AECD-3446
-72-
Autoradiographs of Portulaca oleracea plants collected from selected dis”
tances from the bomb crater on Engebi, Aomon and Runit Islands are shown in
Figures 2, 3, and 4 respectively.
They show graphically the sametype of infor. #9
mation as is contained in Table 3. The intensity of the general background act;
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within the tissues, due largely to ca‘, decreases with distance from the crates
The same trend is evident in the autoradiographs from all three islands,
at random over the plant.
As the distance from the crater decreases the intens{
of the individual spots does not increase accordingly,
This indicates a rather wigs
particulate distribution of high activity fission products with a more limited but
more uniform occurrence of cat,
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The limits of the ca*5 zone should correspond "i.
with the maximum range of neutrons in air and the concentration with the neutrog ‘
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flux, unless scattering of ca*t® coral sand by mechanical means has occurred.
The presence of ca? in the tissues of the plants adjacent to the bomb
crater is considered to be well established,
"
The approximate concentration, hows
ever, was not sufficient to cause more than 734 d/m/gm of fresh tissue! (or per
mip
cc of volume) on March 14, 1950, in those plants only 30 yards from the center of
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the bomb crater on Runit Island, The total activity in and upon the plant collected 3
at 50 yards from the tower base (#575, Portulaca oleracea, see Figure 4) amounteé to 676 d/min/gm fresh material (assuming 20% dry matter) on May 29, 1950.
cannot be corrected for decay since the half-life is unknown,
Ths . a
Assuming cats made- Re
up an appreciable amountof the activity, the corrected figure might be near 1500
d/min/gm fresh material.
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Activity, then, is not excessively high.
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Radiation values are low enough to warrant a search for another contributiag °
cause for thé tissuedamage and death of-plants-in this-zone, -A-reference to Table5
will show the total calcium content of plants collected at 30 yards (Runit) to be oaly
9.3 mg Ca/gm dry matter, while at 200 yards the plants contained 47.5 mg Ca/noe
dry matter, This latter figure corresponds to the normal calcium content of msӴ y
plants.
It is then evident that the plants near the crater are suffering from @ se
:
calcium deficiency. Experimentally grown plants do not survive at lesser calclumm |e
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‘Caleulated from data in Table 3 and assuming 20% dry matter content in the frost
tissue and using scavenging Procedure I, which gives the highest results.
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