21
The radionuclide content of leachates collected in the field
agrees with these results (Cole et al. 1961).
lLeachates
from
young soil contained only spi?5 and sr?°, while leachates from
better developed soils contained mainly sr?? and cgt37, with
traces of other gamma-emitters.
Depth Gradient of sr?
The relative sr?° content of depth increments of the two
soil types is given in Table Iv,
the amount of sx? with depth,
There is a rapid decrease in
and the differences in sr?? con-
tent between soils probably are not significant.
The extreme
values from the results of sr?° analyses of subsamples of replicate samples taken from small areas differ by a factor of more
than ten (Table
II).
It is likely that the variability is
due largely to the spotty nature of the distribution of the
fallout radionuclides, which is evident in the radioautographs
discussed below and from X-ray films that were exposed at the
soil surface and just below the surface (Fig. 11), and to small
differences in the characteristics of the soil within a single
soil type.
Sampling by 1/8-inch increments in 1959 of an undisturbed
old soil,
(Fig.
4
and Table
I)
on Rongelap Island indicates
a gradient of sr?° levels in the top inch of soil (Table v).
The levels in the second inch are about one tenth those in the