Results from plant root uptake experiments, under glasshouse
conditions, support this concept.
Also, the annual precipitation
is higher at the Roller Coaster sites than at other study sites.
5.
The 239-240
Pu inventory estimates indicate that the standing
vegetation contributes a rather insignificant portion of the
total contaminant present in these aged fallout areas.
Four plant uptake experiments have been conducted under glasshouse
conditions to determine the significance of root uptake of 239-2405,
and 241 Am by alfalfa, barley, soybeans, and wheat.
Radiochemical
analysis has been completed for the barley samples (the other plant
samples await analysis).
Results showed discrimination factors
ranging from 1074 to 107? for 239-240), uptake through roots.
Pu/Am
ratios for soil and plant samples also showed greater root uptake of
241an
239-240
the ingrowth product,
, relative to
Pu from the aged
source materials.
EXISTING AND ANTICIPATED PROBLEMS
It has been desirous during the past three years of sample collection
to obtain information on the annual plant species.
period, however,
During this
the environmental conditions have been unfavorable
for the production of annual plants in the study areas.
Again this
year, poor production of winter annuals is probable (those which
germinate in late fall and winter and are so spectacular when flower-
ing during April and May).
Because of the late spring rains, there
may be adequate summer annuals, grasses, and forbs to collect some
samples for radiochemical analysis.
The supposition that the activity levels found on vegetation may be
attributed largely to superficial contamination is based primarily
upon two assumptions:
(1) the residence particulate material is
resuspendable and of small particle size (fallout particles entrapped
upon plant foliage from aboveground nuclear testing generally ranged
below 44-micron diameter), and (2) results from controlled plant
33