Radioecology
Page 146
Table
Percentage of total radioactivity in sea water and plankton contributed by fission products and neutroninduced radioisotopes at approximate times of 48 hours, one week, and six weeks after detonation.
1.
Time after detonation
Less
-99:
Ruthenium-103, 105, 106; rhodium-103,
Barium-140; lanthanum-140
Tellurium-132; iodine-132
Zirconium-95; niobium-95
Strontium-89, 90
Cesium-137
Neptunium-239
Uranium-237
Greater than one week
Plankton
Water
5.9
12.0
2.1
3.0
21
technetium-99m
Mo ly eid; praesodymium-141, 144 105,
than 48 hours
Water
0.83
106
2.6
6.2
0.38
0.30,
0.01
54.0
24.0
"0
Cobalt-47; 58, 60
0.02
Zinc-65
0.02
Iron-55, 59
Manganese-54
0,02
trace
3.0
2.0
8.0
1.0
0.0
0.0
69.0
3.0
0.0
0.0
0.0
0.0
Piankton
5.0
0.90
2.2
5.0
23.0
0.0
6.0
0.0
0.0
0.05
43.0
0.05
0.01
16.0
0.0
33.0
43.0
0.02
16.0
2.0
2.0
0.05
Plankton
0.0
5.0
20.0
0.0
6.8
5.6
1.0
0.76
0.05
Six weeks
Water
Q9.0
0.0
20.0
0.0
0.0
0.67
24.0
0.93
0.12
24.0
0.6
0.02
18.0
3.0
1.4
18.0
0.05
18.0
8.2
0.08
0.84
0.G
0.0
25.0
Less than 0.01 per cent.
However,
in some tropical areas, where the to-
tal mass of organisms is very small in comparison
to the volume of the water, the influence on the
distribution of radionuclides may be small and in
the open seas surrounding the Marshall Islands, at
jeast, appears to be insignificant.
In the sea at Eniwetok Proving Ground the ratio of the volume of the sea water to contained
plankton is approximately 100,000,000 to 1
(Anonymous, 1958). The ratio of total radioac- tivity in the water to radioactivity in the plank-
Because of the resulting uncertainty, the minor
differences between the percentages of radionuclides in plankton and water less than 48 hours
cannot be considered to be significant. At less
than 48 hours the radionuclides probably were taken
up by the plankton in an approximately direct
ratio to their occurrence in the water with the exception of strontium and possibly cesium. Of all
the radionuclides listed in Table 1 only radioactive stontium and cesium are initally present in
solution in the water.
ton in the same area was approximately 10,000 to 1
at one week and 30,000 to 1 at six weeks after
contamination.
Thus at one week the plankton
showed an average concentration factor of 10,000
and at six weeks 3,000 for the introduced radio-
sample.
centration factor of the plankton with increased
time is not known but has been observed to occur
consistently in samples collected in the open sea
Samples of plankton and water were taken and the
amounts molybdenum-99, technetium-99m; cerium,
activity.
The cause of the apparent drop in con-
at the Eniwetok Proving Ground (Lowman, 1960;
Lowman et al., 1957; Seymour et al., 1957).
In view of the observations that the plankton
contained only 1/10,000 and 1/30,000 of the total
~radioactivity in the contaminated area at one week
and six weeks, respectively, the organisms could
not have exerted a significant influence upon overall movement and distribution of the introduced
radioactivity.
However, the plankton might be
Experimental data taken in 1958 at the Eniwetok Proving Ground showed that radioactive strontium was actively discriminated against by plank-
ton relative to other radionuclides (Lowman, 1960).
promethium-141; barium, lanthanum-140; telluriumu,
iodine-132; zirconium-95 and strontium-90 were
determined by radiochemical analysis. The ratio
of observed strontium-90 to expected strontium-90,
based on the observed levels of the other radicnuclides, was calculated for various times after
detonation.
The results were as follows:
Time
3 hours
21 hours
36 hours
expected to affect the distribution patterns of
those radionuclides concentrated to the greatest degree (iron, zinc, and cobalt).
At six weeks the
ratios of total calculated amounts of radioactive
iron, zinc, and cobalt in sea water to those in
the contained plankton were 1,000, 900, and 700,
respectively.
Thus, even for those radionuclides
for which the plankton exhibited high concentration factors, the physical factors of the environ-
ment such as gravity and water currents probably
exerted the major influence upon their total
movement and distribution.
In Table 1 the percentages of radioactivity
contributed by the different radionuclides in sea
water and in plankton are shown at times of less
than 48 hours, greater than one week, and greater
than six weeks after fallout.
The values
for
water are based on the theoretical radionuclide
composition of fallout3 at the given times and are
Subject to error because they are not corrected for
fractiona
OME e+
tion and Precipitation in the
remy
Cesium-137 has not been
found in any significant amount in any plankton
3
sea water.
.
Ratio of cobait-60 to strontium-90 (Strom et al., 1958},
ratiog of cobalt-60 to manganese-54,
uraniaum-237, and ne tuni
um-239
to 1ron-59 (Lowman, 1960)
.
iron-59,
cobalt-58,
(Kn
i
RSPAPP? 1960), ratio of tron
55
Observed to expected
-43
.06
.03
At three hours approximately 4 as much strontium-90 was associated with the plankton as was
expected. At 21 hours and 36 hours the observed
levels were approximately 1/17 and 1/30 of those
expected.
The discrimination against strontium-90
in relation to the uptake of the other radionu-
clides, therefore, increased with time up to at least
36 hours.
In samples of plankton collected at
later times the levels of strontium-90 in the
plankton were too low to be measured.
Although the radionuclides were taken up by
the plankton less than 48 hours in approximately
the same ratio as they were present in the water,
selective
uptake at greater than one and six
weeks was evident.
At approximately one week the
three radicelements, cobalt, zinc, and iron contri-
buted only .15 per cent of the total radioactivity
in the water but accounted for 62 per cent of the
radioactivity in the plankton.
At approximately
six weeks the values were 2.44 per cent and 73 per
cent respectively.
The accumulation of fission
products by the plankton at one and six weeks was
variable and no marked pattern of active concen-
DOF ARCH IV
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