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QUALITATIVE DISTRIBUTION OF
ATOLL
RADIONUCLIDES AT RONGELAP
tirely dependent on cisterns as a source of water.
Rainfall in this area is comparativeiy iow and the
islets small, so that there is not a well-developed
fresh water lens.
There is, however, some potab!«
water in wells at Rongelap and Eniwetok Islets.
BLOB. HELD
ty of I ashington,
Paborute sof Radiation Biolowy. Larversi
gton
ashin
UW
Seattle,
;
of
In March. 1958, a radiveculogical study
request of the
ongela, Atud was instituted at the
SDivisien of Biology and Medicine, uU. 8. Atomic
This report wili be conM@@nere: Commiss1'n (AEC) .
Meerpned with generalizations regarding the distribuof
redioiuclides at the atoll in the fall
of
Btion
Zryo5y. some five years after contamination with
fa; lout.
+ adioac tive
Rorgelap Atoll was accidentally
4
contaminated
i954, with radioactive fallout from a
1,
fon March
Beher-onuclear device detonated at Bikini Atoll some
#60 miles to the west.
Gamma radiation dose rates
Sat Ronwelap or D+ 1 ‘detonation + one day) ranged
E¢rom 3.5 roentgens per hour at the southern islets
Bof the atoll tu 35 roentgens per hour at the northEighty-two natives re‘ern islets (Dunning, 1957).
Peiding on Rongela» Island, in the south, were evac~
Rated and did not return until June, 1957. At that
Hime the returning population
approached 300 in
Bumber but since appears to have stabilized at 230.
Several radiologicai and biological surveys,
primarily of a monitoring nature, were conducted
rom the time of the first contamination until
958 (Dunning, 1957).
During this time the gamma
adiation dose rates over land areas declined at
pproximately the rate predicted for mixed fission
roducts by Miller and :.eb (i958). Slight rises
n gamma dose rate were observed in 1956 and 1958,
resulting from tests conducted during these years.
owever, the total contribution of radionuclides
rom these subsequent fallouts amounted to a fracton of one per cent of the amount from the 1954
allout.
¢
b
Rongelap Atoll is located in the Marshall
Is-
Bands, in the Central Pacific Ocean. at about 319
North.
It
is a typical atoll with a
lagoon area of
O48 square miles and bout 180-fcot average depth.
The emergent land area is about three square miles
@nd is made up of 61 small islets ranging in size
from a fraci cn of an acre to the largest 2.Sland,
Rengelap, which is about four miles long and one-
halt mile across at its widest puint.
i
There is one small islet on the western reef
and the remaincer are strung along the northern,
eastern, and southern reefs.
The islets on the
hurthern reef are not as well developed as those to
the enst and south.
The waters of the lagoon are
esscntial!ly isothermal (Robinson, 1954).
The cir-
wlition, generated by the northeast trade winds,
pS orem east to west at the surface with a retiurnPog bottom current (Von Arx. 1954).
The estimated
a
Bi
wie
‘or renewal of water in the lagoon is about
Ca
ses The parent material of both soiis and the la-
SOs bot’ om is primarily calcium. arbonate origiue many from corallice alga
e, corals and
teera |
get
gee em hs
“
Pe
tt
in
There is also some accumulatior
of
Udlive:
the sgi.s
of
the
ares
are
Microne
ians.
BeTt ture is ilmited i. variety of proaucts
Sal:
: the focty ceaeanl esport is copra
About
Bimpor ts
' aaa consumed af the orcesen. time is
Meanie: ae and other »arine organisms are
MRew
io
ices Md A ee
is. sources are not exploited as much
sdb.
‘he fongelapese are almost en-
The native style wattle and palm frond buildings have been replaced by plywood and aluminum
structures built to Rongelapese specifications by
the AEC.
Sanitation habits have been altered by
the advent of pit toilets.
The terrestrial fauna is limited in variety.
The only mammal present is the small field rat,
Rattus exulans.
The most common birds are the
fairy tern, Gygis alba, and the noddy terns, Anous
stolidus and -& tenuirostris, which nest in large
numbers on some of the uninhabited islets.
The
reptiles are represented by skinks, geckos, and a
blind snake.
Land crabs are common, the most spectacular being Birgus latro, the coconut or robber
crab.
Insects are few, both in number of species
and individuals.
The most severe pest appears to
be the beetle, Brontispa sp., which attacks the
coconut palm,
in contrast to the land areas there is a tremendous proliferation of both numbers and variety
of organisms on the reefs and in the lagoon.
For
example, there are over 700 species of fish.
Plankton, however, is extremely sparse and as a
consequence the water is so clear that green algae
are found growing at depths of 180 feet.
Since the question of the effects of radiation
on the organisms inevitably arises, it might be
well to consider it briefly before going on to the
main subject.
There is no doubt that the levels
of radiation were of sufficient intensity to affect
living organisms,
However, under actual field conditions and without benefit of study before the
addition of radiation as an ecological factor, it
is difficult to do more than speculate concerning
the cause of the specific anomalies observed.
Fosberg (1959) has accurately described the poor
condition of the plants at the northern islets of
Rongelap Atoli and has suggested that the primary
cause of this condition is radiation.
In our opin-~
ion, however, other factors, particularly edaphic
factors, have probably been more important than
radiation.
The fact that the nitrogen content of
the soils of the northern islets is lower than that
of the rest of the atoil is at least circumstantial
evidence that for some time there have been
differences between these areas with respect to
plant growth.
Stone et al.
(1957) have concluded
from studies of Drosophila populations at Bikini,
Eniwetok. Rongelap, and
uncontaminated atolls that
while there is evidence of genetic changes caused
by radiation other factors mask the radiation
effects.
In short, it is not likely that such
questions will be resolved without controlled experimentation with the species involved, under
varying conditions, and with an eye toward the
possibility of synergistic effects.
Approximately five years after fallout the
long-lived fission products cesium-137 and stron-
tium-99 are the principal radionuclides found in
the Land organisms, while the neutron-induced
radionuclides zinc-65, cobalt-60 and manganese-54
arco found primarily in the marine organisms.
Still detectable in the soil are manganese-54,
droi-55. cobalt-57,. cobalt-60, zinc-65, strontium90. zirconium-95, ruthenium-106, antimony-125,
“esium-137, cerium-144, and europium-155. which
remain .ancentrated in the upper one to two inches.
Wherc higher levels of radionuclides have been
present these nuclides have been reported in a wide
variety or organisms.
It is likely that most of
these radionuclides are actually present in most if
167
nd,
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