tems ee Padded o
colloidal form. However, at 48 hours particulate radioactive material accounted
for two-fifths of the total radioactivity. A major part of this activity was concentrated at the upper edge of the thermocline. Fig. 3 shows the percentage
of radioactivity in the sea water in the particulate form at different depths
with increasing time after detonation. In the two samples collected within the
‘mixed layer (0 m and 50 m) the percentage of particulate radioactivity in the
water decreased between 6 and 28 hours androseslightly at 48 hours. However,
in the upper edge of the thermocline (100 m) and inside the thermocline
(300 m) the percentage of particulate activity rose at an increasing rate during
the interval 6—48 hours post-detonation. The percentage of radioactivity in
the particulate form at 300m rose at an exponential rate from a value of
approximately 1% at 6 hours to 37% at 48 hours.
During the interval 6—28 hours the leading edges of the particulate radioactivity moved downward approximately 50 m, and thoseof the soluble-colloidal
activity approximately 60 m. During the time 28-48 hours the leading edges
of both the particulate and the soluble activity in the mixed layer descended
approximately 50m. Thus the activity in the mixed layer during the entire
period of sampling descended at a rate of approximately 2.5 m per hour.
Below the mixed layer, however, the radioactivity in the particulate form
appeared to descend much faster than that in the mixed Jayer. During the
period 28—40 hours the peak of radioactivity moved down at least 200 m,
1.5
WALTON SURVEY (JUNE It- 21, 1956)
1.4]
1.3
4.28
4 DAYS TO 23 GAYS AFTER CONTAMINATION
otieMARSH SURVEY { SEPT. 1-20, 1956)
G WEEKS AFTER END OF TEST SERIES
----- COLLETT SURVEY {AUG.8-14, 1958)
AT END OF TEST SERIES
ee SILVERSTEIN SURVEY (SEPT. 3-13, 1958)
4.44
J WEEKS
AFTER
ENC
OF
TEST
SERIES
1.0F
245
C45
aT
8
FP
0 2550
RANGE OF UPPER E£0GE
OF THERMOCLINE
THERMOCLINE
100
i“
ra
*
300
4ao
DEPTH IN METRES
Fig. 4
Ratio of activity in particulate fraction to that in soluble plus colloidal fraction in all
water samples from four oceanic surveys made during 1956 and 1958 between the Eniwetok Test Site and Guam
112
on
~i”