prevention of wind erosion and acts as an intermediary trap for blowing
particulate material.
Discussion of desert environment problems and associated recommendations
are presented by Wallace and Romney for measures to be considered in the
proposed cleanup and restoration of areas at the Tonopah Test Range and
Area 13, NTS.
Through examination of past decontamination and soil
disturbance experiences in the Great Basin Desert, Wallace and Romney
found indications of tendencies toward slow natural recovery in disturbed
areas.
Revegetation considerations of disturbed areas are addressed in
detail, with excellent bibliographic material included.
The inventory of plutonium, americium, and uranium in/on vegetation
samples from Plutonium Valley (Area 11) intensive study sites was deter-
mined from analyses of samples at McClellan Central Laboratory.
(Mount's
excellent report of analyses of 238pyu, 24 1am, and 235y in vegetative
material is included in this document.)
The soils under desert plants
in mounds were investigated by Tamura, ORNL, to determine whether the
character and behavior of the plutonium in the mounds were similar to
that in desert pavement soils.
Analysis of samples reflected some of
the problems of sampling mounds.
The distribution of radioactivity
observed demonstrated the importance of sampling techniques.
Preliminary
data on the activity in particle size fractions, in terms of activity
per unit mass, indicates that the coarse silt (50-20 um) contains the
highest activity in the desert pavement samples.
The medium silt (20-5 um)
contains the highest activity in the desert mound samples.
As considerable mechanical mixing had occurred in the mound sampled, it was difficult
to interpret measurements of depth distribution.
In making particle
density measurements, Tamura found an indication that the desert mound
particles in the 20-5 and 5-2 um size classes are lower in density than
the corresponding size classes in the desert pavement.
In the smaller
Size classes in both types of samples, the data suggest that plutonium
is distributed in the lighter fractions as well as the heaviest fraction.
Study of the implications for uptake by man and grazing animals through
ingestion or inhalation of particles from desert mound samples character-
ized by Tamura awaits more definitive data.
NAEG plans include investigation of various natural mechanisms (organic and inorganic soil complexing)
by which biological uptake may be enhanced.
Fowler and Essington emphasized the fact that current soil profile data
from samples taken down to 25 cm indicate that the maximum depth of
penetration of plutonium in soils at NTS is still unknown.
(Greater
in-depth sampling, of course, depends of availability of funds.)
Another
problem indicated is the disparity in the plutonium-americium ratios
among study sites.
Difficult analysis of americium is suggested as a
possible cause of the disparities.
Also, other factors impinge on the
data available, e.g., mechanical disturbance at some sites, differences
in times and types of plutonium release, variance in climatic environments
at NTS, etc.
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