FINDINGS TO DATE
The presently available data indicate that the qualitative response
in tn vitro bovine gastrointestinal tract of field-ingested plutonium,
of uncertain chemical form, was in most cases similar to that of the
plutonium-238 nitrate, plutonium-238 citrate complex, and plutonium238 dioxide used in earlier in vitro studies.
Increased plutonium
solubility was generally noted when the pH was changed from 3.0 to
4.5.
These respective pH values characterize a primary chemical
difference between. abomasal and duodenal contents.
This was followed
by a further increase after the addition of bile and enzymes and
adjustment of the pH to 6.0 to simulate the upper jejunum.
This
increase is attributable to the action of bile.
In most cases,
there was a considerable quantitative difference in
the solubility of field-ingested plutonium and plutonium-238 dioxide
used in earlier studies.
Field-ingested plutonium-238 was found to be generally more soluble
than field-ingested plutonium-239 in these fluids.
The differences
were, however, quite variable.
During the late summer,
fall,
and winter trials,
low plutonium solu-
bilities were observed, accompanied by comparatively high concentrations of plutonium in the rumen contents.
An analysis of the vegetal
composition of the rumen contents indicated that this was associated
with high levels of Furotta lanata
(winter fat).
The minimum and
maximum solubilities in the simulated duodenum, which is presently
believed to be the most important stage, were 0.49 and 13.5% for
plutonium-238.
For flutonium-239, they were 0.14 and 0.76%.
During the spring and midsummer trials, a large increase in plutonium
solubility was observed, which was accompanied by a marked reduction
in total plutonium concentration in the rumen contents.
Analyses of
the vegetal composition of the rumen contents indicated a reduction
in the proportion of Eurotta lanata and an increase in the proportion
Of Oryzopsts hymenotdes
reltail grass).
(Indian ricegrass) or Sttanion jubatum (squir-
The minimum and maximum solubilities in the simulated
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