SMS
RADIOACTIVITY OF MARINE ORGANI
FROM GUAM, PALAU AND THE
GULF OF SLAM, 1958-1959
both the test site (Eniwetok and Bikini) and two
of the collecting areas (Guam and Palau) are within
the path of the westward-flowing part of this cur-
ALLYN H. SEYMOUR
The arrival of Hardtack fallout at the collecting areas was determined indirectly rather than by
a direct measurement of the radioactivity in sea
water. The criterion was a significant increase
rent system (see Figure 1).
Laboratory of Radiation Biology, University of Washington,
Seattle, F ashington
in the gross beta activity of marine organisms.
There ere two reasons for using this criterion:
first, small amounts of radionuclides in sea water
INTRODUCTION
are difficult to detect in the presence of the
salts that are normally present; and, secondly,
Following the Operation Hardtack (Phase I)
puciear test
The collecting area in
the Gulf of Siam is 4,250 miles west of Eniwetok
but outside the North Equatorial Current.
biological
series at Bikini and Eniwetok Atolls
in 1958. a study was made to measure changes with
time in the radioactivity in marine organisms collected at stations located at distances of over one
organisms concentrate certain fallout
nuclides and thus the specific activity for them is
higher than for sea water.
For these reasons bio-
logical samples are easier to prepare for counting
thousand miles from the test site. The radionuclides of principal interest were those from local
and require less counting time than sea water
samples.
currents from near the test site to the collect-
Other objectives of the program were to document the level of radioactivity in marine organisms
from the western Pacific, to provide additional information about the biological distribution of fallout nuclides, and to compare the results of this
study with the study following the Redwing test
series of 1956.
Hardtack fallout that were transported by ocean
ing areas, rather than the fallout nuclides trans-
ported in the stratosphere.
The study following
Hardtack supplemented a somewhat similar program
that was begun after the Redwing test series in
1956 (Thomas et al., 1958).
During the Bikini-Eniwetok phase of Hardtack
there were 24 barge, 2 surface, and 2 underwater
detonations between May 5 and July 26, 1958. A
large portion of the 19 megatons of total fission
yield credited to nuclear tests by the United States
and the United Kingdom for 1957 and 1958
1959) was produced by these detonations.
(Dunhan,
Thirty to
eighty per cent of the radioactivity produced by
the barge and surface detonations could be expected
to occur as local fallout
(Libby, 1959) and to en-
ter the ocean within a day or two after detonation
and within a few hundred miles of the test site.
Practically all of the radioactivity from the
underwater detonations would remain in the ocean.
One objective of the study was to determine if
local fallout from Hardtack could be detected in
ocean waters at distances of 1,000 miles or more
from the test site ‘Guam and Palau are 1,200 and
1,950 miles, respectively, west of Eniwetok).
SAMPLE COLLECTION, PREPARATION AND COUNTING
Samples were collected at approximately three-
month intervals beginning in June 1958 and continuing until November 1959, except in the Guif of
Siam. There were four collections in the Gulf of
Siam and six each at Palau and Guam.
Samples in-
cluded fish,
and plankton.
crabs,
lobsters, snails,
clams, algae,
In addition, 72 weekly plankton sam-
ples were collected at Palau, site of field headquarters for the George Vanderbilt Foundation.
Plankton samples were preserved in ten per
cent formalin, but all other samples were sent freshfrozen from the field stations to the laboratory.
The samples were held in a freezer until they were
processed, at which time they were thawed, dissected, weighed, dried at 95° centigrade, reweighed,
ashed at temperatures up to 540° centigrade, and
If
so, then an estimate could be made of the rate of
movement of local fallout by ocean currents, in
this instance the North Equatorial Current, since
again reweighed prior to counting.
160°
60°
al
40°
aan
-
“G es <a
A eurran
:
North Poetic .
OB
“Kwbsme Et
ae
TFN IER Rte 8 one, toe
1
ago
Figure 1.
The major surface current systems in the north Pacific Ocean
(after Seckel and Waldron, 1960).
151
DOE ARCHW bo