Gross f-activity of Sea water
*Masaru SHIOZAnT
2. Experiments and Measurements
i
About 5 liters of sea water were collected at each
station using a 10 liter polyethylene bucket or surface
water sampler made of rubber.
As soon as the sample
was taken, concentrated hydruchloric acid was added
at a rate of 1 ml of yo, per Liter of sea water.
‘2 liter portion of the acidified sea water was
A
transferred to a 3 liter glass beaker, then 1O mg of
Fe3+ and 10 mg of Bat added as carriers and 3 g of
ammonium chloride added to each sample as the buffer
agent. After the Sample was neutralized with a 1:1
ammonium hydroxide solution using phenolphthalein as
the internal indicator, it was boiled. Precipitetes of
barium sulfate and ferric hydroxide were completely
settled, then filtered on filter paper (2.5 cm diameter).
The precipitates on the filter paper were dried under
an infrared Lamp then counted with a GM counter.
“Gounting efficiency was determined by comparing the
count rate of the Ra-D, EF standard at the same geometry
as the sample with its predetermined disintegrating rate.
The values of 32.8 and 35.2% were obtained.
Mica window
thickness of the GM counter was 1.4 - 1.6 mg/em2 and
the background count 12 cpm when the GM tube was shielded
by 5 cm of lead.
gre
2- Results
- Results obtained are shown in Table 1.
_, Horizontal distribution of gross f-activity of
surface water is shown in Fig.1. Relation between
Bross f-activity of surface water and location represented
by latitude are shown in Fig,2. In the South Equatorial
Current area, gross f&-activity is relatively low in
comparison with other regions.
. In the Equatorial Counter Current region, radioactivity increases abruptly, however, there is no
difference of gross #- activity between the Equatorial
Counter Current and North Equatorial Current.
The trend of distribution of gross f-activity is
_ *Hydrographic Division,
Maritime Safety Board Agency.
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