>
x3
paper, the ratio of radioactivity in the macro-microplankton to that in the
nannoplankton plus particulate matter is insignificant (on the average 0.00025
of the particulate matter), and all the material on the filter paper may be
considered to be from nannoplankton and inorganic particulate matter.
Also, no macroplankton was retained on any of the filter papers.
The radioactivity of the macro-microplankton per unit volume of sea
water was calculated by using data on plankton volumes reported by the
Pacific Oceanic Fisheries Investigation from surveys made in 1956 and 1957
in the Marshall Island areas. In this study, the volumes of water strained by
2
.
.
plankton nets were measured and compared with the volumes of plankton
obtained. In the open sea approximately one ml of plankton was collected
for every 100,000 1 of water filtered.
In four different surveys made at the Eniwetok Test Site in 1956 and 1958,
the radioactivity in the macro-microplankton was low in comparison to
that in the particulate material and to that in the dissolved material (Table IT).
ne
”
q
/
ie
:
ay
oe
at
.
te
epee
ety
TABLE II
Loo
om cm
ae
.
.
ets
sy
.
.
"
yy
mer
:
RATIO OF ACTIVITY IN WATER TO ACTIVITY IN PLANKTON
.
.
Filter paper |
plankton
|
i
co;
plankton
Filter paper + CO,
plankton
7,600
10,500 4—23 days
after detonation
|
i
ve Te Poo
ot
'
tes
.
‘
a
| Walton survey 11—21 June 1956
'
2,900
|
_ Marsh survey 1-21 Sept. 1956
7,800
|
|
| Collett survey, 8-—14 Aug. 1958
|
' Silverstein survey, Sept. 1958
. Walton—device detonated over
-
!
water
Walton—fired on ground
|
|
1,500
|
6,100
3,400
.
ee May eee ge
ee
Fe
ge,
sb,
:
a
.
|
|
2,900
7,400
36,000 ~90 days
after detonation
10,900 at end of
series
| 105,000 ~ 3 weeksafter
|
end of test
10,500
.
coy
+
re
.
oe,
a
Seee NS ce eali
ge RAESE IT he
et
9,400
106,000
"
,
28,000
|
|
series
13,900 4 and 6 days
post-shot
10,300 23 days postshot
The Walton survey was made during the middle two weeks of June 1956
(during the test series) and included 53 sampling stations. Two centres of
contamination were included in the survey area and were sampled 4-6 days
and 23 days respectively after detonation of the devices producing the fallout.
In an average of the Walton samples, the particulate matter greater than
0.45 « contained 2,900 times and the dissolved material 7,600 times as much
radioactivity as did the macro-microplankton per litre of water. The samples
were also subdivided to include (1) the fallout area resulting from contamination produced by two closely-spaced over-water shots, and (2) a contaminated area with fallout containing large amounts of calcium compounds from
a device fired on the ground. No appreciable difference existed between
the ratios of particulate activity to macro-microplankton nor the dissolved
activity to macro-microplankton in these two areas.
Another survey was conducted with the USS Marsh approximately
21/, months after the Walton survey. The filter paper/plankton ratio was
124
1.
wee
eeee
V
Ae
nV .
;