EPA-660/3-75-006
FEBRUARY 1975
                                    Ecological  Research Series
Phosphorus Uptake  and  Release
by  Lake Ontario Sediments

                                    National Environmental Research Center
                                      Office of Research and Development
                                      U.S. Environmental Protection Agency
                                             Corvallis, Oregon 97330

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                               EPA-660/3-75-006
                               FEBRUARY  1975
     PHOSPHORUS  UPTAKE AND RELEASE BY

          LAKE ONTARIO SEDIMENTS
                   By

             R.T.  Bannerman
             D.E.  Armstrong
             R.F.  Harris
             6.C.  Holdren
        University of  Wisconsin
       Madison,  Wisconsin    53706
            Grant  #800609

        Program Element 1BA026
       ROAP/Task No.  21 AKP/008
           Project Officer

           Tudor T.  Davies
        Grosse lie Laboratory
National Environmental  Research Center
     Grosse lie, Michigan   48138
NATIONAL ENVIRONMENTAL RESEARCH CENTER
  OFFICE OF RESEARCH AND DEVELOPMENT
 U.S.  ENVIRONMENTAL PROTECTION AGENCY
        CORVALLIS,  OREGON   97330

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                               ABSTRACT

     Sediment cores were obtained from 15 lake stations  representing
the three major basins and the Inshore Zone of Lake Ontario.   Cores
were sectioned for characterization of the surface sediments  according
to inorganic P chemical mobility.  Physical mobility was characterized
by measurement of P release from intact cores incubated under controlled
laboratory conditions.  The proportions of potentially chemically mobile
inorganic P were usually high (30 to 60%) in the central basin sediments
and low (2 to 8%} for the inshore zone sediments.  Although the amounts
of inorganic P desorbed after three successive equilibrations (in .1M
NaCl) of Lake Ontario sediments represented only 3 to 17% of  the potentially
mobile inorganic P, sufficient inorganic P was desorbed to restore a
large part of the original interstitial inorganic P concentrations.
Interstitial inorganic P (mobile P) concentrations ranged from 14 to
1280 jug/1 and were higher than dissolved inorganic P concentrations in
the overlying water.  Diffusion rates estimated from the range of observed
                                                                  -2    -1
interstitial inorganic P values ranged from about 0.05 to 0.6 mg m   day
                                                        -2    -1
and were in agreement with the range of 0.03 to 0.8 mg m   day   estimated
from P release from intact cores incubated under controlled laboratory
                                                      -2    ~1
conditions.  Based on  an inorganic P flux of 0.2 mg m   day   , the
estimated annual contribution of inorganic P to Lake Ontario  water is
equal to about 10% of the external P loading.
     This report was submitted in fulfillment of Project Number
R-800609, by the University of Wisconsin, under the sponsorship
of the Environmental Protection Agency.  Work was completed as of
May, 1974.

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                               CONTENTS
                                                                  Page
Abstract                                                            ii
List of Figures                                                     1v
List of Tables                                                      v
Acknowledgements                                                    vi
Sections
I      Conclusions                                                   1
II     Recommendations                                               3
III    Introduction                                                  4
IV     Methods and Materials                                         7
V      Results and Discussion                                       13
VI     References                                                   48
                                  m

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                               FIGURES
No.
1           Sampling Sites  (IFYGL  Station
            Identifiers) for Lake  Ontario  Sediments                    8

2           Inorganic P Sorption Curves for Lake Ontario
            Inshore and Basin Sediments                              41

3           Levels of Dissolved Inorganic  P Released from
            Intact Sediment Cores  Obtained  November 6, 1972          44

4           Levels of Dissolved Inorganic  P Released from
            Intact Cores Obtained  October  9,  1973; for Cores
            Designated Air; N9, the N9  was Introduced after
            35 days.         ^       ^                                45
                                  IV

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                               TABLES

 No.                                                              Page


 1          Total  P,  Total  Inorganic  P,  and Total Organic P
           at Various  Sediment  Depths in  Lake Ontario Cores.       14

 2         Forms  of  Inorganic P in Lake Ontario Sediments.         16

 3         Sediment  Water  Content of Lake Ontario  Cores.           19

 4         Sediment  Exchangeable Inorganic P in the  0 to
           5 cm Sediment Layer  of Lake  Ontario Cores
           Obtained  November 6, 1972.                              21

 5         Interstitial  Inorganic P  in  Lake Ontario
           Sediments.                                              23

 6         Effect of Sediment Storage on  Interstitial
           Inorganic P Values.                                     25

 7         Interstitial  Inorganic P  in  Successive  Aliquots
           Squeezed  From Lake Ontario Sediments.                   27

 8         Total  Filterable Fe  in the Interstitial Water
           of Sediments from Lake Ontario.
                                                                  28

 9         Desorption of Inorganic P from Lake Ontario
           Sediment  after  Successive Equilibrations  in
           Distilled Water.                                        30

10         Desorption of Inorganic P from the 0 to 5 cm
           Sediment  Section of  Lake  Ontario Cores  after
           Successive Equilibrations in Distilled  Water.           31

11          Determination of the Effect  of 0.1M NaCl
           Solution  on Desorption of Inorganic P  in
           Sediment  Suspension  of Sediment from the
           5 to 10 cm Core Section of Station 75.                  32

12         Effect of Filter Pore Size on  Inorganic P
           Desorption Values for Sediment from the
           0 to 5 cm Section of Lake Ontario Cores
           Suspended in Distilled Water.                           34

13         Desorption of Inorganic P from Lake Ontario
           Sediment  after  Successive Equlibrations in a
           0.1M NaCl Solution.                                     35

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                                TABLES
 No.                                                               Page

14          Desorption of Inorganic  P from Sediment
            in the First 5 cm  Section of Lake Ontario
            Cores after Successive Equilibration in a
            .1M NaCl  Solution  under  Oxic or Anoxic
            Conditions.                                             37

15          Sorption  of Added  Inorganic P by Lake
            Ontario Sediments  Obtained June 21, 1972.               39

16          Sorption  of Added  Inorganic P by Lake
            Ontario Sediments  From the 0 to 5 cm Core
            Sections  Obtained  November 6, 1972.                     40

17          Desorption of Added  Inorganic P by Sediments
            in the 0  to 5 cm Section of Lake Ontario
            Cores Obtained November  6, 1972.                        42
                                  VI

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                          ACKNOWLEDGMENTS

     The authors wish to express their thanks to Donald H.  Mezei,
Susan Adams, Sameer Halaka for technical  support, the officers and
crew of the Advanced II, Researcher and Porte Dauphine, and H. B.
MacDonald, the head of technical operations, Canada Centre for Inland
Waters, for cooperation with planning and supplying equipment for  the
1973 Porte Dauphine cruise.

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                             SECTION I

                            CONCLUSIONS
The proportion of potentially chemically mobile inorganic P (NaOH-P)
was high (30 to 60%) in the basin postglacial  muds and in some regions
of the southern Inshore Zone of Lake Ontario,  and was low (2 to 8%)
for the glaciolacustrine clay and most of the  Southern Inshore Zone.
While similar results were observed for NaOH-P and exchangeable
inorganic P, the proportion of exchangeable P  was lower (13 to 18%)
for basin sediments.
Amounts of inorganic P desorbed after three successive equilibrations
of Lake Ontario sediments represented only 3 to 17% of the potentially
chemically mobile inorganic P (NaOH-P).  However, the appreciable
amounts of inorganic P in solution after each  equilibration indicated
that the potentially mobile sediment inorganic P could largely restore
in situ interstitial inorganic P concentrations.
Levels of interstitial inorganic P (mobile P)  ranged from 14 to 1280
jjg/1.  Concentrations were usually higher in the basin than in the
inshore sediments.  This trend was in agreement with the high proportion
of potentially mobile inorganic P in the basin sediments.
The IIP values were always higher than the DIP levels in the overlying
lake water.  This suggests a potential exists, due to the concentration
gradient, for release of mobile P to the overlying water.
The physical mobility of sediment inorganic P  was sufficient to
release DIP to the overlying lake water from intact cores under
controlled laboratory conditions.  The highest levels of P obtained
in the overlying lake water for individual cores ranged from 5 to 250
jjg/1.  The levels of P released reached 10 jug/1 or higher between 12
and 25 days of incubation for most cores and surpassed the mean
concentration of about 11 ug/1 for "soluble phosphate" in Lake Ontario
bottom waters.  For deep lakes like Lake Ontario, the physical mobility
of sediment P is likely controlled rrainly by diffusion cf IIP from the
sediments to overlying water.  Diffusion rates estimated from the
range of observed IIP values (ICO to 1000,ug/l) ranged from about

                                  1

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                -2    -1
0.05 to 0.6 mg m   day   and were in agreement with the  range  of  0.03
            ?    -1
to 0.8 mg m~c day   estimated from the cores  incubated in  the
laboratory.  Based on the inorganic P flux of 0.2 mg m~^ day"   (mean
for incubated cores), the estimated annual contribution  of inorganic P
to the lake water from the sediments is 1.4 x 10^ kg of  P  per  year.
The estimated sediment contribution is about  10% of the  external  P
loading (1.3 x 107 kg/yr).

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                            SECTION II
                         RECOMMENDATIONS
Results of this investigation indicated that the  sediment contributes
about 10% of the external  P loading for Lake Ontario.   The significance
of the sediments as a source of P would increase, however, if  other
external sources of P were reduced.  It is  recommended, therefore,
the mechanism and magnitude of P release from the sediment be  further
investigated.
Since interstitial inorganic P is the most  mobile fraction of  the
sediment P, more complete investigation of  IIP concentrations  should
be pursued with emphasis on seasonal variations and the technique of
interstitial water separation.
Although diffusion is probably a principle  means  of P  transport,
evaluation of other transport mechanisms, such as turbulent mixing
could further clarify the physical mobility of sediment P.  The
accuracy of the determination of the amounts of inorganic P released
from the sediment by diffusion would be increased by an experimentally
determined diffusion coefficients for Lake  Ontario sediments.
The extent to which inorganic P released from the sediments is
transported to the photic zone should be evaluated.

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                            SECTION III
                           INTRODUCTION
The degree to which sediments are able to replenish dissolved inorganic
phosphorus (DIP) in the overlying lake water is of major concern in
relation to attempts to retard or reverse lake eutrophication.   In
terms of total P, the sediments probably serve as a "sink" for P as
a result of sorption and sedimentation processes.  However, release of
inorganic P from sediments may play a role in controlling the levels
of DIP in the overlying water.
Release of inorganic P from sediments is expected to be controlled
by both the chemical and the physical mobility of sediment inorganic P
(Syers et aj_. 1973).  Chemical mobility refers to the rate and extent
of  sediment inorganic P interaction with the surrounding (interstitial)
water and is controlled by the forms of inorganic P contained in the
sediment.  According to this concept, inorganic P in solution or
interstitial water inorganic P (IIP) is completely mobile, while sediment
inorganic P in equilibrium with the IIP is potentially mobile,  and
inorganic P which does not interact with the interstitial water is
immobile.  Available evidence indicates that the important sediment
inorganic P compounds are P sorbed on hydrous Fe and Al oxides
(nonoccluded P), P sorbed on CaC03, and apatite (Williams and Mayer
1972; Syers et^ al_. 1973).  Occluded P or P contained within Fe oxides
may also be present in some sediments.  Except for apatite and possibly
vivianite, discrete P compounds have not been identified in sediments.
Nonoccluded P is in equilibrium with IIP and is potentially mobile,
while occluded P and apatite are immobile.
The chemical mobility of sediment P can be determined by measurements
of IIP and by using extraction procedures (Chang and Jackson 1957;
Williams t a\_,  1967) developed for sediments (Williams t aj_.  1971  a;
1971 b) which allow measurement of nonoccluded and apatite P by
sequential extraction with NaOH, citrate-dithionite-bicarbonate
(CDS), and HC1 reagents, respectively.  Furthermore chemical  mobility
of sediment P has been related to the availability of sediment  P to
algae.  Recent evidence (Sagher 1974) has shown that algae in close

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contact with sediments are able to utilize the dissolved inorganic P
and the potentially mobile sediment inorganic P fraction (NaOH-P).
Physical mobility of phosphorus refers to the transport of P within
sediments and across the sediment-water interface.   In shallow waters,
transport may involve resuspension of bottom sediments by wave action.
However, in deeper waters, transport likely involves the chemically
mobile sediment P and the processes of diffusion or partial  mixing of
surface sediments (Lee 1970; Williams and Mayer 1972; Syers  et al.
1973).
In many lakes, sediment IIP levels exceed dissolved inorganic P
concentrations in the overlying water (Stumm and Leckie 1971;
Bannerman 1973) and a tendency exists for dissolved inorganic P to
move from the sediments to the lake water.  Furthermore, the amounts
of potentially mobile P in equilibrium with IIP are frequently high.
The relationships between phosphorus chemical and physical mobility
are not understood sufficiently to allow precise predictions of inorganic
P release rates from sediments.  However, measurements of chemical
mobility will facilitate evaluation of the potential for inorganic P
release.
While considerable information is available on the sediments of
Lake Ontario and the other Great Lakes (Kemp and Lewis 1968; Kemp 1971;
Thomas e_t jil_. 1972), the nature and mobility of sediment P in the
Great Lakes has received limited attention.
Important information on the phosphorus characteristics of deep
sediment cores from Lake Ontario was provided by Kemp e_t a_K (1972)
and Williams and Mayer  (1972).  The interstitial water composition
(not  including phosphorus) was determined for Lake Ontario by Weiler
(1973) and for Lake Michigan by Callender (1969).  Electrodialysis
was investigated as a technique for extracting mobile P from Lake
Ontario sediments (Kemp and Murdrochova 1971).
The purpose of this investigation was to evaluate the chemical and
physical mobility of inorganic P in Lake Ontario sediments to

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facilitate evaluation of the impact of the bottom sediments on the P
status of the lake water.

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                            SECTION IV
                      METHODS AND MATERIALS
SAMPLING PROCEDURES
Cores of Lake Ontario sediment were obtained with a Benthos  Gravity
corer.  Cores were divided into 3 or 5 cm sediment sections  to a
depth of 15 or 25 cm below the sediment surface.   Sediment sections
were extruded into small plastic bags for transport to the laboratory
or in situ manipulation of the sediment.  Intact  cores were  also
transported to the laboratory for measurement of  P release under
controlled conditions.  All sediment samples were stored cold (ice
chest or 4C).  The samples were collected from 10 or more sampling
sites during three sampling trips on Lake Ontario.
For the initial sampling trip (June 21, 1972), ten sampling  stations
were selected to allow comparison of the three major lake basins  and
the postglacial mud and glaciolacustrine clays (Figure 1).  Four  cores
were taken at each station to allow comparison of station and
interstation variability.  Based on the general sediment classification
of Thomas et a].. (1972), IFYGL station identifiers 83, 75, 92, 45, 32
and 10 were postglacial muds, stations 34 and 52  were glaciolacustrine
clays, and station 62 was near a between basin sill of glaciolacustrine
clay (Figure 1).  The Kingston Basin was also sampled at station  96.
All cores were divided into 5 cm sediment sections and transferred to
plastic bags in the field.  Samples were transferred to glass jars
purged with N2 upon return to the laboratory.  The P measurements
included total P, total inorganic P, total organic P, forms  of inorganic
P, and sorption characteristics.
For the second sampling trip  (November 6, 1972),  IFYGL station identifier
30 (located in the inshore silts according to the classification  of
Thomas et _al_.  1972) and 60 of the inshore zone were selected in addition
to those sampled in June 1972, except that stations 96 and 32 were not
sampled (Figure 1).  Cores were obtained at stations 10, 34, 45 and
75 to provide  intact cores for transport to the laboratory.   Additional
cores at some  stations were obtained for comparison of station or

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                                                                          Kingston
                                                                       96   Basin
                                                                       Duck-Gdlo Sill
Rochester
                            -'   Mississauga .45 .;
                                       Basin
                                     Whitby-Olcott
                       Niagara R.        Sill         Genesee R.
                                                                Scotch Bonnet Sill
Figure 1.  Sampling Sites  (IFYGL Station Identifiers)  for  Lake  Ontario Sediments.

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interstate'on variability.  Measurements made on the 5 cm sediment
sections obtained included total  P, total  organic and inorganic P,
forms of inroganic P, sediment exchangeable P and sorption and
desorption characteristics.
The third sampling trip (October 9, 1973)  included IFYGL station
identifiers 14 and 41, located in the inshore silts according to
Thomas t a]_.  (1972), and the mouth of the Genesse River (GR) in
addition to those sites sampled in June, 1972, except that stations
83, 52 and 32 were not sampled.  The first 15 cm of one core at each
station was divided into 3 cm sediment sections and immediately
squeezed in a pressure membrane device (Reeburgh 1969) to obtain
the interstitial water.  The interstitial  water in the 6 to 9 ml
aliquot was retained for analysis.  The first 6 ml of interstitial
water squeezed was disregarded because of observations of lower
inorganic P values present in the initial  aliquots squeezed from a
membrane squeezer, also reported by others (Bray ejt aj_. 1973; Weiler
1973).  An effort was made to maintain the original sediment
temperature and oxidation status during the squeezing process.  Effects
of oxidation were minimized by rapid transfer of the sediment sample
from the core barrel to the squeezer, purging the squeezer with N2
before closing, and storage of unsqueezed samples in a N2 atmosphere.
Temperature was controlled by squeezing and storing sediment inside
a refrigerator.  The interstitial water was subsequently analyzed for
DIP and total Fe.  A lake water sample from directly above the
sediment-water interface was filtered immediately (0.45 Aim filter),
and the DIP levels were determined upon return to the laboratory.
The 5 cm core sections obtained for analyses other than IIP were
immediately transferred from the small plastic bags to glass jars
purged with N.  The sediment P analyses included measurement of
total P total inorganic P, total organic P, forms of inorganic P
and desorption characteristics.  Intact cores from stations 1C, 30
and 60 were transported to the laboratory for measurement of P
release under controlled conditions.

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ANALYTICAL METHODS
Subsamples were used in the wet state for all experiments.   Moisture
contents of the bulk samples were determined by drying a subsample
at 110C overnight.  Total organic P was determined by sequential
acid and alkali extractions of the sediment and analysis of inorganic P
and total P in the pooled extracts (Mehta t al_. 1954; Sommers elt al_.
1972).  Total inorganic P was taken as the inorganic P in the combined
extracts prior to digestion.  Total P was obtained from perchloric
acid digestion of the combined extracts.  Perchloric acid digestion
was found to yield total P values slightly higher or equal  to the
values from persulfate digestion (Amer. Public Health Assoc. 1971).
Sediment exchangeable inorganic P was determined by the procedure
described by Li et al_. (1973), except that the 32P was added before
the sediment suspension was equilibrated.
The forms of inorganic P  (NaOH-P, CDB-P and HC1-P) in the sediments
were determined by inorganic P fractionation based on the procedures
described by Williams et aj_. (1971 a).  The reagent sequence was Q.1N
NaOH.W NaCl, 17 hours (NaOH-P), citrate-dithionate-bicarbonate,
85C 15 min  (CDB-P), and IN. HC1 for 4 hours  (HC1-P).  The NaOH
extraction was conducted on duplicate samples receiving 0 or 300 ug/g
of inorganic P added with the NaOH reagent.  Recovery of added P in
the NaOH extract was usually greater than 90% except for station 34
which gave recoveries of 0 to 8% for the different sediment layers.
The NaOH-P values for this sediment were corrected by dividing the
amount of P extracted in the unamended sediment by the fraction of
added P recovered in the amended sediment (Williams jrt aj_.  1971 b).
The added P not recovered in the NaOH extract was recovered in the
subsequent CDB extract.  Consequently, the CDB-P values for station
34 were decreased by the amount that NaOH-P was increased by the
correction procedure.  Inorganic P was measured in neutralized NaOH
and HC1 extracts by the method of Murphy and Riley (1962) and in
CDB extracts by the method of Watanabe and 01 sen (1962).
                                10

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Total Fe was measured on interstitial  water samples by atomic
absorption using the Murphy and Riley  P analysis sample due to  the
limited volume of interstitial water available.
EQUILIBRATION PROCEDURES
Sediments used for determination of desorption,  sorption and
exchangeable inorganic P characteristics were equilibrated as a 4%
suspension containing 1.6 g sediment (dry weight basis) in 40 ml  of
distilled water (sorption, exchange and desorption) or O.W NaCl
(desorption).  The sediment suspensions were equilibrated for 40 hours
in polycarbonate centrifuge tubes (50 ml; screw cap) on a wrist action
shaker at 25C.  The equilibrated samples were centrifuged at 10,000 rpm
(12,062 relative centrifugal force) on a Sorvall refrigerated centrifuge
for 15 minutes, decanted into clean centrifuge tubes, and centrifuge
again, except for the desorption equilibrations  performed in a  0.1M.
NaCl which were filtered (0.45 jum) after the initial centrifugation
step.  A N2-filled plastic glove bag was used during manipulations
of the samples to limit contact with oxygen.  For example, the  steps
involving decanting, filtration, addition of inorganic P, addition
of 32P, addition of the distilled water, and addition of 0.1M NaCl
solution were all conducted in the glove bag.  The distilled water
and O.W NaCl solutions used for sediment equilibration were stripped
with N for about 2 hours prior to mixing with the sediment. For
successive equilibrations, the tubes were  re-weighed  and the sediment
resuspended in the appropriate amount of distilled water or 0.1M_ NaCl
solution for a final volume of 40 ml.   The tubes were placed in glass
jars purged with N2 during equilibration on the wrist action shaker.
The effects of filter size  (0.45, 0.22 and 0.10 urn Millipore filters),
and O.lj^ NaCl and distilled water on equilibration P values were
evaluated by using the above equilibration procedure.  Measurement
of inorganic P desorption under oxic and anoxic conditions involved
handling in air and equilibration in air-containing solutions  (oxic)
or equilibration at room temperature for 11 days under 0
conditions  (anoxic).

                                 11

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The release of inorganic P from intact sediment cores  was  evaluated
using the sampling core barrel  as the incubation column by placing
the cores in a refrigerator at  the in situ sediment temperature,  and
incubating the cores under quiescent conditions after  placing  2  liters
of filtered Lake Ontario water  in the column above the core.   A  glass
liner (5.8 cm i.d.) was placed  inside the plastic core barrel  holding
the sediment and water to prevent sorption of inorganic P  by the
plastic liner.  The glass liner was pre-soaked in phosphate solution
(2 mg/1) to prevent sorption of DIP released from sediments.
A short piece of plastic core barrel capped by a cork  was  placed
over the column.  Holes drilled in the plastic and/or  cork provided
ports for sample withdrawal and introduction of air or N2  while
helping to maintain the desired atmosphere in the water above  the
core by limiting exchange with  the atmosphere.  For some columns, air
or N was introduced beneath the surface of the overlying  water  column
through 6 mm pyrex tubing.  The N was prepurified and was passed
through pyrogallol 15% (w/w) in KOH (20% w/w) prior to passage into
the water column to remove traces of C^.  Both the Ng  and  air  were
also passed through distilled water to maintain saturation and reduce
evaporation in the core.  Other cores were incubated with  the  overlying
column exposed to the atmosphere without introduction  of air or  N
The concentration of DIP in the overlying lake water was measured
over a period of 60 to 70  days.  The three intact cores obtained
at station 10 on the November 6, 1972 sampling trip received
intermittent Ng treatment, air, and no treatment, respectively.   Cores
from stations 34, 45 and 75 of  the same sampling trip  were not treated
with air or Ng.  Cores from stations 10, 30 and 60 of  the  October 9,
1973 sampling trip were treated initially with air, and after  35  days,
one of the two cores for each station was treated with N2  for  the
remainder of the incubation.
                                  12

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                            SECTION V
                       RESULTS AND DISCUSSION
FORMS AND AMOUNTS OF SEDIMENT P
Total P and total inorganic P concentrations in the upper 20 cm of
Lake Ontario sediments ranged from 500 to 1500 and 500 to 1230 jug/g,
respectively, and were usually closely related (Table 1).  Amounts of
total P were similar to those reported by Kemp et_ al_. (1972) and
somewhat lower than found by Williams and Mayer (1972).   Values for
cores taken at different times from the same station agreed closely,
indicating that sediment sampling and station locating techniques were
adequate.  In most cases, levels were higher in the deep basin sediments
than in sediments from the Inshore Zone.  An increase in total P content
with increasing depth of the water column is a common observation in
small lakes (Rohlich 1963; Delfino et al_. 1969; Williams et al_. 1970)
and apparently reflects transport and deposition of fine-textured
materials in deep water areas.  Total inorganic P tended to decrease
with depth over the upper 20 cm for station 30 (inshore silts), station
34 (glaciolacustrine clays), station 10 (postglacial muds), and
station 60 (Inshore Zone).  This trend was previously observed for
a longer sediment core (1.5 m) from the Mississauga Basin (Williams
and Mayer 1972).
Amounts of organic P were usually low (0 to 290 jug/g) and were lower
in the glaciolacustrine clays than in the postglacial muds (Table 1).
Concentrations tended to be lower over the 5 to 15 cm interval than
at the 0 to 5 and 15 to 20 cm depths.  Amounts of organic P in cores
from the Mississauga Basin were comparable to the levels reported by
Williams and Mayer (1972).
Differences among stations were more apparent in the forms of
inorganic P present than in the total P or total inorganic or organic P
contents of the sediment.  For the upper 5 cm layer, the Inshore Zone
sediments tended to contain small amounts of NaOH-P and CDB-P and a
high proportion of HC1-P (Table 2).  In contrast, basin sediments
contained comparable proportions of NaOH-P and HC1-P and smaller
amounts of CDB-P.  Similar trends were found for basin sediment samples
                                13

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Table 1.   TOTAL P,  TOTAL INORGANIC P,  AND TOTAL  ORGANIC P  AT VARIOUS  SEDIMENT DEPTHS  IN  LAKE  ONTARIO CORES'

Station
Identifier

52
24
30
60
14
41
GRb

83
92
75
92
62
75

32
45
45
Sampling
Date

21 JUN 72
6 NOV 72


9 OCT 73



21 JUN 72


6 NOV 72



21 JUN 72

6 NOV 72
Total P
0-5 5-10 10-15

911+111
955 890 900
888 685 610
548 500 500
737
755
825

1078
1195
1001+22
1270 966
950 980
1163 1103

1272
1461
1356 1028
Total Inorganic
15-20 0-5 5-10 10-15
Inshore Zone
891+108
1010 940 890 900
612 790 675 600
567 548 500 500
675
713
712
Rochester Basin
867
1000
871+.30
1140 860
810 945
1050 1020
Mississauga Basin
995
1176
1095 883
P Total Organic P
15-20 0-5 5-10 10-15

20+3
885 15 0 0
550 98 10 10
522 22 0 0
62
42
113

211
195
1 30+_53
130 100
140 35
113 83

278
286
261 195

15-20


125
62
45















-------

10
10

96

21
6

21

JUN
NOV

JUN

72
72

72

1444+65
1448 1108 1335

857+_24
Niagara
1229+85
1182 1218
Kingston
810+2
Basin

935 1132
Basin


214+_20
895 230 173

47+27


202 287


aSediment depth intervals in cm.   P concentrations  are  in  ug/g  sediment  on  a  dry-weight  basis.   Deviations
 shown are for two cores at the same station.   Average  deviations  for  five  cores  at  station  45 were  59,  50
 and 20 ug/g for total  P, total inorganic P,  and  total  organic  P,  respectively.


 The Genesse River.

-------
                           Table 2.   FORMS OF INORGANIC P IN LAKE ONTARIO SEDIMENTS
CTl

Phosphorus forms at various depths below sediment surface3
Station Sampling
Identifier Date
34 21 JUN 72
52
30 6 NOV 72
60
34
14 9 OCT 73
41
GRb

NaOH
2
4+1
28
8
3
4
5
14
0-5 cm
CDB
6
5+1
16
6
6
4
5
14

HC1
91
90+2
53
81
85
74
74
46
5-10
NaOH CDB


10 5
4 1
2 6


cm 10-15 cm
HC1 NaOH CDB HC1
Inshore Zone


72 8 6 82
95 2 4 91
86 2 5 97


15-20 cm
NaOH CDB HC1


6 7 88
2 4 95
2 8 88


Rochester Basin
83 21 JUN 72
92
75
62 6 NOV 72
92
75
30
33
46^5
22
37
40
17
14
6+1
18
15
17
48
41
42+J
57
36
29



15 18
30 15
50 11



65
50
32







-------
                                                 Mississauga Basin
    45    21  JUN 72      60   15    31
    32                   53   14    42
    45     6 NOV 72      46   16    29        45      8    35
                                                   Niagara Basin
    10    21  JUN 72      48+5  10+1   32+1
    10     6 NOV 72      50   19    22        51      7    35       50      6   32      58      8   39
                                                   Kingston Basin
    96    21  JUN 72      18+1  10+0   72+2

Concentrations expressed as per cent of  sediment total  inorgaic P.  Deviations shown are for two cores at
 the same station.   The average  deviations  between  5 separate cores at station 45 were 3, 1, and 3% for
 NaOH-P, CDB-P and  HC1-P, respectively.
 Genesse River.

-------
by Williams and Mayer (1972).   Stations 30,  GR,  62 and 96 were
exceptions (Table 2).   Station 30 and GR (Inshore Zone) contained
appreciable amounts of NaOH-P  and were more  similar to basin  sediments
than other Inshore Zone sediments.   Below 5  cm,  the P  distribution
at station 30 was similar to that for other  inshore stations.   Both
stations showed a relatively large decrease  in sediment water content
from the upper 5 cm core section to the 5 to 10  cm section (Table 3).
The trends for NaOH-P and sediment water content values may reflect
the deposition of some recent  sediments of high  P content over  the
coarse-textured materials generally found along  the southern  shore.
These trends are apparently variable along the southern shore,  as
stations 14, 41 and 60, also in the southern Inshore Zone, did  not
show a high proportion of NaOH-P in the upper 5  cm or  large decreases
in sediment water content with depth below the sediment surface.
Station 62, located near the Scotch Bonnet Sill, exhibited a  P
distribution and sediment water content intermediate between  the
postglacial muds and glaciolacustrine clays.  The sediment water
contents of the basin sediments were higher  than those observed for
the Inshore Zone (Table 3). Evidently, as a result of the higher
elevation of the sill, this region is not subject to deposition
of more recent sediments to the extent occurring in the surrounding
basins.  The proportion of NaOH-P was lower  in the Kingston Basin
(station 96) than in the other basins, suggesting less deposition
of recent high P content sediment in the Kingston basin.   Based on
P distribution changes with depth, sediments were generally uniform
over the upper 20 cm for the basin sediments (station  10) and the
Inshore Zone glaciolacustrine  clays (station 34).
The results obtained from inorganic P fractionation (Table 2) indicate
that the proportion of potentially chemically mobile inorganic  P
(NaOH-P) is high in the basin  postglacial muds and in  some regions of
the southern Inshore Zone, and is low in most southern Inshore  Zone
sediments and in the glaciolacustrine clays.  The NaOH-P fraction
is thought to include
                               IS

-------
   Table  3.  SEDIMENT WATER CONTENT OF LAKE ONTARIO CORES

                               fo/\

Station Sampling
Identifier Date
52 21 JUN 72
34 6 NOV 72
30
60
GRb 9 OCT 73
30
41
14
92 6 NOV 72
62
83
75
92 9 OCT 72
32 21 JUN 72
45 6 NOV 72
45 9 OCT 73
10 6 NOV 72
96 9 OCT 73
Water
Below
Content at Following Depths
the Sediment Surface9
0-5 cm 5-10 cm 10-15 cm
37+8
57+_l
52+2
26
35
42
26
27
60+3
51+6
68
76+2
69
73+1
75+1
SC
75+2
75
Inshore Zone

56^2
30+J
21
23
26
24
31
Rochester Basin
54+0
42+J
63
70+1
65
Mississaucja Basin
72
71+1
78
Rochester Basin
70+1
Kingston Basin
63

58
28
19







67

73


65

a% water = weight of water divided by weight of  water +  sediment.
 Deviations shown are for two or more cores  at the  same  station.


 Genesee River.
                              19

-------
inorganic P in equilibrium with inorganic P in solution based on
investigations of the nature of the inorganic P in this fraction
(Williams et a},. 1971 a; 1971 bj Syers et al_. 1973) and relationships
between the amounts of NaOH-P and isotopically exchangeable inorganic
P (Li et a]_. 1972).  Levels of sediment exchangeable inorganic P in
Lake Ontario sediments (Table 4) were in agreement with the chemical
mobility trends for inorganic P observed based on measurement of
inorganic P forms (Table 2).  The basin sediments contained a high
proportion of exchangeable P relative to the Inshore Zone sediments.
An exception was station 30 surface sediment which contained a higher
proportion of NaOH-P than other Inshore Zone sediments (Table 2), but
did not contain appreciable exchangeable inorganic P (Table 4).  The
level of NaOH-P for station 62 (22%) was intermediate between major
basin sediments (30 to 60%) and the glaciolacustrine clays (2 to 4%),
while the proportion of exchangeable P at this station was comparable
to that for the glaciolacustrine clays.  According to a map prepare
by Thomas Q a/L (1972), station 62 is located in the Scotch Bonnet
Sill which is composed of glaciolacustrine clay, while the basin
sediments are predominantly postglacial muds.  The results of inorganic
P fractionation and exchange investigations indicate that station 62
is more closely related to Inshore Zone sediments than to basin sediments.
While similar trends were observed for NaOH-P and exchangeable P the
proportion of exchangeable P was lower.  For example, the major basin
sediments contained 30 to 60% NaOH-P, but only 13 to 18% exchangeable
inorganic P.  Similar relationships were observed for sediments from
small lakes (Li 1973; Li et al. 1972).  These results indicate that
NaOH-P may overestimate the potentially mobile P fraction, or that
this fraction is underestimated by exchangeable P measurements in
some sediments (Li 1973).  Recent results (Sagher 1974) have shown
that algae are able to remove a high proportion of the NaOH-P fraction
from Wisconsin lake sediments, although removal was incomplete in
some cases.  This evidence supports the concept that NaOH-P corresponds
to the potentially mobile sediment inorganic P fraction.
                                    20

-------
Table 4.  SEDIMENT EXCHANGEABLE INORGANIC  P  IN THE 0 to 5 CM SEDIMENT
       LAYER OF LAKE ONTARIO CORES  OBTAINED  NOVEMBER 6, 1972

Station
Identifier

34
30
60

62
92
75

45
32b

10
31P Soln
ug/g

2.4
0.5
1.0

4.1
1.5
1.2

0.9
2.5

1.2
Sed Exch 31Pj3
ug/g %
Inshore Zone
13 1
9 1
20 4
Rochester Basin
29 4
167 15
193 18
Mississauga Basin
140 13
153 15
Niagara Basin
194 16
Total
ug/g

16
10
21

33
169
195

140
156

195
Exch Pj.
%

2
1
4

4
15
18

13
15

16
aSed exch Pj is expressed as percent of inorganic P  in  sediment phase;
 total exch PT is expressed as a percent of inorganic P in  the sediment
 and water phases.

Sampled June 21, 1972.
                                 21

-------
Lake Ontario sediments contained varying amounts of inorganic P  in
the CDB-P fraction.  The chemical forms of inorganic P in this fraction
are somewhat uncertain.  In soil inorganic P fractional on,  this
fraction (also termed "reductant soluble P") is attributed to P  occluded
in Fe oxides.  However, in lake sediments, the NaOH-P and CDB-P  may be
of similar nature and associated with hydrous Fe and Al oxides (Williams
et al_. 1971 c; Williams and Mayer 1972; Syers et al_. 1973).   In  terms
of chemical mobility, it is likely that the NaOH-P represents a  more
mobile inorganic P fraction than CDB-P in the sequential  extraction
scheme.
Large amounts of inorganic P were present as HC1-P.  This fraction
accounted for about 90% of the inorganic P in the glaciolacustrine
clays (stations 34 and 52).  The HC1-P fraction contains  mainly  apatite
(Williams and Mayer 1972; Syers et a]_. 1973).  The concept that  this
fraction is immobile is supported by investigations of uptake of
sediment inorganic P by algae (Sagher 1974).  Algae were unable  to
utilize sediment inorganic P contained in this fraction.
The combined amounts of sediment inorganic P contained in the three
inorganic P fractions  (NaOH-P, CDB-P, HC1-P) were frequently less
than the total inorganic P content of the sediment (Tables 1 and 2).
This occurred because the fractionation scheme used was not intended
to provide complete recovery of total inorganic P.  More comprehensive
fractionation schemes  (Williams eib aj_. 1971 a; 1971 b) involve
determination of residual inorganic P following HC1-P extraction, but
residual inorganic P was not of interest in this investigation of
inorganic P mobility.
INTERSTITIAL INORGANIC P
Levels of interstitial inorganic P (mobile P) ranged from 14 to  1280
ug/1.  Concentrations were usually higher in the basin than in the
inshore sediments  (Table 5).  This trend was in agreement with the
high proportion of potentially mobile inorganic P in the basin sediments
(Table 2).  The glaciolacustrine clay sediments (station 34) exhibited

                                 22

-------
     Table 5.   INTERSTITIAL  INORGANIC  P  IN  LAKE ONTARIO SEDIMENTS

Station
Identifier
34
14
30
41
GRb
60
62
75
92
45
10
96
Interstitial Inorganic P at Followi
below the sediment surface (cm)a
Lakewater
15
3
15
18
4
8
20
19
16
25
20
19
0-3
19
249
498
92
158
83
1050
1070
145
1260
140
1280
3-6 6-9
Inshore Zone
14 14
592 252
569 392
115 50*
47* 311
58 69
Rochester Basin
1010 954
1040 899
55 87
Mississauga Basin
537 693
Niagara Basin
446 684
Kingston Basin
1040 1160
ng Depths
9-12
14
67
37*
33*
663
133*
382
997
107
422
90
637

12-15
28
22*
116*
in*
182
39*
444
1190
46
749
99
537
aFor values indicated by *, the time required to separate the
 interstitial  waters was greater than one-half hour.

 Genesee River.
                                23

-------
the lowest IIP values, and these sediments  also contained  a  high
proportion of HC1-P (immobile P).   Southern Inshore Zone sediments
contained higher IIP levels than station 34, but the values  were
generally lower than for basin sediments.
For basin sediments, IIP values for the surface 3 cm were  generally
in the range of 1000 jug/1.  However, stations 92 and 10 were exceptions,
even though the proportion of potentially mobile inorganic P for  these
stations were comparable to other basin stations.  The lower IIP  values
at stations 92 and 10 may reflect differences in sediment  characteristics,
most likely Eh, or changes in IIP during analysis.   However, the  trend
of lower values at these stations for all  depths suggests  that  IIP
concentrations were lower at stations 92 and 10 than at other basin
stations.
The IIP levels in the 0 to 3 cm section were usually higher  than  in
the 3 to 6 cm section.  However, below the 3 to 6 cm a clear trend
in IIP levels was not apparent.  The decrease in IIP between the
6 to 9 and 9 to 12 cm sections at stations  14, 30, 62 and  10 was
possibly a result of storing these sections during squeezing IIP
from the first 3 sections (Table 5).  Alternatively, the unusually
long squeezing time required to obtain sufficient interstitial  water
for analysis of these sections may have contributed to the low  values.
Intentional excessive handling, storage and exposure of sediments to
air prior to obtaining interstitial water was shown to have  a major
effect on IIP values.  Sediments from stations 92 and 10  (a  mixture
of the upper 9 cm) were analyzed after storage in plastic  bags
exposed to air for various periods of time (Table 6).  IIP values
decreased with increased storage time.  Handling of these  sediments
prior to the initial analysis caused the IIP value to be lower  than
values obtained for the individual sections taken directly from the
cores (Table 5).  The likely explanation for the effects of  storage
and excessive handling of sediments on IIP levels is the oxidation
of dissolved and solid phase Fe and subsequent sorption of inorganic P.
                                24

-------
  Table 6.   EFFECT OF SEDIMENT STORAGE ON  INTERSTITIAL INORGANIC
                             P VALUES

Storage Time,                        Interstitial  Inorganic P,
   min                                       jug/1

                                           Station  92
     0                                        85
    90                                        55
   600                                        33

                                           Station  10
  0-10                                        20
 15-30                                        12
 34-44                                        21
 67-80                                        14
100-110                                       12
                                25

-------
IIP values in successive aliquots from the Reeburgh squeezer
indicated that the peak IIP value was obtained in the 9 to  12  ml
aliquot for most stations (Table 7).   A gradual  initial increase
followed by a decrease in IIP values  in successive aliquots from  the
Reeburgh squeezer was also reported by Bray et_ afL (1973) and  Weiler
(1973).  Since the 6 to 9 ml aliquot was used in this investigation,
the IIP values were probably underestimates of in situ values.
Measurements of interstitial Fe were made to evaluate whether  sediments
were sufficiently reduced for reduction of Fe3+ to Fe2+ to  occur  and
thereby affect IIP concentrations.  The values observed were higher
than for the overlying lake water, but were highly variable between
sediments (Table 8).  Interstitial Fe levels were similar to those
reported by Weiler (1973) for comparable locations.  Apparently,
some Fe2+ was present in most of the sediments, but the concentrations
varied due to differences in Eh, Fe content, and/or distribution  of
Fe between the solid and solution phases.
DESORPTION AND SORPTION OF SEDIMENT INORGANIC P
The desorption and sorption of inorganic P by Lake Ontario  sediments
were investigated to provide information on the ability of  sediments
to control or "buffer" the dissolved inorganic P (DIP) concentration
in the surrounding water upon addition or removal of inorganic P  in
the water phase of sediment-water systems.  It was necessary to conduct
desorption-sorption in sediment-water suspensions containing a lower
sedimentrwater ratio than that found for undisturbed lake sediments.
A  1:25 sediment:water ratio  (dry weight sediment basis) equilibration
system was used, while for Lake Ontario sediments, the sediment:water
ratio ranged from about 3:10 to 3:1.   Furthermore, in spite of efforts
to transport and store sediment samples without exposure to air and
to conduct desorption-sorption experiments under oxygen-free conditions,
it was observed that DIP concentrations tended to decrease  with
                                                               PI
storage of sediments, apparently due to partial oxidation of Fed   and
sorption of dissolved inorganic P.  Consequently, desorption-sorption
                                26

-------
Table 7.  INTERSTITIAL INORGANIC P IN SUCCESSIVE ALIQUOTS
           SQUEEZED FROM LAKE ONTARIO SEDIMENTS
Aliquots
ml
0-3
3-6
6-9
9-12
12-15
6-9
9-12
12-15
0-3
3-6
6-9
Interstitial
the Sediment
0-3
810
1180
1070

1120
537
557
542
33
94
83
Inorgani
Surface
3-6
130
706
1040
1080
981
1260
1300
1180



c P at Following Depths
(cm)
6-9 9-12
Station 75
112 201
619 781
899 997
1022 1010
1048 885
Station 45



Station 60



Below
12-15
368
978
1190
1080
847






                            27

-------
       Table 8.   TOTAL  FILTERABLE  Fe  IN THE INTERSTITIAL WATER
                   OF SEDIMENTS FROM  LAKE ONTARIO
                               (mg/1)

Station
Identifier
34
14
30
41
GRb
60
62
75
92
Interstitial Fea at the Following Depths Below
Sediment Surface (cm)
0-3
0.5
3
3
1
5
8
0.3
4
6
3-6
0.4
4
7
1
6
1
0.2
4
13
6-9
Inshore Zone
0.4
16
8
1
25
1
Rochester Basin
0.3
5
21
9-12
0.4
12
3
1
46
7
0.4
4
27
the
12-15
0.3
9
7
3
37
1
4
7
31
Mississauga Basin
45
10
96
3
1
1
6
1
1
9
Niagara Basin
2
Kingston Basin
12
9
2
13
14
2
15
Concentrations in  the  lake  bottom water were less than 0.3 mg/1.
 Genesee River.
                               28

-------
experiments provided information on comparative trends for sediments
from different sites, but the equilibrium inorganic P concentrations
are not directly comparable to IIP levels.
Initial desorptions were conducted in distilled water (Tables 9 and 10).
Amounts of inorganic P desorbed appeared to decrease with increasing
depth below the sediment surface with the largest change occurring
between the 0 to 5 and 5 - 10 cm section (Table 9).  However, the
sediment samples from the 5 to 10 cm section were stored 3 weeks
longer than the 0 to 5 cm section before equilibrating, and storage
effects may have contributed to the observed changes.  Sediment from
the 0 to 5 cm sections of stations 45, 75 and 10 equilibrated in
separate experiments several weeks apart demonstrated a large decrease
in desorption valuesfor the second equilibration of the same sediment
samples (Tables 9 and 10).  Values for DIP increased during successive
desorption steps in some cases (Tables 9 and 10), in contrast to the
gradual decrease expected based on sorption-desorption isotherms.  This
suggested that some fine particles were not removed from suspension
by the centrifugation procedure and that these particles reacted in
the measurement of inorganic P.  To evaluate this possibility, an
experiment was conducted to compare inorganic P concentrations in
distilled water and O.W NaCl systems after centrifuging and filtering
the supernatant solution.  The 0.1M_ NaCl was added to flocculate the
sediment.  Comparisons were made for samples centrifuged twice
(double centrifuge) or filtered through 0.45, 0.22, or 0.10 jum
Millipore filters following the double centrifugation steps (Table 11).
In sediment from station 75 equilibrated in distilled water the level
of inorganic P in solution increased with each desorption step.  The
values were decreased somewhat by filtration, but even for the 0.10 urn
filter, the concentration after the third equilibration was four times
that of the first equilibration.  In the 0.1M. NaCl system, small
increases in values occurred with successive equilibrations and small
decreases were observed with decreasing pore size of the filter.  These
results suggest that the sediments tended to disperse in the distilled
                                29

-------
 Table 9.  DESORPTION OF INORGANIC P FROM LAKE ONTARIO SEDIMENT
       AFTER SUCCESSIVE EQUILIBRATIONS  IN DISTILLED WATER
                               (>jg/g)a

Station Sediment
Identifier Section,
cm
34
52
30
60
75
83
62
92
45
10
0-5
5-10
10-15
0-5
5-10
0-5
5-10
0-5
5-10
0-5
5-10
10-15
0-5
5-10
0-5
5-10
0-5
5-10
0-5
5-10
0-5
5-10
Inorganic P Desorbed in Successive Equilibration
steps
1st
2.5
2.0
l.C
2.7
1.8
6.1
1.0
1.4
0.8
9.8
6.4
5.0
1.6
0.6
4.3
4.5
3.4
1.5
23.0
2.0
7.6
1.8
2nd
2.5
1.3
2.4
1.9
14.1
1.2
2.6
1.0
16.6
10.8
6.0
1.0
5.1
4.6
8.0
2.6
3.6

3rd 4th 5th
Inshore Zone
3.4 2.4 2.0
1.5 1.2 1.2
1.8 1.8 1.6


Rochester Basin
10.2 2.3 2.4
2.6 1.8 1.9


Mississauga Basin
5.8 6.2 6.5
Niagara Basin
6th
2.0
1.0
1.6


2.3
2.1


6.1

6.0
ug/1  = 40 x ug/g.
                                      3C

-------
Table 10.  DESORPTION OF INORGANIC P FROM THE 0 TO 5 CM SEDIMENT SECTION
OF LAKE ONTARIO CORES AFTER SUCCESSIVE EQUILIBRATIONS IN DISTILLED WATER
                                 (jjg/g)a

Station
Identifier

34
34b
30
60

75
75b
92
62

Inorganic P Desorbed in Successive Equilibration Steps
1st

2.6
1.3
0.8
1.2

2.0
1.5
1.3
4.5

2nd

3.9
1.2
2.2
2.2

4.9
2.5
3.2
5.1

3rd
Inshore
4.8
1.4
4.7
2.1
Rochester
8.8
2.7
3.8
4.4
f'iississauga
4th 5th
Zone
3.8 4.4
3.1 2.6
4.6
2.0 1.5
Basin
10.0 11.6
3.8 3.8
5.2 4.2
4.4
Basin
6th


1.8



9.1
4.4



   45
   10
1.8
1.6
4.5
4.9
7.1
Niagara Basin
7.3       9.6
9.6
 jug/1 = 40 x jjg/g.

 Oxic condtions  (contact with  oxygen  was  not  limited  during procedure).
                                  31

-------
 Table 11. DETERMINATION OF THE EFFECT OF 0.1 M NaCl SOLUTION ON
DESORPTION OF INORGANIC P IN SEDIMENT SUSPENSION OF SEDIMENT FROM
             THE 5 TO 10 CM CORE SECTION OF STATION 75
Filter
Pore
Sizeb
jjm
Double Centrifuge
0.45
0.22
0.10
Double Centrifuge
0.45
0.22
0.10
Inorganic P Desorbed In Foil
Equilibrations^

First
47+3
55+3
45+_l
40+0
43+1
34+2
33+3
28+0

Second
Distilled Water
162+3
161+5
98+_2
82+_5
.1 M NaCl Solution
50+1
42+_7
40+2
27+1
owing Successive

Third
222+20
216+5
154+8
152+3
53+1
46+10
40+3
28+2
    = Aig/l-r-40; error values are average deviation for triplicate
samples.

 Filtered  samples centrifuged twice prior to filtration.
                                32

-------
water system and that an appreciable amount of the dispersed sediment
was less than 0.10 jum diameter material.  The Q.lf4 NaCl system was
effective in flocculating the sediment, although some particulate
material apparently remained after double centrifugation.  Other
data obtained after equilibration in distilled water and filtration
through various pore size filters following double centrifugation
indicated that dispersion also occurred for other sediments (Table  12).
Values for the first equilibration suggest that the 0.1M_ NaCl did
not cause appreciable desorption or sorption of inorganic P (Table  11).
Concentrations in the double centrifuged samples were similar for
NaCl and distilled water systems.  The tendency for dispersion in
the distilled water system apparently increased as dissolved ions
were washed out in successive equilibrations, and dispersion was
unimportant in the first equilibration.  Based on these results, it
was concluded that relationships between DIP and sediment inorganic P
during successive equilibrations could be evaluated more accurately
in the O.IM^ NaCl than in distilled water.
The amounts of inorganic P in solution after the first equilibration
ranged from 0.6 to 35.8 jug/g for the various Lake Ontario sediments
investigated  (Table 13).  This corresponds to a concentration range
of 24 to 1432 ug/1.  Except for stations GR, 41 and 92, these values
were somewhat less than the IIP values observed for these sediments
(Table 5).
Desorption of inorganic P was usually greater for the sediment from
0 to 5 cm section  (Table 13).  Amounts of inorganic P desorbed were
higher for basin sediments than inshore sediments.  Inorganic P
levels in the second equilibration of sediment from the 0 to 5 cm
section were  usually lower than the  levels in the first equilibration.
This was most evident for station 30 and the Genesse River station of
the  Inshore Zone and all of the basin stations.  Small decreases
usually occurred between the second  and third equilibrations.
Desorption usually increased slightly between the first and second
                                 33

-------
Table 12.  EFFECT OF FILTER PORE SIZE ON INORGANIC P DESORPTION VALUES FOR
 SEDIMENT FROM THE 0 TO 5 CM SECTION OF LAKE ONTARIO CORES SUSPENDED IN
                           DISTILLED WATER
                                     a
Filter Pore Size
Inorganic P Desorbed in Successive
Equilibration Steps
/urn

Double Centrifuge
0.45
0.22
0.10

Double Centrifuge
0.45
0.22
0.10

Double Centrifuge
0.45
0.22
0.10
First
Station 30
17
18
17
19
Station 34
117+2
116+4
108+0
90+1
Station 75
33+1
28+1
31+2
30+J
Second

50+2
53+_3
44+4
42+4






110+4
109+6
86+5
71+6
a,ug/g = /jg/1 -f-40; deviations are average deviations for triplicate
  samples.

Filtered samples centrifuged twice prior to filtration.
                                    34

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Table 13.  DESORPTION OF INORGANIC P FROM LAKE ONTARIO SEDIMENT AFTER



        SUCCESSIVE EQUILIBRATIONS IN A 0.1 M NaCl SOLUTION3

Inorganic P
Station
Identifier

60
30
GRb
14
41
34

92

45

96
Desorbed In Successive Equilibration Steps
0-5 cm
1st

1.
4.
7.
2.
4.
0.

35.

20.

12.

5
0
7
3
0
6

8

1

3
2nd

1.
1.
2.
1.
4.
0.

15.

10.

6.

8
8
8
9
5
8

8
Mi
4

8
layer
3rd
Inshore Zone
0.9
1.2
5.0
2.4
3.6
0.8
Rochester Basin
13.6
ssissauga Basin
11.0
Kingston Basin
5.1
5-10
1st

1.
2.
1.
1.
1.
0.

6.

13.

2.

2
2
4
8
4
2

1

3

0
cm
2nd

1
2
3
3
1
0

7

11

3

.4
.8
.1
.1
.8
.2

.3

.3

.2
layer
3rd

1.
2.
3.
4.
1.
0.

5.

1.

3.

1
7
5
1
4
2

8

3

4
 >g/l  =  40  x >jg/g.
  Genesee  River.
                                  35

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equilibrations for the sediment from the 5 to 10 cm sections.   Similar
amounts of P were desorbed during the second and third equilibrations
of the 5 to 10 cm section, except for station 45.
Although the concentrations of inorganic P in solution after each
equilibration were appreciable, the amounts of P desorbed were small
compared to the amounts of potentially mobile P in the sediments.
The combined amounts of P desorbed during the three successive
equilibration steps correspond to about 3 to 17% of the NaOH-P.
This reflects the low ability of water to act as a "sink" for sediment
P and that multiple desorptions would be required to completely desorb
the potentially mobile P fraction.
Most desorption experiments were conducted under conditions chosen to
minimize changes in sediment Eh.  These sediments are designated as
"unchanged."  For comparison, desorption was also evaluated under
oxic (exposed to air) and anoxic (equilibration at room temperature
for 11 days) conditions for several sediments equilibrated in 0.1M.NaCl
(Table 14).  For Inshore Zone sediments, the amounts of P desorbed
under oxic conditions were similar for the different sediments and
were somewhat lower than amounts desorbed from "unchanged" sediments
(Table 13).  Desorption increased slightly under anoxic conditions.
For the basin sediments, desorption was considerably less for oxic
than for "unchanged" sediments.  Sediments equilibrated in distilled
water also gave higher P desorption values for the "unchanged"
conditions as compared to oxic conditions (Table 10).  Apparently,
the conditions for "unchanged" sediments were intermediate between
oxic and anoxic conditions.  The anoxic values likely reflect the
effect of reduction of Fe^+ to Fe^4" and resulting desorption of
inorganic P.  Whether these sediments became sufficiently reduced to
promote complete reduction of Fe^+ was not determined.  Possibly, with
addition of a carbon energy source for sediment microorganisms, a
further decrease in sediment Eh and release of inorganic P would have
occurred.  This may explain the low desorption value for station 75
sediment under anoxic conditions.
                                36

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Table 14.  DESORPTION OF INORGANIC P FROM SEDIMENT IN THE FIRST 5 CM
 SECTION OF LAKE ONTARIO CORES AFTER SUCCESSIVE EQUILIBRATIONS IN A
         .1 M NaCl SOLUTION UNDER OXIC OR ANOXIC CONDITIONS

Station
Identifier

60
GRb
14
41

92
75
Oxic Equil
First
Inshore
0.3
1.2
1.2
1.7
Rochester
2.4
0.7
ibrations
Second
Zone
0.5
1.8
0.8
2.2
Basin
3.6
1.7
Anoxic Equilibration

0.9
1.4
1.3
3.6

56.2
3.5
    45
Mississauga Basin
 0.9           0.6
32.1
 jug/1  =  40  xjug/g.
 Genesee  River.
                                  37

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Sorption of added Inorganic P was investigated to evaluate the
ability of sediments to "buffer" the interstitial water inorganic P
concentration upon addition of inorganic P.   Sorption of added
inorganic P was evaluated by adding inorganic P to sediments  suspended
in distilled water (1:25 sediment:water ratio).  In most cases,  the
Inshore Zone sediments sorbed less  than the  basin sediments (Tables
15 and 16; Figure 2) Stations 30 and 62 were exceptions.   Station 62
was similar to Inshore Zone sediments, while station 30 (surface 5 cm)
resembled basin sediments.   These trends correspond to chemical  mobility
characteristics.  Little change in  sorption  ability was observed with
depth below the sediment surface as discussed previously for  these
sediments (Table 15).  At levels of added inorganic P comparable to  the
interstitial water and bottom lake  water concentrations (2.5  to  25 ug/g),
the basin sediments sorbed  most of the inorganic P.  However, the
amounts of P remaining in solution  at equilibrium sometimes exceeded
the values of DIP found in  the water column  of Lake Ontario (Shiomi
and Chawla 1970).
For inshore sediments (34,  60), equilibrium  DIP values increased
sharply upon sorption of low amounts of inorganic P and exceeded
observed IIP values (Table  5) for these sediments (Figure 2).  For
basin sediments, there was  little change in  equilibrium DIP values
upon sorption of up to 100  ug/g of added inorganic P.  These  results
indicate that addition of inorganic P (e.g., through mineralization
of organic P) to inshore sediments  could increase IIP values
considerably, but would have little effect on IIP levels in basin
sediments.
Sediments which sorbed the  most inorganic P  during the sorption  step
(basin sediment) usually released the least  P during a subsequent
desorption step (Table 17).  Consequently, the net sorpticn of added
inorganic P, expressed as a percentage of the total added P,  was
usually higher for basin sediments, than the inshore zone sediments.
Station 62 was an exception in that the net  sorption was  comparable
to inshore zone rather than other basin sediments.  This  is in
                                38

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 Table 15.   SORPTION  OF ADDED  INORGANIC P BY LAKE ONTARIO SEDIMENTS



                       OBTAINED JUNE  21, 1972

Station Core
Identifier Section,
cm

34 0-5
5-10
52 0-5
5-10
10-15

92 0-5
75b 0-5
75 5-10

32 0-5
5-10
10-15
Added P Sorbed (%) For Added P
Level (jug of P per g)a of
2.5

80
83
73
93
95

100
100
100

100
100
100
25
Inshore
80
72
60
78
85
Rochester
98
88
93
Mississauga
100
100
95
250
Zone
48
41
24
50
57
Basin
82
82
79
Basin
87
48
89
2500

20
25
17
37
31

52
52
48

57
46
52
ajug/liter = ^g/g x 40.




 Sediment in  3% sediment suspension
                                 39

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Table 16.  SORPTION OF ADDED INORGANIC P BY LAKE ONTARIO SEDIMENTS
   FROM THE 0 TO 5 CM CORE SECTIONS OBTAINED NOVEMBER 6, 1972

Station
Identifier

34
30
60

92
62
75

45
Added
6.25

71
100
91

100
66
93

98
P Sorption (35) For Added
12.5 25
Inshore Zone
70 65
98
89
Rochester Basin
98
66
98 98
Niagara Basin
99
P Level
50

59
99
75

98
53
98

99
Oig/g)a Of
100


99
62

98
46


99
ajug/l = 40 x >jg/g.
                               40

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        200
400
600
800
1000
1200
I40O
1600
                    Dissolved  Inorganic P in
Figure 2.  Inorganic  P Sorption Curves for Lake Ontario Inshore and Basin Sediments.

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Table 17.   DESORPTION OF ADDED INORGANIC  P  BY  SEDIMENTS  IN THE
0 TO 5 CM  SECTION OF LAKE ONTARIO CORES OBTAINED  NOVEMBER 6, 1972



Station
Identifier

60

62
92
Add P Desorbed as
Added P Sorbed
% Net Added P Sorbed

% Total
For The Added Levels of
6.25 25 50

32

8
4
100
Inshore

Rochester


Mississauga
6.25
Zone

Bas i n


Basin
Added P
tog/g)a
25 50

51

49
94

as


100






 45
1       2       92
98    98
97
          x 40.
                              42

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agreement with the chemical mobility characteristics discussed
previously.  Because these experiments were conducted in distilled
water, values were corrected for sediment dispersion based on
control samples.
P RELEASE FROM INTACT CORES
Dissolved inorganic P (DIP) was released to the overlying lake  water
from intact sediment cores under controlled laboratory conditions
(Figures 3 and 4).  The initial levels of DIP in the lake water were
low (0 to 2 pg/1), but began to increase after several days of
incubation.  The effects of lowering the levels of dissolved oxygen
(to about 3 mg/1) in the overlying lake water by stripping with N
were inconsistent.  P release from the station 10 core aerated  with
air was greater than for the duplicate core treated with Ng after
35 days (Figure 4).  Release from the air-treated core from station 60
was lower prior to the introduction of N2 into the duplicate core at
35 days.  However, P release appeared to be related to N treatment
for stations 10 (Figure 3) and 30 (Figure 4).  The rate and extent
of P release might have increased if tne overlying water had been
anaerobic.  Apparently the Eh of the sediment decreased sufficiently
with time to allow increased rates of P release, although the water
column for some cores was saturated with air.  These conditions exist
in the bottom waters of Lake Ontario, where mean dissolved oxygen
levels of about 12 mg/1 have been measured during the summer (Dobsin
1967).
The highest levels of P obtained in the overlying lake water ranged
from 5 to 250 jjg/1 (Figures 3 and 4).  However, only cores from
stations 34 and 10 (Figure 3) had maximum values below 10/ug/l, and
most cores gave maximum values between 30 and 90/jg/l.  The levels of
P released reached lOjug/1 or higher between 12 and 25 days of
incubation for most cores, and surpassed the mean concentration of
about 11 jug/1 for "soluble phosphate" in Lake Ontario bottom waters
(Shiomi and Chawla 1970).

                               43

-------
   40
    30
    20
-  .0
OL
o
 O
 M
    30
    2O-
     10
Station  10
 N2   -
Air   .-.
Control -^>-
           Station  75
           Station  45
           Station  34
               to
             20       30       40       50
              Incubation  Time  in  Days
                                                           60
       Figure  3.   Levels of Dissolved  Inorganic P Released from Intact
                   Cores Obtained November 6, 1972
                                   44

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   250




   200




    ISO




    100




    80




    60




    40




    20
Q.



o

'c
O
o
o


s
to
IOO




 80




 60




 40




 20



  0





IOO




 80




 60




 40




 20
Station 30
                                                          TIT-
                                                       ^ ^


                                                      *Air  N2
            Station 6O
                                                Air-, N2
            Station 10
                10        20       30        40       50


                        Incubation  Time  in  Days


        Figure 4.   Levels of Uissc-iveu  Inorganic  P  Released from Intact

                   Cores Obtained October 9,  1973;  for Cores Designated

                   Air, -,>, the  NZ was  Ir.troduced  after 35 Days.



                                  45

-------
Rates of P release were calculated for cores treated with air,
since the bottom waters of Lake Ontario contain high concentrations
of dissolved oxygen (Dobsin 1967).  Rates were calculated based on
the increase in DIP in the overlying water between days 12 and  33 of
the incubation period; a constant release rate was assumed.  This
interval represented a period following the initial lag and prior
to the marked changes in rates occurring with continued incubation
for several cores.  The calculated release rates ranged from about
0.03 mg m~2 day"  for stations 34 and 45 to 0.8 mg irf^ day"  for
station 30.  The average rate for the 7 cores investigated was  about
0.2 mg m"2 day"1.
It was observed that the calculated release rates were not related
to IIP values measured for the upper 3 cm of these cores after
incubation.  A direct relationship might be expected if release
were controlled by diffusion of IIP to the overlying water.  However,
IIP values may have changed between day 33 and day 62, the end  of the
incubation period.  Furthermore, an IIP concentration gradient  may
exist within the upper 3 cm.  Finally, the volume of water over the
sediment cores was relatively small, and DIP concentrations may have
been controlled by sorption-desorption reactions at the exposed
sediment surface as well as by diffusion of IIP from the sediment.
For deep lakes like Lake Ontario, the physical mobility of sediment P
is likely controlled mainly by the diffusion of IIP from the sediments
to the overlying water.  Little disturbance due to bottom currents is
expected in the deep basins although wave action and currents are
likely important in shallow near-shore areas (Williams and Mayer 1972).
Some disturbance of the sediment-water interface by benthic organisms
may occur, but less benthic activity occurs in the deep sediments than
in shallow water regions (Kemp et aj_. 1972).
Rates of diffusion of IIP from Lake Ontario sediments were estimated
from IIP values measured in sediment cores, based on a DIP concentration
of 10 jug/! in the overlying water (Shiomi and Chawla 1970), Fick's first
                                 46

-------
law of diffusion, and a diffusion coefficient of 10~6 cm2  sec'1
(Stumm and Leckie 1971).  The value of the diffusion coefficient
is somewhat uncertain (Weiler 1973).  For an IIP range of  about 100
to 1000 ug/1 for the upper 3 cm of sediment (Table 10),  the  estimated
diffusion rates range from about 0.05 to 0.6 mg nr2 day  .   This  is  in
agreement with the range of 0.03 to 0.8 mg m~2 day"1 estimated from
cores incubated in the laboratory.  While the two different  approaches
of estimating the physical mobility of sediment P are in agreement,
the calculated rates may be inaccurate for several reasons:   the
diffusion coefficient may be inaccurate; the upper value may over
estimate rates for basin sediments, as IIP concentration gradients
may exist in the upper 3 cm; the lower range may underestimate release
from near shore sediments due to mixing by wave and current  action,
and benthic organisms.  However, the rates obtained provide  a basis
for evaluating the impact of sediment inorganic P release  on the
overlying lake water.
The annual contribution of sediment inorganic P to the P content  of
the overlying water can be estimated based on the inorganic  P flux
of 0.2 mg m~2 day"  (mean for incubated cores) and a sediment area
of 19,000 km2 (Williams and Mayer 1972).  The estimated annual
contribution is 1.4 x 10^ kg of P per year.  This compares to an
estimated annual loading from external sources of 1.3 x 10?  kg per
yr; about one-half of this arises from municipal waste waters
(Great Lakes Water Quality Board, 1973).  Thus, the estimated sediment
contribution is about 10% of the external P loading.  The  estimated
annual P release from sediments would correspond to about  5% of the
potentially mobile inorganic P (NaOH-P) in the upper 3 cm  of sediment.
                               47

-------
                            SECTION VI
                            REFERENCES
Bannerman,  R.T.   1972.   Interstitial Inorganic P in Lake Wingra
   Sediments.   M.S.  Thesis,  University  of Wisconsin, Madison.
Bray, J.T., O.P.  Bircker,  and B.N.  Troup.  1973.  Phosphate  in
   Interstitial  Waters  of  Anoxic Sediments:   Oxidation Effects  During
   Sampling Procedure.   Science 180: 1362-1364.
Callender,  Edward.  1969.   Geochemical  Characteristics of Lake
   Michigan and Superior Sediments.  Proc. 12th Conf. Great  Lakes
   Res., Internat. Assoc.  Great Lakes Res.,  pp.  124-160.
Chang, S.C., and M.L.  Jackson.  1957.  Fractionation of Soil
   Phosphorus.  Soil Sci.  84: 133-144.
Delfino, J.J., G.C.  Bortleson, and G.F. Lee.  1969.  Distribution
   of Mn, Fe,  P, Mg, K, Na,  and Ca in the Surface Sediments  of  Lake
   Kendota, Wisconsin.   Environ. Sci. Technol. 3: 1189-1192.
Dobson, Hugh H.   1967.   Principle Ions and Dissolved Oxygen  in  Lake
   Ontario.  Proc. 10th Conf. Great Lakes Res., Internat. Assoc.
   Great Lakes Res., pp. 337-356.
Great Lakes Water Quality Board.  1973.  Great Lakes Water Quality,
   Annual Report to International Commission.
Kemp, A.L.W.,  and C.F.M. Lewis.  1968.   A Preliminary Investigation
   of Chlorophyll Degradation Products in the Sediments of Lake Erie
   and Ontario.  Proc.  llth Conf. Great Lakes Res., Internat. Assoc.
   Great Lakes Res., pp. 206-229.
Kemp, A.L.W.  1971.  Organic Carbon and Nitrogen in the Surface
   Sediments of Lakes Ontario, Erie end Huron.  J. Sed. Petrology.
   41: 537-548.
Kemp, A.L.W.,  anc A. Murdrochova.   1571.  Electrodialysis:  A
   Method for Extracting Available Nutrients in. Great Lakes  Sediments.
   Proc. 14th Conf. Great Lakes Res.,  Internat. Assoc. Great Lakes
   Res., pp. 241-251.

-------
Kemp, A.L.W., C.B.O.  Gray, and A. Murdrochova.  1972.  Changes
   in C, N, P and S in the Last 140  Years in Three Cores  from Lakes
   Ontario, Erie and Huron.  In:  Nutrients in Natural  Waters,
   Herbert E. Allen and James R. Kramer (Ed.).  New York:Wiley-Interscience,
   pp. 251-280.
Lee, G.F.  1970.  Factors Affecting  the Transfer of Material Between
   Water and Sediments.  Eutrophication Information Program, University
   of Wisconsin, Madison.  Occasional Pap. 1.
Li, W.C., D.E. Armstrong, J.D. Williams, R.F. Harris, and J.K.  Syers.
   1972.  Rate and Extent of Inorganic Phosphate Exchange in Lake
   Sediments.  Soil Sci.  Soc. Amer.  Proc. 36: 279-285.
Li, Wan C.  1973.  Exchangeable Inorganic Phosphate in Lake Sediments.
   Ph.D. Thesis, University of Wisconsin, Madison.
Li, Wan C., David E. Armstrong, and Robin F. Harris.  1973.
   Measurement of Exchangeable Inorganic Phosphate in Lake Sediments.
   Environ. Sci. Techno!. 7: 454-456.
Mehta, N.C., J.O. Legg, A.I. Goring, and C.A. Black.  1954.
   Determination of Organic Phosphorus in Soils.  I.  Extraction
   Method.  Soil Sci. Soc. Amer. Proc. 18: 443-449.
Murphy, J. and J.P. Riley.  1962.  A Modified Single Solution  Method
   for the Determinations of Phosphate in Natural Water.   Anal.
   Chim. Acta. 27: 31-36.
Reeburgh, W.S.   1967.  An  Improved Interstitial Water Sampler.
   Limnol. Oceanogr. 12:  163-165.
Rohlich, G.A.  1963.  Origin and Quantities of Plant Nutrients  in
   Lake Mendota.   In:  Limnology of North America.  D.G.  Frey  (Ed.).
   University  of Wisconsin  Press, Madison, pp. 75-87.
Sagher, A.   1974.  Microbial Availability of  Phosphorus in Lake
   Sediments.  M.S. Thesis, Department of Soil Science, University
   of Wisconsin, Madison.
                                 49

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Shiomi, M.T., and V.K. Chawla.   1970.   Nutrients in Lake Ontario.
   Proc. 13th Conf. Great Lakes Res, Internet.  Assoc.  Great Lakes
   Res., pp. 715-732.
Sommers, L.E., R.F. Harris, J.D.H.  Williams, D.E. Armstrong, and
   J.K. Syers.  1972.  Fractional on of Organic Phosphorus  in Lake
   Sediments.  Soil Sci. Soc.  Amer. Proc. 36: 51-54.
Stumm, W., and J.O. Leckie.  1971.   Phosphate Exchange with Sediments;
   Its Role in the Productivity of Surface Waters.  Proc. 5th Int.
   Water Pollution Res. Conf., (in  press).
Syers, O.K., R.F. Harris, and D.E.  Armstrong.  1973.  Phosphate
   Chemistry in Lake Sediments.  J. Environ. Qua!. 2:  1-14.
Thomas, R.L., A.L.W. Kemp, and C.F.M.  Lewis.  1972.  Distribution,
   Composition and Characteristics of the Surficial Sediments of Lake
   Ontario.  J. Sed. Petrology. 42: 66-84.
Watanobe, F.S., and S.R. Olsen.  1962.  Color-metric Determination of
   Phosphorus in Water Extracts of Soil.'. Sdil  Sci. 93: 183-188.
Weiler, R.R.  1973.  The Interstitial  Water Composition in the Sediments
   of the Great Lakes.  1.  Western Lake Ontario.  Limnol.  Oceanogr.
   18: 918-931.
Williams, J.D.H., J.K. Syers, and T.W. Walker.   1967.   Fractionation
   of Soil  Inorganic Phosphate by a Modification of Chang and Jackson's
   Procedure.  Soil Sci. Soc. Amer. Proc. 31: 736-739.
Williams, J.D.H., J.K. Syers, R.F. Harris, and D.E. Armstrong.  1970.
                                                  >
   Adsorption and Desorption of Inorganic Phosphorus by Lake Sediments
   in a 0. NaCl System.  Environ. Sci. Technol. 4: 517-519.
                                      t
Williams, J.D.H., J.K. Syers, R.F. Harris, and D.E. Armstrong.  1971a.
   Fractionation of  Inorganic Phosphate in Calcareous Lake Sediments.
   Soil Sci. Soc. Amer. Proc. 35: 250-255.
Williams, J.D.H., J.K. Syers, D.E. Armstrong, and R.F. Harris.  1971b.
   Characterization  of  Inorganic Phosphate in Noncalcareous Lake
   Sediments.  Soil  Sci. Soc. Amer. Proc1. 35: 556-561.
                                 50

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 Williams, J.D.H., O.K. Syers, S.S.  Shukla, R.F.  Harris,  and  D.E.
   Armstrong.  1971c.  Levels of Inorganic and Total  Phosphorus
   in Lake Sediments as Related to Other Sediment Parameters.
   Environ. Sci.  Techno!. 5: 1113-1120.
Williams, J.D.H., and T. Mayer.  1972.  Effects of Sediment
   Diagenesis and Regeneration of Phosphorus with Special  References
   to Lakes Erie and Ontario.  In:  Nutrients in Natural  Waters,
   Herbert E. Allen and James P. Kramer (Ed.).  New York:Wiley-Inter-
   science, pp. 281-316.
                                 51

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                                  TECHNICAL REPORT DATA
                          (I'lcasc read luztfuctiom; on the reverse before completing)
 ntPOHT NO.
                            2.
                                                          3. RECIPIENT'S ACCESSION-NO.
 TITLE AND SUB [ ITLE
 Phosphorus Uptake and Release by Lake Ontario Sediments
                                                          5. REPORT DATE
                                                         6. PERFORMING ORGANIZATION CODE
 AUTHOR(S)
         R.T. Bannerman, D.E.  Armstrong,
         R.F. Harris, G.C. Holdren
                                                         8. PERFORMING ORGANIZATION REPORT NO.
 PERFORMING ORG "vNIZATION NAME AND ADDRESS
  Water Chemistry Program and Soils Department
  University of Wisconsin
  Madison, Wisconsin    53706
                                                          10. PROGRAM ELEMENT NO.
            11. CONTRACT/GRANT NO.

               R-800609
2. SPONSORING AGENCY NAME AND ADDRESS
  Environmental Protection Agency
                                                          13. TYPE OF REPORT AND PERIOD COVERED
                                                             Final Report	
            14. SPONSORING AGENCY CODE
16. SUPPLEMENTARY NOTES
6. ABSTRACT
    Sediment cores were  obtained from 15 lake stations  representing the three major
 basins and the Inshore  Zone of Lake Ontario.  Cores  were sectioned for characteri-
 zation of the surface sediments according to inorganic P chemical mobility.  Physical
 mobility was characterized  by measurement of P  release from intact cores incubated
 under controlled laboratory conditions.  The proportions of potentially chemically
 mobile inorganic P were usually high (30 to 60%)  in  the central basin sediments
 and low (2 to 8%) for the inshore zone sediments.  Although the amounts of
 inorganic P desorbed after  three successive equilibrations (in .1M NaCl) of Lake
 Ontario sediments represented only 3 to 17% of  the potentially mobile inorganic P,
 sufficient inorganic P  was  desorbed to restore  a  large part of the original inter-
 stitial inorganic P concentrations.  Interstitial inorganic P (mobile P) concentra-
 tions ranged from 14 to 1280 ug/1 and were higher than dissolved inorganic P
 concentrations in the overlying water.  Diffusion rates estimated from the range of
 observed interstitial inorganic P values ranged from about 0.05 to 0.6 mg m~2 day"1
 and were in agreement with the range of 0.03 to 0.8  mg m~2 day"1 estimated from P
 release from intact cores incubated under controlled laboratory conditions.  Based
 on an inorganic P flux  of 0.2 mg m~2 day"1, the estimated annual contribution of
 inorganic P to Lake Ontario water is equal to about  10% of the external P loading.
                               KEY WORDS AND DOCUMENT ANALYSIS
                 DESCRIPTORS
 Eutrophication, Phosphorus,  Sediment,
 Sediment-Water Interface,  Interstitial
 Phosphorus.
                                             b.lDENTIFIEBS/OPEN ENDED TERMS
Lake Ontario
                          c.  COS AT I Field/Group
1R. DISTRIBUTION STATEMENT
                                             19. SECURITY CLASS (This Report)
                          21. NO. OF PAGES
                               60
                                             2O. SECURITY CLASS (This page)
                                                                       22. PRICE
EPA Form 2220-1 (9-73)

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