of plutonium levels in field and laboratory investigations.
Soil concen-
tration is the most significant source term, subject to wide variation.
Mass loading factor for air and parameters of the lung model used for
radiation dose estimates also affect the sensitivity of estimates of
radiation dose to man.
Bloom and Martin report their analysis of the
effects of variations in these important factors.
Results indicated
that none of the variations examined were surprising except, perhaps,
for the large range that occurred due to variations in the parameters of
the lung model.
The largest variations were due to translocation class,
a parameter which could cause a factor of 600-700 variation in dose rate
to lungs in respirable size range particles; rate for bone parameter
caused less than a factor of 4 variation with particle size, where
translocation class caused less than a factor of 60 variation.
These
wide ranges of values need further exploration in attempts to move
narrowly defined bioenvironmental differences and impacts on modeling
efforts.
Martin and Bloom, BCL, also conducted additional simulation modeling
studies for the NAEG grazing cattle plutonium ingestion investigation.
Martin and Bloom concluded that the grazing, soil, and plant studies
conducted in Area 13, NTS, were apparently well designed; that a repetition of the study would probably yield results similar to those already
obtained; that given an adequate sampling design, reasonably accurate
estimates of plutonium ingestion rates by grazing cattle can be obtained
in spite of the extreme variability of contributing factors; and that
given site-specific input parameters, the simulation model provides.
estimates of plutonium ingestion rates which are as accurate as those
obtained from long-term grazing studies relying on fistulated steers.
It is suggested that the model can be applied to other contaminated
areas at or near NTS, but the results of such applications are uncertain
unless supported by valid estimates of soil ingestion rates and the
digestibility of vegetation available to grazing cattle at a specific
site.
The results of observations by Nathans, LFE Environmental Analysis
Laboratories, are reported on shape, density, color, and specific activity
of radioactive particles in "close-in" fallout.
Data on particles from
cratering events and from surface and near-surface bursts are evaluated
and classified by Nathans as part of a characterization of fallout
particles containing transuranic elements and present in the soil of
NTS.
Nathans and Francisco, LFE, presented plutonium-bearing particle isolation methods and some observations with regard to particles isolated at
LFE for the Nevada Applied Ecology Group.
Certain characteristics of
the particles after isolation are listed to indicate similarity and
variation in NTS samples undergoing analysis.
In environmental studies, development and application of techniques are
very important to increase understanding of results of sampling programs
and to assist in cutting down analytical costs.
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