x
3
lad
NI
* GRASS
*
= 1000 }—
=
x
© SHEEP BONE
—
x
oO
z
a
oO
>
_
Oo
°
x
a
Oo
x
x
0
*
o
|
*
oO
_|
Ou
x
oO
oO
10
x
|
‘
oO
|
10
100
CALCIUM IN SOIL BY HCI EXTRACTION (G/KG)
Fig. 5—Correlation of Sr”? in grass and sheep bone with soil calcium (normalised to 5000 pc /m? in soil).
4.3 Sr® in Grass
In the autumn of 1956 a series of measurements was madeof the Sr®/Sr*° ratio in grass at
Chilton, near Harwell. Grass samples (accumulated growth) were taken at monthly intervals
and rain was also collected during the month previous to each grass sample. The Sr® and sr*°
activities were measured, and the Sr®/sr*° ratio at the time of sampling worked out. These re-
sults are shown in Table 3. The Sr®/Sr*® ratio in the soil was also estimated, by numericalintegration of the monthly fallout of Sr® and Sr®”. +
Table 3— Sr®®/sr®” RATIOS IN GRASS,
RAIN, AND SOIL AT CHILTON
sr®9/sr** ratio
eoVO7O0O——o—eeeeeeeO
Date
Grass
Rain
Soil
Oct. 5, 1956
Dec. 3, 1956
22
15
40
28
2.4
2.2
Jan. 1, 1957
Feb. 1, 1957
Mar, 1, 1957
1G
13
12
19
17
15
2.3
2.3
2.1
The Sr®/sr* ratio in rain decreased from 40:1 to 15:1 during the period of these measurements but the calculated soil ratio declined only from 2.4:1 to 2.1:1, because of the effect
of build-up and radioactive decay. The Sr® /sr*? ratio in grass was on each occasion intermediate between that of rain and of soil.
“For this purpose results on the Sr® and Sr™ content of rain at Milford Haven due to Osmond (1957)
were used. This was necessary because the Chilton results did not extend far enough back. Over the
period during which the Sr®*/sr*° ratio from both stations was available, there was good agreement between
them.
216