Table 4.1 RADIOACTIVITY OF WATER SAMPLES*
Pretest
Island
Posttest
Sample
depth,
Fe(OH);
Ca-Sr_
Sample
depth,
Whole
Fe(OH),
7
Ca-Sr
ft
scavenge
oxalate
ft
sample
scavenge
oxalate
4
25
Background
0.09
0.17
Japtan:
Surface
Bottom
-
0.48
Background
Igurin:
Surface
Bottom
40
Background
0.01
60
16
Background
0.32
0.72
0.30
0.14
62
0.07
0.04
55
19
Background
2.3
1,8
0.83
0.66
Rigili:
Surface
Bottom
Bogombogo:
Surface
Bogallua:
Bottom
0.35
0.05
350
96
18
45
1.11
0.26
23
330
92
16
55
0.02
0.04
25
46
70
20
22
84
0.01
0.02
25
Background
Background
5.0
7.0
1,0
1.0
20
0.13
0.25
20
40
Background
0.84
0.04
0.35
0.22
Engebi:
Surface
Bottom
2.7
3.1
Aomonand Rojoa:
Surface
Bottom
Runit:
Surface
Bottom
OR.
* Measured in disintegrations per minute per milliliter.
A gross examination of the types of organisms present in the catches was made to de-
termineif the difference in counts between net hauls and between stations could be accounted
for by the type of organism in the cateb. Although the catches varied considerably, both
quantitatively and qualitatively, there was strong evidence that the activity of the samples was
not associated with the presence of any one group of organisms. Autoradiographs of a dried
9,
plankton sample showed that the activity was usually associated with inanimate objects, but,
even when the organisms were active, the association was not with any one particular group
(see Sec. 4.9.1). Further evidence was obtained from the paired hauls, in which the activity
of the samples often varied, but the composition of the catch was similar. For example, the
catch in net B and net D at Bogallua appeared similar in composition (foraminifers, principally, and some snails, copepods, and a few miscellaneous eggs and arrowworms), but the
sample from net B was seven times more active than the sample from net D (1,160,000 d/m/g
as compared to 155,000 d/m/g). Since net B was of finer mesh than net D (173 and 74 meshes/
in., respectively), it might be thought that some small radioactive organism was escaping the
D net and was being caught in B, but microscopic examination of the catches did not demonstrate this to be true. It is believed that the fine-mesh net was more efficient in capturing
suspended inanimate radioactive particles.
The radioactivity in plankton samples is recorded in Table 4.2.
28
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