PREDICTION OF RADIONUCLIDE DEPOSITION
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Fig. 3—Comparison between the predicted (C) and the measured (A)
depositions of gross beta radioactivity for four-week sampling periods
at Tecumseh, Mich.
DISCUSSION
Admittedly, the model was used in an arbitrary fashion to predict
the deposition on the Tecumseh farm. Itcertaiply ie unuesirable to have
to keep the model current with an extensive program of measurements
just to be able to predict the deposition at one location. In the following
discussion an attempt is made to show that the model in its general
form may be widely applicable. On the other hand, it will be shown that
its applicability to specific situations is limited because at the present
time the behavior of certain terms in the model cannot be predicted.
Applicability
First of all, with the model selected it was assumed that radioac-
tivity is washed from the atmosphere exponentially with rainfall. Since
the rainfall collected during a four-week period isthe sum of individual
rainfalls, one might expect to find an exponential relation between the
deposition and the amount of rainfall on, say, a daily basis. In the literature on this subject, the relation that is repeated again and again is
the apparently logarithmic one between the radioactivity concentration
in rain and the amount of daily rainfall. This relation has been reported
in Norway® from 1956 to 1959, in Great Britain’ in 1956 and 1957, and
in Russia.’ The period during which the relation was found in Russia
was not reported, but it probably was in 1960 and/or 1961. Figure 4
shows the relation plotted logarithmically. The points in Fig. 4 were
determined by dividing the daily rain concentrations by their respective monthly concentration, averaging the data over several months
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