837
NOTES
FENCHEL, T. M., AND R. J. RIEDL. 1970.
The
sulphide system : a new biotic community
underneath the oxidised layer of marine sand
bottoms.
Mar. Biol. 7: 255-268.
FRIEDMAN, S. M.
1962.
Measurement
of sodium and potassium
by glass electrodes.
Methods B&hem.
Anal. 10: 71-106.
HILLS, G. J., AND D. J. IVES. 1961. The hydrogen electrode,
p. 71-126.
In D. J. Ives
and G. J. Janz [eds.], Reference electrodes.
Academic.
KRAMER, J, R. 1961. Chemistry of Lake Erie.
Proc. Conf., 4th, Great Lakes Res. Mich.
Univ. Great Lakes Res. Div. Publ. 47, p.
27-56.
KRU~LIBEIN,W. C., AND R. M. GARRELS. 1952.
Qrigin
and classification
of chemical
sediments in terms of pH and oxidation-reduction potentials.
J. Geol. 60: l-33.
LING, G. N. 1967. Anion-specific
and cationspecific
properties
of the collodion-coated
glass electrode and a modification,
p. 284292. In G. Eisenman [ed.], Glass electrodes
for hydrogen and other cations. M. Dekker.
MANHEIM, F. T. 1961. In situ measurements
OXIDATION-REDUCTION
of pH and Eh in natural waters and sediments.
Stockholm Co&rib.
Geol. 8: 27-36.
POMMER, A. M. 1967. Glass electrodes for soil
waters and soil suspensions, p. 362-411.
In
G. Eisenman [ed.], Glass electrodes for hydrogen and other cations. M. Dekker.
PORTNOY,H. D. 1967. The construction of glass
In G. Eisenman
electrodes,
p. 241-267.
[ea.],
Glass electrodes
for hydrogen
and
other cations. M. Dekker.
RISE~~AN, J. H., J. W. Ross, AND R. A. WALL.
1966. Glass electrode and method of makU.S. Pat. 3,282,817.
See
ing the same.
Chem. Abstr. 70: 54272.
SKOPINTSEV, B. A., N. N. RONENSKAYA, AND
E. V. SMIRNOV. 1967. New determinations
of the oxidation-reduction
potential in BlackSea water.
Oceanology 6 : 653-659.
THEEDE, H., A. PONAT, K. HIROKI, ASD C.
SCHLIEPER. 1969. Studies on the resistance
of marine bottom
invertebrates
to oxygen
deficiency
and hydrogen sulfide.
Mar. Biol.
2 : 325-337.
WHITFIELD, M . 1969.
Eh as an operational
parameter
in estuarine
studies.
Limnol.
Oceanogr. 14 : 547-558.
DETERMINATIONS
ABSTRACT
An uncomplicated
technique
for determining oxidation-reduction
potentials
of the
mud-water
interface
region in aquatic systems is presented.
Laboratory
and field observations of the oxidation
and reduction
of
hypolimnetic
water and lake sediment
are
reported.
Oxidation-reduction
(redox) potentials,2
while not amenable to strict thermodynamic interpretation,
are nonetheless valuable indicators of environmental boundary
conditions
(Stumm
1966; Morris
and
Stumm 1967). Attempts have been made
to relate redox potentials to productivity
and release of nutrients in lakes and in
soils (e.g., Hutchinson et al. 1939; Hayes
et al. 1958; Burrows and Cordon 1936;
Darnell and Eisenmenger 1936; Pearsall
1 This work was supported
by the Office of
Water Resources Research, as authorized
under
the Water Resources Research Act of 1964.
2 The term ‘<oxidation-reduction
potential”
has
been retained in this work to conform with the
classic terminology.
AT THE MUD-WATER
INTERFACES
and Mortimer
1939). Redox potentials
and pH have been used to describe the
habitats
of various bacteria
( Gillespie
1920; ZoBell 1946; Baas Becking et al.
1960)) and a relationship between reducing conditions and diagenetic alteration of
the sediments has also been stressed (Mason 1949; Berner 1969). The importance
of oxidation-reduction
potentials as an environmental parameter is well established
in the literature, but the methods used are
unnecessarily tedious and time-consuming
for work with lacustrine sediments.
MATERIALS AND METHODS
Intact samples of the mud-water interface and the overlying waters were obtained by means of a free-fall corer with
a transparent plastic insert.
Uniformly
spaced holes were drilled into the insert
and filled with silicon rubber to form
septa. A one-way flow valve mounted
above the insert in the corer developed a
negative hydrostatic pressure as the corer
was raised from the lake bottom, preventing loss of the sample (Fig. 1). The plastic
838
NOTES
zoo-
H20
11170
/IId
Y! B
CD
___-----___
\\\
@
q
op
0
OEh
(mV)
-100 -
lo
.o
I0
10170
K2C r2°7
90
A
800 I
L
NATURAL
LAKE
0
SYSTEM
-*ooI
0
FIG. 2.
- ----,
0
II o
I
II
I
I t
I
I I /---’ /
I I
0
-300 -
I
I
20
IO
CM ABOVE MUD-WATER
Summer and autumn
interface region.
--
I
-10
INTERFACE
redox profiles
of
inserts were sealed with rubber stoppers
for transport to the laboratory and could
then be used as experimental microcosms
for the study of mud-water
interface
phenomena.
Redox potentials (Eh) were determined
with a Ag/AgCl reference electrode and a
bright platinum “inert” electrode (platinum wire, Ladd Res. Ind., Inc., Burlington, Vt. ) in circuit with a potentiometric
eleclaboratory recorder. The Ag/AgCl
trode was prepared by electroplating
a
length of silver wire (0.354-mm diam) in
a NaCl solution. This electrode was inserted directly
into the water column
through a silicon rubber septum of the
plastic tube with minimal
disturbance.
The platinum electrode ( 0.177-mm diam )
was inserted through a glass capillary tube
into the system through one of the septa;
the low tensile strength of the bright
platinum made the glass insertion-guide
necessary. This electrode couple was standardized by the methods of Effenberger
( 1967). Figure 2 illustrates the rapid response of the electrode couple. Electrode
drift was negligible
in the standardization solutions and very slight in natural
systems.
RESULTS
60
30
SECONDS
Electrode-couple
---_____
-2oo-
FIG. 3.
mud-water
SATURATED
SOLUTION
-----
7/70
-400
lOOOr,
MUD
:’
IOO-
C
FIG. 1. Diagram of the coring system. A. Silicon septum in the plastic insert.
B. One-way
flow valve. C. Upper stop of plastic insert. D.
Case-hardened
stainless steel core head.
,
oooooooooooooooooo
response
90
time.
Cores were collected from a nearby
thermally stratified fishpond. Redox profiles across the mud-water
interface and
through the overlying hypolimnetic waters
839
NOTES
sot-
zoo-
100 Eh
(mV)
o-
-zoo0
5’
IO
I
FIG. 4.
I
15
,
20
Oxidation
,
30
,
25
MINUTES
process
of
35
,
40
1
45
hypolimnetic
water.
were made for the summer and autumn
months (Fig. 3). Freshly collected cores
were oxidized by bubbling air through a
cannula; redox potential of the water was
monitored during the oxidation process
( Fig. 4). Cores were then sealed and
placed in the dark. Self-reduction
over
time occurred as shown in Fig. 5; we are
sure that this is not just a simple equilibration process. This system was found
ideal for studying the mechanisms of reduction and nutrient mobilization
at the
mud-water interface.
DISCUSSION
The potentials measured by this electrode couple in natural systems are mixed
potentials and cannot be considered as
conceptually
defined oxidation-reduction
potentials. These measurements are thermodynamically
useless in the complex
nonequilibrium
systems found in nature.
However, electrode potentials are useful in
monitoring the progress of specific aquatic
systems toward an oxidized or reduced
state; as such, electrode potential measurements can be used to indicate the responses of these systems to experimental
treatments.
(Caution must be exercised
in the use of electrode potential in comparing natural systems. )
Unfortunately,
attempts to treat electrode potentials as redox potentials have
led to much confusion in the literature.
Previous workers were also hampered by
methods not readily suited to experimental
manipulation.
Unlike these methods, the
sealed system described here could be
used for observation and experimentation
without disturbing the mud-water
interface sample and without oxygen contamination. The lateral insertion of fine platinum wire into the sediments eliminates
many of the problems inherent in the
cumbersome electrodes used by Mortimer
(1941, 1942) and Hayes et al. (1958) (see
Gorham 1958). The use of a Ag/AgCl
reference electrode directly inserted into
the system avoids the agar-salt bridge
necessary with the calomel (Hg/HgCl)
reference electrodes used by others.
The rapid equilibration
and high degree
of reliability
of the Pt-Ag/AgCl
redox
electrode couple and the essentially sealed
experimental system described here represent a marked improvement over previous
methods for the investigation of sedimentwater interface phenomena.
J. E. SCHINDLER
Department of Zoology,
University of Georgia,
Athens 30601.
Eh
(mv)
-10
0
c
I31”L”xxYxxxxxxxxxxxxxxxxxxxx
4 DAYS
K. R. HONICK
Sciences,
bx I
Division of Natural
New College,
Sarasota, Florida
33578.
4
REFERENCES
-sod
1
60
FIG. 5.
interface
I
50
L
1
40
30
CM ABOVE MUD-WATER
Self-reduction
system.
1
I
20
IO
INTERFACE
process
I
I
0
-10
of mud-water
BAAS BECKING, L. G. M., I. R. KAPLAN, AND D.
MOORE. 1960. Limits of the natural environment in terms of pH and oxidation-reJ. Geol. 68: 243-284.
duction potential.
840
NOTES
BERNER, R. A.
1969.
Migration
of iron and
sulfur
within
anaerobic
sediments
during
early diagenesis.
Amer. J. Sci. 267: 19-42.
BURROWS, W., AND T. C. CORDON. 1936. The
influence
of the decomposition
of organic
matter on the oxidation-reduction
potential
in soils. Soil Sci. 42: l-10.
DARNELL, M. C., AND W. S. EISENXENGER.
1936. Oxidation-reduction
potentials
of soil
suspension in relation to acidity and nitrification.
J. Agr. Res. 53: 73-80.
EFFENBERGER,M. 1967. A simple flow cell for
the continuous
determination
of oxidationreduction
potential,
p. 123-126.
In H. L.
Golterman
[ed.], Chemical
environment
in
the aquatic habitat.
North-Holland.
GILLESPIE, L. J. 1920. Reduction potentials of
bacterial
cultures
and water-logged
soils.
Soil Sci. 9: 199-216.
GORHAM, E. 1958. Observations
on the formation and breakdown
of the oxidized microzone at the mud surface in lakes.
Limnol.
Oceanogr. 3: 291-298.
HAYES, F. R., B. L. REID, AND M. L. CANERON.
1958.
Lake water and sediment.
2. Limnol. Oceanogr. 3: 308-317.
HUTCHINSON, G. E., E. S. DEEVEY, AND A.
WOLLACK. 1939. The oxidation-reduction
potentials of lake waters and their ecological
significance.
Proc. Nat. Acad. Sci. U.S. 25:
87-90.
MASON, B. 1949. Oxidation
and reduction
in
geochemistry.
J. Geol. 57: 62-72.
MORRIS, J. C., AND W. STUMAL
1967.
Redox
equilibria
and measurements
of potentials in
the aquatic
environment.
Advan.
Chem.
Ser. 67: 270-285.
MORTIMER, C. H. 1941. The exchange of dissolved substances between mud and water
in lakes. 1 and 2. J. Ecol. 29: 280-329.
-.
1942. The exchange of dissolved substances between mud and water in lakes. 3
and 4. J. Ecol. 30: 147-201.
PEARSALL, W. H., AND C. H. MORTIAIER. 1939.
Oxidation-reduction
potentials in water-logged
soils, natural waters and muds. J. Ecol. 27:
483501.
STUMM, W. 1966. Redox potential as an environmental
parameter:
conceptual
significance and operational
limitation.
Proc. Int.
Water Pollut. Res. Conf., 3rd, Munich
1:
283-308.
ZOBELL, C. E. 1946. Studies on the redox potential
of marine
sediments.
Bull. Amer.
Ass. Petrol. Geol. 30: 477-513.
ANNOUNCEMENT
AMERICAN
SOCIETY
OF LIMNOLOGY
The 35th Annual Meeting of the Society
will be hosted by the Florida State University, Tallahassee, from 19-22 March 1972.
There is no special theme for the meeting
and papers on all aspects of the aquatic
environment will be accepted. However,
papers are desired that can add quantitative
information on the impact of man’s activities
on the aquatic environment.
Deadline for submission of abstracts is
15 November 1971. The program is being
AND
OCEANOGRAPHY,
INC.
coordinated by George H. Lauff, ASLO
Program Chairman, in cooperation with
Robert Harriss, Local Program Representative. Titles and abstracts should be mailed
to Dr. Lauff, W. K. Kellogg Biological
Station, Michigan State University, Hickory
Corners 49060. For information conceming preregistration
and other activities,
write to: Dr. Robert C. Harriss, The Marine
Laboratory, Florida State University, Tallahassee 32306.