17
18
and 241i in the Atoll sediments is made (see Table 1).
Transuranic
isotopes deposited from global fallout of weapons debris are estimated
from available data (Kr76, Ha73) and are also given in Table l.
only a small fraction of the total quantity deposited to the earth
Some specific marine environments
However, these lagoon sediments are the most contaminated
aquatic regions in the world that received transuranic inputs only from
nuclear weapons,
The estimated
23 9p,
4
2405
4
waa and 2418
Enewetak, while 2385, is higher in Enewetak Lagoon.
Am levels is expected at Enewetak from
24)
2394240,
Pu in sediments in
Buzzards Bay, Mass., where the 2394240), was not preferentially
associated with the fine fractions of sedimentary deposits
difference is perhaps not unexpected, because most of the transuranic
inventory deposited to the lagoon environment was probably associated
During the years after nuclear
Pu
The transuranic inventory at lagoon locations, however, is
dependent on the local abundance of the fine and caoars, materials.
Table 2 shows the 2A concentrations in the {fine and ceorarse comionents
of two core samples from mid-lagoon locatiens at Fnewetik.
TRANSURANLCS ASSOCIATED WITH COMPONENTS
Using the definition ef Fmery et al.
IN THE
SEDIMENT COLUMN
(Em54) for classifying fines
as material less than 0.5 mm in diameter, 23 surface samples and several
cores were separated into fine and coarse fractions.
The dry weight of
the fines ranged from 25 to 80% of the total dry weight of the surface
Atoll sediments.
A similar range
of fine material was found in Bikini
At least 93% of the sediment weight in Mike and Koa
crater deposits was fine material.
from Enewetak lagoon, the
ee
This
reactions with exposed surfaces of the larger sedimentary components.
decay.
volume (No78a),
(Bo?6).
testing, some plutonium has exchanged slowly as a result of chemical
Inventories of
2Alay at Bikini will increase by 25% from 241p, decay, while only a 10%
241
The activity
These distributions between size fractions are
with small particulate carbenates.
inventories at Bikini exceed the respective isotopic inventories at
increase over present
in the coarse fraction.
very unlike those encountered for fallout of
were contaminated with substantial quantities of transuranics from other
source terms,
to the concentrations associated with the coarse fraction.
of 41 and 23942405, in the fines was 0,6 to more than 10 times that
The inventory at the Atolls of transuranics produced by weapons is
surface with global fallout debris.
associated with the fine sediment components were greater than or equal
In over 98% of the sediment samples
24) Am an d 239+240 Pu concentrations (pCi/g)
The traction
of the coarse components in the sediment column of core 6 decreases with
depth and in core 1 increases with depth,
os
24)
The
Am concentration
associated with the fine fraction in the surface 2-cm section is 2 to 5
times the concentration associated with the coarse fraction; but because
the fine material in the surface layer of core 6 accounts for only 257%
of the total dry weight of the sediment volume,
y
241
58% of the
Am in the
surface 2-cm layer is associated with the coarse fraction.
In core l,
o
241
.
.
on the other hand, 95% of the total
Am in the surface 2-cm laver is
associated with the fine fraction.
Although the
241
Am concentrations
pos Anca