a
lho, ~ The Carrier was added to the sample as
in the previous procedure. 10mg of Ce, 5 mg of La,
20 mg of Zr, and 10 mg of Ru were added to 20 liters
sea water. The rate earth fraction, separated from
alkaline earth elements, was dissolved in hydrochloric
acid and precipitated as an oxalate and separated
from Zr and Ru. The rare earth oxalate was ignited
and dissolved in nitric acid and adjusted toa 9 M
HNO3z solution. Ce was oxidized to quadrivalent by
sodium bromate and extracted by MIBK. After the MIBK
layer was washed with a 9 M HNO, solution containing
a few drops of 2 M NaBrO3, Ce was stripped by water
containing 3 drops of hydrogen perioxide, precipitated
as an oxalate, filtered by filter paper then counted
- by a dg gas flow counter.
likCe was counted after M41ce completely decayed
and its effect on the count of 144Ce became negligible.
Counting efficiency for each nuclide was determined
- by measuring the respective standard at the same
geometry and condition as the sample.
3. Results
The results obtained are givenin Table 1.
The locations of sea water sampling are shown in Fig 1.
We can divide the locations to three groups, that is,
Stations 23, 25, 27 and 29 belong to the South
Equatorial current, Stations 31 and 35 to the Equatorial
Counter Current, and Stations 39, 41 and 43 to the
North Equatorial Current.
db, Ihere are con
90sr radioactivity ab
increase fro
tends one vertical
r
that of 90Sr and the
a
ve
abo
radioactivity
r
Cur
l
ria
ato
South Equ
Equatorial Current re
decreases abruptly fr
Ce at
The value of
but
ge,
lar
abnormally
.
no
are
on
locati
l
ica
log
bio
effect of
5, Relation between r
Fig. 7 shows tha
radioactivity and dis
linear function. Thi
supplied to the marin
to a deeper layer by
in the same manner as
coincides with the ch
of 20Sr in sea water
amounts of the stable
there is no Linear re
activity and dissolve
is due to the unstabi
sea water.
6. UAce to 2Sr
4. Relation between radioactivity and water temperature.
In the South Equ
Lice /P0sr above the
the thermocline is from 15° to 25°C.
to indicate that 144c
As is shown in Fig. 6, the temperature range of
These temperature
boundaries are indicated by dotted lines in Fig. 6.
ae Above the thermocline, there are differences
between the radioactivities of 79Sr, 13s and MAce
in the South Equatorial, Counter and North Equatorial
Gurrents. However, there is no difference between
them, below the thermocline.
those of below the th
and suffers the effec
its motion in sea wat
deeper layer faster t