One important link in the strontium-90 food chain is the
pathway through plants.
The significance of the amount of strontium-90
uptake by plants relates to its transport and final deposition in the
bones of humans.
There are many complicated mechanisms concerned in
the soil-plant relationship which are still to be evaluated.
These,
when they are worked out, will make possible the determination of the
ultimate significance of a particular level of soil contamination at
a particular time.
The strontium/calcium ratio for plant root uptake in nutrient
solutions is 1.0.
The U.S. Department of Agriculture studies0/» how-
ever, indicate that in American soils the average uptake departs from
this experimental value.
Menzel has calculated a factor of ky = 0.36
on the basis of
_ tSe/ee) plant
kr *
Sr/Ca)
soil
The available calcium in the soil determines the amount of
strontium-90 taken up by the plant.
Menzel has shown that over a
range of 0.7 to 48 milli-equivalents of calcium per 100 gms of soil,
the strontium-90 uptake wasinversely proportional to the amount |
of calciumpresent. =
Some experiments have been conducted which relate uptake of
strontium-90 by plants to soil depth distribution of this contaminant.
Here root depth is the critical parameter.
The over-all significance
of this principle will depend upon calculations relating actual depth
‘of contamination to root’ depths for various food crops.
The total
problem, however, has not yet reached a degree of sophistication which
would render such analysis fruitful.
The SUNSHINE Project data contain correlated sets of alfalfa
and soil samples from the Chicago milk shed, analyzed for strontium-90.
4o/ Menzel, R.G. and Brown, I.C., Leaching of Fall-out and Plant
Uptake of Fall-out.
March-April 19953.
Bi-monthly Report, U.S. Dept. of Agriculture,
104