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16 REPLY REPEA
U. 5. NAVAL RADIOLOGICAL DEFENSE LABORATORY to
vine,
SAN FRANCISCO 24. CALIFORNIA
901-107
HWW: as
AIR MAIL
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PA CAN ASS
Dr. W. F. Libby
U.S. Atomic Emergy Commission
Washington 25, D.C.
Dear Dr. Libby:
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In accordance with your request of 26 December 1956, Dr. 4.V.
Weiss has as
celcium and Sr’
semples of Marahall Island soil for exchangeable
and has computed the sunshine wits on this basis.
Seven soils from different islands in the northern Marshall
group were assayed.
The samples were 6" x 6" surface soils and
ranged in character from calcareous perticulate to rich loam.
Exchangeable calcius was determined by the method of Smith and
Blume (So1l Sei. 77 9, (1954).
Samples of #01] varying in weight
from 1-2 pounds were extracted with 500 ml of the equilibration
solution.
In estimating cats , extracts of the exposed soils were scavenged
with ferric hydroxide prior to omlate precipitation to eliminate
interfering nuclides, srX, which would be expected to follow cad, ‘
was insufficient in concentration to interfere with accurate counting
measurements, as evidenced by the identical aluminum absorption curves
obtained with the extracts and an authentic sample of CaS.
The date are shown in the accampenying table.
Previous analyses
on these soil types showed that the calcius content ranged from 23-35
per cent. Clearly, exchangeable calcium represents only a small frection of the total.
it was interesting to note that the sunshine units expressed on
the basis of exchangeable calcium are without exception considerably
reater than that of plants recovered from the respective islands
for. USNRDL Report &55 (1956)).
This observation implies that a sizeable fraction of SrO is in
&n unavailable form:pr that the distribution of this rediocelement in
the soil is inhomogeneous and only a small part is translocated to the
ares of the root systen.
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