764
MARTIN
tl
f, fraction of ingested ®*Sr deposited in the rabbit’s skeleton
f, = fraction of ingested '°"I deposited in the rabbit’s thyroid
Ap = 0.693/T,, where T, = effective half-life of Sr or ‘I on plants
\, = 0.693/T, where T, = effective half-life of *Sr in rabbit’s
skeleton
A, = 0.693/T, where T, = effective half-life of ''I in rabbit’s
thyroid
RESULTS
Estimates of average gammadoserates, of 8§Sr concentrations in
plant samples and in the bone ash of rabbits, and of '4I concentrations
in plant samples, in the stomach contents of rabbits, and in rabbit thy-
roids are given in Tables 1 and 2. The approximate locations at which
these samples were collected are shown in Fig. 2.
The wide range of values and the relatively large standard errors
of the means given in Tables 1 and 2 indicate a high degree of appar-
ently inherent variability.* The wide range of Sr and ‘I concentrations in plant samples and in rabbit tissues or stomach contents is
partly a reflection of the wide range of initial contamination levels as
indicated by estimated gamma dose rates; but much of the inherent
variability is undoubtedly related to the probabilistic nature of the environmental and biological processes that influence the external contamination of plants and the accumulation of radionuclides in animal
tissues. The probabilistic approach to the study of food-chain kinetics
and the use of stochastic models to simulate these processes are con-
sidered in this symposium by Turner.
The results of correlation and regression analyses given in
Table 3 show that the quantitative interrelations of initial dose-rate
estimates and estimates of maximum °%Sr or '*!I concentrations in
plants and animal tissues are highly significant in spite of their inherent
variability.
As might be expected, the correlation between
initial gamma dose rates, Ry, and initial concentrations of *Sr or '!I
on plants, P,), are highly significant. The correlations and regressions
of plant contamination on maximum concentrations of **Sr in bone ash,
Bz, and of '*4I in thyroids, A;, are also highly significant. The some-
what higher correlation between '*/I concentrations in stomach contents, S), and in thyroids, A;, suggests some difference between the
plants collected for radiochemical analyses and those actually eaten
by the rabbits in the Sedan fallout field.
*Since the standard deviations (= sx Vn) are large in relation to the means,
the frequency distributions of these variates are sharply skewed. Preliminary
investigations indicate that they may be lognormal rather than normal.
+See paper by Frederick B. Turner, this volume.