Local differences in dose rates at one inch
Survey meter readings were also taken at one inch above t
ground with the beta shield both open and closed.
There was n
apparent correlation between these readings and the gamma dose
rate readings at three feet,
except in a very general way, but
such readings were useful in selecting areas from which to sam
and indicated local distribution of the activity.
For example
when measurements were made one inch over the ground with the
shield open in 1959, the levels were higher after the litter
was removed from the soil and there were markedly higher level
of activity over areas covered with soil algae than over bare
sand.
Attempts also were made with a survey meter to determin
local differences in activity in trees.
This was unsuccessful
since the general levels of activity masked local effects with
the trees, even though laboratory analyses showed that the
activity in lichens and mosses collected from the bark was
several times higher than in the bare portions of the trees.
The use of survey meters to determine the vertical distributic
of activity in soil pits was impracticable due to the high bac
ground levels from surrounding contamination and the fact that
the bulk of the radioactivity was in the surface inch or less
of soil.