTIVITY VEXSUS JtPT^I  , oRANCJ LA,\E, CO.
    40 I—i—i
CXJ
C_3
r--
en
•r-H
 I
cn
CJ
    35
    30
    25
    20
15
    10
                          CORE  W   GRAND LAKE
                                         I=260mCi/kfi?
                                                   1  I  »	»==»
                          10         15          20

                               DEPTH   (cm)
                                                                  30
                                                                                    ro

-------
11- Cs-137 -iCFlVITY VffcSUS 'J5PTH ,  fCHO LAKct UT.
                       CORE  J    ECHO  LAKE
25
     i i i i | i » i i I i i i i | i » i > | i i i t | i i i t | t i i t | i i i > | t i i i | > i i i | > i i > | t > i > | i i i i
  0' » i i i | i i i i | i > i » | i i i > | i > t > | » i i i i » > > > | t i i t | i i i t | i i i i \ i t i i
   0     5    10    15   20   25   30   35   40    45    50   55    60   65
                            DEPTH   (cm)

-------
CORE A    BEAR LAKE
1.8
1.6-
OJ 1.4
EE
^ 1.2-
• r-i
e «•*
r-- O.B-
CQ
(!n o-6-
CJ
0.4-
•0.2-
0 .0
I 1 1 1 | • t -— 1 	 1 — -1 — — |- --•!—• t 1 	 1 	 1 	 — t— — — 1 	 1— 	 1 '-| 	 1— — — 1 	 1 1
1=183 mCi/kmt2
-r^l :
r-'" "1
1 1
r"'r L -
- r L
i *"

	 1 1 	 1 l 1 	 1— 	 1 	 1 	 1 	 I 	 1— — i 	 i -i— 1 i 	 1 — JC.. . 1 --JH 71 — -•.— i *=r— : t_
    10
15
25
    DEPTH  (cm)

-------
rliUil.
              ~I:«:TY VERSUS
                                   L«€. NY.
                                DART LAKE CORE  N

                                                  • I • •
                                   DEPTH  (cm)
-vl
cn

-------
              It-  Ci-137 -* •'.   VcRSUS  0£PTri  ,WQOOS LAKE  NY
    O
    CM


    00
I

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UJ

§  2

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    (VJ
(vj   5j-   to      o   (vi


          (uuo) Hld3Q
                                        (0   00

-------
.,-
           ,-,C£,,l«4TIfl., .CISUS 05PIH.  >
                                          e.  
-------
                                                                 78
VARVED SEDIMENTS IN CHRONOLOGY
Ingemar Renberg, Dept. of Ecological Botany, Umea University,
S-901 87  Umea, Sweden.
Already 1920 Nipkow published a paper about the varved recent sediment
of Lake Zurich in Switzerland. This is an excellent paper which really
constitutes the beginning of the research about varved lake sediments.
A large number of papers have been written since then. Particularly,
during the last decade the number of investigations have increased
markedly. O'Sullivan (1983) has published a review paper containing
170 references, all of which not dealing with varved sediments, but
most of them do. It is not at all surprising that so much attention has
been paid to these sediments during the last few years considering their
great value for so many kinds of paleoenvironmental studies.

In this paper the intention is not to bring up all potential applica-
tions of varved sediments, but focus on some basic information about
the formation, composition and appearance of varved sediments and on
varve-counting and other things closely related to the chronological
aspect.


Terminology

It is necessary to start with a few words about the terminology. In
this paper the term "a varve" is used to denote a distinct sediment
deposit accumulated during the course of one year. Consequently, a
varved sediment is a sediment stratified in such a manner that it is
possible to distinguish between the deposits of individual years.

The word varve is a short precise expression, which, ever since De
Geer defined the term at the beginning of this century (see De Geer
1940), means, the sediment deposited during one annual cycle. There
is no real principal difference between these classical clay varves
and lake sediment varves. Both are formed in fresh waters and depend
mainly on a seasonality of sediment supply. Therefore, there is no
reason to restrict the use of the term varve to varved minerogenic
sediments deposited during the deglaciation.

The corresponding terms most frequently used in English literature
are "an annual lamination" and "an annually laminated sediment".
A number of other terms have also been used (see e.g. O'Sullivan 1983).


Varve formation

There are two prerequisites for the formation of varves:

(a) that different kinds of materials accumulate during different
    seasons of the year,

(b) that no mixing of the sediment takes place by water movements,
    bioturbation or gas bubble formation.

-------
                                                                   79
Point  (a)  is  fulfilled in most temperate lakes and will  be  discussed
further  in the following chapter "Varve composition".

Point  (b)  is  fulfilled in several lakes, namely in meromictic  lakes
or  in  deep dimictic lakes stratified for long periods  and with anoxia
in  the hypolimnion. Stratification of the water column reduces water
movements,  and anoxia inhibits the activities of benthic organisms.
Consequently  the  best varves are formed in the deepest part of a lake
basin  (Fig.  1).
                            A dimictic lake
  no varves
                                                                6 m
                                                 Varve formation
                                                 ceases
                                           — Wavy and disturbed
                                              varves
               The best varves are
               formed here where
               anoxia last longest
Fig. 1. A generalised  drawing of a dimictic lake with varved  sedi-
ments. Varve quality is  highest in the deepest part of the  lake
basin and deteriorates with decreasing water depth.
Varve composition

The variation  in the  composition of the material deposited on  the
lake bottom is caused by  a seasonality in:

(a) the allochthonous inflow,

(b) the organic production in  the lake,

(c) the chemistry of  the  lake; calcite precipitation, sulphur precipi-
    tation, precipitation of iron etc.

The first two points  are  the most important ones involved in the  forma-
tion of a varved lake sediment.  The chemistry of the lake usually
influences the formation  processes too, but generally to some  lesser
extent.

-------
                                                                 80
O'Sullivan  (1983) distinguishes  five  types  of varved  sediments:

(a) clastic
(b) biogenic
(c) calcareous
(d) ferrogenic
(e) thiogenic

This division requires  some  further explanation.

(a) The  classical varved  clay  is the  best example of  clastic varves.
Varves consisting mainly  of  mineral grains  are  sometimes  deposited  in
lakes too, but  their  low  organic content make them  less interesting
than biogenic varves  for  paleolimnological  studies.

(b) Biogenic varves also  contain mineral grains but the organogenic
matter is more  predominant.  Most of the varved  lake sediments  in
Sweden,  Finland and probably in  N. America  must be  characterized as
biogenic varves.

A typical varve from  a  lake  in an area with a climate like  the N.
.Swedish, characterized  by long winters with snow and  ice, is shown
in Fig.  2.
Fig. 2. A micro photograph of a thin-section showing one varve  from
a N. Swedish lake  (from Renberg 1981 ).  A piece of varved sediment
was treated with polyethylene glycol, microtomed and photographed in
a lightmicroscope.

(A) is a layer of mineral grains deposited during the spring flood
period after the snow-melt.
(B) is the summer-autumn layer which consists of organogenic material,
such as remains of algae, animals, plants etc.
(C) is the winter layer which consists of fine grained, mainly orga-
nic matter. This layer is deposited during the ice-covered period of
the year.

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                                                                   81
Lakes in other  climatic regions must be  expected to have varves with
another sequence of the units which build  up the varve.

The composition of the sediment deposited  during the productive sea-
son of the year depends on the flora and the fauna of the lake and on
the conditions  of the watershed as well. Diatoms and remains  of
Chrysophytes can be abundant in the summer-autumn layer. Simola  (1977)
and others have shown by the adhesive  tape technique, that  seasonal
diatom successions can be recognized within the varves. Battarbee
(1981) has shown the same for cysts of Chrysophytes.

(c) Calcareous  varves are found at the classical site for varved  lake
sediments, Lake Zurich (Nipkow 1920).  To this category belong also
several lakes  in N. America studied by Ludlam (1969, 1979)  and others,
Kelts & Hsu  (1978) have studied the varves in L. Zurich and they  have
presented a  drawing showing the composition of those varves (Fig. 3).
 Autumn
 Late spring
 Lulu iiulumn H wintur
Micrite (1-4 pm), aggregates
plankton Incl. dinolluuyulutos
some diatoms

Larger calcite polyhedra, diatoms
Diatom blooms

Organic substrata, blue-green algae
iron sullidut, linu mlnural detritus
Fig.  3.  The composition of the  calcareous varves in Lake  Zurich.
From  Kelts  & Hsu (1978).
Calcareous varved sediments  are  not so interesting when  dealing with
acidification. That kind of  varves can of course not be  found in
areas  sensitive to acidification.

(d)  0'Sullivan (1983) distinguishes a ferrogenic varve type.  Whether
this is correct or not may be  discussed. Most probably iron plays no
role in the varve formation  process as such. Iron is more of a cos-
metic;  it makes the varves beautiful and distinct (Fig.  4), or often,
causes  complicated light and dark laminations within the varves (Fig.
5).

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                                                                 82
Fig. 4. A photo of a frozen sediment. A,B,C and D form together one
varve deposited 60 years ago. During the oxic periods in the hypo-
limnion, during and after the overturn perio.ds in spring and autumn,
a sediment coloured brown (light) by iron hydroxides is deposited
(A and C, respectively). During the anoxic periods in summer and win-
ter a sediment blackened by iron sulphide is laid down (B and D).
The main composition of this varve is the same as on the photo of
the thin-section (Fig. 2). From Renberg (1981).
(e) Thiogenic varves. Satake & Saijo (1978) have described varves in
a strongly acid crater lake in Japan. A varve consists of alternating
whitish-yellow and dark-brown layers. The whitish-yellow layers are
formed by deposition of sulphur particles at the end of summer and
at the end of winter. The dark-brown layers are formed by growth of
a diatom species during the spring and autumn turnover periods.


Visual appearance

The colour of the most common varve type, the biogenic varves which
will be discussed further here, is to a large extent influenced by
iron. As mentioned in the previous chapter (Varve composition) compli-
cated alternations between dark and light laminations, caused by iron-
sulphide and ironhydroxide precipitation, are not unusual (Fig. 5).

The kind of lamination seen in Fig. 5 and other types of laminations,
can make it difficult to decide what is a true varve. When working
with varves and taking advantage of them in any stratigraphical study
it is of course necessary to know how the varves are built up and what
different layers represent.

The annual growth of a sediment, by varves, can clearly be seen in
Fig. 6.

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                                                                 83
Fig. 5. A photograph showing the topmost part of a varved sediment
from L. Hogbackstjarnen, N. Sweden. A very complex kind of lamination
has been created by ironsulphide and ironhydroxide colouring the sedi-
ment and by silt deposition.
Fig.  6. A  series of photographs  showing  the  surface  sediment with  the
frozen bottom water above  (from  Nylandssjon, N.  Sweden). Freeze  cores
were  taken in 1978, 1979,  1981 and  1982  and  these were photographed.
The annual growth by one varve is clearly discernible.

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                                                                 84
In cases where a complex lamination creates confusion about the varve
dating it is necessary to check the chronology in some way. Marker
layers, such as mineral layers caused by well-documented activities
in the watershed are one possibility. There are also a few, usually
very time-comsuming methods to study the microstratigraphy of diatoms,
Chrysophytes etc., which can be used to check the structure of the
varves (see "Varve composition").


Sampling and varve-counting

Freeze coring is required for soft surface sediments but consolidated
older sediments are easily taken without freeze technique, e.g. with
a large Russian peat corer.

The varve-counting can usually be made direct under a stereomicro-
scope. There are, however, several tricks to make the counting easier
(see Saarnisto 1979 and Renberg 1982).


Advantages

There are several advantages with varved lake sediments:

- a reliable chronology can be obtained simply by counting the varves.

- varves, or laminations, guarantee that no post-depositional mixing
  has taken place.  Hence, short-term changes in the environment can
  be traced.

- varves provide possibilities to do reliable investigations of the
  animal net accumulation rates of various sediment components.


Problems

For the acidification research the immediate benefit of varved lake
sediments may be hard to see, because varves are usually not found
in acidified lakes. They are more likely to be found in eutrophicated
lakes. However, indirectly varved sediments are of great importance,
e.g. for dating the fallout history of airborne pollutants such as
heavy metals, soot, etc.

However, in some of the strongly acidified lakes in S.  Sweden varves,
or at least laminations, can be found in the recent sediments. The
mechanisms involved in this process should be studied.

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                                                                 85
References
Battarbee, R.W. 1981. Diatom and chrysophyceae microstratigraphy of
   the annually laminated sediments of a small meromictic lake. -
   Striae 14, 105-109.

De Geer, G. 1940. Geochronologia Suecica Principles. - Kungl. Sv.
   Vetenskapsakademiens Handlingar 3:18:3, 1-367.

Kelts, K. & Hsu, K.J. 1978. Freshwater carbonate sedimentation. - In:
   Lerman, A. (ed.) Lakes: chemistry, geology, physics, 295-323.
   Springer Verlag, New York.

Ludlam, S.D. 1969. Fayetteville Green Lake, New York. 3. The lamina-
   ted sediments. - Limnol. Oceanogr. 14, 848-857.

Ludlam, S.D. 1979.Rhythmite deposition in lakes of the Northeastern
   United States. - In: Schliichter, Ch. (ed.) Moraines and varves -
   origin, genesis and classification, 287-294. Balkema, Rotterdam.

Nipkow, F. 1920. Vorlaufige Mitteilungen fiber Untersuchungen des
   Schlammabsatzes im Ziirichsee. - Z. Hiidrol. 1, 100-122.

O'Sullivan, P.E. 1983. Annually-laminated lake sediments and the
   study of Quaternary environmental changes - a review. - Quaternary
   Science Reviews 1, 245-313.

Renberg, I. 1981. Formation, structure and visual appearance of iron-
   rich, varved lake sediments. - Verb.. Internat. Verein. Limnol.
   21, 94-101.

Renberg, I. 1982. Varved lake sediments - geochronological records of
   the Holocene. - Geol. FSren. Stockh. Forhandl. 104, 275-279.

Saarnisto, M. 1979. Studies of annually laminated lake sediments.
   In: Berglund, B.(ed.) Palaeohydrological changes in the temperate
   zone in the last 15 000 years. IGCP 158 b. Lake and mire environ-
   ments. Project Guide 2. Specific methods, 61-77. Lund.

Satake, K. & Saijo, Y. 1978. Mechanism of lamination in bottom sedi-
   ment of the strongly acid lake Katanuma. - Arch. Hydrobiol. 83,
   429-442.

Simola, H. 1977. Diatom succession in the formation of annually-lami-
   nated sediments in Lovojarvi, a small eutrophicated lake. - Annales
   Botanici Fennici 14, 143-148.

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                                                                           86


                    The Interpretation of Metal Chemistry



                              Stephen A. Norton







     Some of the material  presented herein Is from the literature, some  Is



my own, and some Is from the work of graduate students at the University of



Maine.  The data Illustrate some points that we should keep in mind in



evaluating chemical data from sediment cores.  Figure I  from Nriagu and



Wong, (1983) shows arsenic profiles as a function of depth In a variety of



lakes.  The profiles describe exponential curves In all  cases except for



Kelley Lake.  If we Ignore the curve from Kelley for a moment, these



profiles look very much like     Pb profiles in "the ideal lake".  If



one had a lake with a zero sedimentation rate, and bioturbation decreased



with depth, and there was an instantaneous deposition of any pollutant such



as selenium, lead, or zinc, the pollutant would be exponentially dispersed


                                    210
as shown in Figure I  along with the     Pb due to nothing but



bioturbation.  The picture that we see would be an artifact of bioturbation



and not a historical  development of chemical  profiles.  Thus, bioturbation



is very important.  We must always keep  it in mind In interpreting data



from cores.



     The chemistry of sediments is controlled by a variety of things



Including autochthonous and allochthonous inputs. Including atmospheric



Inputs.  These may be organic or Inorganic.   These sediments may then be



modified by bioturbation and/or dI agenesis.   The simplest trend to be



interpreted in sediment chemistry is a change in concentration for a



constituent, for example,  enrichment of surface sediment concentration over



background.  Figure 2 displays data from a sediment core from Blavatn, a



lake  in Norway.  On the right,  displayed as  a function of depth, is the


                                          210
iron oxide content of that sediment.  The    -Pb profile (not shown)

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                                                                           87



Indicates that a hundred years before the present is approximately at a



depth of 5 cm.  This is a lake with a slow sedimentation rate.  We see



measurable    Cs well down in the sediment.  The iron profile has very



high background concentrations, on the order of 25 or 30 weight percent of



the ignited sediment.  A spike of iron making up greater than half of the



sediment is present.  This spike is diagenetic in all probability,



corresponding to a period when reduced dissolved iron was diffusing up



through the sediment and precipitated at the transition from reducing to



oxidizing conditions.  Also,  iron hydroxide may sediment through the water



column, accumulating and becoming what Is commonly called an iron crust.



Because the variable of Figure 2 Is in concentration units, the components



are not all independent; the forcing variable In this case is iron Inasmuch



as it is so abundant in the sediment.  At about 5 cm this prominent Iron



concentration spike causes little dips in all the other major elements.   If



one did not have total  chemistry of this sediment one would attempt to



Interpret the decline in the titanium, magnesium, or even zinc or copper



and one could be completely wrong.  One must have complete knowledge of the



sediment to interpret.  In a reasonable way, concentration profiles (or make



even more sophisticated interpretations involving deposition rates).



     Other modifications of the sediment or things to be wary of are shown



on Figure 3 showing data from a core from Dream Lake In northern New



Hampshire.  The Invariant chemistry for the major elements suggests steady



state conditions.   Note that the vertical  scale Is not depth but


                                            210
chronologic age, based  on the CRS model for    Pb.  Up core, there Is a



prominent  increase In total stable lead, a prominent increase and then



perhaps a decrease in zinc, a very broad general Increase in copper, a



slight decrease in magnesium, and a prominent decrease in calcium.  We've



observed a number of cores from oligotrophic clear water acidified lakes,

-------
                                                                          88




which commonly have a sharp decline in zinc concentration toward the



surface sediments.  In circumneutral lakes zinc tends to increase to the



surface.  We and many other workers (Renberg, Tolonen, Dillon, and others)



have suggested that the decline is caused by leaching of the zinc, either



In situ (microcosm studies suggest that this Is certainly possible), or



leaching of zinc from the detritus prior to its being deposited at the



bottom of the lake (either in the lake water column or when the detritus



was on the terrestrial landscape).  An alternative interpretation Is that



these zinc peaks may be a diagenetic phenomenon rather than a straight



forward depositional process (see Carignan, this workshop).  Many cores



from these acidified  lakes have a sharp decline In calcium in recent



sediment.  We also attribute that decline to acidification of the overlying



waters and leaching of the sediment In situ or leaching of the calcium in



the detritus prior to deposition.   Clearly, bulk chemistry is controlled by



processes not just In the water column but also occurring after deposition



(see Holdren, this workshop).  Interpreting the chemistry must take Into



consideration these diagenetic processes.



     Data in the literature for sediment cores may be as simple as undated



core depth versus concentration for various constituents.  Figure 4 shows



an enrichment in certain elements relative to other elements.  However, we



must always be cautious in interpreting the increase.  It may be due to a



decrease in some other component.    In the case of increasing concentrations



of trace elements such as Pb, an increase of that magnitude (Figure 4) must



be independent.   One must also be very careful  in interpreting trace heavy



metal data in comparison to major metal chemistry if the data have been



gathered by two different analytical techniques.  For example, the data on



the upper set of curves were obtained by analysis of solutions from a



sediment extraction; the lower curves are based on analysis of solutions

-------
                                                                           89
from total digestion.  Thus the curves compare "apples and oranges".  The
authors (Farmer et al., I960) clearly state this but frequently one finds
comparisons between data sets where analytical techniques are not
comparable.  We're really measuring one speciation compartment of the
metals for the former case.  We must worry about methodologies (see
Campbell  and Tessier, this workshop) as well as the chronologies.
     Figure 5 shows data from sediment element speciation studies from two
acidic lakes in Norway.  Both lakes have been acidified, at least as
Indicated  by the loss of fisheries.  We see an increase in total zinc and
then a decline in recent sediment for Hovvatn, a decline in several
sediment "compartments".  By looking at bulk chemistry we get one
Interpretation; by looking at the speciation (see Campbell and Tessier,
this workshop) we get a much more sophisticated story about where the
available zinc is and how it's leaving or entering the sediment.
     Figure 6 from Galloway and Likens (1979) shows enrichment type data
for various elements; unfortunately we have a situation of comparing apples
and oranges.  Four or five of these elements were anlyzed after one
extraction method and four or five were done by neutron activation; thus we
can't directly compare metal concentrations.  Additionally, one of the
major metals was not analyzed for.  The metals may be increasing partly due
to decreases In other constituents.  This Is true of major but not minor
elements.
     Figure 7 can be Interpreted as a case of relative enrichment of
aluminum  In surface sediments relative to the older sediments (with respect
to concentration) but one cannot say anything about absolute changes in
deposition rates.  Also, the reported concentrations are for ammonium
acetate extractable (pH = 4.0) cations, are reported on a percentage basis,
and could be (and should be) explained as a change in compartment

-------
                                                                           90



concentration.  This may be unrelated to total concentration.  Furthermore,



inasmuch as all the major elements have not been analyzed for, there may



not be an independent increase in concentration.



     In acidic rain studies we tend to concentrate on biologically



important elements, for example Hg.  Tolonen and Jaakkola (1983) present Hg



data (Figure 8) (influx and concentration) from Lake Sorvalampi.   If one



were to look only at that data one would be quite impressed with the fact



that, starting in about 1959, the concentration of Hg went up, the  influx



went up and clearly we have an environmental problem.  But if one  looks at



the rest of the influx date (as was done) one sees that many of the major



elements such as potassium, sodium, magnesium, aluminum, and titanium are



increasing suggesting that something is going on in the watershed, causing



an increased gross deposition rate.  The increase in Hg may not be a



straight forward atmospheric pollution story.



     The trace metal profiles from a core from Lake Hovvatn (Figure 9)



yield an unusual curve for lead,  certainly  increasing with time but with



some major peaks and valleys.  The Zn profile is even less decipherable.



The: interpretation rests on iron  which is forcing the rest of the



chemistry, in terms of concentration, to respond in this fashion.   If one



removes the iron from the sediment (mathematically) and recalculates



everything on a concentration basis, the lead profile has a normal



exponential increase in concentration.  The zinc increases and then sharply



decreases towards the surface and all of these minima in the calcium,



magnesium, manganese, ... concentrations disappear; it then resembles a



lake that has been more or less in steady state.  Reemphasizing, one must



look at a I I of the sediment, not just the element that you're interested in



for whatever specialized interest.



     The core from Jerseyfield Lake (Figure 10) in the Adirondacks has a

-------
                                                                           91
nearly exponential    Pb profile, with a few minor changes in an
exponential shape, and nearly steady state concentrations for many


elements.  A sharp decline in calcium is interpreted as due to lake


acidification (perhaps diagenetic leaching of calcium from the sediment due


to acidification of the overlying waters).  A fairly prominent iron-rich


crust at the surface comprises 20% of the sediment; this enrichment causes


a slight depression of the concentration of other constituents.  The


exponential increase in total lead and zinc concentrations in the profile


are typical for an acidic lake.   This core provided extremely good CRS


dating.  Thus we can calculate deposition rates.  The deposition rate for


titanium dioxide (Figure II), shows values slowly declining from 23 or 22

     2
ug/cm /y down to perhaps an average of 17 or 18 (25% decrease); around


1900 or 1910 there is a sharp increase in the deposition rate of TiO~


in the sediment at the coring site and then a decrease to the present.  In


1910 logging in the watershed was initiated.  It seems consistent that the


logging might be linked with increased terrestrial erosion and deposition


in the lake.  The importance of the analysis of deposition rates is that


knowing that TiO~ loading to the sediment is increasing, all  inorganic


constituents will increase, not necessarily in the same proportion but in


some (hopefully) related manner.  And If TIO. is increasing or


decreasing, the flux of indigenous Pb, In, Cu, Cd, Hg, Se, etc. must also


vary In parallel.  However, these elements are also commonly associated


with atmospheric deposition from polluted air masses.  We would like to


know what the gross sedimentation rate Is doing so that we can correct the


total Pb or Zn sediment deposition rates for the indigenous material and


derive a loading rate for .material derived from the atmosphere.  Using the


CRS dating for the Jerseyfleld core we derive total stable Pb loading rates


shown In Figure 12.  The values are remarkably stable prior to 1850.

-------
                                                                           92



Around 1850 to 1875, depending upon the accuracy of the dating, there is a



marked increase from about O.I micrograms per square centimeter per year to



about 3.5, and then a decline.  The Ti02 increased and so part of the



Pb increase is related to TiCL.  We can factor out the part of the



Increase that Is due to Increased erosion and deposition of inorganic



material  from the watershed.  About 95% of this profile is dominated by



anthropogenic and atmospheric Pb.  The decline in Pb in recent sediment is



common to almost all cores that we've looked at.  It seems to be ubiquitous



across the northeast, possibly reflecting a decline in Pb deposition to the



watersheds; this Is reflected in aerosol measurements as well.  The Fe for



Jerseyfield (Figure 13) is fairly constant, paralleling TiO~.   In



recent sediment there is a sharp Increase, which is ephemeral; the



iron-rich crust will migrate upward with the sediment-water interface,



dissolving at its underside and precipitating on the top—a diagenetic



process.



     When we see a sediment core that has more or less invariant chemistry



one feels that there is a good case for steady state and we can start



looking at other factors.  Figure 14 shows data from a core from Fish River


                             210
lake in northern Maine.  The    Pb profile has a flat section  in the



profile.   This can be interpreted in one of two ways:  either  turbation or


                                                            210
increased sedimentation, diluting the atmospheric signal  of    Pb.  We



chose the latter in our interpretation and developed a CRS chronology for



this core.  The CaO deposition rate is shown on Figure 15.  Fish River Lake



is non-acidic, and thus calcium would be fairly conservative in the



sediment with respect to diagenesis.  Calcium deposition rates on the order



of 150 micrograms per square centimeter per year are fairly constant until



1950.  After I950+, the CaO deposition rate increases dramatically (as does



the rate for TiO,, and everything else).  But the chemistry of  the

-------
                                                                           93

sediment did not change.  We interpret this core, and there may be many


lake cores like it, to indicate that there is a lot of resuspension and


deposition of much sediment of the same composition or erosion and


deposition of much soil with essentially the same composition as the


sediment that had previously been deposited.  The deposition rates go up,


but the chemistry of the sediment did not change.  The reason we think


we're correct in interpreting this as due to a greater in lux of sediment


rather than turbation  is the interpretation of the total  Pb profile (Figure

                                               2
16).  Background deposition rates of 0.75^ug/cm /y (which is fairly


high) exist because the area is a mineralized zone in the state of Maine.


The values for sediment loading of Pb from the atmosphere in Maine

                                       2
typically range between 2 and S.Sirg/cm /y.  The high Pb deposition
rate can be explained by a tripling of drainage basin inputs.  Figure 17


compares the deposition rates by taking the ratio of total Pb to TiCL.


We've normalized an element that's dominated by atmospheric  input to a


major rock forming element.  We still get the same type of exponential


picture of Increasing Pb deposition rate relative to TiO,,.   In this


particular lake ( Jerseyf ield) about half of the ratio rate increase from


0.005 to 0.01 would be due to increasing deposition of TiCk.   The best


representation is the atmospheric flux, which Is derived by correcting the


total flux.  We can perhaps use some of these metal deposition rates as a


surrogate for sulfate loading trends.


     Figure  18 shows data from Lake Husted In the Rocky Mountains, a  lake


we thought would be pristine.  Not so.  There is regional lead pollution in


that part of Colorado, starting about 1850 and apparently related to the


mineral industry.  Other elements associated with fossil fuel burning


(e.g., Zn) are not elevated in concentration.  Measurement of only one


heavy metal  (Pb) could have led to an Incorrect conclusion.  The moral of

-------
                                                                           94
the story is:  for good interpretation of trace metal data, one must have



good chronology and thorough chemical characterization of the sediment.








                              References Cited



Farmer, J.G., Swan, D.S., and Baxter, M.S., I960. Records and sources of



     metal pollutants in a dated Loch Lomond sediment core:  Science Tot.



     Environ., I6P 131-147.



Fritz, S.C. and Carlson, R.E., 1982, Stratigraphic diatom and chemical



     evidence for acid strip-mine lake recovery:  Water, Air, Soil Poll.,



     17.  151-163.



Galloway, J.N. and Likens, G.E., 1979, Atmospheric enhancement of metal



     deposition in Adirondack lake sediment:  Limnol. Oceanogr., 24f



     427-433.



Hansen, D.W. and Norton, S.A., 1982, Spatial and temporal trends  in the



     chemistry of atmospheric deposition in New England:   Intern. Symp.



     Hydromet., Am. Water Resour. Assoc., p. 25-33.



KahI, J.S., Norton, S.A., and Williams, J.S., 1984, Chronology, magnitude  •



     and paleolimnological record of changing metal fluxes related to



     atmospheric deposition of acids and metals in New England, in Teasleyf



     J.I., Ed., Geologic Aspects of Acid Deposition:  Ann Arbor Science



     Pub., 23-35.



Norton, S.A.,  1985, The sedimentary record of atmospheric pollution in



     Jerseyfield Lake, Adirondack Mountains, New York, in Adams, D.D. and



     Page, W., eds.,  Acid Deposition - Environmental, Economic, and Policy



     Issues:  Plenum Pub.

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                                                                           95
Norton, S.A. and Hess, C.T.,  1980, Atmospheric deposition  in Norway during



     the last 300 years as recorded  in SNSF  lake sediments.   I.  Sediment



     dating and chemical stratigraphy, in Drablos, D. and Tollan, A., eds.,



     Ecol.  Impact of Acid Preclp., SNSF, Sandefjord, Norway, 268-269.



Norton, S.A., Hess, C.T., and Davis, R.B., I960, Atmospheric deposition  in



     Norway during the  last 300 years recorded in SNSF  lake sediment:   I.



     Sediment dating and chemical stratigraphy:  Proc.  Int. Corif. Ecol.



     Impact of Acid Precip.,  SNSF, Sandefjord, Norway,  p. 268-269.



Nriagu, J.O., 1983, Arsenic enrichment in lakes near the smelters at



     Sudbury, Ontario:  Geochim. Cosmoch. Acta, 47r  1523-1526.



Reuther, R., Wright, R.F., and Forstner, U.,  1981, Distribution and



     chemical forms of heavy  metals  in sediment cores from two Norwegian



     lakes affected by acid precipitation:   Intern. Conf. Heavy Metals



     Envir.:  CEP Consultants, 318-321.



Tolonen, K. and Jaakkola, T., 1983,  History of lake acidification and air



     pollusion studied on sediments  in South  Finland:   Ann. Bot. Fennici,



     20r 57-78.

-------
                                                                                        96
              ARSEMC CONCENTRATION 

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        FIG. I. Arsenic profiles in sediments of representative lakes around the smelters at Sudbury, Ontario.

                                                     from  Nriagu,  1983
CS137
H20
ORG
                                       BLflVRTN
FEO
                                                        MNO
                                                       P8
                                                       ZN
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                   PCT.IG».          PCI.ICH.         PCT.ICM.          PCT.ICK.
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                                       Figure 2
                                             from Norton  and Hess, 1980

-------
                                                                        97
    H20
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   per. ION.
                                                                       mi IOL
                  Concentration versus  age (translated from depth)
                                  Figure 3
                                              Modified from Kahl et al.,  1984

-------


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%
•
; i
30 1.0 2.0

•
•

-" Cd

H9*l
•
'•

) 10 20
1
•"
,
-

s,
%
•
; i
25 50
* • •
/


Cu

P4/9



10 20
f !•
-.
•
^9

-* Pb-210
dpm/g
f
' [
25 50




Cr

XS/'l

•;

"* 50 1C
I •
*

-

- Ci-137
dpm/9
.



E
c
V
E
J
c

X
a
a

0

I
c
tl
•6
c
•x
a
b
a
                                                                                       98
   4  The "concunirulion/doplh ii\ srdirm-iu" profiles of lead, /.inc. coppi-r, cliromium
and manganese ((MI^COi II/NI1< OH • I Id  fraction) and of lulal .ir.sonic, cad mm in, irun,
aluminium, silicon, I cad-'J10 and cacsiunvi:i7  in  Loch  Lomond st-dimml con- I.LKI'M
1 (sue  lext).

                               from  Farmer et al.,  1980
Hovvatn
                                           Langtjern
                                                    from  Reuter  et  al., 1981

-------
                                                                               99
         AO
                                                           Cd
0  1   J  J   «   i   *      012345*     0   1   2   3  4  S  6
5
V
«
20
25
30
35
(
0
S
«
IS
20
25
30
35
4O
(
0
S
n
u
20
25
30
35
40
Figure
; .
. •
. .
. .
. -
. .

Cr
> • a « 24 30 :
•
• 1
.
.
•
.
•
Sb
> .5 1 is 2 2i :


K
r*
• «


O Element concentrati<
0
5
«
«
20
25
30
35
•
0
3
e
8
12
«
•
21
24
C
0
5
«
e
20
25
X
35
40
m vs. de]
•
•
.
• •
• -
• •
>•
•
Cu
9 « 12 • 24 30 !
.
.
*
. .
•
. .
'
V
10 3D 30 4O SO •


-
.
-
•
-
)th (cm) in Woodhull Lake
0
3
a
•
e
e
«
21
B
0
5
O
B
2O
25
JO
35
40
D 0
0
3
•
8
e
«
«
21
24
sediment
.
.
*
.
*
. .
'•
Pb
1 40 80 00 KO BO 30
•
.
•
•
•
•
•
•
Zn
75 OO 225 300 375 4M
•
.


*
•
•
. All concentration values i
 '1 dry wt except for An. which i.s
                               From  Galloway and Likens, 1979

-------
                                                                                             100
             E
             o
        Figure  7 P*P»h profile* of A!. Ft, M«. and Ca concentration! in the ndnncnL Concentration* are expremd

                                          M mg gnt~' sediment



                                                    from  Fritz and  Carlson,  1982
                                    SORVALAMPI
                                3O
 SORVALAMPI

- "P
                                                                             11
         5




        W>




        15-




       20




       25




       30^
                    V   . «  so 
-------
                                                                                     101
                                                                             ZN
                                 C8NC. VS. DEPTH (CHI





Fi9ure 9    chemu*!prof*f<»mamma*,fio^utoHo***,4.j>.     from  Norton and  Hess, 1980
                                                frOTT)
          H20
ORG
PBS 10
TI02
RL203
                                     to-




                                     30-




                                     HO-
          NR20
          fCT.IH.
      700    0  	   1000




        CONC.  VS. DEPTH  (CM)
                                                                        m.
                                                               from  Norton. 1985
     Figure 10: Sediment  chemistry from a core  from Jerseyfield Lake, NY.

-------
                                                                102
     2000    1900     1800    1700    1600    1SOO
    35 I ••••' •••''••••'	'	'	' " • • | 35
    30 -
"   as-
\n
o
Q-
UJ
O

    20 -
    IS
                                  TI02


                        JERSEYFIELD
                                            30
                   ras           Figure  11


                          from  Norton,  1985
                                            is
     2000    1900    1800    1700    1600    1500

                   CflLENOflfl TEflfl
     2000    1900    1800     1700    1600    1SOO
   ij.O J .... i .... I	I.,..i....I	' • •• -I U.O
   3.5 -
   1.0 -
   1.0 •
   0.5 -
   0.0
          PB


JERSEYFIELD
                                            3.5
                                            3.0
                                           -2.5
                                                       Figure  12
                                           •2-°   from  Norton,  1985
                                           • i.o
                                           •o.s
                                            0.0
     2000    1900     1800    1700    1600    1500

                   CALENDAR TEAR

-------
                                                                         103
      2000    1300    1800    1700    1600    1500
    900 J "••'••••'•"•'••••'" "'""'""'	'•" 'fc 900
    BOO -
    700 -
    600 -
 •-  500 -
 n  100 -
   300 -
   200 -
    100
                      FEO

            JERSEYFELD
                                           -aao
                                           -700
                                          C-600
                                           500
                               100
                                           300
                                           200
                                           100
                                                         Figure 13

                                                         from Norton, 1985
     2000   1900    1SOO     1700    1600    1SOO
H20
   FISH RIVER  LflKE.  55'
PB210         ORC          FEO
                                                    UNO
                  K)    0.0 	 ._.  Z.O    0.0 	 ._.  1.0    0.0
                                                                Figure  14
                                                                from Hanson and
                                                                Norton,  1982
                    CONC.  VS.  DEPTH  (CHI

-------
      2000     1940     1880     1820     1760     1700
    325 JIM iin. •!• mi ••••!•. MI	'"--I	1325
                                                                       104
K
>-
o
o
=5
a:
a:
•x,
o
a.
UJ
o
    300 -
    275 -
250 -
    225 -
    200 -
    175 •
    ISO -
    125 -
    100
                                       CflG
                          FISH RIVER LAKE
  •300
                                                  ^275
                                                      -250
                                                   -225
                                                   •200
                                                   -175
                                                   -150
                                                   -125
           Figure 15


           from Norton,


           unpub.
                                                    100
      2000      1940      1880     1820

                        CflLENOHR YEflR
                                       1760
1700
         3.50
            2000
  3.25 -




  3.00 -




  2.75 -

c


;j 2.50 -

CJ


S 2.25-




£ 2.00 -

c



I I'75 '



8 i.so-
a.
UJ
a

  1.25 -




  1.00 -




  0. 75 -
                   19DO    1980    1820     1780
         0.50
            2000
                                        PB
                        FISH RIVER LAKE
                   '.940    I860    1620

                          CfiLENOBK TfflR
                                        1760
                                            1700

                                              •3.50
                                             -3.25




                                             -3.00




                                             -2.75




                                             -2.SO




                                             -2.25




                                             -2.00




                                             -1.75




                                             -1.50




                                             -1.25




                                              !?00




                                              0. 75
                                                  0.50
                                               1700
     Figure 16


     from  Hanson and


     Norton,  1982

-------
                                                                   105
0.14
0.19
0.12
u 0.11

-------
                                                                                106
           Dynamics of Part IcuI ate Metals In Lakes of Northern Ontario








                                  Jerome Nrlagu








     We assume that the metal from the atmosphere somehow gets Into the



sediment*  So far nobody has tried to look at the mechanism of how It moves from



the top of the water column to the bottom of the water column - In other words,



the transfer of pollutant metals from the air down to the sediment.  There



haven't been any systematic  Investigations of this problem.  This paper deals



with the transfer of metals  from the atmosphere to the sediment and also



considers the subsequent release of the metals from the sediment to the water



column.



     For our study we used lakes located near the smelters at Sudbury, Ontario



for the simple reason that metal concentrations are unusually high in the



samples (Table I) and thus easy to measure well.  They are so high that you have



to dilute the samples to do your analyses.  Notice that Silver Lake has a pH of



about 3.9, and extremely high metal concentrations (Table 1).  By studying such



lakes we avoided the question of sample contamination during handling and



analyses.  Around Sudbury, we know where the metals come from (Table 2).  The



data are for emissions from the smelters between 1973 and 1981.  The release of



S0? Is a big one.  We all know about It—the single largest source of this



pollutant  In North America.  The smelters emit a lot of iron as well.  The point



I  want to emphasize  is the ratio at which these pollutants are emitted, because



we are going to  look at the  same ratios  in the water column and then down into



the sediments.  Arsenic has  not really been receiving any attention whatsoever.

-------
                                                                                107
Clearly, large quantities of As are being broadcast around the ecosystems around



Sudbury.  For people who are Interested in toxicology it may be noted that the



populations around base metal smelters usually have a high Incidence of cancer



which has usually been attributed to arsenic.



     Selenium is another element that Is being overlooked and that, I feel, is



very unfortunate (Table 3).  About 50 tons or so of Se have been dispersed via



the atmosphere.  Note that about 630 tonnes of the Se are wasted in the



environment with the slags and tailings.  The disposal of such wastes can create



severe Se pollution problems on a local scale.



     The Se profiles In lake sediments In the Sudbury basin are depicted In



Figure  I.  The point at which Increased sedimentation of Se began  Is very sharp.



It  is sharper than you find  In the Algonquin Park or possibly in the Adirondack



Mountains.  The rate of Se accumulation is extremely high.  Windy  Lake  is



Interesting because the Se increase began around 1945 or so when they installed



a 500 foot smelter stack in Sudbury.  Kelley Lake is used as a sewage pond.



That Is why -the Se profiles  in  Its sediments are unusual.



     We've selected our lakes on the basis of the morphology of the bottom.



We've looked at lakes with fairly flat bottoms and few  large sedimentation



basins.  We took the sample almost at the middle of each basin.  If you were to



go to the margins of the basin you would likely get different flux rates but we



are  looking for the average value.  We assume that these are average deposition



rates and flux rates for the metals (Table 4).  Note that the nickel levels are



extremely high; they are among the highest recorded anywhere in Canada that I



know of.  In view of the high metal concentrations, the  lakes represent a good



"laboratory" for studying the fate and behavior of pollutant metals  In the



environment.



     With the sources of the metals established, we proceeded to look at the

-------
                                                                                108
speclatlon of the metals In the water column Itself.  In what forms do you have



the metals In some of these highly contaminated lake waters?  We started out



with the simple Phreque Model, one of these super duper computer programs that



you get from USGS.  We've adopted It and simply fed the composition of the lake



water Into the computer program, and asked It to determine the species present.



Nickel wl'll,  according to the computer model, occur dominant I y In the divalent



form; the nickel sulfate complex has become quite Important because of the high



sulfate concentrations In the water column.  On the other hand, copper, If you



have any humlc acid present,  Is tied up mostly as copper humates.  You also have



divalent copper and copper sulfate.  What happens If you have a lot of suspended



matter or what  is the association of metals with partlculates  In the water



column?  We tried to model that.  We tused Hem's adsorption model  for lead.  We



altered it and utilized the Phraque speclatlon program.  That way we get the



species present while a sub-routine produces the amount of adsorption and the



percentage of species that are adsorbed.  Below a pH of about 5.5, according to



our calculation, very little of the metal In solution will be adsorbed by the



suspended particulates.  From this point on, adsorption decreases quite



dramatically.  Many Investigators have found the same thing.  Whenever you talk



about adsorption of metals by partlculates It must be concerned with the pH.



Below a pH of 6, the adsorption  Is quite low.  In the literature all adsorption



calculations assume that the metal  Is  In the divalent ionic form.  Few people



have considered the adsorption of complexed species onto particulate material.



When we ran the computer program, we found a discrepancy between the divalent



copper and total copper.  This was attributed to the adsorptin of complexed



species.  What  species are being complexed to make up the difference?  If you



simply run your model as  if all the metal Is in the divalent form, the print out



(for Pb) will look  like Figure 2.   If  you assume that the PbOH Is being

-------
                                                                                109
adsorbed, what you see Is quite different.  That's one point that has been



missing  In the literature up until now, the adsorption of complexed species by



suspended partlculates.



     Let's look at suspended partlculates In detail because we are blaming them



for playing an Important role In the cycling of metals In the water column.  To



do that, we designed a fairly simply sedimentation trap or particle interceptor



(Figure 3).  They're light weight and you can set them up In the field.  They



weigh about 20 pounds or so.  You have two moorings, and the sediment traps.



Usually we have three traps per station which are attached to a sub-surface



float and a marker on top.  The sub-surface floats are Important because the



lake Is heavily used by recreation Ists and the pranksters would pull your traps



up If you had a suface float.   In each trap we put a tablet or mercuric Iodide.



Each tablet weighs 0.25 grams.  The tablet is enclosed In plastic with a pin



hole In  It.  This enables the slow diffusion of mercuric Iodide into the trap.



This reduces the biodegradation In the trap.  We have found some large organisms



which went In there to eat the trapped material and they were dead!  We did not



Include the dead organisms  in the analysis.



     In addition to the traps, we use a flow through centrifuge to get at what



we call suspended partlculates  (the trap will give us the settling



partlculates).  That gives us the concentration of part IcuI ate matter  In a given



volume of.water at the time of sampling.  There Is a big difference between



suspended and settling particulates.  First of all, the suspended particulates



contain considerably more organic matter than you will find In the settling



partlculates.  You can speculate on why that is so.   It's true in all of the



lakes.  The C to N ratio on the other hand Is almost the same.  In the



sediments, on the other hand, the C to N ratio In the surficlal sedimetns  (0-1



centimeter) Is much smaller than  In the suspended partlculates (Table 5).   If we

-------
                                                                                no
compare the ratios and assume that It Is material that has been blodegraded from



the water column, we find that 50-70$ of the blomass In the water column  Is



blodegraded before It gets burled In the sediment.  This Is much lower than we



find In the Great Lakes or that people find In lakes with much less heavy metal



pollution.  As we showed In most of the lakes (Table 6) these suspended



particulates are so heavily laden with toxic metals that they make a very toxic



diet to any consumer, therefore we are not surprised that the degradation  rate



is lower.  Let's look at the Cu concentrations In the traps and suspended



material and In the sediment (Table 6).  The suspended particulates usually



contain a  little more Cu than the sediment.  The ratio of the metals In the



suspended particulates to the sediment Is 2 to 3 or even as high as 4.  What



that means  Is that we're losing metals In the sediments or that blodegradatlon



in the water column  Is enriching the metals In suspended material.  Let's  look



at the flux rates (Table 7).  Remember that the suspended material has higher



metal concentrations than the sediment (remember that we are still talking about



lakes near Sudbury).  It may be entirely different  In other areas.  Here  Is what



you get for the particulate flux  In the water column using the sediment traps.



Clearly we find seasonal changes  (Table 8).  For example. In July and August we



have the highest flux.   In May and June and again  in September, when you  have



overturn, we find considerably less seston  In the water column going down.   If



you  look at the 3 meter samples, the flux  In the hypollmnlon Is considerably



higher than that In the epI limn Ion for the seston as well as the metals.   If you



take a close look at a I I of the fluxes In the water column and sediment,  what



you get  fs really outstanding (Figure 4).  You get  a logarithmic Increase In the



flux near the sediment water Interface.  You find exactly the same thing  In



small  lakes.  What this means is that there Is a  lot of resuspenslon of sediment



going on.   If you take a sediment accumulation rate from  lead 210 dating  and

-------
                                                                                Ill
compare that with what you get in the sediment traps, the net sedimentation rate



is only 5-20$ of the sedimentation rate based on the trap studies.  The



residence time for a particle at the sediment water  interface is extremely



short.  The particle simply passes up and down and up and down.  This has been



observed in many lakes.  Even in the oceans as well.  Look at the differences in



the resuspension rate; as you get to the deepest part of Lake Ontario, the



resuspension decreases (Figure 4).  The  increase towards shallow water Is almost



an order of magnitude higher.  We will compare the flux rates we get  In the



epI limn Ion and hypollmnlon and sediments.  The flux  rates in the hypollmnion are



much greater than in the epllimnlon.  On the other hand the sedimentation rates



one gets In the epllimnlon are similar to what one gets  in the sediment.  The



value  In the epllimnlon may be as much as 1.5 times  the sediment value.  This



value  is for the summer when phytoplankton production Is highest.  The values



may be more nearly equal during the winter.  There  is a close linkage between



the organic flux from the production of organic matter and the cycling of trace



metals.  We have mostly focused on heavily contaminated sites.



     We decided to  look at three other sites.  One  Is the Algonquin Provincial



Park which Is near Dorset, the second locality Is the east coast of Nova Scotia,



the third area  is the Turkey Lakes watershed  In the  northwestern part of



Ontario.  Here are some preliminary data from the Algonquin Park.  The metal



profiles In the sediments are very similar to what  is found  In the Adlrondacks.



In all cases you see an Increase  In sedimentary metal burden towards the



sediment-water  Interface.   If you use the sediment deposition rate, the rates of



metal  accumulation  in the sediment (Table 9) are closer to those observed by



Norton  In New England and others  In the Adlrondacks.  Therefore,  I conclude that



the flux of toxic metals  Into sediments  In the Algonquin Provincial park are



comparable to those observed  In sediments  in the Adlrondacks.  We don't know

-------
                                                                                112
where the zinc (Figure 5)  is coming from.   We find  exceedingly high zinc values



in the Algonquin Park lake sediments.   I  don't know If this Is unique to this



area because of bedrock chemistry.

-------
                                                                      113
Table I.  Total Metal Concentrations fn Lake Waters.
Lake
Silver
Middle
Lohl
Ramsay
McFar 1 ane
Wavey
Kelly
Vermll 1 Ion
Concentrat I on ( ug/ 1 )
NI Cu Zn
510
330
220
220
120
94
92
80
110
36
61
16
10
27
18
8
100
28
26
9.0
II
21
4.3
3.0

-------
                                                                      114
Table 2.  Source Parameters.





Smelter Emissions (tons/day)



         Nl                        2.6



         Cu                        2.6



         Pb                        0.6



         S02                       2500



Ratios of Metals Released (average)



         Fe/NI                     0.6-5  (2.8)



         Fe/Cu                     0.9-35 (2.5)



         Cu/Nl                     0.7-1.2 (1.0)



Airborne Metal Levels Around Sudbury (ug/m3)



         NI                        0.4-5



         Cu                        0.1-4



         Pb                        0.4-5



Metal Ratios  In the Aerosols



         Fe/NI                     14



         Fe/Cu                     3.2

-------
                                                                      115
Table 3.  Se Flux to Sediments
Lake
Richard
Verm Ml Ion
McFarlane
Lohl
Ne 1 son
Kelly
Hannak
Flux
mg/m2/y
0.25
0.40
0.49
I.I
0.96
12.4
I.I
Enrich. Factor
3.4
2.8
3.4
18
13
—
13

-------
                                                                      116
Table 4.  Present-day Rates of Metal Deposition In Sudbury
          Area Lake Sediments.
Lake
Kelley
Ramsey
Vermi 1 1 Ion
McFar 1 ane
Richard
Lohi
Windy
Ne 1 son
Wavy
NI
595
386(38)
298(12)
115(18)
112(28)
108(44)
26(2.5)
13(113)
0(1.0)
2Cu
mg/nr/y
258
301(36)
60(10)
75(31)
52(22)
87(43)
2.6(1.1)
1.9(77)
0(1.0)
Pb
9.8
27(5.9)
20(2.2)
10(3.2)
5.2(4.2)
6.8(9.3)
40(3.8)
23
0(1.0)
Zn
38
48(2.6)
62(1.7)
32(1.8)
12(2.0)
17(2.5)
7.4(1.0)
27(7.3)
0(1.2)
(  ) Enrichment factors are shown In parentheses

-------
                                                                      117
Table 5.  Partleu I ate Organic Carbon and Nitrogen
Lake
McFar 1 ane
3m
15m
Ne 1 son
3m
20m
Wavy
3m
21m
Verm 1 1 1 (on
3m
6m
Windy
3m
20m
Suspended Part.
C($) C/N

28
14

26
22

29
23

22
16

26
19

8.8
8.0

5.6
7.5

7.7
9.2

7.3
7.5

7.2
8.3
Sett 1 Ing Part. Sediments
C($) C/N C(%) C/N

10
12

16
17

17
13

16
15

16
15
6.5
7.1
5.7
14
10
II
14
4.6
9.2
2.6
8.1
8.3
7.7
9.4
6.3
II


10


12


12


13



-------
                                                                       118
Table 6.  Metal Concentrations In Trapped and Suspended
          Material and In Sediments (ug/g).
Lake
McFar 1 ane
Susp.
Trap
Sed.
Wavy
Susp.
Trap
Sed.
VermM lion
Susp.
Trap
Sed.
Ne 1 son
Susp.
Trap
Sed.
Windy
Susp.
Trap
Sed.
Cu

237
483
470

630
195
220

256
177
140

~
146
2470

—
172
45
NI

2170
2210
735

624
112
— •

2580
989
700

368
158
2720

578
308
132
Zn

587
666
206

234
72
120

548
270
147

347
137
740

556
207
171
Pb

357
207
64

358
132
69

165
64
48

562
182
1160

490
166
54

-------
                                                                      119
Table 7.  Comparison of Part feu I ate Metal  Flux Rates
          (mg/m /y)
Lake & Sample
McFarlane
3m
15m
Sed.
Ne 1 son
3m
20m
Sed.
Wavy
3m
21m
Sed.
Verm III ton
3m
6m
Sed.
Windy
3m
20m
Sed.
Cu

37
88
—

4.4
15
0.5

10

3.8

27
44
16

6.6
21
0.7
Nl

185
678
31

4.6
16
3.6

6.3

3.8

149
256
82

10
45
7.1
Zn

50
137
8.8

8.2
10
7.4

4.1

2.1

53
56
17

10
31
2.0
Pb

12
43
2.7

9.9
14
6.3

7.4

0.8

12
12
5.5

6.6
17
II
. Cd

0.6
2.5
—

0.4
0.5
•—

0.2

—

0.4
0.6
—

0.3
0.8
—
Seston

1040
1490
440

450
750
370

510



2010
2040
1160

600
930
430

-------
                                                                      120
Table 8A.  Partlculate Metal  Flux Rates In  Windy Lake
           (mg/m /y)
Period
May/ June
3m
20m
June/Jul
3m
20m
Jul/Aug
3m
20m
Aug/Sept
3m
20m
Average
3m
20m
Cu

6.3

5.7
10
6.0
35
8.2
31
6.6
21
Nl

8.5

7.9
13
10
91
13
69
10
45
Zn

6.8

II
9.6
9.4
50
12
60
10
31
Pb

6.0

6.0
9.9
6.8
31

23
6.6
17
Cd

—

0.2
0.2
0.2
1.4
0.4
0.7
0.3
0.8
Seston

380

580
410
550
1690
680
1230
600
930

-------
                                                                      121
Table 8B.  Part Feu I ate Metal Flux Rates In McFarlane Lake
           (mg/m /y)
Period
May/ June
3m
15m
June/Jul
3m
15m
Jul/Aug
3m
15m
Aug/Sept
3m
20m
Average
3m
15m
Cu
46


47
81
28
105
28
79
37
88
Nl
125


226
302
154
794
234
937
185
678
Zn
64


74
82
34
200
28
128
50
137
Pb
12


17
19
29
—
8.8
71
12
43
Cd
0.6


1.0
1.4
0.5
3.8

2.3
0.6
2.5
Seston
1040


1620
1590
850
1640
660
1230
1040
1490

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                                                                                 122


Table 9.  Present-day rates of metal deposition In the Algonquin Lake sediments
Lake
LOUISA
PROULX
HOGAN
BASIN
BRULE
TIM
KIOSHKOKWI
THREE-MILE
Nl
0.65(1.3)
2.95(1.5)
1.79(1.7)
1.77(1.5)
1.77(2.0)
3.60(3.1)
1.72(1.2)
8.36(2.4)
Cu
0.70(1.0)
3.50(1.4)
2.22(1.5)
2.81(1.3)
2.08(1.5)
2.22(1.4)
1.91(1.2)
9.39(1.5)
Pb 2
(mg/m /y)
3.90(17)
11.9 (13)
10.0 (16)
14.8 (32)
25.7 (52)
14.3 (26)
3.7 ( 6)
43.5 (23)
Zn
5.0(1.7)
22.1(1.7)
8.6(1.5)
12.9(1.6)
14.0(2.7)
10.7(1.3)
9.5(1.3)
50.3(2.2)
Cd
0.07(2.0)
0.43(3.0)
0.16(2.2)
0.19(2.0)
0.25(3.4)
0.23(2.3)
0.13(1.8)
0.74(2.6)
ft
 1  The enrichment factors (In brackets) are defined as the ratio of metal
    content  In surface (0-1 cm) sediment to the average metal content  In
    pre-colonial sediments.

-------
                                       Selenium Concentration (tig g'1)
      KJ-
     20
     30
•±1   4O

                   -1880
                MacFarlane Lake
I
CO
€
     20-
     30-
     40-
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 3
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                Wavy Lake
                                                      -1880
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                                                    • Richard Lake
                                                                                     WHO
                                              50    100    ISO   200    250
                                                                                LohiLake
                                                                                           -1880
                                                                                      Hanrwh Laka
                                                                                                                                          ro

-------
      Figure 2
                                                  124
   50
   40-
   30-
Q
LU
O
Z
LU

8
CO
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20-
10-
O  o-
            McFARLANE  LAKE
         5.5
               6.0
 6.5
7.0
75
U_
O
   30-
                                             HCOt?
LU
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DC
LLJ 20-
Q_
   10-
        VERMILLION  LAKE
                   Pb (total)
        5.0
               5.5
 6.0

PH
6.5
7.0

-------
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-------
Figure 4
                                                                      126
10.0-
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-------
     Figure 5
                                         127
  o
    Zn, Pb, Ni  Concentrations (pg/g)
             80   120   i&o   200  240
  10.
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Lake  Opeongo
Ann i e Bay

-------
                                                                            128
              SITE-SPECIFIC VS. WHOLE-SYSTEM MEASUREMENTS
                      OP TRACE METALS IN SEDIMENTS
R.  DOUGLAS EVANS, ENVIRONMENTAL CENTRE, TRENT UNIVERSITY, PETERBOROUGH,
                  ONTARIO,  CANADA, K9J 7B8

PETER J.  DILLON,  DORSET RESEARCH CENTRE,  ONTARIO MINISTRY OF THE
                 ENVIRONMENT, DORSET,  ONTARIO, CANADA, KOB 1GO
     It is widely recognized by most workers who study lake sediments

that sediment cores exhibit profiles of changing metal concentrations

with depth into the sediments.  The emphasis of this paper is the

legitimate uses of these sediment profiles.  We will focus on two

particular types of studies: site-specific studies and  whole-system

studies.   Site-specific studies are those studies  in which one goes to

the center of the lake, takes a core,  and tries to produce some useful

information from that center-of-the-lake core.   Whole-system studies,  on

the other hand,  are a larger type of study where you try to produce a

single number which represents the entire system.



     Single core studies have been conducted in a wide variety of

locations, from the Pacific Ocean to the Great  Lakes,  in  numerous small

lakes and ponds, even the Palace Moat in Tokoyo.  There are several

types of questions which can be answered using a single core or site-

specific studies.   First, this type of study is very useful for

determining the time of onset of environmental changes.  Several workers

have measured changes in contaminant concentration with depth into a

-------
                                                                            129
sediment core.  They then use a dating technique in conjunction with the




contaminant profile, and from  these data, they are able to determine at




what time in  the past the environmental  change  began  (eg. Evans and




Dillon, 1982,Forstner and Wittmann, 1981).   Second, one can use these



centre of the  lake  profiles  to look at relative  diffences between




metals.  A good example of such a study  is one in which the zinc and




lead concentrations are examined.  If  they have  different atmospheric




sources or pathways, one might look at the different timing of onset of



anthropogenic  loading or at  relative differences in the the magnitude of




the metal contamination.  Thirdly, in selected situations, single




sediment cores can be used for testing of sedimentation models.








     There are several constraints which may limit the usefulness of



single core studies for even these few purposes.  Some of these are




sediment mixing, metal  mobility,  and  differential  binding of metals.




These topics have been discussed in detail by other participants in this



symposium and  we refer  the  reader to  those sections.  However it is




assumed, for example, that if bioturbation is very severe it will be




recognized and its  impacts on  the assigning of dates of events will be



dealt with accordingly.








     There are, however, some  things  that one cannot do with single




centre-of-the-lake  cores.  The  literature contains  many studies where




people try to  put such data  to an inappropriate  use .   A good  example is




the calculation of  atmospheric flux of a trace metal from a single  core.



One cannot calculate a valid estimate of atmospheric flux from a single

-------
                                                                            130
core or even from a very few cores within a lake without supplementary

data.  There are several studies which illustrate  this  point.  Edgington

and Bobbins (1976)  published a study showing lead profiles in four cores

from Lake Michigan.  From  those  cores they attempted  to produce a

historical record of lead deposition.  As suggested earlier, they
applied the lead-210 dating technique to the cores and  measured lead

concentrations in the cores.  In similar fashion, Evans and Dillon

(1982)  attempted to measure historical changes in lead  deposition into

Found Lake,  a small meromictic lake in southern  Ontario.  The advantage

of working in a meromictic lake  is that  you don't have  the mixing

problems which you get in dimictic lakes; hence the profiles exhibit no

mixed  layers (Fig.  1).   As  in the work of Edgington and Robbins,  lead-

210 dating was used to establish  a time frame for changes in the input

of lead.  In both studies,  one of the objectives  was to determine the

atmospheric flux of lead to the respective lakes.   Now as we have

already stated,  this is not possible using a single sediment core.  One

of the reasons  for this is  that sediments tend to focus to the centre of

the lake.   In figure 1,  the lead  concentration profiles for two cores

indicate surface concentrations of 300 and 600 ug/g dry weight.  If we

were to translate these values into  fluxes  to the sediment the result

also would be different by  about  two-fold.  Since there can be only one

value for the atmospheric  flux,  it  is impossible to decide between the

two cores.  In fact it is unlikely that either value is the true

atmospheric flux.  To translate the results into atmospheric flux we

need some measurements of  the whole system.

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                                                                            131
     There are a number of approaches  one  can  use  to  get  a  whole-system




measurement.  Edgington and Bobbins tried to do this by using the




historical record of lead emitted by automobile exhaust and coal



burning.  They  used this as a  source function which they integrated with




whole lake sediment accumulation.  Their whole lake accumulation data




was then derived  from  a relationship between total deposition of



sediments since last glaciation (mean Waukegan member) and a few point




measurements  of recent sedimentation.  By integrating sediment




accumulation with atmospheric lead emisions, they were able to formulate



a model  which simulated the  observed lead concentration profiles in



their sediment cores.  In our study (Evans and Dillon,  1982),  rather




than taking the approach of using a hypothetical function for



atmospheric emissions, we used the shape of the measured lead profiles




in the sediment core as the source function. The assumption which we




used was that in a meromictic lake the shape of the lead concentration




profile will  reflect in a relative sense the changes in atmospheric flux




through time.   To scale that  relative picture  of change through time to




the actual deposition, we used regional information on whole lake




deposition of lead from a series of lakes (Dillon and  Evans,  1982).




Hence we were able  to  produce a historical record of atmospheric lead




deposition through time (Fig. 2).  The two curves show  two  estimates of



the same function of atmospheric deposition.  One point which should be




made is that while this type  of analysis can be done using a single



core,  it is useful to check the validity of your historical rate of




change by using two or three cores. Each core  should  give you the same



result within  the limits  of  error  of the analyses.  Having derived a

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                                                                            132
function such as that shown in Fig. 2,  one can then apply it to mixed

cores from dimictic  lakes as a test of  its validity.  Without going into

the actual model used, Evans and Dillon (1982) showed that their

function was reasonable  for  the  Haliburton area of Ontario (Fig.  3).

While these two studies used somewhat different methods  to achieve a

similar result, the  important point is  that in both cases, atmospheric

flux was arrived at by incorporating a whole-system measurement into the

calculation and thereby eliminating the problem of differential rates of

sedimentation across the lake bottom.




     We referred to  the Palace Moat study earlier.  This study is a

useful example of the problem of trying to extract too  much information
                                               •
from one's work.  In this study  (Goldberg et  al.,  1976),  a single

sediment core was collected from the Palace Moat  in Tokyo, Japan.  Using

dating techniques in combination with changes in trace metal

concentrations, they were able to obtain information on the time of

onset of environmental change for  various metals.  They then attempted

to examine the relationship between atmospheric deposition, or their

perceived atmospheric deposition,  and the sediment  record.

Unfortunately,  this was not possible  because they  had no information on

sediment focussing in the moat.  It was not possible, on the basis of

their single core,  to determine  whether their core represented the

average for the moat, 10$ of the average, or two  times  the  average.

This is an example of an invalid application of a site-specific

study.

-------
                                                                            133




     Given the limited value of site-specific  studies, whole-system




measurements  take on an added  value.  There are several catagories of




questions which require whole-system measurements to obtain valid




answers;  for example, atmospheric flux calculations have been mentioned




previously.  One needs whole-system  measurements to compare trace metal




contamination betweeen lakes.  It is not valid to take a single core




from each of two lakes and to compare either the concentrations or flux



calculations from those two  lakes.  If inter-regional differences in



trace metal deposition are to be compared,  a single  number which



represents each lake in our comparison must be obtained.  Mass balance




studies, comparing inputs and outputs of trace metals, where sediments




form a  component of either the inputs or the outputs,  demand whole-




system  information.   There are several more examples but these are




sufficient to illustrate  the  point.








     Earlier,  we stated that a whole-system measurement is one which




allows us to represent the trace metal contamination within a lake by a




single number.  Thus far the only proven way of obtaining a single




number  for a lake is to intensively core the lake until  there is




sufficient information to numerically  represent spatial variation in the



system.  For practical reasons,  at least in our own  work,  so far this



has limited us to small systems, although  there are data which suggest




that whole-system information  can be obtained for large  systems as well.




In a lake of approximately 60 ha, such as  Red Chalk Lake shown in figure




4, we collect 30 or 40 cores.  We try to balance the coring locations as




a function of the morphometry.  Thus we collect more cores in the

-------
                                                                            134
shallow areas and less in the deep areas.  This simply reflects the




importance of various depth strata within  the  lake.








     If one examines the mass of lead in cores across the bottom of a




lake such as that shown in figure U, a pattern begins to emerge.  The




mass of lead at a given location in the lake is a function of the depth




of the lake at which  the  core  was collected (Fig.5).  There is also a




good correlation between bulk sediment accumulation and the mass of




contaminant.  Thus we get relationships such as that shown in figure  5,




where the mass of anthropogenic lead increases toward the center of the




lake.  On  the  basis  of 25-30  cores, we  can  produce a mathematical




relationship which describes the spatial variation in lead accumulation.




Using this relationship,  we can derive a single number  for the  lake.




There are a number of ways to do this,  but they all involve intergration




of the spatial variability data with the morphometry of the lake.  One




could use Theissen's  polygons,  a  spatial  mapping technique where each




core represents a specific area on the lake bottom.  Another possibility



is to derive a regression equation relating anthropogenic lead to lake



depth and then use the regression equation in conjunction with the




morphometric data.  Lastly,  one can take specific values for a




particular depth stratum.   For example, if several cores have been




collected from the 12-16 m stratum,  the average value of those cores




could be applied to the entire stratum. We have used all three of these




techniques on several lakes and have  found  that the  whole-system




estimates are very similar,  with variablility between methods of 5-10




percent (Evans and Rigler,  1984).  While  the  following examples use

-------
                                                                            135
anthropogenic lead, it should be possible for a wide variety of




parameters to produce a number  which  is  reasonable and represents a




lake.








     Figure 5 illustrates the relationship between lead mass and depth




for Red Chalk Lake, the same lake shown  in figure 4.  The same pattern



is seen in several different types of lakes.  In figure 6, the same data




are presented for Bob Lake,  a larger lake approximately  2.5 km sq. in




surface area.  In this lake  as well,  we  find a linear relationship



allowing the intergration to be quite simple.  Hope  Lake  (Fig.7) is a




small subarctic  lake near Shefferville,  Quebec. The mass of lead per



unit area is much lower than in the two  southern Ontario lakes (40-60




mg/m2 vs  1000-2000 mg/m2).   Despite the  low  levels  of lead, we still see



a trend toward linearity with depth.   The other important point




illustrated by figure 7 is that the strength of the relationship seems




to be related to  the maximum depth of the lake. The intensity of




sediment focussing  is probably  a function of the maximum depth.  Thus




Bob Lake with a 'maximum depth of 60 m had a very strong relationship




while in Hope Lake  (14 meters maximum depth) the relationship is much



weaker. Once the  lakes become very shallow (3-4 meters)  the mass of lead




becomes quite constant across the lake bottom and integration is simply



a matter of averaging the appropriate number of  cores.








     The other important aspect to representing a lake by a single



number is that we should have an estimate of the reproducibility of that



number. Given the coring intensity required,  there are not many

-------
                                                                            136




estimates of reproducibility.  We have,  however, undertaken replicate



sampling on one lake. In Red Chalk Lake,  we cored the lake in 1980 and




then again in 1982.   The,separate  sampling  schemes are shown in figure



4.   By  doing the  entire  project  twice,  we were able to look at the



ability to produce a single number which represents this  lake.  For the



two studies, the reproducibility or the variance was  about 5%.  There



was much higher variability if one compares data from any one location



in the lake.








     Data such as these can be used in many ways.  If we  are going to



compare metal contamination between lakes we need a number which



represents each individual lake.  In  table  1,  we have  compared the



average burden of lead,  zinc,  and  cadmium for each of eight lakes in the



Haliburton region of southern Ontario.  The values are the total



anthropogenic burden since onset of cultural activities.   For each lake



the data are derived from a sampling scheme much like that described



earlier using as many as 50 cores per lake.  One way to generate



information of this  nature without overtaxing  the analytical capacity of



the average research lab is to avoid  chemical analysis on individual



sections of the core and to integrate the sediment over the entire depth



in which you find the trace metal of concern.  This drastically reduces



the number of measurements required.








     Using the technique of integrated sampling and analysis, we have



been able to measure whole-system value for many lakes.  For those lakes



whose whole-system  measurements are  shown  in table 1, there is not a

-------
                                                                            137
great range of variation for any metal but especially  for lead.  The




average lead burden for this area  is  680  mg/m2 (Dillon and Evans,  1982).




This represents the integrated total  deposition of anthropogenic lead



since the onset of cultural activities (approximately  100 years




according to lead-210 dating).   These lakes are all within a radius of




about 30 kilometers, thus we can begin to get some idea of the magnitude




of regional variation in sediment  burden  for the  various metals.  For




zinc deposition the variation is highest, less so for cadmium, and least



for lead.








    We can expand this work to  a much larger area.   Evans and Rigler




(1984)  have measured  whole-system  anthropogenic lead in each of five



regions:  three in Ontario and two  in  Quebec; one  a sub-Arctic station




near Shefferville,  one much further south.  From this we can begin to




determine the  regional variation in lead  burdens  across  eastern  Canada.




The Haliburton area of Ontario has  the highest deposition (680 mg/m2)



while deposition falls off  in either  direction  (east or west).  The sub-




Arctic station has very low deposition, about one-tenth that of




Haliburton.   The eastward flow of  anthropogenic material appears to be




much stronger than the northward flow.  We are starting a program to



fill in the picture for northern sites which will help to determine




whether this hypothesis is  correct.








     While the most complete data  set available is for total




anthropogenic lead burden (Evans and  Rigler,1980;  Dillon and Evans,



1982; Evans and Rigler, 1984) the  techniques do not apply only to total

-------
                                                                            138
anthropogenic lead burdens.   Robbins (1980)  measured the current rate of



accumulation of anthropogenic lead in Lake Huron sediments.  This study



serves to illustrate two very important points.  The first is that it is



possible to determine whole-system parameters for short periods of time



(ie.  annual accumulation)  and the second  is  that  Lake Huron is a very
                                             X


large lake and thus, with enough effort,  it is possible to make whole-



system measurements on very large systems as well as small ones.







     The last example of the need for  whole-system measurements is in



the determination of trace metal mass balances within a lake.  If one is



attempting to quantify the inputs and losses of a trace metal within an



aquatic system,  the sediments are a large  component.  In figure 8 we



present data for copper concentration in  five sediment cores  from



Clearwater Lake (Dillon et al.,  1982).  The  shape of the concentration



profile is a function of the core location.   The  two cores with the



highest concentrations are from  deep water sites,  the two cores with the



least concentrations are from shallow water  sights.  The differences in



the copper profiles indicate first  that different mechanisms  are at work



in the shallow regions than in the deeper areas and second that a



calculation of the sediment component of  a mass balance equation on the



basis of a centre-of-the-lake core would  be  highly  speculative.







SUGESTIONS FOR FURTHER RESEARCH



1.  We require many more whole-system measurements  for a wide variety of



    trace metals which have a high affinity  for  lake sediments.   With



    this information, we will be able to  make predictions about

-------
                                                                           139
    catchment - lake interaction,  regional difference in natural and




    anthropogenic burdens,  and long range transport  of  the pollutants.








2.   Since  whole system measurements are tedious  and  costly,  research




    effort should concetrate on ways of reducing the number  of samples




    required to make such a measurement.  Specifically, we should  be




    attempting to formulate predictive relationships which allow whole-




    system parameters to be estimated from a  few samples.








REFERENCES CITED




Dillon, P. J. et. al., 1982. Ont. Ministry of  the Environment report #



     SES 009/82.




Dillon, P. J.  and R. D. Evans, 1982. Hydrobiologia,  91:  121.




Edgington,  D. N. and J. A. Bobbins,  1976. Environ. Sci. & Technol. 10:  266.




Evans, R.  D. and P. J. Dillon, 1982. Hydrobiologia,  91:  131.




Evans, R.  D. and F. H. Rigler, 1980. Environ. Sci &  Technol.,  14:  216.




Evans, R.  D. and F. H. Rigler, 1984. Wat. Air 4  Soil Poll.,  in press.




Forstner,  U. and G.  T.  Wittmann,  1981.  Metal  Pollution  in the Aquatic



     Environment. Springer-Verlag,  New York,  486p.




Goldberg,  E. D. et. al.,  1976. Geochemical Journal,  10:165.



Robbina,.J.  A., 1980. E.P.A. report #600/3-80-080. 309p.

-------
                                                                            140
Table 1.   Whole-lake anthropogenic burdens of zinc,  cadmium, and lead in



          eight lakes in the Haliburton region of southern Ontario.
LAKE Pb
CHUB
CLEAR
CROSSON
DICKIE
HENEY
JERRY
PLASTIC
RED CHALK
BURDEN
(mg/m2)
645
624
627
608
732
735
768
676
Zn BURDEN
(mg/m2)
418
596
322
488
475
587
506
563
Cd BURDEN
'(mg/m2)
8.2
7.2
6.2
8.1
8.9
10.4
7.8
11.3
MEAN VALUES   680
494
8.5
                           (FROM Dillon and Evans, 1982)

-------
                                                                            141
Table 2.  Regional average lead burdens.








REGION              LEAD BURDEN (mg/m2)








Barry's Bay, Ont.           386



Parry Sound, Ont.           388



Haliburton, Ont.            680








Pare des Laurentides, Que.  333




Schefferville, Que.          44

-------
                                                                            142
LIST OF FIGURES



1. Lead profiles in two cores from Found Lake.



2. Historical record of lead deposition as measured in Pound Lake.



3. A comparison of observed and model Pb profiles.



4. Sediment core collection sites on Red Chalk Lake.  The locations



   indicated in the upper figure were sampled in 1978 while the sites in



   the lower figure were sampled in 1980.



5. The relationship between lead mass and lake depth at sampling site in



   Red Chalk Lake.



6. The relationship between lead mass and lake depth at sampling site in



   Bob Lake.



7. The relationship between lead mass and lake depth at sampling site in



   Hope Lake.



8. Copper concentration profiles in five cores from Clearwater Lake.

-------
                                                             143
    o.H
   0.2-1
CJ
 I 0.3-
   0.4-1
Q

LJ
   0.5-f
   0.6H
5  0-7-*
   0.8i
   0.9H
            CONCENTRATION OF LEAD  pg-g"'dry moss
                 200        400       600
FOUND  LAKE


   CORE  I •
   CORE  2 -
      FIGURE 1,
      (.FROM EVANS AND DILLON, 1982)

-------
                                                     144
         HISTORICAL RECORD OF

      LEAD FALLOUT IN HALIBURTON

           COUNTY SINCE 1820

             •—• Core   I

             *—-* Core  2
  i  i  r r  i  i  •T  i.  i  |  i


1800        B50        1900
              -25
             -20



             -15
                                          -10
                                          -5
                  T)
                  cr
     1950   1978
                YEAR
FIGURE 2,
(FROM EVANS AND DILLON, 1982)

-------
                                                                             145
           70
  L«ad Concentration
40      60      80     100
                                            120     140     HO
  02
 ;oa.
«?
 •»
 ll.O-
  14
O
                         BOB LAKE
                           CORE  C
    FIGURE 3,
              (FROM EVANS AND DILLON,  1982)

-------
                                                                                   146
                                                 000m
  RED  CHALK
  La». 45* II'  Long. 78' 3»'
                           ACM*
       Inflow 6
fctlow S
   ft  li.'.lo*  3
     FIGURE  a.

-------
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 cn
 o
 o.
 O
               y= 31.4x4- 364.7   (r2=.89)
                  10
20        30

      Depth/m
40
50
          FIGURE 5,
                    (FROM EVANS AND RlGLER,1980)

-------
   200CH
CM
 l
   1500-
 Q.

 O

 UJ 1000-
 o
 O
 Q_
 O
 cr

 t  500-
       0
4
8
12
i
16
20
24
 I
28
 i
32
36
                               DEPTH  IN LAKE/m
                                                                            CO
      FIGURE 6,

-------
                                                             149
  I60P
   140
 &
 e»
 6
  "120
 o
 £100
 2
 3 80
 a. 60
 u

 §40
 O
 a.
 o
 
-------
                                                                 150
  0.0-
  1.0-
ru
E
o
« 2.OH
a
o
  3.0-
  •4.0-J
                  400
                   t
 Cu Cone.  Cug/g

 BOO
__J	L_
                        1200
1600
 L_
 2000
	I


         —  Cora *1
         —  Core *2
CLERRWRTER  LRKE SEDIMENTS  1979

    	Core *3    	—  Core *5
    	  Core •*
     FIGURE  8,
                 (FROM DILLON  ET  AL,,  1982)

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                                                           151
 Use of Sulfur in Paleolimnological Analyses








               Presentation at



    U.S.E.P.A. Workshop on Paleolimnology








                     by








              Myron J. Mftchel1



        State University of New York



College of Environmental Science and Forestry



             Syracuse, NY  12310

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                                                                             152
                                     Abstract








        Since oxidized sulfur compounds have been implicated in the historical



changes in lake acidification, the use of this element as a paleolimnological



indicator is of critical' importance.  The changes in sulfur concentration in



sediment with depth and thus potentially with time is dependent on the input of



sulfur to the limnetic ecosystem via direct atmospheric deposition and inputs



from streams and groundwater, the latter of which are affected by watershed



characteristics.  In addition, the transfer of sulfur from the overlying water to



the sediment is a function of sedimentation of organic sulfur and dissimilatory



sulfate reduction within the sediment.  The diagenesis of sulfur in the sediment



may obscure historical patterns of sulfur input since redox gradients and



biochemical  processes which affect sulfur transformation may vary with depth.



Despite these limitations, an examination of the sulfur sediment profiles in



lakes in northeastern United States and southeastern Canada demonstrate that



sulfur concentration increases during that period when higher atmospheric inouts



of sulfur due to the combustion of fossil fuel would be expected.  Lakes in which



sulfur inputs to sediments are dominated by sedimentation of organic sulfur



should show a more definitive historical record than those lakes in which



dissimilatory sulfate reduction is the major mechanism for sulfur accumulation.



Future research should concentrate on examining those processes which affect the



transformation and transfer of sulfur both in overlying water and sediment for a



range of lakes which exhibit different limnological  characteristics.

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                                                                              153






                                   Introduction







        This presentation will address briefly five major topics relating to the



use of sulfur In paleolImnologlcal analysis:  1) forms of sulfur In limnetic



systems; 2) sources of sulfur; 3) mechanisms of sulfur accumulation In sediment;



4) depth distribution profiles In lake sediments; and 5) potential  directions for



future research.







                                  Forms of Sulfur



        Sulfur Is found In a wide range of chemical species which include both



organic and Inorganic forms.  Sulfate Is the dominant Inorganic form In oxlc



limnetic systems.  Under conditions of oxygen limitation a variety of reduced



chemical species of sulfur may be produced of which sulflde Is the most notable.



This sulffde may be transformed through a variety of chemical  reactions and form



Iron-sulflde compounds of which pyrlte has the lowest solubility and may



accumulate In sediments.  Also, other Inorganic sulfur forms such as sulfftes,



elemental sulfur, and thiosulfates may be found In lake sediments but are



generally In small concentrations.



        There are also a variety of organic sulfur constituents which may be



divided Into two major classes, carbon-bonded sulfur and ester sulfate.  Many



organic sulfur constituents have carbon to sulfur bonds In both aliphatic and



aromatic forms.  Some of these carbon-bonded sulfur compounds are derived from



the sulfur-containing ami no acids which Include cystlne, cysteine and methlonlne.



These amino acids and other carbon-bonded sulfur constituents are found in all



living organisms.  Another major class of organic sulfur Is composed of ester



sulfates which are formed by a variety of organisms, but are especially Important



products of fungi and bacteria.  Both organic and Inorganic sulfur constituents



are altered during decomposition and humificatlon processes and the actual

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                                                                              154
chemical form of many organic sulfur compounds found in sediments is not known.



Thus many analytical schemes rely on the separation of broad groups of sulfur



constituents (Landers et al. 1983).








                                 Sources of Sulfur



        Sulfur may enter a lake system either from direct atmospheric deposition



or from stream and groundwater inputs.  These latter inputs are generally most



important except for lakes with small watershed to lake area ratios in which



direct atmospheric deposition would be the dominant input.  Watershed inputs of



sulfur are influenced by geology, soil type, vegetation type, hydrology and



atmospheric sulfur contributions.  There is also wide geographical variation in



atmospheric sulfur composition and this variation is directly related to



anthropogenic inputs associated with the combustion of fossil fuels, especially



coal, and the movement of air masses.  The geographical distribution of sulfate



inputs by wet deposition for eastern North America Is given In Galloway and



Whelpdale (1980, Fig. 1).  There Is documentation of recent historical  changes in



anthropogenic sulfur Inputs to the atmosphere as well as changes In sulfate



concentration in precipitation.  Changes in sulfate concentration in those Great



Lakes most Influenced by man show these historical trends (Nriagu and Hem 1978,



Fig. 2).  For the Great Lakes these changes are probably most attributable to



various industrial processes which include sulfur as a by-product.  However, It



may be expected In more remote lakes that changes in limnetic sulfate



concentration may reflect changes In atmospheric inputs if the watershed sulfur



cycle has not had major disruptions.



        There Is a complex series of Interactions which alter both the form and



concentration of sulfur constituents passing through the watershed as shown In



Figure 3.  The quantity of sulfur In throughfal1 varies with vegetation type with



conifer throughfall having a higher concentrations of sulfate than throughfall

-------
                                                                              155
from a hardwood canopy.  Not only Is throughfall enriched in sulfate, it contains



significant components of carbon-bonded sulfur forms as well (David et al. 1984).



As the solution passes through the forest floor sulfur concentration increases



and both soluble carbon-bonded sulfur and ester sulfate forms in addition to



sulfate are found.  A portion of this soluble sulfur is derived from the



decomposition of organic sulfur constituents which are products of both



above-ground litter and below-ground root Inputs.



        Depending on the contact time which is a function of hydrology and the



characteristics of the mineral soil, a portion of this sulfur may be deposited as



organic sulfur constituents or be adsorbed as inorganic sulfate in the 8



horizons.  These sulfur retention parameters are major determinants of both the



quantity and form of sulfur entering stream and ground waters.  These effects



have been demonstrated in decreasing concentrations of sulfate in streams with



decreasing elevation in a watershed in the Canadian Rockies (Mitchell et al.



1984c) and Hubbard Brook in New Hampshire (Fuller et al. 1984).







                Mechanisms of Sulfur Accumulation In Lake Sediments



        Sulfur input to a lake is an integrated response to atmospheric inputs



and watershed effects.  To ascertain some of these relationships we have



determined Inputs, outputs and fluxes of sulfur In South Lake located in the



Adirondack Mountains of New York (Mitchell et al. I964a, Fig. 4).  The importance



of linking sulfur dynamics with lake acidification has been emphasized by various



studies since sulfur fluxes through an ecosystem can have major Impacts on the



hydronfum ion budget.  The empiracle linkage has been shown with nanograms which



relate sulfate loading to pH  levels (Anon. 1981, Fig. 15).  Specifically In lakes



sensitive to acidification, higher sulfate loadings will result in pH depression.



        Moreover, sulfur plays an active blogeochemical role in acidification



processes.  For example, under conditions of dissimilatory sulfate reduction

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                                                                               156




which are often associated with anoxia or high carbon demand, this biochemical



pathway generates alkalinity (Kelly et al. 1982, Fig. 5).  An important process



associated with dissimilatory sulfate reduction is the potential formation of a



series of iron-sulfide compounds including the end product, pyrite.  This process



is important in the accumulation of sulfur in some lake sediments.  A classic



example which demonstrated the importance of this biogeochemical pathway was the



study of Stuiver (1967, Fig. 6) on LInsley Pond.  Within this pond sulfate was



removed from the water column and converted to sulfide within the sediment.  This



pathway accounted for changes in sulfate concentration in the metalimnion and the



hypolimnion.  This process has been documented for other lakes.   For example, in



the Experimental Lakes Area Lake 223, in which suIfuric acid was experimentally



added, the sulfate was reduced to sulfide and the acid addition ameliorated by



the generated alkalinity (Schindler and Turner 1982, Fig. 7).



        Another mechanism for sulfur addition in sediment is by the formation of



organic sulfur compounds.  For example, in Wintergreen Lake (King and Klug 1982,



Fig. 8) a high concentration of ester sulfate was found within the sediment.



This ester sulfate was derived from macrophyte and plankton seston inputs.  In



this hypereutrophtc lake a portion of this ester sulfate was hydrolyzed and



contributed to dissimilatory sulfate reduction.   In our studies  of three New York



lakes, we found that organic sulfur constituents were major sulfur forms in



sediments (Mitchell et ai. 1984b, Fig. 9).  In our detailed study of South Lake



we found that most of the sulfur inputs to sediment were derived from seston



Inputs (Figure 4).  The seston is rich in sulfur (-0.9%)  with ester sulfates and



carbon-bonded sulfur contributing to 57% and 32% of the total sulfur,



respectively.  The dissimilatory sulfate reduction rates of South Lake were



sediments one-tenth those from the Experimental  Lakes Area (i.e.. Lake 223) and



thus dissimilatory sulfate reduction was not a major incorporation pathway.  This



was reflected In the relatively low pyrite concentrations (12% of total  S) in the

-------
                                                                              157
sediment of South Lake.  Recent information from studies of marine sediments has



shown that certain organic sulfur compounds are more refractory than pyrite to



degradation.  Thus, these organic forms may accumulate within sediments.



        A number of studies have developed input and output budgets for sulfate



in lakes.  In most cases, only a small fraction of the sulfate which enters the



lake system is retained within the lake (e.g., Wright 1983, Fig. 10).  In other



cases, It has been estimated that sulfate outputs are slightly greater than



Inputs (Galloway et al. 1980, Fig. 11).  However, most lake sulfur budgets have



only been produced using a mass balance approach for Inputs and outputs of



sulfate with little consideration of Intralake sulfur dynamics.







                  Depth Distribution of Sulfur in Lake Sediments



        To examine sulfur budgets with a paleolimnologlcal approach, the critical



aspect Is to ascertain whether the sulfur Inputs to sediment and the resultant



vertical distribution of sulfur are directly related to historical changes in



limnetic sulfur concentration.  There  is some  Information presently available on



the vertical sulfur distribution of lake sediments.  For example, within



eutrophic Lake Mendota there is a decrease In sulfate and an Increase In sulfide



with depth In the water column due to dissimilatory sulfate reduction (Nrlagu



1968, Fig. 12).  Within the sediment is exhibited a vertical sulfur profile which



is typical of lakes where reduced sulfur Is deposited within the sediment.



Similar profiles have been noted In other lake sediments where dissimilatory



sulfate reduction is a major process.  Although the distribution of sulfur in the



sediment profile may be affected by redox gradients which could alter the



transformation of inorganic sulfate In pore water, the vertical distribution may



also be due to changes In sulfate concentration since the rate of dissimilatory



sulfate is positively correlated to sulfate concentration.



        Furthermore, other sources of sulfur within the sediment such as organic

-------
                                                                              158
sulfur from seston inputs may also be related to historical changes in limnetic

sulfate concentration.  For bacteria and algae which can contribute to the

seston, it has been shown that the organic sulfur fractions increase in response

to sulfate Increases in the surrounding medium.  We have demonstrated that the

sulfur distribution profile of South Lake with its relative high inputs of

organic sulfur would be a reflection of historical increases in sulfur inputs


beginning in the mid-1800's.  A similar pattern is exhibited for Ledge Pond in

Maine (Mitchell et al. 1984a, Fig. 13).  Thus, it can be hypothesized that lake

sediment sulfur profiles-from lakes dominated by organic sulfur inputs should be

less affected by diagenetic processes.  Such historical changes have also been

documented in Southeastern Canada using both total sulfur and stable isotope
                                            D
distribution profiles in various lake sediments (Nriagu and Coker 1983).

        However, it is important to recognize that the origins of sediment sulfur

may vary markedly among lakes.  Recent work by Altschuler et al. (1983)

investigating sulfur dynamics in the Everglades has shown that the sulfur

distribution profile is affected by both inputs and diagenetic processes which

when integrated together produce a profile in which the composition and the

concentration of specific sulfur constituents show a distinct vertical  pattern

(Figure 14).  Thus, the understanding of sulfur profiles in sediments is

dependent upon recognizing and quantifying those processes which affect sulfur

sediment dynamics.




                     Potential Directions for Future Research

        To further our understanding of the use of sulfur in paleolimnological

analysis, research in three areas is needed.  Firstly, processes which affect the

distribution of sulfur in sediments need to be quantified for a spectrum of lake

systems.  Seston inputs, mineralization and diagenetic alterations need to be

ascertained.  Secondly, for a wide variety of lake systems the distribution of

-------
                                                                              159
total sulfur as well as specific organic and Inorganic components need to be



determined.  Lastly, the interactions among lake acidification processes, changes



in limnetic sulfate concentration, and lake sulfur dynamics need to be considered



concomitantly as a potential tool for ascertaining historical changes in lake



b i ogeochem i stry.

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                                                                              160
                                 Literature Cited








Altschuler, Z.S., M.M. Schnepfe, C.C. Sllber and P.O. Simon.  1983.  Sulfur



        diagenesis in Everglades peat and origin of pyrite in coal.  Science



        221:221-227.



Anonymous.  1981.  United States-Canada Memorandum of Intent on Transboundary



        Air Pollution.



David, M.D., H.J. Mitchell and S.C. Schindler.  1984.  Dynamics of organic and



        inorganic sulfur constituents In hardwood forest soils.  In: E.L. Stone



        (ed.) Proceedings of the Sixth North American Forest Soils Conference,



        Knoxville, TN  (in press).



Fuller, R.8., M.J. Mitchell, R. Krouse and C. Driscoll.  1984.  Stable sulfur



        isotope ratios in the Hubbard Brook Ecosystem (in review).



Galloway, J.N., C.L. Scofield, G.R. Hendrey, E.R. Altwicker and D.E.



        Troutman.  1980.  In: D. Drablos and A. Julian (eds.) Ecological



        impact of acid precipitation.  SNSF Project, Oslo, Norway.



Galloway, J.N. and D.M. Whelpdale.  1980.  An atmospheric sulfur budget for



        eastern North America.  Atmos. Envir. 14:407-417.



Kelly, C.A., J.W. Rudd, R.B. Cook, and D.W. Schlndler.  1982.  The



        potential importance of bacterial processes in regulating lake



        acidification.  Limnol. Oceanogr. 27:868-882.



King, G.M. and M.J. Klug.  1982.  Comparative aspects of sulfur mineraliza-



        tion in sediments of a eutrophic lake basin.  Appl.  envir. Microbiol.



        43:1406-1412.



Landers, D.H., M.B. David and M.J. Mitchell.  1983.  Analysis of organic



        and inorganic sulfur constituents in sediments, soils and water.  Int.



        J. envir. anal. Chem. 14:245-256.

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                                                                              161
Mitchell, M.J., M.B. David, D. Maynard and S.A. Telang.  1984c.  Sulfur con-


        stituents of a watershed in the Canadian Rockies of Alberta, Canada


        (in review).


Hitchell, M.J., M.B. David and A.J. Uutala.  I984a.  Sulfur distribution in


        lake sediment profiles as an index of historical depositional


        patterns.  Hydrobiologia (in press).


Mitchell, M.J., D.H. Landers, D.F. Brodowski, G.B. Lawrence and M.B. David.


        1984b.  Organic and inorganic sulfur constituents of the sediments


        in three New York lakes: effect of site, sediment depth and


        season.  Wat. Air Soil Pollut. 21:231-245.


Nriagu, J.O.  1968.  Sulfur metabolism and sedimentary environment: Lake


        Mendota, Wisconsin.  Limnol. Oceanogr. 13:430-439.


Nriagu, J.O. and R.D. Coker.  1983.  Sulphur in sediments chronicles past


        changes in lake acidification.  Nature 303:692-694.


Nriagu, J.O. and J.D. Hem.  1978.  Chemistry of pollutant sulfur in natural


        waters,  p. 221-270.  In: J.O. Nriagu (ed.) Sulfur in the Environ-


        ment, Part 2, Wiley-Interscience, N.Y.


Schindler, D.W. and M.A. Turner.  1982.  Biological, chemical and physical


        responses of lakes to experimental acidification.  Wat. Air Soil


        Pollut. 18:259-271.
                                >

Stuiver, M.  1967.  The sulfur cycle in lake waters during thermal stratifi-


        cation.  Geochim. Cosmochim. Acta 31:2151-2167.


Wright, R.F.  1983.  Input-output budget, of Langtjern, a small acidified


        lake in southern Norway.  Hydrobiologia 100:1-12.

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                                                                                   162
Fig. 1 Wet deposition of SO4-S (gSm~2y~l)in eastern North America for 1977.
     Figure 1.   From  Galloway and Whelpdale (1980).

-------
        Chemistry of Pollutant Sulfur in Natural Waters
                                                                     163
    40
    30-
     20-
 1
 0-10-
 co
           T SUPERIOR
           • MICHIGAN
           * HURON
           • ERIE
           « ONTARIO
             MICHIGAN •""'^HURON
                SUPERIOR A	
      1850       1870       1890       1910       1930

                                      YEAR
1950
1970
Figure 1.  Historical changes in sulfate concentrations in the Great Lakes. (After Beeton,
1965).
 Figure  2.   From Nriagu and  Hem (19?8).

-------
                                    ATMOSPHERE
                                       m* • —

                                        so";
                                            THROUGHFALL
         VEGETATION
         Carbon - Bonded

              504
         teaching     \ Litter.

                      ¥    ill
          l"^^^™^*"™^^™''*—*''^""'"^^^^^^^•^^••i^^^^


            SOIL
  '   'CARBON-BONDED  S '   '
  t
    x ^ _^Immobilization ^~*   •  SMICATF
      ESTER  SULFATE
                                    £---Rant Uptake
        ADSORBED

         SULFATE
" Adsorption-

s-0esorption
              -— -^-^-	2^7    !•
              _ ^-_-,^r L e a chi n g
Figure 3. Conceptual diagram of sulfur transformation and flux in a

       forest ecosystem.

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                                                                       165
Water Input
Sulfate 82
Ecter sulfote 16
Carbon -bonded S 2
Pyrite 0
Other inorganics 0


Direct Atmospheric Input
It-
Water Column
334
s

Seston
Sulfate
Ester sulfo
Car ban -b
Pyrlte
Other lnor(
/
X,
83
te 10
onded S 7
0
ionic S 0
V
f
Sulfate 1 1
Ester sulfate 57
Carbon - bonded S 32
Pyrlte 0
Other Inorganic S 1
\
Sulfate 1 3
Ester sulfate 22 2.79
Carbon - bonded S 52 which
Pyrite 12
Other inorganic S 1
18
f
4C

\
Outflow
Sulfote 82
,-3 Eater sulfate 1 1
0 ^ Carbon- bonded S 7
^ Pyrife 0
Other Inorganic S 0
f
mol S -m"^ In 15.5 cm
corresponds to 135 years
of sedimentation
                               Sediment
figure  A.  A sulfur budget  for South Lake in  the Adirondack region  of  New
          York.  From Mitchell et al.  (198i»).

-------
                                                                                        166
                               Regulation of acidification

  Table 7.  Estimation of hypolimnetic alkalinity production in Lakes 226N, 227, and 223 in response to
increased H*. S
sumincv
1979

Utar")
95
137
291


Net whole-lmke
alkfram
liypol imneuc
reductions*
Hypothetical spnng

H*. .
30
41
23

so,-,
146
214
257

NO,-,
22
20
12

F
0.90
0.94
0.24

Mixed
_^~j_i
1UUUBI
+34
+52
-18
Appfox
gradient
model
+5.0
+ 10
-18
• IB ftoq* liter"*
            Figure 5-   From  Kelly et al. (1982).

-------
                                                                          167
                                                              O.I nig S/  .
                                                                     /CHI
                                                              O.B«* S/cm,
                                                              1.0 mq S/  2
                                                                     /cm*
Fig. 10. The total sulfate budget of Linsley Fond in kg sulfur, calculated for an
early stage  of thermal stratification (left numbers in center squares) and final
stage (right numbers in central squares). The other numbers give the transfer
of sulfate, in "kg sulfur, between the different sections.  At right the total amount
of sulfate reduced and stored per cm2 of sediment during the 4-month interval under
discussion.  Total amount of dissolved hydrogen stdfide at the end of stagnation
            amounts to approximately 15 kg  S in the hypolimnion.
 Figure 6.  From Stuiver (1967).

-------
                                                                      168
                             TABLEV
        Annual S budget for Lake 223. All values are in 103 moles.

Natural Inputs
Bulk precipitation
Direct runoff
Streamflow
Total (!„,)
Acid Addition
Total Input (I)
Outflow (0)
Change in Mass (AM1)
Sedimentation (S)
S/L%
1976
2.6
8.9
0.8
113
101.8
114.1
8.4
78.3
27.4
24
1977
1.7
12.8
3.8
18J
53.5
71.8
23J
24X)
24.5
34
1978
10
16.6
6_5
23.1
62.0
87.1
43.5
20.3
22.3
26
1979
10
10.9
4.6
17.5
51.7
692
373
41.7
-10.4
-15
1980
10-
11.8
0.8
14.6
56.9
71.5
9J
-7J-
69J
97 x - 33
• Approximate values. Neither January 1981 lake chemistry nor precipitation
values for 1980 are available.
Figure  7.   From Schindler and  Turner  (1982).

-------
                      pmol S/g dry w».

                 90     133    IBO	225    270   315
 E
 w
   10
      Protein-S  Ester Sullote-S
Total Sulfur
   FIG. 2. Depth profiles of total ester sulfate, sulfur,
 and protein sulfur profundal sediments in sediments of
 Wintergreen Lake. The absence of error bars means
 that the width of bars is less than the datum point
 diameter.
                                                                    169
Figure 8.   From King and Kl ug  (1982).

-------
                                                                      170
         0.245
      Oneida
                        SULFUR CONSTITUENTS OF LAKES
                            0.498
                                                     0.667
Deer
South
    Non-HI reducible S
            Ester  SO]
                  Suifide
Fig. 3.  Comparison of total S and major S constituents in sediment of three study lakes with all samples
combined. Area is proportional to percent composition (dry mass). Values for percent total S are given.
 Figure 3.  From Mitchell  et al. (198*0.

-------
                                                                                                     171
                                                        SO
                        langrjem 1974-80
                                                     9MMOUS rttUfR
               prtcipiution 2 \
                      Lake 239
                                                                    dtpmition 19
precipitation 3
                                                                  outflow 19
                            outflow 46
Fig. 3. Mean annual flux of sulfate for the period 1974-80 at Langtjern and its terrestrial catchment (4.79 km2) and for 1972 at Lake 239.
ELA (3.96 km') (Schindler et aJ. 1976). Units: Keq • km'2 y1.
          Figure 10.    From  Wright  (1983).

-------
                                                                 172
                                 n
                                 n
                                 n.   r
                                                             JO.
              H   NO,SO,CINH4CaMa    KNaAl




           2. Annual budgets for major components - error < ± 12%
Figure  II.  From Galloway et al. (1980).

-------
                  SULFUR METABOLISM AND SEDIMENTARY ENYlllONMKNT
                                                                                            173
    o r
   20
 •s.
 o
 ui
 O
   40
   60
   80
	O—  SULFIOE-S   i
        TOTAL-S
                    1-0      2-0   0        1-0       2-0
                 CORE I                  CORE  2
                                   SULFUR  CONTENT
                           i-O       2-0
                             GORE  3
3-0
  Fie. 2.  Vertical distribution of sulfur in the  sediments of Lake Mendota. Core 1, depth of water
ss 3.8 m; marl-sludge boundary = 15 to 25 on. Core 2,  depth of water =  11.6  m; marl-sludge
loimdary = 35 to 45 cm.  Core 3, depth of water = 21.3 m; marl-sludge boundary =  40  to 50 cm
Sulfur concentration is expressed in mg/g dry weight of sediments; marl-sludge  boundary is measured
frcm  the mud-water interface.
       Figure  12.   From  Nriagu  (1968).

-------
                                                               174
                        DEPTH  (cm).
            CM
            o
                 ut
                     r
                     >
                     x
                     m
                                                5  q
                                                o  d
                                                N  CO
                                                §   .
      o  a.
      o  SI
                                                *  1
                                                   §Q
                                                   ut
                        a
                        o
                              5    to     3
                     YEAR  DEPOSITED
                       DEPTH  (cm)
            (M
            O
                                        Ol
                     •a r-
                     O f
                     2 O
                     Cf O
                       m
                                                o   a
                                                o   d
                                                   o
                                               s
                                                   CO
                                                   a
                                                   (A
                                                   UI
                      Ol
                      ia

-------
                                                                                         175
       Cor* 3
    25
   1OO
       Cor* S
 o  so
    rs
                                          ,  s

                                          il
                                          I  -8
                                            I
                                                          I
       Cor* •
    29
    ao
    75
0        1.0

 Ab*
-------
                                                                              176
              6
               0             30            60            90
                  SULPHATE Loading to  Lake Water (Kg/ha/yrl
Figure 28.  Effects of various  sulphate  loading  rates on  lake  pH  for  lakes  in
           very sensitive (1)  and somewhat  less  sensitive (2)  surroundings  in
           Sweden.  Added points are for:  (•)  Florida  (Crisman and Brezonik,
           1980); (o) Como Creek (Lewis  and Grant,  1979); (&)  Hubbard Brook
           (Likens et al., 1977); and (x) Norway (Wright  and Snekvik, 1978).
           (modified from Aimer et al.,  1978).
 Figure 15.   From Anon.  (1981).

-------
                                                                           177



                              Sulfur Ofagenesis







                              George R. Holdren







     Until I  came on this trip, I  felt that there were a number of elements



for which there was some hope of getting a reasonable deposition rate from



a sediment core, of learning something about their deposltlonal history.



Now, having watched Merrill HIte and Richard Carlgnan, and from what I've



understood talking to Steve Elsenrelch, the trace metals, the transition



metals, and trace organIcs are moving around a lot.  So there are fewer



things you could really attack for Information.  My Interests Involve



looking at chemical dlagenesis, that Is, at those things for which you



cannot just take a dated core, and obtain a concentration at a given depth



to  learn something about either the timing or the magnitude of Increased



deposltonal fluxes because of post-deposit tonal changes In the distribution



of that particular element.  All of the changes that I am talking about are



lumped into a category which we can call chemical dlagenesis.  Chemical



dlagenesis can be put into one of two categories.  First, we can change the



chemical form of a substance, for example, changing iron oxide to an iron



sulfide or changing an amI no acid into ammonium  ion.  These reactions



change the chemical form, but may not necessarily affect the distribution



of the element.  The other part of chemical dlagenesis, and the part that



I'm going to concentrate on, Is the redistribution of the element within



the sediment column.  It Is really this aspect of diagenesis which, for



certain elements, can make time reconstructions very difficult.



     If we look at the mobilization and redistribution we can categories



the reactions into several types of processes.  There are the physical



processes such as the resuspension which Dr. Jerome Nriagu was talking

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                                                                           178



about, and bioturbatlon, Involving organisms mixing the top part of the



sediment column, In which they are living.  These processes can be



understood by comparing the distributions of elements with things like



   Cs or    Pb.  We can have some Insight Into what the magnltlde



of these physical redistributions are by using these short living time



tracers.



     The chemical aspect of remoblIIzatlon is something which Is a more



complex.  It Involves the transport of an element through the pore water.



The process may result In significant redistribution of the element within



the sediment column.  Now what two things drive the chemical  mobilization



and redistribution?  We need activity gradients In the sediment pore waters



to get transport.  Other things being equal, you need changes in pore water



gradients as a function of depth within the sediment column to get net mass



accumulation or mass depletion from the sediment solids.  The larger the



gradients and the greater the changes In the gradients, the greater the



mass redistribution Is going to be.



     There are some common examples of the types of dlagenetic changes



which occur.  In marine systems, suI fates have been studied extensively



(Figure I).  On the left hand side of Figure I  Is the pore water



Information.  These profiles then generate the corresponding sediment



solids profiles.  We can get these profiles In different forms.  I  have



generalized them, however. Into three categories here.  We can get new mass



added to the system, as In the case of sulfur in marine systems.  Here, we



have sulfate coming Into the sediment where It Is mlcroblally reduced to



hydrogen sulflde.  This, consequently Is turned into acid volatile sulfides



and pyrlte.  These species Increase In the sediment solids as a function of



depth.



     A depletion or net loss of mass from the sediment column occurs In the

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                                                                           179
case of silica.  Here, we normally have low overlying water concentrations
of dissolved silica which Increase to several hundred mlcromoles within the
pore water over an 8-10 cm depth before leveling off.  This Is a result of
the dissolution of biogenlc silica.  As It dissolves, dissolved silica Is
transferred down the gradient and out of the sediment.  This results In
mass lost from the sediment.
     There Is a third broad classification of dlagenetlc redistribution.
There  Is no net change In the total Integrated mass  In the sediment column.
This Is Illustrated by a species such as where there  Is dissolution of the
solid below the oxlc zone, and repreclpltatlon In the surface zone, and/or
at depth.  This produces a profile with relatively large concentration of
dissolved manganese at some depth, and lower concentrations at the surface
and below the concentration maximum.  The solid profile is a mirror Image
of that of the dissolved species.  With this process, there Is no net gain
or loss of mass from the system, Just a redistribution of that mass within
the sediment column.
     To summarize, there are two main points to figure I.  The solid phase
gradients are passive actors.   They are a reflection of what Is going on
or has gone on.  Second, the solid phase gradients mask changes In
historical Inputs which we are trying to get, either directly or
Indirectly, from the study.  All of the action Is happening In the pore
water, as reflected by the pore water gradients.  These gradients are the
things that drive the mass transfer processes.  So, by studying these
gradients, you can gain an Idea about the rates of those reactions which
are affecting the distribution processes.
     If a species is chemically active this should be reflected In pore
water gradients of the species.  For obtaining historical Information from
lake sediments In regions which are receiving acidic  Inputs, the big

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                                                                           180



question Is:  are chemical dIagenesis and redistribution significant enough



to warrant studies?  Are there enough dIagenetic changes to suspect that



these might be having a significant impact on the shapes of the sedimentary



profiles?  Or. Richard Carigan suggested that this was the case with the



trace metals.  However, until now, there have not been many studies which



have addressed this question directly, and, in most literature, one finds



that the presumption has been that the concentrations and the concentration



activity gradients are too small to drive significant redistribution.



     If, as I maintain, post-deposittonal redistribution Is significant,



the next question Is how do we deal with it?  Because pore water



redistributes species over many centimeters, we get a smearing of the



historical  record over that zone where you see the gradient.  Under these



conditions, we need some way to unsmear the record or, otherwise, deal with



that problem.  One way to approach this  Is through the use of the



dIagenetic equation (Figure 2).  For pore waters, this describes the



concentration of the species as a function of time and depth.  The equation



Includes terms for dlffusional transport, for burial plus other advective



processes (e.g.. In seepage lakes, it would be the groundwater influx into



a lake), for removal of a species from the pore waters by precipitation or



microbial uptake reactions and for production of the dissolved species from



the sediment solids.  For any particular element we need to know what each



of these terms are to solve the dlagenetic equation.



     For sulfate, In most systems which have been studied, the production



term, P, can be assumed to be smalI and thus it can be ignored, and the



removal terms are used to describe observed changes In the profile.  Here



removal rates are proportional to the dissolved sulfate concentration in



the pore waters (Cook and Schindler, 1983).  If we solve the dlagenetic



equation using a first-order removal term, we can calculate a profile for

-------
                                                                           181
sulfate under steady-state contIons (I.e., assuming no time dependent
changes In the concentration of sulfate as a function of depth).  The
result Is Illustrated In Figure 3.
     If all  the action Is happening In the pore water, and changes In these
gradients give us the changes In mass accumulation as a function of depth
In the sediments, we can match these changes In the pore waters with
changes In the solids.   The dlagenetlc equation which describes the solids
profile Is somewhat analagous to the previous equation (see Figure 2).  In
this equation, the first term describes the biological mixing, I.e.,
bioturbatlon.  The second term describes burial, but, unlike the situation
with the pore waters, this does not Include evectlve processes like
seepage.  Presumably, the solids are not mobile In this fashion.  The
reaction term, which  Is taken from the change In the sulfate gradient, plus
time dependent changes which occur with the detrltal component.  Solving
this under steady conditions, we end up with the solid sulfur
concentrations as a function of depth.  For any given time or depth, the
sulfur concentration  Is equal to the detrltal plus the dlagenetlc
contribution from the dissolved sulfate (Figure 4).
     If everything is being driven by reactions In the pore waters, how do
we get at the pore water Information?  There are three ways that have been
used to obtain pore water data.  Squeezing and centrlfugatlon are two
techniques which have been used a fair amount In the past In various
sediment pore water studies.  There are certain advantages to these
techniques.  You can extract large volumes of pore water; in fact, you can.
In many cases, extract as much as your patience allows.  Secondly, you
retain the mud from which that water was extracted.
     There are some disadvantages of these two techniques.  Both methods
are prone to significant oxygen and temperature effects.  Anything that Is

-------
                                                                           182



oxygen sensitive (Iron, manganese, phosphorous, hydrogen sulflde, sulfate,



and silica) respond to changes In or exposure to atmospheric oxygen.  To



minimize these effects requires extensive glove bags, or boxes for sampling



handling.  The temperature effect results In essentially an Ion exchange



effect.  As one Increases the temperature, Ions desorb or dissolve from the



solids.  For certain things like silica, changing the temperature from



8°C to 18°C results In a doubling of the amounts of dissolved



silica In the pore waters (Matlsoff, 1978).  The set-ups to minimize both



temperature and oxygen effects are large and costly.  Sampling is



relatively slow for the squeezing, requiring 60-90 minutes per sample



unless you have a huge bank of squeezers.  Sampling time Is a little bit



faster for the centrtfugatlon, but still a time consuming process.  These



methods become increasingly cumbersome  If you're trying to prepare samples



In the field.  It's very difficult to get the equipment to a remote lake.



     A third approach, and one that Is becoming quite popular, is a method



called peepers or pore water equiIIbrators.  These devices have several



advantages.  They are very easy to work with.  Essentially, they consist of



a dialysis bag In a rigid frame.  When you retrieve it, you only have water



present, so you won't have to worry about the temperature effect.  Also,



these devices can be sampled quickly.  Typically, In our set up, which



consists of 24 or 26 samples, complete sampling can be done from start to



finish In about 12 minutes.  Still, the oxygen effect Is evident, but the



approach Is better than squeezing because we have some control over it.



There are some disadvantages, too.  Once you put these in the field. It



requires several weeks for the water to equilibrate.  The exact amount of



time depends upon the  length of the diffusion path.  For example, If you



have a 1 cm long diffusion path in a cell, the device needs about 3-4 weeks



to equilibrate to within 95% of the actual composition.  Also, If you

-------
                                                                           183
require sediment solids, a core must be obtained separately, and this can
raise reasonable questions as to whether the mud Intervals are equivalent
to what the peeper Intervals were looking at.  That Issue Is something
that's difficult to answer.  The cost of a peeper Is about $500 per peeper
frame, making It comparable to or cheaper then the other two methods.  Now,
back to the main topic.
     How does the sediment dIagenesis apply to estimating the timing or
magnitude of Increased deposltlonal  fluxes to remote lakes.  If we look at
sulfate, the major an Ion In modern precipitation, we can study dissolved
sulfate profiles In the pore water to estimate Its mobility.  Typically we
have high concentrations In the overlying water, which decrease with depth
In the sediments.  Based on these gradients and changes In the gradients
with depth, we can calculate the transfer of the sulfur from the lake water
phase Into the sediment solids.  The factors controllng this transfer
Include the concentration of the SO " In the lake water, the rate
of sediment deposition, the activity, diversity, and density of Infaunal
organisms, and several general chemical factors.
     To calculate a mass balance using the dlagenetlc equations we need the
rate of sulfate uptake by the sediment micro-organisms regardless of the
details of the specific reaction.  We can get this directly from the
dissolved sulfate profile In the pore water.  Second, we need the sediment
deposition rate.  Third, we need the dissolved sulfate profile (absolute
concentrations, as well as the gradients.)  Fourth, we need the detrltal
sulfur  Input to the sediments, and finally, we need Information about the
biological mixing coefficient of the surflclal sediments.
     We need to know these things as function of time.  Here we are stuck,
because there Is no good historical  Information on any of these parameters.
For example, what was the lake water sulfate concentration In 1920?   How

-------
                                                                           184
was the mlcroblal activity different then from what It Is now?  How does
the detrltal sulfur Input differ between 1920 and now?  Because there  Is no
really good way to obtain these data, the best that we can probably do Is
study sediments at a lake In an area receiving acidic precipitation but not
suffering drastically from those acidic Inputs.  That Is, we should study a
lake In which the pH of the water Is still 6-7.  In doing this, we can
hope, at least, that the micro-organisms haven't been severely stressed by
reductions  In pH, and that they are responding to their environment in
about the same way as they did prior to acidic deposition.  Under these
conditions the two remaining significant unknowns are the detrital Inputs
and the lake water sulfate concentrations as functions of time.
     Before presenting the detailed results of the calculations, let's
first describe,  in general, the types of profiles which might be expected
from 1) a normal, steady-state sulfate Input and 2) how perturbations of
this input affect the solids' chemistry (Figure 5).  If we stimulate the
bacterial incorporation rate, Increase the lake water sulfate
concentration, or decrease the sedimentation rate, we get an Increase  in
the total sedimentary sulfur concentration.  With time, this would lead to
some new steady state profile as it gradually gets buried in the sediment.
On the other hand. If we Introduce a lot of acid to suppress mlcroblal
processes.  If the sedimentation rates are Increased Cas might happen
through logging and Increased erosion], or if we decrease lake water
sulfate concentrations, the result is a decrease In the total sedimentary
sulfur In the surface sediments.  We can also get combinations of these two
situations  (Figure 6).  We could hypothesize a situation where there  Is an
Increase in the sulfate loading prior to a substantial depression of the
pH.  In this case, we might expect to find an Initial Increase in
sedimentary sulfur followed be a decrease In surflcial sediments as the

-------
                                                                           185



mlcroblal activities become depressed.



     Consider Grass Pond, In the Adirondack Mount tans of New York, a lake



that has a near neutral pH, ca. 6.5, and look at the total sedimentary



sulfur profile (Figure 7).  In the deep sediments, sulfur contents are



about 0.25%.  This value Increases up to about 0.6, the maximum being at a



depth of about 5 cm.  The concentration, then, declines to the surface.



This profile Is something you would expect to observe with an Increased



sulfate  loading.



     The dissolved sulfur profile for Grass Pond Is Illustrated on figure



8.  The heavy line Indicates the sulfate profile, the lighter line



Indicates the hydrogen sulflde profile.  We can use these data to derive


                                                                 -9
the first order rate constant for sulfate asslmiltlon (k = 3 x 10  ).



In contract, the sulflde gradient Implies that mass Is moving up through



the sediments.  However, this transport Is less than about \5% of the



downward sulfate transport, so we can Ignore this reverse flux.



     The next problem  Is to evaluate the sulfate boundary condition.   We



assume the  lake water sulfate concentration to be constant through time.



One thus obtains the expected steady-state profile.  Then, we can envision



various sorts of Increases  In the loading rates (figure 9).  For example,



there could be a long gradual  Increase, followed by a more rapid Increase.



We could attempt to model responces (figure 9) to WW1 and WW11.  From this,



you can see that the boundary condition Is really the great unknown.



Clearly, we don't know what the actual boundary condition Is.  However, the



way we've decided to model  It  Is to assume some steady sulfur Input through



time to  some point at which loadings begin to  Increase.  Then, In 1965,



when we start having some good trend analyses available, (loadings have



been constant to within 2Q% since 1965) have  it stabilize at present day



conditions.  We can vary the time of onset of  increase and use these

-------
                                                                           186



various boundary conditions to calculate total sedimentary sulfur profiles.



I  have assumed that the the detrltal sulfur Inputs have been constant



through time.  The last figure shows some typical examples of the results.



The data points are shown.  Line 2  is the steady state profile, and the



other lines were calculated using the boundary condition shown In the



previous figure.  Assuming that the increase of SO/" started In



1950 results In curve b; curve c assumes an Increase starting In 1935, and



curve d corresponds to an Increase starting In 1920.  Clearly, the 1935



onset date fits the data best.  Remember all that has been done here Is a



mass balance calculation.  We've taken the gradients that were found In the



pore waters to calculate the mass transfer of sulfur Into the sediment.



Finally, we compared those profiles with the actual distributions In the



sediment.  We can also use modelling and balancing approach to estimate



pre-anthropogenic sulfate concentrations In the lake.  Our current



estimates are somewhere In the neighborhood of 10 mlcromolar.  In other



words„ we think that there as been about an 8-fold Increase in the rate of



sulfur delivery to the lake.



     (tow, if the sulfur mobility had been Ignored, and we had just compared


                                  210
the excess sulfur directly to the    Pb, then we would have estimated



an onset of about 1880-1890.  That's based on depth where we first observe



the rise above base level for the total sulfur concentration.  If we



consider sulfur mobility however which allows that essentially modern



sulfur diffuse Into older, deeper sediments, the estimate for the time



since onset Is cut about In half, or to about 1930.



     This is just one example of an approach that can be used to unravel



depositional histories In complicated, chemically reactive sediment



systems.

-------
                                                                                                 187
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       Trace metal diffusion across the sediment-water  Interface:
           Implications  In the chronological  Interpretation of
                  dated trace metal sediment profiles.
                            Richard Cartgnan
     Dated  sediment  profiles  are often used to  recontruct  the  deposition
history  of  anthropogenic  pollutants.  For example,  the rapid  increase  in
concentration of several trace metals (Pb,  Zn,  Cu,  Ni,  Cd, Ag, and others)
observed  in  the  more recent (100 y or less) sediments  of  many  lakes  has
generally been attributed to the Increased atmospheric emission and subsequent
deposition  of  these trace metals.  While trace metal profiles  collected  in
circumneutral  lakes generally show a maximum at the surface,  the most recent
sediments of acid lakes typically show a concentration maximum located one  to
several cm below the sediment-water Interface. In acid lakes, this superficial
decrease  in  trace metals  has usually been interpreted as a result of  their
recent  acidification.  According to this  interpretation,  subsurface  maxima
could  be explained either by the leaching of superficial sediments by  acidic
overlying waters,  or by a decreased sedimentation of some trace metals due to
their   increased  solubility  in  acidic  waters.   The  objective  of   this
presentation is to show that at least another mechanism,  which Is independent
of  hypothetical past changes in acidity,  can lead to the formation of  trace
metal profiles having subsurface maxima.
     Recent  observations  on  porewater  trace metals In acid  lakes  of  the
Sudbury (Ontario) and Quebec (Quebec) regions show that the downward diffusive
flux  of  trace metals across the sediment-water Interface can account  for  a
major  part  of trace metal accumulation by  the  sediments.  Moreover,  trace
metals  can  be diffusively transported several (2-5)  centimeters  below  the
sediment-water   Interface.  Such a mechanism is Illustrated in fig.  1,  where
profiles of porewater and total Ni collected at a depth of 15 m in  Clearwater

-------
                                                                           199
Lake (Sudbury) are presented. At this site, a steep porewater Ni concentration
gradient  (2.0 x 10   umol.cm  .cm  ) is present between I  and 4 cm below  the
sediment-water  interface.  Assuming steady state conditions and using  Pick's
first  law,  as  applied  to  the sedimentary environment (at  10 °C),  it  is
calculated  that  such  a concentration gradient  should  support  a  downward
                            —2  —1
diffusive flux of 16.3 ug.cm  ,y  .  At the same site, the recent accumulation
                                            2 10
rate of Ni in the sediments, estimated from    Pb sedimentation rate and total
                                             —2  —1
Ni  amounts  to  approximately  17  ug  Ni.cm  .y  .  In  this  lake,  similar
calculations  for  Zn and Cu yield similar results.  Diffusion is therefore  a
major  mechanism  by  which  these  sediments  accumulate  trace  metals.  The
porewater  Ni profile also shows that the Ni concentration gradient is  linear
between  1  and  4 cm and vanishes around 4  cm,  where  the  Ni++  presumably
precipitates  as millerite (NiS).  The linear gradient indicates that most  of
the  diffusing  Ni  is transported down to 4 cm below  the  interface  (Pick's
second law), where it accumulates and forms the observed peak in total Ni.
       Chronological    reconstructions  of  trace  metal  deposition  in  lake
sediments  are  usually based on the assumption that  diffusive  transport  is
negligible  within the sediment column.  The above results show that diffusion
should not be ignored in acid lakes.  Chronological reconstructions, and  their
interpretation   in  a  recent  acidification  context, should  therefore   be
considered  with  caution  in the absence of a good knowledge of  trace  metal
diagenesis in recent sediments.

-------
                                                          200
     0
    10
E
u
Q.  20
LL)
   30
   40
POREWATER  Ni  (pm)

     2.5              5.0
                  1000           2000


               TOTAL Ni(ppm)
 Figure 1:  Total  ( O K and porewater (  • )


          Ni in  the sediments of Clearwater lake.

-------
                                                                                201

                                 Stable Isotopes


                                 Gerald Matisoff



      Stable isotopes are perhaps the ideal tracer for geochemical processes.  The


reason is that, in order to trace a particular element, the best thing to use is a


tracer of that element itself (i.e., a different isotope of that element).  In


essence, stable isotopes have tremendous potential for use for just about any kind


of tracing process.  In fact, carbon, oxygen and hydrogen isotopes have been used


extensively to study many geochemical, biogeochemical and biological processes.


      The sketch in Figure 1 illustrates a situation of particular interest to


paleolimnologic studies in remote lake regions.  Lead, nitrogen and sulfur are


released from industrial sources, undergo long range transport, and are deposited


in a remote watershed.  The record preserved in the lake sediments also reflects


contributions from within the watershed and all processes which occur within the


watershed and lake prior to and after deposition.  Of particular interest are the


isotopes of sulfur, nitrogen and lead which may be used to identify the sources of


these materials.  It is hoped that these isotopes can also be used to determine if


the source material is from automobile exhaust or a particular coal burning unit,


and the percentage of the lead sourced from within the watershed and from the at-


mosphere.  There is essentially no work at all on nitrogen isotopes in paleolimnologic


studies, although there is an increasing amount of literature about nitrogen isotopes


in the marine environment.  Here, I will present a review of lead and sulfur isotopes


in paleolimnology.


      Lead isotopes are derived from the uranium and thorium decay series.  U-238

                                                          q
undergoes a decay to lead-206 with a half-life of 4.5 x 10  yrs.  Lead-206 comprises

                                                           0
about 23.6% of all lead.  U-235 has a half-life of 7.1 x 10  yrs and undergoes decay


to lead-207.  Lead-207 comprises about 22.6% of all lead.  Thorium-232 has a half-life


of about 1.4 x 10   yrs and undergoes decay to lead-208.  Lead-208 comprises about

-------
                                                                           202
Figure 1.  Cartoon illustrating the sources and long range transport (LRT)
           of sulfur, nitrogen, and lead to remote lakes.

-------
                                                                                203
52.3% of all lead.  Finally, lead-204 makes up about 1.5% of all lead.  It has a




half-life of about 10   yrs, so for most purposes it is constant.  Natural geological




variations in the uranium to thorium ratio and the different half-lives of the




parents of the lead isotopes have resulted in significant variations in the lead




isotope ratios in different geological materials.  The half-lives are sufficiently




long, so that for paleolimnologic work lead isotope  ratios can be used as conser-




vative tracers of the source materials.  Lead-208 represents about half of the lead




and would be particularly valuable to study.  Since it's derived from thorium as



opposed to uranium, there is the additional problem in that any difference in lead-208/




lead-204 ratios might also reflect differences in the uranium to thorium ratios in




the starting materials.




      Figure 2 shows the lead-208/lead-204 and lead-207/lead-204 ratios versus the




lead-206/lead-204 ratio in surficial sediments.  The data are about 10-15 years old




and are from a variety of sources.  Note that the data tend to fall on a straight




line in both tri-isotope plots.  The reason is fairly straightforward.  As U-238




in the starting material increases, U-235 in the starting material also increases




because the uranium proportions remain approximately the same.  Similarly, the decay




products of those will also increase.  However, in terms of geological materials,




such as basement rocks, the data may not necessarily follow a straight line because




the materials consist of a very large age range.  Data of interest in Figure 2 are




those surficial grab samples from Lake Superior, the Canadian Shield, Hudson Bay,




Great Bear Lake, and Great Slave Lake.  Note that these samples exhibit very high




lead-206/lead-204, lead-207/lead-204 and lead-208/lead-204 ratios.  The lead




isotopic composition is more a function of age of source areas for the sediment




than of rock type because the source rocks contain significant quantities of U




and Th relative to lead.  As a result, these sediments from Precambrian terranes



exhibit the high isotope ratios.

-------
         48.0
           15.5
                18.0
2O.O
                                          22.0
24.0
Fig.   2 207Pb/204Pb  and 20BPb/2<)4Pb versus 2nf> Ph/204 Pb for sediments  ol
Cenozoic age from various localities  rprom  rjoe    1970)
                                                                                                 Area or
                                                                                                 Symbol
                                                                                   Description
                                                                    A             Pelagic sediments of the  Red Sea and  basins of the Atlantic,
                                                                                   Antarctic,  and Indian Oceans except for the Gulf of Aqaba,
                                                                                   HCI soluble lead
                                                                    A             Sediment from the Gulf of Aqaba. HCI soluble lead
                                                                    P             Pelagic sediments from the Pacific Ocean basin, HCI soluble lead
                                                                    ST-GC         Calcareous clastic  sediments  from  the  Salton Trough  and a
                                                                                   manganese nodule from the Gulf of California:
                                                                    o                HCI soluble lead
                                                                    •                residue lead
                                                                    B             Sediments from the Baltic Sea:
                                                                    x               HCI soluble lead
                                                                                   Sediments from Lake Superior in the Canadian Shield:
                                                                    D               HCI and water soluble lead
                                                                    •               residue lead
                                                                    HB            Sediments from Hudsons Bay in the Canadian Shield,  HCI
                                                                                   soluble lead
                                                                    GSL-GBL      Sediments from Great Bear  Lake and Great Slave Lake in the
                                                                                   Canadian Shield:
                                                                    +               HCI soluble lead
                                                                    V             Sediments  from the Mediterranian Sea, HCI soluble lead
                                                                                                                                           ro
                                                                                                                                           o

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                                                                                205
      The lead isotopic composition of ores from the Mississippi Valley district are




shown in Figure 3.  Note that the lead isotope data exhibit considerable overlap




with some of the Precambrian rocks from North America and Cenozoic sediments from




Precambrian terranes, but are significantly more radiogenic (higher ratios) than




Cenozoic and Mesozoic igneous rocks anywhere in the world.




      A literature search reveals that the vast majority of lead isotope studies




in recent sediments has been performed by Patterson and his co-workers.  They report




that the lead-206/lead-207 ratio in most lead ores is in the range of 1.19 to 1.25



(Table 1).  In Missouri lead ores the ratio is much higher, 1.28 to 1.33  They




note that the proportion of U.S. lead ore consumption provided by the use of Missouri




lead ores has increased from 9% of the lead in the U.S. in 1962 to 82% in 1976.




      The question with respect to paleolimnologic work is whether or not this change




in the source material will cause a change in the isotopic composition of atmospheric




lead, and consequently result in downcore changes in the lead isotopic composition




in remote lakes.  There is very limited data for the isotopic composition of atmos-




pheric lead.  Chow et_ al. (1975) report an atmospheric lead-206/lead-207 ratio




~1.15 before 1967 which closely reflects the lead from outside the Missouri district.




They report that the ratio increased to ~1.20 by 1974 and to ~1.23 by 1977.




      Shirahata et^ al. (1980) examined the isotopic composition of lead in sediments




from a remote lake from the High Sierras.  Figure 4 is their plot of the lead-206/



lead-207 ratio leached from pond sediment humus as a function of the date of deposi-




tion.  Superimposed is the atmospheric lead data previously discussed (Table 1).



Note that prior to about 1960 the lead isotopic ratio was around 1.15, reflecting




a source that certainly was not Missouri lead.  After 1960 there seems to be an



increase in the lead-206/lead-207 ratio in the most recent sediments.  A better




defined increase in that ratio was observed in coastal California sediments.  This




indicates that the change in source lead is recorded in remote lake sediments.

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                                                                                206
    44.0 •
    42.0
   &

  |40.0
  09
  8
     38.0
     36.0
   if16'5
   *»
   8
   £16.0
   8

      15.5
       Precambrian
       whole-rocks
       from north america
Cenozoic sedi-
ments from pre-
cambrian terranes
of the world
Cenozoic and mesozolc
igneous rocks of the world
                               Cenozoic sediments from precambrian
                               terranes of the worldv
                                Precambrian whole-rocks
                                from north america
           Cenozoic and mesozoic igneous
           rocks of the world
              18/3
               20.0
           24.0
Fig.3  207Pb/204Pb and 208Pb/20*Pb versus J06Pb/JO*Pb for extremes and means
of four Mississippi Valley districts: 1 Illinois-Kentucky fluorspar district;
2  Southeast Missouri  lead  belt;  3 Tri-State  zinc
district;  4 Wisconsin-Illinois-Iowa  lead-zinc district,
For comparison, enclosed  areas include the kinds of
data as labeled (from Doe,  1970).

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                                                               207
Table 1.     Pb/   Pb ratio in lead ores  and atmospheric lead.
         Data from Shirahata et  al. (1980).
                        206Pb/207Pb      JL      Year
Most Lead  Ores:        -1.19  - 1.25
Missouri Lead Ores:   -1.28  - 1.33
      U.S.  Ore Use:                       95?       1962
                                          21%       1968
                                          57%       1971
                                          825?       1976
Atmospheric Trend:         -1.15                 < 1962
 (California)
                            -1.20                    1974
                            -1.23                    1977

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                                                                                                     208
                 1.280 -
                 1.260 -
1.240  -
                 1.220
                 1.180

                 1.160

                 1.140
                        NATURAL LEAD IN POND SEDIMENT
                        SILICATES AND NATURAL LEAD LEACHED
                        FROM PONO SEDIMENT HUMUS
                            \\\\\\\\\\\\\\\\\
                            ZONE OF EXTRAPOLATED VALUES FROM OLD SEDIMENT
                                     \\\\\V\\
                                                  ANTHROPOGENIC
                                                  ATMOSPHERIC
                                                  LEAD
      _ EXCESS LEAD LEACHED FROM
       PONO SEDIMENT HUMUS
                          1900        1920       1940       I960       1980
                       DATES OF DEPOSITION IN THOMPSON CANYON
Fig.  4 Pbio*/Ptr07 ratios in excess leads leached from pond sediment humus, natural lead in pond
sediment silicates, natural lead leached from pond sediment humus, and atmospheric lead deposited in
           Thompson Canyon correlated with dates of collection in Thompson Canyon.
          From  Shirahata  et  al.  (1980).

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                                                                                209
Another interesting point is that if the lead in the most recent sediment was derived




strictly from atmospheric lead then it would not be possible to use lead isotope




ratios to distinguish between old silicate material and the current anthropogenic




component because there is an overlap of the values.  The old silicate material has




very high lead-206/lead-207 values C-L'25), while current atmospheric values are




also very high (~1.24).




      Here I'd like to present preliminary data that Dr. Holdren and I have collected




from Grass Pond (Herkimer Co., NY).  Figure 5 is a plot of total lead versus sediment




depth.  It is a 'typical1 profile of lead in recent remote lake sediments, where




high values (MOO ppm) are observed at the surface and much lower values (<10 ppm)




occur at depth.  This type of profile is discussed in detail elsewhere in these




proceedings.  Figure 6 presents lead-206/lead-207 ratios from Grass Pond sediment




sections.  Superimposed is the atmospheric trend in the lead isotope ratio observed




in California and presented earlier (Table 1; Fig. 4).  Note that old sediments have




very high lead-206/lead-207 ratios.  Presumably they reflect contributions from



pre-industrialization atmospheric lead plus country rock lead.  Higher




up the core (more recent sediments) the lead-206/lead-207 ratio decreases reflecting




an increased input of anthropogenic, atmospheric lead.  In the most recent sediment



there appears to be a leveling off of the lead-206/lead-207 ratio and perhaps even




a slight increase in the ratio in the topmost sediments.  This may be a reflection




of increased U.S. usage of Missouri Valley lead since 1962 (Table 1).




      Of fundamental importance is whether or not it is possible to determine if




there is more than one source of lead and, if so, what the proportions are of those




sources.  One way of determining the number of sources of lead is to use a tri-isotope




plot  (Fig. 7).  In this type of diagram any one source may not necessarily have a




distinct value of one of the ratios but it is unlikely that two sources will have

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                                                                       210
                                   f=» m  >
              O
               O
1 SO
         £
         u
         I
         h-
         Q.
         UJ
         Q
           50
Figure 5.  Total lead concentration versus sediment depth
           from a core collected in Grass Pond  (Herkimer
           Co., NY).

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                                                                                   211
                 a o
T1 S O
     1 . 3 O
  D
rx 0.


N \

  D
  Q_
         1 Z
                                                                   50
  Figure  6.      Pb/    Pb  ratios  from Grass Pond sediment sections (horizontal
              bars).   Superimposed ('X')  is the atmospheric trend in the lead
              isotope  ratio reported for California (Table 1; Fig. 4).

-------
                                                                               212
     s . ~
 Q_
rv.
o
CM
  1 5 . S
1 1 1 1 1 1
-
2 6
.31
i i i i i i
-
11
:
-
i i i i i i i i i
         1 S . 5
                      2 O S
2O-4
Figure 7.  Lead tri-isotope plot of Grass Pond sediment sections.  Higher
           sample numbers indicate greater burial depth (see Fig. 6).  Note
           expanded ordinate.

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                                                                                213
the same values for both isotope ratios.  Thus, by using two isotope ratios it is




possible to distinguish between two sources.  Mixing of two sources would be repre-




sented as a straight line on a lead-207/lead-204, lead-206/lead-204 plot.  The data




in Figure 7 do seem to lie along a straight line.  Note that the vertical axis is




very expanded.  We don't really know how precise the data are at this point so we




can't say for sure if sample number 2 might actually be off the line.




      In order to test the two component source hypothesis, the data may be compared




to a very simple mixing model (Fig. 8).  In the model, lead is contributed to the



sediment from two sources:  1) background lead with a lead-206/lead-207 ratio of 1.265




and a steady-state flux yielding a lead concentration in the sediment of about 9 ppm,




and 2) varying amounts of atmospherically derived anthropogenic lead of unknown




isotopic composition.  Prior to the introduction of industrial lead the sediment




concentrations of lead would be 9 ppm and the lead-206/lead-207 isotopic ratio would




be 1.265.  Addition of increasing amounts of atmospheric lead with an isotopic ratio



much smaller than the background lead value of 1.265 will generate a curve that has




smaller isotopic ratios with increasing lead concentrations.  Since there is always




a contribution of both sources of lead which are isotopically different from each




other, the curve will asymptotically approach both end members.  Here, I have




selected two values for the lead-206/lead-207 ratio in the atmospheric component.




First, a value of 1.175 was chosen because that approximates the value measured




in California in 1971.  Second, a value of 1.23 was chosen because that is the




current (1977) value in California.  Clearly the data fall off the lines.  There




are several possible interpretations.  First, extra lead might be leached from




the watershed by acidic precipitation.  Thus, more lead would be deposited without




really changing its isotopic composition.  This would cause the data to lie above




the mixing curve.  Two, the estimated value of the lead isotope ratio in the at-

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                                                                                  214
2 O O
R t>—
   O
    1.18
                     206
1 . 2
  Figure 8.  Two lead-spurce-mixing model compared to Grass Pond sediments,
             Assumed    Pb/   Pb ratios of the atmospheric component are
             1.175 and 1.23.

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                                                                                215
mospheric component could be different from the true value.  Since there are no




measurements for the lead value in the Adirondacks, it is possible to try to fit the




data by arbitrarily selecting a lead isotope ratio in the atmospheric component.




However, there is no single value for that ratio which will permit the mixing




curve to go through all the data points.  Another possibility is that the data




reflect transients in the lead isotopic composition of the atmospheric lead.  The




model assumes steady-state inputs and does not address this possibility.  Finally,




the model doesn't account for any post-depositional remobilization of lead in the



system by upward diffusion due to recent acidification if such an effect does




exist.  These preliminary results indicate that it is possible to use lead isotope




ratios to determine the sources of the lead and the proportions of the lead from




each of those sources.  However, they also indicate that there are some additional,




unexplained phenomena.




      Several suggestions for future research are listed in Table 2.  At the present




there are too few case studies to highlight the full utility of this technique.




Additional case studies are needed.  That research must include accurate measure-




ments of the downcore values of lead isotopes in various fractions of lake sediments.




It is also important to determine the isotopic composition of both wet and dry




fallout.  At the moment there is little or no data of this type for anywhere in the




northeast U.S., and especially in remote locations.  The isotopic compositions of




various watershed materials also needs to be measured.  At the moment, there are




no background studies.  The geographical and temporal variation of industrial and




atmospheric lead has been measured in some places, but to my knowledge very little




background work in the northeast U.S. is available.  Certainly the temporal data



has not been monitored.  It is not possible to go back in time and get it, so that




the historical record must be reconstructed from paleolimnologic studies.  The




leaching of lead from watersheds will increase with increasing atmospheric acidic

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                                                      216
TABLE 2. SUGGESTIONS FOR FUTURE WORK

1)  Case Studies
2)  Isotopic Composition of Wet and Dry Fallout
3)  Isotopic Composition of Watershed Materials
4)  Geographical and Temporal Variation of
    Industrial and Atmospheric Lead
5)  Effects of Acidification on Leaching of
    Lead Isotopes
6)  Model of Transient Flux with Bioturbation

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                                                                                217
deposition.  It is unknown if this enhanced weathering will preferentially leach



certain isotopes.  Furthermore, it is also unknown if the acidification of the lake



water will affect the deposition and accumulation of lead in the sediments.



Finally, it is essential to unify this information by including transient depo-



sitional flux and bioturbation in a comprehensive model of the depositional and



post-depositional processes.



      Sulfur is the other element that has stable isotopes of interest in the system.



It has four isotopes that are known:  S-32, S-33, S-34 and S-36.  About 95% of the



total sulfur consists of S-32 while S-34 is about 4.2% of the total sulfur.  There



are large fractionations between S-32 and S-34, so that they are the two isotopes



normally examined.  The standard notation is del S-34 in parts per thousand.  It



is the ratio of S-34 to S-32 in the sample to S-34 to S-32 in the standard Canyon



Diablo troilite, minus 1 times 1,000:



                  ^s\
      634S(%0) =
                   32_
                     S-
sample
          -1
x 1000                                (1)
                       CDT
      The major mechanism for the isotopic fractionation of sulfur is the reduction



of sulfate to sulfide:






      32s04(aq) + H234S(g) = 34SO=(aq) + ^Sg)                              <2>





This reaction has a theoretical fractionation factor of 1.075,  although observed



values for    6S-34 are on the neighborhood of 30-50 parts per thousand.  Isotope



exchange reactions can also be important fractionation mechanisms.  This is par-



ticularly important when attempting to identify the source of industrial sulfur.



In Figure 9 the sulfur isotope fractionation can be seen to be a function of various

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                                                                                             218
    a
     i
    <3
18
16
14
12
10
 8
 6
 4
 2
               100    200
                     300    400    500
                       Temperature, °C
600
700   800
Fig.  9 Theoretical sulfur isotope fractionation curves for pvrite-ealena, pyrite-
sphalerite, and sphalerite-galena .   From  Hoefs  (1973).

-------
                                                                                219
mineral pairs.  With increasing temperature the fractionation of sulfur isotopes




between the two mineral pairs decreases, but at lower temperatures the fractionation




can be quite large.  There is also a fractionation between dissolved aqueous sulfur




species.  Figure 10 shows that the fractionation factor for the sulfate-sulfide




pair is very high at low temperatures and decreases with increasing temperature.




There is also a pH effect.  H-S-sulfide and HS"-sulfide have fractionation factors




of about 1.01 at lower temperatures which decrease with increasing temperature.




This pH effect is much smaller than the oxidation/reduction fractionation displayed



by the sulfate-sulfide couple.




      Typical values of natural variations in sulfur isotopes are presented in Figure




11 and Table 3.  Extraterrestrial material are similar to the isotope standard




and therefore yield 5S-34 values near 0.  Basaltic and granitic rocks also show




very little fractionation.  Metamorphic rocks show a range of fractionation factors




depending on whether or not the sulfur mineral component is sulfide or sulfate, since




sulfides have large negative fractionations and sulfates have large negative fractiona-



tions.  Similarly, sedimentary rocks yield 5S-34 values over the entire range.




Sulfate SS-34 has varied in sea water from +9 to +35%0 throughout geologic history.




It is currently about +20%0.  This has occurred as a result of significant pre-




cipitation of sulfate evaporites (gypsum and anhydrite) or sulfides (pyrite), so




that the sea water sulfur reservoir was affected.  $S-34 in marine pore water




sulfide ranges from very large negative numbers near the sediment surface to positive



values at depth.  The SS-34 value in petroleum depends on the original source of the




sulfur.  If it was sulfate that was reduced to sulfide, then the «S-34 value will




be negative, but if it was from anhydrite, then large positive «S-34 values-would be




expected.  Similarly, coal exhibits a wide range of values.  «S-34 values in native




sulfur are very slightly positive.  Sulfide ores are highly variable and reflect the




source of the sulfur as well as the ore forming process.  Finally, primary igneous



rocks tend to have KS-34 values on the order of 0.

-------
                                                                                       220
1000 In a = 534Sj-534Ss-2
 3     8     S     §     S
                                                    FIGURE  10  Fractionation of sulfur isotopes
                                                    among  S(V2.  H,S (aq),  HS'. and  S': af.• a
                                                    function of the temperature. Note that SOi"2 is
                                                    stronglj' enriched in 3iS relative to S~2 and that
                                                    the enrichment increases with decreasing tem-
                                                    perature. Fractionation of sulfur isotopes among
                                                    H:S (aq) and HS" is less pronounced  but these
                                                    ions clearly prefer JaS  over 35S compared to the
                                                    sulfide ion.  From Hoefs  (1973) .

-------
                                                                                             221
                                     Evaporite sulfate
                            | Ocean water
                                 imentary.
                                           ic rocks
                                            Granitic rocks


                                           Basaltic rocks
                  Extraterrestrial matter
               (meteorites and lunar rocks)
               I	I	I	i
        50    40      30     20     10     0     -10    -20    -30   -40

                                    4 *S in V.

Fig. 11MS/32S distribution in some naturally occurring sulfur compounds (^-varia-

                   tions in '/»relative to Canyon Diablo troilite)

          From  Hoefs   (1973).

-------
                                                              222
Table 3. .Typical values of natural variations in sulfur isotopes,
                                          6J
    rioucj.J.aJ.
Seawater SO^                     +20  (9 to 35 Geologic History)
S.W. Porewater HgS,  N          -32  to + 4
Petroleum                        -8 to +32 ( -15%o <  S0jj)
Coal                             -30 to +32
Native  Sulfur                   +2 to +6
Sulfide Ores                    variable
     Primary Igneous             -0
Sedimentary Rocks
   Sulfates                      -+17
   Sulfides                      —15
 Igneous & Metamorphic Rocks    -2.5

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                                                                                223





      Consider a sediment system in which there is an initial pool of sulfate which




is reduced and/or incorporated into the biological material (Fig. 12).  In an open




system like the ocean, the sulfate maintains the same isotopic composition it started




with.  In Figure 12, the 6S-34 in the sulfate would remain at +10%0.  Since the



fractionation factor doesn't change (here equal to 1.025), the sulfide produced by




reduction of the sulfate would always have a 6S-34 of -15%0.  The situation is




different in a closed system.  Sediments aren't exactly a closed system, but they




are not exactly an open system, either.  Sulfate diffuses into the sediment and is




reduced and/or incorporated into the solid fraction.  In sufficiently organic rich



sediments, the concentration of sulfate goes to 0 as in a closed system.  However,




sediments also have the property of an open system because sulfur is exchanged across




the sediment-water interface.  In a completely closed system sulfate reduction




preferentially removes the light isotope from the remaining sulfate pool, making




the pool of sulfate heavier.  However, the fractionation factor remains the same




so that the 6S-34 in the sulfide also continuously increases.  After all the sul-




fate has been reduced to sulfide the 6S-34 of the total sulfur is exactly the same




as the initial sulfate (+10%0), except that originally it was sulfate and now it's



all sulfide.  Therefore, it is essential to account for sulfur diagenesis when



examining downcore isotopic changes.




      Jtfrgensen (1979) attempted to quantify this sulfur diagenesis in a steady-state,




diffusion, reaction model.  His model (Fig. 13) incorporates sulfate diffusion across




the sediment-interface, bioturbation inhibiting sulfate reduction of the top 15 cm of




the sediment column, sulfate reduction to H_S, sulfide diffusion and precipitation as




pyrite, and sulfide oxidation to sulfate in the top 15 cm.  One of J0rgensen's (1979)




simulations is also presented in Figure 13.  Here he has assumed that open system




conditions prevail for sulfide (10% is precipitated as pyrite) and he has assumed a




fractionation factor of 1.025 for sulfate reduction.  Note that the sulfate concentration

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                                                                                     224
                                                -10  -20
60  50  40   30   20  10
Fig • 1- Variations of ^fS values of sulfide produced and of residual sulfate in a
  closed system. Assumed fractionation factor: 1.025; assumed starting composition
           of sulfate: +10; assumed starting composition of sulfide: -15
          Frora.Hoefs  (1973).

-------
                                                                                              225
      The sulfur cycle in marine sediments. All processes incorporated into the model are shown.
                     SO?*.
I
a

1

            100
            150
                           10
                        )nnet S cm
                       «	   20    0
           4*51.
•10   *20   «30   •AC
                                            FtS,
                                 30
                     10     20
                       F»Sj        pmol S on'1
       Calculated concentrations (A) and isotopic compositions (B) of SOJ~. H2S, and FeSj in the
 model sediment. Concentrations are stated per cm3 fresh sediment. Open system conditions prevailing
                         for sulfide (/ = O.I) and sulfate. a =» 1.022.
Figure  13.   Steady-state,  diffusion,  reaction,  sulfur  isotope
               fractionation  model  for  marine  sediments  (from
               J0rgensen,  1979).

-------
                                                                                226
is constant down to (15 cm) and then decreases.  Reduction of the sulfate increases




the sulfate pool in S-34 so that the $S-34 increases from +20 to +45 per mil.




Because very little sulfide gets precipitated and a large fraction is recycled,




fractionation increases the SS-34 of the pyrite only about 4 or 5 per mil.




      Nriagu and Coker (1976) examined sulfur isotopes in Cake Ontario sediments?"  They




found that sulfate disappeared from the pore waters by about 6 cm (Fig. 14).  The




total sulfur profile shows a subsurface maximum, which probably represents recent




increased sulfate concentrations in the lake water (see Holdren, this volume).




Nriagu and Coker examined the sulfur isotopes in two fractions.  First, the acid




volatile sulfur (essentially FeS) profile shows the exact shape that would be




interpreted in terms of sulfur diagenesis; fairly low $S-34 values at the surface




which increase downcore as sulfate is reduced.  This interpretation implies a




fractionation factor of about 30 per mil which is consistent with known values.




However, the lake value is currently about 7%0 so that the SS-34 of the total




sulfur should not exceed that value.  Both the acid volatile sulfur and the residual



sulfur (fixed sulfur)  are heavier than 7 per rail.  Nriagu and Coker (1976) inter-




preted this as loss of reduced, light H-S sulfur by emission from the sediment.




That would enrich the sediment in the heavy isotope to SS-34 values above the




starting (lake) value.  There is no other reasonable interpretation in a steady-state




system.  Another possibility is that the lake once had a SS-34 of about 24%0 and




recent loading of very light sulfur by industrial sources has lowered the value




to its current level.   A diagenetic interpretation is also consistent with 'the




data except, that the diagenetic model needs to include a heavier sulfur component



in the lake water originally and transient conditions for the <£S-34 in the lake




water.  My interpretation is that both processes are probably important.  Diagenesis



clearly changes the isotopic ratios in the sediment, and there is   mounting



evidence for historical changes in the concentrations (and consequently the




isotopic ratios) in lake water.

-------
                                                                                        227
                       CS] mg/gds

      0  .2  .4  .6  .8  1.0  1.2 l.l) 1.61.8 2.0:.2 2.1
         I    I   I   I    i   I    i   i    I   l    i   I
-15 -10 -5  0   5   10  15   20  I-,   30
 i    i   i   i   i   i    i   i    i   i
  10 -
1
  20 _
  30
                                 Total S
                                           From Nriaeu and Coker
                                           	197C	
                                                                                  Acid
                                                                                Volatile
                                                                                 Sulfur
         I    I   \   i    i   i    i   i    i   i
      0   2   4   6   8   10  12  14   16  18  20  22  24

                       [SOT] mg/1
  Figure 14.   Sulfur fractions and isotopic  composition of Lake Ontario
               sediments.  Data from Nriagu and Coker  (1976).

-------
                                                                                228
      Nriagu and Coker  (1983) also examined six lakes in northern Ontario.  Their




data from one of the lakes is redrawn in Figure 15.  The total sulfur profile is




similar to that observed in many lakes.  Sulfur concentrations exceed 1% dry weight




at the surface and decrease rapidly to  .l-.2% dry weight below about 10 cm.  The




SS-34 shows about a 15 per mil increase downcore from about -8%0 to a more or less




constant value of 5-7%0.  Note that many of the cores exhibit a subsurface maximum




in 
-------
                                                                                         229
                    [S] (dry wtl)

      0   .1  .2 .3  .'i  .5  .6  .7 .8  .9  1.0    -15   -10    -5
         i    i   I   I    i   I   i   i   i
63ftS ',c
                10
   10-
I
u
a
   20 -
   30
                                  From Nrlagu and Coker
                                         1983   .  ..
    Figure 15.  Sulfur and SS-34  from McFarlane Lake sediments (northern
                 Ontario).   Data from Nriagu  and Coker  (1983).

-------
                                                                              230
-1

10-

20.
"e
^ 30-
x
0.
w
'40"

50-
60.

7n _
/ U
0-5 0 5 10 15 -10 -5 0 5 10 15 2v
1 i i i i / i i i i i
*
-------
                                                          231
  TABLE 4. .  SUGGESTIONS FOR FUTURE WORK

1)  Case Studies
2)  Isotopic Composition of Wet and Dry Fallout
3)  Isotopic Composition of Watershed and Lake Materials
4)  Sulfur Diagenesis in Soft-water Lakes
5)  Effects of Acidification and Eutrophication on
    Sulfur Diagenesis
6)  Model of Transient Flux with Bioturbation

-------
                                                                                232






sulfur fractions are emerging.  However, in order to understand their meaning,



we need to understand sulfur diagenesis in particular.  Isotopic compositions of



wet and dry fallout in watershed and lake materials need to be measured to help us



understand sulfur diagenesis and an understanding of sulfur diagenesis can help us



understand the isotopes.  The effects of acidification also need to be addressed.



These reactions are microbially mediated so that acidification would be expected



to have a profound effect on the nature and extent of the reactions.  At present,



we have no idea how acidification will affect either the diagenesis of sulfur or,



for that matter, the isotopes.  Finally, it is necessary to put this all together



in a comprehensive transient diagenetic model where bioturbation and mixing of



new and old materials are included with all the post-depositional reactions.

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                                                                                233
                               REFERENCES CITED






Doe, B.R. (1970).  Lead Isotopes.  Springer-Verlag,  New York,  137 pp.




Hoefs, J. (1973).  Stable Isotope Geochemistry.  Springer-Verlag, New  York,  140 pp.




J^rgensen, B.B. (1979).  A theoretical model of the  stable sulfur isotope dis-




      tribution in marine sediments.  Geochim. Cosmochim. Acta,  V. 54, 363-374.




Nriagu, J.O. and R.D. Coker (1976).  Emission of sulfur from Lake Ontario sediments,




      Limnol. Oceanogr., 485-489.




Nriagu, J.O. and R.D. Coker (1983).  Sulphur in sediment chronicles past changes




      in lake acidification.  Nature, V. 303, 692-694.




Shirahata, H., R.W. Elias, C.C. Patterson, and M. Koide (1980).   Chronological




      variations in concentrations and isotopic compositions of anthropogenic




      atmospheric lead in sediments of a remote subalpine pond.   Geochim.



      Cosmochim. Acta, V. 44, 149-162.

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                                                                     234
Paleolimnological  approaches to the study of acid deposition:
          metal partitioning in lacustrine sediments
            Peter G.C. Campbell and Andre Tessier
                     Universite du Quebec
                     INRS-Eau, C.P. 7500
                      Sainte-Foy, Quebec
                       Canada  G1V 4C7
            Presented at the U.S. EPA Workshop on
       "Progress and problems in the paleolimnological
        analysis of the impact of acidic precipitation
          and related pollutants on lake ecosystems"
          Held at Rockport, Maine, 22-26 May, 1984.

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                                                                           235
                                Introduction

     Metals   introduced  into  the  aquatic  environment,  whether  from
atmospheric  or  terrestrial  sources,  are  distributed  among  a variety  of
physico-chemical  forms.    As  these  different  metal  forms will  generally
exhibit  different  chemical   reactivities,   the  measurement  of  the  total
concentration  of   a particular  metal  provides  little  indication  of  the
metal's potential  interactions with the abiotic or biotic components present
in  the  environment.   The corollary,  of  course,  is  that knowledge  of  the
speciation  of  a   metal   is  useful  for  determining  its   origins  and  for
understanding its  geochemical  behavior (mobility/transport) and  biological
availability.

     Metal  species  exist along  a  size  spectrum   ranging from  dissolved
through colloidal  to particulate phases;  in the context of  this workshop on
paleolimnology  and  its  application  to  acidic precipitation   research,  we
shall emphasize the  right-hand end  of  spectrum, i.e.  those  settleable forms
likely to be  found  in  lacustrine sediments  before/after diagenesis.   Metals
in such sediments  may be:

1.   adsorbed   at   particle   surfaces  (e.g.:  clays;   humic   acids;   iron
     oxyhydroxides);

2.   carbonate-bound  (e.g.:   discrete carbonate  minerals;  co-precipitated
     with major carbonate phases);

3.   occluded   in   iron   and/or  manganese   oxyhydroxides  (e.g.:   discrete
     nodules; cement between particles; coatings on  particles);

4.   organic-bound  (e.g.:  bound up  with organic matter,  in  either  living or
     detrital form);

5.   sulfide-bound   (e.g.:   amorphous  sulfides,    formed  in  s i tu;   more
     crystalline forms);

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                                                                           236
6.   matrix-bound  (e.g.:  bound in lattice  positions  in alumnosilicates, in
     resistant oxides or in resistant sulfides).

Intuitively,  it might  be  expected  that  chemical  reactivity,  geochemical
mobility, and  biological  availability  will  decrease in  the  order  1 > 2, 3,
4,  5  > 6;  the  relative ranking  of  forms  2,  3,  4  and 5  is,  however,  more
difficult to predict.

     In  principle,  the   speciation   of  sediment-bound  metals  could  be
determined   both   by   thermodynamic   calculations   (provided  equilibrium
conditions prevail) and by experimental techniques (Table 1).  The modelling
of  sediment-bound  metals  is  far  less  advanced  than  is that  of  dissolved
species,  primarily  because  the  thermodynamic   data   needed  for  handling
sediment-interstitial water systems  are  not yet  available.  Thus,  the  only
realistic means of  studying metal partitioning in sediments at  the present
time   is   to  fractionate  the   sediment  physically   and/or  chemically.
Conceptually, the solid material  can be partitioned into specific fractions;
sequential   extractions  with  appropriate reagents  can  then  be devised to
leach   successive   fractions   "selectively"   from  the   sediment   sample.
Alternatively,  the  sediment  may  be fractionated physically,   according to
grain  size  or  by  density  gradient separation, and the  individual  fractions
analysed separately.   Many such  experimental  procedures  have  been  proposed
and  applied to  a  wide  variety  of  suspended or surficial  sediments  from
streams and  lakes;  a limited  number  of  sectioned sediment  cores  have  also
been studied in this manner.

     In  this  contribution  to  the  workshop,   the  increasingly  prolific
literature  pertaining   to   metal  partitioning  in sediments   is  summarized
briefly  and   several   important  methodological   problems  are  discussed.
Applications  of  partitioning  procedures in  paleol imnological  studies  are
reviewed,   with  particular  emphasis   on  those  bearing   on the  acid
precipitation phenomenon,  and specific  research  objectives are  formulated.

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1.   Metal partitioning as determined by selective chemical extractions

Choieof
     To extract  sediment-bound  metals  selectively from a particular form  or
phase, one may choose among a variety of different reagents  (see Table  2 for
a  partial   list).    The  reagents  fall  naturally into  classes  of similar
chemical behavior, for example:

*    concentrated  inert   electrolytes   (desorption   of  electrostatically
     adsorbed metals);

»    weak acids  (dissolution of carbonate phases, desorption of specifically
     adsorbed metals);

»    reducing agents  (reduction of amorphous iron and/or manganese  oxides);

«    complexing  agents   (competition  for  metals  complexed  with  organic
     functional  groups, dissolution of precipitates);

o    oxidizing agents (oxidation of organic matter and sul fides);

»    strong  mineral   acids  (dissolution  of  resistant  oxides,   sulfides,
     aluminosilicates).

If  the  extractants are  chosen in order  of  increasing strength,  they can  be
used in sequential fashion; representative examples of this  type of approach
are  shown   in  Table   3,   as  used  for  pollution  studies  in  the  freshwater
(Tessier et a!., 1979; Forstner,  1982)  and marine  environments  (Engler £t
al. , 1977),  or for geochemical  exploration  (Chao and Theobald, 1976).  Note
that  each   of  these   procedures  was  designed  for use with  oxic   (surface)
sediments; this  same comment applies to all other published  sequences.

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                                                                            238
     A number of  points  should  be mentioned in this context.   First of all,
it  would  be  unrealistic  to  think  that  one  could  select a  sequence  of
reagents  that  would  extract   the  individual  fractions  in  order  without
influencing the other  sediment  constituents.   As must be chemically obvious
from  inspection  of Tables  2  and  3,  available  reagents  are  inherently
unselective and any  sequential  extraction  procedure will unavoidably  suffer
from a  certain  lack of  selectivity.   There  is  a related potential  problem
with readsorption in that  if you  liberate  a metal with  a given  reagent then
it  may   readsorb  onto  the  remaining  solid  phases,   i.e.   the  extraction
procedure  itself  may  cause  a  shift  in  the  metal  distribution  pattern.
Precipitation  reactions  may   also  be  a  problem,  particularly  if  sodium
hydroxide  is  used  to  remove  the  organic  fraction (i.e.,  metal  hydroxide
formation).

     Once  the  reagents have been  selected,  there  remains  a decision  as  to
the order  in  which  they are to be  employed.   As is evident in  Table  3,  the
precise  sequence  of extractants  may  vary considerably,  particularly  with
respect to the oxidation of the organic matter present in the  sediment; this
step may follow the reduction procedure (methods  1  and 2), may  be introduced
between two  reduction  steps  (method  3) or may even be  discarded completely
(method  4)!    In  addition,  the exact  experimental conditions  employed  to
conserve  the  sediment  sample,  and  subsequently  to extract  the  different
metal  fractions,  may  influence  the  metal  distribution.   For  example,  the
ratio  of  extractant  to  sediment  may be important,  particularly  if  the
sediment is  consuming  some of  the  reagents,  as  is  the  contact  time between
the sediment  and the  extractant.   It follows  that the  distribution of  a
metal  among  various fractions  is  operationally  defined.    I  would  like  to
dwell  a  little  longer  on two points  in particular:  extraction selectivity
and sample conservation.

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                                                                            239
a    Extraction selectivity

     How can you  go about evaluating  extraction  selectivity?  As  indicated
in Table 4, one can use pure solids or known  geochemical phases, alone  or  in
model sediments built  up  from  various solid phases or in natural  sediments;
these  samples  are  then  subjected   to  the  extraction  procedure   under
evaluation and one  notes  in  which fraction(s) the added metals appear.  One
could also analyze extracts and/or the residual sediment remaining  after the
various  extractions,  and  determine  various complementary  parameters.   For
example,  if  you  were  using a  procedure that  included  a  step  designed  to
remove organic matter,  then you  could follow the fate of the organic matter
and  note  when  it actually  disappeared from your  sediment.   You could also
perform successive  extractions  with  the same  reagent  and  determine to what
extent the first extraction removes the phase of interest;  ideally  the  metal
concentrations  in  the   second  and subsequent extractions with  a  particular
reagent should be much  lower than those in the first extraction.

     Rapin & Forstner  (1983)  used a  number  of  these approaches to evaluate
the  selectivity  of an  extraction  procedure  comprising  five  steps  (cf.
Tessier et al.. 1979):

          step I    NH^OAc, pH 7
          step II    NaOAc / HOAc, pH 5
          step III  NH2OH.HC1 /HOAc, 96°
          step IV    H202 / HN03, 85°,  pH 2; NH^OAc
          step V    concentrated HN03, 120°

Using  both  a  freshwater  and  a  marine   sediment,   they   measured  the
concentration of organic carbon and total sulfur in the residual solid  phase
remaining  after  each   extraction  (Table  b).    For  both  sediments  the
selectivity of the  procedure for organic  matter proved satisfactory, almost
all  of  the  organic carbon  remaining  intact until  the  oxidation  step  (IV).
Similarly,  for the  marine  sample most  of  the   sulfur  remained  with the
residual  sediment  until extraction with  acidic  hydrogen peroxide.   In the

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                                                                            240
freshwater  sediment,   however,   the  selectivity  for  sulfur  was  poor and
appreciable quantities were extracted in each fraction (Table 5).

     In a parallel study the same authors (Rapin & Forstner, 1983)  subjected
a number  of  solid phases to the  extraction  procedure,  notably several pure
carbonates (Ca, Cd, Mn,  Pb), two amorphous  iron/manganese oxides from  deep-
sea nodules,  two  more  crystalline iron  oxide minerals (hematite, goethite),
an amorphous  iron  sulfide  and  a  crystalline  lead  sulfide (galena); in each
case they determined the fate  during extraction of both  the major  metal and
any metals  present as  impurities.   Selectivity  proved  to be  good for the
carbonate  phases   (>85%  extraction  in   fraction   II),  acceptable  for most
metals associated  with  the  amorphous iron/manganese oxides (>80% extraction
in fraction III, except for Cd and Pb),  but poor for those metals present as
impurities  in  the technical  grade  iron  sulfide.    In  this   latter case
appreciable solubilization of Fe, Mn and Cu was noted in fractions  I,  II and
III,  i.e.  before  the  oxidation step  (IV)  that  is  nominally  designed  to
liberate  metal  sulfides.   Note  that the results  from both  the analysis of
residual sediment after extraction (see above) and the use of sulfide  phases
of  known  composition  indicate  that  selectivity  for   metal   sulfides  is
unsatisfactory.

»    Sample conservation

     Let us  now consider a second methodological  point,  namely the need to
preserve  sample  integrity  between  sampling and  analysis.   I  have gleaned
several perspicacious quotes from the literature.

     -  "drying,   grinding  and  contact  with   atmospheric   oxygen  are
        undesirable" - Engler et_al_. (1977);

     -  "effects   of   temperature  changes   during  sample  collection  and
        preparation are very important and should be considered" -  Engler ^t
        al.  (1977);

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                                                                            241
     -  "sample handling and pre-treatments may noticeably affect extraction
        results" - Jenne & Luoma (1977).

Experimental  data  to support  these contentions  were  not presented  in the
original publications, but recent results from our laboratory have served to
emphasize  their relevance  and  demonstrate  how  important  the  effects  of
sample pre-treatment may be.

     Conscious  that  there  are  often  unavoidable  delays  between  sample
collection  and  the  subsequent  analyses,  we  experimented  with  various
preservation  techniques:    wet  storage  (1-4°C),  freezing,  freeze-dry ing,
drying under a nitrogen stream (20°C), drying under air in a convection oven
(105°C).   Using  the familiar sequence of  extractants  (Table 6), we studied
several natural  sediments,  both  oxic and  anoxic.   In all  cases the fresh
sediment was  subjected  to  the extraction  procedure within  48  h of sampling
and the resulting metal distribution  was used as  a reference for comparison
with  the  distributions  obtained  after  different  sample  pre-treatments.
Representative results are shown in Figures l(a) and (b) for fractions I and
II  extracted from  an  anoxic  sediment  (lake Magog,  Quebec).    The  dashed
horizontal  line  corresponds  to the fresh  sample  (100%);  values  above/below
this  line  indicate an  increased/decreased extractability.   Clearly  sample
pre-treatment  influenced  the  distribution  of  metals   among   the  various
fractions; of the preservation methods tested, those involving the drying of
the sediment (air-drying;  N2-drying;  freeze-dry ing)   had  especially  marked
effects.    Among  the  different  metals   studied,  copper  and  zinc  were
particularly  sensitive  to  sample pre-treatment,  extractions  I-II being the
fractions most affected.

     Similar  results  were  obtained  for oxic  sediments, but  as  expected the
changes were somewhat less dramatic than those observed with anoxic samples.
In  the  light of  these  results we  would  strongly  urge  that drying  of the
sediments  be  avoided;   acceptable   preservation  techniques  would  include
short-term wet storage  (dark; 1-2°C) or freezing.

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                                                                            242
     In a  related  study  (Table 7) we  have  also evaluated the importance of
maintaining  an  oxygen-free  atmosphere  during  the  manipulation  of anoxic
sediments, a  point of obvious importance when  dealing  with sediment cores.
Two anoxic  sediments  were subjected  to  the usual extraction  procedure: in
one experiment the manipulations  were carried  out  in  a glove  box under a
nitrogen  atmosphere  and  the  reagents  used  for  the  first three extractions
were  deoxygenated  prior  to  use,  whereas in  the second  experiment no  such
precautions  were taken.    The  acid-volatile  sulfide  (AVS) content  of the
sediments was  measured on the  fresh  sediment  (100%) and after  each of the
first  three   extraction  steps  (Table 8).    If oxygen  was not rigorously
excluded,  AVS   concentrations   dropped  markedly   during   the   first  two
extractions;   11-38%  remained  after  treatment  with  MgCl2,   1-20%  after
reaction  with  the NaOAc/HOAc  (pH 5)  buffer.    If  a working  atmosphere of
nitrogen was maintained,  the AVS levels were preserved through the  first two
extractions  (87-97%)  but were  reduced  to  <  5% of the initial concentrations
after  treatment  with   the  NH2OH»HCl/HOAc  reagent.   Note that even in  this
most  favorable  case  the  acid-volatile (amorphous) sulfides are  removed not
in  the oxidation  step (IV)  but  rather  during the  extraction  designed to
solubilize the Fe/Mn oxides present in the sample.  This lack of selectivity
of  the extraction  procedure  with respect  to  sulfide phases  was   mentioned
earlier.

     Consider now the  influence of adventitious  oxygen, not on acid-volatile
sulfides  but  rather  on metal  partitioning  in  the  sediment.  In the absence
of  precautions  taken  to  exclude  oxygen,  several  general    trends  were
observed:

     fraction I:    increase   Cd Co Cr Cu.Ni Pb Zn
                    decrease   Fe Mn

              III:   increase   Co Cu Ni Fe Mn

              IV:   decrease   Cd Cr Cu Ni Zn Fe

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                                                                            243
Representative results are  shown  in  Table 9 (Fe) and Tables  10-11  (Pb).   In
the former case, for the lake Nepahwin sediment, the decrease  in  fractions  I
and II was accompanied by  an  increase in fraction III, as would  be  expected
if oxidation  of  ferrous  to ferric ion  had  occurred during sample  handling;
indentical results  were  observed  for  the lake  Aylmer  sediment.   For  lead,
fractions II  and III were also very sensitive to the introduction of  oxygen,
but in  this  case the two  samples exhibited contrasting  behavior:    for  the
lake Nepahwin sediment a marked increase  in fraction II was accompanied by  a
corresponding decrease in  fraction III,  whereas for  the  lake Aylmer  sample
an equally important  but opposite shift  occurred  (F  II  +;  F III t).  These
latter results illustrate the fact that it generally will not  be  possible to
predict  the   consequences   of  not  having   prevented   the   introduction   of
adventitious   oxygen,  i.e.  it will be  impossible to "correct" retroactively
data that have  been obtained without  adequate  precautions.   As will  become
evident  in part  2  of this  presentation  (see  below);  this is  an  exceedingly
unfortunate  conclusion  since  virtually all  the available paleolimnological
data have been  generated either from  dried  sediments  or from wet  sediments
that have been allowed to come in  contact with  adventitious oxygen.

     In  summary,  our evaluation  of  the  effects of  sample  pre-treatment  on
metal  partitioning  in sediments leads  to  the following conclusions:

     -   no storage  method  tested  completely  preserves  the initial  chemical
         and physical characteristics of the sediments;

     -   if a variety of extractants  are to  be used  (e.g.   sequentially),
         there  is  no choice  but  to  perform  the  extractions  as  soon   as
         possible after collection;

     -   drying of the sediment (air-dry ing, N2-dry ing, freeze-dry ing)  should
         be avoided  at all costs;

     -   possible preservation  techniques  include wet  storage (dark,  1-2°C)
         or freezing;

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                                                                            244
     -  for anoxic sediments the maintenance of oxygen- free conditions  is  of
        critical importance during the extraction procedures.

Finally,  several  lines of  evidence  suggest that  for sul fide- rich  (anoxic)
sediments  the  various  extraction  procedures  currently  in  use   in  the
environmental  field  (cf.  Table  1, methods 1-3) will  be compromised by the
tendency  of  the metal -containing sul fide phases to be progressively  (rather
than selectively) extracted from the host  sediment.

                                ******

2.   Paleolimnological  applications

     In  this  section  we  shall   consider how  the  determination  of metal
partitioning  in  sediment   cores  might  be  helpful   in  the  study  of  acid
deposition,   e.g.   in  determining  the  chronology   of  environmental
acidification,  or  in  evaluating  geochemical   responses  to  acidification.
Three  questions  merit  our  attention,  namely  the  effects of  (i)  sediment
diagenesis,  (ii)   atmospheric  inputs  of metals   and  (iii)  environmental
acidification  on the partitioning of metals in sediments.
Effects
     To identify down-core changes in metal partitioning that are  related  to
environmental acidification,  it  will  first be  necessary  to account for any
changes  due to  sediment  diagenesis.    Chemical  reactions  occurring after
sediment deposition will include:

     -  the breakdown of organic matter;
     -  the removal of dissolved 02;
     -  the reduction of N03-, SO^-  HC03-;
     -  the production of C02, NH,/, HP01+2-} HS~, CH^ ;
     -  the reduction of Fe, Mn oxy hydroxides;
     -  the formation of metal sul fides, carbonates.

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                                                                            245
Down-core changes  in the  concentrations  of such  parameters  as 02,  pe,  pH,
SO^,  S2~,   and dissolved  organic  carbon  (DOC)  may  thus  be  anticipated.
Concomitant changes  in  the chemical  nature of the dissolved  and particulate
organic  carbon may  also  be  expected.   Similarly,   sediment compaction  at
depth will  lead  to  a decrease in the  surface area available  for adsorption.
Integrating  these  changes  in  a  qualitative  conceptual  model,  one  can
identify  the  possible effects of  sediment di agenesis on  metal  partitioning
in  sediments;  in effect, on analyzing  successively older sediment strata one
might anticipate:

     -  a decrease in the  adsorbed fraction  (F I);
     -  a decrease in the  easily/moderately  reducible  fraction  (F III);
     -  a decrease in metals  formerly  adsorbed to  this fraction  (F II);
     -  an  increase  in  the  sulfidic  fraction  (F III  in recent  sediments,
        F IV as crystallinity  increases);
     -  an  increase  in the carbonate fraction  (F  II).

Clearly there  is  no  evident trend on  going down the  core.  This can  best be
attributed   to  the  previously   demonstrated   inadequacy   of   the   common
extraction  procedures  when  applied  to   anoxic  sediments.    As  mentioned
earlier, these procedures  were developed for surficial  (oxic)  sediments  but
subsequently have been used rather indiscriminately  in the study of sediment
cores.
lf!e£t.s_ 2f_i£C£6jiS£d_ata£S£h£ri_c_l2ajli£gs- of _metal_s_ (at  constant  pH)
     Once  again,  to  identify  down-core changes  in  metal  partitioning  that
are  related  to environmental  acidification,  it will  first  be necessary  to
consider  any  changes  brought  about by  increased  atmospheric  loadings  of
metals  (i.e.,  direct  deposition).   If  the  metal  input  is  in dissolved  or
acid-leachable  form,   then  one would  anticipate increases  in the  relative
proportions  of  one  or  more  of  the  non-detrital   metal  fractions  in  the
sediments  (e.g.,  Fe/Mn  oxides,  F  III);  such  changes  have  indeed  been
observed  in  surface  sediments  affected by  mine drainage  (Tessier etal . ,

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                                                                            246
1980;  1982)  and  by  air-borne  smelter  emissions   (Campbell  &  Tessier,
unpublished  data  from the  Rouyn-Noranda area, Quebec).   Alternatively,  if
the metal  input  is  in particulate,  non-leachable  and settleable form,  then
one  might  anticipate an   increase  in  the  relative  contribution  of   the
residual  fraction  (F  V).    This  latter suggestion  was first  advanced  by
Patchineelam  and  Forstner  (1977),  who  observed   an  increase  in   the
concentration and relative  proportion  of  residual  metal  in the  upper  or
intermediate strata  of  a sediment  core  taken from the  German Bight.    They
attributed  these   increases   to  inputs  of  metal -containing  atmospheric
particulate  material  that  passed  through  the  water  column  unchanged,
resisted  diagenetic  change and thus  was  preserved  within  the  sediment
without transformation.   This intriguing observation does not  appear to  have
been followed up.
Effects
     Finally,  adding  the third  element to  our conceptual  model,  we might
anticipate that environmental acidification would lead to  a  lower efficiency
of metal capture by suspended solids in the lake water column  (Dillon, 1982;
Dillon  &  Smith,  1982);  total  concentrations  of certain  metals  in the  lake
sediments  might  thus  be  expected  to  decrease.    With  respect  to metal
partitioning  in  these  sediments,   based  on  laboratory  studies  of metal
adsorption  on  well -character!' zed  hydrous  metal  oxides   (Fe,  Mn, Al )  as  a
function  of pH  (Kinniburgh  &  Jackson, 1981),  environmental  acidification
would  be  expected  to  cause  a  decrease  in  the  relative  proportion  of
specifically  adsorbed  metals  (i.e.,  fraction  F  II   in  our  sequential
extraction procedure: Table 3, method  I).  Similarly, a decrease  in pH might
be expected  to lead  to  the  dissolution of any  carbonate phases present  in
the  sediment   (also   fraction  F   II).    Other  more   subtle   effects   of
acidification  can  be  envisaged;  for  example,   increased  sulfate reduction
(Kelly  et  al .,  1982)  might lead to  an increase in metal  sulfide formation.
However, as mentioned earlier, these sulfide-bound metals  tend not to appear
in a particulate  fraction  but  rather to be extracted progressively from the
sediment, appearing in several fractions.

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                                                                            247
     Experimental  data  relating  to  these  predicted  changes   have   been
provided by both Gambrell  and  Khalid (Gambrell  et al., 1980; Khalid  et al.,
1981),  who  determined  the effect  of pH  changes on  metal  partitioning  in
river  sediments.   In  their laboratory  incubations  of  sediments  in closed
containers, a decrease in pH from 8  to 5 led to an increase  in  the levels  of
dissolved  and  exchangeable  cadmium and  zinc,  i.e.  to  an  increase  in  the
geochemical mobility  of these  metals.    In a natural  (i.e.,  open)  system,
such  an  increase in  mobility would  result in  a  net  loss  of the  metal  from
the  sediment.    In  contact,  lead and  mercury  were  little affected by  pH
changes in this  range.   As indicated in Table 12, the increase  in dissolved
and  exchangeable cadmium occurred at the  expense of the  "organic  fraction"
(H202/HN03 extraction,   F  IV),  whereas  in  the   case  of  zinc   there was  a
corresponding  decrease  in  the  relative  contribution   of  the   reducible
fraction (NH2OH.HCl/HOAc extraction, F III).
     Having considered  how sediment  di agenesis,  increased metal inputs  and
environmental  acidification  may  affect metal partitioning in  sediments,  let
us now examine  the  available  data for metal partitioning  in  sediment  cores.
We have identified  some  21 such  studies:    10 in  the  marine environment,  the
earliest dating from 1972, and 11  from  freshwater systems, starting  somewhat
later, in 1979.   Given the purpose of  this  workshop,  we  have  considered only
those  investigations  carried  out in  lacustrine   (freshwater)  environments.
The  relevant  data  have  been summarized  in two  tables*,  for  circumneutral
(Table 13) and  acid lakes  (Table  14).

     For studies performed on sediments from circumneutral lakes,  in all  but
one  case   the   sediment  sample  was   preserved  by  freeze- dry ing;  the  only
exception is the  study  of  Baiker, as cited  by Forstner  (1982),  for  which no
*  N.B.:  The  present  authors would  appreciate  learning  of any  freshwater
          studies that may have been omitted  from this  compilation.

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                                                                            248
perservation technique is indicated.  As has been mentioned earlier,  freeze-
drying affects metal partitioning  in  sediments.   Note also that  in  no cases
were precautions  taken  to exclude  oxygen  from the  lower (anoxic)  sediment
strata.  Clearly the metal distributions reported in these studies cannot  be
considered  representative  of  the  metal   partitioning  in  the  different
sediment  strata  in  situ  at  time of  sampling.    Even  with  this   caveat,
however,  some  potentially  useful  information  can  be  derived  from these
studies.    For  example,  Dominik  and  co-workers  (1983)  determined  the
distribution of copper  and  zinc in two  cores  from lake Geneva (0-1, 31-33,
75-80  cm  strata), using  an  extraction  scheme identical  to  that described
earlier and used  by  Rapin and Forstner  (1983).   Total metal concentrations
were higher in the upper sediment strata, this increased concentration being
associated with non-detrital fractions  (F  II  for Zn, F IV for Cu).   Similar
observations have  been  made  by Baiker  (1982), who  noted  Zn accumulation  in
the  carbonate  fraction  F  II  in  lake  Constance  sediments,  as  well  as  by
Manning and co-workers  (1983), who  reported  Cu,  Pb  and  Zn  accumulation  in
the  reducible  fraction  F  III in  lake Ontario  sediments.   As mentioned
earlier,  this  type of  distribution pattern  is  indicative  of  an increased
anthropogenic   input  of  metal   (not necessarily  of  atmospheric  origin)  in
dissolved or Teachable particulate form.  Dominik et al. also noted  that the
partitioning  of 210Pb  in their  cores  differed  from  that  of  stable   lead
(Figure 2):    for 210Pb  the  reducible  fraction  dominated  (NH2OH-HCl/HOAc
extraction, F  III) whereas  for stable  lead the  most important contribution
was  that  of  fraction II  (NaOAc/HOAc  extraction).   These authors suggested
that there were at least two distinct sources  of lead, lead speciation being
different  for  each source  and exchange among the  different  species being
slow.   In  view of their potential  implications  in the development  of 210Pb
dating  models,  these  results  clearly merit  further   study  in   properly
preserved  sediment cores  for which artifacts  due  to sample  handling may  be
discounted.

     For studies performed on cores from acid  lakes  (Table 14), it should  be
noted  that in  3 of 6  instances the sediment was air-dried; in the remaining
studies  the  sediments  were  stored  wet,  but in  2  of  these  3  cases  no

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                                                                            249
precautions were taken to  exclude  oxygen from the anoxic sub-samples  during
the  extraction  procedure.     Once   again  it  is  clear  that  the  metal
distribution  patterns  observed  in  all   but  one  of these  studies have  been
altered by  sample  pre-treatment and  cannot  be considered representative  of
the metal  partitioning that existed in the original intact cores.

     Despite  these  problems,   it  is   intructive  to consider  the  results  of
Reuther and  co-workers  (1981),  who  determined  the  partitioning  of several
metals in sediment cores  from lakes  Hovvatn  (pH 4.4) and Langtern  (pH 4.95)
in Norway.   For the  lake of  lower  pH  they  noted a decrease  in the total
concentrations  of  cadmium and zinc  (but not  lead)  in the  upper sediment
strata.   This  decrease  was  attributed  to the remobilization  of  Cd  and  Zn
from the  sediment, mainly from the organic  and  easily  reducible fractions,
respectively.   That  this apparent remobilization  was noted  in lake Hovvatn
but  not  in  lake  Langtern   suggested   to  the  authors  the  concept  of  a
"threshold pH", a value  below which  the  pH must drop before mobilization  is
observed  (c.f.  Norton et al.,  1981).    Similar  results  were subsequently
reported  by  the  same  authors  (Reuther et  al.,  1983)  for  lake Gardsjon
(pH 4.7)  in Sweden.   For Clearwater lake (pH  4.65) located near Sudbury,
Ontario,  total  zinc  concentrations   also decreased  in the  upper sediment
strata,  this  decrease  again  occurring  predominantly  in  the   reducible
fraction  (Rapin et al.,  1984).   However, data for Dart lake  (pH  5.2)  in New
York  showed  no evidence of  zinc  mobilization  as concentrations  increased
monotonically towards the sediment-water  interface (White, 1984).
        f
     The^Te is a certain seductive consistency  among all  the results obtained
at pH  values  less  than ~ 4.8, notably for Zn  -  see  Figures  3a, b, c.   Note
also  that this  apparent  mobilization   of Zn from  the  reducible  fraction
agrees with the laboratory simulations  reported  by Gambrell  et al. (1980) -
see Table 12.   However, Reuther  and his co-workers  did not  consider  the
potential   effects  of  sediment  diagenesis  on  zinc  partitioning  in  their
sediment  cores.   That such  diagenetic  effects  may  indeed  be  important  is
suggested by  the  results obtained by Viel et al.  (1983)  for a core from
circumneutral   lago  Maggiore,  situated  on   the  Switzerland-Italy   border

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                                                                            250
(Figure 3d).   The authors attributed  the  increase in zinc concentration  at
intermediate  depth  (notably  in the  reducible fraction)  to  the  diagenetic
formation  of   vivianite  (FePO^) and   the  co-precipitation of  zinc.    Th'is
result  underlines  the  danger  inherent  in  interpreting decreased  metal
concentrations  near  the  sediment-water  interface solely  in  terms of  metal
mobilization  upward  towards  the  overlying water  column  (Reuther  et  al.,
1981; 1983).   It  is  imperative to  consider the possible  effects of sediment
diagenesis on  total  metal  concentrations and  on  metal  partitioning;  one  of
the  best  ways  to  follow  such  diagenetic  processes   is   to  sample the
interstitial   water  (e.g.,  with in  situ  dialysis chambers)  and  determine
down-core  gradients  of  the  parameters  of  interest  not only in  the  solid
phase, but also in the associated interstitial water.

     In  summary,  our  analysis  of   published  applications  of  selective
extraction procedures to the paleolimnological study of  lake  sediments  leads
to two principal conclusions:
             .?-•'•''"''"'"/
     -  metal ^distribution patterns  reported in  the literature for sediment
        cores  (Tables  13,  14) have been  influenced by sample pre-treatment
        and cannot  be  considered  representative  of  the metal  partitioning
        that existed in the original lake sediment;

     -  to identify down-core changes  in metal partitioning that are  related
        to environmental  acidification,   it  will  be  necessary  to "correct"
        for any  down-core  changes  due to  sediment  diagenesis or to  changes
        in the direct atmospheric deposition of metals.

3.   Recommendations

     In light of the various methodological considerations developed  earlier
in this presentation (part 1),  and  taking into account our conclusions  with
respect to  the potential  application  of  selective  extraction procedures  in
paleolimnological  studies   (part   2),  we  offer  the   following  research
recommendations:

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                                                                            251
     -  develop  selective  extraction  procedures  better  adapted  to  anoxic
        (sulfide-rich) sediments (i.e., more selective for sulfidic phases);

     -  determine the  speciation of  the  atmospheric inputs  of  certain key
        metals  (e.g.,  the  relative importance  of  leachable-particulate and
        insoluble-particulate forms of  Cd,  Zn and Pb)  in  order  to evaluate
        whether particulate atmospheric inputs can persist unchanged in lake
        sediments and  thus directly  influence  metal partitioning in these
        sediments (cf. Patchineelan & Forstner,  1977);

     -  compare  the  partitioning  of   210Pb  with  that  of   stable  Pb,  in
        properly  preserved/handled sediments,   in  order  to  determine  the
        generality  of  the  apparent disequilibrium  reported  for  lake Geneva
        sediments by Dominik et al. (1983);

     -  for those metals reported  to  be mobilized  from  lake sediments below
        a certain threshold pH value (e.g., Cd,  Mn, Zn), determine down-core
        changes   in  metal   partitioning   in   properly   preserved/handled
        sediments collected  from  lakes selected  along  a pH  gradient,  and
        combine  these  measurements with  the  appropriate  analysis of down-
        core  changes  in  interstitial  water  chemistry   ...  in  order  to
        distinguish   between  changes   attributable  to  "normal"   diagenetic
        processes and  those induced by  acidification of the overlying water
        column.  These  same measurements  could  also be  performed within the
        framework of an experimental  lake acidification programme.

                              Acknowledgements

     Unpublished  data  were  graciously  furnished  by  R.D.  Evans  (Trent
University),  M.S.   (Jesse)   Ford  (Ecosystems  Research   Centre,  Cornell
University), J.R. White  (Indiana University), as well  as  by R. Carignan and
F. Rapin of our  research center.   Discussions with the  latter two colleages
were invaluable in the preparation of this report.

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                                                                            252
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Chao, T.T. and P.K. Theobald (1976).
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                                                                           253
Dillon, P.J. (1982).
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Evans, R.D. and C.J. Parliament   (1983).
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Accumulative phases for  heavy  metals in limnic sediments.  Hydrobiologia 91:
269-284.

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                                                                            254
Gambrell, R.P., R.A. Khalid and W.H. Patrick  (1980).
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suspensions  as  affected by pH  and redox.   Environ.  Sci. Technol.  14:  431-
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Gupta, S.K. and K.Y. Chen (1975).
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Holmgren, G.S.  (1967).
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Jackson, M.L. (1958).
Soil chemical analysis.  Prentice Hall, Englewood Cliffs, N.J., 498  pp.

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Kelly, C.A., J.W.M. Rudd, R.B. Cook and D.W. Schindler  (1982).
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Khalid, R.A., R.P. Gambrell  and W.H. Patrick  (1981).
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Qual. 10: 523-528.

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                                                                            255
Kinniburgh, D.G. and M.L. Jackson (1981).
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Inorganics at Solid-Liquid  Interfaces,  M.A.  Anderson and A.J. Rubin  [eds.],
Ann Arbor, MI, Ann Arbor Sci. Publ., Chapter 3, p. 91-160.

Manning, P.G., K.R. Lum and T. Birchall  (1983).
Forms of  iron,  phosphorus and  trace-metal  ions in  a layered sediment core
from lake Ontario.  Can. Mineralogist 21: 121-128.

Norton, S.A., C.T. Hess and R.B. Davies  (1981).
Rates of accumulation of heavy metals in pre- and post-European sediments in
New  England  Lakes.    In:    Atmospheric  Pollutants   in  Natural   Waters,
S.J. Eisenreich ted.], Ann Arbor, MI, Ann Arbor Sci.  Publ.  Inc., Chapter 20,
p. 409-421.

Patchineelam, S.R. (1975).
Untersuchungen  liber die  Hauptbindungsarten  und  die  Mobilisierbarkeit von
Schwermetallen in fluviatilen Sedimenten.  Thesis, Univ. Heidelberg,  137 pp.

Patchineelam, S.R. and U. Forstner  (1977).
Bindungsformen von  Schwermetallen  in marinen Sedimenten.  Untersuchungen an
einem Sedimentkern ans  der  Deutschen Bucht.   Senckenbergianda marit. J9: 75-
104.

Rapin, R., R. Carignan, A. Tessier  and P.G.C. Campbell  (1984).
Unpublished data.

Rapin, R. and U. Forstner (1983).
Sequential  leaching  techniques  for  particulate  metal  speciation:   the
selectivity of  various  extractants.  4th Int.  Conf.  on Heavy Metals in the
Environment, Heidelberg, Proceedings p.  1074-1U77.

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                                                                            256
Reuther, R., J.B. Anderson and U. Forstner  (1983).
Effect of pH-changes  on  the  distribution and chemical forms of  heavy  metals
in sediment cores from Swedish lakes.  4th  Int. Conf. on Heavy Metals  in  the
Environment, Heidelberg, Proceedings p.  868-871.

Reuther, R., R.F. Wright and U. Forstner  (1981).
Distribution and  chemical  forms  of heavy metals  in sediment cores from  two
Norwegian lakes  affected by  acid precipitation.   3rd  Int. Conf.  on Heavy
Metals in the Environment, Amsterdam, Proceedings p.  318-321.

Schwertmann, U. (1964).
Differenzierung  der  Eisenoxide  des  Bodens  durch  photochemische Extraktion
mit  sauerer Ammoniumoxalat-Losung.   Z.  Pflanzenernahr.    Dung.   Bodenkde,
105:  194-202.

Stover, R.C., L.E. Sommers and D.J. Silviera (1976).
Evaluation of metals in wastewater sludges.  J. Water Pollut. Cont. Fed.  48:
2165-2175.

Tessier, A., P.G.C.  Campbell, J.C. Auclair, M. Bisson and H. Boucher (1982).
Evaluation  de  1'impact  de  rejets miniers  sur des  organismes  biologiques.
Universite du Quebec, INRS-Eau, rapport  scientifique  No 146, 257 p.

Tessier, A., P.G.C.  Campbell  and M. Bisson  (1980).
Trace  metal  speciation  in  the  Yamaska  and  St.  Francois  Rivers  (Quebec).
Can.  J. Earth Sci. 17: 90-105.

Tessier, A., P.G.C.  Campbell  and M. Bisson  (1979).
Sequential  extraction procedure  for  the  speciation of  particulate  trace
metals.  Anal.  Chem. 51_:  844-851.

Viel, M., G.P.  Nembrini,  J.  Dominik and J.P. Vernet  (1983).
Vertical  distribution and   chemical  speciation  of  heavy  metals  in Lago
Maggiore  sediments  (North Italy).   4th  Int.  Conf.  on Heavy Metals  in  the
Environment, Heidelberg,  Proceedings p.  793-796.

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                                                                            257
Volkov, I.I. and L.S. Fomina (1974).
Influence  of  organic  material  and  processes  of  sulfide  formation  on
distribution of  some trace  elements in  deep-water sediments of  the Black
Sea.  Am. Ass.  Pet. Geol. Mem. 20: 456-476.

White, J.R. (1984).
Trace  metal  cycling  in  a  dilute acidic  lake system.   PhD  Thesis, Dept.
Civil Engineering, Syracuse University, 261 pp.

-------
                                                                           258
      MO
     4*0.
      MO
     y
      •o
                            Q
                                 ©
                                                       1 -
                                                       /L^tT-.
                         c»
                                                 III
     VIO
    I 310
    6
                                                            ®
                                                  TI
FIGURE 1.  Effects of  sample  pre-treatment on metal partitioning in an
           anoxic sediment  (a)  fraction I  (exchangeable at pH 7, MgCK);
           (b) fraction  II  (carbonate and  exchangeable at pH 5, NaOAc/HOAc)
           Sample treatments:   fresh; wet  storage, 4°C, 20 d; freezing;
           dried  under  N,
20 C; dried in air,
    4'
105°C
  20
freeze-dried.

-------
                                                                               259
       210
          Pb
            8.6
            1.9
            2.1
Pb
   32
   21
                       130
    20
Zn
   145
                                   60
               410
    65
Cu
                                                 62
                             20
                                                185
      32
              625 0-1 cm


            <
            >
            UJ 625 75-80 cm




              527 2-3cm
                                                       UJ
                                                       O
                                                       UJ
                                                       ** 527 31-33 cm
                                    m     nr
           I-  adsorbed  and exchangeable at pH 7;  II-carbonate
           and  exchangeable at pll 5; I 1 I - reducib le;  IV-orqanic

           matter  and  sulphides; V-residual
FIGURE  2.   Partitioning of  Cu,  Zn, Pb and  2l°Pb in two sediment cores from
            circumneutral  lake Geneva.   (From Dominik et al..  1983).

-------
       JO      00
           —^-XvX-X-X-X-l i • IV.',:; : t'f-
           .. Jx-XvX-XvX-x-x-x-x-^/
            •x-x-x-xvXvx-Xx-x-x^
                      Zn
       •*-.-.•.-.•.'.•.'.'I '**•*'
                             0
                                                                                         zoo  IppmJ
                                                                        MOO
                100   200   300 PPB
                    Zinc
                    (0-20)
      Exchangeable pH 7
I JZ2 Carbonates  •*• exchangeable  pH 5
      Fe-Mn oxides
      Organic matter + sulfides
      Residual  fraction
FIGURE  3.   Partitioning of  Zn  in sediment cores  from (a) lake  Hovvatn (pH 4.6)  - from Reuther  et
            al.  (1981); (b)  lake Gardsjon (pH  4.7)  - from Reuther et al.  (1983);  (c) Clear-water
            Take (pH 4.65) - from Rapin et al.  (1984); (d) lago MaggTore (circumneutral) - from
            Viel et al. (1983).
                                                                                                                ro
                                                                                                                en
                                                                                                                o

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                                                                       261
Table 1:  Possible approaches for the determination of metal
          partitioning in sediments.
          o   mathematical modelling

                  thermodynamic equilibrium calculations

          •   experimental manipulation

                  physical separation:    grain size
                                          specific gravity
                                          magnetic properties

                  chemical separation:    selective extractions

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                                                                       262
Table 2:  Methods for the extraction  of  metals  from  major  chemical
          phases in sediments  (examples).  After  Forstner  (1982),  with
          modification.
  BaCl2-triethanolamine  (pH 8.1)
  MgCl2
  ammonium acetate (pH 7)
£ajrbonate jahases
  C02-treatment of suspension
  acidic cation exchanger
  NaOAc/HOAc-buffer (pH  5)
redii£ib]e_ j>hases (in approximate order
                  of release of iron)
  acidified hydroxylamine  (+ 0.01 M HN03)
  ammonium oxalate buffer
  hydroxylamine-acetic acid
  dithionite-citrate buffer
or£aji i£ f_ra_ct i on (i nc 1.  s u 1 f i de s)
  H202-NH1+OAc (pH 2.5)
  H202-HN03
  organic solvents
  0.1 M NaOH/H2S01+
  Na-hypochlorite
  Na-pyrophosphate
  diethylenetriaminepentaacetic acid
  (DTPA) - NaOAc (pH 7)
Jackson (1958)
Gibbs (1973)
Engler et al. (1977)

Patchineelam (1975)
Deurer et al. (1978)
Tessier et al.  (1979)
Chao (1972)
Schwertmann (1964)
Chester & Hughes  (1967)
Holmgren (1967)

Engler et al.  (1977)
Gupta & Chen (197b)
Cooper & Harris (1974)
Volkov & Fomina (1974)
Gibbs (1973)
Stover et al.  (1976)
Khalid et al.  (1981)

-------
Table 3:   Examples of sequential extraction procedures  .
                                                                            263
  step    method # 1
                         method # 2
                    method # 3     method # 4
           MgCl
                         NH^OAc
                    NH..OAC       NH2OH.HC1/HN03
II
           NaOAc/HOAc
III      NH2OH.HCl/HOAc
NH2OH.HC1/HN03      NH2OH.HC1    NH2OH.HCl/HOAc
                                                H202/HN03
IV      H202/HN03
                            H202/HN03
                                     f/HCl/HN03
           HF/HCIO
                         HN0
                    HF/HN03      HF/HN03
(a) method 1 =  Tessier et al. (1979); method 2 = Forstner (1982); method 3
    =  Engler etal. (1977); method 4 = Chao & Theobald (1976).

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                                                                       264
Table 4:   Possible approaches for the evaluation  of extraction
           selectivity
        use of pure solids

        o   alone
        •   in model sediments
        o   spiked into natural sediments

        analysis of extracts and/or residual sediment for
        various "complementary" parameters

        •   organic C
        *   inorganic C
        o   total  S
        »   acid volatile sulfide
        o   Al, Si

        successive extractions with same reagent

-------
                                                                       265
Table 5:  Extraction of sulfur and organic carbon from marine (A) and
          freshwater (B) sediments. After Rapin & Forstner (1983); see
          text for description of steps I- V.
                                                          B

% in sed.
Step I
II
III
IV
V
S
0.09%

10%
—
90%
___
C org
4.3 %

—
—
77%
23%

% in sed.
Step I
II
III
IV
V
S
0.6 %
17%
13%
20%
42%
8%
C org
2.7 %

—
—
85%
15%

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                                                                      266
Table 6:  Evaluation of the effects of sample pre-treatment on
          metal partitioning (INRS-1).
              metals   :    Co Cu M1 Pb Zn; Fe Mn

              extractants: MgCl2
                           NaOAc/HOAc
                           NH2OH-HCl/HOAc
                           H202/HN03
              sediments:   lake Aylmer (oxic)
                           lake Magog (anoxic)
              preservation: wet storage, 4°C (20d)
              methods       freezing
                            freeze-drying
                            drying, N2, 20°C
                            drying, air, 105 °C

-------
                                                                       267
Table 7:  Evaluation of the effects of sample pre-treatment on
          metal partitioning (INRS-2).
           metals:

           extractants:
           sediments:
           comparison:
Cd Co Cr Cu Ni Pb Zn; Fe Mn

MgCl2
NaOAc/HOAc
NH2OH-HCl/HOAc
H202/HN03
lake Aylmer (anoxic)
lake Nepahwin (anoxic)

with/without N2 atmosphere
for extractions 1 •»• 3

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                                                                       268
Table 8:  Fate of acid volatile sulfides during the extraction
          procedure - influence of adventitious oxygen.

                          lake Aylmer         lake Nepahwin
                      (1.8 x 10-6 mole/g)    (29 x 1Q"6 mole/g)
  fresh sediment             (100%)                (100%)
  lyophilized                  33                     2
  air-dried                    11                     1

  with N2 atmosphere
  step      I                  97%                   89%
            II                 97                    87
            III              <  5                     1

  without N2 atmosphere

  step      I                  38%                   11%
            II                 20                     1
            III              <  5                     0

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                                                                      269
Table 9:  Influence of adventitious oxygen on the partitioning of iron
          in an anoxic sediment (lake Nepahwin).
iron concentration (10-6 mole/g)
fraction
I
II
III
IV
with N2
19.0 ± 0.6
123.6 ± 2.1
119.3 ± 0.6
13.1 ± 1.0
without Np
2.7 ± 0.2
47.3 ± 2.8
176.5 -t 3.2
10.3 ± 1.0
a
- 16.3
- 76.4
+ 57.1
- 2.8
                      246.5  ±  5.2   273.1  ±  4.0   + 29.7
                      521.5  ±  5.7   509.9  ±  5.8   - 11.6

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                                                                       270
Table 10:  Influence of adventitious oxygen on the partitioning of lead
           in an anoxic sediment (lake Nepahwin).
lead concentration (10-9 mole/g)
fraction with N2
I 0.1 ± 0.01
II 99.9 ± 6.3
III 1071.5 ± 74.8
IV 419.9 ± 28.0
V 154.4 ± 8.2
without Np
2.7 ± 0.2
502.0 ± 17.4
656.4 ± 66.1
337.9 ± 18.3
173.8 ± 11.6
A
+ 2.6
+ 402.1
- 415.1
- 82.0
+ 19.4
                    1747.2  ± 82.1    1674.8  ± 72.4   -  72.4

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                                                                       271
Table 11:  Influence of adventitious oxygen on the partitioning of lead
           in an anoxic sediment (lake Aylmer).
                         lead concentration (10~9 mole/g)

           fraction      with Np        without Np       A

               I        1.9  ±  0.1     2.4  ±0.2   +  0.5

              II      173.8  ± 12.1   117.3  ± 10.6   - 56.5

             III      168.9  ±  5.8   214.8  ± 12.1   + 45.9

              IV       43.9  ±  3.9    55.0  ±  6.3   + 11.1

               V       97.0  ±  1.9   102.3  ±  2.9   +  5.3


               Z      485.5  ± 14.0   491.8  ± 17.4   +  6.3

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                                                                               272
Table 12:  Influence of pH on the partitioning of sediment-bound metals.
  metal   A pH
   Cd
                    effect
relatively mobile; organic forms decreased as
 pH lowered; accompanying increase in dissolved
 and exchangeable forms; no significant changes
 in Cd associated with reducible fraction.
reference
   Zn
relatively mobile; dissolved and exchangeable
 Zn increased markedly as pH decreased;
 concomitant decrease in Zn associated with
 reducible fraction.
   Pb
immobile; little or no dissolved Pb detected
 at any pH; exchangeable forms increased under
 moderately acid conditions (pH 5.0); no
 significant changes in Pb associated with
 reducible fraction.
   Hg
immobile; little or no dissolved Hg detected at
 any pH; exchangeable Hg increased slightly
 under moderately acid, reduced (pH 5.0, -150mV)
 and weakly alkaline, oxidized (pH 8.0, +500mV)
 conditions.

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Table 13:  Determination of metal  partitioning  in  sediment  cores  (circumneutral lakes).
reference
Capobianco
& Mudroch
(1979)
Baiker, in
Forstner
(1982)
geographical
location
lake Ontario
lake Constance
dating preservation
no freeze-dried;
ground
yes ?
N2 strata
(cm)
no 1
(* 26)
? 2, 3
(+ 15)
metals
Fe Mn
Cr Cu
Ni Pb
Zn
Zn
extraction
procedure
0.5 N HC1, 20°
HC1/HN03, 90°
HF/HC1 0^03
BaCl2/EDTA
?
NH2OH»HC1
0.3 N HC1
Manning et al . lake Ontario
(1983) 	
Viel et al. lago Maggiore
(1983") 	
yes
yes
210pb
freeze-dried
freeze-dried
no 1
(* 10)
no 1,2
(+ 20)
Cd Co
Cr Cu
Ni Pb
Zn
Cd Cu
Pb Zn
                                                                                   MgCl,
                                                                                   NaOAc/HOAc
                                                                                   NH2OH»HCl/HOAc
                                                                                   H909/HNO,
                                                                                   HF/HC1
                                                                                   MgCl2
                                                                                   NaOAc/HOAc
                                                                                   NH2OH-HCl/HOAc
                                                                                   H262/HN03
                                                                                   HF/HC10U
Dominik
et al. (1983)
                   lake Geneva
 yes
210pb
freeze-dried
no     0-1     Cu Zn   NH^OAc
      31-33      Pb    NaOAc/HOAc
      75-80    210Pb   NH?OH»HCl/HOAc
               21°Po   H262/HN03
                       HNOo
                                                                                                              CO

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Table 14:  Determination of metal partitioning in sediment cores  (acid  lakes).
reference
Evans &
Parliament
(1983)


Reuther et al.
(1981)
Reuther et al.
(1983)
White (1984)

Ford (1984)
Rapin et al.
(1984)
geographical dating
location
Plastic lake yes


lake Hovvatn yes
lake Langtjern
lake Gardsjon ?
lake Stora Gal ten
lake Lysevatten
Dart lake yes

Cone Pond yes
South King Pond 210Pb
Clearwater lake
preservation N2
air- dried, no
80 °C; ground


air- dried; no
70 °C
air-dried; no
70 °c
wet storage, no
4°C (-> 6wk)

wet storage, no
?°C (3-12mo)
wet storage, yes
4°C (+ 7-lld)
strata metals
(cm)
2 Pb
(- 12)


1 Cd Co
(+ 20) Cu Ni
Pb Zn
1,2 Cd Pb
(- 20) Zn
Fe Mn
1,2,4 Pb Zn
(-- 20) Al
Fe Mn

1 Al
Fe Mn
1,2,4 Cd Cu
(> 20) Ni Pb
Zn
Fe Mn
extraction
procedure
MgCl,
NaOAc/HOAc
0?3l5 HC13
HC1/HN03
(non-sequential )
NH^OAc
NH,OH'HC1/HN03
(NH^ )oC2Oj.
H202/HN03
HR03
NH.OAc
NH.OH.HC1/HNO,
(NHJ-C-O,,
H202/RN03
HR03
MgCl2
NH2Ofl.HCl/HOAc
H202/HN03
HN03
H202/HC1
NaOH
LiB02
MgCl2
NaOAc.HOAc
NH2OH-HC1
NH9OH.RCl/HOAc
                                                                                            p
                                                                                          F/RC10
                                                                                                              [\3

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                                                                           275
                              DIATOM ANALYSIS

                                     by

                            Richard W. Battarbee
                            Pa IaeoecoIogy Research Unit
                            Department of Geography
                            University College London
                            26 Bedford Way
                            London WCIH GAP
Introduction

     I  would like to start by thanking Steve for Inviting me and also by

thanking the EPA for funding the workshop and providing us with excellent

accommodatIons.

     First,  I  want to Introduce you to diatoms because I  think that a

number of people here are not particularly familiar with diatoms and diatom

analysis.  I shall then talk about the history and some of the problems of

diatom pH reconstruction.  Finally, I  will suggest some other things that

we should be doing with diatom analysis.

Diatoms

     Figure I  shows SEM pictures of two common acid diatoms, label I aria

quadrIseptata and T. blnalIs.  Diatoms are unicellular algae.  They are

particularly Interesting to palaeolImnologlsts because they have slllclous

cell walls and therefore tend to be well preserved In lake sediments.   In

the figure there are two complete cells.  The features we are Interested  In

for taxonomic purposes are the characteristics of the valves.  These valves

are connected by a series of girdle bands of various kinds and quantity,

although  In sediments It's likely that these various components of the

diatom cell  will be separated.  Diatoms grows In most wet or damp habitats.

They are, of course, particularly common  In rivers, lakes, estuaries and

the oceans.  In  lacustrine environments many people think mainly  In terms

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                                                                        276
of plankton Ic diatoms, the ones that grow In the open water more or  less
free floating and completing most of their life cycle In the water column.
However, especially In acid lakes, we are also concerned with pertphytlc
species, those that grow around the edges of a lake associated with various
kinds of substrates, on plants, the eplphyton, on sand, the eplpsammon, on
stones, the eplllthon, and on mud, the eplpelon.  There Is a lot of overlap
between the species found  In these habitats.  We might expect that almost
all surfaces situated above the photic limits In a lake will have a fairly
dense cover of diatoms.  These are the communities, as well as the plankton
communities, that contribute diatoms to the sediment.  In addition we must
not forget that diatoms can come from outside the lake, from lakes
upstream, from streams, and In fact there may be diatoms associated with
soils  in the catchment.  All of these can come Into the sediment often
going completely unrecognized.  It Is a possible source of error that has
to be considered in some situations.
pH Reconstruction
     Diatoms respond very  strongly to water quality.  In fresh water,
especially mesotrophic and oligotrophic fresh waters, pH or hydrogen  Ion
activity, or more probably factors correlated with hydrogen Ion activity,
have a strong influence on the composition of diatom communities.  The
starting point in most diatom pH studies Is Hustedt's classic monograph on
the diatoms of Java, Ball  and Sumatra (Hustedt 1937-39).  He Introduced a
number of terms describing groups of diatoms  In relation to pH
     (I)  AlkalIbiontic:   occurring at pH values > 7;
     (2)  alkalIphilous:   occurring at pH about 7 with widest distributions
          at pH > 7;
     (3)   indifferent:  equal occurrences on  both sides of pH 7;
     (4)  acidophilous:  occurring at pH about 7 with widest distribution

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                                                                        277



          at pH < 7;



     (5)  acldobiontlc:  occurring at pH values < 1, optimum distribution



          at pH = 5.5 and under.



     That was the beginning and nothing much really happened for quite a



while until the Danish algologlst Nygaard In 1956 tried to quantify the



Hustedt scheme by producing three Indices:



     Index a = (acid units)/(alkalIne units);



     Index co = (acid unlts)/(number of acid species);



     Index e = (alkaline unlts)/(number of alkaline species).



Indexu) and Index e have not really been used very much because they seem



to produce variable results.  They are dependent on the number of species



Identified, taxonomtc conventions that vary between workers and the number



of Individuals that are counted In any sample.  Consequently, they are not



very good.  But Index a has been used and Is still being used by dlatomists



today as a way of reconstructing pH.  The Index calculation produces a



number which can be correlated with measured pH and this can be used to



calculate a linear regression equation to predict pH (Fig. 2).



     This  Introduces the problem of which pH measurement we use In such a



regression, how we measure pH, and what time of year the pH Is measured.



Should we  look for an average pH value, should we use a value for a



particular time of year, how many samples do we need for a lake that may



have fluctuating pH before we are happy that we can actually ascribe one pH



value to put  Into our equation?



     Jouko  Merilainen has addressed this problem with respect to Finnish



lakes.  By looking at the pH of 150 lakes through the seasons he showed how



in some cases the summer pH can be up to two units higher than the autumn



pH (Fig. 3).  He suggested that only pH measurements that were taken after



the overturn  In autumn should be used in calibration models.  That may be

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                                                                           278

fine in Scandinavia and may work well In dlmlctfc lakes but then many of


our lakes are holomlctic and there are seasonal variations In pH caused by


different factors, so It's still not entirely clear Just which pH value we


should use.  If we go back to the regressions we can see that Merllalnen


produced a very good relationship using the pH measured In autumn against


the log of the Nygaard Index.  However, ft has a certain deficiency, one


that Ingemar Renberg In particular was concerned with.  In very acid


conditions It may be that there are no alkaline diatoms at all, so the


denominator of the equation Is 0, producing scores of infinity.  To counter


this problem Renberg Included the percentages of the clrcumneutral taxa In


the equation and produced an index B:




                     %ind.+(5x
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                                                                        279
get away from this classification system by using the occurrences of
selected taxa In the data set as individual predictors of pH.  An example
Is shown In Fig. 6.  It has a good r value but the relationship Is not
quite as good as that given by the other systems.  There are ways of
Improving this by using various PCA methods which Involve the whole data
set.
     Davis and Anderson compared the various techniques of pH
reconstruction on a sediment profile from Speck Pond  In Maine (Fig. 7).
The diagram shows that whether we use the  Index system, the multiple
regression analysis of groups or the multiple regression analysis of
Individual  taxa the story Is similar although there seems to be more
variability with the latter.
     These are the various ways being used at the present time to
reconstruct pH and they allow diatomlsts.  If a good chronology Is
available,  to address a number of questions.  What  I  want to do very
briefly  Is to show you an example of this  In practice using some of our
work from Scotland.  The site is called Round Loch of Glenhead and  It has a
pH at the present time of about 4.7.  Figure 8 shows  a dated diatom
diagram.  In the  lower part of the diagram the percentages of the various
species  are quite stable, but at about  1600 AD there  Is a decline  In the
plankton, a feature which seems to be very common In  acidifying lakes at a
pH of about 5.5.   In this particular case one can see that  it Is quite
clearly  a pre-Industrial Revolution feature, so the cause is not associated
with acid deposition.  From about 1850  there Is very  clear evidence of
acidification with strong declines In circumneutral species, Increases  In
the percentages of the acidophilous species, and then strong Increases  In
the acldobiontic  species.  The data can be summarized by grouping the
species  Into the  various pH categories  and using a pH reconstruction

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                                                                        280
method, here Index B, to show likely pH change through time (Fig. 9).   It
appears that we have a drop of about I  pH unit since about 1850.  Our
predicted pH for the surface sediment Is about 4.7,  agreeing very nicely
with the measured pH that we have for this site which ranges between 4.5
and 5.
DI atoms and the Cause of Lake Acidification
     So we can begin to produce some Important Information about whether a
lake Is being acidified.  We can. If necessary, calculate the rate of
acidification through time If we translate pH  Into H  concentrations
and by doing more and more of these sites In different areas we can begin
to assess the extent of acidification.  However, by careful choice of sites
we can also begin to address the problem of the causes of acidification.
For example, in Britain one of the possible causes of aldlfication Is the
afforestation of our uplands.  Afforestation is usually the planting of
conifers In the uplands on acid moorland soils.  There are various ways
that such planting might cause acidification, we think, so to test the
hypothesis we chose sites that were afforested and compared them with
non-afforested sites.  We found that our most extreme examples of
acidification occurred  In catchments that had not been afforested and In
the two sites that had been afforested we found evidence of acidification
beginning a number of decades before the time of planting.
D i atoms and Acid If I cat I on HI story
     Last year  I reviewed the available literature to work out a chronology
of acidification (Table I).  So far there are only about 30 or 40 sites
which  have been worked on In this way so we do not have much to work with.
However, I suspect there are at  least two or three times that many sites
actually being worked up at the present time and the situation  is likely to
improve dramatically  In two to three years time.  The evidence presently

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                                                                        281
available from America, Norway and the UK suggests that the present
acidification problem  In those countries began In the nineteenth century
with the most rapid changes taking place since about 1930.  This Is
apparently counter to the view that acidification Is a problem of the last
20 or 30 years.  It Is clear from this that most documentary records, where
they exist at all, do not have the antiquity or reliability required to
determine the history of this problem.
ProbI ems of pH ReconstructI on - ExtrInsIc Factors
I.  Good pH reconstruction needs very large modern data sets.  These take a
long time to produce and they need to be of very high quality.  But how
valid Is It to amalgamate regional data sets to produce the large files
necessary?  Should we put all our data together to produce data sets that
are very useful statistically but by doing this we are bringing problems
associated with regional variations In ecology and distribution of the
various taxa.  I think  It Is better to try to work with smaller regional
data sets and only amalgamate after careful Inspection of the behavior of
the different species  In the various regions.
2.  Clearly a very important question In all this Is taxonomy and the
correct Identification of species.  There are plenty of obvious examples  In
the recent IIterature where mistakes have been made by poor taxonomy.
Correct identification  Is especially important where species of very
different ecology have  similar morphology as  in TabelI aria.   On a
different plane there are many very genuine taxonomlc difficulties, as with
all diatom analysis, mainly relating to the difficulty of the species
concept In diatoms and  form variability within species.
3.  Then again, there are problems relating to the lack of Information
about the ecology of many diatom species.  Some species are reasonably well
understood, they occur  frequently, In abundance, and we can see their

-------
                                                                        282
distribution In relation to a range of water quality parameters.  For many
species, however, especially the ones that are less common, we really don't
know which pH class to put them In or, If we look to the literature for
help,, we might find that the literature Is wrong or conflicting. In which
case we might arbitrarily choose the more conservative of two
posslblIItles.
4.  Perhaps one of the most worrying problems Is the artificiality of the
pH classification Itself.  Species ranges and optima are likely to follow a
continuum of values and many species may legitimately fall  between classes.
Consequently models that move away from the pH classification system should
certainly be encouraged.
ProbI ems of pH Reconstruct Ion - Intrinsic Factors
     We might expect to find some of variance associated with the
relationship between measured pH and predicted pH to be related to other
intrinsic factors i.e. beyond the control of the operator and the models
used.   There are many and I have suggested five.
I.  One problem  Is using diatoms as  Indicators of pH when their presence  Is
due to another or a combination of other factors.   I don't know of any
examples of this In acid system but  It Is clear that the same species can
occur  in different environments for different reasons.  For example,
Cyclotella meneghInlana Is correctly thought of as a halophllous species
since  it occurs  In saline lakes and brackish estuarlne conditions.   It also
occurs  In eutrophic lakes but It would be wrong to use it as an indicator
of salinity in this environment.   In an acid system It might be that
nutrient enrichment leads to the development of a flora that contains taxa
categorized at higher pHs although pH itself may not have changed.
2.  Another question which we are working on at the moment is the
relationship between the diatom assemblage and the sources of the diatom

-------
                                                                        283
assemblage.  It must not be forgotten that what we are doing Is relating pH
to a fossil assemblage that, we assume, fairly represents the contemporary
living communities In each lake.  In other words the relationship between
the point of accumulation, the point at which we take a core or surface
sediment sample, and the distribution of communities and micro-habitats Is
critical to the composition of the sediment assemblage and thereby to the
reconstructed pH within any particular lake system.  Some of our
preliminary data Indicate that there Is considerable spatial variability In
diatom communities within a lake.  pH reconstruction, for example, on a
range of II eplpsammlc and 17 eplllthlc habitats within the same  lake and
at the same time gives values from 3.7 to 5.3 and 3.7 to 5.0 respectively.
The mean of these values  Is close to the pH 4.7 value predicted from the
surface sediment assembalge so at this site our assumptions appear to be
fairly valid.  However, there has been so little work of this kind we must
continue to question these assumptions In many other situations.
3.  A related problem to this Is that of differential transport and
accumulation.  This  Is not just a problem of mlcrohabltat variability but
variability In the way In which the diatoms from those habitats are then
transported to the point of accumulation and the Influence of this on the
spatial pattern of accumulation of an  Individual taxon.  John Anderson, a
graduate student of mine, has looked at the spatial distribution of
planktonlc diatoms In the sediments of a eutrophic lake.  Figure  10 shows
variations between cores of one species, Stephanadlscus tenuis.  The trends
are very similar but the detailed patterns and the ranges of percentages
vary quite strongly and this would undoubtedly cause variations in pH
reconstruction.
4.  Another factor that hasn't really been considered In acid lakes is the
problem of breakage and dissolution.  While dissolution Is a very Important

-------
                                                                        284
problem in many alkaline and saline sites I  am not sure to what extent they
are a problem In acid lakes.  Our data suggests that diatoms are preserved
reasonably well, but If dissolution does occur and If It Is differential
between taxa It will cause problems In pH reconstruction.  What seems to be
more Important  In our Scottish sites Is breakage.  We have a lot of diatom
fragments and debris there that we cannot really Identify and we have to
hope that the diatoms that we count and Identify are In fact a
representative  sample of the ones that we can't.  But If there is
differential breakage, again there Is going to be a problem In
reconstruction.
5.  The final point  I would like to make Is about the Importance and
problems of allochthonous Inputs.  It may not be a problem in many sites
but in some of  our Scottish sites the catchments of the lakes have been
disturbed by afforestation processes involving deep ploughing to drain the
soil prior to planting.  These operations have been followed by severe soil
erosion.  We think considerable quantities of diatoms are comlnig In with
eroded material and causing problems In pH reconstruction.
Other Areas of  Ignorance
     There are  some problems with pH reconstruction, but, perhaps
surprisingly, it seems to be a good technique and  it does work quite well
In  lots of situations.  However, I  want to suggest that In all this kind of
work we do not  pay enough attention to understanding the dynamics of the
contemporary diatoms In these systems.  There are all sorts of questions
that we need to address ourselves to.  Not just what the pH of a lake was
and what are the error bars on that pH, but we need to know why these
changes have taken place, why do we lose the diatom plankton around the mid
5 pH, what happens to diatom productivity In acidifying lakes, what Is the
relationship between diatom and other primary producers, and can we, from

-------
                                                                        285
dfatom accumulation rates fn the sedlmens Infer anything about changing
production?  Also, does transparency Increase when lakes acidify and If so,
to what extent does that Influence habitats within the system, and could
some of the changes we observe be due to habitat change rather than changes
In water chemistry?  Why do we get this very marked change In diatoms at
low pH?  There has to be a very Important ecological  mechanism operating
across these particular gradients and we are not sure what It Is.   I would
like to see a lot more attention paid to these ecological questions as well
as to the statistical questions of pH reconstruction.
Recommendat1ons
     I.  Don't Ignore contemporary diatom populations.
     2.  Integrate palaeolImnologlcal research with  llmnologlcal research.
     3.  Monitor populations over a wide range of lakes  In relation to both
         lake and catchment variables.
     4.  Take advantage of manipulation experiments e.g. liming, to assess
         diatom responses.
     5.  Persuade ecophyslologlsts to consider core-derived hypotheses and
         questions.
     6.  Choose sites very carefully to answer specific questions.
     7.  Assess within basin variability.
     8.  Evaluate hypotheses by comparison with parallel data.
     9.  Take taxonomy very seriously.

-------
                                                                              286
-•z.C'S. llar-ia  auzar-issztata Knuds.
ia b-inal'is  (Hhr.)  Grun.
               Figure 1.  Two  acich'obiontic diatoms from Loch  Enoch.

-------
a
                index
                log index
                                                56789
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-------
                150 Lakes in Eastern Finland
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                      measured pH
                                              8
                                                           ro
                                                           10
                                                           o

-------
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                                                            8
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                                                                10

-------
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-------
                   Speck Pond
                                                            293
        0
              4.5
        8
       24
Inferred pH
       5.0

5.5
                                          ®
               Regression  based on :-
                     Taxa	•_  pH  Groups

                     •®	®'  L<>g«
FiLgJ_7   Comparison of downcore pH for Speck Pond,  New England, calculated from
       multiple regression analysis of taxa and pH groups, and from logjo a
       (from Davis & Anderson, unpublished manuscript).

-------
Diatom diagram for Round Loch of Glenhead, Galloway



15 -

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                            dates for Round Loch of  Glenhead, Galloway, Scotland (from Flower &  Battarbee  1983).
                                                                                                                ro
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-------
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Fig.
            pH groups and pH reconstruction (Index B) for diatoms from

            Round Loch of Glenhead, Galloway, Scotland.

-------
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-------
Table  1.   AC-IIHIII-AMON  HAIA  inn  I.AKI-.S  I:HOM  NORWAY. SWUII-N.  I'INI AMU.  iiu-  I  .S  A. ANM (!.\NAI>A
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-------
                                                                          298
                                Chrysophyceae

                                  John Smol

     It has been well documented that fossil diatoms can be very useful In
reconstructing lake water pH.  Nevertheless, a frequent complaint of
paleoltmnologlsts has always been that diatoms represent only one portion
of past algal communities, and that a clearer understanding of past lake
conditions could probably be achieved if different algal groups were used.
The Chrysophyceae represents such an algal group for a variety of reasons.
The Chrysophyeae are a very diverse group of algae with approximately  1,000
described species, the majority of which are flagellated and planktonlc.
They are found In a variety of habitats, but appear to be most abundant in
ollgotrophlc and acidic waters, where they may represent upwards of 90$ of
the primary production In some Canadian shield lakes.
     When I  discuss chrysophycen microfosslIs, I am referring to
chrysophycean cysts or statospores, and mallomonadacean scales.
     All chrysophyte species produce cysts  (=statospores), which Is a
resting and/or sexual stage.   In fact the formation of the statospore  Is a
characteristic feature of the Chrysophyceae, and the external morphology
appears to be species specific.  Statospores are formed endogenously by all
chrysophytes, but relatively little is known about them at this time.  What
we do know about statospores Is that a I I chrysophytes produce them, that
all statospores are siliceous  and therefore are well preserved lake
sediments, and that the statospores themselves seem to be species specific.
However, only a small portion  of statospores have been  linked to the algae
that produce them.   In fact, less than 5% of chrysophyte species have been
linked to their respective statospores.  This situation hasn't changed much

-------
                                                                          299
since 1956, when Nygaard, In his classic paper from Lake Gribso, recognized
the viability of chrysophycean statospores as a useful group of
mlcrofosslIs.  He recorded and Illustrated a variety of statospores from
his diatom slides.  Seventy seven morphotypes were described by Nygaard,
and he gave them temporary names under the genus Cysta and then a suitable
species name, usually of a descriptive nature.  Although this was a very
practical approach, Nygaard recognized Its short comings, as evidenced by
the fact that he compared himself to an ornithologist who was trying to
describe a bird fauna of an unexplored region with only the eggs at his
disposal for identification.  However, he did produce a stratigraphy and he
showed that there were changes In the statospore profiles.  That was almost
30 years ago, and we haven't progressed very much since that time.
However, recently the International Statospore Working Group (I.S.W.G.) has
been formed.  I would predict that In about  10 years most statospores will
be linked to the algae that produced them, as the I.S.W.G. is setting down
strict guidelines as to how to describe statospores.
     There is still a large amount of work to be done here besides
statospore taxonomy.  There is some evidence  In the  literature suggesting
that not all chrysophytes form a statospore every year and they may
overwinter In the vegetative state.  Research should be done on the stimuli
triggering encystment and the physiology of resting stage formation.  This
Is especially Important for acidification studies because very often
chrysohytes are abundant In acidified lakes.
     Much more progress has been achieved with the scaled chrysophytes, the
Mailomonadaceae, a very  Important family In the Chrysophyceae which
Includes such genera as Mailomonasp Synurar and Chrysosphaerella.  The
characteristic feature of the Mailomonadaceae Is that they are covered by
siliceous, species specific scales.  Until the 1950's, most taxonomlc work

-------
                                                                          300



on this family was based on the size and shape of the cells.  However, with



the advent of electronmicroscopy, it was demonstrated that this was an



inadequate way of describing the taxonomy of these organisms, and now the



entire taxonomy Is based on the morphology of the scales.  Each scale is



species specific.  Since these scales are siliceous, they have all the



necessary characteristics to be useful paleo indicators.  They are well



preserved and abundant in lake sediments, In fact they are sometimes more



common than diatoms (In some lakes It's not uncommon to have 200 scales per



diatom).  They can be prepared using the same techniques used for diatoms,



and they also appear to be ecologically diverse.  These scales were almost



totally ignored in paleolimnological  studies until I960 when three papers



were almost simultaneously published (Battarbee et a I., I960; Munce, 1980;



Smol, I960).  However, these early studies largely addressed the problem of



eutrophicatlon (Smol et a I., 1983).



     More recently, much of my research effort has been focussed on lake



acidification.  All of this work has been done in "conjunction with Don



Charles and Don Whitehead at Indiana University.  As has been discussed by



Rick Battarbee, diatoms are very useful for lake acidification studies,  but



unfortunately planktonic diatoms tend to be excluded In acidic waters of a



pH < 5.5.  Consequently, If only diatoms are used In paleo studies of



acidified lakes, one wouldn't be able to trace changes in the



phytoplankton.  In contrast, chrysophytes are almost exclusively



planktonic.   It would seem that if chrysophycean microfosslls could be



recorded in acidified lakes, we would get some Indication of changes In the



open water community.



     In order to better understand the ecological preferences of



mallomonadacean species, we have recently completed a survey of the



mallomonadacean assemblages from the surficlal  sediments of 38 well studied

-------
                                                                          301
lakes In the Adirondack Mountains (N.Y.) (Smol et al., I984a).  Reciprocal
averaging and cluster analyses Indicated that pH and factors correlated
with It (e.g., alkalinity) exerted the greatest Influence on
mallomonadacean assemblages.  However, some of the most striking
relationships could be seen when the relative abundance of Individual taxa
were expressed relative to the summer pH levels of the surface waters of
the 38 study sites (Figs. I  & 2).  Certain taxa appeared to be quite
specific In their pH preferences.  From this preliminary survey. It would
appear that taxa such as Mailomonas caudata and M. punctlfera , as we11 as
Synura splnosa appear to be circumnutral or even alkalI philous species,
whereas M. hamatar M^. hlndonlI. and S. macracantha appear to be
acldoblontlc.
     The next stage was to see If these assemblages could be used to infer
past pH levels from stratigraphlc analyses.  Deep Lake In the Adlrondacks
was chosen as an initial study site (Smol et al., I984b).  Fossil
mallomomadacean assembalges shifted abruptly  In the lakes recent sediments
from a clrcumneutral flora dominated by Mallomonas crass I squama, with
lesser amounts of M*. punctlferaf  to one dominated by acidobiontlc species
(i.e., M. hIndon11 and M. hamata).
     The results of the Deep Lake study have been confirmed by the study of
a variety of other  lakes  In the Adirondack Mountains (currently part of the
PIRLA project funded by the Electric Power Research Institute).  As an
additional example, data from Big Moose Lake are presented here (Fig. 3).
Recently, Charles (1984) described the diatom stratigraphy from this core.
As In the Deep lake study, a marked shift  In Mallomonadaceae occurred In
the mid-1940's with more acidobiontlc taxa Increasing In abundance.  An
analysis of the accumulation rates of scales  In the Big Moose core (Fig. 4)
Indicates that mallomonadacean populations Increased substantially during

-------
                                                                          302



the proposed period of acidification.  Quite possibly, the decreased



populations of planktonfc diatoms at this time (Charles, 1984) resulted In



a less competitive environment for the planktonlc chrysophytes.



     Chrysophycean microfossils still represent a relatively unexplored



group of pa IeoIndicators; however, I  believe that these preliminary studies



Indicate that future Investigations are clearly justified.  Further studies



on the physiological ecology of chrysophytes will be required to refine the



predictive value of these microfossils.  Continued surveys of



mallomonadacean distributions should elucidate these relationships, but



laboratory studies on chrysophyte physiology and the monitoring of



chrysophyte populations  In manipulated lakes should be undertaken.  In



addition, taxonomic research on statospores will eventually allow the



Inclusion of all chrysophyte species In the Interpretation of lake



hIstorIes.

-------
                                                                     303
                               REFERENCES
Battarbee, R.W., G. Cronberg, and S. Lowry.  I960.  Observations on
          the occurrence of scales and bristles of Mailomonas spp.
          (Chrysophyceae) In the micro-laminated sediments of a small
          lake  In Finnish North Karelia.  Hydroblologla 71:  225-232.

Charles 0.  1984.  Recent pH history of Big Moose Lake (Adirondack
          Mountains, New York, USA) Inferred from sediment diatom
          assemblages.  Verh. Internat. veretn Llmnol. 22: (In press).

Munch, C.S.  I960.  Fossil diatoms and scales of Chrysophyceae In the
          recent history of Hall lake, Washington.  Freshw. BIol. 10:
          61-66.

Nygaard, G.  1985.  Ancient and recent flora of diatoms and
          Chrysophyceae in Lake Grlbso.  Folia llmnol. scand. 8:
          32-262.

Smol, J.P.  1980.  fossil synuracean (Chrysophyceae) scales In lake
          sediments:  a new group of pa IeoIndicators.  Can. J. Bot.
          58: 458-465.

Smol, J.P.  1985 (In preparation).  Chrysophycean mlcrofosslIs as
          Indicators of lake water pH.  To be published in Smol, J.P.
          etal. (Eds.).  Diatoms and Lake Acidity.   Dr. J.V. Junk
          Publishers, The Hague.

Smol, J.P., S.R. Brown, and R.N. McNeely.  1981.  Cultural
          disturbances and trophic history of a small meromlctlc lake
          from central Canada.  Hydrobiologla 103:   125-130.

Smol, J.P., D.F. Charles, and D.R. Whitehead.  I984a.  Mailomonadacean
          (Chrysophyceae) assemblages and their relationships with
          limnologlcal characteristics in 38 Adirondack (New York)
          lakes.  Can. J. Bot.  62:  911-923.

Smol, J.P., O.F. Charles, and D.R. Whitehead.  I984b.  Mailomonadacean
          mlcrofosslIs provide evidence of recent lake acidification.
          Nature 307:  628-630.

-------
   1.   The percentage contribution of selected Ivlallomonas scales plotted
   relative to the summer pH values for the Adirondack study lakes
   (from Smol 1985).
7.
100
50
0-
/
50-
o-
4
20-
1 100
M. crassisquama
& pseudocoronata
• •
•
.. ' V. 50
: •
• .
• • • .
.••
. .
»
M. acaroides

•
• •
•
• • *
>l 	 ' 1 	 | 	 1 	 1 	 1 	 1 	 1 	 1 OT 	 i***f« 	 1 	 i 	 1 	 T***T 	 *~i
i 5 6 7 8 45678
P H pH
•
* 50 -
M.hamata M. hindonii
*
: . v. .
•:•
.... . • ." • * • * *'t:;.\. f. : o-
5678 4
PH
20-j
M. caudata .
• •.!•••• f*
» -••••
..r— :. r •••-. /• .
45678 4
pH
•
. *..
	 • 1 • «1-M .f . 	 1 . lf..M^..M, lf .1 t
5678
PH
M. punctifera
. •
. ••••
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-------
Figure 2.  The percentage contribution of  selected Gynura scales  plotted

       relative  to  the summer pH values  for  the Adirondack study  lakes

       (from Smol  1985).
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                          Big    Moose   Lake
Figure 3-  The relative frequency of mallomonadacean scales in the recent sediments of
      Big Moose Lake.  The Pb-210 dates were provided courtesy of Dr. S. Norton and
      Ms. Geneva Blake of the University of Maine at Orono, Dept. of Geological
      Sciences.
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-------
                                                          307
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Figure 4-.  The accumulation rates of mallomonadacean scales in
      the recent sediments of Big Moose Lake.

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                                                                     308
                               Cladocera


                            David F. Brakke

     I  thank Steve Norton for getting this workshop organized and for
putting me on the program at about the time that I  would normally be
driving to work so that I'm at least half awake.  Rick Battarbee
summarized many things that apply to most groups of organisms.  In
addition to diatoms, his discussion applies to the Cladocera, and to
many of the other Invertebrates that I  shall discuss.  I will start
out with some slides to show you the kind of organisms I will talk
about,  because more people know about diatoms, I think, than know
about cladocerans.
     Here is one cladoceran.  It Is a very large one, certainly large
enough to handle a few diatoms.  It is a littoral zone cladoceran.  It
lives in the shallow areas of the lake, in the weed beds and the mud.
This is an Intact organism.  It Is not planktonic,  so we are talking
about a totally different set of organisms, than is In the littoral
zone.  Cladocerans reproduce mainly by parthenogenesis.  They make
xerox copies of themselves.  There Is a sexual phase, which usually
occurs in the fall, with males and gamogenetic females being produced.
They produce resting eggs, which are saddle shaped resting structures
called ephippia.  These structures, for some of the cladocerans are
the only structures that remain in the sediments.  For example, almost
all of the other parts of Daphnla will  disappear.  The parthogenetic
females do not  leave any remains; the males may  leave clasping hooks,
but the ephippia will remain In the sediments.  These can be
Identified at least for certain species.

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                                                                     309
     In lake sediments, a cladoceran will be disarticulated.  They are
not siliceous as are diatoms; they are made of chitln.  Chit I nous
structures do preserve very well, but there Is differential
preservation.  Not all groups of the cladocerans preserve equally
well.  In fact, many of the cladocerans are completely eliminated
except for very small parts.  This Is also true for other planktonlc
groups, such as the copepods.
     This Is another of the  littoral zone cladocerans.  You can
determine very easily the species from Individual parts.  A few little
pollen grains on the slide show the rough size of the parts.  Other
parts of the organism that are preserved, In addition to the shell,
are the post-abdomen and the post-abdominal claw.  These one can also
differentiate.  One can tell the species by nearly any one of the
parts that are recovered from the sediments.  This is the reverse side
of one of the cladocerans which  live primarily In the mud.  The parts
that preserve normally are the headshield, shell, the post-abdomen,
and post-abdominal claw.  Most of the other parts disappear.  To
reiterate, the parts are species specific.
     A totally different kind of cladoceran would be these  little
elephant-like forms.  This  Is Bosmlna. which Is normally a
euplanktonlc form.  Most of  Its population Is probably off shore In
the center of the lake; but there are also very  large littoral
populations.  It  Is from a different family than the  littoral  chydorld
cladocera, but very  Important In oligotrophic lakes.  In contrast to
Daphnlar Bosmlna preserves very well.  Wolfgang Hofmann Is one of the
few people In the world who can handle them taxonomlcally.  They are
rather variable morphologically, and they are very common  In
oligotrophic lakes and in acidic lakes.

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                                                                     310
     Returning to Daphlna. I  will  give you some examples where It may
be preserved.  Sometimes the claws preserve very well and are very
useful;  the ephlppla preserve well.  Cladocerans have been used for
Inferring a variety of things about changes In lakes.  They have been
used very successfully to reconstruct the eutrophlcatlon history of
lakes.  For example, Saint Clair Lake in Northwestern Minnesota was
enriched when a sewage plant was hooked up to a series of lakes, and
started spilling phosphorous downstream.  After 1870, with excessive
phosphorous loading, essentially the whole community became dominated
by one species, Chydorus sphaericus.  The lake had a number of species
and ended up with many fewer, with the community essentially dominated
by Chydorus.  There are very good relationships between primary
production In a lake and the species diversity of cladocerans.  The
greater the production In the lake, the lower the species diversity of
cladocerans.  The community becomes simpler and is dominated by a
single form or just a few forms, usually Chydorus sphaericus.
     There have been some surface sediments that have been studied for
cladocerans in similar fashion to diatoms (Figure I).  They show
variations with respect to a pH gradient, just as do the diatoms.
They are not as powerful, but if you put up some New England surface
sediment samples for cladocerans you would see these butterfly
diagrams of percent composition vs. depth.  Some species occur at
higher pH's and never to any great abundance; some occur throughout a
profile and you cannot say very much about them at all.  If you do a
cluster analysis of surface sediment samples, you do find some
groupings of  lakes that tend to have lower pH's and groupings of those
that have generally higher pH's, although there are other important
variables (Figure 2).

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                                                                     311
     Elevation has an Influence on these cladoceran communities; they
may be much more complicated In terms of their response to pH than
diatoms.  They are Influenced by many more factors.  Some of the
cladocerans have a greater abundance at higher pH and their decline In
sediment Implies that the lake water pH may be going down.
Essentially, It Is confirmatory evidence for a pattern that might have
been Inferred on the basts of diatoms.  There are some species that
seem to have constant relative abundance with pH and some like
Chydorus sphaerlcus that are either more abundant at higher pH's In
eutrophic lakes or more abundant In the acidic lakes.  This species
group may be a rather Interesting one, because once  It Increases with
either  Increasing or decreasing pH It really does tell you something.
It may tell you that the lake has either moved into a eutrophic phase
or that It has been acidified.  We have categorized these various
species In terms of pH group and also an altitude group (Figure  3).
There are still more than a few question marks, and  In some cases an
Inadequacy of enough material to classify a taxon.  Some very abundant
taxa occur but there are other taxa that you see at very  low
frequencies.
     Does this have any correlation with other data?  From some work
in Norway by Hobaek and Raddum, which Includes some of the lakes that
Steve Norton and Ron Davis have sampled, there are differences between
so called acidic lakes, humic  lakes, and less acidic  lakes in terms of
the number of species present.  The number of species may be something
that Is useful.  If a lake moves from a pH of 5.5 to a lower value,
you might assume that some of the species are being  lost.  This Is
particularly true for the cladocerans, but apparently less true for
the copepods and the rotifers about which we know  little.  But species

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                                                                     312
number looks like something that we might be able to use, at least for
the cladocerans.  The copepods leave few resting structures so It Is
one part of the plankton that we really cannot say much about In terms
of changes related to acidification.
     Will we ever get to these kinds of equations relating pH and taxa
for the cladocerans?  I  frankly doubt It.  One of the main reasons Is
that there are many more factors,that begin to shape cladoceran
communities than Influence diatom communities.  The cladocerans,
however, do respond to pH.  The number of species and diversity for
New England surface sediments appears to decrease with a decrease In
lake water pH (Figure 4).  There Is certainly variability, but there's
a general trend from more than 20 different species to less than 5 In
the more acidic lakes.
     Some of the species of copepods occur across a transect of pH in
Norway.  But some of the other species are only found In the more
acidic lakes and not In the higher pH lakes.  With the cladocerans
there  Is one group that occurs only In the higher pH lakes.  As the pH
goes down, those organisms are eliminated.  The Bosmlna complex which
Is a very diverse group, apparently occurs across the entire pH
gradient.  There may be a lot of information to be gained from this
group and no one has really looked at it.  I think there Is a lot of
controlled variability that might be expressed and quantified.
     There are a number of other areas for which this pattern has also
been observed.  If you  look at the Sudbury area or the LaCloche
Mountain area in Ontario, In areas where the pH is greater than 5,
Daphnia occurs.  When pH is less than 5, there are no Daphnia.
Daphnia at deeper  levels In the sediments but not In surfIcla I
sediments may be an indication that the pH has gone down.  This may

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                                                                     313




not tell us exactly what that pH level  was, but In most lakes with a



pH that Is 5.7 or 5.9 Daphnla will  be present In the population.  If



It disappears that may tell us something.



     Let's get back to some of the variation that occurs In some of



these communities.  Figure 5 shows the distribution of chydorld



cladocerans in a number of surface sediment samples In Norway against



elevation above sea  level  In meters.  As elevation Increases, Chydorus



starts to dominate the community.  That  Is also evidenced by a plot of



diversity against relative abundance of Chydorus.  When Chydorus Is



very abundant (>60$) the diversity Is very low.  When Chydorus



abundance Is  low, diversity Is much higher (Figure 6).  And again this



can occur on either end of the pH gradient.  There are also



Interactions between various species that you have to begin to tease



apart.  For example, when Alonopsls elongata Is abundant, AI one I la



nanaf which Is another very common species. Is almost not there



(Figure 7).



     What happens In terms of changes over time?  This Is the history



of Speck Pond based on Ron Davis' diatom data; they Indicate when a



change  in pH occurred.  These are the metal increases based on Steve



Norton's data.  The cladocerans did not give a clear pattern of



change, and In fact  Indicated that other disturbances had occurred in



the  lake (Figure 8).  A cluster analysis of these same data  Indicated



that there was a difference between the surfIcla I sediments and those



deeper  in the core  (Figure 9).  The cladocerans seem to indicate that



the  lake has changed.   In this  lake, also, Daphn ia did occur at depth



In the  core in fair  abundance.   Daphinla did, however, disappear from



the  lake, presumably as pH declined.  The cluster analysis and



disappearance of Daphlnla confirm the  Inference based on the diatoms

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                                                                     314
(Figure 10).
     Here Is another example from Ledge Pond In Maine.  The littoral
zone cladocerans, Indicate that the lake water pH had decreased.  They
showed the same pattern of surface sediments analyzed across a pH
gradient (Figure II).  This Included a decrease In the number of
species In the upper-most sediments, perhaps related to acidification
or a decrease In pH.
     In another lake In Norway this same patterns occurs.  One of the
species occurs primarily In higher pH lakes; there Is a very clear and
marked decrease In that taxon towards the surface (Figure 12).  Some
Individual taxa have a more direct relationship with pH than others.
Alonopsisf which we would have predicted on the basis of the surface
sediment relationships to be more abundant In the acid lakes,
Increases up core.  What did the diatoms Indicate for this lake?  The
acidibiontic taxa Increased to the surface, so It looks as though
there was a decrease In pH in this lake.
     Disturbances In the watershed are reflected in the cladoceran
community.  This small lake had some logging activity In It.  It looks
as though the community Is relatively the same through a period of
time, and then there was a (sediment) Interval, here, when this more
alkaline-loving taxon Increased.  The lake has returned to some kind
of condition that was similar to what It was before.  Perhaps effects
of logging changed the community, and It has now rebounded to Its
former condition.   It is important to keep In mind other watershed
perturbations.
     Many of these cladocerans living In the littoral zone are
dependent on the kinds of aquatic plants and associated communities
that are found there.  Kris Ken I an demonstrated that  lake water pH has

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                                                                     315



more of an Influence on the cladocerans  than does the distribution of



the macrophytes.  The pH-Is more important than the specific type of




macrophyte.



     One of the major problems In trying to use cladocerans to assess



acidification In lakes Is that the kinds of lakes that have been



examined.  In terms of being the most sensitive lakes, may be not very



good candidate  lakes to take a core for cladoceran analyses.  A lake



like this, which Is In Norway, may have very inorganic sediment; it



has very steep sides to  ft, very little littoral  zone development, and



there may be no way to get enough cladocerans, at least from the



littoral zone.  In the sediment to count.  There may be abundant



Bosmlnar but an Important part of the community may not be there.



Blavatn, a lake in the center of Norway, has only five or six species



present and In very low numbers.  In this case, you would have to use



enormous quantities of sediment to get enough taxa and Individuals to



work with.  There is a very practical limitation to doing cladoceran



analyses on some of lakes.  For some of the lakes that you would want



biological Information In addition to diatoms, It will not be



available.  In these cases, Bosmlna may be a very useful organism to



concentrate on.  I have mentioned the taxonomlc difficulties with that



group.  Bosmlna Is very abundant, even In some of the high altitude



lakes with very low sedimentation rates, little organic material, and



few chydorid cladocerans  in the sediments.  Whereas, Bosmina has not



been utilized In these cases, It may be something to work on.



      In summary, there are a number of factors that  Influence the



structure of cladoceran assemblages.  I have reviewed a number of the



more  important  factors In this talk and list several here (Figure 13).



     A final topic to mention Is the tremendous variation In terms of

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                                                                     316



size of cladocerans.  Cladocerans get eaten by vertebrate and



Invertebrate predators.  The size structure and species composition of



a cladoceran assemblage can change due strictly to predatlon.  For



example, If we look at a lake that you might call  non-acidified there



Is a significant forcing relationship between fish populations and the



size structure of the zooplankton.  Certainly, zooplankton graze



selectively, but they may not have as great an effect In terms of size



structure of diatoms.  A species of cladoceran may be exposed to a



vertebrate-predator dominated system.  But if fish are eliminated by



low pH/high Al, you may end up with only Invertebrate predators.  Fish



select different sized cladocerans, so they may force a change



selectively In the community.  Whether the cladocerans force some



significant change  In the phytoplankton Is open to question.  I  do not



think that  It  Is Important enough to cause significant variability In



dlatom/pH relationships.  And it may be In these acid lakes that as pH



goes down, as we get a change In the algal community, the cladoceran



community may also change, but there may be absolutely no causal



relationship between the two.  However, If the euplanktonic diatoms



and other algae begin to change from diatoms to something like



Mai lomonas,. this may Influence the grazers.  As far as I know no one



has really  looked at that.  We do know that if the grazer community



has been altered and we start putting phosphorous into the system, the



phytolankton undergo wild oscillations because this whole system Is



very unstable.



     We have a problems In using the cladocerans In the same ways that



we can the diatoms to  Infer pH changes.  But they do give us a window



through which we can look at other kinds of communities.  We need much



more experimental work aimed at understanding the dynamics of systems

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                                                                     317



with different predatJon regimes.  A disappearance of a key taxon may



tell us when fish were eliminated or when corIxIds became abundant,



but those Interactions are not well known.  The key concern related to



aquatic acidification Is the success of fish populations; the



cladocerans may tell us something of the history of changes In fish



populations, but only If we understand the relationships much better.



This Is a major area for further research on cladocerans  to



understand the acidification process.



     Clearly additional  sediment analyses are recommended.  This



applies to both surface sediments and cores.  The cladocerans do tell



a story that seems to be useful  In Interpreting acidification



histories.  The species relationships across pH gradients would



benefit greatly from more analyses than the relatively small number



that have been accomplished so far.  Some additional sediments are



available from the Adirondack Mountains of New York and Norway; these



should be examined.  Consideration should also be given to obtaining



larger cores from a few well-selected sites, where multiple parallel



measurements can be made, and where ancillary sediment data can be



gathered.

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                                                                               318
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                                                                               319
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                                                                               320
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Synerholm, C.C.   1979.   The Chydorld Cladocera from surface lake sediments In
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                           •*-,«'.!$•••.#•   .#•
                                                                                321
••1
              T
Fimirp 1      Relative abundances of the chydorid cladoceran taxa vs lakewater pH [3].
  9                                      (Brakke  et al.,  1984)
               ELEV. pH
               ( M)
               976
               880
               948
               837
               750
              I 123
               813
               803
               893
               I 13
              457
               78
               122
               I 17
               125
              469
               527
                                  LAKE
                                   NO.


4.65
e c

6.2
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                                                      16
                              0   2   4   6   8   10   12   14
                                       CHI-SQUARE  DISTANCE
                Figure 2
                              Cluster analysis of 18 lakes based on surface
                     sediment chydorid assemblages.

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                                                                                                          322
Figure  3
             Chydorid Cladoccra Recovered from New England Lake Surface Sediments*
  Species
  pH Group
Altitude Group
  Acroperus cf. harpae
  Alona affinis
  A. barbulata
  A. bicolor
  A. circumfibriata
  A. costata
  A. quttata
  A. intermedia
  A. quadranqularii
  A. rustica
  A. spp.
  Alonella excisa
  A. exiqua
  A. nana
  A. pulchella
  A. sp. #1
  Alonopsis spp.
  Anchistropus minor
  Camptocercus ntc rectiroaris
  Chydorus bicornutus
  C. faviformis
  C. gibbus
  C. piger
  C. sphaericus
  C. spp.
  Disparalona aaairostru
  D. rostrata
  Eurycercus (Bullatifrons) spp.
  Graptoleberis tatudinaria
  Kurzia latissima
  Leydigia leydigi
  Monospilus dispar
  Pleuroxus denticulaius
  P. procurvus
  P. striatus
  P. trigonellus
  Pseudochydonu globosus
  Rhynchotalona falcata
B?
B7
A?
BorD?
E?
B
B
B?
B

B?orC7
A?
A?
C?or B?
A
B
B
D

B?orC?
E?
A
A

A?
A?, B?. or C?
A
A?
C?
A
    e
    b?
    bore
    e
    b
    b
    a
    b
    b?
    c.'
    b?
    b?
    b?
    b
    core

    bore
    b
    c
    b?
        • A = grertest relative abundance at higher pH; B = uniform or variable relative abundance
  re pH; C = less frequent at both high and low pH values;  D = more frequent at both high and low
  pH values; E = greatest relative abundance at lower pH;  a = greatest relative  abundance  at lower
  altitude; b = uniform or variable relative abundance re altitude; c = less frequent at both high and
  low altitude; d = more frequent at both high  and low altitude; e = greatest relative abundance at
  higher altitude.

-------
          DIVERSITY (H'J

        2.0   2.8    3.6
          i
          a
 4.5  -
      6  10  14  18  22  26

    NUMBER OF SPECIES  (S)
                           60-
                           40-
                           20-
70
                                      Chydorus sphaericus
                                                    *  *  *+        *

422              775
          Elevation (m)
1128
Figure 4
       Numbers of chydorid species and
 Shannon-Weaver (H') diversity at each lake.

 (Brakke et al,, 1984)
                             Figure 5
                                                                                               CO
                                                                                               ro
                                                                                               CO

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  60-
8

-S40-
I
S20-
                                                         324
           Chydorus sphaericus
     1.19
                                    Figure 6
                   1.55
                                             **

                                             *
                            H1
1.90
2.25
   30-
 •21
 o
 £201
 
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                                                                               325
          SPECK  PONO
     »
   O }0
      _
l¥  I     !     H    »    I
  z  0
              !
Figure 8  Relative abundances of chydorid cladoceran taxa vs sediment depth in Speck
  Pond, Maine. The scale is in 10% intervals.

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                                                                             326
co
LU
_i
CL
2
<
CO
LJ
5
Q
LJ
CO
   0-0.5
  2.0-2.5
  8.0-8.5
  6.0-6.5
  4.0-4.5
  5.0-5.5
18.0-18.5
24.0-25.0
20.0-21.0
12.0-12.5
14.0-14.5
10.0-10.5
             02468
             CHI-SQUARE  DISTANCE
                                  Figure  9  cluster analysis of chy-
                                    dorid assemblages in 12 sediment lev-
                                    els from Speck Pond, Maine.
                  Dophnio/cm3
                  10          20
  E
  o
 CL
 LU
 O
                                         30
                                           Figure 10  Daphnia ephippia
                                              in sediment levels from Speck
                                              Pond.
                                       both figures from Brakke et al., 1984

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          DIVERSITY  (H')
  2.0    2.2     2.4    2.6    2.8
u

I
r-
Q-
UJ
Q

r-
Z
UJ
2
Q
in
10
15
25
   15    17    19    21    23    25
^Figure  11 Numbers of chydorid species
    NUMBER  OF  SPECIES   (S)  Ledge Pond core.
                                       and Shannon-Weaver diversity (H') for the
                                                    Figure 13 Factors Influencing the Structure of Cladoceran Communities

                                                        General Factors Influencing Cladoceran Communities
                                                          I. Lake morphometry
                                                          2. Latitude and elevation
                                                          3. Water  [2]  chemistry, esp. Ca, alkalinity
                                                          4. Lake nutrient status and algal productivity
                                                          1. Littoral zone development and macrophyte communities
                                                        Changes over Time Caused by
                                                          I. Watershed disturbances
                                                          2. Climatic change
                                                          3. Shifts in predation
                                                          4. Change in nutrient  regime
                                                          5. Atmospheric deposition of acids/metals
                                                            •  Watershed and lake titration of alkalinity, pH change
                                                            •  Elimination of fishes changing balance on invertebrate predation
                                                            •  Structural changes in the littoral zone
                                                            •  Alteration of food supply due to change in production/decomposition
                                                            •  Effects of metals  and  acids/metals
                                                          6. Various other types of pollution
                                                     Figures 11-13  from Brakke  et al.,  1984
                                     K)
                                            20  23
                                                             SNSF 31
                                                           Nedre molmesvotn
                                                             0      2O
                                                                             3O
                                                                                                      20
                                	 Alonoptli alongat*
                                ..... Aeropiruf fcorpat
                                	 Along off Inli
                           ^— Alone f uillco
                           	Alonalla ticlio
                           	 Alonallo nana
                                                                                            — Onrdorat iphatrlcui
                                                                                            	Ctiydorwi »lg«r
                                                                                            	 Curfccrui lamtllalut
                                                                                                                                                                               OJ
                                                                                                                                                                               f\>
              Figure 12
                    Chtngci in uleclcd chydorid Ctidoccri of Ncdre Mllm»vnn(SNSF .1.11. Norway. Chronology of pH chinir and heavy mrial
               deposiiion ii given in Fig. 6. 2 cm = 1963; 6 cm = 1917;  10 cm = 1877.

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                                                                 328
                      Invertebrates  in Sediments

                         Wolfgang Hofmann
  Ma ny thanks again for the  invitation  to  this wo r k s h o p.
  A drop of pH  in  lake water has various effects on the  lake
ecosystem and one  effect  is  a faunal succession due to  a
shift  towards  predominance  of species which are adapted  to
low pH or which are selected by secondary  effects of
acidification.  This is one point.
 Another point  is  if a strong correlation  between low pH  and
its faunal effects occurs for instance  indicated by the
existence of  indicator species.   In  this case the species  com-
position of an  assemblage may be indicative of a certain  pH  level
Such relationships provide the opportunity  to  follow faunal
changes by analysis of animal remains  in the sediment and  to
use faunal successions for reconstruction  of former pH
conditions. An  important  point is  to.check  if  such correlations
between the occurrence of certain  species  and  pH really
exist.

  I  wi I I now have  to discuss the use of "other
invertebrates"  as  indicators of  pH  conditions  and the use  of
their remains in  lake sediments  in  order to track the
process of acidification."Other   invertebrates" cover roughly
12 taxonomic groups (besides Cladocera) which  are
represented by  remains in the sediment  (Rhizopoda,
Gastropoda, Bivalvia,  Ostracoda,  Acari, Ephemeroptera,
Odonata, Megaloptera,  Heteroptera,  Coteoptera,
Trichoptera,Diptera)(s. Frey 1964). A  presentation
time of  35 minutes means  3 minutes  for each.
  In this situation, a concentration on a  certain taxon
seems inevitable.  The selection of  organisms which are  of
particular interest in this  respect  is based on three
criteria:
  1.Abundance:  The remains should  occur in  high abundance  in
the sediment  to get sufficient numbers of  specimens to
characterize  the  composition of   the assemblage. This is
particularly  important as the effect of acidification occurs
very near the sediment surface,  so  sampling distances and
sample volumes  are generally small.
  2. Positive indication  of  low pH:  that means that species
typical  of low  pH  should  be  present  in  the  taxonomic group.
Some groups (Mollusca, Ostracoda)  do not occur if pH falls
below a certain threshold. However,  it  is  very difficult  to
prove the absence  of a taxon and additionally  it is
generally difficult to demonstrate  the  relationship between
the absence of  a  taxon and a certain ecological factor.
  3. Pa IeoI imnoIogicaI studies should  exist which provide  a
basis for the discussion.
  In most of  the  taxonomic groups mentioned above abundance
of remains in lake sediments is extremely  low. Hence,
kilograms of material  are needed and only  single specimens
are found more  or  less occasionally. This  is the case  in
Mollusca, Acari,  Ephemeroptera,  Odonata, Megaloptera,
Heteroptera, Coleoptera,  and Trichoptera.  The  remaining
Ostracoda avoid Iow pH conditions.  Rhizopoda occur at  t ow

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   0.
 RHIZOPOUA
                 GASTROPODA
«£" " """SfV^" v   f
MEGALOPTERA
                                  B1VALVIA
                                                                            329
                                   EPHEHEROPTERA
                              -sA
                                                        ODONATA
                                                        •i.-     t~r-
                                                         "tffrgr
                                                          •^
                                                           M
                                                        TR1CHOPTERA
               D1PTERA
    I nvc'ft irlir.i ICK iiiiJ


    rciiiiiins  in  lake so dime nis

-------
                                                                 330
and high pH values (Grospietsch 1958) and  their  remains  are
often abundant in lake sediments. But they have  been
primarily used as indicators of changing moisture  during bog
development (Tolonen 1979).
  Due to this procedure of selection  the Chironomidae  among
the Diptera are the only  taxon which  left  ov.er.  Chironomids
are the predominating  insects  in  lakes both  in  respect  to
number of species and  individuals. They occur  in all  types
of freshwater habitats and chironomid analysis  is  an
established method in  paleolimnological research (Stahl
1969, Frey 1964,  Hofmann  1971b, 1979).
   In  large lakes 100 to 200 species occur  the  head  capsules
of which are preserved in  the  sediment. In respect  to
identification of these remains there are  some  restrictions
because chironomid taxonomy is generally based  on  adult
males. However, we don't  have  adults  and we  even don't  have
complete larva. The basis  for  identification  is  in  most
cases a more or less incomplete head  capsule.
   In pa IeoI i mnological research chir onom ids  have up to  now
been primarily used to follow  the process  of  eutrophication
in lakes. Recently, a  few  papers  came out  discussing  the
influence of changing  pH  on chironomid assemblages.
  This is  to show you  just one example of  a  core study  of a
north German lake (Schoehsee). In the first  phase  of  lake
development chironomid species occurred which  are  typical of
oligotrophic conditions.  They  disappeared  during lake
history
in the postglacial period  and  occur today  in  oligotrophic
lakes of Scandinavia and  the Alpine region.  The  occurrence
of such species is closely relateted  to the  oxygen
conditions in  the hypoli mn ion  which is on  the  other  hand
related to the trophic conditons  of the lake.  So their
disappearance  indicates oxygen depletion during  summe r
stagnation and the establishment  of an eutrophic lake
(Hofmann 1971b).
  Relationships between pH conditions and  the  species
compos ition of the chir onom id  fauna became evident  by
observation of recent  faunas.  Brundins (1949)  study on  the
bottom fauna of Swedish lakes  included some  acid,  polyhumic
lakes. Minimum pH was  5.7. Brundin  listed  an  assemblage  of
chir onom id species which  are characteristic  of  low pH
e nv i r onmen t s:
Ab labesmyi a  brevi tabiI is       Tr issoctadi'us  mucronatus
  Ablabesmy/a  long/palp/s      Chironomus tenuistylus
   Zalutsch/a za/utschicola     Sergentia  longi venfris.

 , Even at  lower pH values  in Lake Trestickeln  (Sweden)  (pH
range 3.9 - 4.6) Wiederholm &  Eriksson (1977)  found a  fairly
diverse chironomid fauna  with  Za Iu t schi a present and  high
abundance of Chironomus in the littoral zone.
  Mos sberg £» Nyberg (1979) summa r i z ed some trends  in  the
chir onom i d commun ities  in  relation  to pH on  the  basis  of
results f r om seven Swedish takes: 1.  The chir onom id fauna of
these  lakes, where pH  ranged between  3.6 and  5.4,  were  again
characterized  by  the occurrence of  Zatutschia.  2.  A
succession from Sergentia longiventr/s (which  was  a
character  species of Brundins  (1949)  polyhumic  lakes  with pH

-------
                                                                            331
   100
    60
    60
    20-
                               = A28.9-85.6x
.0 4.2
4.4
4.6
4.8
5.0
pH
     FIR.  2.  Relative  number of Chironomiis .»/>.  in  the
     littoral zone (1 and 2 m)  in relation to pH. (In  per
     cent  of totn! fauna.)
 60-
 AO
 20-
100 -i  Chironomus  sp JU Phaenopsectra sp.
 ao
                  m
                  X
                          in
                                              c.
                                              :2.
                                              in
                                              o>
                                                      -j

                                                      a
                                  m
                                         o<
                                         £
   4.0
                                      4.4
4.6
4.8
5.0 pH
 Fig. 3. Relative importance (in percent of total fauna)
 of Cli:rono»>ns sp. and Phacnoprccira  ;p. at 6—10 m
 depth in five of the lakes.
Mossberg  and
             (1979)

-------
                                                                 332
values between 5 and 7)  is  replaced by  Ch/ronomus at  a  pH
level of about 4.5. 3. Relative abundance  (percentage)  of
Ch /ronomus increased in  the  littoral zone  with  decreasing
pH.
   The latter  is in accordance with a  list  given  by
Thienemann (1954) of chironomid taxa found in waters  with  pH
below 4 due  to sulphuric acid. Under these conditions  there
is a distinct  predominance  of  the genus  Chironomus.
  The results  of these observations may  be summarized  as
foilows:
  1. The chironomid faunas  at  pH below  7 are positively
characterized  by the occurrence of certain species
(indicator species).
  2. Two pH  ranges are obviously characterized  by  different
taxa: above  4.5  to 5 the typical taxa are  Za Iu t sch/3,
Sergent/a  longiventris,  Ch/ronomus  tenuistylus. Below  4.5  a
shift occurs  to  predominance of Ch/ronomus alone.
  Hence, among the chironomids  indicator species  of
different pH  conditions  exist. The question arises  if  such
indicators can be used in pa IeoI imnoIogicaI studies  to
demonstrate  the  effect of low  pH on the  chironomid community
and, furthermore,  to reconstruct former  pH conditions.
  Walker & Paterson (1983)  observed the  chironomid
succession in  long cores from  two humic  lakes in  New
Brunswick, the recent  pH values of which ranged between 5.2
- 6.7 and 4.0  -  4.8, respectively. The  subfossil  assemblages
were highly  diverse and  the  indicator  taxon Zatutsch/a was
present in both  lakes. The  last phase of development  in the
more acid lake was characterized by a decrease  in
Ta n y t a r sus
and an increase  in Ch/ronom'js  and Psec t roc i ad i us,  which has
been explained by  the establishment of  peat-pool
e n v i r o nme n t .
  Recently,  Brodin (ms.) presented some  interesting  results
from Lake Flarken  in Sweden. The author  very carefully
discussed the  changes of the environmental  conditions
reflected by  changes in  the  chironomid  community.  In  this
case climate was an important  factor governing  the
development:  Changes in  temperature and  humidity  led  to
falling and  rising water level. The rise of the water  level
led to the estabt i shmen.t of  a  hypol imnion  as a  low
temperature  environment  as  an  habitat of cold stenothermal
profundal species.  So climate was one  factor and  the  other
predominating  factor was pH: A major phase of lake
deveIopment was  very distinctly characterized by
predominance  of  two species  one of  them  was Zalutsch/a and
its occurrence is explained  as  indicative  of  the  existence
of a polyhumic and low pH environment. A mos t d r ama t i c
change in t.he  chironomid fauna occurred  in the  surficial
sediment layer:  The number  of  taxa decreased  from  50-55 to
15-20 and a  species succession  led  to predominance of  two
Chironomus species.
  This development  was obviously related to a drop  in  pH
which was 6.5  in 1974 and between 5.0 and  5.5 in  1979/32.
Th i 5 clearly  demonstrates the  effect of  a  further  drop  of  pH
on a " Iow-pH-commun i t y" .
  The same process has been  observed by  Moss berg  (ci ted

-------
                                                                                         333
    C l> i r o n o m i d en a u s in i n e r a 1 s a u r e n  (HiSOi) C e w a s s e r n
                          mil e i n c in  pH  < 4
               Name
Cchict
Niedrigslci pll
Ccratopogonidac:
I^asioliclea aciilicola	      Japan
Dasyhelea lersa	      Sumatra
Ceratopogonidae  vermiformes	      Europa
Tanypodinac:
Ablabcsmyia monilis	      japan
Ortliocladiinae:                     Japan
Corynoneura bifurcate	      Europa
Chironornariae:
Chironomus acerbiphilus	      Japan
Chironomus sp. sp	      Japan
Cliiroiiomus costatus opicatus	      Sumatra
Cliironomus sp	      Sumatra
Cliimnoiiius plumosus	      Japan
Chironomus tlorsalis	      Europa
Chironomus sp. t/mmnii-Cruppe ....      Europa
Chironomus sp	      USA
PentopeJilum coiwexum  .......     • Sumatra
Tanytarsariae:
Tanytorsus sp	      Japan
                  2,68
                  3,17

                  3-5
                  2.9
                  3,17

                  1.4
                  1.4
                  2,83
                  2,68
                  3.5
                  3,17
                  3.1
                  3.6
                <4

                  2.9

-------
     POHTEY POND CHIRONOMID DIAGRAM
                                                              »d<*
   35
     0  200400 600
                                                0  20 40 60 60 100%


                                    Fig. S. Porlcy Pond percentage chironomid diagram.
Walker  and  paterson  (1983)
                                                                                                                            OJ
                                                                                                                            CO
                                                                                                                            -p.

-------
     WOOD'S POND PERCENTAGE CHIRONOMID DIAGRAM
                                                       0 20 40 60 SO 100%
                                           Fig. 6. Wood's Pond percentage chironomid diagram.
Walker  arid  paterson( 1983  )
                                                                                                                          CO
                                                                                                                          CO
                                                                                                                          tn

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Chronology
Corynocara amblgue
Polypediium nubveulosurn
Paratanylarcui »p.I
PtaclrocUdiut 7 tordldallut
Tanylarcut uimaentli
Abl»ba»myl* monlll*
Tanylariut ap. Q
Dlcrotandlpa* nar«o»u«
Chlionomui plumotui
Tanylartui 7 glibretcan*
Paactrocladlut "taptantrlonalla"
Tanylartut cf. gragarlut
Procladlut cf. chorau*
Dlcrolandlpai »p- Q
Chlronomu* gr. Ihumml I
Cladolanytaraut cf. mincut
Cladopalma 7 vlildula
Slampalllnalla cf. minor
Polypediium gr. icalaanum
Pageallalla orophlla
Zaluttchla i»lul»chicola
Tanytaraut gr. amlnului I
Cladotanytareua cf. atrldoraum
Tanyltrtut chlnyenila
CUdolanylaraua nlgrovlllatua
Cladotanytarau* ap.I
TaAnytaraui type m«dlua
Procladlui ap. II
Chlronomua gr. plumo»u» n
Slampallina bautal
Tanylaraua gr. eminulut II
Tanylanua lugani
Paaclrocladlua lypa •dwardtll
Chlronomu* >p. X
Chlronomut ap. VI
Php«jfOp»eclra 7 flerloei
Lake Flarken. Most abundant  chironomid taxa at each sampling level of


the main core. For comparison,  the most abundantly occurring taxa


in the lake at present,  gained  from live chironomid sampling in


1979-1982, is indicated  in the  right part of the figure.
Rink order of lii*
Q most abundant

   Znd
O  3rd
          •  5|h
             (ms.)
                           GO
                           CO
                           en

-------
                                                                337
after Brodin) in Lake Grimsgoel where pH dropped from 6.2  in
1949 to 4.8 - 5.5 in 1977: As  in Lake Flarken, 50 % of  the
chironomid species disappeared. The  low pH  led to an
increase in faunal similarity  between the two  lakes. Before
acidification 15 % of the species were common  in both lakes,
now they have 40 "*• of the taxa  in common. Thus,
acidification led to characteristic  and uniform chironomid
commun i t i es.
   As  the effects of cultural  acidification occur very  near
the sediment  surface, there  is  the chance to observe this
process on the basis of short  sediment cores.
    In an Bavarian lake (West Germany) with  a recent pH  of
3.6 - 4.8 a 40 cm core has been analyzed (Erneis-Schwarz &
Kohmann 1984). There was a general trend of reduction of
number of  taxa which began already at 40 cm sediment depth
and in the uppermost layer an  increase in Ch/ronomus and
disappearance of  Tanytarsus was attributed  to  acidification.
  Some limitations in the interpretation of results from
such short cores are evident:
   A main advantage of  pa IeoI imnoIogicaI  methods is that
they allow to characterize the  "predisruptive  conditions"
(Binford,  Deevey & Crisman 1983). For the interpretation of
what was happening near the sediment surface we need
i n f o r ma tion on the "background  variation" of species
abundance and occurrence due to successions under natural
conditions. This  information can only be supported by the
analysis of long sedi men t cores. This lack  of  info rma tion
often  leads to an overaccentuation of the variation observed
near the sediment surface.
  Results from single cores neglect  horizontal variation,  so
Henriksson, Olofsson S. Oscar son (1982) based  their results
on mean values from  three short cores. They were from two
Swedish lakes with pH ranges between 4.3 and 4.7. In the
uppermost  layer, a decrease  in  Tanytarsini  and an increase
in  Sergentia and Psec troclac/ius was  observed which was
explained as a result of acidification. The mos t recent and
most dramatic change of the  fauna  is obviously not
documented in the sediment:  In  the cores from  Lake Gardsjoen
869 head capsules have been examined and no specimen of the
genus  Chironomus has been found. Today Ch/ronomus belongs  to
the predominating taxa in the  lake.
   Again,  the interpretation of the  changes  in subfossil
assemblages is difficult because  the natural variation  is
not known. And,  as in the example by Erne i s-Schwa r z & Kohmann
(1984), in the diagrams there  is no  indication of the
influence of   low pH, because no indicator species was
present. It is insufficient  to  discuss the  influence of an
ecological factor such as pH on the  basis of genera (with
some exceptions). Phaenopsectra obviously means
Sergent i a in
which only one species, S.  longiventris,  is typical of
polyhumic lakes (Brundin  1949). Chironomini  includes taxa
such as Chironomus which  increase with decreasing pH and
others which disappear.
  The problem is  that at a pH  higher than about 4.5 a
relatively diverse chiron om id  fauna ma y exist  without
indicator  species which indicates a  pH below 7 and which can

-------
    Orllwclodllnor
                                    Tonypodlnot
                                                          CMionominaf
                                                                            Chliononlnl      Tonrlor|lnl
 0-
 l-»
 1-10
11-10
  lltlt
            Abbildung  1:
            Die  relative  Abundanz der  Unterfami 1ien Orthocladiinae,  fanypodi-
            nae,   Chironotinae (Chlronotini 4  Tanytars/niJ;   alle Chirqnonmi-
            den-Gattungen  einer Sedimentschicht  entsprechen  1007..
 Emeis-schwarz  and  K°hm»nn
CO
CXI

-------
                                                                                                339
                                     LAKE   GARDSJON
     0   10   20   30   40   SO   0   10  20   0    10   20   30   40    0    10   20   0   10   20
1-2
5-6
8-9
14-15
cm

|


Phaenopsectro
JL

IT
IJ
other
Chironomini
,1


1
Tanylarsini
j

I



1

	 I
Tanypodinae



1
Orlhocladinae
                                  LAKE   HARSEVATTEN
                                                                        10   20   30  40   50
1 -2
5-6
8-9
14-15
cm
F
]
Phaeno-
psectra
V

J
.elht
Chiro
ni

r
nomi-









Tanylarsini









Tanypodinae

I


Orthocladinae
Fig. - Hercemuge distribution of head capsules of different chironomid subgroups at different sediment levels in Lake Clrdijbn an<<
Lake Harsevaucn.
   Henriksson  et  al.   (1982)

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                                                                                                                       340
 Tahlf 3. Change* in »ome chirunomid subgroups reported as eltecls uf ucidificatiun ol oligohumic lake* with an
 actual pH level below 5.

 Lake*                                     Tanytar*inii    I'liui-nu/i.'n-cira   Pneciriit'lailius   Cliiri>iiiniiu.\

 (iardijun. prulundal                                      +               +
 llar^evaltcn. profundal                                    +               -r
 Tre>iickcln(Wiederholm& Eriksson 1977)                  +                              +
 l-'ive lakes, liloral (Mossberg 1979)                                         +              +
 l-'ive lakes, profundal (Mossberg 1979)                      +                              +
Henriksson  et   al.

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                                                                341
be identified at the larval head capsule.  In  the  list given
by Brundin (1949) 6 species are considered  to be  typical of
pH values above 5.5 and below 7, only one  of  them
(Za lutsch / Nyberg (1979)  have shown that
below pH 4.5 Sergenf/a  longiventris  typical of polyhumic
lakes is replaced by Chironomus. The  genus
Psectrocladius  is
not typical of  low pH.  Similarly, the genus Chironomus  does
not indi.cate acidification, as  it is  also  abundant  in
eutrophic and polluted sites (Thienemann 1954).
  If pH  drops distinctly below 4 as  jt  is  the case  in the
Reinbeker Tonteich  in the  vicinity of Hamburg (West  Germany)
the effect of low pH can be read from the  chironomid
community. The  chironomid  fauna has been sampled  in  1933
when pH  was 3.2 and in 1950 when pH was  3.3.  In  both  cases,
the predominating taxa were Chironomus  and
Corynoneura
(Thienemann 1954). The chironomid head  capsules  from a  short
sediment  core obviously reflect  this  extremely poor
chironomid assemblage:  76  % of  the specimens  belonged to  two
Chironomus species, followed by  Corynoneura.  Four taxa  of
three genera made up 97 %  of the material  (Hofmann,  unpubl.
data ) .
  Also in this  case the effect of low pH  is reflected by  the
tow diversity of the assemblage  rather  than by the
occurrence of indicator species.  It  is   known from  adult
midges sampled  at the pond that particular  Chironomus
species  were involved which are  typical  of  acid
environments. However,  they cannot be used  as  indicator
species  if only subfossil  ma terial  is available  because the
species  cannot  be identified at  the  larval  head  capsules.
  In this point  lies the most important  restriction  in  the
use of chironomids as indicators of  the  pH  conditions.
Relationships between the  fauna and ecological factors  can
in most  cases only be deduced on the  basis  of species.  So,  a
prerequisite for the use of these organisms as indicators  is
an accurate  taxonomic differentiation of  the  subfossil
ma terial. Generally a refi nemen t of  larval  t axonomy  i s
necessary.
  Although some  trends  in  the response  of  chironomid
assemblages  to  dropping pH became distinct  by the material
published there  is need  for some more case  studies  based on
long sediment cores and of course including other
pa IeoI imnoIogicaI methods  which  provide  information  on  what

-------
Reinbeker Tonteich, Naumann-Lot,  16.3.1983: Chironomiden
Sedimenttiefe (cm) 6-8 4-6 2-4
Frischsediment (g) 7.8 9.1 7.5
Chironomus p 37 55 4O
Chironomus a 23 17 12
Corynoneura 24 12 4
Tanytarsus 5 5 8
Polypedilum gr. sordens 1
Microtendipes 1
Cladotanytarsus 1
Glyptotendipes 1
Psectrocladius 1
Procladius
Pentaneurini indet.
y 69 92 66
0-2 y-
9.8
57 189
61 113
6 46
2O 38
1
1
1
1
4 5
1 1
1 1
150 397
Tanytarsus evtl. = Tanytarsus gr. pallidicornis  (s.  Probe  6-8  cm)
 Abundance of chironomid head capsules in a short sediment  core  from  the
 Reinbeker Tonteich (y. Germany)  (nofmann, unpubl. data)
                                                                                                00

-------
                                                                 343
was going on in the lake ecosystem.
  To come to the other  invertebrates which have been
neglected: Of course  they have to be  included whenever
possible. The Rh i zopoda are of particu'lar  interest  in  this
respect. But also the Ostracoda should be  considered.  The
consideration of these  different groups gives the chance  to
get information on the  development of many representratives
of the  fauna under the  influence of decreasing pH.

-------
                    344
Re IPiences

   Bintord. M. W., Deevey.  E.S.  6.  Ctisman,  T.  L. (15-63):
P a Ie oI imn ology: an historical  perspective on lacustrine
ecosystems. Ann. Rev. Eeol.  Syst.,  14:  255-266.

   Brodin, Y.: The postglacial  history  ot Lake Tiarten.
interpreted from subfossil  insect  remains,  (ms.)

   Brundin. L. (1949): Chironomiden und andere Bodentiere
der  suedschwedischen Urgebirgsseen.  Rep.  Inst. Freshw. Res.
DrottninghoIm, 30: 1-914.

   Erne i s-Schwar z . H. £. Kohmann,  F.  (19M):  Die Chironomiden
(Diptera: Chironomidae)  eines  veisauerten Bergjees. Kleiner
Arbersee. Bayerischer WaId.  in:  Lenhart.  B.  el al. (ed.):
Vcrsauerung in der BRD, Verlag E.  Schmidt (in press).

   Frey, D. G. (1964): Remains ot  animals in Quaternary  lake
and bog sediments and  their  interpretation.  Arch. Hydiobiol.
Beih. Ergebn. Limnol.  2:  1-114.

   Grospietsch, T. (1968):  WechseI t ierchen (Rhi?opoden ) .
F r anckh, St uIt gar t .

   Henrikson. L.. Olafsson,  J.  B.  f. Oscarson.  H. G. (1982):
The impact of acidification on Chiron on-, idae (f>iptera)  as
indicated by  subtcssil stratification.  HydrobioIogia  86:
223-229.

   Hofmann. W. (1971a):  0 i e DOStgI aria Ie  Entwicklung  der
Chironomiden- und Chaoborus-Fauna  (Dipt.) des Schoehsees.
Arch. Hydrobiol. Suppl.  40:  1-74.

   Hofmann. W. (1971b):  Zur  Taxonomie und Paloekologie
jubfoisiler Chiron omiden  (Dipt.)  in Seesedimenten. Arch.
Hydrobiol. Beih. Ergebn.  Limnol.  G:  1-50.

   Hofmann. W. (1979): Chitonomid  analysis.  >n: Berglund.
B. E. (ed.):  Pa IaeohydroIogicaI  changes  in the  temperate
zone in  the last  15000 years.  Subproject  B.  Lake and  mire
environments.  IGCP 158 B.  Project  guide,  vol.   2. Lund:
259-270.

   Mossberg.  P. £. Nyberg.  P.  (1979):  Bottom tauna ot  small
acid forest lat.es. Rep.  Inst.  Fresr.w.  Res.  Or o t t n i ngho I m  56:
77-87.

   Slahl. J,  B. (1969):  The uses  ol  chironomids and other
midges in  interpreting  lake histories.  Mill. int. Ver.
Limnol.   17: 111-125.

   Thienemann. A.  (1954):  Chir onomus.  in: Die
C< i nriengewae:. i,e r . Stuttgart'.  20:  1-834.

   Tolonen. K. (1979): Rhi;opod analysis, in:  Berglund. B.
E . ( e d . ) : Palaeohsdrological  changes in  the temperate  rone  i
the last  15000 years.  Subptoject  f*.  Lake  arid m i i e
env i r onmen Is.  IGCF 158 B.  Project  guide,  v. o I .  .. Lund:


   Walker, I. R. & P a t e r «. o n .  C.  Ci.  i i 9 J. 3  ) :  Post-glacial
•r h i  i o n crri i d f. u c c e r r i t*n  in  t *,,-> *-ma I I .  h u'i-1 < I AI e- 5.  in the IJ t- w
P- r ufi svw i ck - Nova Scotia  « C a n a d a i  border  n r e 3 .  r i r- =, hw.
I n v e r t r- ti I . 6 i O I .  .'• : f. 1 - 7 > .

   W i e cl e i h o I m . T . f. E r i k 11 o n .  L .  ( 1 ri 7 7 ) :  benthos o t an acid
lake. • j i t o; 23: j 6 1 - r f. 7 .
n

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                                                                             345

          CONTRIBUTIONS OF PLANT PIGMENTS TO PALEOLIMNOLOGY

                          Seward R. Brown

     The commonest and most widespread method of estimating phytoplanktonic
biomass in freshwaters and the oceans is by measurement of chlorophyll £
content.  The approach is made possible because of the ubiquitous presence
of this pigment in the photosynthetic tissues of plants.  Other chlorophylls,
phycobilins, and a wide variety of carotenoids are frequently associated
with it, but the suite of these pigments differs greatly among planktonic
taxa.  Because the pigments are preserved in lake and marine sediments, a
similar approach can be taken in estimation of former planktonic populations
in existence at the time when the pigments were deposited.  In fact, this
is the only approach that permits an estimate of the total planktonic assemb-
lage, since microfossils usually provide only evidence of silicified algae
such as the diatoms and chrysophytes.  In living assemblages the presence
of blue-green algae, flagellates, and many non-silicified taxa may be readily
observed on microscopic examination of plankton samples, yet these forms
which are rarely preserved in fossil samples may have contributed very signif-
icantly to the planktonic biomass of their time. This becomes a matter of
considerable importance in paleolimnology if studies encounter periods of
eutrophic conditions when blue-green algae often dominate the algal assemblage,
as well as in other situations where flagellates and picoalgae are known to
contribute very substantially to primary productivity.

     The main obstacle to the use of pigments and other organic fossils
relates to molecular stability of these compounds.  As organic entities,
they are particularly vulnerable to degradative processes.  Diagenesis begins
in senescent and non-living cells and is accelerated by photo-oxidative pro-
cesses, bacterial attack, and passage through the guts of grazing anitials.
The diagenetic pathways in chlorophyll are well known.  A sequence of coloured
compounds is formed, beginning with the loss of magnesium from the molecule
to form pheophytin, or breakage of the ester linkage with phytol to form
chlorophyllide.  Loss of both substituents produces pheophorbide, moreover
any of these derivatives may also be found in oxidized form.  As a result,
lake sediments invariably contain a complex mixture of native chlorophylls
and various products of the diagenetic sequence in addition to the carotenoid
pigments associated with the photosynthetic apparatus of the algae that produced
them.  Measurement of the chlorophyll of living planktonic assemblages is rel-
atively simple because only native chlorophylls and early derivatives need be
distinguished.  The sedimentary mixture of fossil forms requires chromatographic
separation before measurement can be achieved, but methods for this separation
and identification have been developed and are routinely practised.  Lability
of the pigments imposes a further inconvenience on paleolimnologists in that
sediment samples require somewhat more protective handling than is necessary
for samples to be analysed only for pollen and microfossils.

     In this paper the emphasis on chlorophyll is placed on its use as an
estimate of total algal production where the objective is to reconstruct
paleoenvironmental conditions through interpretation of algal response to
change in them.  Increases in populations of indicator taxa are seen as a
response to changes favourable to those taxa.  Ecological success, however,
is the outcome of competition, and the competition is rarely to extinction,
thus the need for a measure of total productivity relative to that of any
specific producer or group of producers.

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                                                                            346
     Changes in environmental conditions are frequently associated with
change in the levels of nutrient input to lakes and with change in the
composition of those inputs.  Some algal forms compete more successfully
than others for scarce nutrient resources.   Upon enrichment of nutrients,
changes of dominance in the algal assemblage take place, productivity in-
creases, and competition for nutrients may become less important than that
for light - in which case low light-adapted forms are favoured.  Change in
metals, associated with change in pH, undoubtedly affects various taxa
differently, although their toxic effects have been little studied and are
poorly understood.  It is well known that biotic interactions occur and
that these too are important determinants in the outcome of competition.
Diatom populations may be inhibited by allelopathic interactions with
blue-green algae.  Selective grazing by zooplankton may suppress those
algal species favoured by the grazer.  Heterotrophy and disease are addit-
ional factors.  Under some conditions, as yet most frequently observed in
meromictic lakes, the minute picoalgae contribute as much as 85% of total
algal productivity.  Competition must be seen, therefore, as a very complex
process.  From this it follows that where its outcome is to be used in the
interpretation of environmental change, some attention must be given to the
total planktonic community in addition to that focused on selected component
species.  The chlorophyll derivatives preserved in sedimentary deposits have
the potential to supply that information, as well as to provide insights
into the intensity of grazing pressure exerted by herbivorous zooplankton.

     While the ubiquity of chlorophyll 
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                                                                           347
extracts.  Differences in their polarity make phase separation between
organic solvents a simple matter whereby the classes thus separated were
thought to distinguish between allochthonous and autochthonous inputs to
sediment deposits.  Attempts were also made to estimate planktonic species
diversity based on numbers of carotenoid entities discovered in lake sed-
iments, however these results may be misleading because the studies did
not take into consideration the fact that diagenetic products may have
contributed to these numbers.  The validity of the approach remains to be
tested through rigorous identification of the carotenoid fractions in the
pigment assemblage.  A few readily distinguished members have been isolated
from carotenoid mixtures, and these have been used successfully to indicate
the presence of specific algal components of former planktonic communities
where no other evidence of their existence was preserved in the sediment
matrix.

     The remarkable advances that have taken place in carotenoid chemistry
in the past quarter of a century have opened the way to much greater exploit-
ation of the ecological information provided by these pigments.  It is not
suggested that routine fractionation and identification of all components
of sedimentary extracts is a practical measure for paleolimnologists, but
it is clear that some of these pigments can be readily used to identify
elements of the planktonic assemblage that otherwise cannot be recognized.
Thus far the best success in this endeavour has been achieved relative to
the blue-green algae and photosynthetic bacteria, but certainly present and
future use is not restricted to this limited application.  Paleo-reconstruct-
ion depends upon the re-assembly of fragments of the fossil record, and its
validity is increased by the more such fragments that can be fitted together.


                        REFERENCE S
BROWN, S. R. 1969. Paleolimnological evidence from fossil pigments.
             Mitt. Internat. Verein. Limnol., 12:95 -  103

BROWN, S. R., R. J. DALEY and R. N. McNEELY, 1977. Composition  and  stratig-
             raphy of the fossil phorbin derivatives of Little  Round Lake,
             Ontario.  Limnol. Oceanogr., 22: 336-348
BRUGAM, R. B.,  1984. Holocene Paleolimnology in. H. E.  Wright, Jr. ted.)
             Late Quaternary Environments of the  United States,  Vol.2
             University of  Minnesota Press, Minneapolis

CARPENTER, S. R. and A. M.  BERGQUIST,  1984. Experimental tests  of grazing
             indicators based on chlorophyll ja degradation  products.
             Archiv. Hydrobiol.  (in press).
DALEY, R. J. 1973. Experimental  characterization  of  lacustrine  chlorophyll
             diagenesis. 2. Bacterial,  viral and  herbivore  grazing  effects.
             Arch. Hydrobiol., 72: 409-439

DALEY, R. J. and S. R. BROWN  1973. Experimental  characterization of  lacust-
             rine chlorophyll diagenesis. 1. Physiological  and  environmental
             effects. Arch. Hydrobiol.,  72: 277-304

FOGG, G. E.  and J. H. BELCHER  1961. Pigments from the bottom deposits of
             an English lake. New  Phytol., 60:  129-138

LIAAEN-JENSEN,  S.  1978. Marine  Carotenoids. pp.  1-73  jji P.  J.  Scheuer (ed.)

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                                                                           348
            Marine Natural Products, Vol. 2, Chemical and  biological
            perspectives.  Academic Press, New York.

SANGER, J. E. and E. GORHAM  1972. Stratigraphy 'of  fossil  pigments  as  a
            guide to the postglacial history of Kirchner Marsh,  Minnesota.
            Limnol. Oceanogr., 17.: 840-854
REPETA, D. J. and R. B. GAGOSTAN  1982. Carotenoid  transformations  in
            costal marine waters.  Nature 295_: 51-54

WATTS, C. D. and MAXWELL  1977.  Carotenoid diagenesis  in  a  marine  sediment.
            Geochim. Cosmochim. Acta, 41; 493-497
WATTS, C. D., J. R. MAXWELL and H. KJOSEN  1977.  The potential  of  carotenoids
            as environmental indicators, pp. 391-414 iji R. Compos and  J.  Goni
            (eds.) Advances in Organic Geochemistry.  Enadimsa Servicio
            Publicaciones.

WHITEHEAD, D. R. and T. L. CRISMAN   1978. Paleolimnological  studies of
            small New  England  (U.S.A.) ponds:  1. Late-glacial and  post-
            glacial trophic oscillations. Polish Archiv. Hydrobiol.,  25:
            471-481                                                   ~~

ZULLIG, H.  1982. Untersuchungen fiber die Stratigraphie von  Carotinoiden
            im geschichte^n Sediment von  10 Schweizer Seen  zur Erkundung
            frGherer Phytoplankton-Entfaltungen.  Schweiz. Z. Hydro1., 44:
            1-98

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                                                                               34?

                         Sedimentary  Humic  Materials
                              Daniel  R.  Engstrom
                         Limnological  Research Center
                              220 Pillsbury Hall
                           University  of  Minnesota
                            Minneapolis,  MN  55455
     The  use  of  sedimentary humic substances in my work  has  been  largely

restricted   to  "natural"  lake  acidification  and  has  not  been   related

specifically  to  acid  rain phenomena,   although I think  that  it  may  have

important  application to such problems.    Those individuals working on  water

chemistry  in  acidified lake regions have generally separated out lakes  that

have high dissolved organic content from clear-water lakes,  because it's been

observed  and/or  assumed  that they behave differently in  response  to  acid

inputs.  In  addition,  it seems likely that humic materials in surface waters

could  influence  diatom communities,  so that in reconstructions of  pH  from

diatom  stratigraphy,  water  color  (dissolved organics) may be one  of  those

"other factors" that affect transfer functions.  Then finally, it appears from

some  of the Scandinavian studies that there is an increase in water  clarity,

that  is  a decrease in dissolved humics in surface waters,  as  lakes  become

acidified.   If we can somehow reconstruct the humic content of lake waters in

the past, we may then have an additional  index to changes in lake acidity.

     The  results  that  follow  are  from  ongoing  paleoecological  work   in

Labrador, Canada, and most of the interpretations are from a series of surface

sediment  samples and associated water chemistry data that were  collected   in

1979  as  part  of a regional survey of 70 lakes  distributed  throughout  the

Province  from  the Strait of Belle  Isle north to Okak Bay  (Fig.  1).   These

sites  span  a distance of 800 km across a pronounced  vegetational  gradient,

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                                                                               350
from  spruce-fir  forest in the  southeast,   through  spruce-lichen  woodland,



forest  tundra and finally open tundra in the north;  there are also extensive



peatlands in some parts of southeastern Labrador.    The lakes are clustered in



these different vegetational regions.



     Water  quality data front Labrador show  extremely dilute lakes  (Fig.   2);



mean  alkalinity is around 2 mg/1,  mean conductivity is about 10  uS/cm,   and



most  sulfate  values are below 2 mg/1.   On the other  hand,  pH  values   are



largely  circumneutral.   There is no indication from these water quality  data



of acidification from anthropogenic sources,  so we have a group of  sensitive



yet  pristine  sites  that  could  serve as   an  important  reference  for  pH



reconstructions (from diatom spectra)  in acidified lake districts.



     I'll  first  discuss  the relationship  between the content of  humics  in



surface  waters and the content of humic materials in the sediments  of  those



same lakes.   I have used apparent color (in  standard relative units of the Pt-



Co scale) as a simple estimate of humic content of lake water.  While it might



be  preferable  to have a more direct measure of humic concentration  such  as



D.O.C.,  for field work in remote regions where laboratory analysis of samples



may  take weeks,  a more immediate determination using a field comparator  is a



reasonable  solution.   The  distribution of water color in  relation  to   the



different vegetational zones is illustrated  in Figure 4.   A striking trend is



evident  in  that lakes in the tundra region  have extremely clear water  (Pt-Co



color  generally 5 units or less),  lakes in lichen-woodland and forest-tundra



areas are somewhat darker (10-20 Pt-Co units), while in forested regions water



color  from   dissolved  humics is much higher,  and the  range  of  values  is



greater.    In  those southeastern lakes surrounded by peatlands,  the color is



darker  yet.   While vegetation and soils are obviously important controls  on



lake  water   color,  there  are  other factors that  influence  the  level  of

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                                                                               351

dissolved humics in these lakes:    the area of the catchment relative to  lake

surface,  the water residence time,  and the sedimentation/degradation rate of

the humic materials themselves.

     The  content of humic materials in the sediments of these same lakes  was

measured  with a spectophotometric method for analysis of dissolved tannin and

lignin   (Standard Methods) as modified for lake sediments  by  J.P.  Bradbury.

20-25  mg of dried powdered sediment were extracted in 0.1 N KOH for 1 hr.  at
   o
100 C.   A  mixture of tungstophosphoric and molybdophosphoric acids  (tannin-

lignin reagent) was then added to a diluted aliquot of the. hydroxide  extract,

and  the  absorbance  of the resultant blue complex was measured  at  700  nm.

Spectrophotometric  readings were calibrated against tannic acid standards  to

provide a relative measure of humic content per gram dry sediment.

     An  important  problem  that  should be mentioned at  the  onset  is  the

difficulty  of comparing concentrations of a substance from a single  sediment

sample  from one lake to another.   Because of density-dependent deposition of

materials  in lake basins,  the content of humics per gram dry  sediment  will

vary  depending upon where in the lake the sample was taken.   This  situation

arises  because organic materials,  being less dense than clastic  components,

are  preferentially deposited in deep water,  which results in a concentration

gradient  across lake depth that also varies from lake to lake.    One  way  to

circumvent  this difficulty is to express the humic concentration relative  to

sedimentary  organic matter rather than total dry sediment.   Organic  matter,

including  both humic and non-humic materials,  being of more uniform density,

should be less subject to density-dependent sorting.   This is indeed the case

for the Labrador data:  humic content per gram organic matter in the sediments

is strongly correlated  (r = 0.81) with water color  (Fig.  4).   A  logarithmic

transformation  of color improves the relationship slightly  (r = 0.8S).    As  a

further  test  of this empirical relationship I obtained a  second  series  of

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                                                                               352
sediment  samples from 35 lakes in the Boundary Maters Canoe Area of Minnesota



and again compared the humic content with lake color.    As shown in Figure  5,



both  the  correlation coefficient (r = 0.81)  and the  slope of the line  (m  =



1.38)  are the same as in the Labrador data set,  although similarity of slopes



may be somewhat fortuitous.



     These  results imply a  fairly robust relationship between humic materials



in lake water and surface sediments.   However, it's seductive to think that we



can reconstruct paleo water  color without some understanding of the mechanisms



of humic sedimentation.   In  relatively simple terms, humic content per gram of



organic  sediment can be viewed as a ratio of  allochthonous inputs to the  sum



of  autochthonous  plus  allochthonous inputs;  it is  a  relative  measure  of



allochthonous to total organic productivity of the system.   If we assume that



sedimentation  of  humic materials is somehow proportional to  the  amount  of



dissolved humics in the surface waters, then an increase in water color from a



greater  flux  of humic materials to the lake,  all other things being  equal,



should increase humic concentrations in the sediments.   We might also  expect



the  autTochthonous productivity of the lake to decrease,  thereby  increasing



humic   concentrations  in the sediments,  because it is known  that  dissolved



humics  can  suppress  phytoplankton productivity either  through  shading  or



complexation of nutrients.



     A  preliminary  application of sedimentary humics in a  paleolimnological



reconstruction of water color is illustrated in Figure 6.   This stratigraphic



diagram is from Lake Hope Simpson in southeastern Labrador,  for which we have



assembled detailed geochemical and palynological data  as well.  The horizontal



lines  demarcate vegetational zones from pollen analysis:   the lowermost  zone



represents  a sedge-herb tundra,  the next a shrub tundra of birch and  alder,



then   a  zone  representing  the  transition  from  trundra  to  a   forested

-------
                                                                               353
environment,   and finally a zone covering the last 6000 years during which the
region was dominated by black spruce forest.   I  argue in some detail elsewhere
(Engstrom  and Hansen,   1984) that the content of humics in the sediments (per
gram  dry matter) accurately reflects changes in the soils and  vegetation  of
the  catchment,  which  altered the input of humics and the erosion of  clastic
materials  to the lake.   The major increase in  humic content of the sediments
(per  gram dry matter)  corresponds exactly to the development of  closed-crown
fir-forest  (ca.  7500   yr  B.P.) as determined   by  pollen  analysis.    In  a
qualitative  sense  we   might  expect that water color  would  have  increased
markedly at Lake Hope Simpson in response to this vegetational and pedological
change.   However,  if  we want to reconstruct paleo water color quantitatively
from  the  surface sample data,  the humic content of the  sediments  must  be
normalized to the organic matter.   This curve  (humics/ g O.M.) is included in
Figure  6 along with a  profile for water color as calculated from the transfer
function  shown  in Figure 4.   Because water color in derived from  a  simple
linear relationship the two profiles are virtually parallelj  an exception  is
evident  for   basal  sediments O9000 yr B.P.) for which water color  was  not
calculated.   As expected,  water color increases from about 10-20 Pt-Co units
during  the  tundra  and woodland phases to about 60  Pt-Co  units  after  the
transition  to  conifer forest at 7500 yr B.P.   These values  are  reasonably
close  to that found in corresponding Labrador environments  today,  including
the present-day value for Lake Hope Simpson  (60  Pt-Co units).  Water color was
not  reconstructed for  the oldest sediments because no modern analogue  exists
with high humic concentration (per gram organic  matter) in the tundra  regions
of  Labrador   (Fig.  7).   I hypothesize that the coagulation and deposition of
dissolved  humics  was   much more efficient during the  early  postglacial
perhaps because of high levels of suspended clays that would aid sedimentation
— so that the deposition of humic materials relative to other organic  matter

-------
                                                                               354
was greater or,   alternatively,  that the internal  productivity of the lake was



extremely low at this time, perhaps for climatic reasons.  This period probably



represents  a  clear water phase of the lake,   except for   the  aforementioned



clays inwashed from the newly deglaciated terrain.



     The  next  step  in  humic   studies would be   the  application  of  these



techniques to sediment cores from anthropogenically acidified lakes.   However,



the interpretation of humic stratigraphy from  such  systems might be  different



from  that described above for the Labrador sites  where the primary signal  is



one  of changing humic inputs to the lake.    Instead,  we  would be looking for



changes  in the efficiency of humic sedimentation.    The trend resulting  from



acidification  should  be   an increase  in  sedimentary  humic  concentration



corresponding to a decrease in water color.   Polymerization and sedimentation



of  dissolved  humics  may be more rapid in acid lakes where  high  levels  of



aluminum  and  other multivalent cations are available for  complexation  with



colloidal hutnates.   In addition,  the supression  of phytopl ankton populations



in acid lakes might lower the deposition of autochthonous  organics and thereby



indirectly increase sedimentary  humic concentrtions (per gram organic matter).



     The  empirical relationship between water color and sedimentary  humics in



present  day lakes needs to be further tested  in other  regions,  particularly



those  presently  receiving  acid  rain.    If  results  from  these    initial



applications  are  promising,  then refinements in  the analytical  procedures,



such as quantitive fractionation techniques,  are  in order.

-------
                                                                               355

                                   FI6URES

Figure 1.  Map of Labrador showing location of surface-sample sites.

Figure 2.  Selected Mater chemistry data from Labrador lakes.

Figure 3.  Distribution of water color in Labrador lakes in relation to
          catchment vegetation.

Figure 4.  Relationship between water color and sedimentary humics  (per gram
          organic matter) in 70 Labrador lakes.

Figure 5.  Relationship between water color and sedimentary humics  (per gram
          organic matter) in 35 lakes from the Boundary Waters Canoe Area,
          Minnesota.

Figure 6.  Stratigraphic profiles for 7. organic matter (from loss-on-ignition) ,
          sedimentary humics (as mg tannic acid /g dry matter and  /g organic
          matter), and the reconstruction of water color from the  regression
          relationship in Figure 4.  Vegetation zones defined by pollen
          analysis:  Zone 1 = sedge-herb tundra, Zone 2 = shrub tundra, Zone 3
          = forest transition, Zone 4 = spruce forest.

Figure 7.  Sedimentary humic concentrations  (per gram organic matter) in
          Labrador lakes in relation to catchment vegetation.

-------
                          356
LABRADOR  SURFACE SAMPLE
    SITES   1979
   • Surface Samples
   if Coring Sites

-------
                                                                                      357
HO    '/.
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-------
                                                                 358
80
70.
60
50
40
30
20
10
                             (N = 24)
TUNDRA
40
30
20
10
                                                       WOODLAND
                             (N  = 19)
30 -
20 -
10 -
            (N = 15)
                                                       FOREST
30 -
20 -
10 -
            (N = 9)
                                                       PEATLAND
             20     40      60      80     100
                      WATER COLOR (Pi-Co  UNITS)
                                                   120
     140

-------
           LRBRRDDR  LRKE5
                                     359
         Y  -31.0 + 1.32  X
in
i
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       HUMIC5   MG TflNNVB D.M.

-------
                                      360
          BWCR  LRKE5
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        Y  -45.9 +  I.36 X


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       HUMIC5   MB TflNN./B D.M.

-------
LflKE  HOPE SIMPSON
    LRBRRDOR: N52 27' N56 20'
  YBP

 1000-
 2000-
 3000-
 4000-
 5000
 6000-
 7000-
 8000-
 9000-
10000-
11000-
    O.M.
HUMICS/D.M
HUMICS/O.M.
COLOR
        M.   MG/G D.M.
                MG/G O.M.
               f i  i  i  i  i
                20  40  60
               PT-CO UNITS
                                                             co
                                                             cr>

-------
en
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              TRNN./E D.M.  

-------
                                                                           363
                     Polycyclic Aromatic Hydrocarbons

                                Ron  Hites
     Polycyclic  aromatic  hydrocarbons (PAH)  are well preserved  in  sediments
(see Figure 1  for example structures),  and as  best as we can tell, they are
not mobile in a core.   The compounds were first of interest because some of
them, particularly benzo[a]pyrene,  will  cause cancer in  animals.  Most PAH are
produced  by combustion, and therefore, when we  find them in  sediments we know
that something,  somewhere had to get burned  and that  the  combustion effluent
got to the sediment.   Logical ly it got to  the  sediment through  the air, and
I'l 1 come back to that.  There are two exceptions  to this combustion source.
One is peryl ene.  We know that it is formed  in  situ in sediments because its
concentration  increases  as we go down a core, but  we don't know the identity
of its precursor.  Retene is  another  compound which is of  natural  origin, and
it is formed  from diterpenes.
     The  paradigm that we're using  for the movement of polycyclic aromatic
hydrocarbons  from combustion  sources to aquatic sediments  is  as  follows:
There are  essentially two  kinds of sources,  one is  stationary and one is
mobile.   We're not particularly concerned about mobile  sources.   Stationary
sources can be 1 arge seal e burners of coal , for exampl e, a coal  fired power
plant or  small  scale burners of coal, for example,  home  furnaces.   The burning
of petroleum and the  burning of  natural  gas  under  the  wrong  conditions also
wil 1 give  PAH. The PAH leave the combustion  source adsorbed on  soot and are
injected into the atmosphere where  they can do one of  two  things.  They can
land near the source if the soot particles are large enough.   For  particles of
10 urn or  more,  they will  land within a few  kilometers and then be transported
into local  sinks by run-off.   This  transport mode  is not terribly  efficient

-------
                                                                364
Pyrene
                                                           Chrysene
                          Fluoranthene
                  Benzo[a]pyrene
Perylene
 100O
        Benzo[a]pyrene  emission  rates
                     in  tonnes/year
                    from  NAS,   1972
C0100
2
a
o
  10 ••
Ed

                                     1

          I
          i
                •
i
•
        Mobile      Coal big       Gas        Waste      Oil ref.
           Coal home      Oil        Wood     Open burn    Coke prod
                             Source type

-------
                                                                          365
(except in  cities which are  paved).   In remote  lakes,  this  particular
mechanism  is not applicable.  The alternate mechansim is transport by the wind
for distances  on  the  order of 1,000 kilometers.   The particles with the
associated  PAH will come out of the air either  in  the rain or as dry fall out
and then be transported through the water column to the sediment where they
will then  accumulate  in the sediment record.  We can  core  the sediment and
read the record.
     It is important to know something about the history of  inputs of the PAH
into the environment.   We would really like  to know how  many  PAH went out into
the atmosphere,  and   presumably  have come down  into the  sediments,  as  a
function of time.   We  can get  some such information from emission surveys.
Although published by  the  National  Academy of  Sciences (1972),  I must  point
out that the data  on which the inventory was  based  were measured during the
mid-1950's  to mid-1960's with  several different methods;  some  were good and
some were  bad.  Figure   2 shows the emission rate  of  benzo[a]pyrene in metric
tons per year on a logrithmic  scale.  There are three  major sources.  One  is
coke production.  The second is open burning of such  things as coal trash near
a coal  mine.  Both of  these two sources have been decreasing lately. The
other major source of PAH  is  coal  used to heat homes.  Hand stoked,  home
burners of coal were very inefficient, producing large amounts of soot and
PAH.  This  source has gone down dramatically,  and we'll  come  back  to that.  In
Figure 2,  "coal big" means industrial scale coal burning such as coal  fired
power plants.   This is not a very large source.  Oil and gas burning do not
produce much polycyclics either.  Judging from thi s inventory,  we conclude
that PAH came mostly from coal  burned in homes, coal burned in refuge  heaps
near coal mines, and from coke production (at least in the  1960's).  Much  of
this coal  waste burning and  coke production takes place in  the  United States'

-------
                                                                           366




midwest.



     Let's  look now at how these things have changed as a function of time.



Figure 3 i s a hi story of energy use in the U.S. in quadr i 11 ions of BTU's,  and



it shows  energy produced from different  fuels:  coal, oil,  gas,  and wood.  For



example, in 1850, most of the energy in the  U.S. was coming  from wood.    The



history of coal use is particularly  interesting.  We note  that  coal  use went



up dramatically around the turn of the century and then levelled off.   Oil  use



has been going up  dramatically since about 1930  (see the black bar),  and



natural gas use almost parallels that  of oil.   These historical patterns  are



quite useful.   For  example,  if we  look  at polycyclic profiles in a  core over



time and we see an  increase in the 1900's and stability ever  since, we  can



say: "The  source is coal."    On the  other  hand,  if we see a dramatic rise



starting around  1930, we can  say: "The source is oil".  There  is an obvious



connection  to  acid  rain;   presumably  PAH  from  coal  would track  pH



reconstructions in  cores.



     Before showing our data,  I thought it would be  wise to use  the scientific



method  and  to calculate what we might expect  (see Figure 4).  We  can calculate



the fluxes of polycyclics based  on  either wet or dry depositional mechanisms.



If we  use  dry  deposition mechanisms,  we can talk  in terms  of an  average



atmospheric concentration and  a depositional   velocity (which is how  fast  the



particles come  down to the  surface).   Unfortunately, there  is a  wide  range in



estimates of the depositional  velocity: 0.01 to 0.5 cm/sec.   By  multiplying



the atmospheric concentration by the depositional velocity,  we  end up with a



flux of 0.3-15  ng cm~2 yr'l from  a  dry depositional   effect.   Wet deposition is



••nuch easier to  calculate once  we  know  the concentration of PAH  in rain  which



is in the range of  1-3 ng/1.  Multiplying this by the average rainfall,  which



for the northeastern U.S. is 80-100 cmyr"^, we get a wet flux  of 0.08-0.3 ng



cm~2 yr"1.  We add the dry  and  wet fluxes  together  and  take  a geometric

-------
S^^^v History of energy use
) in the United States
v.
4O-
36-

3O-
Td a,.
|20'
w
10-
-
o-
-^ (quadrillion BTU)








H- !« 10 llj
185O 187O 189O








JL








^



*fl








"fe
191O 193O
186O I860 19OO
1920








I







t
t







/
RI ;

n
^
J
^
}
. a











3
^
^
^
i
t
t
t
i
. g
Fuel
^^^ Coal
1^1 Oil
Z3 Gas
^^^ Wood





195O 197O
194O
I960

Year
                                                           367
       Calculated fluxes
Dry deposition
    Atms. cone, x Depositional  velocity = Dry flux
    1 ng/m3     x 0.01-0.5 cm/sec       = 0.3-15 ng
Wet deposition
    Rain cone,
    1-3 ng/1
Emission basis
x Rainfall      = Wet flux
x 80-100 cm/yr = 0.08-0.3 ng
    Input rate
    * Area
    1300 x 106 g/yr * 7.8 x 1016
                 cm
  = Flux
2 = 17 ng

-------
                                                                           368
average of the ends of the range and come up with 2-3 ng cm~2 yr'l.   Another



way we can  get a flux  estimate  is to  take the emission  rate which  was



estimated  by the National  Academy of Sciences (1972) to be 1300 x  106 g/yr and



divide that  by  the area of the  U.S.   One ends up with  a  flux of  17 ng cm"2 yr"



\  Comparing  this to our other estimates, we are led to expect about 2-20 ng



cm~2 yr"''.



     Let's compare these  estimates  to what we have measured.  Figure 5 is a



table  from  a  paper  in  which  we reported PAH fluxes at  several locations



(Gschwend and Hites, 1981).  These sites include Lake Superior, Somes  Sound



(which  has a sill so it's  somewhat  separated  from the  Atlantic), Hadlock  Lower



Pond (which  is a fresh  water pond on  Mount Desert Island), and  Coburn Mountain



Pond.  We  reported f 1 uxes for three di fferent periods:  presentdayflux, a



flux  corresponding  to 1950,  and a flux corresponding  to  the  turn of the



century.   At present, these fluxes average 0.8-3 ng cm~2 yr"^  which  is in



reasonably  good  agreement with what we  calculated.   The flux  in  1950 was



generally twice as high as at  present and  the flux  at the  turn of the century



was lower by a factor of 5-10 than at present.  The data at the top of the



table are  all  from remote sites.   As  I mentioned,  if  one goes  to  urban sites,



like the  Boston Harbor, one  should find much higher fluxes. The numbers  given



in the bottom  of  Figure 5 are averaged over the  20th century for  three



locations:  Boston Harbor, Buzzards Bay,  and Pettaquamscutt  River.  The PAH



flux averages  25-55 ng cm"2 yr" ^.  This  is gratifying because Bates j^t al.



(1984)  carried  out measurements  of PAH in  a Puget  Sound  core  and found a flux



similar to what we've measured  at these urban areas.



     I now want to show several PAH  core  profiles.   Figure 6 shows data from



the first core that we ever did.  This was a core  from Buzzard's Bay which is



between Cape Cod and Rhode Is!and.  We measured PAH in three sections  which

-------
                                                                                                                           369
          PAH fluxes (in ng cm   yr~ )  to sediments  from S remote  sites In the  Northeastern United States for  3 age
Intervals:  present, approximately 1950, and 1900:  and to sediments from 3 urban sites for 1940  to the present.
Buzzards  Bay data from Httes et al.  (1977), and 1n  sHu density estimated from oater data of Rhoads and Young (1970).
Pettaauamscutt River PAH data from Hites et al. TTSSOb), sedimentation rate from Goldberg et al.  (1977), and in situ
density estimated from data of Orr and Saints (1974).


Remote Sites
Lake Superior (IS)
0.02 cm/yr

Isle Royal e (IR)
0.09 cra/yr
Somes Sound (SS)
0.1 cm/yr

Had lock Lower Pond (HLP)
0.07 cm/yr
Coburn Htn. Pond (CMP)
0.3 cm/yr

AVERAGES


Urban Sites
Boston Outer Harbor
0.1 cm/yr
Buzzards Bay, Mass
0.3 cm/yr
Pettaquamscutt River
0.3 cm/yr
AVERAGES
•includes all CjgHjj 'son


Interval
1955-now
1930-1955
1870-1920
1974-nm
1951-1955
1960-no«
1940-1960
I860- 1940
1950-now
1920-1950
1975-no*
1943-1947
1898-1901
present
•» 1950
•* 1900

1900-non

1940-now

1940-now


in
situ
dens.
0.55
0.55 .
0.55
0.33
0.32
0.43
0.52
0.51
0.1?
0.11
0.036
0.057
0.057
.
.
-

0.93

0.3

0.16

-


Chen
0.3
0.2
0.06
0.4
1
2
4
0.4
2
0.3
2
8
0.8
1
3
0.4

24

18

46

30


anth
0.03
0.02
0.004
0.01
0.05
0.2
0.4
<0.02
0.1
0.04
0.2
0.5
0.07
0.1
0.2
0.03

5.6

2

5

4
ers except perylene

C,
phen
0.3
0.2
O.OB
0.5
2.5
1
4
•0.2
2
-
4
12
1
1.5
4.5
0.4

17

.

36

25
From:


fluo
i
0.9
0.2
0.4
1
5
8
0.4
4
0.3
4
11
0.5
3
4
0.4

37

53

93

55


pyr
0.6
0.5
0.1
0.3
0.7
4
5
0.4
3
0.2
3
8
0.3
2
3
0.3

39

48

93

55
Gschwend


b(a)a
0.3
0.3
0.07
0.2
0.2
2
3
<0.05
0.6
0.04
0.7
3
0.2
O.B
1.5
0.1

19

37

42

30

chry*
tri
1
1
0.3
0.8
0.7
2
4
<0.2
1
0.1
2
6
0.9
1.5
2.5
0.2

23

37

42

35
& Hites,


b(e)p
0.9
0.9
0.2
0.8
0.9
2
2
0.2
0.8
0.1
2
7
0.4
1.5
3
0.5

14

.

.

•v25
1981


b(a)p
0.4
0.3
0.07
0.2
0.2
2
2
0.2
0.6
0.06
0.7
4
0.1
0.8
1.5
0.1

17

140*

130«

•v30

                                                                                         Total relative un-
                                                                                substitmed   PAH   abun-
                                                                                dance  observed  in  three
                                                                                dated sections  of a  sedi-
                                                                                ment  core from Buzzards
                                                                                Bay. Massachusetts  (open
                                                                                circles),   and   calculated
                                                                                PAH  production  (closed
                                                                                circles)  as  a function of
                                                                                time.

-------
                                                                           370
were dated by lead-210 so we knew to what year  these  sections corresponded.
In 1850, we found  very 1 ow PAH concentrations (about  7% of the maximum).  At
the turn of the  century, we  saw the maximum concentration, and  in about 1972,
we found PAH were still  near the maximum.  Our probl em was to ex pi a in  this
1 eve! ing off at 1900.  From the coal use pattern, factoring in a 1 ittl e bit
due to oil, we calculated an estimated production of polycyclic  aromatic
hydrocarbons.   These calculated values are  shown  as  the  curve labeled
"Production" in  Figure 6,  and they agreed we! 1  with the PAH measurements of
the sedimentary  record.
     We  did cores  at  other  locations.  Figure 7  is the PAH profile for a core
taken from  the Pettaquamscutt  River.  We were  able  to do this location through
the good graces  of Ed  Goldberg at Scripps who had  dated this core using lead-
210.  One finds  a  low, but relatively constant level, of PAH up to 1900, a
rapid increase between 1890  and  1920,  and a  subsurface maximum corresponding
to 1950.   This was  a very good core because it is  from an anoxic basin  of the
Pettaquamscutt River.  The  water on the bottom of this  basin is saline and has
been anoxic for some time,  and thus,  there is  no bioturbation.  The other data
plotted  in  Figure 7 as open circles are benzo[a]pyrene concentrations in a
core from the  Grosser PI oner Sea  in  Europe.  This core  also shows a subsurface
maximum  in  1950  and agrees well with our data  from the Pettaquamscutt River.
     Let's  look at a few  other locations.  Figure 8, top left,  shows data from
the Mountain  Pond  near Coburn Mountain  in Maine. The date (time)  scale was
based on lead-210.  The core  profiles  of three compounds  (benzo[a]pyrene, the
sum of chrysene and triphenylene, and pyrene)  are plotted.   These all  parallel
one another.   In  fact, we  almost always  see that  the concentration  ratios of
the different PAH  stay constant as one goes down  a core.  This convinces us
that there is  no  degradation.  If there were  some  degradation,  some of these
compounds would  be changed relative to others.   In  all these  cores (see Figure

-------
                                                                                                    371
             ~  I3r
             a  12'
O)
o
3
(A
E
o
=>
CJ
0
a
c
X
Q_
|

II
10
9
8
7

6
5
4
3
2
1
e
.' i '« -
'' 1 •
' i ' ^^~~
'

2.4
2.2 _
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2.0 |
o
/ : • H'-e"
II, I 01
• i \ f -1
"~"-s-^ \ / -
1 ,' \ '
i i \ ,'
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/ ? —
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-i- — T — ""^-i — — • : .,1,1.
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1.4 1

1.2 a
1.0 S
to
0.8 |
0.6 .E
ft
O
0.2 m
                 1820  1840  I860  I860   1900  1920  1940  I960  1980
                                    Year o' Deposition

      Total PAH abundance (see Table 11 in the various Pettaquamscutt River sediment core sections
vs date of deposition (horiponial bars, left scale): benzo[a]pyrene abundance in the Gosser Ploner Sea
                 (GRIMMER and BOHNKE. 197S) vs date of deposition (®. right scale).

               From:  Hites  et  al., 1980
                Concentration  Ing/pn dry scdnwnt)


           n          ZOO	400	600
       t
       &
          20
          30
                       Coburn Mountain Pond, Maine
   Concentration (ng/gm


n     TO   300    300   tOO   500
              Concentration  Ing/gm  aVy c*dan»ntl

                      SO         100
                                                            Concjntroliuii Ing/gm  *y Mdrantl
                                                                  SO
              H0     Lake Superior, Michigan
                                                      10
                                                       S ^.BB
             Somes Sound, Maine
           PAH profiles in four sediment cores. Symbols: A benzo(a)pyrene; O chrysene and triphenylene;

                                               pyrcne    From:  Gschwend &  Hites,  1981

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                                                                            372
8),  we  see  a  subsurface maximum at 1950.   Figure  8,  lower  right, presents PAH
data from the  Somes Sound, Maine,  core.   There's a subsurface maximum at  1950,
and a raise  from background  at  about the turn of the century.   Figure 8,
bottom left,  gives  PAH core profiles-for a site  in Lake  Superior which is
interesting because this site is more  upwind from the major midwestern sources
of combustion than is Maine.  We  see  an  indication of  a subsurface plateau.
In this case, we  don't  see  the surface concentrations drop off as much as
we've seen  in other locations, but we do see an increase at the turn of the
century.
     The only other PAH data from a dated sediment core are from a paper by
Prahl  and Carpenter  (1979) of the University of  Washington.   They  analyzed  a
core from Oabob Bay which is a bay on the southwestern side of Puget Sound.
These authors  found  profiles looking  very much  like what  we've seen before.
Figure 9 shows their data for benzo[a]pyrene and fl uoranthene.  There  is an
increase  at the turn of the century and also the 1950 maximum.  Very recently,
Sates et_ _aj_.  (1984) have published a PAH  core profile from  another location in
Puget Sound;  it  too looks similar to these profiles (Figures 7 to 9).
     There  are two features  of  polycyclic aromatic  hydrocarbon profiles which
are constant.  One is the increase at  the turn of the century  and the other is
the subsurface maximum at 1950.  Why the  increase in  1900?  Because that's
when coal  use  increased dramatically.   This has been discussed above.  Let me
now address the maximum at  1950.  Clearly coal  use did not  maximize  in  1950.
Coal use for  all  practical purposes has been constant during the  last 70
years.   Factoring  in  petroleum  doesn't help because that increases  since  1950.
We need some  way  of causing PAH  to go down  starting in 1950; putting  more
fuels into  the equation doesn't  help.  Better emission controls on large scale
burners  of  coal  don't  help  us  either.  Emission  controls really didn't   start

-------
                                                                                             373
                                     P4H IN DAB(» 9A« SEDIMENTS
                                 r:    4c    co   K    we
                              Profiles of three PAH concentrations with depth in
                         a Dabob Bay sediment core. Approximate ages of the sub-
                         surface maxima and deepest sediments based on 2>0Pb
                         measurements are given on the diagram. Average porosity
                         for the sediment core is 83°0 (range: 92°cr 0-1 cm: 79°,.
                                          29-30 cm I.

                         From: Prahl  and  Carpenter,  1979
      Residential   Heating   by  Fuel   Type
8O--
OO--
4O--
3O--
ZO--
10--
              193O        194O        195O        I960       197O        198O
                                             Year

-------
                                                                           374
in 1950,  and  it's  also hard for me  to  imagine them having that large an
effect.
     The answer to  thi s probl em begins by remembering Figure 2 which showed
there were a lot of polycyclics coming from the burning of  coal  in homes.
Figure 10 presents  data on residential heating  by fuel  type.   In  1930,  about
35% of all the  residential heating in  the U.S. was from wood and about  65% was
from coal.  Thus, only  two fuels were  used  to heat homes in the 1930's.  Let's
look at the other end of  the time  scale.   Today, home heating is about 65%
from natural  gas.   Oil  has been decreasing  since  1960  as  people converted to
other fuel types (mostly  electricity).   There is  very  little  coal  used  today
for home heating.   In fact, today wood  is ahead  of coal.  Thus, one of  the big
sources of polycycl ics has been el iminated since the 1930's.  It had been a
1 arge source, not  in terms of the amount of coal burned, but in the terms of
the inefficiency with which that coal has been burned.   All of these badly
maintained, hand stoked,  home coal burners emitted  large amounts of  PAH and
soot; that source has been completely  turned off  starting in  1930-1940.   It's
been replaced by natural gas which produces almost no  polycyclics, by oil
which produces  some  PAH  but  not nearly  at the rate that coal does,  and by
electricity which  is  the product of large  coal fired  power plants which
produce  few polycyclics.  We believe this trend away  from coal as a home
heating  fuel  accounts for the PAH decrease since 1950.

Research Recommendations
     We  need  more cores from more lakes.   We  could  then  develop a better and
more quantitative correlation between  polycyclic  fluxes and fuel  usage.  More
 lakes would also allow us to expand the regional  data  base of  fluxes.  At the
moment,  we only  have  fluxes  for two regions:  the  upper Great Lakes and Maine.
We need  to determine  if these fluxes are  correct  for other remote  regions.

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                                                                            375
References



Bates, T. S.; Hamilton,  S.  E.; Cl ine,  J.  D.  (1984)  Vertical  transport and



     sedimentation  of  hydrocarbons  in the  central main  basin  of  Puget  Sound,



     Washington.  Environ. Sci. Technol.  18,  299-305.



Gschwend,  P.  M. and Hites, R.  A. (1981) Fluxes of PAH  to  marine  and  lacustrine



     sediments in  the northeastern  United  States.  Geochim.  Cosmochim. Acta,



     45,  2359-2363.



Hites,  R.  A. ei_ a 1.  (1980) PAH in an  anoxic  sediment  core from the



     Pettaquamscutt  River (Rhode  Island,  USA).   Geochim. Cosmochim. Acta, 44_



     873-878.



National  Academy of  Sciences (1972) Particulate polycyclic  organic matter.



     National  Academy  Press:  Washington,  D.C.



Prahl , F.  G. and Carpenter,  R.  (1979) The  role  of zooplankton fecal  pellets in



     the sedimentation of PAH in  Dabob Bay, Washington. Geochim.  Cosmochim.



     Acta.  43,  1959-1965.

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                                                                      376

CARBONACEOUS PARTICLES (SOOT) FROM FOSSIL FUEL COMBUSTION

Ingemar Renberg, Department of Ecological Botany, Umea University,
S-901 87  UMEA, Sweden
Combustion of coal, oil, wood and other kinds of organic matter generates
particles containing elemental carbon. Several types of particles are
formed,    both submicrometer sized and coarse particles. At least for
coarse particles their surface morphology and surface texture is indi-
cative of their origin. According to Griffin & Goldberg (1981) spheri-
city is a characteristic of particles from fossil fuel burning and the
fine surface structure makes it possible to distinguish between partic-
les derived from coal and oil. Wood and also coal burning produce
elongate particles which often display the fine details of plant cellu-
lar structure (Fig. 1).

No consistent nomenclature exists for carbonaceous particles and a
large number of terms have been used. In this paper they will be called
soot.

Soot particles are released into  the atmosphere along with  other pollu-
tants generated at fossil fuel combustion. The amount emitted depends on
several things, such as type of fuel, type of combustion system, cleaning
devices etc. In the atmosphere the lifetime of these particles are con-
trolled by several factors. The particle size is very important. The
residence time of fine particles is usually longer than of coarse par-
ticles. But all particles will sooner or later return back to the surface
of the earth, where they are deposited everywhere.

Rather few seem to have thought about what happens to all these soot
particles. Due to the elemental carbon in the particles, which is very
resistent to degradation, they are preserved in soils for a long time
and in lake sediments forever.

The soot particles in sediments form a stratigraphic record that shows
the history of the deposition of pollutants from fossil fuel combustion.
This was first shown by Griffin, Goldberg and co-workers in their study
of a sediment core from Lake Michigan (see e.g. Griffin & Goldberg 1983).
They prepared and analysed the sediment according to the scheme shown in
Fig. 2. In their charcoal (all kinds of elemental carbon particles were
included) content diagram from L. Michigan, Griffin & Goldberg (1981)
discerned four different sections (a-d), see Fig. 4, and drew the follow-
ing conclusions:

(d) prior to 1900 the majority of the particles were elongate-prismatic
    in shape, with many showing woody cellular structures,

(c) chis is a transitional period with an increasing abundance of
    spheroidal particles indicating a coal source,
(b) smaller amounts of elongate-prismatic particles and more porous
    spheres from coal combustion, and from about 1950 also particles
    derived from oil combustion,

-------
                                                                      377
(a) after 1960 the charcoal concentration decreased probably due to
    improved cleaning techniques.

We have made soot particle analysis of lake sediments from Sweden.
We have prepared the sediment in a similar way as Griffin & Goldberg
with H202, although usually not dissolved the silicates with HF, and
furthermore, actually counted the number of spheres with a stereomicro-
scope. The method is described by Renberg & Wik (1984a) and is schema-
tically shown in Fig. 3. When using this method it is possible to count
spheres (Fig. 6) larger than about 5-10 ym.

Results from Lake Granastjarn, N. Sweden, are shown in Fig. 5 (left).
A core of the varved sediment was sampled with the crust-freeze corer
and was sub-sampled quantitatively to allow calculation of annual net
accumulation values of soot spheres to the lake bottom (cf. the presen-
tations about freeze coring and varves in chronology). When comparing
the results from this lake with the results from L. Michigan (Fig. 4)
the shapes of the two figures turn out to be very similar.

Lake Granastjarn is situated in an area which was industrialized rather
late. Despite that, there was   soot deposition during the 18th century.
At the middle of the 19th century there was a slight increase in the
soot deposition. This is the time for the so-called industrial revolu-
tion in N. Europe. A marked increase in the soot deposition took place
about 1950 due to the industrial upswing after the second world war when
oil combustion really increased in extend. There was a peak in soot de-
position around 1970, just before the "oil crisis".

The Swedish coal and oil consumption is also shown in Fig. 5 (right).
This curve is probably typical for many European countries. There are
similarities between the soot deposition in L. Granastjarn and the con-
sumption of coal and oil in Sweden.

Several things justify more research about soot in sediments.

1. The role of carbonaceous particles in the atmosphere.  The history of
   the elemental carbon pollution of the atmosphere, recorded in sedi-
   ments, is worth studying because: elemental carbon has a significant
   impact on visibility, it plays a role in atmospheric chemistry,and as
   it absorbs light may have some potential for altering the climate
   (Wolff 1981).

2. Soot - metal pollution. Heavy metals deposited from the atmosphere
   derive from several different sources, of which fossil fuel combus-
   tion is important for some metals (Pacyna 1984).

   In a sediment core from L. Michigan, Goldberg et al. (1981) found
   that concentrations of several metals covaried with the concentration
   of charcoal from coal, oil and woodburning (Fig. 7). Of course, that
   does not necessarily mean that soot and metals are closely related.
   They might both be indications of the general increase of air pollu-
   tants during this century.

3. Soot - PAH. See summary of presentation by Ron Hites.

-------
                                                                      378

4. Soot - acidification. It is likely that the soot particle record to
   some extent reflects the history of acid precipitation. The best
   correlation must be expected between submicrometer sized particles
   and acid substances. Ogren & Charlson (in print) have in fact been
   able to demonstrate a significant correlation between wet deposition
   fluxes of excess sulphate and elemental carbon in rain water samples
   collected in Sweden. Coarse particles (>5 ym) were not included in
   their analysis. But can we expect to find a correlation between
   coarse soot particles like the ones we have analysed and acid depo-
   sition? Probably, because there is likely to be a relationship bet-
   ween the deposition of coarse and fine soot particles. In the acidi-
   fied Lake Girdsjon in Southwestern Sweden we have made both a soot
   particle and a diatom analysis (Fig. 8). The pH curve inferred from
   the diatoms is more or less a mirror image of the soot particle dia-
   gram. The pH value started to decrease concomitant to the marked
   increase in the soot particle deposition.

5. Soot-paleomagnetism. See summary of presentation by Jan Bloemendal.

6. Soot as a dating tool. In Sweden (and Europe) the history of fossil
   fuel combustion as recorded by statistical data,and hence the influx
   of soot to lake sediments, shows some characteristic points;

   a) the middle of the 19th century - the industrial revolution with
      increased coal burning,
   b) about 1950 - the industrial upswing after the war with increased
      oil combustion, and

   c) about 1970 - the peak in oil combustion before the oil crisis.

   As pointed out earlier in this paper these three points are discern-
   able in the varved sediment of L.  Granastjarn. One model for "soot
   dating" is to determine the soot content at different levels of a
   non-varved sediment core and try to identify these points or other
   local points of marked change of the soot curve (Renberg & Wik 1984b).
   Of course, there are local and regional variations in the soot fall-
   -out history. Therefore, it is recommendable, or necessary, to
   establish local soot fall-out chronologies before trying to make any
   detailed soot datings.

   Fig. 9 shows the results of an attempt to show that soot dating really
   works. Lake Koltjarn has a varved sediment and Lake Omnesjon not.
   The soot concentration curves from the two lakes are rather similar
   in shape and three points (about 1930, 1950 and 1970) can be identi-
   fied rather easily.
Recommendations for research

   Reliable methods for quantitative analysis of different size fractions
   of soot particles should be developed.

   The behaviour of soot particles in lake water, e.g.  the pathways
   from the lake water surface to the sediment should be studied.

   The correlation between soot in sediments and sulphur,  nitrogen, PAH,
   magnetic parameters and certain heavy metals should  be  studied.

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                                                                      379
References

Goldberg, E.D., Hodge, V.F., Griffin, J.J., Koide, M. & Edginton, D.N.
    1981. Impact of fossil fuel combustion on the sediments of Lake
    Michigan. - Environ. Sci. Technol. 15, 466-471.

Griffin, J.J. & Goldberg, E.D. 1975. The fluxes of elemental carbon in
    coastal marine sediments. - Limnol. Oceanogr. 20, 456-463.

Griffin, J.J. & Goldberg, E.D. 1981. Sphericity as a characteristic of
    solids from fossil fuel burning in a Lake Michigan sediment. -
    Geochim. Cosmochim. Acta. 45, 763-769.

Griffin, J.J. & Goldberg, E.D. 1983. Impact of fossil fuel combustion
    on sediments of Lake Michigan: a reprise. - Environ. Sci.  Technol.
    17, 244-245.

Ogren, J.A. & Charlson, R.J. Paper in print in Tellus.

Pacyna, J.M. 1984. Estimation of the atmospheric emissions of  trace
    elements from antropogenic sources in Europe. - Atmos. Environ. 18,
    41-50.

Renberg, I. & Wik, M. !984a. Soot particle counting in recent  sediments;
    an indirect dating method. - Ecol. Bull, (in print).

Renberg, I. & Wik, M. 1984b. Dating recent lake sediments by soot par-
    ticle counting. - Verb. Internat. Verein. Limnol. 22, xx-xx.

Smith, D.M., Griffin, J.J. & Goldberg, E.D. 1975. Spectrometric method
    for the quantitative determination of elemental carbon. -  Anal.
    Chem. 47, 233-238.

Wolff, G.T. 1981. Particulate elemental carbon in the atmosphere. -
    APCA Journal 31,  935-938.

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                                                                                                            380
                            MICROSOPIC    SURFACE  TEXTURE
                                                                                           ETCHED,
                                                                                         CONVOLUTED,
                                                                                           LAYERED
                                                     Fig. Hal
                                  MICROSCOPIC  SURFACE TEXTURE
                                     SMOOTH
 ROUGH, IRREGULAR,
PITTED or CELLULAR
  ETCHED,
CONVOLUTED,
  LAYERED
          ELONGATE
          PRISMATIC
UJ
Q.
I
1/5
                                       COAL
                                       WOOD
       WOOD
       COAL
                                       COAL
                                       WOOD
       COAL
       WOOD
     OIL
                                                      Fig. l(bL


              u«n cff charcoal pjrticlc* According lo their shapes and surface icxlures. The "-hapci (\ernc3l u*i«.l arc \icwrd under 1000 x mj^nificjiion and the
                              surface icxlurn (hori/onial atisl arc oh».cr\rd under >HOO * m-j£nifn.~di»on.
         Fig.  1.    Figures  from Griffin  & Goldberg  (1981).

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                                                                 381
               OVEN DRIED SEDIMENT

                       I
               OXIDIZING WITH H2°2 + KOH
                       I
               LEACHING WITH HCI

                       1
               DIGESTION WITH HF

                       I
               LEACHING WITH HCI

                       4
               OXIDIZING WITH H2O2 + KOH

                       I
               LEACHING WITH HCI

                       *
               THE RESIDUE IS OVEN
               DRIED AND  THE CARBON
               CONCENTRATION DETERMINED
               BY INFRARED ASSAY
Fig.  2.  Schematic description of  a method for charcoal analysis  in
        sediments by Griffin & Goldberg (1975) and Smith et al.  (1975)
        This method has been slightly modyfied recently (Griffin &
        Goldberg 1983).
               OVEN DRIED SEDIMENT

                       I
               OXIDIZED  WITH »2°2

                       I
               SUSPENDED IN H20


               AFTER HOMOGENIZATION
               A SUBSAMPLE IS POURED
               INTO A GLASS PETRI DISH

                       I
               EVAPORATION AT ROOM
               TEMPERATURE

                       I
               THE NUMBER OF SOOT
               PARTICLES IS DETERMINED
               BY  COUNTING UNDER A
               STEREOMICROSCOPE
Fig. 3.   Schematic description of a method for counting soot spheres
         in  sediments by  Renberg & Wik  (1984a).

-------
                                                                                           382
                   cm
                         LAKE MICHIGAN BOX  CORE  LM-780914
                               See d
                                                     See b
                                         Set c
                       o               c :              020
                              •/. CARBON  by  WEIGHT  >38^
    5CV1"
         Charcoal pnrticla in Core LM 780914 collected September 14. 1978 Tram southeastern Lake
     Michigan a( 43 WN and H6J22'W. The scanning electron micrographs show the particle morphologies
     common to four periods: (at The 0-8 cm interval is representative or the particles in the sediments ol' the
      post I960 period; lb| 12-Ucm, 1930-1960: Id 27-28cm. IVOO-1930. and Idl 30-31 Drc-1900 ocriod.

Fig.  4.   From  Griffin  & Goldberg  (1981).
  0)
  e
  o
  o
  4)
  h»
  fl

  E
  o
  <0
  ®
           Lake Granastjarn

           soot particle deposition
            no  m"2yr1
1980
1970

1950

1930
1910

1890

1870
1850

1830

1810

1790
                        zoo ooo
                                        coal & oil consumption
                                        In  Sweden

                                        metric tons • 106
                                400 OOO  0    1O    20    30   4O
    Fig   5    The  annual net  accumulation  of  soot  spheres in the varved
                sediment  of  L.  Granastjarn  (left)  and  the  Swedish  coal and
                oil  consumption (right).

-------
                                                                      383
Fig. 6.  A soot sphere from a lake sediment.

-------
                                                                                            384
                                                The charcoal  (soot)  concentration  in the
                                                L.  Michigan core.  This figure  is re-drawn
                                                from Fig. 2 in Griffin &  Goldberg  (1981)
                                                to  make  the comparison with the figures
                                                below easier.
                             IK coee (.'**).
       YEAR
       I'JOO
                                                                             JO  «0  JO  ?0  10
                                                                              DEPTH IN CORE (cm)
                                                    50  «O  SO   20  10
                                                    DEPTH IN  CORE (cm)
60  50  40   30  ?0  10
    DEPTH IN CORE (cm)
60  5Q   40  30  20  fQ
   DEPTH IN CORE (cm)
60  JO  «0  SO  20  IO
    DEPTH IN CORE (cm)
50  40   50  !0  10
DEPTH N CORE (cm)
                 Metal concentrations (on a dry-weight basis) as a (unction of depth in the Lake Michigan core.

          Fig.  7.   Figures  from Griffin  & Goldberg (1981).

-------
                                                                     385
                          inferred from  diatom

                         /analyses  (index B)
            6 -
        r
        a
TO   5

5

0)


nj
            4 -
   r1800
                                          - 10 ooo
                                       1979
                                                      c
                                                    W Q)
                                          - 30 OOO  JH E
                                            "'•5


                                          - 20 000   w
                                                    a >,
                                                    o w
                                                    SE
                                                      CO
                                                    o o
                                                    c a.
Fig.  8.   The  soot  particle concentration in a core from L.  Gardsjon

         and  the pH  history of the lake inferred from the subfossil

         diatom record of the sediment.

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                                                                                    386
                   • GRANASTJARN

                    KOLTJARN &
  LAKE KOLTJARN

  SOOT SPHERULES (no. g'dry «ed.)

  0       1 000      2 000
                             3 000
o 	 .
10 ~ 	 	 	 	 i
E , ... — ,
z
£ i. "...— ~...IZ
UJ
- 1982
- 1070
(• 1974
!- 1968
j-1963
|-1958
L1953
[-1948
1-1943
r 1938
I- 1933
I . _
Q
Z
UJ
20 --
                               (-1928
                               -1900
                                              a
                                              UJ
                                              o
                   LAKE OMNESJON

                   SOOT SPHERULES (no. g'dry sod.)

                   0        500      1 000
                                                                              1 500
                                                10 -1	
                                                   1	
30 -
-1858


1-1749
    Fig.  9.   The  soot particle  concentration  in the varved  lake sediment

              of L.  Koltjarn  (left) and  in the  non-varved L.  Omnesjon  (right)

-------
                                                                   387
      Accumulation and Processing o-f Chlorinated Hydrocarbons  in



    Lake and Bog Sediments: Relationship to Atmospheric Deposition
                                  by
S.J. Eisenreich, R. Rapaport, N. Urban, P. Capel,  B.  Looney,  J.  Baker




                  Environmental Engineering  Program




             Department of Civil and Mineral  Engineering




                       University of Minnesota




                        Minneapolis, MN 55455
                   Contribution to  the  Workshop  on




           "Progress and Problems in  the  Paleolimnological




           Analysis of the  Impact of  'Acidic  Precipitation'




              and Related Pollutants  on Lake Ecosystems"








Introduction




     Atmospheric transport  and deposition play an  important  role in




distributing trace organics of anthropogenic  origin throughout the




aquatic and terrestrial environment.  Trace organics of interest in




this presentation are  chlorinated hydrocarbons such as PCBs,  DDT-group




compounds, chlorinated hexanes  (BHC's), hexachlorobenzene and




toxaphene.  These compounds exhibit similar chemical/physical




properties of low aqueous solubility  and  vapor pressure,  high

-------
                                                                   388
partition coefficients with respect to octanol, solid  and  aqueous
organics and lipid phases of organisms., and long chemical  residence
times in the environment  (i.e., persistent and re-Fractory) .   They  are
transported through the atmosphere primarily as gases  or attached  to
•fine particles  «2 urn mmd).  The primary removal mechanisms  are
unproven but thought to be scavenging o-f organic-laden aerosols  by
precipitation and dry deposition, especially of the  large  particles.
The role o-f air-water transport o-f the gas phase organics  is unclear,
although volatilisation is an  important loss process for lakes and
oceans.  Once deposited in a lake, the hydrophobic organics  bind
preferrentially to organic detritus and ultimately are deposited in
bottom sediments.  The proportion of trace organics  in the dissolved
phase depends on the concentration and composition of  particles.   For
organics having log Kow > 3.0  and S3 in the range of 1 to  100 mg/1 , 75
to  1007. is apparently in the dissolved phase based on  filtration.
Even so, small  and large lakes exhibit fine particle residence times
less than one year, and trace  organic residence times  of 2 to 4  years.
Thus, sediment  profiles may preserve, in the absence of major
bioturbation, the historical input pattern, although sediment focusing
probably alters the actual magnitude of inputs.
     The objectives of this presentation are to present the  historical
record of CH input to lake and bog sediments,  and to provide
information how organic profiles may be useful  in dating sediment
cores.
Discussion
Lake Sediments:
     The historical record of  CH deposition to lake  sediments has  been
obtained for a  variety of  trace organics.   I will present  information

-------
                                                                   389
on cores taken -from Lake Ontario in a high sedimentation rate
environment and in Lake Superior having slow rates of sediment
accumulation.  In this -first section, the Lake Ontario cores will
be discussed in some detail.  Box cores taken in eastern Lake Ontario
were dated with both Pb-210 and Cs-137 by J.A. Robbins, and mixing
parameters and sedimentation rates determined -from the rapid steady-
state mixing model which adequately describes Pb-210 behavior (Table
1) .
     The Pb-210 pro-files are consistent with mixing depths of 3 to 4
cm in E-30 and 5-6 cm in G-32, corresponding to an intrinsic
resolution 
-------
          Table 1.  Lake Ontario Sed1ment_Core_Data
                                                                     390

Long/Lat ? ,
R (gem *yr ')
W (on yr'1)
S (cm)
S (g/cm2)
*V(yr)
E-30

.0443 ± .0027
0.2
3-4
.50 ± ,08
11.3
6-32

.0795 ±
0.3
5-6
.92 ±
11.6


.0031


1.0

•V S/R

-------
                                                                               391
                                   TOTAL PCBs   ng/g

                                       400         800
                        10  A
              DEPTH  cm
                        15  -
                        20  ir
1981
1961 -
1941
1921 -
           TOTAL PCB FLUX  rig/cm  yr
               20        40
          TOTAL PCB  ng/g

                  400
1981
1961
                                          1941
1921
            Figure 1.  t-PO3 concentrations and fluxes in dated
                       sediment cores from Lake Ontario.

-------
                                                                   392




concentrations scale to the sedimentation rate.  Figures 2 and 3 show




the depth profiles o-f PCB, t-DDT, mirex and HCB in the two Lake




Ontario cores.  In these cores, mirex concentrations are about equal




and thus accumulation is proportional to sedimentation rate.  This




behavior is consistent with the hypothesis that mirex enters the lake




on particles via riverine sources; potential PCB delivery to both




sites occurs via settling particles -followed by dilution with




uncontaminated, erosional sediment.  The t-DDT peak occurs deeper in




both cores than the PCB or HCB peak, the age o-f which is probably




about I960 representing the period o-f peak usage in North America.




     For persistent hydrophobic organics, transport and fate are




dominated by associations  (sorption/partitioning) with the high




surface area, high organic content particles.  Thus, the total




quantity of organics in sediment cores differing in sedimentation rate




should be directly related to the ratio of organic carbon fluxes.



Figure 4 shows the relationship of accumulated mass of several




different organics in the two cores.  The data points cluster closely




along the line representing the ratio of the organic carbon fluxes,




and not  the mass accumulation rate.




     The penetration of PCBs to depths in both cores having ages prior




to the onset of production suggests downward migration in the sediment




cores.  As a test of this hypothesis and searching for evidence of  PCB




degradation, the ratio of tri-, tetra-, and pentachlorinated byphenyl




congeners to t-PCB versus depth was plotted.   Initially, Figure 5




shows that the penta-substituted congeners are lost  (degrade) at the




expense of the lighter congeners.  A more plausible explanation is




that the lighter congeners are diffusing in the porewater away from




the sedimentary peak leaving the heavier species behind.  This

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-------
                                                                    395
              Sedimentation Rat* • 1.89
                                  Organic Carbon
                                   Sedimentation Rat* • 1.44
                      Heplachlor Epoxld*

                    4-PCS
                 O
                 UJ
           2000  t-
                                      1000
                                     4000
1250
5000
 1500
6000
           ACCUMULATED MASS (ug/m*)  in  LO-8J  E-30
Figure 4.   Relationship of accumulated mass of several organic
            contaminants in two  Lake Ontario cores to mass and
            carbon  accumulation  rates.

-------
                                                                   396
scenario necessitates that PCBs and perhaps other organics  occur  at
measureable concentrations in porewaters,  These data  have  been
modeled assuming di-f-fusion is responsible -for the deep penetration
into the core by lower chlorinated species, yielding a tortuosity-
corrected di-f-fusion coe-f-ficient of about 10"* cmz/sec.   Table  2
documents the occurence of t-PCB occurring at concentrations  10 to 500
times overlying water values.  The cores -from Lake Ontario  have
demonstrated the differential mixing of sediment components, the
potential application of organic input functions to date cores, and
the mobility of trace organics in sedimentary profiles.
     Nine sediment cores collected in  1978 in the western and  central
basins of Lake Superior were dated with Pb-210 and analysed for PCBs
and DDT.  Surficial sediment concentrations  (0.5 cm) of  PCBs ranged
from 4 to 180 ng/g of dry dediment corresponding to estimated  recent
fluxes of 2 to 70 ug/ma yr.  Highest concentrations and  fluxes of PCBs
occur in the western arm of the lake nearest the urban areas of
Dulnth/Superior and the major source of sediment to the  lake - erosion
of red clay along the Wisconsin shoreline.  Levels are also generally
elevated in the central region of the  lake in the vicinity  of  Isle
Royale.  We believe this area may be impacted by atmospheric transport
from the upwind urban/industrial center of Thunder Bay,  Ontario.
Surficial FCB concentrations are higher than observed  by Frank et al
 (19SO), who reported values integrated over 3 cm, and  generally  lower
than observed for the other lakes.  Figure 6 provides  an example  of
concentration-depth profiles for selected sediment cores taken in 1978
in Lake Superior.  Fractionating the cores into ~ 0.25 cm segments  in
the upper few cm corresponds to a time resolution of ~6 years  for a
linear sedimentation rate of 0.04 cm/yr to 2.5 yrs for a sedimentation

-------
                                                                     397
                 Loke Ontario  - 1981
                        Core G-32
 3-CB  x   3
t-PC3   10
                                                         x»
                                               1 - PCS
                                             10  20  30
10  20  30  40   50
Figure 5.
 m_i_T
 Table
         PCB congener ratios  to t-PCBs in L081-G32:
         evidence for diffusion of lower chlorinated congeners.
        CB* In Pore Water of Great Lakes' Sediments
Pore Water
(ng/1)
Lake Superior
26
18
12
9-35
M
Lake Erie (HS-81)
72
35
1-5
Lake Huron (HS-81)
39
26
307
•\.l
Sediment
(ng/9)

5.0
7.9
7.8
9-19
M700

76
40
—

46
39
21
.»
KP
("9/9)P/
(ng/g/w

190
440
640

MO6

1060
1160
~

1180
1520
70
,106
Site
10

9BX-81
19BX-B1
31BX-81
2BX-81
Lake

0-2 em
2-4 on
Lake

0-2 cm
2-4 en
4-6 cm
Lake

-------
                                                398
Depth
 (cm)
                Total PCB(ng g"1)
                  70      I40     2IO
0

t-
4


8
10
0
2
4
6
8
m

I



,, 	 I



Site 1,1 Bx
1 i i

70 140 2!
, J 370


Site 2, 4Bx
i i
1CT7O
- IJ7 ( U
-1961
-1951
-1942
1933



0
4 f*\ ^m9
-1963
•1931
•1901



70 140 210
0, 	 . i 1QKQ
2

4
6
8
n




Site 5, 11 Bx
i i
'1938
'1874




            Figure 6. PCBs in lake Superior Sediment Cores

-------
                                   399
  Total  PCB (ng g"1)
       7      14      21








Depth
(cm)









u
2
4
6
8
10





Site 4, 8 Bx
i i

7 14 2
w
2
4
6
8
10




Site 10, 24 Bx
i i

35 70 10
0
2
4
6
8
m

i

i •
d

Site 11, 26 Bx
i i
                        .1967
                        -1959
                         1939
                         1919
Figure 6 contd.

-------
                                                       400
Total PCB (ng g ')
35 70 105
0
2

4
fi
VJ
8
10

	 1 	 »


I
j
[

Site 6, 13 Bx
i i

4 c\-rr\
.1972
-1967
-1961
-1955
-1950
"1944


70 I40 2IO
!
2
4
Depth
(cm) 6
8
10


J



Site 7, 15 Bx
i i

h1972
"1965
-1949
-1934
"1919



35 70 I05
Q, 	 • 	 • locrt
p
L-
4
6
8
m


j
1

Site 9,21 Bx
i i
-1940
"1902




Figure 6 contd.

-------
                                                                   401
rate of 0.1 cm/yr.  Pb-210 analyses of these sediment cores show
mixing depths o-f 0 to 4 cm, with most cores having values o-f 0 to  2
cm.  A mass accumulation rate of 0.04 cm/yr (lakewide average) with  a
mixing depth o-f 1 cm yields a time resolution o-f 25 years.
Application of various biological mixing models using Pb-210 as a
tracer suggest a low rate of mixing.  The detailed 'shape of the PCB
profile in the upper few cm argues against significant mixing.  Figure
7 shows the historical profiles of PCBs in three sediment cores
differing in mass accumulation rates by > two times.  In nearly, all
cores examined, the onset of elevated concentrations occurs near 1950,
peaks in 1972-73, and decreases in the last decade.  The date at which
PCB levels increase most rapidly is about the same in all the Great
Lakes.
     The sedimentary profiles of PCBs in Lake Superior are in close
agreement with the decrease in PCB residues measured in Lakes Michigan
and Superior coregonids and chubs and the U.S. sale of PCBs.  The
decrease in PCB concentrations in major fish species demonstrates
clearly reduced loading to the lakes as a result of improved disposal
practices.  The difference in time between the peak in PCB sales and
the peak in sedimentary concentrations corresponds  (fortuitously)  to
the average residence time of PCBs and DDT determined from mass
balance calculations - about 2 to 4 years.  We conclude that the FCB
profiles in Lake Superior sediments record the historical input
pattern.  Furthermore, the sedimentary burden responds rapidly to
decreased loading, on the order of the chemical residence, time of  the
lake.   Implicit in this discussion is the necessity to collect
undisturbed sediment cores and have the ability to segment the cores
with appropriate time resolution.

-------
1980
    0
1970
1960
1950
1940
    0
    PCBs in Fish
            g"1-)
            4
             PCB Sales
a L.Michigan Coregonids
o L. Michigan Chubs
+ L. Superior  Coregonids
    10
20
30
        Domestic PCB  Sales
            (103 Kg yr"1)
                8
40
                                            PCBs in L.Superior  Sediments
                0
0
                35
           (ng g"1)
               70
        105
 140
                                                                         B
                                          + S-78-1
                                          o S-78-6
                                          • S-78-7
1 40
                                              (ng
280
                 Figure 7. Historical PCB Profiles in Three Lake Superior Sediment Cores
                        Comparison to PCB Sales and Fish Concentrations.
                                                                          O
                                                                          PO

-------
                                                                   403




Bog Sediments:




     Ombrotrophic mires or wetlands are referred to as bogs and




receive their hydrologic input entirely from the atmosphere; i.e.,



little or no groundwater or sur-face runoff.  Several peat cores -from




bogs in eastern North America have been collected and analyzed for




various chlorinated hydrocarbons.  We have concluded that hydrophobic




trace organics behave conservatively in the core, mimic the tentative




input function and provide both the shape and magnitude of the




atmospheric flux to these sites.  An example of particular interest to




us is the story evolving concerning purportedly new DDT inputs to




North America.




     DDT is perhaps the most effective and notorious pesticide




developed to date.  Its uses, benefits, and environmental hazards  have




been documented.  DDT was first introduced to the environment during




the latter stages of World War  II to combat typhus and malaria in  the




tropics.  Peak use of DDT in the U.S. occurred in the late  1950's  and




early 1960's, with peak U.S. production occurring in the early 1960's.




DDT was banned from use in North America in 1972, and concentrations




and fluxes of DDT and metabolites have decreased substantially since.




We believe that new DDT inputs  continue and may be increasing.




     When DDT is released to the environment after application to




fields usually by aerial spraying, or is allowed to migrate into




lakes, streams and coastal areas, it is transformed into metabolites,




most notable DDE and DD.  DDT is transformed into DDE in aerobic




environments and ODD is the first product formed in anoxic  systems.




DDE is a metabolic deadend in that it is stable to further




degradation.  However, ODD can  be transformed into other metabolites —




mostly hydroxylated and dechloroinated species.  The halflife of  DDT

-------
                                                                   404



in the environment has been estimated to be about 10 years, with much




variabibi1ity depending on conditions.




     As o-ften occurs in scientific endeavors, the discovery of this



potentially-injurious phenomenon occurred by serendipity.  We are




investigating the biogeochemistry of Sphagnum bogs in North America




through funding provided ny the National Science Foundation.  Sites of




study are restricted to ombrotrophic bogs which receive all of their




hydrologic and nutrient inputs from the atmosphere.  Therefore, these




systems are ideal for studying certain aspects of atmospheric




processes.  Bogs are characterized by low pH and basic cation




concentrations, and high organic carbon and color.  In attempting  to




determine the ages associtaed with various peat horizons, we




discovered that many elements or species which normally behave




conservatively in the profile did not.  Examples are the radionuclides




Cs-137 and Pb-210.  Dated profiles are needed to establish mass and




chemical accumulation rates, which presumably represent historical




atmospheric deposition.  It occurred to us that hydrophobic organics




such as DDT and PCBs might bind strongly to peat organic matter and




behave conservatively in the core.  Also, peat profiles should provide




horizons indicating the onset of DDT use in the environment,  its peak




use in the early 1960's, and the falloff following the 1972 ban.




Realistically, the 1960 peak might be the only feature that could  be




applied to the dating problem.




     To this end, peat cores were collected from Minnesota to Maine,




and north to Nova Scotia for study of biogeochemical processes, and




-four were were analyzed for t-DDT.  Figure S shows a comparison of the




DDT use and production curves to DDT accumulation rates.  The depth of




each core was 50 to 60 cm, and the core was segmented into 2.5 or  5.0

-------
U. S. PRODUCTION AND USE Of OPT

           Unit - K>*g
       29     90     79
                          no
     t-DDT ACCOM, (/ig/nAyr)
0           5
                         10
     I-DOT ACCUM. (jig/m'.yr)
0            I            2
1971-'
1964


1944
Year
1924

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1944.
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1924.

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1944.
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I-OOT ACCUM. l/ig/m'.yr) 1- DOT ACCUM. (/tg/m'.yr) 1- DOT ACCUM. (/ig/m'.yr)
0 3 10 o 9 10 0 10 21

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1944.
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=>,




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Figure 8.   t-DDT in Peat Cores from Eastern North America.
             Comparison to DDT Use  and Production Curves.
                                                                                                                 O
                                                                                                                 cn

-------
                                                                   406




cm sections.  The ages of the depth increments are derived  from  a




novel ash dating technique and Pb-210.  These pro-files  show a  peak




accumulation at about 20 years ago, and a dramatic decrease in the




early 1970's.  In some cores, t-DDT increases at the surface and in




others, remains at higher than expected levels.  Closer analysis o-f




the cores shows that >757. o-f the t-DDT in the sur-face peat  is




untrans-formed p,p'-DDT.  Remembering that little parent DDT ought to




be present at the sur-face -from historical use patterns,  then we  can




only conclude that recently-deposited species must, o-f  necessity, be




derived from new source(s).  This conclusion is supported by finding




largely parent DDT species in snow and rain in northern Minnesota.




     Figure 9 shows that present day fluxes of t-DDT, which is mostly




fresh DDT, are about 10 to 207. of the peak accumulations in 1960.




Since the ecological consequences of historical DDT use are well




documented, the increase of  DDT inputs via atmospheric  deposition to




North America is cause of some concern.  We hypothesise that the




likely source of new DDT is  material emitted into the atmosphere in




Mexico and Central America,  and delivered to eastern North  America  by




long range traport.  The meteorological pattern shown in Figure  S




makes transport of fresh DDT to North America as a gas  or aerosol  a




likely possibility.  It should be noted also that t-DDT profiles in




peat cores has evolved into  a rather useful technique for dating peat




cores.

-------
                                                                    407
                                           NORTH AMERICA
 PACIFIC OCEAN
                                                                    1
                                                              ATLANTIC
                                                                OCEAN
TOTAL
 DDT
       SURFACE
        CPEAK DDT
         T ACCUMULATION
       i
f°,p' +
\p,p'DDT
             I	i
                    yr
            Figure 9.  Recent and Historical DDT Fluxes to Areas in
                      Eastern North America.  Source of New and
                      Continued Input is Likely Mexico and Central
                      America.

-------
                                                                          408
References
1.  Eisenreich, S.J., Capel, P.O., Robbins, J.A., Bourbanm'ere,  R.,  Accumula-
    tion and diagenesis of chlorinated hydrocarbons In lake sediments.   1984,
    in preparation.
2.  Eisenreich, S.J.,unpublished data.
3.  Eisenreich, S.J., Johnson, T.C., Hollod, G.J., Geochronology of  PCB and
    DDT inputs to Lake Superior.  1984, in preparation.
4.  Petersen, J.C.,  Freeman, D.H.  1982.  Phthalate ester concentration varia-
    tions in dated sediment cores from the Chesapeake Bay.  Environ. Sci.
    Tech., J6, 464-469.
5.  Oliver, B.G., Nicol, K.D.  1982.  Chlorobenzenes in sediments, water and
    selected fish from Lakes Superior, Huron, Erie and Ontario.   Environ.
    Sci.  Tech., 16,  532-536.

Acknowledgments
    This  research is based on part on funding from the U.S. EPA, NSF and NOAA.

-------
                                                                           409

MAGNETIC MEASUREMENTS OF ATMOSPHERIC PARTICULATES AND OMBROTROPHIC


PEAT; A REVIEW




                          *
F. Oldfield, J. Bloemendal , L. Barker, A. Hunt, J.M. Jones, M.D.H Jones,


R. Maxted, N. Richardson, J. Sahota, Dept. of Geography, University of


Liverpool, U.K. and K. Tolonen, Dept. of Botany, University of Helsinki,


Finland.


* Present address - Graduate School of Oceanography, University of Rhode


Island, U.S.A.
     This contribution reviews research efforts designed firstly, to use


magnetic measurements to characterise and differentiate sources of


urban-industrially derived atmospheric particulate material; and


secondly, to use magnetic measurements to study the history and spatial


variation of urban-industrial pollution as preserved in recent


ombrotrophic peat deposits and lake sediments. In doing so, it attempts


to define the future role of magnetic measurements in acid rain and trace


metal deposition studies. Part of the rationale for the emphasis on the


use of ombrotrophic peat in the work reported here is that depositional


environments in which geochemical inputs are exclusively atmospheric are


clearly advantageous.


     The presentation is divided into four sections: The first reviews


the production of magnetic particulates by fossil fuel combustion and


illustrates the use of magnetic measurements in characterising urban


aerosols; the second reviews the stratigraphic and spatial record of


magnetic deposition as recorded in ombrotrophic peat; the third shows


that in certain situations lake sediments can record the deposition

-------
                                                                           410




history of industrially-derived magnetic material; and the fourth




outlines some future research priorities. Definitions of the magnetic




parameters referenced are given in Table 1.




                     SECTION ONE




     Figure 1 illustrates the process of fly ash formation in a




coal-fired power station. Raw coal is pulverised, producing particles of




~ 10-100 microns diameter. Further mechanical breakup yields particles of




~ 0.1-50 microns diameter (accounting for 99% of the final product).




Vapourisation, nucleation and condensation produce particles of ~ 0.1




micron diameter (accounting for only 1% of the final product). Sulfur




compounds, magnetic iron oxides and trace metals all become enriched




during this process and trace metals are further enriched in the magnetic




fraction.




     Figure 2 illustrates the production of ferrimagnetic material during




fly-ash formation. There are two main pathways: Firstly, with a short




combustion period and/or low temperatures, magnetite is produced from




pyrite framboids with little dimensional change or melting. Secondly,




with higher temperatures and/or a longer combustion period, pyrite is




oxidized eventually producing hematite, which dissolves in a Mg-rich




silicate melt, eventually yielding ferrous silicate and a Mg-rich




magnetite; then depending on the rate of cooling either stoichiometric




magnetite or eqimolar mixtures of magnetite and  maghemite are produced.




The ferrimagnetic grains are spherical in shape. Regarding their size,




production models and indicate that magnetic spherules generated by all




of the relevant industrial processes will be ~ 2 microns diameter or




greater. This is consistent both with their reported sizes and with their




magnetic properties. Spherule size is important, since magnetic




properties are highly dependent upon grain size. Their size is such that

-------
                                                                           411




they can be magnetically distinguished from generally much finer-grained




magnetic material of crustal/pedogenic origin.




     The relationship between magnetic oxides and heavy metals in fly




ash, industrial particulates and vehicle emissions is poorly understood.




Two schemes have been suggested (Figure 3): Firstly, ferrospheres in the




form of an Al-substituted ferrite accept transition metal ions by




isomorphic substitution. Secondly, condensation of volatilised trace




species occurs on particulate surfaces in cooler parts of the system.




     Where a single emission source is dominant, magnetic mineral




concentrations in samples taken using air samplers are often roughly




proportional to trace metal concentrations. Table 2 shows magnetic:metal




ratios of samples from the two Mersey tunnels in Liverpool, England. The




sampler used was an Andersson 2000 four stage cascade impactor mounted on




a high volume air sampler (20 CFM). The magnetic:metal ratios for the two




tunnels are quite similar. However, particle-size dependence of




magnetic:metal ratios may complicate this picture. Table 3 shows the data




from Table 2 broken down according to particle size. The 50% effective




cutoff diameters for impactor stages 1-4 are 7.0, 3.3, 2.0 and 1.1




microns. There is a tendency for higher magnetic:metal ratios to occur in




the coarser particle size ranges.




     Magnetic:metal ratios may vary considerably with particulate source.




Table 4 compares magnetic:metal ratios for the two tunnel sites with




those for particle-sized resuspended fly ash. The ratios for the fly ash




are several orders of magnitude higher.




     Different combustion processes give rise to particulate emissions




with distinctive magnetic characteristics as well as diferent




magnetic:metal ratios. Magnetic measurements alone or in combination with




measurements of metal concentrations can aid the identification of

-------
                                                                           412
aerosol sources in areas of mixed emission. This is illustrated in Figure

4 which compares the 'S' ratios of fly ashes from Hams Hall power station

in the West Midlands, England, with those of leaf samples from urban and

rural areas in Yorkshire, England, and the Mersey tunnel samples

referenced earlier. The tunnel samples, dominated by vehicle exhaust

emissions, are dominated by magnetite, while the fly ashes and leaf

samples have a significantly greater hematite component. This

relationship is independent of particle size.

     On a larger geographical scale, magnetic measurements can

differentiate dusts of urban-industrial origin from those resulting from

deflation processes. Figure 5 plots the susceptibility:Al ratio versus

atmospheric Al concentration for a suite of samples obtained from the

Mediterranean atmosphere by R/V Shackleton. Samples with the highest

susceptibility:A1 ratios are associated with the lowest atmospheric Al

concentrations. This relationship is interpreted as resulting from

varying degrees of dilution of a relatively highly magnetic

urban-industrially derived aerosol from the European mainland by crustal

material with relatively low concentrations of magnetic material, derived

from sources such as the North African arid zone.

     Figure 6 gives another example of the use of magnetic measurements

for aerosol source differentiation. The samples shown are fly ashes,

North Atlantic dusts and two sets of dusts from Barbados, a red-brown

coloured summer set, derived from the North African arid zone, and a grey

winter set derived from a more local source, in South America. The

gradient from high to low SIRM:ARM ratios reflects a declining proportion

of relatively coarse grained magnetic material of urban-industrial

origin, while the gradient from low to high values of frequency-dependent.

susceptibility reflects an increasing proportion of very fine-grained

-------
                                                                           413
magnetic material of inferred crustal origin. The diagram clearly




differentiates the fly ashes, dominated by relatively coarse magnetic




material, and the North Atlantic and Barbados dusts with a progressively




increasing proportion of very fine soil-derived magnetic grains.




     The main conclusion from this section is that irrespective of the




feasibility of directly estimating heavy metal concentrations from




magnetic parameters, the use of magnetic measurements to separate




particulate sources appears viable, Also, although no direct




sulfur-magnetic particulate link may exist the ability of magnetic




measurements to differentiate aerosol sources is clearly of considerable




value in the context of acid rain studies.




                         SECTION TWO




     Figure 7 shows plots of volume, specific and cumulative SIRM for a




series of short ombrotrophic peat profiles from Cumbria, England. At all




of these sites, and at many others studied subsequently, peaks in




magnetic concentration occur near the present day surface. At all of the




Cumbrian sites it is known from pollen-analytical evidence that the depth




of peat accumulated since 1800 AD seldom exceeds 20 cm. Likely sources of




magnetic input to these sites include local sources such as




Barrow-in-Furness and a steelplant at Millom, as well as extra-regional




sources such as the heavily industrialised areas of South Lancashire.




     Spatial variations in the concentration of magnetic material reflect




distance from industrial sources: this is the case for either peak




concentrations or cumulative deposition above the point of initial




magnetic increase. This is shown in Figure 8 which maps specific SIRM for




surface peat samples from the northeastern U.S. and eastern Canada. The




sites with highest values are located close to major sources of




industrial pollution. They are as follows: sites 2 and 3, Toivola Bog and

-------
                                                                           414




Ely Lake Bog, northern Minnesota, near the Mesabi Iron Range; and site 4,




Guilletville Bog, Sudbury, Ontario, located 12 km northeast of the




Sudbury nickel smelter and lying in the prevailing wind direction. Figure




9 maps the SIRM:ARM ratios of the same sites shown in Figure 8. The




pattern of variation of this parameter, with the highest values




associated with the most contaminated sites, is consistent with the




expected size range of industrially generated magnetic spherules.




     The effect of microtopography on magnetic mineral accumulation




within peat bogs is reflected in higher magnetic accumulation rates in




hummock sites than in pool sites; the differences are especially




pronounced at British sites.  This may result from the prefential




deposition of magnetic material on hummocks, but may also reflect the




dissolution of magnetic material in pools. Where pollen analysis has been




used as an independent test of the synchroneity of magnetic changes




between pool and hummock cores from the same bog site, initial magnetic




increases and subsequent changes in both concentration parameters and




normalised interparametric ratios are clearly synchronous. Examples are




given in Figures 10-12, which show SIRM profiles together with the




variation of selected pollen taxa from cores from Heathwaite Moss,




Cumbria, England, Axe Edge Moor, Derbyshire, England, and Ely Lake Bog,




Minnesota. At each site, comparison of the pollen curves between hummock




and pool sites indicates a high degree of synchroneity of the SIRM




stratigraphy.




     At several British sites there is a strong positive correlation




between magnetic mineral concentrations and those of Cu, Pb and Zn. Fe,




Mn, Cd and Ni correlate less consistently. Figures 13-14 show the results




of magnetic measurements and heavy metal analyses from two sites, Whixall




Moss, Shropshire, England, and Loch of Lowes, an ombrotrophic peat site

-------
                                                                           415




in Perthshire, Scotland. In each diagram the base of the most pronounced




increase in magnetic concentration is marked with a dashed line. At both




sites, the large increases in the concentration of Pb, Cu and Zn occur at




the same depth as the increase in magnetic mineral concentration. At Loch




of Lowes, the magnetic mineral-heavy metal relation is equally clear in




both pool and hummock cores.




     Where accurate dating is available, variations in the magnetic




stratigraphy of ombrotrophic peats correlate with the history of regional




industrialization. Figure 15 shows four superimposed magnetic profiles,




together with the mean (solid line), from Karpansuo Bog, situated in a




remote part of central Finland. An absolute chronology has been




established by the annual moss increment counting. The S1RM values have




been used to estimate magnetite accumulation rates. Accumulation rates




begin to increase above background levels from around 1860, and by 1900




the mean annual accumulation rates are 2 to 5 times the pre-1860 level.




However, the sharpest increase occurs just prior to 1950, and in all




profiles the maxima occur during the last 30 years. This mirrors the




relatively late spread of heavy industry to eastern Finland during the




post-war period. Work in progress on the moss increment dating of




magnetic profiles from hummocks in ombrotrophic peat sites in Maine and




New Brunswick indicate a trend of declining magnetic accumulation rates




for the last 30 years, possibly reflecting the greater use of oil




relative to solid fuel in the U.S. over the last few decades.




      'S' ratios reveal distinct temporal differences in magnetic




grainsize and/or mineralogy within ombrotrophic peat sites. At several




sites, the earlier industrial phases appear to be characterised by the




production of magnetic material with a higher hematitermagnetite ratio




than modern phases. Figures 16-17 show examples from Ringinglow Bog, near

-------
                                                                           416



Sheffield, England, and Heathwaite Moss, Cumbria, England. At Ely Lake




Bog, Minnesota (Figure 18) a similar magnetically 'hard' component is




associated with the earlier stages of iron-ore mining the Mesabi Range.




     The main conclusions from this section are that although we cannot




demonstrate that the mineral magnetic record in peat is unaffected by




post-depositional solution, diagenesis or downwash,  the evidence favours




the view that the magnetic record is sufficiently well preserved to




provide a basis for correlation and relative chronolgy. Its relation to




trace metal deposition suggests it may aid reconstruction of emission




histories, by reflecting variations in magnetic flux density and




mineralogy in response changing technology and energy base. Direct




comparison between records magnetic deposition and vegetation change at




degraded sites may permit evaluation of the causes of such degradation.




                     SECTION THREE




     In lake watersheds where the flux of terrestrially-derived magnetic




minerals is low, atmospheric deposition can affect the magnetic




mineralogy of the recent lake sediments. The most favourable sites are




likely to be those located close to major industrial sources, with




watershed lithologies with low concentrations of ferrimagnetic minerals,




and with low rates of .allochthonous sedimentation. Newton Mere, Cheshire,




England, meets some of these criteria. Newton Mere (Figure 19) is a




closed glacial kettle lake situated between the industrialized zones of




South Lancashire, Deeside and the West Midlands. The recent sediments are




highly organic muds. Figure 19 shows the lake basin and watershed




together with the results of magnetic measurements and heavy metal




analyses for four cores. The curve of frequency-dependent susceptibility




is shown for core J, and lead-210 ages are shown for core G. In all




cores, magnetic mineral concentration increases in the top 18-30 cm,

-------
                                                                           417




coresponding to the last 70 years on the basis of the lead-210




chronology, the timespan over which the main increase in magnetic




material flux to peat surfaces in Northern Europe occurs. The curves for




Cu closely parallel the increase in magnetic mineral concentration,




although this is less clear in the case of Zn, Pb and Ni. Significantly,




the zone of increased magnetic mineral concentration is also




characterised by a reduction in frequency-dependent susceptibility,




consistent with the presence of a relatively coarse-grained




industrially-derived magnetic component.




     Therefore, under favourable circumstances magnetic measurements of




recent lake sediments can provide a record of the history of trace metal




deposition. The advantages of the technique lies in its speed and




non-destructiveness. Also, magnetic measurements may be of indirect value




to lake sediment-based studies of acid rain and trace metal deposition




histories by providing a basis for inter-core correlation and by




identifying shifts in allochthonous particulate input. In addition to




mineral magnetic appliactions, studies of recent paleomagnetic secular




variation in lake sediments can provide rough timescales of sediment




accumulation for the last 100-10,000 years and may be used to extend




timescales based on lead-210.




                SECTION FOUR









     Amongst future research priorities we would consider the following




to be the most important:




1) The exploration of extreme situations in terms of Eh, pH and sulfur




concentrations to test magnetic mineral persistence and the relative




importance of diagenesis.




2) Further characterization of magnetic extracts using optical, XRD, SEM,

-------
                                                                           418




Mossbauer and related techniques.




3) Direct comparisons of the peat and lake sediment records of




atmospheric deposition and ecosystem modification over the last 200-300




years.




4) Use of trees established on ombrotrophic peat and the record in the




peat beneath and beyond them to establish the relative importance of




filtering to all aspects of emission-associated deposition.




5) Further evaluation of mineral magnetic parameters in characterizing




and establishing the source of dusts and aerosols on spatial scales




relevant to acid rain and trace metal deposition studies.




6) Detailed case studies of degraded peat systems linking technological




history to ecological change through the mineral magnetic record of




anthropogenic deposition.

-------
00
c
rt
h4-
8
             Raw
            Coal
Pulverised
  Coal
           H- a
                 FLY  ASH FORMATION
                                   Fly
                                   Ash
                                                                                ro
                                                                                o

-------
                                                                  421
                               FEED COAL
             PYRITE
                I
               as
           Frarnboids
        Combustion Period Short
              and/or
        Combustion Temperatures Low
        Little Dimensional Change

         Little or No Melting
           MAGNETITE
     oxidation

              Haematite
dissolution in an Mg
 rich silicate melt
                                                Ferrous
                    Silicate
                   I
  fusion and ablation
                   V
          Mg RICH MAGNETITE
                     \
                                      Slow Cool
                   Rapid Cool
 few large
 particles
many small
 particles
                                     STOCHIOMETRIC
                                       MAGNETITE
                  EQUIMOLAR
                  MIXTURES
                      of
                  MAGNETITE
                      and
                  MAGHEMITE
                               PULVERISED
                                  FUEL
                                   ASH
Figure 2. Production of  ferrimagnetic material during  fly ash formation.

-------
                                                          422
               TRACE ELEMENT CONTENT
                          OF
                   FERROSPHERES
      Substitution

              Ferrospheres  in the form of an
              Aluminium substituted Ferrite
                        Fe2-3 AI0-7%
              or as an
                   Mg  Rich Magnetite
       accept
        V,Cr.Mn.Co.Ni.Cu.Zn  Transition Metal Ions
       by          fSOMORPHIC SUBSTITUTION

      Volatilisation/Condensation

                 Condensation  of
          Volatilised  Trace Species on Particulate
                    Surfaces
          in  cooler parts  of  the system
Figure 3., Trace element content of ferrospheres.

-------
                                                                                               423
           Sample SIRM against Metal Concentration (nricrograms) for Sunned Stages
           Summed
           Stages
SIRHx
x-fe
SIIVU  SIWV
x'ur  x^Mn
SIWJ^
x-Ni
           1  to 4      0.4050
           1  to 5
       0.8942   1.0940   6.638    46.62   88.33   11.86   218.6
                                            TABLE 17

                                       qUEENSWAY TUNNEL




           Sample SIRM against Metal  Concentration (m-icrograms) for Summed Stages
Summed
Stages
1 to 2
1 to 3
1 to 4
1 to 5
SIRM, SIRM, SIRMx
^xre x^Al x'Pb
0.4441 1.555 3.8832
SIRMx SIRJJ^
^^^7p j^^CU
13.611 51.97
SIRMx- SIRMx Sim^
15^-9
17.97
                                            TABLE 17

                                         KINGSWAY TUNNEL
Table  2. Magnetic:metal ratios  for air  samples  from the Mersey
           tunnels, Liverpool, England.

-------
                                                                                             424
          Sample  SIRM against Metal Concentration (micrograms)
Impactor
Stage
1 1
i 2
J
5

Sample SIRM

Summed
Stages
1 to 4
1 to 5
SIRM,
0.4421
0.4217
0.2746
0.3890


against

SIRJJ,
XTe
0.4050
SIRM,
XAI
0.8289
0.8401
1.1125
1.323


SIRMx
/Pb
2.3451
1.2605
0.3583
0.5824


!xfc
9.021
8.240
4.631
2.950

TABLE 16
SIRM,
/Cu
80.41
38.68
23.37
29.19


Metal Concentration (micrograms) for

SIRMx
/A1
0.8942

SIRM,
XPb
1 .0940

SIRM,
/£n
6.638

SIRM,
XCu
46.62
SIRMx
X^1"
112.99
120.99
40.60
58.24


Summed

SIRMx
XCr
88.33
SIRM,
/*n
10.358
15.122
12.179
14.563


Stages

SIRfJx
x^Mn
11.86
SIRMx
xfo
248.61
302.43
243.78
97.06 !
i


SIWJ, 1
x-Ui j
218.6 j
i
TABLE 17
9UEENSWAY TUNNEL
         Sample SIRM against Metal Concentration (micrograms)
Impactor
Stage
1
2
3
4
5
SIRMx
x'Fe
0.4876
0.4240
0.3437
0.4368

SIRM,
/Al
1 .2744
2.0086
1 .5836
3.599

SIRMx
x""Pb
9.9009
6.4720
14.2566
0.646

SIRMx
/Zn
16.323
14.821
9.536
8.571

SIRM,
x^Cu
85.88
56.03
24.411
26.454

SIW,
x^Cr
183.90
116.51
-
-

SIRK,
X^Mn
16.09
19.41
28.50
-

SIRM,
/Ni
.
_
.
-

                                         TABLE 16
         Sample SIRM against Metal Concentration (micrograms) for Summed Stages
Summed
Stages
1 to 2
\ to 3
1 to 4
1 to 5
SIRMx SIRM, SIRMx
0.4441 1.555 3.8832
SIRM, SIRMx SIRMx SIRMx SIRMx
17-07
13.611 51.97
                                         TABLE 17

                                       KINGSVAY TUNNEL
Table 3.  Particle size variations  for magneticrmetal ratios  for
           air  samples  from the  Mersey tunnels,  Liverpool,  England^

-------
                                                                                                 425
                  Sample SIRM against Metal Concentration fmic'agrams)
Imoactor SIRMx
Stage x^e
2
3
4
0.4217
0.2746
0.2890
SIRMx
0.3401
1.1125
1.222

1
0
0
x^b
.2605
.2583
.5824
/£
8.240
4.631
2.950
SIRMx
x'fu
38.68
23.37
29.19
SIRMx
120
40
58
.99
.60
.24
SIRMx
15.122
12.179
14.563
SIRMx
302
243
97
.43
.78
.06
                                              qUEENSVAY TUNNEL
                 Sample SIRM against Netal Concentration (•icrograms)

Impactor
Stage
2
3
4
SIRMx
x're
0.4240
0.3437
0.4368
SIRM,
2.0086
t .5836
3.599
Sx%
6.4720
14.2566
0.646
SIR*,
x'fn
14.821
9.536
8.571
xfc
56.03
24.411
26.454
SIRM,
XCr
116.51
.

SI*x-
/&n
19.41
28.50

SIM"

_

                                             KINGSVAT TUNNEL
                 Sample SIRM against  MetaJ Concentration  (ppn)
Impactor
 Stage


  2
  3
                           SIRM
                                                                       SI
                                         5230       817
                                         4871       661
                                         3748       470
62O51  14O80   452O
68431  15127   3992
53363  11244   3265
                                                                               SIRM,
19789
2O529
17152
                                    RESCSPENDED WLVERISEO FUEL ASH
                           Irapactor
                           Sta
-------
                                                                         426
        -05-
        -0-6-
         -07-
-200mT
 SIRM
         -0-8-
         -09-
         -1 O-1
                       SIRM

 0-3        0-4        0-5
_J	\	L-
         ^T  Haroa  Hall
         if  Kingaway
         if  Quaanaway

         X  Laaf samplaa
                /()  o«
                •       /
                I      /
                                  1
                                       x\
0-6
 '
                                                              07
                                                                1
      E.C.D.
 O   7-0 pm
 A   3-3 |im
 O   2-0 |im
 0   1-1 n"»
 if Backup filtar
           Figure 4. Plot of -20mT/SIRM versus -200mT/SIRM for leaf  samples
                    and particle sized Hams Hall fly ash and Mersey tunnel
                    dusts.
                    Source: Hunt,  A.,  Jones, J.and Oldfield,  F.
                    The Science of the Total Environment. 33. 129-139. (1984),

-------
         IO
         10  -
       in
         O
         X
         ,o
         10'
           IO1
                                10
                                                Mediterranean  « 0

                                                 North Atlantic    x
                                                          o
                                                         *o    •
                                    AI  ng m3
                      SUSCEPTIBILITY  and ALUMINIUM Concentration
                                                                              427
10
Figure 5. Susceptibility/Al ratios  for soil-sized  particuiates  and
          atmospheric Al loadings.
          Source: Chester,  R.,  Oldfield,  F.,  Sharpies,  J.,  Sanders,G
          and Saydam, A.C.  Water. Air and Soil  Pollution,  in  press.

-------
                                                                  428
        500-


J1
I V)
IJ
1
r
4004>-
II _J
1
II u.



300-



SIRM
ARM


200-


-
100-


•
^.
o A Resuspended and particle sized
<
/

flyash

North sea and North


Atlantic
5 • dusts (SIRM SOxlO'3)

•
^

1

V :
\ •
o
irt
uidjb
w
_>
•§ a
o c
" 0
>>M |
Jo '3 <•>
•o c o
C OlrS
S *
<> ^

>



Q-i 	
0
More secon
: ie. most 'polluted
: OT North Atlantic dusts
2S (SIRM 16-21 xlO"3)
• (V
u 01 North Atlantic dusts
\ ® (SJRM 5-IOxlO'3)
• ie. least 'polluted'
Barbados dust set
A (Red /brown 'Saharan
dusts) (SIRM 4-8x
Barbados dust set










\


^ A (Grey'winter' dusts)
(SIRM 4-8 xlO'3)


c




g
S~^/£>
^k A — — *
90 J ^~~
— I 	 r 	 1 —<— — >
S 10 15 20 25
XqV.
dary soil derived ferrimagnets~0 03»i







summer
HT3)














30
diameter
Figure 6. Plot of frequency-dependent susceptibility versus SIRM/ARM
          ratio for resuspended fly ash and North Atlantic and Barbados
         dusts.

-------
                                                                                                                       429
                                         00:0
                                          no
                                    HEATHWAITE MOSS HI
                                    Pool
                                                                                                          WHITE MOSS     Wl
                                                                                                         BANK END MOSS  81

                                    RUSLANO MOSS   R2
                                    RUSLANO MOSS   RS
                                    OMO pool
             •ialuirt  SIRM
                       Tptat cumulative
 Ftc. J Sacuruion ruMtemul reauneM maimeiizxiiufl i SIR Ml values in recent pent ai Henn«aiic
iruj Rutuml MtMMi. r>ic finiotnm t^ut cnante^ m content ration »nh Occ'i. ifw mini line OKJU the
^umuiaii*e  SIRM at » magnetic motncm >n M.\ m- tn«m me f*c«mnmt u( mi.rci\cd Cuncemraitoni up
ine inr r»rv
                                                                                                                  MOSS   Ml
10 recem cvats at Bana
4» lor f:i^iiv 5.
                                                 i   r    -~ „ _ «- ...
    Flgure  7-                                short
                    Source:  Oldfield,  F.,  Brown,  A.  and  Thompson,  R.
                    Quaternary  Research,   1£,  326-332  (1979).

-------
                                                                       430
MAGNETIC    DEPOSITION   ONTO   OMBROTROPHIC
PEAT—SJRM IIO-WK,INorth East  USA—E. Canada
   Figure 8.  Specific SIRM values of surface samples from ombrotrophic peat sites
            in the northeastern U.S., and eastern Canada.

-------
                                                                      431
   RATIO; MAGNETIC    DEPOSITION   ONTO
   OMBROTROPHIC    PEAT—North East  USA-
   E Canada
Figure 9. SIRM/ARM ratios of surface samples from ombrotrophic peat sites in the
         northeastern U.S. and eastern Canada.

-------
    10
  Of---  	
100
1000
10000
 10
 15
 20
 25
E
o
a
4)

0 0 1
  10




  15
   HEATHWAITE MOSS : HUMMOCK
           HOLLOW
 I'HIUS       Ulmus       Ainu:.


0     20     0  10  0     20     40  0 6
                                                                                 V
                                                                                             % A.P.
                                                                                 r
     Figure 10. SIRM profile and selected pollen  curves  for a core from Heathwaite Moss,  Cumbria,

                England.
                                                                                                                 CO
                                                                                                                 r\>

-------

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2
4



£ 12
o

tfl
20












in
3
C
£
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I
1







0
5
i


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i



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Q
04
2
t

6
-•
10





Spacific SIRM HO-6 Gg''cm3 I
4000 8000 12000 16000
•— 1
| 	 '
I

J Hummock



AXE EDGE HUMMOCK


100  10 0 10  20  0 100 10 20  30 40 0
 Ptrctnloges of Tola) Polltn Counttd
                          I
                                          20
                                                     60
                                                          60
                                  	L
                                                                    Spacific SIRM 110*0 g ' cm' I
                                                                   .0    UX>    800   1200
                                                                  2
                                                                  4
                                                                  6
                                                                 -a
                                                                  10
                                                                  12
Pool
                                                                            AXE  EDGE -POOL
      0501001020050100    20
                                          fin
Figure 11.  SIRM profile and  selected pollen curves for  a core  from Axe  Edge Moor, Derbyshire
             England.
                                                                                                                       CO
                                                                                                                       OO

-------
                           SIRM
                                                  Pinus
                                                                   Ambrosia
   10
 10
 15
 20
100
1000
10000
E
u
  0
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 10
 15
 20
         ELY LAKE BOO : HUMMOCK
                            HOLLOW
0     40    80     0      40
                                                                 % Upland Pollen
     Figure 12.  SIRM profile and selected pollen curves for a core from Ely Lake Bog, Minnesota.
                                                                                                                CO

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                                                                              435
                        ~6
                SIRM  (10~ Am* kg"


              0     2000    WOO
             104
         01
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    ug g~ ary  weignt
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200     3GC ?b
                                                            —  Pb

                                                            —  Cu
                                       20-"
                                            WM 2   Depression
100
200 Zr,
               0     2000
                                             WM 3   Hummock
                  WM 3  Hummcck
Figure  13.  Results of magnetic measurements and heavy metal analyses  of

            cores from Whixall Moss,  Shropshire, England.
            Source: Jones,  J.M. Journal  of Applied Ecology, in press.

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                                                                          436
            SIRM  (10~5 Am2 kg1
                  2000
     a.
     
-------
                                                                   437
  1975-
  1950-
  1925-

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  1900-
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                          Magnetic deposition kg(x10 m y1)
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                     H
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                     Mean values
             KARPANSUO  BOG
        MAGNETIC DEPOSITION  RATES


               1840 -1975 A.D
                                                                     • —I
                                                                      I
  1850-
       Figure 15. Magnetic accumulation rate curves for cores from Karpansuo Bog,
                central Finland.

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       RINGINGLOW    BOG
                                                                   438
          £20-
           Q.
           OJ
           •o
            30-
            40J
                       SIRM  (10~6Am2kg~1)
                      2000    4000
                            6000     8000
                                      RB 1
                                      Pool
  0-6
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0-6
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      IRM
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                                   IRM
                                     -100rrf
                              IRM
      IRM
         300mT
            IRM
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                                   IRM
                                      300mT
                              IRM
                                 300mT
Figure 16.  SIRM and 'S1 value profiles from a core  from Ringinglow Bog,
          Sheffield,  England.

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                             -IRMX/IRM300°
             439
      0.8   0.6    0.4   0.2   0   -0.2  -0.4   -0.6   -0.8  -1.0

    0  '	'	
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 -1000
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                                                       Pool
             -200
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          HEATHWAITE  MOSS - Backfield  ratios
  Figure 17.  'Sf value profiles from cores from Heathwaite Moss, Cumbria,

           England.

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   10
   10
   15
   20
   25
~B
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    5-

   10

   15

   20
100
 i iw ~u uiry 'I
1000           10000
                           -IKM/SIKM
100000   06   0.4   0.2    0  -0.2  -0.4  -0.6   -0.6  -1.0
  _i     i	i	1	1	1	1	•	1	•
ELY LAKt BOG-d)Hummock
 ELY LAKE BOG-(2) Hummock
                                         -200
                            -I     I	L.
                                                                               4	^
                                                                               -1000  -9000
    Figure 18. SIRM and 'S1 value profiles  from a core  from Ely  Lake Bog, Minnesota.
                                                                                                                       O

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                                                                                                           441
          BUL« u*GNE' C MEASUREMENTS             BULK CMCuiC*!. MOSURCMCN1S .mq g
          SIBM "C';«-«-«3 '•>	SlBw/x. '•!«  S M*»ff0t»>    Ptt —•—    Zn —
           X lO"--^:"' — '0-«m                Cu ——    Ni	
         ,0   D6  '    0   '   2  3  -06 -l 0      1035
                                                                              NEWTON  MERE
                                                                       fi'y.  <. Newton Mere. Cheshire. U.K. showing bathymetry.
                                                                       catchment limns and coring locations.
               CORE J
                         NEWTON  MERE
               Magnetic measurements and heavy  metals

Fig. !. Magnetic measurements and heavy metal analyses for Mackereth mimcores from Newton Mere.
             Figure 19.  Magnetic  and heavy  metal profiles  from cores  from Newton Mere,  Cheshire,
                          England.
                          Source: Oldfield, F.,  Barnosky,  C., Leopold,  E.F. and Smith, J.P.
                          Hydrobioloeia. 103. 37-44  (1983).

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                                                                          442
               VARIABILITY AND ERRORS  IN PALEOLIMNOLOGY
                        David  Parkhurst -  Ind.  Univ.
     In paleolimnology, as in all science,  we would like to be
correct.  Failing that, we would like to have some idea how far from
correct we are.  In general,  we are interested both in our degree of
accuracy and in our degree of precision.
     These ideas  can be put together by reference to Figure 1, which
uses the example  of dates corresponding to various depths in a core, as
                   210
reconstructed from    Pb dating.  In that figure, the solid line
represents the true, but unknown, relationship of date to depth; the
bold aashed line  represents our best estimate of that relationship; and
the light dashed  lines represent an estimate of the imprecision of our
estimate (for example, 95% confidence limits).  At any given depth the
closeness of the  bold dashed  line to the solid line represents our
accuracy, or oeing right on average, or a lack of bias.  The width of
the lignter dashed lines represents the variability of our estimate, or
the uegree of imprecision in  that estimate.

                               Accuracy
     I would like to emphasize that I believe our most important job as
paleolimnologists is to try to be accurate.  That is, we need to get
our science right, so that our best estimates are correct on average
for whatever it is we are trying to estimate.  At the same time, we
can't  ignore the fact that even  if we are correct on average, there
will still be statistical variation around our averages.  So, we ought

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                                                                          443
to attempt to put some sort of error bars on every estimate we make.
In what follows, I would like first to give some examples of how good
science can lead to better accuracy, and then to discuss the question
of variability estimates.  The examples are:
1.  Steve Norton has suggested that we should work with absolute
concentrations of chemicals rather than with the relative proportions
of each.  If we fail to do this, and one component of the mixture
changes, we may conclude that all the other components have changed as
well because their proportions will change.  This is clearly an
inaccurate conclusion that can be avoided by clear thinking and good
science.
2.  Peter Campbell tells us that for certain measurements we need to
freeze our samples and to keep oxygen away from them, in order to
measure what was really there in the original sediments.  If we fail to
do these things, the composition of the sediment will change before we
measure it -- tnen we can never get an accurate measurement of what had
oeen there.  In such a case, knowing the precision or even the accuracy
with wnicti we have measured the changed composition  is not of very much
interest, particularly if that imprecision is small  relative to the
size of tne cnange that has occurred.
                                              210
j.  Mike Binford and others have talked about    Pb  dating.  There it
is clear that we must use a correct model.   If we assume a constant
                         210
initial concentration of    Pb when that assumption  is untrue, then
our dates assigned to various depths in the core cannot be accurate,
particularly in the deeper sediments.  Also, we may  need to correct for
biological mixing; if we do not, our dates may again be wrong on

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                                                                          444
average.  If they are very wrong, the precision of the CIC estimate is
hardly of any interest.
4.  Ron Davis spoke about pH reconstruction.  To paraphrase him in
mathematical terms, we might use a model which stated:
            log a =  a*pH  +  b*alkalinity  +  c*S04 +  d*f(fish).
Here we often regress log a on present day pH; then we turn the
relationship around at various depths in the core to estimate pH from
log ex.  As Davis pointed out, all the variables on the right hand side
of tnis equation tend to co-vary.  That is, they are not independent.
Given that, it is okay to back-calculate pH from a if all the covarying
relationsnips between the variables remain the same.  If the
relationships among them change, however, it may be quite incorrect to
do this type of back calculation.  (For further comments about this
problem see an informative paper called "Use and abuse of regression"
by Box, 1966.)
     If the covariance structure of the "independent" variables changes
with depth in the core,  then we introduce a potential inaccuracy in our
dates but have no way to estimate that  inaccuracy.  If this actually
happens, then the precision estimates which are readily available from
regression analysis may  be misleading.
5.  As a final simple example, Rick Battarbee pointed out the
importance of identifying each diatom taxon correctly when we use
diatoms to reconstruct pH.

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                                                                          445
     To summarize so far, let me reemphasize the importance of being
accurate.  To be accurate we have to get the basic science right.
Generally, and this is a real problem, we can't know how accurate we
are on average.  The best we can do is try to get many independent
lines of evidence for any given phenomenon, or try to measure each
variaole in several different ways and then look for agreement.

                               Precision
     As stated above, we often will not know how accurate our estimates
of a given quantity are.  Even so, for almost any quantity we measure
or derive, statistical techniques are available to estimate the lack of
precision in that quantity.  We should be using these more often than
we do in paleolimnology, I believe.  Let me give two examples:
1.  The Electric Power Research Institute is currently sponsoring a
large project, Paleolimnological Investigations of Recent Lake
Acidification  (PIRLA).  As part of that work, Russell Kreis is
coordinating a variability study to help estimate precision.
     In this, a few of the many lakes in the overall project have been
selected for special attention.  Each of these lakes will be cored
three times.   (Most of the lakes will be cored just once.)  Then each
core will be suosampled in numerous ways.  As an illustrative example,
consider estimating pH values using the regression method of Charles
(1985).  A variability study for this reconstructed pH from a given
time interval  in a given lake might take the form shown in Fig. 2.

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                                                                          446
     In this example, three cores are taken from the lake.  Each
sediment interval is cut into two halves; those are weighed and
digested, and a microscope slide is made from each.  The diatoms are
identified and counted by five different diatomists, each making
duplicate counts of each slide.  The data from these 60 counts could
then be plugged into the pH reconstruction equation to yield 60
estimates of pH (for a given time interval).  These estimates can then
be analyzed by nested analysis of variance (Sokal and Rohlf, 1981,
Chapter 10).
     This information can be used in two ways.  First, it will identify
which step in the pH-reconstruction process introduces the greatest
variability.  One can relate the variability in each step with the
human effort involved in that step to make future studies more
efficient.  Second, variances derived in this way can be used as
variance estimates for all lakes in the PIRLA study.  These can be
combined with other variance estimates (such as those related to using
a regression equation to derive pH values from diatom counts) to put
error bars on pH estimates.  Similar procedures could be used, of
course, for aluminum concentrations, pollen counts, or any other
variable.
     The example given would be tremendously time-consuming to carry
out, and indeed the PIRLA variability study will not follow that exact
procedure.  It is infeasible to replicate every measurement to such a
degree.  Nevertheless the variance estimates obtained will be
exceedingly valuable, and similar procedures are to be recommended for
at least a subset of any large study.

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                                                                          447
2.  One crucial component of paleolimnological reconstruction is the
date estimates assigned to various depths in the core.  The most
generally applicable methods for dating sediments appear to be those
              210
making use of    Pb.  However, to date we know of no published
methods for putting confidence limits (or other forms of error bars) on
derived dates.  J. Robbins (pers. comm. 1984) has developed an error
                                                          210
propagation method which makes use of estimated errors in    Pb and
?i n
  uPo counts, in the mass of the    Po spike used in the    Pb
count, and in other variables (e.g., estimated sedimentation rate) to
put error bars on dates.  Battarbee, Digerfeldt, Appleby, and Oldfield
(1980) indicated error bars for estimated dates, but did not describe
the methods used to obtain them.  Mike Binford has begun to estimate
uncertainties in dates from the CRC model using Monte Carlo
simulation.  In my opinion, the Monte Carlo method has greatest promise
for estimating 95% confidence limits on dates, because it is very
general ana flexible.
      In any case, developing methods to estimate uncertainties in
estimated dates should have high priority, because of the central
importance of the dates to any  interpretation of a core.  There remains
                                                  210
the problem of uncertainty in the accuracy of the    Pb dates,
resulting from the difficulty of choosing a correct model for any given
core.  For some cores  (and particularly for older sediments), this
uncertainty may exceed that associated with the fit of the data to the
chosen model.  Even so, we should estimate the latter uncertainty if
only  because it provides a minimum estimate of the total uncertainty.

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                                                                          448
                              Conclusion
     In any field of science, including our own, both accuracy and
precision are important.  Generally speaking, statistical methods are
available to estimate the uncertainty associated with lack of precision
in our measurements or in quantities derived from them.  Just as
generally, inaccuracy usually arises from unknown sources of bias;
because they are unknown, these uncertainties are difficult or
impossible to estimate.
     For these reasons, we should as far as feasible do three things.
First, we should use replicates and statistical methods to estimate
imprecision uncertainty -- this at least produces a lower bound on our
total uncertainty.  Second, we can try to measure each important
quantity by several independent methods, hoping that these methods do
not share the same biases.  If they all tell us the same story, we
certainly have greater faith in our accuracy.  Finally, we must
continue to develop and refine the basic scientific understanding of
the phenomena we are studying;  this is the most direct and fundamental
way to reduce inaccuracies.

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                                                                          449
                            ACKNOWLEDGMENT
     I  thank Donald Charles for comments on the manuscript.
                              REFERENCES

Battarbee, R.W., Digerfeldt, G., Appleby, P.G., and Oldfield, F.
     1980.  Paleoecological studies of the recent development of Lake
     Vaxjosjon, III.  Reassessment of recent chronology on the basis of
     modified 210Pb dates.  Arch. Hydrolbiol.  89:440-446.
Box, G.E.P.  1966.  Use and abuse of regression.  Technometrics
     8:625-629.
Charles, D.F.  1985.  Relationship between surface sediment diatom
     assemblages and lake water characteristics in Adirondack lakes.
     Ecology 66, in press.
Sokal, R.R. and F.J. Rohlf.  1981.  Biometry (2nd edn.) W. H.
     Freeman, San Francisco.
David F. Parkhurst
School of Public and Environmental Affairs
Indiana University
dloomington, Indiana 47405
July 1984

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                                                                         450
Figure 1.  A hypothetical  data-depth curve derived from
measurements at one-centimeter intervals in a core.  The true
relationship, an estimate  of that relationship,  and 95% confidence
limits for the estimate are diagrammed.

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                                                            451
                                  DATE
                     o
                     o
                     00
o
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00
o
o
CD
o
in
o
O
O
CO
        0
                         Tfi
                J  True date

                I   Estimated date for  I-cm  interval

                I I  95%  Confidence limits of estimate
        10.—
        20 —
DEPTH
 (CM)
        30-
        40"

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                                                                                            — CORES
                                                                                            __SUBSAMPLES
                                                                                            _ DIATOHISTS
                                                                                            _ COUNTS
                                           PH2141

Figure 2.   Example of a nested experimental  design,  generally  similar to those in the PIRLA variability
study.  The diagram represents data  for a  single time  interval  from one lake.   The pH value shown is
that estimated from diatom data,  obtained  in the first count by the fourth  diatomist, of the slide
prepared from the first subsample (of the  time  interval  under  analysis) from the second core.   The
scheme shown would yield 3-2-5-2=60  such pH  estimates, which would  then be  available for analysis of
variance.
                                                                                                                 en
                                                                                                                 (V)

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