regard to plutonium absorption, the minimum and maximum solubilities were
0.49% and 13.5% for plutonium-238. For plutonium-239, they were 0.14% and
0.76%.
During the spring and midsummer trials, a large increase in plutonium solubility
was observed; this increase was accompanied by a marked reduction in total
plutonium concentration in the rumen contents.
Analyses of the vegetal compo-
sition of the rumen contents indicated a reduction in the proportion of Eurotta
Zanata and an increase in the proportion of Oryzopsis hymenotdes (Indian
ricegrass) or Sttanion jubatwn (squirreltail grass). The minimum and maximum
solubilities in the simulated duodenum were 95.1% and 96.6% for plutonium-238;
for plutonium-239, they were 44.5% and 90.02.
Boyd et al.
(1974) reportedthat samples of a polydisperse aerosol of 24 1am0.
treated successively at 300°
C and 1050
C were relatively insoluble with a
fractional dissolution rate of less than 107" per day in a standard solvent
prepared to simulate the chemical constituents of lung fluid.
Repeatedly the
dissolution rate proved to be inversely related to the total phosphate concentration in the standard solvent.
Raabe et al. (1974) collected samples of aerosols present in a glove box
during a plutonium oxide and uranium oxide powder mixing operation. Solubility
studies were run at 37° C using lung fluid simulant with and without the
phosphate component.
Preliminary indications were that the cumulative plutonium
solubility was higher in the standard solvent, both with and without phosphate,
than was observed for laboratory aerosols of *39Pu0,.
The cumulative solubility
of americium in the phosphate-free solvent was at least two orders of magnitude
higher than that of plutonium, but was much less in the solvent with phosphate.
MATERIALS AND METHODS
The procedure described briefly here is essentially that of Barth (1975).
Rumen-fistulated Hereford cattle were allowed to graze periodically in the
inner enclosure and nonfistulated cattle were allowed to grave continually in
the outer enclosure of Area 13 ot the Nevada Test Site (Smith, 1975).
The
inner enclosure directly surrounds the ground zero of a high-explosive detonation of an atomic device during a safety test. The outer enclosure, a less
heavily contaminated area, completely surrounds the inner enclosure, and most
of it is located a greater distance downwind from ground zero than the inner
enclosure.
Area 13 has been described by Tamura (1975).
Samples of whole rumen contents were collected from the fistulated cattle
following a 48-hour grazing period.
Samples were collected from the nonfistulated cattle at the time of slaughter.
Samples of whole rumen contents were added to four Erlenmeyer digestion flasks
with simulated abomasal juice consisting of HCl and pepsin, and the pH was
adjusted to 3.0. Abomasal incubation in a water bath at 39.5 was allowed to
122
If: