ship Shunkotsu~Maru determined the amounts of radioactivity in
the sea water and marine life.
The maximum sea water activity* found during the
Japanese expedition was about 91,000 d/min/liter, 450 km
west of Bikini on June 21,
1954.
Over 1000 d/min/liter
was found as far as 2000 km WNW of Bikini.
the Japanese
scientists,
this activity was
According to
in solution,
Since it passed through a fine filter paper.
In addition,
samples taken in depth showed activity was present at
some locations down several hundred meters.
(NYO-4656)
After consulting the Japanese data it was decided to attempt
to measure the residual activity remaining in the Pacific Ocean
a year after its deposition.
Operation Troll on the U.S.
Coast
Guard Cutter Taney covered a course of 17,419 miles between
February 25 and May 3,
1955.
The conclusions drawn from the data gathered and edited
by Harley (NYO-4656) are summarized as follows:
1.
Sea water and plankton samples show the existence
of widespread low-level activity in the Pacific Ocean.
Water activity ranged from 0-570 d/min/liter and plankton
from 3-140 d/min/g wet weight.
2.
There is some concentration of the activity in
the main current
Current.
streams,
such as the North Equatorial
The highest activity was off the coast of Luzon,
averaging 190 d/min/liter down to 600 m (April 1,
3.
*
1955).
Analyses of fish indicate no activity approaching
Measurements were made by coprecipitation with ferric hydroxide
This procedure eliminates the natural K40
and barium sulfate.
activity and loses certain fission products,
some of the Ru and Nb.
such as Cs and