CONTROLLED ENVIRONMENTAL RADIOIODINE TESTS
831
significantly higher for test 2. This suggests that the meteorological
factors were different enough between the two tests to influence deposition rates. However, at present, no definite relations to the friction
velocity and the mean wind speed have >een found.
Half-life on Grass
In the first test no specific area was used to measurethe half-life
on the grass. The daily samples that were taken to measure the activity consumed by cows were used to develop a half-life figure. This
turned out to be between three and four days, whereas in the second
test a plot was established which showed the half-life to be between
five and six days. This range agrees better with the literature. The
method used during the first test was used as a check during the sec-
ond test. With this system the half-life was between four and five days.
Figure 9 shows all three results. The reasons for the disagreements
have not been determined.
>
tTrrtrttrt ttt! TH
mom
80 F—-*S
arco! | GRAZING DATA 7
aTEST 2 GRAZING DATA _|
P A
eT
——
“oo
BY
o
~
Qo
=_|
OTEST 2 SINGLE PLOT)
~
_—
°
>
=
20
——
oe 9
\
“NaN
=
Ww
°
<
4
=
> 10 =
t—
zZ
uw
8
—_
Ty2=5.50 DAYS
Na \
=e
Oo
—
—
\. “ a,
o\
‘o
Tiv2 =4.25 DAYS
48
6
4
NN
\ oN
\ ~~
o
7
~~]
ud
N\
No
‘
Ne
z 6h
T1/2=3-50 DAYS —_.
2
CO
—
—
2
4
12
10
8
6
DECAY TIME, DAYS
14
16
Fig. 9—Half-life of #'I on grass.
G2r