3e
DISCUSSION OF SURVFY DATA
The ratio of the radioactivity in planxton to that in
water ona basis of equal weights is highly variable from station to station and from collection date to collection date.
Some of the variability
water sample values.
is probably due to inaccuracies
in
A single value for water is probably less
reliable than a single value for plankton because of the method
of sampling and the lower level of activity in the water; when
the water value ts based on the sverage of several observations
the comperison is fairly reliatle, but a compsrison based on a
single water value is less reliable.
The average of ratios for ™
all stations of the Marsh survey wes 2500 (minimum 29,
18,000).
maximum
The average ratios for the Walton and Troll surveys
were 7,000 and 300 respectively.
Several factors may enter into the reduction of the plankton-water ratio with time.
One factor may be that selective up-
take by the plankton is less evident from relatively fresh fallout material, where & wide spectrum of radioisotopes is avail-
able.
A decreasing ratio with time after fallout, evident from
comparing the Walton, Marsh and Troll date,
bility.
supports this possi-
Furthermore, the western stations (14 - 42) of the
Marsh survey, which would tend to have older fallout materia POF ARCH
than the eastern stations,
have a lower ratio of plankton ac-
tivity to water activity than do the eastern stations.
The
values and their standard errors are 475 * 98 and 3716 2 754
respeotively.
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