eee ee SE
j. J. KORANDA
ND
3 Cactus Crater (Table 1) does not appear to be
of ADAMs,
related to the current level of tritium in the soil
conclusion
urce of the
water (509 T.U.) beneath that plant.
Because
the total loose water of a woody stem may
oil samples
aLOW and
contain water that is not involved in the current
uanspirational stream, the loose-water tritium
in nuclear
he Nevada
value for wood is not expected to be in equilib-
“ent in the
nd moves
physiolog-
rum with soil-water tritium levels. However,
the loose waterofthe leaves of the Messerschmidia
tree at Cactus Crater contained 442 T.U. which
is within the range of expected equilibrium with
the soil-water tritium (509 T.U.) indicated by
experimental studies.
The variation in the boundtritium content of
exhibit a
the Cactus Crater area within 30 ft of each other
~- .p to inter.
-9. These
the Afesserschmidia and Scaevola trees growing in
isno doubt related to the usual variation in soil
moisture conditions (whenever they are considered micro-topographically).
) with the
tration of
cted in a
The high tissue-boundtritium values of plant
amples at Cactus Crater indicate that not only
content of
is tritium present under the current environmental conditions, but also that it occurred in
n fallout
ation site
ly bound
higher concentrationsin the available soil water
in periods preceding this survey and subsequent
to the detonations. The higher level of bound
stonation
ritium in the inner growth rings or older wood
cimen or
ofMesserschmidia indicates greater concentrations
at earlier times, even if exchange mechanisms
are considered. The tissue-bound tritium
content of the Cactus Craterlitter samples, when
compared to the tissue-boundtritium values for
grecn leaves from the sametree,also indicates a
sin their
)2-15 months.
yorted in
Table 4.
aalysis of
es show
varying concentration of tritium during the
general,
e sample
Sinceit
mples in
ted with
On Engebi and Sandildefonso Islands, loose
water in plants and the soil had a low tritium
content also. Previous to the sampling, however,
available water must have contained more
tritium because tissue-bound tritium levels are
as much as thirty times (Scaevola litter) the
current loose soil water.
ie that in
samples
Because of the low level of tritium in the
available soil water in the presence of the large
tritium
aterials,
water of
level of
sources boundin thesoil, the levels occurring in
the organic matter as tissue-boundtritium seem
to be anomalous. The following sequence of
events should explain the conditions described
iced an
er of the
te loose-
above. The tritium levels in the soil water will
veadily increase if it is » ‘ moving through the
0 T.U.)
—
wil rapidly, as it would conceivably be in the
1455
rainy season. After heavy precipitation and in
very porous soil materials such as coral sand,
rainwater moves quickly through the soil profile
and washes the shallow root zones of the atoll
plants, lowers the loose-water tritium content,
and leaves it with the same tritium content as
the rainwater. The shallow root system of
Messerschmidia was described by Kenapy@® who
found that a 4ft high tree had lateral roots
which extended 60 ft from the crown within
2-6 in. of the surface of the ground. Becausé
the plant absorbs large quantities of water
daily, the loose water of the leaves will quickly
adjust to the low tritium content of the new soil
water, while the tissue-bound tritium of the
same plant confirms that previously, tritium
was more abundantin the waterofits root zone.
BLUMENsTOCK and REx"!”) give an average value
of 6.93in. of rain on Eniwetok Island for
August which wasthe time of samplecollection.
This would account for the lower loose-water
tritium content in soil water at this time.
In Table 3, the tritium analyses of samples
collected on four other islands on Eniwetok
Atoll are reported. These islands have been
contaminatedbyclose-in fallout which contained
large particles. Like the other islands, a large
source of tritium is present, bound in soil
materials. Also the loose soil water has a lower
tritium concentration, and loose-water tritium
values in plants, except for coconuts, were
generally between 50 and 150 T.U. Higher
levels were present in the tissue-bound tritium
of the plants. The elevated tritium concentrations in the coconuts from Japtan and
Igurin Islands would indicate that the tree had
been exposed to water of much higher tritium
concentration during the formation of the coconut.
Thetritium content of water samples collected
at Eniwetok Atoll is given in Table 5. Because
of the frequent exchange of the lagoon water
with the open sea and the vigorous mixing of the
lagoonitself, the water in the lagoon is apparently
uniform in its tritium content from surface to
bottom. Von Arx"#)estimated the exchange of
Bikini lagoon water with the open seas as once
every 13-39 days depending upon the season.
In spite of the frequent exchange of the lagoon
with the open sea and the occurrence ofintralagoon mixing, there is a local concentration of