131CS PASSAGE FROM PRECIPITATION TO MILK
707
individual rains and accompanying wind and ground dust storms. The
degree to which forage covers the ground also represents a large
factor in determining the efficiency of deposition.
Comparison between the '’Cs concentration of milk and rainfall
1)
(Fig.
activity
a
a
indicated that milk produced by
A
T
cows on pasture
T
t
——
PASTURE HERD
-
ot
so
o
4
--- 3x COWS
See
|
7
—
frre BULK MILK
oe
a
io ==
i:
~
O
w
=
T
S
zc
A
T
=
<t
\
,
ae
{|
\.
Litt
0
20
40
tf
ty
40
pt
80
JAN. 1, 1963
tt
100
a
~
é
4
Ww
4
3
o
4
a
LL
1
7
T
10!
>
die =
wa
UO
<
ee
ft EE
)6©6120)0«140
MAY 1, 1943
«#3160
BEER
PEE
180
200
JUNE 13, 1963
Sy
220
260
Z
=
[
240
a
4
280
SEPT. 17, 1963
TIME, DAYS
Fig. 1—Concentrations of "Cs in milk produced by cows on pasture,
cows fed ina dry lot (bulk milk), and high-milk-producing cows milked
three times a day and fed in a dry lot (3x) related to corresponding
rainjall activity, 1963.
responded almost immediately to increases in forage activity, except
for the period around day 240, at which time the herd was largely
dependent upon hay for feed rather than on pasture. This response
does not agree with the statement that ‘“‘peak concentrations of cesium137 in milk have appeared about one month after peak fallout rates.’”
Feed-Milk Transfer of 137Cs
Dairy cattle normally are fed large amounts of hay and/or pasture,
both of which may contain much higher levels of fallout ‘Cs than
those found in grains, which are the other major components of the
diet. It is much easier to obtain reliable estimates of the transfer
coefficient between feeds and milk than between precipitation and feeds
because experiments to test the latter can bedesigned at will whereas,
for the former, experiments are dependent upon the vagaries of the
weather.
An average value for the ratio of '°’Cs contained in feed which
would
be
found in milk would be most useful for prediction of the
activity in milk expected from cows that had grazed on contaminated