RAINOUT RELATIONS ON SAMPLING NETWORKS
511
Measurements of ®Sr and Sr were made by Isotopes, Inc.,
utilizing techniques developed in their laboratories.’ Walton et al.‘
indicate that the overall error of the routine radiochemical analysis
was +7 and +9% for “Sr and Sr, respectively.
SPATIAL VARIABILITY OF RAINWATER RADIOACTIVITY
An investigation was made of the spatial variability of the con-
centration and deposition of gross beta rainout and "Sr and "Sr rainout
on
the sampling networks. This investigation was made to obtain
quantitative
data
on
the probable variability of radioactivity ona
mesoscale in convective storms and to determine the relation between
the relative variability of radioactivity and rainfall. The relative
variability was obtained by the simple method of Conrad and Pollak®
in which it is defined by
AD
V= 100
where V is the relative variability in percent, M is the mean of the
sample, and AD is the average deviation from the mean. The relative
variability was chosen as the variability parameter so that factors
measured in dissimilar
could be compared. The
cause of the simplicity
persion about the mean
Study.
units, such as concentration and deposition,
Conrad and Pollak method was selected beof calculation and because the average diswas considered a desirable statistic for this
The relative variability of beta concentration, beta deposition, and
storm rainfall was calculated for eight storms on the Boneyard network and seven storms on the Kaskaskia networkin 1962. Five samples
were obtained in each of the Kaskaskia storms and five or six samples
in each of the Boneyard storms. Since the two networks are nearly
equal in area, the data were combined to obtain a larger sample upon
which to establish trends or relations. The rainfall variability was
based upon observations at the same points at which the rainwater
samples were taken.
The relative variability of gross beta radioactivity and storm
rainfall for each storm is presented in Table 1, along with data on
storm mean rainfall. In Table 1 beta concentration refers to the
quantity of radioactive material per unit volume of rainwater. Beta
deposition is the quantity of radioactive material deposited per unit
area. This is determined by the product of the concentration of radioactive material and the rainfall depth. On the average, the relative
variability of gross beta radioactivity was nearly twice that of storm
oO)