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 0.1M NaCT
(desorption). The sediment suspensions were equilibrated for 40 hours
in polycarbonate centrifuge tubes (50 ml; screw cap) on a wrist action
shaker at 25°C. 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 ym) after the initial centrifugation
step. A No-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 al] conducted in the glove bag. The distilled water
and 0.1M NaCl solutions used for sediment equilibration were stripped
with No 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 No during equilibration on the wrist action shaker.
The effects of filter size (0.45, 0.22 and 0.10 um Millipore filters),
and 0.1M 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,-free
conditions (anoxic).

n


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

(ug/1)*
Filter Inorganic P Desorbed In Following Successive
Pore Equilibrationsb
Sized
ym First Second Third
Distilled Water

Double Centrifuge 4743 162+3 222420
0.45 5543 161+5 21645
0.22 4541 98+2 15448
0.10 40+0 8245 15243

«1M NaCl Solution
Double Centrifuge 43+1 50+1 53+]
0.45 3442 42+7 46+10
0.22 3343 40+2 4043
0.10 28+0 2741 2842

44/9 = yg/1+40; error values are average deviation for triplicate
samples.

bFiltered samples centrifuged twice prior to filtration.

32


Table 8. TOTAL FILTERABLE Fe IN THE INTERSTITIAL WATER
OF SEDIMENTS FROM LAKE ONTARIO

(mg/1)
Station Interstitial Fe@ at the Following Depths Below the
Identifier Sediment Surface (cm)
0-3 3-6 6-9 9-12 12-15
Inshore Zone
34 0.5 0.4 0.4 0.4 0.3
14 3 4 16 12
30 3 7 8 3 7
41 1 1 1 1
eR> 5 6 25 46 37
60 8 1 1 7 ]
Rochester Basin
62 0.3 0.2 0.3 0.4 4
75 4 4 5 4 7
92 6 13 21 27 31
Mississauga Basin
45 3 6 9 9 14
Niagara Basin
10 1 1 2 2 2
Kingston Basin
96 1 1 12 13 15

3concentrations in the lake bottom water were less than 0.3 mg/1.

PGenesee River.

28


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 NaC1 SOLUTION UNDER OXIC OR ANOXIC CONDITIONS

(ug/g)*
Station Oxic Equilibrations
Identifier First Second Anoxic Equilibration

Inshore Zone

60 0.3 0.5 0.9
eR> 1.2 1.8 1.4
14 1.2 0.8 1.3
41 1.7 2.2 3.6

Rochester Basin

92 2.4 3.6 56.2
75 0.7 1.7 3.5

Mississauga Basin
45 0.9 0.6 32.1

3ug/1 = 40 x g/g.

>genesee River.

37


contact with sediments are able to utilize the dissolved inorganic P
and the potentially mobile sediment inorganic P fraction (NaQH-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 wil] 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 et al. 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 et al. (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

5


law of diffusion, and a diffusion coefficient of 10-6 cm? secé!

(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 m-2 day”). This is in
agreement with the range of 0.03 to 0.8 mg me day”! 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 me 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 106 kg of P per year. This compares to an
estimated annual loading from external sources of 1.3 x 107 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 (NaQH-P) in the upper 3 cm of sediment.

47


Dissolved Inorganic P in pg/I

250 T T T T T 7

200} ~— Station 30

150

T
.
N

100+ ~~

100 Station 60

r 4

took Station 10 Air

Incubation Time in Days
Figure 4. Levels of Dissvive inorganic P Released from Intact

Cores Gbtained octoter 9, 1973; for Cores Designated
Air, ‘is, the N2 was iy troduced after 25 Nays.

4s


Williams, J.D.H., J.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. Technol. 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


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 yg/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 No
were inconsistent. P release from the station 10 core aerated with
air was greater than for the duplicate core treated with No after

35 days (Figure 4). Release from the air-treated core from station 60
was lower prior to the introduction of No into the duplicate core at
35 days. However, P release appeared to be related to No 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/l have been measured during the summer (Dobsin
1967).

The highest levels of P obtained in the overlying Jake water ranged
from 5 to 250 yg/1 (Figures 3 and 4). However, only cores from
stations 34 and 10 (Figure 3) had maximum values below 10 wg/1, and
most cores gave maximum values between 30 and 90 wg/1. The levels of
P released reached 10 ug/l or higher between 12 and 25 days of
incubation for most cores, and surpassed the mean concentration of
about 11 49/1 for "soluble phosphate" in Lake Ontario bottom waters
(Shiomi and Chawla 1970).

43


SL

Niagara Basin

10 21 JUN 72 1444+65 1229+85 214+20

10 6 NOV 72 1448 1108 =1335 «61182 +1218 935 1132 895 230 173 202 = 287
Kingston Basin

96 21 JUN 72 857+24 810+2 47+27

sediment 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.


water system and that an appreciable amount of the dispersed sediment
was less than 0.10 um diameter material. The 0.1M 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 0.1M NaCl than in distilled water.

The amounts of inorganic P in solution after the first equilibration
ranged from 0.6 to 35.8 ug/g for the various Lake Ontario sediments
investigated (Table 13). This corresponds to a concentration range
of 24 to 1432 ug/l. 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


Abstract
List of Figures
List of Tables

Acknowledgements

Sections

I Conclusions

Il Recommendations

III Introduction

WV Methods and Materials
V Results and Discussion

VI References

CONTENTS

N FF wW

13
48


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 al. (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 Feet 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
sediment:water 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

storage of sediments, apparently due to partial oxidation of Fe2+ and
sorption of dissolved inorganic P. Consequently, desorption-sorption

26


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 No while
helping to maintain the desired atmosphere in the water above the

core by limiting exchange with the atmosphere. For some columns, air
or N2 was introduced beneath the surface of the overlying water column
through 6 mm pyrex tubing. The No was prepurified and was passed
through pyrogaltol 15% (w/w) in KOH (20% w/w) prior to passage into
the water column to remove traces of 09. Both the No 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 No.
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 No treatment, air, and no treatment, respectively. Cores
from stations 34, 45 and 75 of the same sampling trip were not treated
with air or No. 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


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 NaQH-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 NaQH-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 ottained from inorganic P fractionation (Table 2) indicate
that the proportion of potentially chemically mobile inorganic P
(NaGH-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 glaciclacustrine clays. The NaOH-P fraction

is thougnt to include

16


vl

Table 1. TOTAL P, TOTAL INORGANIC P, AND Mad bes laa P AT VARIOUS SEDIMENT DEPTHS IN LAKE ONTARIO CORES?
ug/g

Station Sampling Total P Total Inorganic P Total Organic P
Identifier Date 0-5 5-10 10-15 15-20 0-5 5-10 10-15 15-20 0-5 5-10 10-15 15-20

Inshore Zone

52 21 JUN 72 911+111 891+108 20+3
34 6 NOV 72 955 890 900 1010 940 890 900 885 15 0 0 125
30 888 685 610 612 790 675 600 550 98 10 10 62
60 548 500 500 567 548 500 500 522 22 0 0 45
14 9 0CT 73 737 675 62
4) 755 713 42
GR? 825 712 113
Rochester Basin
83 21 JUN 72 1078 867 211
92 1195 1000 195
75 1001+22 871430 130+53
92 6 NOV 72 1270 966 1140 860 130 100
62 950 980 810 945 140 35
75 1163 1103 1050 1020 113 83
Mississauga Basin
32 21 JUN 72 7272 995 278
45 1461 1176 286

45 6 NOV 72 1356 1028 1095 883 261 195


Table 7.

INTERSTITIAL INORGANIC P IN SUCCESSIVE ALIQUOTS
SQUEEZED FROM LAKE ONTARIO SEDIMENTS

(yg/1)

Interstitial Inorganic P at Following Depths Below

Aliquots the Sediment Surface (cm)

mi 0-3 3-6 6-9 9-12 12-15
Station 75

0-3 810 130 112 201 368

3-6 1180 706 619 781 978

6-9 1070 1040 899 997 1190

9-12 1080 1022 1010 1080

12-15 1120 981 1048 885 847
Station 45

6-9 537 1260

9-12 557 1300

12-15 542 1180
Station 60

0-3 33

3-6 94

6-9 83

27


interstation 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 et al. (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 et al. 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 No
before closing, and storage of unsqueezed samples in a No 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 um 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 No. 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 10, 30
and 60 were transported to the laboratory for measurement of P
release under controlled conditicns.


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 Tow (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 (NaQH-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
ug/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
ug/l. The levels of P released reached 10 wg/1 or higher between 12
and 25 days of incubation for most cores and surpassed the mean
concentration of about 1] 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 mainly by diffusion cf IIP from the
sediments to overlying water. Diffusion rates estimated from the
range of observed IIP values (100 to 1000 ug/l) ranged from about

1


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 yig/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 Jower 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 cma 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 4, SEDIMENT EXCHANGEABLE INORGANIC P IN THE 0 to 5 CM SEDIMENT
LAYER OF LAKE ONTARIO CORES OBTAINED NOVEMBER 6, 1972

Station S'p sotn sed Exch 3p, Total Exch Py
Identifier ug/g ug/g % ug/g %
Inshore Zone
34 2.4 13 1 16 2
30 0.5 9 1 10 1
60 1.0 20 4 21 4
Rochester Basin
62 4.1 29 4 33 4
92 1.5 167 15 169 15
75 1.2 193 18 195 18
Mississauga Basin
45 0.9 140 13 140 13
3ab 2.5 153 15 156 15
Niagara Basin
10 1.2 194 16 195 16

3Sed exch Py is expressed as percent of inorganic P in sediment phase;
total exch Py is expressed as a percent of inorganic P in the sediment

and water phases.

bsampled June 21, 1972.

ral


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
YW 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. 36


FIGURES

Sampling Sites (IFYGL Station
Identifiers) for Lake Ontario Sediments

Inorganic P Sorption Curves for Lake Ontario
Inshore and Basin Sediments

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

Levels of Dissolved Inorganic P Released from
Intact Cores Obtained October 9, 1973; for Cores
Designated Air; Nos the Ny was Introduced after
35 days.

iv

Page

4

44

45


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 110°C 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 et al. 1954; Sommers et 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 (NaQH-P, CDB-P and HC1-P) in the sediments
were determined by inorganic P fractionation based on the procedures
described by Williams et al. (1971 a). The reagent sequence was 0.1N
NaOH.1M NaCl, 17 hours (NaQH-P), citrate-dithionate-bicarbonate,

85°C 15 min (CDB-P), and IN HCT 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 et al. 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 NaQH-P was increased by the
correction procedure. Inorganic P was measured in neutralized NaOH
and HC] extracts by the method of Murphy and Riley (1962) and in

CDB extracts by the method of Watanabe and Olsen (1962).

10


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.

vit


9L

Table 2. FORMS OF INORGANIC P IN LAKE ONTARIO SEDIMENTS

Phosphorus forms at various depths below sediment surface@

Station Sampling 0-5 cm 5-10 cm 10-15 cm 15-20 cm
Identifier Date NaOH CDB HCI NaOH CDB HCl NaOH CDB- HCI NaOH CDB- HCI
Inshore Zone
34 21 JUN 72 2 6 91
$2 4+] 5+] 9042
30 6 NOV 72 28 16 53 10 5 72 8 6 82 6 7 88
60 8 6 81 4 1 95 2 4 91 2 4 95
34 3 6 85 2 6 86 2 5 97 88
14 9 OCT 73 4 4 74
41 5 5 74
gro 14 («1446
Rochester Basin
83 21 JUN 72 300=«17 48
92 33° «14 4]
75 46+5 6+] 42+]
62 6 NOV 72 22, «18 57 15 18 65
92 37.15 36 30. «15 50
75 40 17 29 50 11 32


EPA-660/3-75-006
FEBRUARY 1975

Ecological Research Series



Table 15. SORPTION OF ADDED INORGANIC P BY LAKE ONTARIO SEDIMENTS
OBTAINED JUNE 21, 1972

Added P Sorbed (%) For Added P

Station Core Level (ug of P per g)® of
Identifier Section, 2.5 25 250 2500
cm

Inshore Zone

34 0-5 80 80 48 20
5-10 3 72 4] 25

52 0-5 73 60 24 7
5-10 93 78 50 37

10-15 95 85 57 31

Rochester Basin

92 0-5 10098 82 52
75> 0-5 100 88 82 52
75 5-10 100 93 79 48

Mississauga Basin

32 0-5 100 100 87 57
5-10 100 100 48 46
10-15 100 $5 89 52

Aug/liter = g/g x 40.

OSediment in 3% sediment suspension

39


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.


0.05 to 0.6 mg m2 day"! and were in agreement with the range of 0.03
to 0.8 mg me day! estimated from the cores incubated in the
laboratory. Based on the inorganic P flux of 0.2 mg m2 day! (mean
for incubated cores), the estimated annual contribution of inorganic P
to the lake water from the sediments is 1.4 x 106 kg of P per year.
The estimated sediment contribution is about 10% of the external P
loading (1.3 x 107 kg/yr).


TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)

1 REPORT NO. 2. 3. RECIPIENT'S ACCESSION-NO.

TITLE ANDSUBTITLE - 5. REPORT DATE
Phosphorus Uptake and Release by Lake Ontario Sediment

6. PERFORMING ORGANIZATION CODE

7 AUTHOR(S) I. PERFORMING ORGANIZATION REPORT NO.
R.T. Bannerman, D.E. Armstrong,

R.F. Harris, G.C. Holdren

9. PERFORMING ORG \NIZATION NAME AND ADDRESS 70. PROGRAM ELEMENT NO,
Water Chemistry Program and Soils Department
University of Wisconsin

TT, CONTRACT/GRANT NO.
Madison, Wisconsin 53706

R-800609
12. SPONSORING AGENCY NAME AND ADDRESS 13. TYPE OF REPORT AND PERIOD COVERED
. . Final Report
Environmental Protection Agency 14, SPONSORING AGENCY CODE

16, SUPPLEMENTARY NOTES

16. 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/l 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 m2 day71
and were in agreement with the range of 0.03 to 0.8 mg m2 day-1 estimated from P
release from intact cores incubated under_controlled laboratory conditions. Based
on an inorganic P flux of 0.2 mg m2 day ~, 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 lb. IDENTIFIERS/OPEN ENDED TERMS |c. COSATI Field/Group
Eutrophication, Phosphorus, Sediment, Lake Ontario
Sediment-Water Interface, Interstitial
Phosphorus.
13. DISTRIBUTION STATEMENT 19. SECURITY CLASS (This Report) 21.NO. OF PAGES
60
20. SECURITY CLASS (This page) 22. PRICE

EPA Form 2220-1 (9-73)

MENT PRINTING OFFICE: 1975-623- 03199 REGION 19



Table 13. DESORPTION OF INORGANIC P FROM LAKE ONTARIO SEDIMENT AFTER
SUCCESSIVE EQUILIBRATIONS IN A 0.1 M NaC] SOLUTION?

(ug/g)

Inorganic P Desorbed In Successive Equilibration Steps

Station 0-5 cm layer 5-10 cm layer
Identifier Ist 2nd 3rd Ist 2nd 3rd

Inshore Zone

60 1.5 1.8 0.9 1.2 1.4 1.1
30 4.0 1.8 1.2 2.2 2.8 2.7
grb 7.7. 2.8 5.0 1.4 3.1 3.5
14 2.3. 1.9 2.4 1.8 3.1 4.1
41 4.0 4.5 3.6 1.4 1.8 1.4
34 0.6 0.8 0.8 0.2 0.2 0.2
Rochester Basin
92 35.8 15.8 13.6 6.1 7.3 5.8
Mississauga Basin
45 20.1 10.4 11.0 13.3 11.3 1.3
Kingston Basin
96 12.3 6.8 5.1 2.0 3.2 3.4

Aug/1 = 40 x pg/9.

PGenesee River.

35


Table 5.

INTERSTITIAL INORGANIC P IN LAKE ONTARIO SEDIMENTS
(ug/1)

Interstitial Inorganic P at Following Depths

Station below the sediment surface (cm)a
Identifier Lakewater 0-3 3-6 6-9 9-12 12-15
Inshore Zone
34 15 19 14 14 14 28
14 3 249 592 252 67 22*
30 15 498 569 392 37* 116*
4] 18 92 115 50* 33* 111+
GRb 4 158 47* 311 663 182
60 8 83 58 69 133* 39*
Rochester Basin
62 20 1050 1010 954 382 444
75 19 1070 1040 899 997 1190
92 16 145 55 87 107 46
Mississauga Basin
45 25 1260 537 693 422 749
10 20 140 446 684 90 99
96 19 1280 1040 1160 €37 537

3For values indicated by *, the time required to separate the
interstitial waters was greater than one-half hour.

OGenes ee River.


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

Station Added P Sorption (%) For Added P Level (yig/g)@ OF
Identifier 6.25 12.5 25 50 100

Inshore Zone

34 71 70 65 59
30 100 98 99 99
60 9] 89 75 62

Rochester Basin

92 100 98 98 98
62 66 66 53 46
75 93 98 98 98

Niagara Basin
45 98 99 99 99

8ug/1 = 40 x ng/g.

40


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 fractionation, this
fraction (also termed "reductant soluble P") is attributed to P occluded
in Fe oxides. However, in lake sediments, the NaQH-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 NaQH-P represents a more
mobile inorganic P fraction than CDB-P in the sequential extraction
scheme.

Large amounts of inorganic P were present as HCI-P. This fraction
accounted for about 90% of the inorganic P in the glaciolacustrine
clays (stations 34 and 52). The HCI-P fraction contains mainly apatite
(Williams and Mayer 1972; Syers et al. 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 (NaQH-P, CDB-P, HC1-P) were frequently less

than the total inorganic P content of the sediment (Tables J 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 et al. 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


No.

14

15

16

7

TABLES

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.

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

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

Desorption of Added Inorganic P by Sediments

in the 0 to 5 cm Section of Lake Ontario
Cores Obtained November 6, 1972.

vi

37

39

40

42


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 ug/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
smal] 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 ug/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 smal] amounts of NaQH-P and CDB-P and a
high proportion of HC1-P (Table 2). In contrast, basin sediments
contained comparable proportions of NaOQH-P and HC1-P and smaller
amounts of CDB-P. Similar trends were found for basin sediment samples

13


Shiomi, M.T., and V.K. Chawla. 1970. Nutrients in Lake Ontario.
Proc. 13th Conf. Great Lakes Res. Internat. Assoc. Great Lakes
Res., pp. 715-732.

Sommers, L.E., R.F. Harris, J.D.H. Williams, D.E. Armstrong, and
d.K. Syers. 1972. Fractionation of Organic Phosphorus in Lake
Sediments. Soil Sci. Soc. Amer. Proc. 36: 51-54,

Stumm, W., and J.0. Leckie. 1971. Phosphate Exchange with Sediments;
Its Role in the Productivity of Surface Waters. Proc. 5th Int.
Water Pollution Res. Conf., (in press).

Syers, J.K., R.F. Harris, and D.E. Armstrong. 1973. Phosphate
Chemistry in Lake Sediments. J. Environ. Qual. 2: 1-14.

Thomas, R.L., A.L.W. Kemp, and C.F.M. Lewts. 1972. Distribution,
Composition and Characteristics of the Surficial Sediments of Lake
Ontario. J. Sed. Petrology. 42: 66-84.

Watanobe, F.S., and $.R. Olsen. 1962. Colormetric Determination of
Phosphorus in Water Extracts of Soil. . Soil 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 0.1M NaCl System. Environ. Sci. Technol. 4: 517-519.

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. Proc’. 35: 556-561

50


Table 9. DESORPTION OF INORGANIC P FROM LAKE ONTARIO SEDIMENT
AFTER SUCCESSIVE EQUILIBRATIONS IN DISTILLED WATER

(ug/g )4
Station Sediment Inorganic P Desorbed in Successive Equilibration
Identifier Section, steps
cm Ist 2nd 3rd 4th 5th 6th
Inshore Zone
34 0-5 2.5
5-10 2.0 2.5 3.4 2.4 2.0 2.0
10-15 1.¢ 1.3 1.5 1.2 1.2 1.0
52 0-5 2.7 2.4
5-10 1.8 1.9 1.8 1.8 1.6 1.6
30 6-5 6.1 14.1
5-10 1.0 1.2
60 0-5 1.4 2.6
5-10 0.8 1.0
Rochester Basin
75 0-5 9.8
5-10 6.4 16.6
10-15 5.0 10.8 10.2 2.3 2.4 2.3
83 0-5 1.6 6.0
5-10 0.6 1.6 2.6 1.8 1.9 2.1
62 6-5 4.3 5.1
5-10 4.5 4.6
92 0-5 3.4 8.0
5-10 1.5 2.6
Mississauga Basin
45 0-5 23.0
5-10 2.0 3.6 5.8 6.2 6.5 6.1
Niagara Basin
10 0-5 7.6
5-10 1.8 6.6

ug/l = 40 x ug/g.

3c


Table 10. DESORPTION OF INORGANIC P FROM THE G TO 5 CM SEDIMENT SECTION
OF LAKE ONTARIO CORES AFTER SUCCESSIVE EQUILIBRATIONS IN DISTILLED WATER

(ug/g)?
Station Inorganic P Desorbed in Successive Equilibration Steps
Identifier Ist énd 3rd 4th Sth 6th

Inshore Zone

34 2.6 3.9 4.8 3.8 4.4

3a 1.3 1.2 1.4 3.1 2.6 1.8
30 0.8 2.2 4.7 4.6

60 1.2 2.2 21 2.0 1.5

Rochester Basin

75 2.0 4.9 8.8 10.0 11.6 9.1
75° 1.5 2.5 2.7 3.8 3.8 4.4
92 1.3 3.2 3.8 5.2 4.2

62 4.5 5.1 4.4 4.4

Mississauga Basin
45 1.8 4.5 7.1 9.6

Niagara Basin
10 1.6 4.9 7.3 9.6

a
ug/l = 40 x ug/g.

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

31


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 m2 day”! for stations 34 and 45 to 0.8 mg m2 day"! for
station 30. The average rate for the 7 cores investigated was about

0.2 mg me? day"!

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 al. 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 ug/} in the overlying water (Shiomi and Chawla 1970), Fick's first

46


Table 3. SEDIMENT WATER CONTENT OF LAKE ONTARIO CORES

(%)

Water Content at Following Depths
Station Sampling Below the Sediment Surface

Identifier Date 0-5 cm 5-70 cm TO-T5 cm

Inshore Zone

52 21 JUN 72 37+8
34 6 NOV 72 57+] 56+2 58
30 5242 30+1 28
66 26 21 19
arb 9 OCT 73 35 23
30 42 26
4) 26 24
14 27 31
Rochester Basin
92 6 NOV 72 60+3 54+0
62 5146 4241
83 68 63
75 76+2 76+) €7
92 9 OCT 72 65 65
Mississauga Basin
32 21 JUN 72 73+1 Té 73
45 € NOV 72 75+1 71+]
45 9 OCT 73 &G 7é
Rochester Basin
10 6 NOV 72 7542 7041 65
Kingston Basin
96 9 OCT 73 75 €3

a water = weight of water diviced by weight cf water + sediment.
Deviations shown are for two cr more cores at tre same station.

b .
Genesee River.


Kemp, A.L.W., C.B.J. 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. Technol. 7: 454-456.

Mehta, N.C., J.0. 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 cf Plant Nutrients in
Lake Mendota. In: Limnology of North America. D.G. Frey (Ed.).
University of Wisconsin Press, Madison, pp. 75-§7.

Sagher, A. 1974. Microbial Availability of Phosphorus in Lake
Sediments. M.S. Thesis, Department of Soil Science, University
of Wisconsin, Madison.


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 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 m2 day”!
and were in agreement with the range of 0.03 to 0.8 mg me day”! estimated
from P release from intact cores incubated under controlled laboratory
conditions. Based on an inorganic P flux of 0.2 mg m2 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.

ii


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 curing a subsequent
desorption step (Table 17). Consequently, the net sorption 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


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 smal]
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 Fee* to Fe@* and resulting desorption of
inorganic P. Whether these sediments became sufficiently reduced to
promote complete reduction of Feet 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


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


SECTION VI
REFERENCES

Bannerman, R.T. 1972. Interstitial Inorganic P in Lake Wingra
Sediments. M.S. Thesis, University of Wisconsin, Madison.

Bray, J.T., 0.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
Mendota, 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 Chlorophyl] Degradation Products in the Sediments of Lake Erie
and Ontario. Proc. 11th 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 and Huron. J. Sed. Petrology.
41: 537-548.

Kemp, A.L.W., anc A. Murdrochova. 1°71. Electrodialysis: A
Method for Extracting Available Nutrients im Great Lakes Sediments.
Proc. 14th Conf. Great Lakes Res., Internat. Assoc. Great Lakes
Res., pp. 241-251.


Kingston
96- Basin

Duck-Gallo Sill

inshore -" =—“h
034 a 83
a--7 aT 920 !
~ Mississouga 45, ef Rochester
woe - 4:232 Basin cay 2 75 .
-° % Basin ~?"
= Niagara Basin weer”

---
-

\ 0 “Scotch Bonnet Sill
Whitby- Olcott

Niagara R. Sill Genesee R.

Figure 1. Sampling Sites (IFYGL Station Identifiers) for Lake Ontario Sediments.


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

G.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 Ile Laboratory
National Environmental Research Center
Grosse Ile, Michigan 48138

NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTIUN AGENCY

CORVALLIS, OREGON 97336


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 values for 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 0.1M 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 um
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 um
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


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+] 32+]

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
NaQH-P, CDB-P and HC1-P, respectively.

MGenesse River.


RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development,

U.S. Environmental Protection Agency, have been grouped into
five series. These five broad categories were established to
facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in
related fields. The five series are:

1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research

4. Environmental Monitoring

5. Socioeconomic Environmental Studies

This report has been assigned to the ECOLOGICAL RESEARCH STUDIES
series. This series describes research on the effects of pollution

on humans, plant and animal species, and materials. Problems are
assessed for their long- and short-term influences. Investigations
include formation, transport, and pathway studies to determine the
fate of pollutants and their effects. This work provides the technical
basis for setting standards to minimize undesirable changes in living
organisms in the aquatic, terrestrial and atmospheric environments.

EPA REVIEW NOTICE

This report has been reviewed by the Office of Research and
Development, EPA, and approved for publication. Approval does
not signify that the contents necessarily reflect the views and
policies of the Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or
recommendation for use.


Lp

Sediment AP in ug/g

+100 45 T T T T T T T T

+90

+80r

+70F

+60

+50

+40

+30

+20

+10

L n n L 1 1
200 400 600 800 1000 1200 1400 1600

Dissolved Inorganic Pin yg/I
Figure 2. Inorganic P Sorption Curves for Lake Ontario Inshore and Basin Sediments.


Table 6. EFFECT OF SEDIMENT STORAGE ON INTERSTITIAL INORGANIC

P VALUES
Storage Time, Interstitial Inorganic P,
min ug/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


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

(ug/1)?

Inorganic P Desorbed in Successive

Filter Pore Size? Equilibration Steps
um First Second
Station 30
Double Centrifuge V7 50+2
0.45 18 5343
0.22 7 44+4
0.10 19 4244
Station 34
Double Centrifuge 11742
0.45 116+4
0.22 108+0
0.10 90+1
Station 75
Double Centrifuge 3341 110+4
0.45 2841 109+6
0.22 3142 86+5
0.10 30+1 7146

4ug/g = yg/1—40; deviations are average deviations for triplicate
samples.

DF i tered samples centrifuged twice prior to filtration.

34


inorganic P in equilibrium with inorganic P in solution based on
investigations of the nature of the inorganic P in this fraction
(Williams et al. 1971 a; 1971 b; Syers et al. 1973) and relationships
between the amounts of NaOQH-P and isotopically exchangeable inorganic
P (Li et al. 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 NaQH-P than other Inshore Zone sediments (Table 2), but
did not contain appreciable exchangeable inorganic P (Table 4). The
level of NaQH-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 et al. (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
smal] 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 NaQH-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


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 al. 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 CaCO3, 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 ITIP and by using extraction procedures (Chang and Jackson 1957;
Williams et al. 1967) developed for sediments (Williams et al. 1971 a3
1971 b) which allow measurement of nonoccluded and apatite P by
sequential extraction with NaOH, citrate-dithionite-bicarbonate

(CDB), and HCT 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


Table 17. DESORPTION OF ADDED INORGANIC P BY SEDIMENTS IN THE

0 TO 5 CM SECTION OF LAKE ONTARIO CORES OBTAINED NOVEMBER 6, 1972

Add P Desorbed as %
Added P Sorbed

Net Added P Sorbed as
% Total Added P

Station For The Added Levels of (ug/g)*
Identifier 6.25 25 50 100 6.25 25 50 100
Inshore Zone
60 32 51
Rochester Basin
62 8 49
92 4 94
Mississauga Basin
45 6 2 1 2 92 98 98 97

Sug/1 = po/g x 40.

42


Dissolved inorganic P in ug/!

T T T T T T T
Station 10
Ng —e—
407 air ee 7
Control —o—
30r 4
20 4
(OF 4
Station 75 -e—
40h Station 45 -©- 4
Station 34 —o—
30r 4
20 4
Fn 4
aioe
fe) aan 4 i 7 L
(0) to 20 30 40 50 60 70

Incubation Time in Days

Figure 3. Levels of Dissolved Inorganic P Released from Intact
Cores Ubtained !loveber 6, 1972

44


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 4°c). 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 al. (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 sil] 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 No 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