Tne alfaifa sampies ranged from 4.3 to 21 Sunshine Units.
Unit
(S.U.) is defined_ss one micro-microcurle (10°~~
Unit(S.U.)isdef:
ium~
am
icium.
strontium-90pergramof
ecalci
12
A Sunsnine
curie) of
The topPp inch of the soil sampl
ples
averaged 12 S.U., and the 1" - 6" depth of soil averaged 4.0 8.U.
There was no correlation between the strontium-90 and calcium uptake
and the plant concentration for strontium-90 was much higher than anticipated from the soil analyses.
It vas concluded that the strontium-90
content of alfalfa was largely due to direct fall-out on the plant
rather than absorption of strontium-90 from the soil by the roots.
“he
Lamont Laboratory analyzed corn leaves and obtained 0.5 S.U. from a 50%
HCl leachate and less than 0.05 S.U. from the plant after leaching, demonstrating that most of the activity was on the surface of the plant and
had not been taken up by root absorption from the soil.
These findings make it impossible to project current soil and
bone deposition data because the non-recurring initial fall-out contamination is obscuring the biological uptake phenomena.
The problem
of the fraction of strontium-90 still unaccounted for also becomes more
important because of these findings.
If the strontium-90 still unac-
counted for should be made available by descending to the earth's surface
over a long period of time, there exists a mechanism for short circuiting the early parts of the biospheric chain and thereby increasing the
final deposition of strontium-90 in bone over that expected from soil
analyses.
In other words, the root's preferential selectivity of celcium
over strontium, as indicated previously, will not be operative for that
fraction of the strontium-90 which falls out on the plants and is
mechanically transported to the next step of the chain leading ultimately to the bones of humans.
From the point of view of human hazard, the major animal pathway of significance is that which deposits strontium-90 in milk and milk
products.
In certain areas of the world where, for example, small
animals such as fish are eaten whole, this would be a modifying factor.
In this report it will be considered that the cow and cow's milk con-
105