showed 3,907 and 2,677 dpm/g, respectively.
are taken into account,
If the gravel contents
the values are reduced by 2.7% for the mound
samples and by 19.5% in the bare soil.
The analyses show that the
bare soil contains a slightly higher plutonium content even though
the field readings showed the reverse situation.
These findings of plutonium association with particle size contrast
with earlier studies of mound and bare soil samples
(Tamura,
1975a).
There,
from Area 5
(GMX)
the coarse silt in the mound samples contri-
buted only about 11% of the activity as compared with 75% in the
sample from Area 13.
About 75% of the activity from the mound in GMX
was in the coarser sand fractions.
The likely explanation for the
difference is the distance from GZ of the samples; at GMX, the distance was 250 ft; and at Area 13, 590 ft.
At GMX, particles of
coarse silt and larger sizes in the surrounding soil contributed 947%
of the activity; at Area 13, the same particles contributed about
74%.
Since closer distance to GZ would permit larger particles to be
deposited,
the difference in the bare soil and mound may be ascribed
to this difference in source term,
To date, particle size segregations have been made without benefit of
any dispersive treatment.
In order to evaluate differences in par-
ticle size distribution and possible differences in plutonium distribution, the samples of bare soil and mound were given 5 min of
ultrasonic treatment.
Table 4,
The results of this treatment are given in
By comparing results in Tables 3 and 4,
the notable feature
of the size distribution is the reduction in sand content and the
increase in silt and clay.
Overall,
the plutonium concentration in
the respective size fractions was not greatly different in the bare
soil.
In the mound sample,
the plutonium concentration in the size
fractions appears tohave decreased; this would suggest that the
particles being contributed by the coarser fractions to the finer
silt and clay were not highly contaminated particles and, thus,
these
particles proportionately changed the concentration in the different
Size fractions.
The effect of the ultrasonic treatment on the plutonium distribution
in the soil is that the contribution from the sand fractions decreased
and the silt and clay fractions increased.
The largest increase in
13