26
25
gravity of the Halimeda and other sediment components is 1.8 g/em?
carbonate matrix and its associated transuranics in the sedimentary
(km54).
deposits.
Activities of 2394240, assoctated with the algae are related
to the activity in the surface sediment,
The mean wetidry ratio of the
The transuranics associated with the organic fraction
released during decomposition are recycled to the benthic or pelagic
Halimeda species is 2,3, and the average wet weight of the plants,
environments.
without holdfast, is 6.4 + 3.8 (No78a).
cycling the transuranics between the sediments and aqueons environment.
Therefore, the average
Over the long term the algae could play a key role in
2394240, concentration associated with the live Halimeda species at
Enewetak is 0.62 pCi/g wet weight.
with each plant.
PLUTONIUM CONCENTRATIONS IN THE LAGOON SEA WATER
Approximately 4.0 pCi are associated
If the number of Halimeda plants were known, the mean
A considerable number of lagoon water samples have been collected
Plutonium inventory associated with the living Halimeda reservoir could
for plutonium analysis by this laboratory since 1972 (Ke/3, No74, ho76,
be computed.
No78b).
Unfortunately, no estimates of Halimeda biomass at
Enewetak are available.
During the late 1940s, the mean sedimentation
rate of Halimeda at Bikini was estimated at 3.8 mm/yr (Em54).
If this
Several studies are in progress at the Atoll that require data
on concentrations in lagoon water so that the number of samples and the
locations sampled are predicated by the current program requirements,
£ 2394240
sedimentation rate is applicable toa Enewetak Atoll, approximatley 1 Ci
Contours o
of 2394240, is deposited annually in the sediments in association with
distribution patterns (No74)
Halimeda detritus.
This quantity represents only 0.4% of the surface
Pu concentrations in the water show complex
in various regions of the lagoon,
4
The
.
Spatial patterns of surface and botton 23942405, concentrations in
sediment inventory and yet a smaller fraction of the total inventory in
solution and in association with filterable material are verv different
the sediment column,
as are the 2385 239240), ratios in the water mass.
However, if the life span of each plant is l yr,
A detailed
for example, a quantity of 2394240 Pu equivalent to half the present
discussion of the plutonium levels in the pelegic environment of the
sediment inventory, or 125 Ci, could be recycled with the algae in
lagoon is in preparation (No78b).
approximately 175 yr.
the analysis of lagoon water samples collected since 1972 with
Spies et al.
(Sp78) demonstrated that when live
Instead of relating all results fron
Halimeda from Enewetak were cleaned and treated with 1N acetic acid, the
hydrological, seasonal, or spatial factors, we will suriarize sore of
acid soluble fraction, or the carbonate material, contained 58% of the
the data that is related to remobilization and redistribution of
total 239240.
plutonium,
Pu, while 42% remained bound to the plant tissues.
plant decomposes after death,
As the
the organic material and associated
radioelements are released to the environment leaving the skeletal
In 1972, 1974, and 1976 a suffictent number of water samples from
JOH4240,
:
.
the lagoon were analyscd for 23942 A Pu to permit an estinate of mean
.
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