In the four oceanic surveys made at the Eniwetok Test Site during 1956
and 1958, the ratios of particulate activity to soluble activity in water samples
exhibited similar patterns (Fig. 4), with ratios relatively high at the surface,
dropping to a minimum value at 25—50 m,and rising again near the thermocline. Only in the 1956 (Walton) surface samples, taken 4—23 days after
observed during the Walton survey resulted from a surface land detonation
which, at the time of sampling (23 days after detonation), included an area
approximately 100 miles in diameter.
Another fallout area with much lower activity, observed during the Walton
survey, resulted from two devicesfired over water 4 and 6 days before sampling.
The contaminated area was approximately 30 miles in diameter. Thefallout
material from the surface shot contained large amounts of calcium compounds,
whereas the material from the over-water shots was mixed, for the most
part, with evaporated salts from sea water and the material surrounding the
nuclear device. The radioactivity was not distributed evenly throughout the
mixed layer in either contaminated area, and in the areas of high activity
from both the surface shot and the over-water detonation the activity in the
water tended to be concentrated near the thermocline (Fig. 7a).
500
i.
3 200 |
< +
oe
Pree
ae
g
secre
COLLECTED
23
ITA wn
SURFACE SHOT
eo
lh
i the relative radioactivity of the water
epth sampled. Maximum value at each
as 100
o
ss5
RANGE OF UPPER
EOGE oF
THERMOCLINE
aad
a
Pr
au
Pereee
PP
Oe
D/M
ao
qn
on
on
an
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CE
ad
a
an
ve)
ww
in
An
an
wn
os
nn
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yr
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r
wo
oa
an
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ALINCWICN
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ae
contamination, did the particulate fraction contain a greater amount of
radioactivity than the soluble fraction. The major part of the radioactivity
Le,
pee
;
fawn
AFTER
Es 4 aA
DEPTH
IN
OVER -WATER
SHOT
METERS
Fig. 7a
Total activity in water from two contaminated areas: one from a surface shot and one
from an over-water detonation
ae Marshall Islands and as far\west
ain 6-—8 weeks after contamination
aken during four different surveys
vas not uniformly distributed in the
; after contamination and 6 weeks
particulate matter to those in the
The radioactivity in the water was about six times as high in the area contaminated by the surface detonation as in that contaminated by the over-water
shot. The water samples from these two areas were combined into two samples
to determine if any differences in distribution of activity with depth was
apparent between the two types of fallout. In the area of fallout containing
relatively large amounts of calcium compounds, the radioactivity in the water
| throughout the depths ‘above the
in these two figures are averagesof
| trends. The lack of homogeneity
ked at individual collection stations
Within the upper thermocline the radioactivity was about the same as that
at 25 m. The ratio of radioactivity associated with particulate matter to that
associated with matter in solution was high at the surface (ratio=1.17), low
at 25 m (ratio —0.03), and rose with increasing depth into the thermocline to
1e upper mixed layer (Fig. 4). Also
washigh at the surface, low at 25 m, and again high just above the thermocline.
a value of 0.39 at 100m (Fig. 7b).
8°
115
~ AEG
+ we