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It is desirable ta measure the rate of fallout, its accumulation,
and the atmaspheric reservoir of material yet to be deposited on earth's
surface.
The samples currently taken for this program include soils,
sea water, collections of fallout in open pots and on gummed film, and
collections of atmospheric dust on filters.
Soils
A soil sample can represent the accumulated fallout at any given
location.
There are many criteria to bea met to insure. that a soil
semple is representative.
Anideal sampling site is considered to be
an open, level area, undisturbed by cultivation and_cavered by grass or
simple vegetation covering to immobilize the surface.
Drainage slopes,
silted areas or other wmusualdrainageconditions should be avoided.
Samples are collected with soilaugers to give definite areas and depths.
The most common division of sampling is to.collect the top two inches
and the two to six inch layer separately.
The known area and the
measured weight of sample allow the Sr-90 measurements to be converted
to terms of millicuries per square mile.
Renoval of Sr-90 from a soil sample is a difficult problen because
the relatively low levels of activity currently found reguire use of
very large semples.
At present two to four pounds of sail are taken
for analysis and this makes the usualprocedure of caupletely dissolving
the soil by fusion a practical impossibility.
Thus although the fusion
technique is the only method certain to remove all Sr-90 fram the soil
it has been necessary to study other methods for Sr-90 extraction.
After considerable experimentstion, procedures that agree satisfactorily
with the fusion technique have been developed.
Tnese involve the ex-
traction of the Sr-90 by electrodialysis or by hydrochloric acid leaching
poe
é: ARCHIVES
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