Radioecology
ap
but that the levels
Rongel
pt all organisms gs Onat ee
extremely low and so escape
Meat which they occu
Metection.
solution,
Passing from the soil to the soil
:
collecBehe term being used here to mean leachates
lysimeters, strontium-90,
Heed in the field from ony-1
25 are the principal nuMresiun-i37, and antim
Belides found.
although Rul06-Rh106, cerium-144,
et al.,
‘Send europium-155 are also detectable (Cole
t to soil
respec
with
exist
s
rence
diffe
Here
_
“*
“Mtype in that the leachates from immature soil,
Beoosisting almost exclusively of parent material,
ium-90.
Beontained only antimony-125 and stront
for this
n
natio
expla
t
eviden
no
us
to
is
: ere
Bdifterence.
&
The ground water probably contains these nu-
felides since their movement has been detected in
Heachates to depths of 30 inches, but the levels
Bare so low in ground water that special techniques
Pwould have to be developed to detect them.
;
The
Land plants contain principally cesium-137
and strontium-90. Manganese-54 and zinc-65 have
heen found in plants from the more heavily contami-
inated 1slets but are present in relatively insigMnificant amounts.
In general,
cesium-137 accounts
for yO per cent or more of the radioactivity in the
land plants and strontium-90 for the remainder.
This is unlike the situation usually found on con-
tinental soils and is a consequence of the low
potassium content of Rongelap soil.
Amendments of
potassium to Rongelap soil reduce the uptake of
cesium-137 by plants (Walker et al., 1961}, and
general, no definite sources of zinc-65 are known
to exist five years after fallout.
It is possible
that there is concentration of undetectable levels
from the sea water or algae. The possibility that
most of the zinc-65 radioactivity in fish is residual appears to be ruled out by the fact that young
fish contain relatively high levels.
The marine invertebrates taken as a whole contain a wider spectrum of radionuclides than de«the
fish.
These are manganese-54, cobalt-57,60/
65, strontium-90, cerium-144, and probably e&
155. The corals contain cobalt-60 and are thé
only invertebrates in which strontium-90 has bees
consistently detected. From limited data available thus far it appears that these nuclides were
deposited in the skeletal material soon after fallout and have remained localized in portions of the
coral colony actively growing at that time.
The
clams contain mostly zinc-65, cobalt-57 and cobalt-
60.
Weiss and Shipman (1957) originally reported
the concentration of cobalt-60 in the kidney of
Tridacnid clams collected at Rongelap in 1956.
Animals such as the sea cucumber
(Holothuria,
Stichopus) and spider snail (Lambis, Strombus),
which Tngest large amounts of bottom sediments,
contain ruthenium-106, cerium-144, and probably
europium-155.
Of several species of algaé sampled in 1959
the only radionuclides detected were ruthenium-106,
cerium-144 and europium-155. In general, the
levels of radioactivity in the algae are lower
affect the distribution of cesium-137 within the
plant.
There are, of course, differences between
than in the fish or invertebrates.
relative amounts of cesium-137 and strontium. For
‘example, copra contains very little strontium-90
57,60, zinc-65, zirconium-95, ruthenium-106, and
cerium-144, but all in minute amounts. In 1959
plankton samples collected by pumping a total of
two and a half million gallons of water were
pooled for gamma-ray spectrum analysis and were
found to contain only enough of these nuciides
plant species and plant parts with respect to the
as compared with Pandanus fruit, and the basal
leaves of various plants contain more strontium-90
frrelative to cesium~-137 than do the terminal leaves.
This variation is related to differences in mobility between cesium and potassium, and strontium
and calciun.
i
The rats contain cesium-137 and strontium-90,
preflecting the radionuclides present in the plants
on which they feed,
The coconut crab and the land
thermit crab (Coenobita perlatus) contain the same
nuclides but concentrate strontium-90, as has been
reported for Coenobita from Eniwetok Atoll (Held,
The occurrence of radionuclides in man at
‘Rongelap has been summarized by Cohn et al.
(1960).
In 1958 these nuclides were cesium-137 and stron-
;tium-90 coming form the food plants, and zinc-65
coming to man from marine products.
g
The birds, which feed almost exclusively on
fmMarine organisms, contain primarily zine-65 and
moccasionally small amounts of manganese-54 and
g@ cobalt-60.
Strontium-90 is also found in small
@ amounts in bird bone and may reflect direct uptake
@ from the ingestion of soil, although there is
no
@ Girect evidence that this occurs.
‘
vertebrates containing zinc-65 are known to be |
sumed by fish found to contain zinc-65, but, in
Fs,
cope enue ides in fish are limited to manganese-
Fdowinent
On’
and Zinc-65,
the latter being pre-
Agoatfish (M oe dry-weight basis for a sample of
PRignest 1esepecoecnthys Samoensis) testes have the
Penh eyes eve 5
the
liver, gastrointestinal
tract,
Pend the mese) Ower by about an order of magnitud
e,
Forder of nee ‘ and bone lower by still
another
Paccivity 5 Kn tude
If the totat amount of radioprinc: pa) ye ‘sue 18 considered, then
bone is
Bort] commune en Ory of zine-65 (Joyner, 1961, tne
per-
fton are
teatioay
. The
open
to question
.
sources of zinc-65 for ['
In some instances in-
The plankton contain manganese-54,
cobalt-
for qualitative analysis without resorting to
chemical separations. Further analysis has been
deferred until other studies with the individual
samples can be completed.
The lagoon sediments contain strontiun-90,
ruthenium-106, cerium-144, and europium-155.
The
radioactivity is associated mainly with the fines
and is concentrated in the top two to four inches,
dropping off rapidly with depth.
Radionuclides other than naturally occurring
potassium~-40 were not detected in sea water al-
though larger samples and more sensitive techniques
undoubtedly would have revealed their presence.
In sum, on land the present distribution of
long-lived fission
cesium-137, can be
as it is now. The
reduced primarily
products, strontium-90 and
expected to remain very much
levels of radioactivity will be
by physical decay of the radic-
nuclides so long as other factors such as changed
agricultural practices or a catastrophic storm
do not occur.
In the lagoon, the levels of radioactivity will decline more rapidly than on land
because of the presence of shorter-lived radionuclides, with the exception of strontium-90. The
latter does not enter the marine food web to any
significant extent and may remain as a label use-
ful in evaluating the long-term effects of physical
forces in
the lagoon.
SUMMARY
The qualitative distribution of radionuclides
at Rongelap Atolia as determined approximately five
DOR Ai. bhi we