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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