NAEG studies to gain information concerning the influence of soil microbial activities on the bioavailability and biotransport of transuranics
in desert environments continue. Au and Beckert suggest that the biomass
figure for fungal and bacterial biomasses should provide some understanding of potential microbial activities in Nevada Test Site soils. Of
In fact, the
course, many variables enter into such determinations.
been observed
have
soils
desert
of
soil fungal and bacterial populations
to be very high and diversified, even in locations without plants.
Experiments using Aspergillus ntger are under way to determine whether
the availability and transfer of plutonium are increased during successive
generations of soil microbial growth.
G.I. tract studies with fistulated steers grazing in Area 13 continue.
The relative solubility and concentrations of plutonium and americium in
rumen samples collected under field conditions in Area 13 vary, depending
on several factors discussed by Barth:
season, predominant species
ingested, vegetative stage of growth, presence of fruiting involucres on
Eurotta lanata, grazing intensity, and distance of grazing area from
ground zero.
Future plans include combined studies with microorganisms
and artificial rumen systems.
Investigation of differences between
biological availability of biologically incorporated plutonium and
nonbiologically available plutonium, and study of whether biological
organic binding protects plutonium from being removed from solution by
competing chemical reactions are among studies planned.
A comparison was made of data from cattle grazing in Area 13, NTS (a
plutonium-contaminated safety-shot area), with data from cattle grazed
in the area of the Rocky Flats Plant in Jefferson County, Colorado.
Smith reported on Area 13 cattle, reflecting gonad concentrations equal
to that of femurs and significantly higher than muscle.
Similar relative
tissue concentrations were found in the Rocky Flats cattle data, although
generally the concentrations were less than those reported for Area 13
cattle.
Smith also reported that concentrations of plutonium in the
femurs of young animals were slightly higher than concentrations in
adult animals.
Holstein dairy cows were used to measure rate of passage of sand particles
tagged with L4lce, 85sr, °4Mn, or 46so, through the G.I. tract.
Patzer,
Sutton, and Potter performed the study to determine whether passage rate
of particles through the bovine G.I. tract is related to size. Results
indicated significant variance with particle size, with measurements of
up to 12 days for passage of 90% of the particles in feces.
Comparisons between the biological transport of plutonium and curium in
dairy goats were studied by Sutton et aZ.
Intravenous or oral doses of
curium-243 chloride were administered to 6 lactating goats, followed by
milk, urine, fecal, and blood sampling for 6 days.
Approximately 2% of
the IV dose was transferred to milk during the 6-day period.
Urine and
feces averaged more than 4% of the administered IV dose. The oral dose
results indicated excretion in feces of all but less than 1% of the
administered dose, and nondetectable quantities in milk, urine, and
blood.
Compared with plutonium previously administered (IV) to a single
319