bias in the determination of 261
standard carrier dissolution was used
Although the number of samples
to process these samples.
compared is a relatively small frac-
were primarily for 706). and Pu.
tion of the total analyzed, it appears
Americium-241 was determined in three
that the standard vegetation aliquots
of
(3 g) may underestimate the 239,240),
are compared in Table 8.
concentrations by 7 percent and the
241
;
Am concentrations by as much as
of A to B samples is presented for
16 percent.
isotopic concentrations.
the samples.
Analyses
Measurement results
The ratio
each of the measured atom ratios and
Since the compared
OQOuoted
samples were either litter or roots,
statistics are derived from the pro-
sample inhomogeneity is the likely
pagation of errors.
source of these apparent biases.
geneity is evidenced by the excellent
However, it is also possible that
agreement in the 239, 240, and 90...
these biases may be indicative of an
concentrations from both Bikini and
error resulting from surface con-
Eneu.
tamination of vegetation so that
some spread among the individual
the results may not be a true
data points but are reproducible to
measure of the isotopic uptake by
within 11 percent at a mean of unity.
the plant.
This spread is but another example of
Results for
Sample homo-
Alo exhibit
the inherent difficulty of minor isotopic measurement by mass spectroSAMPLE HOMOGENEITY
metry.
MCL received duplicate samples
Th e 241 iy comparison,
Limited to three points,
though
also shows
from 17 large-volume soil specimens.
no significant bias.
The question to be answered was
these samples indicates that separate
whether separate samples from a large
aliquots of soil can be expected to
specimen of finely divided soil could
show reproducible results
give reproducible results.
the errors presented in Table 8.
The
Comparison of
to within
Data Comparison
MEASUREMENT OF 244 CONCENTRATION —
metry were selected for
ALPHA VS GAMMA DETECTION
chemistry analysis.
241 wet—
In each of
the
624 samples of soil, vegetation, and
animal tissue,
Approximately 13 percent of the
through either a positive gamma
624 samples assayed by gamma spectro-~15L
|
9010051.
tam was quantified