>, and to eddyeffect, if this exists.
currents of radioactivity in the
Suciura and Kamepa (6), by
er the nuclear tests at Eniwetok
to a distance of 1,200 miles, which
- day. Harley reported the west-
miles west from Bikini, which
Marsh approximately six weeks
Test Site (Seymour ef al.), the
lerived from a surface detonation
Marsh survey, the centre of this
ini Atoll. During the intervening
of 300 miles at an average rate of
tive material in this area of high
the surface waters (above 25 m),
aminated water from the original
direction of the prevailing winds
adioactivity was carried by the
id and remained in the surface
rinal contaminated deeper waters
fairly large size and scavenge the accompanying radioisotopes out of the
mixed layer and through the thermocline into the deeper layers.
Plankton undergoes diurnal vertical migrations of distances that exceed
the depth of the thermocline, and thus may carry with it radioelements
adsorbed or ingested in the mixed layer.
Thus three layers of water in the ocean are normally present—the surface
te
etok Test Site the westward drift
ial to that of the current speed,
is may be attributed to the effect
kton into deeper water, where the
laver or mixed layer, in which mixing should occur easily; the thermocline,
which is very stable and across which radioisotopes may exhibit appreciable
movement only under special conditions; and the body of water below the
thermocline, in which vertical mixing is limited.
REVELLE, FoLtsom, GOLDBERG and Isaacs (8) (1955) reported that
when fission products were introduced at the surface of an area where the
mixed layer was approximately 300 feet thick, the radioactivity moved down
at a rate of about 11 feet per hour, so that within 28 hours the radioactivity
was uniformly distributed to the thermocline.
Any study concerning the influence of gravity on radioactive materials in
the open sea is complicated by the effects of currents and turbulent diffusion.
If the leading edge of the contaminated body of water is sampled with passage
MIXED
lmost due west, and according to
vity in comparison with the surhave initially contained apprecine of the second survey had sunk
220
he rate of vertical diffusion
that of molecular diffusion and
dispersion. The extent of vertical
he surface winds and the vertical
180 +
LAYER
—
28HOURS
693,740
476,000
600,000
184,000
PARTIC- 166,800
ULATE
93740
111,500
13.5
37.7
d/m
d/m
SOLUBLE
‘PLUS
COLLOIO
dm
200
300 m).
6 HOURS
H
642,800
TOTAL
>
> 160 5
>
5140 F-
PARTIC ULATE
26.0
46 HOURS
295,500
<
rature change and separates the
tok Test Site is Jess than 100 m
temperature is fairly consistent
in this layer should occur easily
cause the thermocline is a layer
this layer by turbulent diffusion
wn in the upper layer. Therefore
1ermocline should remain in the
to great horizontal distribution
However, radioactive materials
methods:
ied by large amounts of stable
8 where weapons are fired over
lay precipitate into particles of
9
2 120+
«
100 F
80F
6 HOURS
—-~- 28 HOURS
cot
vow48 HOURS
40
et
20
l
o
1
625050
Teese “20077
MO eceescassneeeree
wt
75s«éd1000
OEPTH
1
i
150
200
IN
300
METERS
Fig. 1
Distribution of total radioactivity in sea-water with depth at 6, 28 and 48 hours
109