THE MARINE CHEMISTRY
OF IODATE
by
GEORGE TIN FUK WONG
B.S., California State College, Los Angeles
1971
SUBMITTED IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE
DEGREE OF MASTER OF
SCIENCE
the
at
MASSACHUSETTS INSTITUTE OF
TECHNOLOGY
June, 1973
Signature
of Author.
....
th
Depart en to ofE
a
Planetary Sciences
Feb. 21, 1973
Certified by..
.0-.....e..
.--
ry
.,.
........
_----h-sis Kpervisor
Accepted by.
..........
.o...............
Chairman, Departmental Committee
on Graduate Students
ACKNOWLEDGMENTS
I wish to express my gratitude to Dr. Peter
G. Brewer whose invaluable advice, guidance and
made
encouragement
this
research
enjoyable
and
possible.
I also want to thank Dr. John M. Edmond
for his encouragement and for the instructive
discussions on this study.
I would also like to thank especially Mr.
Roy Smith for his time and effort in collecting
the samples for me during the Geosecs cruise.
The helpful comments from Dr. Nelson Frew
and from the fellow graduate students are also
very much appreciated.
-ii-
TABLE OF CONTENTS
Page
.
i
Acknowledgments...............................
ii
Approval Page....
Table
of
..
0 . .
.
.
.
.
.
.
.
.
.
Contents.........................
.
iii
.
List of Figures....
vi
List of Tables................................ viii
Abstract ...
..
..........
.........
.........
.
x
. .
1
Chapter
I.
Introduction...... . . .
.
. .
. .
. .
. .
A. Purpose of the study....................
1
B. Iodine in the sea.......................
1
C. Analytical methods for the analysis of
iodine
II.
The
in
analytical
11
seawater.....................,.
23
method........................
A. The feasibility of a direct method......
23
. . ..
24
B. Initial te t
i.
.
. .
. . . .
. .
.
The Beer's Law region for the
tri-iodide ion.....................
0
24
ii. Determination of the iodate
concentration in a standard iodate
solution using the standard
addition
method...............,....
-111-
27
iii. Experimental conditions ............
27
iv.
Theoretical interferences..........
v.
The tri-iodide ion absorption
curve.
............
.....
.
.......
29
32
C. The analyticalmethod...................
34
i.
Instrumentation....................
34
ii.
Standard solutions.................
34
iii. Procedure for the analysis of
iodate in seawater.................
iv.
The precision of the analytical
methods ........
v.
43
Correlation between the addition
method and the titration method....
vi.
38
50
Correlation between the addition
and the Matthews and Riley's
,.. .... ....
meth ds,
...
....
...
52
D. Attempts for developing an analytical
method for the determination of iodide
seawater........................
55
storage................................
58
in
III.
IV.
Sample
A. A qualitativestudy.....................
58
B. A quantitative study....................
60
The distribution of iodate in the sea.........
-iv-
63
A. Seasonal variations in the iodate
content of the Woods Hole coastal
surface
water.......
..........
.....
.
63
B. Diurnal variations in the iodate
content in seawater.....................
66
C. The distribution of iodate in the
Argentine Basin in the South Atlantic...
V
Conclusion....
VI.
Future work . . . . . ..............................
......
*
.. 0...
.......
Refe
.... enc ...s.. ...
97
.....
...
...
99
#
a 0 #
....
...
...
102
Appendix 1....................................0 a 00*0
Appendix 2.
. .
. .
. .
. .
..
.
. .
. .
70
. .
.
10 9
ll
LIST OF FIGURES
Page
Figure I-1.
Iodine profiles from the Pacific and
their station positions..................
Figure 1-2.
Variations in iodide-iodine and total
iodine in the Pacific...................
Figure 1-3.
The concentration diagram of the iodideiodate couple at a pH of 8.1 and with
a total iodine concentration of 0.4
Figure I-4.
The analytical scheme for the analysis
of iodide and iodate by co-precipitation... . . . . . . . . . . . . . . . .
Figure II-1.
The Beer's Law region of the tri-iodide
ion absorption at 353 nm. in a 10 cm.
20
26
Figure 11-2.
The tri-iodide ion absorption curve......
33
Figure 11-3.
The apparatus............................
35
Figure 11-4.
The analytical scheme for the analysis
of iodate and total iodine...............
39
Figure 11-5.
A sample plot for the photometric micro-
Figure II-6.
A sample plot for the determination of
iodate in seawater by the addition
Figure IV-1.
Seasonal variations in the iodate
content of the Woods Hole coastal
surface
Figure IV-2.
49
water..........................
Diurnal variations in the iodate content
and the corresponding changes in the
phosphate concentration of the Woods
Hole
coastal
water.................,..
-vi-
65
68
Figure IV-3.
Cruise track of R/V Knorr, Geosecs
Cruise, Leg 5, and the locations of
stations
60
and
61......................
71
The nitrate, phosphate and silicate
profiles of station 60...................
76
The oxygen, salinity and potential
temperature profiles of station 60 with
the water masses identified..............
77
The nitrate and phosphate profiles of
station 61
78
Figure IV-7.
The oxygen profile of station 61.........
79
Figure IV-8.
The salinity and potential temperature
profiles of station 61 with the water
Figure IV-4.
Figure IV-5.
Figure IV-6.
masses
identified.....................
.
79
Figure IV-9., The iodate profile of station 60.........
81
Figure IV-10. The iodate profile of station 61.........
82
Figure IV-ll. The relationship between phosphate and
iodate.
.T........
......
.
...
.....
.
Figure IV-12. The relationship between nitrate and
iodate....**.....................,.....
86
87
Figure IV-13. The relationship between AOU! and iodate.,.
88
Figure IV-14. Vertical profile through the western
basin of the Atlantic Ocean showing
idealized water-mass distribution........
91
-vii-
LIST OF TABLES
Page
Table I-l.
Some molecular properties of iodate and
iodide. ...........
Table 1-2.
......
.
.
..
* ...
5
Mean concentration of iodine in the
surface
water.............................
Table 1-3.
P/I ratio in some algae...................
Table 1-4.
Analytical methods for the analysis of
iodine
in
seawater........................
12
13
14
Results for testing the Beer's Law region
of the tri-iodide ions at 353 nm. in a
10 cm. cell.....
..
..............
.
25
Results for the determination of iodate
concentration in a standard iodate
solution..................................
28
Table 11-3.
Some possible interfering species.........
30
Table 11-4.
Results for the determination of the
precision of the addition method..........
48
Data for determining the precision of
the photometric micro-titration method....
45
Table II-1.
Table 11-2.
Table 11-5.
Table 11-6.
Table 11-7.
Correlation between the addition method
and the titration method..................
51
Correlation between the addition method
and the Matthews and Riley's method.....
53
Table III-1. The qualitative effect of storage on the
iodate content in seawater by various
storage methods .......................
Table 111-2. A quantitative study on the effect of
storage on the iodate content in seawater
by controlling the storage temperature....
-viii-
59
61
Table IV-l.
Seasonal variations in the iodate content
of the Woods Hole coastal surface water....
64
Table IV-2.
Diurnal variations in the iodate content
and the corresponding changes in the
phosphate concentration of the Woods Hole
coastal water..............................
67
Table IV-3.
Nutrient data from station 60..............
72
Table IV-4.
Nutrient data from station 61..............
74
-ix-
l
ABSTRACT
THE MARINE CHEMISTRY OF IODATE
GEORGE TIN FUK WONG
Submitted to the Department of Earth and
Planetary Sciences on March 1, 1973 in
partial fulfillment of the requirements for
the degree of Master of Science.
An analytical technique has been developed for the
analysis of iodate in seawater. In this method, iodate is
reduced to iodine by excess iodide in an acidic solution and
the iodine thus formed is reacted with excess iodide to form
the tri-iodide complex. The tri-iodide ion concentration is
determined spectrophotometrically at 353 nm. by a series of
additions of known amounts of a standard iodate solution. This
method has a coefficient of variation of 2.7%. Alternatively,
the tri-iodide ion concentration can be determined by photometric micro-titration with a standard thiosulfate solution
with a coefficient of variation of 0.7%. A comparison of the
results from these two techniques and from a standard method
shows that they agree to within experimental uncertainties.
The new method is faster than the standard method, is of
comparable precision and can be performed on board ship for
rapid routine analysis of iodate. Attempts to design a similar
method for the analysis of iodide in seawater have so far
been unsuccessful. Storage experiments show that seawater can
be stored at low temperature for up to a month without significant alteration of its iodate content.
Studies on the diurnal and seasonal variations of
iodate are inconclusive. The iodate content in the surface
water at the Woods Hole coast is only about one half of that
in the South Atlantic surface water. The total iodine concentration is rather uniform in the sea. If iodate is consumed
by the reduction of iodate to iodide by bacteria, this difference in iodate concentration may be due to the higher
biological activity in coastal waters.
Iodate profiles from samples of stations 60 and 61 of
the Geosecs cruise, leg 5, in the Argentine Basin in the South
Atlantic show a surface depletion, a maximum at around 1500m.,
followed by a minimum and then a gradual increase towards the
bottom. The iodate profiles resemble the profiles of the
nutrients nitrate and phosphate. Phosphate-iodate, nitrateiodate and AOJ-iodate graphs show linear relationships with
correlation coefficients of 0.94, 0.95 and 0.88 respectively.
The molar ratios from these plots are AOU:nitrate:phosphate:
iodate = 2440:357:22.7:l or AOU:nitrate:phosphate = 108:16:1.
This is close to the reported ratios of AOU:nitrate:phosphate
= 138:16:1. From these ratios, it may be calculated that the
recycled iodate is 7-8% of the total iodate and that 90% of
the iodate is conservative,
Thesis Supervisor: Peter G. Brewer
Title:
Associate Scientist
Department of Chemistry
Woods Hole Oceanographic Institution
Woods Hole, Massachusetts
-xi-
CHAPTER
I
INTRODUCTION
A. Purpose of the study
The purpose of this study was to examine the marine
chemistry of iodine in order to assess its involvement in the
biological cycles of the ocean and its use as an oceanic
tracer. The redox chemistry of iodine, and the previously
reported variations in seawater showed the potential use of
this system. As a first step, it was desirable to develop a
rapid, precise and simple method for the analysis of iodate
in seawater and then to use this method to carry out analyses
of vertical profiles of iodate in the ocean.
These data,
together with observations of diurnal and seasonal variations
should give important information on the iodine system in
seawater.
B. Iodine in the sea
The presence of iodine-containing substances has been
known to man for a long time. It is believed that a legendary
Chinese emperor Shen-Nung, said to have lived in the third
millenium B.C., mentioned seaweed as an efficacious remedy
against goiter in his treatise on herbs and roots (Langer
1960). Iodine can be found everywhere in nature in low con-1-
centrations, but elemental iodine was not discovered until
the early nineteen century (Courtois 1813).
Studies on the iodine system in the marine environment can be traced back to 1825 when Pfaff detected iodine in
Baltic seawater, and later, it was also found in French
coastal waters by Laurens in 1835 (Riley 1965a). Agreement
among the early quantitative determinations of iodine varied
widely from 0.017 ug/l (Macadam 1852) to 8000 ug/l (Marchand
1855). Winkler (1916) arrived at a more reasonable value of
38 ug/l. He also suggested that both iodide and iodate were
present. The speciation of iodine in the sea has been a rather
controversial subject. Sugawara (1957) supported Winkler's
proposal because "iodate is the only possible iodine form in
higher oxidation state at the hydrogen ion concentration of
seawater". Shaw et al.(1957) suggested that hypoiodous acid
(HIO) is the dominant oxidized species. His main reasons were:
(1) the ratio of oxidized iodine to iodide is about unity, and
this ratio can be obtained by assuming a thermodynamic equilibrium in the system of hypoiodous acid, iodide, atmospheric
oxygen, water and hydrogen ions at the pH of seawater; (2) if
air is equilibrated with seawater containing hypoiodous acid
and iodide in equal amount, the iodine concentration observed
in marine air will be observed, and, seawater will be able
to lose iodine when exposed to iodine-free air as observed;
-2-
(3) the ratio of total iodine to chloride is higher in warm,
partly enclosed sea areas and this can be explained by the
effect of temperature upon the equilibria mentioned in (1)
and (2) which results in an increase in the content of
volatile iodine molecules at lower temperatures; and, (4) the
disproportionation of hypoiodite is slow because it involves
third order kinetics. Sugawara et al.(1958) performed experiments to verify his own proposal. He showed that: (1) there
is no detectable amount of hypoiodite in seawater; (2) the
system iodine, iodide, hypoiodite and iodate reaches a thermodynamic equilibrium quickly with iodide and iodate as the
predominant components; (3) even in the presence of oxygen,
the oxidation of iodide to a higher oxidation state is quite
slow; and, (4) the ratio of oxidized iodine to iodide is not
unity and it varies from one location to another. Johannesson
(1958), in support of Sugawara, showed that: (1) the triiodide ion is not formed in seawater upon the addition of
excess iodide unless the seawater is previously acidified.
If hypoiodite is present, it will react with excess iodide
without acidification; and, (2) the oxidized iodine concentration, estimated from the tri-iodide concentration, will be
too large unless it is in the form of iodate. Shaw et al.
(1958) finally accepted that the oxidized form of iodine is
-3-
iodate because of the experimental evidences of Sugawara
(1958) and Johannesson (1958). It is presently generally
accepted that iodine is present in seawater primarily as
iodide and iodate and that the amount of organic iodine is
negligible (Sugawara et al.1957). Iodine complexes are generally less stable than those of the other halides (Cotton et
al.1962). Since chloride does not form significant amounts
of complexes in seawater, it is expected that iodide will
behave similarly. Some of the molecular properties of iodide
and iodate are compiled in table I-1.
The iodine concentration in seawater varies with
location
(Sugawara et al.1962) and with depth (Tsunogai et
al.1971). The iodide concentration may vary from below
detection limit to 0.2 uM (ca. 25 ug-I/1) while the range of
iodate concentrations is between 0.2 uM (ca. 25 ug-I/1) and
0.4 uM (ca. 50 ug-I/l) (Tsunogai et al.1971). Thus, the total
iodine concentration which is the sum of the two will be
constant at ca. 0.4 uM. These deviations can best be shown in
Tsunogai et al. (1971) and Tsunogai's (1971b) recent data in
figures I-1 and 1-2.
If iodate and iodide are the only important iodine
species in the ocean, one may consider the thermodynamics of
the iodate-iodide redox couple:
-4-
Table I-1. Some molecular properties of iodate and iodide*.
Iodate
Iodide
Formula
103'
I"
Oxidation state
+5
-*1
Radius of iodine atom (1)
VI 1.03**
VI 2.13**
VIII 1.97***
Ionic structure
Pyramidal
I-0 bond length (A)
1.83
% double bond character
20%
0-bond orbital
hybridization
sp3
Partial molal volume at
25.3
250C (cm3/mole)
*
Data compiled from Cotton et al. 1962,
---.
36.22
Douglas et al. 1965,
Rankama et al.1950, Whittaker et al.1970, Millero 1971,
and Nightingale 1960.
**
Co-ordination numberVI.
*
Co-ordination number VIII.
-5-
Figure I-1.
Iodine profiles from the Pacific and their
station positions. Tsunogai et al.1971,
Tsunogai 1971b.
Fig. I-la.
The vertical distribution of iodine at 120 01'N,
158 0 02'E in the North Pacific where the depth is
5855m. The concentration of iodide(.), iodate
(x) and total iodine (o) are indicated.
Fig. I-lb.
Vertical distribution of iodide-iodine and total
iodine with salinity (.)
and temperature (x) at
the Tonga Trench (23011'S, 174 040'W), where the
depth is 10200m.
Fig. I-lc.
Vertical distribution of iodide-iodine and total
iodine with salinity (.)
and temperature (x) at
60000s and 169 0 55'W in the Southern Ocean.
Fig. I-lb
Fig . I-la
3
0.4Jg at/L
0.2jpg at/lt 0.3
0.4
a
-
Total
lide
-2
km
-3
-5
I T 10I
8
35 *.
35.5
20 *C
30
34.5
s
-4
10
0.1
0.3 pgat/l 0.4
0.2
180
cO00O***
-40
dooooooo0000o0o*
* KH-70-2
0
0
0o
0
0
00
0
000
e3
0
Oil
a KH-70-l
*20
0
KH69-4
. -10
*5 Oshoro
~--i
S.
@N
0
Se1-0
160*E
180i
,. 0
160'110
0
0
10
.10Os
S
34
I
I
00s
0-.
0
34.5
I
0It
20KH-68-4
*
30-
0
Ti:
0
180 6
40-
0
*.
-
Fig. I-ld
Fig, I-lc
-6-
SIC
50'6-
Figure
1-2.
Variations in iodide-iodine and total iodine
in the Pacific. Tsunogai et al.1971.
Fig. I-2a.
The concentration of iodide-iodine in the equatorial Pacific along 170 0W section. Circles and
triangles in the figure show the sampling location, and depth and the ranges of concentration
which are 0.025-0.05 (A),
0.15 (.)
0.05-0.10 (A),
0.10-
and 0.15-0.21 (o) in the unit of
ug-at/l.
Fig. I-2b.
The concentration of total iodine in the same
station as Fig. I-2a. Solid circles show the
concentration range of 0.36-0.39 ug-at/l and
open circles show range of 0.39-0.42 ug-at/l.
a
S
I
a
a
oi
N
40a
o
00
8
o
0
0
0 c
0 00 0
0
c
0
0000
00
0 @00
00
tJ00o
.000
"Do0
0
*0
G00
00o 000
0
4
0
a
0
0
a
I
103- + 6H+ + 6e- = I'
log K = 110..l
+ 3H2 0
(Bjerrum et al.1958).
Therefore,
K=
[I-I
6
[103-] [H+] 6 [ej
or, log
|0O3~ = 6pH + 6pE - log
K ----
(1)
[I-]
In normal seawater, pH = 8.1, and pE = 12.5 (Sillen 1961).
Therefore, [103]
=
[I-]
The equilibrium concentrations of both species can also be
shown by a concentration diagram as in figure 1-3. Total
iodine concentration is assumed to be 0.4 uM and the pH is
fixed at 8.1. The concentration of each species at various pE
can be calculated from equation (1). This diagram indicates
that, at equilibrium, the amount of iodide in seawater is
negligible. However, experimental findings show small but
significant concentrations of iodide and this dis-equilibrium
has been noted for some time (Goldberg 1963; Sillen 1961;
Riley et al. 1971).
Recently, Tsunogai et al.(1969) proposed that this
dis-equilibrium is caused by biological activity of bacteria.
They demonstrated that bacteria, that are capable of reducing
nitrate to nitrite, can also reduce iodate to iodide enzyma-8-
Figure 1-3. The concentration diagram of the iodide-iodate
couple at a pH of 8.1 and with a total iodine
concentration of 0.4 ug-at/l.
-6-
-7
-6
I
I
I
LOG CONCENTRATION
-5
I
(LOG
-~
I
uM)
-2
-
I
I
0,
tri
tically. The enzyme used may be nitrate reductase. Although
the importance of iodine as a nutrient for marine plankton
has not been firmly established, recent work has shown that
marine plankton do take in and excrete iodine, mostly in the
form of iodide (Kolehmainen et al.1969; Kuenzler 1969).
It
is
also known that iodine is involved in the biological activity
of some species and is essential for red algae, brown algae
and mammals (Bowen 1966). The metabolism of iodine in the
higher animals has been well documented (Gross 1962). For
plants, a suitable amount of-iodine is necessary in order to
provide a favorable growth stimulation (Hanson 1963). In all
marine species, iodine can be found in their body tissues
(Hanson 1963).
If the iodate and iodide concentrations in the oceans
are controlled mainly by biological activity, environmental
changes that can vary the amount of biological activity will
be reflected in the iodate-iodide ratio. These environmental
changes may be seasonal variations, latitude changes, temperature changes, etc. Since biological activity is highest in
surface waters, the greatest variations may be observed there.
Some work has already been done in this direction in the
Pacific (Tsunogai et al.19711 Tsunogai 1971b). It has been
observed that the highest iodide concentration is in the sur-
-10-
face water. In the surface layer, the concentration of iodide
is higher in warm water (that is, above 200C, average concentration = 0.1 ug-at/l) than in cold water (that is, less than
2000, average concentration = 0.03 ug-at/1). Among the warm
waters, the highest iodide concentration is found in the
equatorial zone (average concentration = 0.13 ug-at/1) where
the biological activity is also high. Table 1-2 is a summary
of their results.
If iodine is being taken in by plankton, it may bear
some relationship to the other nutrients (for example,
phosphate and nitrate). From Vinogradov's (1953) data, one
can see that the P/I ratio is approximately constant within
a single species despite the crudeness of the data (see
table 1-3).
C. Analytical methods for the analysis of iodine in seawater
The low abundance and the narrow range of concentration of iodate renders a precise and sensitive analytical
method a necessity for a reliable quantitative study. Riley
(1965) listed the available methods prior to 1965 (see table
1-4). In recent years, a few more methods or modifications of
the older methods have been proposed. These methods are also
listed and summarized in the same table. The analytical pro-11-
Table 1-2. Mean concentration of iodine in the surface
water. Tsunogai et al 1971.
Location
Depth
Temp.
No. of
samples
I"
IO3'
Total I
10-' ug-at/l
0C
Lat.
Long,
m.
20N-
1700W
0
10
12±3
26*3
38±1
30
10
13&3
26*3
39t1
66
10.
14+3
25*5
39*1
100
10
13±4
27*3
40+1
Vari- 170 0W
0
>20
15
10±3
27±2
37t2
0
<20
13
2+1
34+1
36±l
0
>20
15
7±2
28+2
0
<20
3
3±2
31*3
34±1
40
2.5+2
38±3
41*2
ous
Vari- 137- 0
ous
163 E
Vari- 170 0W >1000
ous
-12-
Table 1-3. P/I ratio in some algae*.
Iodine (I)
% Dry Weight
Phosphorus (P) I/P
% Dry Weight, Ratio
0.27
o,44
60%
"
0.20
0.44
45%
-U
0022
0.44
50%
Stem
0.13
0024
50%
Lamina
0018
0.38
50%
Nereocystis luetkeana
0.14
0.34
40%
Stem
0.07
0.23
30%
Leaf
0.1
0.37
30%
Macrocystis pyrifera
U
-
* Data from Vinogradov (1953).
-13-
Table I-4. Analytical methods for the analysis of iodine
in seawater.
Approx.
conc.
found
(ug/1)
Method of separation
Method of
deterlnination
Reference
43
Iodate reduced with As2 O3
Photometric
Reith 1930.
Titrimetric
Skopintsev
+ HCl,
iodine liberated
with nitrate and extracted
with CC1 4 .
26-56
Oxidized to 103
MnO4,
with
and Mikhai-
reduced the latter
with C2042-, treated with
lovskaya
I- and acid, liberated
1933.
iodine titrated.
Direct method, depending on
Photometric
catalytic action of I- on
Dubravcic
1955.
reaction between Ce4+ and
As3+, remaining Ce4+
determined.
Total I
I-
= 7-57
AgOl, converted to 103-
co-precipitated with
-14-
Photometric
Sugawara
with starch-
et al.
Table I-4. (continued)
Approx. Method of separation
conc,
found
(ug/l)
Method ofdetermination
Reference
I03--I
with Br. Reacted wit]h acid-
iodine
1955,
= 0-5
ified I-, liberated iodine
color
1957.
measured. Total I by reduction of IO"
with S0 3 2 -
followed by determination
of I~ as described above.
Total I
IO3- reacted with iodide,
Ampero-
Barkley et
=45-70
liberated iodine treated
metric
al. 1960a,
I0 3-I
with excess S20 3 2 -,
titration
1960b.
which
was titrated with iodate.
Total I by oxidation of I~
with Br to IO3"
which was
determined as described
above. Total I also deter-
Photometric
mined by its catalytic
with
effect on the reaction of
brucine
Ce4+ with As 3+,
Total I
Catalytic effect of I~ on
Photometric Voipio 1961,
=60-118
reaction of Ce4+ with
measurement Kappanna et
-15-
Table 1-4. (continued)
Approxr., Method of separation
cone.
found
(ur/1)
Method of
determination
Reference
of residual al.1962.
As3+,
Ce4
Modified Sugawara method,
a. Photo-
reduction of 103-0 with
(NH2 )2 .H2SO.
metric mea- et al. 1970.
Matthews
surement of
tri-iodide
ions.
b. Photometric microtitration
with S2032-
I--I
Improved Sugawara method.
Photometric Tsunogai
= 0-25
with starch et al.1971;
103--I
=25-50
iodine
Tsunogai
color
1971a, 1971b.
Total I
10 3- reacted with iodide-
Photometric Schnepfe
=55-90
starch mixture directly.
with starch 1972.
Total I by oxidation of I~
iodine
-16..
Table 1-4.
Approx.
conc.
found
(ug/l)
I03--I
=37-64
(continued)
Method of separation
Method of
determination
with alkaline KMnO4 to
1O-, which was dete rmined
color
as described above.
-17-
Reference
cedures of these methods usually involve the titration of
liberated iodine or photometric procedures which may depend
on: (1) the catalytic action of iodide on the oxidation of
arsenic(III) by cerium(IV); (2) the color intensity of
extracted iodine; or (3) the color intensit'y of the iodinestarch complex. Many of the procedures require initial
concentration and separation steps or a control of the chlorinity. Some of these methods do not distinguish between the
iodine oxidation states. Some others have a precision insufficient to detail the range of variations that are expected
in the ocean.
Partly because of these analytical difficulties, the
amount of data obtained thus far on the distribution of iodide
and iodate in the sea is very sparse. The data reported by
different investigators are also quite different as summarized
in table I-4. The more reliable data probably were obtained
by Sugawara's (1955) method or its modifications (Tsunogai
1971a; Matthews et al.1970) which are capable of determining
iodide and iodate separately. In this method, iodide is coprecipitated as silver iodide with a silver chloride carrier
from several hundred milliliters of seawater. The precipitate
is separated from the supernatant liquid and then treated with
bromine water. Bromine oxidizes iodide to iodate and the excess
-18-
bromine can be removed by boiling. The iodate can then be
converted to iodine with excess iodide-in an acidic solution.
Tsunogai (1971a) determined iodine as the iodine-starch
complex colorimetrically at 570 rm. and claimed a coefficient
of variation of 3%. Matthews et al.(1970) converted iodine to
the tri-iodide complex and determined it either spectrophotometrically at 353 nm. or by a photometric micro-titration
with a standard thiosulfate solution. They claimed a coefficient of variation of 1% for the spectrophotometric method
and 0.4% for the titration methpd. Iodate can be determined
similarly after being reduced to iodide. A schematic description of the methods is given in figure 1-4. There are several
drawbacks in using these methods. First, they are very timeconsuming. Only about three to four samples can be analyzed
for both iodide and iodate in two to three days. Secondly,
these methods also involve the use of bromine water, which is
rather unpleasant to handle. Besides, the procedure is complicated and cannot be easily automated, or be done at sea.
Consequently, these methods are probably not suitable if a
large number of samples are to be analyzed. Thus, it would
be desirable if a fast, simple and accurate analytical technique can be developed for the routine analysis of iodate
and iodide. The Matthews' method is used in this study as a
-19-
Figure 1-4. The analytical scheme for the analysis of
iodide and iodate by co-precipitation.
-20-
Soluble silver
salt e.g. AgNO
3
Seawater
Ag+ + I- = AgI
Ag+ + Cl- = AgCl
Ag+ + Br- = AgBr
Supernatant
liquid
Precipitate
(Ag, AgCl,
Bromine
water
AgBr
AgI + 3Br 2 + 3H2 0 =
4
2 I03'
103- + AgBr + 5Br- + 6H+
'Supernatant
Precipitate
N2H.H2SO4
N2H
liquid
HSL
103I3
+ 3(N 2 H4 .H2 SO4 ) =
21- + 3N2 + 6H20 +
3H2 SO4
~I
103
AgCl, AgBr
* Steps for removing possible interfering species,
for example, BrO~.
**
For the determination of 12, please see the next page.
-21-
Fig. 1-4. (continued)
Tsunogai's Improved Sugawara Method
Matthews and Riley's Method
Photometric
micro-titration
Spectrophotometric Determination
standard method for determining the reliability' of the new
method.
-22-
CHAPTER
II
THE ANALYTICAL METHOD
A. The feasibility of a direct method
The ideal method will be a simple and rapid method
that does not require pre-concentration steps and has a
precision of ±3% or less. After a survey of the literature
(table 1-4), it seems that a photometric method will be most
promising.
The feasibility of a direct method will depend on.
(1) an absorbing species that can give-a detectable absorption at such a low concentration; (2) absorbances that obey
Beer's Law in that concentration range; (3) the absence of
other species in seawater that may interfere with the formation of the absorbing species; and, (4) the absence of other
species that absorb at the same wavelength as the absorbing
species.
The most probable absorbing species that may be used
seems to be the tri-iodide ion. Tri-iodide ion has been
generated in seawater (Johannesson 1958) and it absorbs
strongly at 353 nm. Moreover, for each iodate ion, three
tri-iodide ions are formed according to the equation:
103~ + 81
313
+ 6H+
+ 3H2 0,
and thus, the absorption will be amplified three fold . With
-23-
a 10 cm. cell, one may be able to detect a significant absorbance of the tri-iodide ions generated from seawater directly.
B. Initial tests
i. The Beer's Law region for the tri-iodide ion
Known volumes of a standard 8 uM potassium iodate
solution were put into 50 ml. volumetric flasks and 0.25 g.
of potassium iodide and 1 ml. of 0.1 M sulfuric acid were
added into each flask. The resulting solutions were diluted
to volume with distilled water. Absorbances of the solutions
were recorded at 353 nm. after fifteen minutes. The results
are summarized in table II-1. The iodate concentration ranges
from 0.16 uM to 0.80 uM which encompassed the iodate concentration range of 0.2 uM to 0.4 uM and total iodine concentration of 0.4 uM (Tsunogai et al.1971). The absorbance
against iodate concentration plot (figure II-1) shows a linear
relationship. This shows that the tri-iodide ion concentration
generated from the iodate or total iodine in seawater will
give a detectable absorbance using the presently available
spectrophotometer, and, furthermore, the Beer's Law is obeyed
in the iodate and total iodine concentration ranges in seawater.
-24-
Table II-1. Reaults for testing the Beer's Law region of
the tri-iodide ions at 353 nm. in a 10 cm. cell.
Volume of
8 uM KIO?
used (mlJ
Final
Volume
(ml)
Final Iodate
Conc. (uM)
Absorbance
1
50
0.16
0.101
2
50
0.32
0.225
3
50
0.48
0-342
5
50
0.80
0.608
-25-
Figure II-1. The Beer's Law region of the tri-iodide ion
absorption at 353 rm. in a 10 cm. cell.
4
1
44
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
t~)
IODATE CONCENTRATION
(uM)
I
ii. Determination of the iodate concentration in a standard
iodate solution using the standard addition method
The procedure is the same as that for the determination of iodate in seawater which will be described later.
Five trials were made. The results are tabdlated in table
11-2. The standard iodate solution is 0.2 uM or 25.4 ug-I/l
which is close to or lower than the lower limit of the iodate
concentration in seawater. A graph of average absorbance
against the amount of iodate-iodine added is plotted. The
iodate concentration thus determined is 26.2 ug-I/l and the
deviation from the theoretical concentration is 3%. This
experiment shows that this method is suitable for the determination of iodate at.low concentrations. Moreover, the
deviation of 3% (which assumes that there is no uncertainty
in the theoretical concentration) is within the goal of ±3%
of coefficient of variation.
iii. Experimental conditions
The reactions involved in the generation of triiodide proceed smoothly at room temperature. No special
experimental conditions are required. However, the excess
iodide is liable to slow air oxidation. Therefore, absorbances must be recorded within a few hours of tri-iodide
-27-
Table 11-2. Results for the determination of iodate
concentration in a standard iodate solution.
Absorbance
I
II
III
IV
V
Average
Absorbance
0.000
0.184
0.141
0.127
0.141
0.135
0.1456
1.015
0.274
0.266
0.264
0.275
0.265
0.2688
2.030
0.395
0.405
0.408
0.418
0.415
0.4082
3.045
0.520
0.531
0.539
0.543
0.559
0.5384
I02~-I1
added
(ug)
From the average absorbance against iodate-iodine added plot,
y-intercept (I) = 0.138, and slope (S) = 0.132.
Therefore,
103- = I x 25 = 26.2 ug-I/l.
Concentration of the standard iodate solution is
0.2 uM or 25.4 ug-I/1.
Thus, the deviation from the theoretical concentration is
26.2-25.4 x 100%
= 3%.
25.4
-28-
formation.
iv, Theoretical interferences
Possible chemical species that may interfere with the
analytical procedure have also been examinea. The major
reactions involved in the analytical scheme are :1) 103~ + 51~ + 6H+ = 312 + 3H2 0
2) 3I2 + 31
= 313
(in the presence of excess
iodide)
-3+ S4062-
and 3) 13" + 2S 2 03 2-
(for the titrimetric method
only)
Reducing agents that are capable of reducing 12 or 13
to'I~
will decrease the iodate concentration found and oxidizing
agents that can oxidize the excess iodide to iodine will
increase it. Other species that can react with thiosulfate
will also increase the iodate concentration in the titrimetric method.
A survey of the more probable interfering species
and the reactions that they may be involved in are listed in
table 11-3. The data were obtained from Jacobson (1949). Of
course, there are still other chemical species that can
react with iodide or iodine, but they are not present in the
ocean, for example, bromine and hydrazine. There are several
-29-
Table 11-3. Some possible interfering species.
Conc. of
interfering
species in
seawater
(ug-at/l)
Interfering
species
Reaction*
Reaction*
conditions
Cu 2+
2Cu 2 + + 4I" = Cu2 I2 + 12
none
<0.05
N02
2N0 2 - + 21
presence
0.01***
+ 4H+ =
2NO + 12 + 2H 0
2
**
of mineral
acid
MnO4"'
2MnO4
+ I
+ H2 0
boiled
negligible**
very acid-
negligible**
ic condi-
present as
tion
solid Fe(OH)3
saturated
negligible**
2Mn0 2 + IOf-+ 20H~
Fe 3 +
H2 S
2Fe3+ + 21" = 2Fe 2+ + 12
H 2S + I2 = S + 2H+ + 2I~
with H 2S
So3 2 -
So3 2- + 12 + H2 0
+ 2H+
SO42- + 21
S20 3
2S 2 032- +
31-=
acidic
negli-
solution
gible**
none
negligible**
S 4 0 6 2 ~ + 312S 2 0 3 2-
+ 12 =
none
S406 2- + 21"
H3 AsO 4
H 3 AsO4 + 21
+ 2H+ =
strong-
0.04****
Table 11-3. (continued)
Interfering
species
Reaction*
Reaction*
conditions
H3 As04
HAs0 2 + 12 + 2H2 0
mineral
acid
*
Jacobson 1949
**
Goldberg 1963
***
****
Wada et al.1972
Johnson et al. 1972
Conc. of
interfering
species in
seawater
(ug-at/1)
reasons that make the effect from the possible interfering
species negligible. Firstly, their concentrations in the open
oceans are low when compared to that of iodate. The average
concentrations of these interfering species in the oceans
are also listed in table 11-3 if they are available. Secondly,
the reactions involved in the analysis of iodate are rapid
and do not require extreme reaction conditions (for example,
heating) as some of these interfering reactions do. Thus, all
interfering reactions that are slow or require specific
reaction conditions will have negligible effect. Thirdly, for
each iodate ion, three tri-iodide ions are formed. This means
that the contribution of iodate to the absorbance is being
amplified three-fold. The interfering species do not have
this amplifying effect. Thus, their interfering effect is
reduced by a factor of three.
v. The tri-iodide ion absorption curve
The absorption curves of the tri-iodide ions developed
from a sample of seawater and from a pure iodate solution of
comparable concentration (0.2 uM) (figure 11-2) are identical.
Both exhibit maxima at the same wavelengths. A prominent
maximum is observed at 3500 A (350 nm.). The ratio of the
intensities of corresponding maxima is also the same. No
-32-
Figure 11-2. The tri-iodide ion absorption curve.
A. Developed from a 0.2 uM standard potassium
iodate solution. Solid line.
B. Developed from seawater. Broken line.
Chart speed l 5 in./min.
Scanning speed : 25 I/sec.
.Path length 1 10 cm.
X is the point at which the light source
was switched from visible to UV.
2500A
INTENSITY SCALE FOR CURVE A
0.0
.05
1
.1
1.0
.2
1.5
2.0
WOW
00I
0.0.00-l0
N
3500A
500A
I -
.4
0.0
INTENSITY SCALE FOR CURVE B
1
I
.5
I
1.0
1.5
shoulder or extra baseline noise can be observed in the seawater curve. This shows that there is no interfering species
in seawater which absorb at around the wavelength of 350 nm.
C. The analytical method
i. Instrumentation
Absorbances are recorded by a Beckman DU quartz
spectrophotometer light source fitted with a Gilford Model
2220 adapter and a Gilford Model 222 photometer and regulated power supply.
For the standard addition method, absorbances are
measured with a matched pair of 10 cm. cells. For the photometric micro-titration, the housing for the cells was modified as shown in figure II-3a. The titration cell is a
modified version of the standard 10 cm. cell (as shown in
figure II-3b). A Gilmont No. 7846 Buret with a maximum
capacity of 2.0 ml. and divisions of 0.002 ml. is used for
the titration. The Luer joint is
fitted with teflon adapters
from Rainin Instrument. A teflon tube is used to connect the
buret to the cell (see figure II-3c).
ii.
Standard solutions
The following standard solutions were prepared prior
Figure
11-3. The apparatus.
Fig. II-3a. The titration cell.
Fig. II-3b. The modified housing for the titration cell.
Fig. II-3c. The titration buret.
-35Fig. II-3b
Fig. II-3a
COVER
I
/
,-
I
TO
DETECT?
1CYR.
.1
TEFLON
ADAPTOR
MICRO-BTJPET
TEFLON
DELIVERY
TUBING
Fig, II-3c
IT
IG
--
CTPI
'j,
to the analysis :-
1. 5% potassium iodide solution
Five grams of potassium iodide crystals were weighed
out and traferred into a 100 ml. volumetric flask. The
crystals were dissolved in a small volume of distilled water
and then diluted to volume.
2. Standard potassium iodate solutions
2.14 g. (0.01 mole) of potassium iodate crystals were
weighed out and transferred into a 500 ml. volumetric flask.
The crystals were dissolved in a small volume of distilled
water and then diluted to volume to form a 20,000 uM stock
solution. Iodate solutions with concentrations of 2,000 uM,
200 uM, 20 uM, 8 uM, 4 uM, 0.4 uM and 0.2 uM were prepared
from this stock solution by successive dilutions.
3. 0.1 M sulfuric acid
25 mi. of concentrated sulfuric acid (36N) was added
slowly and in small increments to 400 ml. of distilled water
with intermittent swirling and cooling in an ice-water slush
bath. After all the sulfuric acid had been added and the
solution cooled, another twenty five milliliters of distilled
water was added to the solution in the same manner. The
resulting solution is approximately 1 M. 50 mi. of the 1 M
sulfuric acid was pipetted into a 500 mi. volumetric flask
-36-
and diluted to volume to make a 0.1 M sulfuric acid solution.
4. Approximately 100 uM sodium thiosulfate solution (Kolthoff
et al 1969)
About 3 1. of distilled water was boiled for 30 minutes and then cooled back to room temperature. 2.48 g. (0.01
mole) of sodium thiosulfate pentahydrate .was.weighed out and
transferred into a 100U ml. volumetric flask. About 0.1 g.
of sodium carbonate was weighed out and added to it. The
solids were dissolved in a small volume of the freshly boiled
water and then diluted to volume. The resulting solution was
about 10,000 uM. Thiosulfate solutions with concentrations of
1000 uM and 100 uM were prepared from this stock solution by
successive dilutions. About 0.05 g. of sodium carbonate was
dissolved in every 500 ml. of solution. The freshly boiled
water was used for the preparation of all these thiosulfate
solutions.
The thiosulfate solution was allowed to stand overnight before standardization. The standardization procedure
is the same as the photometric micro-titration method for the
determination of iodate in seawater except that a standard
0.4 um iodate solution is used instead of seawater. The thiosulfate solution should be standardized just before the
the titrations are performed.
-37-
iii. Procedure for the analysis of iodate in seawater
Allow the stored samples to warm up to room temperature just before the analysis. Shake the sample bottle vigorously in order to ensure thorough mixing. Filter the sample
through a Whatman 40 ashless filter paper with suction. After
that, the sample can be analyzed by one of the routes shown
in figure 11-4.
1. The standard addition method
Pipette 40 ml. of seawater into each of a set of four
50 ml. volumetric flasks. Mark the flasks 0, 1, 2 and 3 and
pipette 0, 1, 2, and 3 ml. of an 8 uM potassium iodate
solution (1.015 ug 103~-I/ml) into each flask accordingly.
Add 0.25 g. of potassium iodide, as solid crystals or as a
5 ml. aliquot of a 5% (w/v) potassium iodide solution, and
1 ml. of 0.1 M sulfuric acid to each flask and then dilute
the solutions to volume. Shake the flasks and then record
the absorbance of each solution in a 10 cm. cell at 353 nm.
after fifteen minutes with seawater as the reference. Repeat
this procedure two more times for each sample. Plot the
average absorbance against the amount of iodate-iodine added.
The slope (S) and the intercept (I) of the graph can be
determined either graphically or by a linear regression
calculation. The iodate concentration in ug-I/1 is given by:
-38-
Figure 11-4. The analytical scheme for the analysis of
iodate and total iodine.
-39-
Total Iodine
Iodate
IO3~
I~ + Oxidizing agent
>
Photometric
microtitration
Addition
method
103
03~
=
x 25.
one can use the relationship of 1 uM-I = 126.9 ug-I/l to
convert the result to uM-I.
2. The photometric micro-titration method
Pipette 30 ml. of the filtered seawater into the cell
and add to it 0.25 g. of potassium iodide crystals, 1 ml. of
0.1 M sulfuric acid and distilled water until the final
volume is 38±1 ml. Put the titration cell into the spectrophotometer and insert the delibery tube of the buret into
the cell. Using seawater as the reference, read the absorbance
at 353 nm. after about ten to fifteen minutes of stirring and
at one minute intervals thereafter until a constant absorbance
is reached. Balance the spectrophotometer before each reading
using the seawater reference. Then, add the standardized
thiosulfate solution from the buret at known volume intervals
of 0.1 or 0.2 ml. After each addition of the thiosulfate
solution, stir the solution for one minute and then read the
absorbance at half to one minute intervals until a constant
absorbance is attained. Again, the spectrophotometer is
balanced before each reading. The end-point is reached when
no further decrease in absorbance is observed upon further
additions of thiosulfate solution. Take at least five points
before and after the end-point. Plot (Vi+AV)A against AV
-40-
(where Vi is the initial volume, AV is the volume of thiosulfate added and A is the absorbance). The end-point is the
point where the two lines intersect.
A plot of (Vi+AV)A against AV is used instead of A
against AV in order to take into account the dilution effect
caused by the titrant and make the resulting graph linear.
This relationship is developed as follows.
Definition of symbols:
A
- absorbance at any point of the titration.
AO
-
initial absorbance before any thiosulfate solution
is added.
a
-
molar extinction coefficient.
b
-
path length.
C
-
concentration of tri-iodide ions at any point of the
titration.
Ci
-
initial concentration of tri-iodide ions.
CT
-
concentration of the thiosulfate solution.
Vi-
AV
initial volume.
-
total volume of thiosulfate solution added up to that
point.
VE.P.
-
volume of thiosulfate solution required to reach the
end-point.
A0 , a, b, Cj, CT and V- are constants. Vi and CT are known
quantities. The reaction that is involved in the titration is:
1 3 + 2S2 03 2- = 31
+ S406 2
Therefore, prior to the addition of any thiosulfate solution,
Ao = abCi, and
the amount of tri-iodide ions =ViCi.
After
V ml. of the thiosulfate solution is added,
amount of thiosulfate added = AVCT,
tri-iodide ions consumed =
tAVCTl
tri-iodide ions remained = (ViCi -
WAVCT),
and therefore, the concentration of tri-iodide
ions = (ViCi -
tAVCT)/(Vi
+ LV).
The resulting absorbance is
ab(ViCi - khVCT)
A=
(Vi + AV)
,or
(Vi + AV)A = (-abCT)AV + (abViCi).
Since a, b, Ci, CT and Vi are all constants, therefore, a
plot of (Vi + AV)A against AV will be a straight line. At
the end-point, ViCi =
bVE.P.CT.
Therefore, A = 0 or some
constant value if there is a residual absorbance due to improper alignment of the cells or other mechanical imperfection. One can therefore locate the end-point at the intersection of the two straight lines. The corresponding AV value
will be the volume of thiosulfate solution needed to reach the
-42-
end-point. Ci can be calculated from VE.P. because
VE.P.CT
2Vi
4
Since the tri-iodide ions are formed by the reaction
IO~ + 81~ + 6H+
=
313- + 3H20 -,
therefore,
Ci
[10 3
3 =
VE.P.CT
6Vi
*
Figure 11-5 is a sample plot of (Vi+AV)A against AV for a
titration. A against AV plots deviate
from linearity near
the end-point while the (Vi+AV)A against AV plot does not
exhibit such a deviation.
The initial volume, Vi, does not have to be known to
better than ±1 or 2 ml. The cell is calibrated so that Vi
will not vary for more than 1 ml. The effect on the end-point
is not detectable for a difference of 2 ml. in Vi.
iv. The precision of the analytical methods
One sample set of results is shown here for each of
the two methods - the addition method and the titration
method. The seawater was collected by the Woods Hole coast.
1. The addition method
The analysis was repeated five times and the average
absorbances of the five trials were used for the absorbance
-43-
Figure 11-5. A sample plot for the photometric microtitration.
I
0' 0
T
p
V (,V + TA)
I
2'
0o
-.44-
Table 11-5. Data for determining the precision of the photometric micro-titration method.
Vi = 39 + 1 ml
CT=
67.6 um
(ml)
A
(Vi+AV)A
0.00
0.184
7.176
0.10
0.20
0.124
4.861
0.30
(Vi+Av)A
III
A
(Vi+AV)A
0.183
6.954
0.186
7.068
0.152
5.791
0.159
6.058
0.123
4.699
0.126
4.813
0.092
3.524
0.096
3.677
.068
2.611
0.040
1.540
0.40
0.064
2.522
m.65
2.496
0.45
0.055
2.170
0.052
1.999
0.038
1.463
0.50
0.55
0.029
1.147
0.029
1.119
0.60
0.029
1.147
0.029
1.119
0.029
1.119
0.80
0.029
1.154
0.030
1.164
0.032
1.242
1.00
0.029
1.160
0.029
1.131
0.032
1.248
1.30
0.028
1.128
0.029
1.140
0.032
1.258
1.50
0.028
1.134
0.029
1.148
0.032
1.267
0.031
1.237
0.032
1.277
1.60
---
1.90
VEP
I03f
0.530 ml
0.534 ml
0.528 ml
0.199 uM
25.3 ug/1
0.201 um
0.198 uM
25.5
25.2
-45-
ug/1
ug/1
Table 11-5. (continued)
IO3'
VEP x 67.6
Vi x6
The average iodate concentration is
25.3 ug-I/1 ± 0.7%
-46-
against ug iodate-iodine added plot. The results are summarized in table 11-4 and the plot is shown in figure 11-6.
Using a linear regression fit, the iodate concentration was
found to be 27.2 ug-I/1 and the standard deviation is 2.7%.
Thus, the precision of this method is acceptable for the
study of the distribution of iodate in seawater.
Using this method, about six samples can be analyzed
in a day if, for each sample, three replica are analyzed.
This will be about twice as fast as the co-precipitation
method. The procedure involved is simple enough so that the
automation of this method with minor modifications in the
procedure seems very promising.
2. The titration method
The analysis was repeated three times for a single
sample of seawater. The results are summarized in table 11-5.
The iodate concentration was found to be 25.3 ug-I/1 with a
coefficient of variation of 0.7f. The lines of the titration
curved were fitted by eye. From the sample plot (figure 11-5),
it can be seen that the data points fall exactly into two
straight lines of different slopes. These two lines intersect at a sharp angle and consequently, the uncertainty in
the end-point will be small. It is hoped that a computer
program will be developed eventually to handle the line
-47-
Table 11-4. Results for the determination of the precision
of the addition method.
103-I
added
(ug)
Absorbance
I
II
III
IV
V
Average
Absorbance
0.000
0.135
0.127
0.117
0.123
0.127
0.1258
1.015
0.245
0.243
0.244
0.244
0.294
0.254
2.030
0.371
0.360
0.361
0.365
0.368
0.365
3.045
0.480
0.474
0.482
0.517
0.488
0.4882
The data was fitted to a straight line by a linear regression
program. From the program, slope (S) = 0.118 and the y-intercept = 0.1285. Therefore,
x 25 = 27.2 ug-I/l.
I03- =
The standard deviation is 2.7f.
-48-
Figure 11-6. A sample plot for the determination of iodate
in seawater by the addition method.
0.0
3.0
2.0
1.0
IODATE -IODINE
ADDED
(ug)
4.0
fitting task. This will eliminate prejudice from the investigator and also allow the calculation of confidence limits
for the end-points.
Using this method, eight to ten samples a day can be
analyzed. The procedure is-simple and the amount of chemical
manipulations is minimal making it possible for on board
analysis and automation. Also, the volume of sample required
is small (only about one fifteenth of the volume needed for
the co-precipitation method) making it possible for routine
analysis.
v. Correlation between the addition method and the titration
method
A sample seawater was analyzed three times by the
titration method and twice by the addition method. The average
iodate concentration is 25.8 ug 103~-1/1 ±2%. (The results
are summarized in table 11-6.) The difference of 2% from the
mean is within the experimental uncertainties of these two
methods and, thus, it may be concluded that both methods
give comparable results.
-50-
Table 11-6. Correlation between the addition method and the
titration method.
The results were obtained from the same sample of seawater.
Titration method
Number of replica
Addition method
3
2
25.3
26.3
Average iodate conc.
-
(ug If--I/l)
Average iodate concentration from the two methods is
25.8 ug 103'-/1 ± 2%
vi. Correlation between the addition and the Matthews and
Riley's method.
Samples of seawater were analyzed by both the addition
method and the Matthews' method. Iodate was analyzed by both
methods for one sample. For the other samples, iodide was
analyzed by the Matthews' method and iodate was analyzed by
the addition method. The results are summarized in table
11-7.
In the one case where the iodate concentration has
been determined by both methods, the results differ by 5%
from the mean (27.5 ug-I/1 +1.5 ug-I/l). This is within the
uncertainties of the methods. The iodate concentration determined by the addition method in the surface water at Woods
Hole is found to be lowwhen compared to open ocean surface
water, at 0.2 uM. (In open ocean water, it ranges from 0.3 to
0.4 uM.) The corresponding iodide concentrations found by
the co-precipitation method are all high and close to 0.2
uM. The total iodine concentration obtained by adding the
corresponding iodide and iodate concentrations from these
two methods are all around 0.4 uM. Since total iodine is
rather uniform in the oceans and in the Pacific, the total
iodine has been reported to be 0.4 uM (Tsunogai et al 1971),
it shows that the iodate and iodide values are probably
-52-
Table 11-7. Correlation between the addition method and the
Matthews and Riley's method.
Addition Method
Iodate
(ug-I/1)
Matthews' Method
Iodate
Iodide
(ug-I/1)
(ug-I/1)
26.0
29.0
Total Iodine*
(ug-I/1)
25.4
26.6
52.0
30.0
25.4
55.4
29.2
22.6
51.8
22.8
50.6
23.2
49.6
27.8
---
26.4
* Total iodine is the sum of the iodide and iodate concen-
trations from the two different methods.
-53-
acceptable, otherwise, the total iodine concentration will
not be close to that in the average ocean water.
The amount of data from the co-precipitation method
is small because of its technical difficulties and the time
required for each analysis. The method involves the use of
bromine and the complete removal of bromine was found -to be
difficult. Other workers have shared this same experience
(Liss, private communication). Any trace of residual bromine
can catalyse the oxidation of iodide to iodine. Since excess
iodide is used to generate the tri-iodide complex, this
excess iodide may be oxidized and give absurdly high iodate
or iodide concentrations. This flaw was detected in a rather
late stage of this research and the procedure was subsequently
modified to give the results summarized here. In the original
Matthews' method, the first batch of excess bromine was
removed by boiling and the second batch by bubbling nitrogen
through and adding phenol to the solution. In the modified .
procedure, in both instances, bromine was removed by boiling
for at least one hour.
One question that may arise is whether the addition
of reagents (for example, the addition of acid in the production of the tri-iodide ions) will alter the iodine composition in the sample by side reactions. The smoothness of
-54-
the graphs for both methods and the agreement among the
addition, titration and Matthews' methods suggest that the
interference is probably negligibly small.
This comparative study of the addition method and
the co-precipitation method shows that the accuracy of the
addition method is acceptable. Since the titration method
yields results comparable to those of the addition method,
its accuracy should also be acceptable. Summing up all these
studies, one may conclude that the new methods can give
highly reproducible results that are comparable to the values
obtained from the co-precipitation method.
D. Attempts for developing an analytical method for the
determination of iodide in seawater
In the original scheme (figure II-4), it was anticipated that iodide can be oxidized to iodate, and then the
total iodine concentration determined by the methods used
for the determination of iodate. The difference between the
total iodine and iodate concentrations will be the concentration of iodide in the sample. Several oxidizing agents
have been attempted but none of them seems satisfactory.
1. Sodium perchlorate
Excess sodium perchlorate was added to each 40 ml.
-55-
uM
of a 0.2 uM potassium iodate and 0.2,potassium iodide solution
in a 50 ml. volumetric flask. The solution was heated in a
hot-water bath. Total iodine was determined using the addition
method after the heating. The iodide concentration obtained
was low. At first, incomplete oxidation was suspected. The
oxidation step was studied intensively. Kinetic experiments
on reaction time and reaction temperature were performed. An
optimal condition of heating at 7500 for one and a half hours
was obtained. However, even under optimal conditions, the
iodide concentration found was still low, and only 20%O
con-
version was apparently achieved. This is probably because
perchlorate can only oxidize iodide to iodine. So, instead of
I-
>
3 --
3
> 312
>313-, one has 2I~
> 12
13*
Consequently, the amplification effect of the direct method
is lost. Iodide concentrations in seawater are much lower
than iodate concentrations, and, at times, may even drop to
zero. The loss of sensitivity by a factor of six is significant and as a result, this route was abandoned.
2. Bromine water
Bromine water can oxidize iodide to iodate. However,
the complete removal of bromine is difficult. As stated
earlier, any trace of residual bromine can catalyse the
oxidation of the excess iodide and give absurdly high results.
-56-
The toxicity of bromine also makes the use of bromine as the
oxidizing agent undesirable.
3. Alkaline permanganate solution
Iodide can be oxidized to iodate by boiling it with
an alkaline permanganate solution. Again, the complete
removal of the excess permanganate without side effects on
later steps is difficult. Moreover, manganese dioxide is
formed in the process. The removal of manganese dioxide by
filtration will cause some loss in sample solution and also
greatly increase the amount of manual manipulation.
-57-
CHAPTER
III
SAMPLE STORAGE
Effect of storage on the iodate content of seawater
A. A qualitative study
About 40 1. of seawater was collected and about one
half of it was filtered. The iodate content in it was determined by the addition method. Ten one-liter glass erlenmeyer
flasks and ten polyethylene bottles were used for sample
storage. About 2 1. of the unfiltered seawater was put into
each of five glass flasks and five polyethylene bottles and
about 2 1. of the filtered seawater was put into each of the
remaining bottles. Each sample in each set of five bottles
was stored under different conditions and all of them were
analyzed for iodate again after eight days. The qualitative
results are summarized in table III-1.
In all cases when chemicals are added, the absorbances
are all much higher than would be observed for a non-spiked
sample. This may be cause by a change in the iodate concentration or by the absorption of the added chemical at 353 nm.
as in the case of mercuric chloride. Both sets of bottles
give similar observations showing that either glass or polyethylene bottles can be used. The filtered sample and the
-58-
Table III-1. The qualitative effect of storage on the iodate'
content in seawater by various storage methods.
Storage Conditions
Temperature
Chemical Added
50C
None
No observable change.
Room temperature
None
No observable change.
Room temperature
Hl
High absorbance.
Room temperature
Toluene
High absorbance.
Room temperature
HgCl 2
Very high absorbance.
Effect of Storage
-59-
unfiltered samples also give comparable results. From this
qualitative study, it seems that a possible way for storage
is by temperature control.
B. A quantitative study
The samples were all stored in polyethylene bottles
and the seawater was not filtered before storage. Three
storing temperatures were used: room temperature, 500 (refrigerator temperature), and frozen (freezer temperature). The
results are tabulated in table 111-2.
This study shows that seawater can be stored for up
to four to five weeks at low temperature with negligible
effect on the iodate concentration. Storing at room temperature will cause the iodate concentration to increase
slowly. This is probably due to the oxidation of iodide to
iodate as predicted by the thermodynamic equilibrium calculation upon the death of the bacteria. Frozen samples give
comparable results after being re-frozen and being stored
for another week or two. The frozen samples were all from
the Southern Atlantic. They all have concentrations comparable to those reported for the Pacific (Tsunogai 1971b;
Tsunogai et al.1971). This shows that the iodate concentrations probably have not been changed during storage.
-6o-
Table 111-2. A quantitative study on the effect of storage on
the iodate content in seawater by controlling
the storage temperature.
Storing Temperature
Room temperature
50C
50 C
Frozen sample
Frozen sample
Frozen sample
Time of Storage
(day)
Iodate Concentration
(ug-I/l)
0
27.8
9
26.8
35
41.1
0
27.8
9
28.4
36
29.4
0
26.0
7
26.4
18
25.0
16
59.2
28
56.9
16
59.6
28
61.2
16
62.7
26
61.6
Table 111-2. (continued)
Storing Temperature
Frozen sample
Time of Storage
(day)
Iodate Concentration
(ug-I/l)
11
60.5
26
60.3
-62-
CHAPTER IV
THE DISTRIBUTION OF IODATE IN THE SEA
A. Seasonal variations in the iodate content of the Woods
Hole coastal surface water
Surface seawater samples were collected between 0900
and 1200 off Woods Hole at intervals of a few days from July
to November. Water was collected with a 20 1. polyethylene
bottle and was brought back to the laboratory for immediate
analysis of iodate. The results are shown in table IV-l. A
plot of iodate concentration against date of sample collection
is shown in figure IV-l.
This study on the seasonal variations of iodate
concentrations in the surface water is far from conclusive.
First, the spring algal bloom was missed. The most pronounced
change should be observed in this period. Secondly, the
location for sample collection was so close to shore that
tidal effect may carry seawater from greater depths with
higher iodate concentration to the surface and cause changes
in iodate concentration. The tidal effect may be eliminated
if the sampling site is a little further away from the shore.
Alternatively, a large tank filled with surface water may be
used to approximate the surface ocean and more control on the
exp.erimental conditions will be obtained. Under normal cir-
-63-
Table IV-l. Seasona1~variations in the iodate content of
the Woods Hole coastal surface water.
Date of Collection
Iodate Concentration
(ug-I/1)
July 13, 1972.
27.2
Aug. 9, 1972.
27.8
Sept. 18, 1972.
30.2
Sept. 25, 1972.
26.0
Oct. 2, 1972.
24.7
Oct. 3, 1972..
25.4
Oct. 9, 1972.
27.8
Oct. 10, 1972.
26.4
Nov. 7, 1972.
26.3
Nov. 21, 1972.
25.7
-64-
Figure IV-1. Seasonal variations in the iodate content
of the Woods Hole coastal surface water.
0
- O
Q00
ci
C4
20
0~
~~
30
IODATE CONCENTRATION
(ug-I/1)
40
cumstances,
if
iodate is being reduced by bacteria to iodide,
iodate concentrations should be inversely proportional to
the amount of biological activity. A maximum change of 5
ug-I/1 (or 15-20%) of iodate has been observed in the period
of July 13 to Nov. 21, 1972. There was a su'dden dip in iodate
concentration from Sept. 18 to Oct. 3. The red tide, which
is an indicator for high biological activity, was observed
in the coastal water off Northern Massachusetts in Sept. 14
(Boston Globe 1972). This dip may be related to this increase
in biological activity. However, I must emphasize that this
conclusion is a highly speculative one. More data will be
needed before a firm seasonal trend of iodate concentration
variations can be established.
B. Diurnal variations in the iodate content in seawater
Surface seawater samples were collected in the same
manner and at the same place as mentioned in the previous
section on Oct. 9 and Oct. 10, 1972 at various time of the
day. Iodate was analyzed by the addition method immediately
after collection. Phosphate was analyzed by the method of
Murphy et al.(19 6 2). The results are shown in table IV-2. A
graph of phosphate and iodate concentrations against time
of the day is shown in figure IV-2.
-66-
Table IV-2. Diurnal variations in the iodate content and
the corresponding changes in the phosphate
concentration of the Woods Hole coastal surface
water.
Date of
Collection
Oct. 9, 1972
Oct. 10,
Time of
Collection
Iodate
Concentration
(ug-I/l)
Phosphate
Concentration
(ug-P/l)
0925
27.8
19.6
1257
30.0
18.8
1625
29.2
17.9
0730
26.4
19.1
1972.
-67-
Figure IV-2.
Diurnal variations in the iodate content and
the corresponding changes in the phosphate
concentration of the Woods Hole coastal water.
A. The iodate concentration vs. time of day
curve.
B. The phosphate concentration vs. time of
day curve.
-99-
0
H>
'-3
H
nOH
H-
0-
20
15
IODATE CONC.
\
25
I
I
/
/
/
I
/
(ug-P/1)
(ug-I/1)
'A
PHOSPHATE CONC.
/
/
I
I
I.
The study on the diurnal variations is also inconclusive although some trends have been observed. The problems
of the sampling site still exist. Moreover, the samples
were obtained in October when the biological activity was
probably low. Consequently, the change in iodate concentration was small. The experiment was performed on a very
cold, windy day. Wind stress might have brought deeper water
with higher iodate concentration to the surface. The tidal
effect might also have changed the iodate concentration.
Bad weather also prevented sampling at night. These disturbing factors caused by the tide and the wind again may
be avoided by doing better controlled experiments with a
tank. The phosphate data are just what one would expect f6r
a nutrient. Phosphate concentration is inversely proportional to the amount of biological activity and a decrease
in the concentration was observed in the daytime while high
concentration was observed in both mornings. The iodate
concentrations also changed but the variations observed in
this study cannot be easily explained by biological activity
alone.
-69-
C. The distribution of iodate in the Argentine Basin in the
South Atlantic
Samples were collected from the Geosecs cruise, leg.
5 (Nov. 4 to Nov. 28, 1972) at station 60 and 61 on Nov. 2223 and Nov. 24-25 respectively. Locations of the stations are
shown in figure IV-3. Samples were frozen in polyethylene
bottles. They arrived at the laboratory at Woods Hole on
December 5 and were analyzed for iodate immediately by the
titration method. The standard thiosulfate solution was
standardized just prior to the analysis. The iodate results
are summarized in table IV-3 and table IV-4. Other hydrographic data are listed in appendix 1 and appendix 2. They
were prepared by Broe5cer et al.(1972b).
The physical oceanography of the sampling locations
for stations 60 and 61 has been thoroughly studied (Fuglister
1960; Ewing et al.1971; LePichon et al.1971a, 1971b). Different water masses can be identified from the salinity, potential temperature, oxygen and nutrient profiles (figures
IV-4, IV-5, Iv-6, IV-7 and IV-8) of these stations using the
well-documented characteristics of the different water masses
in the world oceans (Defant 1961; Sverdrup et al.1942; von
Arx 1962). By comparing these published data with those
obtained from station 60 and 61, one can distinguish five
-70-
Figure IV-3. Cruise track of R/V Knorr, Geosecs Cruise,
Leg 5, and the locations of stations 60 and
61.
I
I
__________I
4.
-BR- - ;
?-B-A7Z--
L
20-
I''
i~Y
~7!
',
I
30
p
40*
TRACK -OF R*/V KNORR
GEOSECS
LEG 5
A LARGE VOLUME STATIONS
* REGULAR STATIONS
o STD STATIONS
* SPECIAL STATIONS
(SEE STATION LISTING)
Table IV-3. Nutrient data from Station 60.
Depth
m
I3uM
Ip
uM
P04-
NO 3 ~
uM
uM
uM
-2.4
0.09
0.0
-4.2
0.10
0.0
Iox
Iox
AOU
uM
103%
2
0.387
0.388
-0.001
0
65
0.392
0.394
-0.002
-1
126
0.448
0.441
0.007
2
18.1
0.25
2.1
244
0.448
0.434
0.014
3
33.8
0,,46
5.3
353
0.448
0.430
0.018
4
44.7
0.65
8.4
533
0.458
0.428
0.030
7
72.8
1.23
17.8
729
0.482
0.454
0.028
6
69.2
1.70
25.1
1036
0.482
0.442
0.040
8
97.6
2.02
30.2
1261
0.474
0.422
0.052
11
125.9
2.16
32.2
1483
0.474
0.415
0.059
12
144.2
2.17
32.4
1576
0.478
0.418
0.060
13
145.3
2.12
31.9
1723
0.458
0.400
0.058
13
140;.4
2.02
30.4
2270
0.459
0.421
0.038
8
91.6
1.46
22.6
2867
0.458 0.425
0.033
7
80.2
1.36
21.0
3212
0,465
0.431
0.034
7
84.0
1.40
21.7
3419
0.474
0.431
0.043
9
104.7
1.66
24.9
3725
0,471
0.419
0.052
11
127.4
2.00
29.6
4016
0.473
0.418
0.055
12
133.7
2.19
32.5
4197
0.475
0.421
0.054
11
132.9
2.22
32.4
-72-
Table IV-3. (continued)
Depth
03
m
um
uM
uM
4223
0.474
0.420
0.054
4238
o.478
4267
0.476
--- a
4297
0.474
---
4323
0.489
4346
0.474
4367
0.475
4388
0.495
4405
0.481
Ip
'p
-
Iox
Iox
I0'
11
AOU
NO 3 ~
uM
uM
uM
133.0
2.21
32.6
2.23
Preformed iodate.
Iox - Iodate of oxidative origin.
-73-
2.23
32.4
2.23
32.4
Table IV-4. Nutrient data for Station 61.
Depth
I03'
Ip
Iox
IO3-
Iox
uM
uM
uM
AOU
3
P0 4 ~ NO3 "
uM
uM
5
0.403
o.403
0.000
0
-o.4
0012
0.0
148
o.425
0.413
0.012
3
28.1
0.41
4.6
268
0.420
0.412
0.018
2
18.9
0041
4.4
426
0.451
0.432
0.019
4
45.7
0.81
10.7
535
0.422
0*410
0.012
3
28.3
0.78
10.2
596
0.451
0.432
0.019
4
46.4
1.13
15.7
692
0.466
0.441
0.025
5
60.9
1.61
22.9
792
0.471
0.447
0.024
5
59.2
1.68
24.7
996
0.485
0.454
0.031
6
75.6
1.87
27.9
1307
o.490
o.442
0.048
10
117.6
2.14
31.8
1386
0.498
o.446
0.052
10
127.1
2.14
32.6
1868
0.482
0.423
0.059
12
145.0
2.06
31.0
2346
0.471
0.426
0.045
10
109.1
1.64
25.0
2825
0.470
0.432
0.038
8
93.9
1.48
22.7
3165
0.485
0.437
0.038
10
118.2
1.74
26.2
3362
0.471
0.419
0.052
11
126.3
1.88
28.1
3496
0.478
3728
0.488
0.433
0.055
11
135.4
2.08
30.7
4096
0.475
0.419
0.056
12
135.8
2.18
32.2
-74-
Table IV-4. (continued)
Depth
03
m
um
4647
0.493
4704
0.486
4752
0.487
4804
0.486
4827
0.482
4844
0.475
4864
0.478
4883
0.477
4904
0.475
4924
0.508
4926
0.485
'p
IOx
Iox
AOU
P04 3~
N0 3 ~
uM
uM
2 21
32.6
2.21
32,6
03'
uM
0.439
um
0.054
u%4
11
132.8
----
0,454
0.054
Ip
- Preformed iodate.
Iox
-
132.4
Iodate of oxidative origin.
-75-
Figure IV-4. The nitrate, phosphate and silicate profiles
of station 60.
.
- Silicate.
x - Phosphate.
+ - Nitrate.
-760
0
50
100
10
20
3 NITRATE
x
44,t X
+
4
x
+
x
+
xx
C),
-
O
0X
0+
+
X
.
-
-X4
x
44
+
x
44
-
C-
uM
uM
PHOSPHATE uM
2
1
0
SILICATE
+
+
Figure IV-5. The oxygen, salinity and potential temperature
profiles of station 60 with the water masses
identified.
SACW - South Atlantic Central Water.
AAIW - Antarctic Intermediate Water.
NADW - North Atlantic Deep Water.
AABW - Antarctic Bottom Water.
.
-
Salinity.
x - Oxygen.
+ - Potential temperature.
-770
10
5
t
1
1
POTENTIAL TEMPERATURE
35.5
SACW
1*1+
+
AAI
+1
x
C>
C)
*
4
C)
CoI
CD
C4.
C)
+
0
C+ t
4I
AAB~l
0C
260 0.2 UiM
240
35.0
34.5
34.2
20
220
200
180
15
36.0 S%
Figure IV-6. The nitrate and phosphate profiles of station
61.
x - Phosphate.
+
-
Nitrate.
0
30
20
10
+
-783 PO 4~ uM
2
0
NO 3
t
+
4.
x+
K
x.
*
x~t
2
C4
+
+
*1
N
C-
C4
x
E-i
C1
c+
+
K
C
1-+
X
+
x
+
++
O
+
uM
Figure IV-7 and Figure IV-8.
The oxygen, salinity and potential temperature
profiles of station 61 with the water masses
identified.
SACW - South Atlantic Central Water.
AAIW - Antarctic Interediate Water.
NADW - North Atlantic Deep Water.
AABW - Antarctic Bottom Water.
-
Salinity.
x - Oxygen.
+ - Potential temperature.
15 POT.' TEMP.
oc
I
I1
I
I
200
180
240
220
260
I
02
UM
L
34.2
36.0
35.5
35.0
34.5
+'
S.A.
AA4.
0>
-x
NADW
x
I,
/
K
Ic
AA BWII
different water masses, namely, the surface water from 0 150 M., the South Atlantic Central Water from 150 - 600 m.,
the Antarctic Intermediate Water from 600 - 2000 m., the
North Atlantic Deep Water from 2000 - 4200 m., and the Antarctic Bottom Water from 4200 m. to the bottom.
The iodate profiles (figures IV-9 and IV-10) from
both stations have some common features. There is a significant depletion in the surface layer from 0 - 120 m., a
minor maximum between 200 - 500 m., a broad maximum from
1000 - 1800 m., and then a minimum from 2000 - 2800 m. From
then on, the iodate concentration fluctuates. However, there
is a trend of gradual increase until about a few hundred
meters from the bottom. The iodate concentrations close tt
the bottom fluctuate wildly. By matching the inflexion
points observed in the iodate profiles and those in the T-S
diagram,
it
can be seen that they do occur at roughly the
same depths. It is possible that iodate may be characteristic
of the different water masses. However, it would be unwise
to generalize such a proposal to the world oceans by two
profiles only. Much more data will be needed from various
oceans before such a proposal can be firmly established.
The nutrient-like behavior of iodate can be observed
when the iodate profiles are compared to those of the other
-80-
Figure IV-9. The iodate profile of station 60.
-81-
/ODATE
40
.35
2-
- GEOSECS
STATION
3-
4-
5-
60
(p
M)
.45
.50
Figure IV-10. The iodate profile of station 61.
-82-
/ODATE
0.35
0
0.4
(pM)
0.45
0.5
l
2-
GEOSECS
STATION 61
3-
4-
1
7
0
nutrients. In station 60, they all have a surface depletion,
a maximum around 1000m., followed by a mid-depth minimum and
then a gradual increase towards the bottom. Even the minor
changes in the other nutrients are reflected in the iodate
profile. The slight inflexion at about 160 m. in the phosphate, nitrate and silicate profiles is recorded as a jump
in the iodate profile. In station 61, a similar trend is
observed. The two minor maxima at the surface around 150 m.
and 450 m. in the other nutrients are much amplified in the
iodate profile. These observations show that iodate does
approximate the behavior of the other nutrients.
In order to study the nutrient-like behavior of
iodate in greater detail, calculations were made to see if
some kind of relationship similar to the Redfield ratios
exists between iodate and the other nutrients. Redfield
(1963) proposed that organisms assimilate nutrients at the
surface water, and, upon their death, they sink and the
nutrients are regenerated via oxidation by bacterial activity.
Consequently, the amount of oxygen used for this oxidation
process may have a stoichiometric relationship with the
other nutrients. Apparent oxygen utilization (AOU) has been
defined as: AOU = 02' - 02 (Richards 1965) where 02' is the
solubility of oxygen at the observed temperature and salinity
-83-
under an atmosphere saturated with water vapor and a total
pressure of 760 Torr. 02 is the observed oxygen content in
that sample of seawater. 02' can be derived from the data
published by Weiss (1970) and Green et al.(1967). The AOU
values calculated are shown in table IV-3 and table IV-4. A
number of investigators (Park 1967; Redfield et al.1963)
have shown that the nutrient parameters - phosphate, nitrate,
silicate and AOU - exhibit linear relationships. From these
graphs, the following equation is derived to describe the
process for the regeneration of.nutrients:
(CH2 0)l06(NH 3 ) 1 6 H3 PO4 + 13802 =
106c02 + 122H2 0 + 16HNO 3 + H3 PO
(Richards 1965b).
This model assumes that:- (1) seawater is saturated with
oxygen at the surface; (2) the average composition of organisms is constant so that the utilization of oxygen for the
regeneration of nitrogen and phosphorus compounds from the
tissues by bacteria takes place in statistically definite and
fixed ratio; (3) no oceanic mixing is taking place; (4) the
rates of regeneration of the nutrients are the same; and
(5)
either no uptake of nutrients is taking place, or else,
it must take place as the reverse reaction of the one proposed for the regeneration of the nutrients. Most of these
assumptions are at best approximate. Surface water may be
-84-
supersaturated or undersaturated with oxygen, and oceanic
mixing is definitely taking place. Riley (1951) and Grill et
al.(1964) suggested that phosphate may be preferentially
regenerated. Preferential uptake of nutrients may also occur.
Consequently, this model is only a crude approximation of the
real ocean and is used as an initial step towards the understanding of the nutrient cycle.
In this study, iodate is plotted against phosphate,
nitrate and AOU. The data from both stations are combined as
shown in figures IV-ll, IV-12 and IV-13. The lines are fitted
by a linear regression program from these data points. Some
of the data points from the surface water are omitted in the
computation because many of the assumptions of this model
are violated in the surface water. Vigorous mixing processes,
active nutrient uptake and penetration of oxygen from the
atmosphere are all occuring in the surface water to the extent
that the model is no longer valid. The solid lines on the
figures are all drawn from the slopes and intercepts given by
the program. The broken lines serves as demarcations for a 3%
deviation from the projected lines. The correlation coefficient of phosphate to iodate is 0.94 and the ratio of phosphate to iodate is 22,7:1. The correlation coefficient of
nitrate to iodate is 0.95 while nitrate : iodate = 357 : 1.
-85-
Figure IV-11. The relationship between phosphate and
iodate.
.
Data from station 60.
x
Data from station 61.
4
0
Cn
0S
XX
X
PHOSPHA TE
(,uM
Figure IV-12. The relationship between nitrate and iodate.
.
Data from station 60.
x
Data from station 61.
-87-
40
*/*
30
0/
/
14J
/
0/
20
k
/
10
x x
0
0.35
0.45
0.40
/ODAT
(
M)
0.50
Figure IV-13. The relationship between AOU and iodate.
.
Data from station 60.
x
Data from station 61.
150
..
0o0
/
/
50
/
7
7.
/
/
x
Xe
x
X
JX
/
0
0.35
0.40
/ODATE
045
(p M)
0.50
x
Lastly, the correlation coefficient of AOU to iodate is 0.88
and AOU:iodate = 2440:1. From these three ratios, AOU:
nitrateaphosphate = 108:16:1 which is close to the generally
accepted value of 138:16:1 (Richards 1965b).
The phosphate-iodate and nitrate-iodate plots have
higher correlation coefficients than the AOU-iodate plot.
This is probably due to the much higher uncertainties in the
AOU values. Phosphate and nitrate can all be determined by
standard methods directly to within 1-2% (Murphy et al.1962;
Morris et al.1963) while the AOU values are calculated from
the difference of two oxygen solubility values. This increase
in the amount of data manipulation will increase the uncertainties in the AOU values. Furthermore, some of the assumptions in the AOU concept mentioned earlier are probably not
met and this will also increase the uncertainties. Greater
precision
in the iodate and AOU values will be required for
better correlations between the two.
The data points from the surface water in the AOUiodate plot fall away from the projected line. It implies
that the preformed iodate is less than it should be. This
may be due to the reduction of iodate to iodide by bacteria
(Tsunogai et al,1969) giving rise to a net loss in iodate.
From the AOU-iodate ratio of 2440:1 obtained from
-89-
this study, iodate can be divided into its generic components - preformed iodate (Ip) and iodate of oxidative origin
(Iox). These results are also summarized in tables IV-3 and
IV-4, The amount of regenerated iodate is small throughout
the entire depth. It is usually around 10% of the total
iodate while the remaining 90% of the iodate is preformed,
implying that only a few percent of the iodate is recycled
in the sea.
One can also estimate the amount of regenerated iodate
from oxygen consumption data and using the currently accepted
oceanic circulation model (Broeiger 1961). Most numbers used
in this estimation are only approximate and may vary by a
factor of two to three, and, in addition to this, there ar'e
other assumptions made in this calculation. Thus, it can only
be regarded as a first approximation to the real situation.
To start with, one can try to follow the presently
accepted path of transport of a parcel of water from the
Noth Atlantic surface to the deep South Atlantic (Broeker et
al,1961; Broecker 1963). It is shown schematically in figure
IV-14. The parcel of water sinks at about 60N at the Greenland Sea and then travels southwards as the North Atlantic
Deep Water (NADW) and eventually reaches our point of observation at station 60 and station 61 at 300S.
-90-
Iodate is
Figure IV-14. Vertical profile through the western basin
of the Atlantic Ocean showing idealized
water-mass distribution.
SACW - South Atlantic Central Water.
AAIW - Antarctic Intermediate Water.
NADW - North Atlantic Deep Water.
AABW - Antarctic Bottom Water.
NACW - North Atlantic Central Water.
-91-
I
~-
I
(~#/wl/
ill
N4JJWI
448W
I
I
'ows
LA TI JDE
3oes
I
assimilated in the North Atlantic surface water by organisms
and as the water travels downwards and southwards, it ages
and the dead organisms are oxidized and consequently iodate
will be regenerated. Thus, there should be a gradual increase
in iodate concentration.
This process assumes that the parcel is a sealed
parcel of seawater so that there is no exchange with other
parcels of seawater by mixing. It further assumes that the
gradient of oxygen consumption with latitude is small. This
has been shown to be close to the real situation by Riley
(1951) in his study on the variations of the calculated rates
of oxygen consumption with latitude.
The oxygen consumption data were calculated using an
advection-diffusion model (Riley 1951; Wyrtki 1962; Craig
1971). The assumptions in this model are:- (1) the distribution of oxygen is constant with time which means that a
steady state has been reached; (2) the horizontal gradient of
oxygen concentrations is negligible relative to the vertical
gradient; and, (3) the ratio of the eddy diffusivity coefficient to the vertical advection velocity is constant with
depth.
In view of the large number of assumptions made, I
must emphasize again that the calculation can only produce
-92-
an.approximate picture of the real situation. The calculation
is shown below.
The oxygen comsumption data can be taken from the
average of the values reported by Craig (1971), Wyrtki (1962)
and Riley (1951).
Therefore,
oxygen consumption in the North Atlantic
Deep Water = 1.3 x 10~3 ml/l-yr
= 58
x 10-3 uM/kg-yr = AOU.
AOU:IO ~ = 2440:1 (from this work).
Iodate production is
2
0
uM/kg-yr = 2.38 x 10-5 um/kg-yr.
Assuming that the average of the surface iodate concentrations in stations 60 and 61 of this work is similar to the
iodate concentration in the North Atlantic surface water
(therefore, surface iodate concentration = 0.395 uM), and
that the residence time of the North Atlantic Deep Water is
about 570 years (Craig 1971), then, the percent increase in
iodate (that is, the amount of regenerated iodate) in the
North Atlantic Deep Water can be calculated to be:
Iox
_
-Itotal
2.28 x 10-5 x 570
x 100%
0.395 + (2.38 x 10-5 x 570
0.395
0
-93-
- 3%.
This result can be compared to what was observed in stations
60 and 61. Stations 60 and 61 were located at around 30 0S
in the Atlantic. North Atlantic Deep Water had been identified earlier in this discussion from T-S diagrams and it
was located at about 2000 to 3000 meters. Iodate of oxidative
origin (Io ) has also been calculated.
In station 60, at 2867 m.,
Iox
OX
=
0.033
0.458
Itotal
x 100 % = 7%.
In station 61, at 2825 m.,
I____
'ox
,total
=
0.038
0.470
x 100 % = 8%.
These results agree well with the circulation model proposed
(Broeer et al.1961; Broeer 1963) and similar observations
on nitrate and phosphate (Broedker 1971; BroE5er et al.1972a,
1972b; Spencer et al 1972a, 1972b; Craig et al 1972). A water
parcel in the North Atlantic surface water has relatively
low iodate content with negligible amount of regenerated
iodate. As it sinks and travels towards the South Atlantic,
the regenerated iodate content increases. The discrepancy
between the observed and the calculated values is probably
due to the deviations from the assumptions in this calculation.
-94-
The mechanism for the uptake of iodine by marine
organisms is still largely unknown. Literature (Shaw 1962)
gives a very confusing picture. It is possible that organisms
take up iodate because it has a structure similar to nitrate.
This failure of some organisms to distinguish between similar
chemical species has been reported in the arsenate-phosphate
pair (Harvey 1960). Arsenate has been found to take the place
of a portion of the phosphate required for growth by the
fresh-water algae Stichococcus flaccidus (Comere 1909). At
the same time, as mentioned earlier, bacteria that are
capable of reducing nitrate can take in iodate and reduce it
to iodide. A large number of algae have the ability to reduce
nitrate using the enzyme nitrate-reductase. So, it is possible
that these algae may assimilate iodate too.
The average surface iodate concentration in the open
ocean in the South Atlantic is about 0.395 uM while the
surface iodate concentration in the Woods Hole coastal water
is only around 0.2 uM. This difference may be due to the
difference in the amount of biological activity if iodide
is produced from the reduction of iodate by bacteria. Coastal
waters have higher biological activity, hence, more iodate
is being converted to iodide. This is also reflected in the
high iodide concentrations observed. The total iodine con-
-95-
centration in coastal waters is about 0.4 uMv.
This is the
amount that was observed in the open Pacific (Tsunogai
1971b). Thus, the difference in the iodate concentration
between the open ocean waters and the coastal waters should
probably just reflect thke difference in the amount of biological activity rather than a gross depletion of iodine
close to the shore.
-96-
CHAPTER
V
CONCLUSION
From the various studies that have been undertaken,
the new analytical technique for iodate has been shown to
be suitable for fast routine analysis of iodate. The analytical method is self-consistent. The addition method has a
coefficient of variation of 2.7% while the titration method
is precise to within 1%. The comparative study of these
methods with the co-precipitation method shows that they
agree to within experimental uncertainties. The storage
experiments show that seawater can be stored at low temperature for up to a month without significant change in its
iodate content.
The study on the distribution of iodate in the
ocean shows that the iodate concentration is significantly
lower in the surface coastal waters than in the surface
water in the open ocean probably as a result of higher biological activity. A depletion of iodate in the surface water
of the ocean was also observed. This has been observed by
Tsunogai et al. (1971b) in the Pacific. The iodate profiles
and the profiles of the other nutrients - phosphate and
nitrate - all have similar features. The Redfield-type
-97-
ratios derived from the iodate data are AOU:NO 3 :P0 4 3 - :103
= 2440:357:22.7:1 or AOU:NO3~:P0 4 3- = 108:16:1. This agrees
well with the established ratio of AOU:N:P = 138:l6:1
(Richards 1965b). The amount of recycled iodate is small. It
amounts to about 10f of the total iodate. From the simple
model calculation, it is shown that the iodate of oxidative
origin increases as the water mass becomes older and moves
away from the surface where biological activity is high. These
observations agree with the theory (Tsunogai et al.1969) that
the reduction of iodate is caused by biological activity and
that iodate exhibits nutrient-like behaviors.
-98-
CHAPTER
VI
FUTURE WORK
The diurnal and seasonal variations studies are
inconclusive and will have to be repeated in a more favorable
season and under better controlled experimental conditions.
The use of a tank as previously suggested may be one way to
overcome the existing problems.
The analytical method for the analysis of iodide has
not been successfully developed yet. A rapid and precise
analytical technique will be necessary in order to use iodide
as a tracer.
The iodide concentration has been observed to increase
towards the water-sediment interface by Tsunogai (1971b) and
he proposed that iodide may be diffusing from the sediment
into the ocean. More data will be needed in order to confirm
this observation. In conjunction to this project, kinetic
data for the iodide-iodate couple will also be needed for a
better understanding of the redox chemistry of this couple in
seawater. If all these data are available, models may be set
up to use iodide as a tracer to study the importance of the
sediment-seawater exchange processes.
In an anoxic basin, pH = 7.6 and pE = -4 (Spencer et
-99-
al.1971) assuming that pE is poised by the couple
S04 2
+ 9H+ + 8e~ = HS
+ 4H 2 0.
For the iodate-iodide couple,
= 6pH + 6pE
log
Then, [I031
-
logK.
-88.5
[I-]
This means that if thermodynamic equilibrium is reached,
iodine should be present solely as iodide in an anoxic basin.
Thus far, there is no data on iodine in anoxic basins to
confirm this hypothesis. If iodine is present in the form of
iodide in anoxic waters, it may be used as a tracer to study
the rates of exchange between anoxic water and aerated water.
This exchange may be an outflow from an anoxic basin or an
upward advection of anoxic water in polluted estuaries. The
penetration of anoxic water into aerated water may lead to
changes in the nutrient budget which may affect marine life.
The techniques for the analysis of iodate and iodide
in anoxic water will also have to be developed since the
theoretically interfering species shown in table 11-3 may
become significant in anoxic water.
The large excess of iodine in the marine atmosphere
has been known for some time (Duce et al.1963, 1965; Moyers
-100-
et al.1972) and has been attributed to the photo-oxidation
of iodide (Miyake et al.1963). With the present analytical
techniques available, it will be possible to study the proposed process quantitatively. The photochemistry in the sea,
other than photosynthesis, has been largely ignored and this
study can serve as an initial step towards a better understanding on the importance of this kind of chemistry in the
sea.
-101-
REFERENCES
Barkley, R. A. and T. G. Thompson (1960a). Determination of
chemically combined iodine in sea water by amperometric and catalytic methods. Anal. Chem., 32,
154.
Barkley, R. A. and T. G. Thompson (1960b). The total iodine
and iodate-iodine content of sea-water. Deep-Sea
Res., y, 24.
Bjerrum, J., G. Schwarzenbach and L. G. Sillen (1958).
'Stability Constants, Part II (Inorganic Ligands)'.
Chem. Soc. Spec. Publ. 7.
Boston Globe (1972). Sept. 15 - Sept. 29.
Bowen, H. J. M. (1966). 'Trace Elements in Biochemistry'.
Academic Press, New York.
Broe cer, W. S., R. D. Gerard, M. Ewing and B. C. Heezen
(1961). Geochemistry and physics of ocean circulation. Ins'Oceanography', (Sears, ed.). AAAS.
Broecer, W. (1963). Radioisotopes and large scale oceanic
mixing. In: 'The Sea', (Hill, ed.), 2. Intersci.
Publ., New York.
Bro
er, W. S. (1971). A kinetic model for the chemical
composition of sea water. Quarternary Res., 1, 188.
Broecer, W. S., A. E. Bainbridge and P. M. Kroopnick (1972a).
Geosecs preliminary report, Leg 3, Reykjavik to
Bridgetown, Sept.4 - Oct. 1, 1972. Scripps Inst.
Oceanogr.
Bro, er, W. S., T. Takahashi and A. W. Mantyla (1972b).
Geosecs preliminary report, Leg 5, Recife to Buenos
Aires, Nov. 4 - Nov. 28, 1972. Scripps Inst. Oceanogr.
Comere, J. (1909). Action of arsenate on the growth of algae.
Bull. Soc. Bot. Fr., d6, 147.
Cotton, F. A. and G. Wilkinson (1962). 'Advanced Inorganic
Chemistry'. J. Wiley Sons, New York.
-102-
Courtois, B. (1813). Decouverte d'ure substance nouvelle
(iode) das vareck. Ann. Chim. (Phys.) 1, 88, 304.
Craig, H. (1971). The deep metabolism : oxygen consumption
in abyssal ocean water. J. Geophys. Res., 76, 5078.
Craig, H., K. Park and R. Weiss (1972). Geosecs preliminary
report, Leg 4, Bridgetown to Recife, Oct. 9 - Oct.
31, 1972. Scripps Inst. Oceanogr.
Defant, A. (1961). 'Physical Oceanography', 1. Pergamon
Press, New York.
Douglas, B. E. and D. H. McDaniel (1965). 'Concepts and
Models of Inorganic Chemistry'. Ginn Co., Waltham.
Dubravcic, M. (1955). Determination of iodine in natural
waters. Analyst, 80, 295.
Duce, R. A., J. T. Wasson, J. W. Winchester and F. Burns
(1963). Atmospheric iodine, bromine and chlorine.
J. Geophys. Res., 68, 3943.
Duce, R. A., J. W. Winchester and T. W. Van Nahl (1965).
Iodine, bromine and chlorine in the Hawaiian marine
atmosphere. J. Geophys. Res., L0, 1775.
Ewing, M., S. L. Eittriem, J. I. Ewing and X. Le Pichon (1971).
Sediment transport and distribution in the Argentine
Basin. 3. Nepheloid layers and processes of sedimentation, Phys, Chem. Earth, 8, 49.
Fuglister, F. C. (1960). Atlantic Ocean atlas of temperature
and salinity profiles and data from the International
Geophysical Year of 1957 - 1958. Woods Hole Oceanogr.
Inst.
Goldberg, E. D. (1963). The ocean as a chemical system. In :
'The Sea', 2. Intersci. Publ., New York.
Green, E. J. and D. E. Carritt (1967). New table for oxygen
saturation of seawater. J. Mar. Res., 2j, 140.
Grill, E. V. and F. A. Richards (1964). Nutrient regeneration
from phytoplankton decomposing in sea water. J. Mar.
Res., 22, 51.
Gross, J. (1962). Iodine and bromine. In : 'Mineral Metabolism,
-103-
An Advance Treatise', (Comar and Bronner, ed.).
Academic Press, New York.
Hanson, W. C. (1963). Iodine in the environment. In : 'Radioecology', (Schultz and Klement, ed.). Rheinhold.
Harvey, H. W. (1960). 'The Chemistry and Fertility of Sea
Waters'. Cambridge Uni. Press, Lond.on.
Jacobson, C. A. (1949). 'Encyclopedia of Chemical Reactions',
1 - 1. Rheinhold, New York.
Johannesson, J. K. (1958). Oxidized iodine in seawater. Nature,
182, 251.
Johnson, D. L. and M. E. Q. Pilson (1972). Arsenate in the
Weatern North Atlantic and adjacent regions. J. Mar.
Res., .20, 1.
Kappanna, A. N., G. T. Gadre, H'. M. Bhavnagary and J. M. Joshi
(1962). Minor constituents of Indian sea-water. Curr.
Sci., 31, 273.
Kolehmeinen, S.,S. Takatolo and J. K. Miettinen (1969). A
tracer experiment with 1-131 in an oligotrophic l'ake.
In : 'Symposium in Radioecology', (Nelson and Evan,
ed.). USAEC, Oak Ridge.
Kolthoff, I. M., E. B. Sandell, E. J. Meehan and S. Bruckenstein (1969). 'Quantitative Chemical Analysis'.
Macmillan Co., Toronto.
Kuenzler, E. J. (1969). Elimination of iodine, cobalt, iron
and zinc by marine zooplankton. In : 'Symposium in
Radioecology', (Nelson and Evan, ed.). USAEC, Oak
Ridge.
Langer, P. (1960). History of goitre. In t 'Epidemic Goitre'.
World Health Organization Tongr., 44, 9.
Le Pichon, X., S. L. Eittreim and W. J. Ludwig (1971a).Sediment
transport and distribution in the Argentine Basin.
1. Atlantic bottoa current passage through the Falkland Fracture Zone. Phys. Chem. Earth, 8, 1.
Le Pichon, X., M. Ewing and M. Truchay (1971b). Sediment
transport and distribution in the Argentine Basin.
2. Antarctic bottom current passage into the Brazilian
Basin. Phys. Chem. Earth, 8, 29.
Liss, P. (1972).
Private comm.
Macadam, S. (1852). Chem. Gaz., 10, 281.
Marchand, E. (1855).
Mem. Acad. Med.
Paris, 19, 121,
Matthews, A. D. and J. P. Riley (1970). A study of Sugawara's
method for determination of iodine in seawater. Anal.
Chim. Acta, 31, 295.
Millero, F. J. (1971). The molal volumes of electrolytes.
Chem. Rev., 1, 147.
Miyake, Y. and S. Tsunogai (1963). Evaporation of iodine from
the ocean. J. Geophys. Res., 68, 3989.
Morris, A. W. and J. P. Riley (1963). The determination of
nitrate in sea water. Anal. Chim. Acta, 2L, 272.
Moyers, J. L. and R. A. Duce (1972). Gaseous and particulate
iodine in the marine atmosphere. J. Geophys. Res.,
71, 5229.
Murphy, J. and J. P. Riley (1962). A modified single solution
method for the determination of phosphate in natural
waters. Anal. Chim. Acta, 27, 31.
Nightingale, E. R. (1960). Role of multiple bonding in electron transfer reactions. J. Phys. Chem., 6_, 162.
Park. K. (1967). Nutrient regeneration and preformed nutrients
off Oregon. Limnol. Oceanogr., 12, 353.
Rankama, K. and T. G. Sahama (1950).
Chicago Press, Chicago.
'Geochemistry'. Uni.
Redfield, A. C., B. H. Ketchum and F. A. Richards (1963). The
influence of organisms on the composition of seawater.
In:.'The Sea', (Hill, ed.), 2. Intersci. Publ., New
York.
Reith, J, F. (1930). Der Jogdehalt von Meerwasser. Rec. Trav.
Chim. Pays-Bar., 42, 142.
Richards, F. A. (1965a). Dissolved gases other than carbon
dioxide. In : 'Chemical Oceanography', (Riley and
-105-
Skirrow, ed.), 1. Academic Press, New york.
Richards, F. A. (1965b). Anoxic basins and fjords. In :
'Chemical Oceanography', (Riley and Skirrow, ed.),
1, 611. Academic Press, New York.
Riley, G. A. (1951). Oxygen, phosphate and nitrate in the
Atlantic Ocean. Bull. Bing. Oceanogr. Bull., XIII, 1.
Riley, J. P. (1965a). Historical introduction. In : 'Chemical
Oceanography', (Riley and Skirrow, ed.), 1, 1.
Academic Press, New York.
Riley, J..P. (1965). Analytical chemistry of sea water. In :
'Chemical Oceanography', (Riley and Skirrow, ed.), 2,
,
295. Academic Press, New York.
Riley, J. P. and R. Chester (1971). 'Introduction to Marine
Chemistry'. Academic Press, New York.
Schnepfe, M. N. (1972). Determination of total iodine and
iodate in sea water and in various evaporites. Anal.
Chim. Acta, 58, 83.
Shaw, T. I. and L. H. N. Cooper (1957). The state of iodine
in seawater. Nature, 180, 250.
Shaw, T. I. and L. H. N. Cooper (1958). Oxidized iodine in
seawater. Nature, 182, 251.
Shaw, T. I. (1962). Halogens. In : 'Physiology and Biochemistry of Algae', (Lewin, ed.). Academic Press, New
York.
Sillen, L. G. (1961). The physical chemistry of seawater. In :
'Oceanography', (Sears, ed.). AAAS.
Skopintsev, B. A. and L. A. Michailovskaya (1933). Iodine
content of White Sea water. Trud. Inst. Oceanogr.
Moscow, 3,
79.
Spencer, D. W. and P. G. Brewer (1971). Vertical advection
diffusion and redox potentials as controls on the
distribution of manganese and other trace metals
dissolved in waters of the Black Sea, J. Geophys. Res.,
26,
5877.
Spencer, D. W., A. E. Bainbridge and J. M. Edmond (1972a).
-106-
Geosecs preliminary report, Leg. 1, Woods Hole to
Reykjavik, July 18 - Aug. 7, 1972. Scripps Inst.
Oceanogr.
Spencer, D. W., J. M. Edmond and R. F. Weiss (1972b). Geosecs
preliminary report, Leg 2, Reykjavik to Reykjavik,
Aug. 12 - Aug. 30, 1972. Scripps Inst. Oceanogr.
Sugawara, K. (1957). The distribution of some minor bioelements in Western Pacific waters. In : 'Proc.
Regional Symp. Phys. Oceanogr., Tokyo, 1955'. UNESCO.
Sugawara, K., T. Kayama and K. Terada (1955). A new method
of spectrophotometric determination of iodine in
natural water. Bull.Chem. Soc., Japan, 28, 494.
Sugawara, K. and K. Terada (1957). Iodine distribution in the
Western Pacific Ocean. J. Earth Sci., $, 81.
Sugawara, K. and K. Terada (1958). Oxidized iodine in seawater. Naturejl82, 250.
Sugawara, K., K. Terada, S. Kanamori, N. Kanamori and S.
Okabe (1962). On different distribution of calcium,
strontium, iodine, arsenic and molybdenum in the
Northwestern Pacific, Indian and Antarctic Oceans'
J. Earth.Sci., 10, 24.
Sverdrup, H. U., M. W. Johnson and R. H. Fleming (1942).
'The Oceans, Their Physics, Chemistry and General
Biology'. Prentice-Hall, Inc., New Jersey.
Tsunogai, S. and T. Sase (1969). Formation of iodide-iodine
in the ocean. Deep-Sea Res., 16, 489.
Tsunogai, S. (1971a). Determination of iodine in seawater by
an improved Sugawara method. Anal. Chim. Acta, 55,
444.
Tsunogai, S. (1971b). Iodine in the deep water of the ocean.
Deep-Sea Res., 18, 913.
Tsunogai, S. and T. Henmi (1971). Iodine in the surface water
of the ocean. J. Ocean. Soc. Jap., 2Z, 67.
Vinogradov, A. D. (1953). 'The Elementary Composition of
Marine Organisms'. Sears Found. Mar. Red., Yale Uni.,
New Haven.
-107-
Voipio, A. (1961). The iodine content of Barents Sea water.
Rapp. Cons. Explor. Mer., 149, 38.
Von Arx, W. S. (1962).'An Introduction to Physical Oceanography'. Addison-Wesley Publ. Co., Mass.
Wada, E. and A. Hattori (1972). Nitrate distribution and
nitrate reduction in deep sea waters. Deep- Sea Res.,
12,
123.
Weiss, R. F. (1970). The solubility of nitrogen, oxygen and
argon in water and seawater. Deep-Sea Res., 17, 721.
Whittaker, E. J. W. and R. Muntus (1970). Ionic radii for
use in geochemistry. Geochim. et Cosmochim. Acta,
31, 945.
Winkler, L. H. (1916). De Jodid- und Jodate- iongehalt des
Meereswassers. Z. Angew. Chim., 29, 205.
Wyrtki, K. (1962). The oxygen minima in relation to oceanic
circulation. Deep-Sea Res., 2, 11.
-108-
Appendix 1. Hydrographic data of station 60.
0"
Xz
O C
0U
> SVv
>N
D
Q
(V
.
eV
Q.
NO
M
tn
9-
%0
0
C
0
t.
Je4
a.J U)
C
(
N#
^ *
)
O (NJ
: ca
4O
0 .
) 0 0 co
(V0DC.-4
(N
C:
O
V
..
3
V (V.
D
0'
D(
N
3C4
t-( k
0.
(V
4
CO C)
n
0.4
C
v ^m
N
O
)
4
C%
"N
OnD
ene)W)
co
4 00
C2 k D -
P-
J'.4
co
0
-
4r) a3
ci
N
(V C)
3-.4
InIt-t--)
'
O
N) C)
.
Nre
.
t-
o
-D
-
-
I)t)e)--')W
K)4.
-0&
(VNNNV(V
CD -4 'A
00.4.4
C 0
30.C)% fN )
N) N(V(
c-i
(j (Vj " (V (V
f
N
CZ) D (
.
e
N l
C%0O
.4 .4
3re&. -
C3
0
3
PO
fo4
...
-
'
(V
.
U-
\
CIN
9
W
5) O
0'
'
W
K
to Lr
N
(V
r
e4
r
C%
N
Iu(V
O4
D(IN 1 VI0000
IU
<
n n
CD
N(
(VC4N
rvN"'D-4
no
o-
e43-
-e)
.
'D
(VN'O
N
co C,
(VcVVcVN
A
A
)
'A41.-I
~003-Jr
ODU)4)%-"-r---
'J-
rO
...
:2 tK)
co
-I
3
90
f3
40%
e
90In
4-4
90
t-in
O2#
4fl.42 0- 3-
-4 -4
fn W) In CO 0%
4)N
r1N)
N
0
) 0
N
c
i1
4)..
4 0
(V (V
0
r- CDc0 o >
N
M0
0
4
D
N)
ID %
3
(V cu Co. N (
Co0%
V %b
O
C C0
4
C
'
(VO I-
C(D )1
it
N
aiko In ')
.N)
to to N)lN
(V cv (V (V (V
0'
0
0 r
j (VK)
co
to
.4 ....
1c
0
0.
CO
0,
d)
%D
N
e
O\
20
CO
ve
*
*
*
4
K)
fq
%
0-4
*c *
. .
W) N
(V
.
en
0
3-3
a
3C re) _4 CA I
OQ
CU
CY 0 Co
0N
NC
o
3V r- c-
o0
C)
0Z
-C
0.43-4
0C
.N)
.4.1-
,o Ln %o cv fu
cl
0 f
)
fn 4T r-
01 Ors Ln %D
O
SC) - . to
eN)03O)
N
N% to
N
If
.4 4C
C0C%
%0 QD %0
4"4W4
W4
40
.3.
D N 3D 4)
(N -4 N) "N)
4 )4
N ) N e)f)Na-
(I
N 04 (V(
C
o
.
r
.4
CN
4
-a
.
N)
v
4
4"-4 -4 -4
(VN( (V (V (V
a%0
-
D n
d)
.
-4-4
IN
-O)
(le 4
.
(N
i NN
7
)
4
3 14-
C4 Z e)')N))"
4
4
,A
u- 4)
.4
tY
to
CJ1- "
EV
V(
i
V(N
M
(V
V N) (
)
%3 D .0D
%DIr4
D
O4q
v i 0
"4 V4 -4 -q 44
D
en
%
&
0i:4)0
(V
t-
oC>0.4.4
0
(
.
0C0
-a%
'A
I- .4 0
0 '-k
' C)
(IVoN (V r- ru- r c)
e~-.Y
-1
~QC-
O
~
.
fnco %Dca a
.
4)0 00 '0
,4 Ca %D 0
a% 4) 6(D r4
0' (O0
O
N
4(V0 %
to
P
C%
al M
l.
o 0
e
(V
N. ) 4n
(V (V (V ( (V
- .. q
0 -Z I- CtrW
0
) o)
PO -' kol.~ 4eY
0%ul N
.
C :1, -.
.
t-
N
N)"cN
CD co a,
N a
0000
CD
.)
10 N)
(VNV V
0.-. .11-03-01-
0
23-33
3
"D PCNl
C-DC_ C;c Cr- (V t- 90 N) N)
1- 7' 0.41-w
000(O
e4
00 1 .4O
. .404)
.40.
.4 0
.4OQOO
4 -4
0
C0
'30
c roN V%;cMa coCDco co
a, 1-
c- 3- Cm 3, 30o %D%
g 0c r
O10 PO
C43 .4-13- 1- c.4
)
CD
~
o
~
00
4cvC"
O
0O .40
.
N) (V
v -4
N
0
Ntn
vccu re
03
"
W) 1 -
tN
N
4
. .4.4
V
e)
e4
N) mt-a,
L40-
Z D0
V4
W4
"4 co
_r K) kD to Wo e-I O _r %D t0
4 Ij
p10 :: r0
- (VN
-10D4.4
N
r)O r - 4r Q
C N Z U =
cO N "I Z n
44 4 . - -4
N N N
N N
K PC) to
NNNNCV
.- 1-1
(V (V
1-01-1-
-N) N
inW)
(V cmto
3-3N
N) No
\D .4
N) 3
C
N
r10
C NN N
0 CD -4
4
9N30
CD %
; ;0.4
c
NNV
.4e
n 4
.C1
.4
D
-4
4t a,494-4
a,a*q4 4 o
en
4
C %D
-109-0
%D%0
=
~
.
N I,
N ( V N- )
-444 00 ) Z V)-K)
r-
) _r
C% 4 (V
cN
v N (V
to
(V (V
c
-W)II nN)(V
to '30
-nT =
N) N) (.
C
N) N) N 3- 3a%
On0.
ON-
N
4 fy
t
0-
O
(V'3
~~ 0W)4
~
q
-4nt
N
..
f-7' 3- (V
:2. (V .4
.
N c) N C) o
) PC K)r)c
tt
e
C
.n
C%
r- to . 4
3.4
311-4
r. "
.0
N u
(V
_r.e
.1 - 43- o3-J
&C~l I-
D
O
D
.v to4)01. .
.
00
CY e
(V r- 0. 4.-4
'4in o) ' 3
N i (
N 7V-4 -4-4
tOtO) N-) K)
e-l) N V) " Nr
NNjV
N4 (N N VV( N
1V
c
03-00
0 CN 'i cN
(V(V((V
NV NeCru(V
N
N(Vcrj
3"
z
,D
.
e
.
N t-4
3
N
r-r-
.4.
hl
.
0
r0
7%
lN:00N
N N r-
4
z
".4.4"
01 p- 0
rN) cLnt
N o4)
KO N)
.
-:
O
-
V3-\V0N)
"n
N
t
.)
(VN)K)
--
D
LO n
14
0
i--
C>.
in
.1-
Ot
s
(4 (V (V (
CO zi
-4 (V N )
0301
N).ej\
0.41
.4'
04)
z (V0
,
4
) 0.4
n C%
.)
NNNNN
0r
C: rer
(v (VJ N1 (V-)
co a1) C'
(V -(
4 1- 0.4
Nco-
..
O
4
.
N
(V (V
en -
K) N)
.- v 1-0
(V C) (V 0
(V (Vj f
10
.
W)
En
p
00o C% q .
co Z"
*
0
c
3
0 0 to
-q
f) N
NV
%O "
NN
O-
toi
.
to -IN) ) 3- 3.4 (V
03
.
N' '3 Nto to
00e4
.. 4.
. (V
a, 3l- W) .001-0't 0.4
(V IY (V N) N)
0D-0'
C%
cc1 a 0 a
C
co e4 LO
(V
C%
*
eon to
O N w ko )
V)
n O
z3 a- 10 % CDV4iLO
...
C%
9to
cD
44)3-e
- O3-1
.40'
304)
'34) 4
.4.4.O
(V
.N
\00
'34)
(V
0 V . r4"4.-4 .4
%0D %U %D 10
-4
D
P It t
1 10
r
cr(a-
N
co
%D %DW) -r "
4
0D
fV0u'3D%
_
D
It.2 t&
%D Z
.
'0 3.3f- 1-t
-r inrLo \or
N) "V-40
0,c
(v C v (V (V
K) 0 .
0 o
N0
.4 T4 .1
.4 0N)
L-%.4 t14
.-N
e1)
3ID I- P- a~ -N) !v fu NW) N
a,1 - Ln)
v,.
q= cNM o
C) to K)
n
tN)
'n : 1- 3>
0
3 . .4 .
N) N) N) N) N
3 N) N)4)N N)"0\O (V CO
%.a
N
13 eN)
N)).4
.1-N
en Cto
o ZI, O
zr
a%
-r
a%
W-) N(VOIDC,
0'
-41C(\o %D
An CD 00%cu
Ln CDfC%
o
1 n
.
.
.4) c;
-4n
q4 _rCw
cyO
CD -4eD in~
%
.
3l r- 3.
-rt
3-011
4
'o 0
i-
to
(V -D ro -r CV
0.4 'VN)
NNNNN
%4n00
to %D
o .
..
4
(VNr)
k -0
o r
_
.-A .4-1NI)C e . .e
(V (V (V (V (Vi
i3-' :I,
) N
0
(l PO .2C3 O O3
0 0
N) C)
fcj (V1 (V -V (Vi
103D
c N4 N) 1- 1DI a r U' ID
)
(
-D
NNNNN c~ (V (V
Li cot
Z. *
O
U
-
x
0e
C
K0:001-0
NNNN
e
N
-4r-
" 44n j
-r C' _0
C>
V
Ov
%
N0c
kf D
V (v N
1%
D-
0
e e
000OO00
CO00.ed.4
C
e
0 00
C)
N
Sa'
N
CI CD
NNN
Z3
S
SN
0
-
Li
0
<n
(-V
LoI
C-
On-:ID
;tn
0W
V)
OD
43
OD
-4
%D4
O4
4)0
f- D
O
tt n
N
1-7%Q Z, %D
2
r- t- 0 Z, 0S4- (V 3-\ 0c
0(V
4 cu
U.7LiC 0% a' 4 W ) 01.-10
0 .
. . .
" m3 . .
.*
In 'n .0 0 -n
C,-
K) )
Itn T) In
)
LO
a' en D .4
- 0
-YC)
0 0 0
0
_E N
<
0
Q
Q.
Li
enU N
o
0
t
X 04&)3-
..
4.,
.:1
ui CD C5 C5 C3 C
:D
Li L...~itoa
0
C3
-r
(
CP
-
DATA' REPORT
H/V Kf'ORR
POsItION 32 31.05
STATION
-CAST
60
1
60
0
60
1
60
60
8
8
60
8
60
60
60
60
60
8
1
60
60
42
UTTLE DEPTH
M
NUPBER
21 4125
16 4197
22 4223
17 4238
18 4267
19 4297
GEOSECS IEG V
FIRST CAST 1330
22 NOV 72
0.0W
TEMP
DEG C
0.1v1
00125
0.130
0.113
0.105
06102
POT TEMP SALINITY SIGMA
DLG C
THETA
0/00
-0.120 34.672
27.076
-0.102 34,669 27.076
-0.100 34.670
27.877
-0.198 34.667
27.875
-0.209 34.672
27.OO
-0,215 34,669 27.870
4323
4324
4346
4367
4308
0.099
-0,221 34.666
8
8
20
23
21
22
23
0.101
0.102
-0.219
-0.220
8
1
24
24
4405
4414
8
SIGMA
z
46.971
47.299
47.412
47.482
47.617
47*745
SIGMA
4
46.130
46.130
46.138
46.139
46.144
46.143
0.1,03
0.106
27.876
27.077
27.870
27.878
27.876
47.860
47. 8b6
34.669
-0.222 34.669
-0.221 34.666
48.057
48.149
46.142
46-.143
46.144
46.144
46.142
0.109
0.111
-0.220 34,671
-0.219 34,667
27.080
27.876
40.226
48.261
46.145
46.142
*********
34.668
47.966
STATION
NIS
DEPIH 4424
OXYGEN
SIL
P04
UM/KG UM/KG UM/KG
225
122.6
2.20
226
2.22
126.3
226
124.1
2.21
60(CONT)
CORR.M
-1403 ALK(T) C02(T) CO2(6C)PRESS
UM/KG
U EQ/KG UM/KG
UIM/KG 0.13AR
2357
2234
32.35
2253
4194
32.44
4268
2356
32.64
2244
2237
42J4
431u
4340
4370
226
127.2.
125.4
2.23
2.21
4397
32.44
32.74
2355
2248
2247
4398
4421
4442
44b4
225
126.5
125,4
2.23
2.21
PRELIMINARY DATA ONLY.....NOT FOR PUBLICATION**********
32,44
32.64
2357
17
2241
DEC
2246
72
4481
4490
PAGE
2
Appendix 2. Hydrographic data of station 61,
DATA
R/V KNIORR
POSITION
36 0.0S
45
SIGMA
2
26.093
26.308
26.736
27.139
27,346
STGMA OXYGEN
SIL
P04
NO3
4
UM/KG UP/KG UM/KG UM /KG
42.752
0 .00
241
0.12
1.1
240
42.047
0.11
0.00
1.1
43.129 226
1.4 0.30
2.83
43.326 224
4.68
1.7 0.41
229
1.7
43.369
0.40
4.10
27.537
27.748
27,909
28.243
20.641
43.404
235
143.424
43. 4 64
12.040 35.140
26.541
26.553
26.577
26,616
26,725
235
i28
215
224
6
7
n
9
10
224
260
317
363
426
14,900
14.600
14.327
13.365
12.106
14.865 35.661
14,758 35.646
14,278 35.540
61
5
61
61
61
61
5
5
5
5
11
12
15
16
17
405
535
596
647
692
12.181
11.612
12.114
11.540
9.223
7.009
6.202
35.242
35.13,
34.720
34.433
34.336
26.791
2u.817
26.903
27.012
27,043
23.972
29.226
29.618
29.990
30.244
43.867
43.941
44.227
61
61
61
61
61
5
5
5
5
5
18
746
19
20
21
22
5.240
792
847
894
996
34.246
34.249
34.254
34.232
34.224
27.097
27.132
27.162
27.101
27.229
30.563
30,818
31.105
31.350
31.802
44.003
44.866
4.385
3.C55
5.176
4.889
4.648
4.313
3,779
23
24
1
2
3
1145
1307
1306
1533
1700
3.439
2.913
2.776
2.671
2.764
3.354
2.819
2.677
2.561
2.637
34.265
34,325
34.364
34.457
34.572
27.302
2 1.398
27.441
27.525
27.610
4
5
6
7
8
18661
2020
21A6
2346
2504
2.832
2.077
2.899
2.690 34.655
2.719 34.720
3.01b
2,939
2.824 34.044
2.733 34.850
27.672
27.720
27.766'
27,011
27.030
36.369
37.153
37.905
38.660
39.406
45.703
45.737
45.765
9
10
11
12
15
2665
2825
2921
3165
3362
2,010
2.750
2.655
2.117
1.697
2.590
2.522
2.405
1.861
1.431
27.849
27.069
27.881
27,665
27,065
40,159
40.901
41.619
42.474
43,398
45.798 234
45.025. 241
245
45.049
222
45.893
218
45,942
15
16
17
18
19
3497
3545
3720
5912
4096
1,402
1.3b6
1.045
0,700
0.451
1,207
27.069
44,021
44,249
45.098
45.954
45.971
45.9b3
0,405 34.698
27.868
27.860
27,069
0.144 34o683
27.071
46,805
61
61
61
61
9.293
7, 07*,
6.267
4.956
4.718
.
SALINIT '?ISIGMA
0/00
WHTA
35.82i 26.067
35,931 26.161
35,783 26.354
35.641 26.478
35.628 26.500
5
5
5
5
5
61
61
61
61
61
STATION
GEOSECS LEG V
FIRST CAST 1454
24 NOV 72
0,0W
STATION BOTTLE DEPTH TEMP POT TEMP
-CAST
M DEG C DEG C
NUPBER
61 5
1
17.436
-5
17.435
61
5
51
17.392
2
17,303
86
61
5
3
16.114
16.100
61 5
15.104
15.001
4
140
61
5
5
188
14.929
14.099
REPoRT
13.312
35.326
2.726 34.776
34,066
34,004
34,086
34.12
34,774
34,760
1.090 34.743
0.759 34.722
43.599
43.809
44.539
44.648
244
244
240
242
247
263
6
52
87
150
190
2046
2032
2046
2059
2064
2067
2044
2043
2061
2052
226
271
9.08
10.74
2331
2330
2342
2319
2305
0.70
9.08
2311
0.78
10.25
20662
1.13
1.45
1,61
15.73
21.01
22.97
2306
2205
2274
11.0
13.1
15.6
17.1
22.2
1.63
1.6B
23.66
24.73
1.75
1.78
1.87
25.71
26.39
27.96
1.7
1.7
2.0
0.39
3.1
0.70
0.81
3.6
3.1
3.4
5.6
8.7
10.6
0.41
0.!50
4.19
4.49
6.05
45.075
251
32.657
33.518
33.930
45.191
233
216
208
31.2
43.2
2.02
2.14
30.11
31.87
48.5
2.14
34.695
45.491
35.501
45,564
194
107
57.3
60.9
2.22
2,15
32.65
33.33
189
198
207
60.4
58.0
56.0
2.06
1.04
224
45.0
229
1. 6*4
45.1
1.59
46.1
42.9
1.56
1.40
1.45
23.84
70.5
06.9
1.74
1.08
26.23
28,14
96.4
145.618
45.66b
46.021
46.063
217
215
217
46.095
220
2347
2347
2343
1995
2004
2047
2037
2023
44.920
44.973
45.397
ALK(T) CO2(T) CU2(GC)PRLSS
U EG/KG UM/KG UM/KG 0.-AR
2023
2022
2041
2055
2051
259
254
256
45.340
NIS
61
UEPTH 4933 CORR.M
43 . 2
1083
31.08
28.03
27.75
25.01
24.23
22,76
22.37
1.98
29.61
2.08
30.78
116.0
122.0
2.15
2.18
31,66
32,25
320
367
430
490
2272
2108
2050
2068
2062
2081
2096
2269
2271
2272
2103
2116
2125
2126
2132
2093
2092
2118
2122
2131
2265 , 2155
2151
2165
2166
2215
2223
1157
1321
1401
2211
2211
2206
1o90
2053
2272
2274
2296
2306
2313
2u7
2016
2094
2179
2196
2205
32.25
106.6
********* PRELIMINARY DATA ONLY.....NOT FOR PUBLICATION**********
2329
2332
2322 -2214
540
602
b53
699
753
800
903
100b
155U
1728
2325
2205
2321
2188
2326
2173
2101
2537
2324
2171
2337
2204
2701
2064
3023
3211
2344
2219
2190
2173
2172
2211
2224
2347
2221
2233
2242
23 3
2359
2237
2242
2246
22 U
17
DEC
72
2213
2376
3413
3550
3630
3737
3975
4164
PAGE
1
DATA REPORT
R/V
POSITION
KNOnR
36
45
0.OS
STATION COTTLE DEPTH
tiur'OLR
M4
-CAST
20 4273
61 1
21 4463
61 1
61 1
22 4647
16 4704
61 8
17 4753
61 8
61 8
18 4784
GEOSECS LEG V
FIRST CAST 1454
24 NOV 72
0.0W
POT TEMP
TEMP
orG C DEG C
-0.017
0.305
0.209
-0.130
-0.188
0.171
0.157
-0.200
-0.215
0.155
-0.224
0.152
SALINITY SIGMA
0/00
IIETA
34.676 27.074
34.671 27.875
34.668 27.076
34.667 27.876
34.665 27.875
34.667 27.077
SIGMA
z
47.634
48. 467
49.285
49.536
49.749
49.970
34.666
34.665
34.655
34.674
34.672
27.076
27.075
27,067
27.882
27.881
50.071
50.078
0.155
-0.224
-0.223
-0.225
-0.228
-0.231
0 .15;
0.160
0.160
-0.231 34.672
-0.231 34.670
-0.231 34.674
27.881
27.879
27.883
50.421
50.509
50.520
4825
4e27
4644
4865
4885
0.155
0.156
.0.156
4905
4924
4926
0.156
*********
50.143
50.240
50.332
DEPTH
SIL
SIGMA OXYGEN
UM/KG UM/KG
4.
46.116 222
124.4
46.131 225
125.3
46.138J 226
126.3
46.140
46.140
46.143
46.142
46.141
46.134
46.149
46.148
IJIs
STATION
P04
lv03
UM/ K6 UM/KG
2.19
2.19
2.20
32.35
32.44
32.54
61(CCUNT)
4933 CURR.M
ALK(T) C02(T)
C02(GC)PRESS
U EQ/KG Ui/KG UM/KG D.UAR
2355
2240
2249
4351
2356
2245
2247
d247
4768
4836
4691
226
127.2
2.21
32.64
2358
2254
226
127.3
2.21
32.64
2361
2237
4913
4915
49-32
4953
4973
46.140
46.146
4541
473U
4994
2247
46.150
PRELIMINARY DATA ONLY.....NOT FOR PUBLICATION**********
5015
5017
17
DEC
72
PAGE
2