34
radionuclides in old soils is as follows, in order of greatest
penetration:
est37, sr?°, spt?5 | co°®, zn°>, or 44 py 144 Eut?>
and probably other rare earths.
In the young soils,
consisting
almost entirely of parent material, the positions of cs*3? and
spt?5 are reversed and the other radionuclides appear to be
more completely retained in the surface algal crust.
The maxi-
mum concentration of fallout radionuclides remains at the soil
surface, a few inches or less in depth, except in areas where
there has been erosion.
In the eroded areas large particles
containing both soil algae and radionuclides are randomly distributed to a depth of a few inches.
There is some horizontal movement of radionuclides but
such movement appears to be very localized and thus is of little
consequence in the overall picture of distribution.
@st37 and sr?° are the principal radionuclides entering a
cycle within the soil-plant system.
Any loss from this system
appears to be small (a fraction of one per cent per year), but
a definite conclusion can not be drawn from the data.