aa”
ss
1.3
1.2,
u
1.1%
\
1.0 ,
OF
.8
RANGE OF UPPER
EDGE oF
THERMOCLINE
-7t
4
> 45
¢.45pu
OF
aE
aL
2{
4
et
COLLECTED 23
DAYS AFTER
\
5 l
SURFACE SHOT
COLLECTED 4 DAYS
AFTER OVER -WATER
ft
eee eee ISL
fe
J_--
re ee
25
50
DEPTH
75
IM METERS
sHoT
100
Fig. 7b
Ratio of activity in particulate fraction to that m solution plus colloid fraction from
two contaminated areas: one from a surface shot, and one from an over-water detonation
ge
oa ° oy .
In samples collected in the area from the over-water detonation, the total
radioactivity in the water was highest at the surface, decreased gradually at
50m to a value about one-third of the surface activity, and rose to a value
about two-thirds of the surface activity in the upper edge of the thermocline.
At 100 m depth the radioactivity was about one-tenth of that at the surface.
More than half of the radioactivity at the surface was associated with particles.
and at 25, 50 and 75 m less than one-tenth of the activity was in the particulate
form. At 100 m about one-sixth of the activity was associated with particles.
In both contaminated areas the particulate matter at the surface is probably
primarily comprised of microplankton. In the area contaminated with fallout
containing calcium compounds, the rise of particulate activity at and in the
upper edge of the thermocline is probably due, to a large degree, to very smal]
inorganic particles hindered from settling through the thermocline because ot
the density gradient. Because few particles would be present in fallout from the
over-water shot, a rise in ratio of particulate activity at the thermocline would
not be expected, and the observed rise was only approximately one-fourth that
observed from the ground detonation. The fallout area from the surface detonation was sampled 23 daysafter contamination; thus the larger particles present
in the fallout would have already sunk to depths below those sampled bythe
time of the survey.
Chemical factors
Pape eg Lot
eaeyb SS,
bt ey
Fie tA
al
Whenradioactive materials in the particulate form are introduced into seawater, the particles may go into solution either because of their high solubilits
constant or from increased hydrostatic pressure as they sink through the wate
by gravity. If initially in the soluble form, they may be precipitated as particles
of varying size by interaction with salts in the sea or with accompanying
materials, or by adsorption to biological or inorganic particles. The particles.
whether inorganic or organic, would tend to be removed from the mixed
layer by gravity, although the planktonic organisms tend to offset this effec:
«
.
.
-
116
nor
ane Pete