30
29
of the inventory estimated to a l6-cm depth in the sediment column
disturb large quantities of material and release large amounts of
(Table 1).
unassimilated material containing plutonium in their feces.
The average quantities of soluble plutonium in the water are
Moriarty
in recent
(Mo76) estimates that a 200-g mullet, a species common to Fnewetak,
years only small fractions of the Atoll plutonium inventory is either
which feeds by scooping up bottom material to sift and remove small
remobllized to the solution phase or resuspended to the water column.
algae, will pass 50 g of dry sediment through its gut per day.
also small fractions of the sediment inventory.
Therefore,
During 1976 zooplankton samples contained less than 1% of the
Bottom particles from the NW quadrant of the lagoon where highest
23942405, activity in the total material filtered from an equivalent
piutonium concentrations in sediment are found usually have high
volume of water (No78b).
plutonium concentrations, indicating that a fraction of
The remaining 2394240Pu in the particulate
the plutoniua in
material is therefore associated with other forms of suspended matter,
the particulate phase may originate from turbulent resuspension of the
Between 1960 and 1963 Johannes investigated the composition of the
sediment components in deep
suspended particles in the lagoon (Jo67).
associated plutonium is probably not transported for any distance in the
Progressing from the eastern
(60 m) water.
This resuspended material and
reef toward the lagoon, suspended benthic alyae and sediment particles
lagoon.
became less abundant with depth of the water as they settle to the
the same general area of its origin.
bottom, and suspended macroscopic organic aggregates, consisting largely
active processes capable of generating and moving particulate plutonium
of mucus released by coral, increased progressively in size and number
in the water mass have been considered,
(Jo67).
ether processes resuspend so little of the plutontum inventory.
Often calcareous grains resuspended near the reef,
Previous results indicate that the material
is redeposited in
Only a few of the vartety of
It ds romarkable that
these and
barring
microorganisms, copepod fecal pellets, and other undifferentiated
catastrophic events, the present distribution and inventory of plutonitin
material were incorporated with the aggregates.
in the sediments will be only slightly altered durinp the years by
These materials and
other particles produced in the pelagic environment are the most
important food components for lagoon zooplankton and certain
plankton-feeding fish (Ge74).
The small quantities of plutonium
relocation of labelled material from other regions in the lapeon,
Laboratory studies with contaminated sediments and soils from
Enewetak show that plutonium is rapidly partitioned between the solid
ingested with this particulate debris is dispersed over the lagoon by
phase and solution, reaching equilibriur after severel days with an
these organisms.
average distribution coefficient for plutenium of 1.8 x 10",
Herbivorous fish play a role in the generation of
particles in the water column (5m73).
These fish are not efficient
assimilators; while satisfying their energetic requirements, they
Table &
shows this and some recent determinations of the distritution
coefficlent for plutenium in laberatory and field experfinents using a
Je
are pac’ s