198
undisturbed arcas for a period of years, al least
within the distances studied thus far. The
aseesament of fallout on natural areas, therefore,
is expressed in terms of activity per unit area.
Fallout contamination of soil is determined
fram samples taken from cither one square foot
or one quarter square foot areas depending
upon the objectives of the experiment. Soils
data may seem out of place in a symposium on
biological material. However, it will be shown
that the biological fate of radioactive fallout is
dependent to a large extent not upon total
fallout deposited in an area but wpon some
fraction of the total. Soil sampling provides us
with a method of characterizing the total fallout
against which data we can compare the biologically significant fraction of homb debris.
This latter point is exemplified in Figure 1
which compares the amount of fallout from a
10,000
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44 U SON, FRACTION)
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20
40
0
C7
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DISTANCE FROM GROUND ZERO LUKEST
single detonation on soil as compared to the
amount offallouton plant material as a function
of the distanceof the sampling site from Ground
Zerg one dav following contamination, It will
be noted that activity per unit weight of dried
plant material compares quile favorably with
theactivity contained inthe less than 44-micron
particle size fraction of soil as opposed to otal .
soil contamination. Nate also that the degree
of plant contamination in this particular case
appears to increase, or, conservatively, to stay
the sameover (he major portion of the 80 miles
distance studied.
The significance of these
observations are two-fold. First, animals
grazing in these fallout areas and feeding upon
bi,
trappedbythe plantacting as a selective fallout
collector.
10
0
Ficurn 1-~The relative degree of radioactive fallout con-
tamination. on soils and plants resulting fram a single
detonation expressed a8 a functionof the distance of the
sampling site from Ground Zero (1.
“i
i wae
these forage plants will not be ingesting gross
fallout but rather a specific fraction (the less
than 44-micron size group) which has been
|
Second, since the degree of plant
contamination tends to remain the same over a
very great distance the internal dose to animals
grazing these areas will also be similar and the
potential hazard similar over a great portion of
.
i
ACTIVE FALL-OUT
F ATE, PERSISTENCE OF RADIO
SHORT TERM BIOLOGICAL
THE SHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIRLD
the fallout pattern.
Figure 2 shows a special preparation de-
veloped for the study of the characteristics of
fallout material contaminating plants. In the
field, plant leaves are carefully placed on
gummedpaper and backed with blotter material
and dried. In the laboratory, an autoradiogram
is made which serves as a map for the location
of specific particles on the plant leaves. Detailed analysis of many of these preparations
support the conclusion that the less than 44micron diameter fallout particles are the principal source of radioactivity in forage material
samples within a period of weeks following fallout contamination. It has not been possible to
distinguish between external contamination and
metabolized fission products in range plants.
Experiments in which soil flats have been exposed to fallout and subsequently cultivated in
the greenhouse do show that fission products
(particularly Sr) are biologically available
from fallout and will be accumulated in the
plant parts [2].
Figure 3 is a photographof the dried peltof a
Mare Fork To
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Peck tar
yn .
oh
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al
1
ation and the
i
i
by leaves & ha wing the leaf prepar
retention
fallout particle
study of0
&
Fiaure 2.—A preparation for
preparation to X-ray film [1].
the
of
exposure
m
vom
diogra
ng
ee
autora
resulti
heee
t area andof
kangaroo rat, sampledfrom a fallou
from a one-half
the autoradiogram resulting
film. This
hour exposure of the pelt to X-ray
ely 12 miles
animal was collected approximat
after fallout.
from Ground Zero about 24 hours
minationis
Althoughthe degree of fallout conta
that we have
startling, it is interesting to note
burns or damfound no indication of radiation
ted from these,
age in the plants or rodents collec
burns resulting
or more distant, areas. Beta
verified, howfrom fafioutparticles have been
within 20
ever, oh livestock and deer grazing
|
miles of Ground Zero.
ts, it is
In regard to metabolizedfission produc
of the physioloindeed fortunate that, in terms
animals, relagical requirements of plants and
biological signifitively few isotopes are of reat
cance.
However, whether the biological haz-
of radioiodine or
ards are interpreted in terms
ic isotope,
radiostrontium or some other specif n prod-
other fissio
the fact remains that many
in tissues for a
ucts are apparenUly present
t contaminalimited period as aresult, of fallou
rule of radiation. As long as the fundamental
rily
biology remains “that radiation
is prima
lion
ms”, then we
a destructive force in living syste
of this material
are committed to learning more
ever its
” what
that we must “learn to live with,
.
lf-life.
biological inte
oe relationship between the
fallout to time,
and persistence of radioactive
ial within
the location of the biological mater
ior of the isothe fallout pattern, and the behav
cular fission prodtopie precursors of the parti
re-
which
nets under concern are parameters
anything
quire special consideration and defy
ut phenomeput an arbitrary divisionof the fallo
term effects.
noninto short term and long