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Lagoon studies of transuranics will continue, providing adequate
ship support is available. The atoll seems to have reached a chemical
steady-state condition with respect to the partitioning of 239*240py
between solution and solid phases of the environment.
Using an
experimentally determined Ky for 239»240py, the dissolved quantity
predicted in equilibrium with the concentrations in sediment agrees
well with recently average measured concentrations In water at both
Enewetak and Bikini Atolls.
characteristics.
The remobilized 239924°py has solution-like
Over the next 250 y, an estimated 50% of the present
233,240py sediment inventory will be remobilized to solution and
discharged to the north equatorial! Pacific.
It has yet to be determined
if biological components of the sediments are an important link in the
remobilization process. Additional temporal data are needed to verify
our estimates of the rate of regenerated plutonium.
Our evidence that
plutonium is remobilized from the sediment to the water is substantial
and leads to the conclusion that similar processes must be occurring
in coastal and other aquatic areas. We are now modeling our data to
show the extent of remobilizatién that may be occurring in coastal and
other waters contaminated only with global fallout.
Less significant marine radiological pathways to man also require
study. For example, the highest plutonium levels in fish were found,
unexpectedly, in samples collected from the ocean reef of Sally tsland.
The gut samples contained contents with 150 pCi/g of 2392240pu,
However,
the concentration of other radionuclides was among the lowest detected
in fish at Enewetak Atol}. These are high isolated plutonium sources
at the atoll! available for uptake by marine organisms. As another
example, a particle high in plutonium was isolated from the gills of
fish caught near Yvonne. Using mass spectrometry we determined the
241py and, with the measured 2*!am concentration, dated the particle.
It originated in the 1958 test series from the non-nuclear test held at
Yvonne.
It is obvious that hot particles are still available to fish on
the reef.
If these nonedible parts of fish are recycled to the
terrestrial environment by man, levels of plutonium of marine origin
could be increased in village areas.
An evaluation of the expected
impacts from those less significant pathways will be made.
MAJOR MATERIALS, EQUIPMENT, AND SUBCONTRACT ITEMS:
Estimated Cost
Equipment
FY 1979
FY 1980
Groundwater sampling equipment
(pumps, generators, and in situ
conductivity meters)
$ 4,000
$ 3,000
Air samplers and generators for
reef work
In-situ filtration-preconcentration
system
5,000
.
5,000
Sere 7"
19,