Co
As Chilton (APA-38) crossed the sill of Enyu Channel, it waa immediately ob-
served that the water, instead of being marvelously clear as it had been when the
first wits of Joint Task Force ONE entered the lagoon, was as opaque as that off
Point Loma and it was at first supposed that this decrease in transparency might
reflect a major change in the biological situation. An increase in opacity had
eccurred during the period from March to Auguet 1946 when the lagoon wae cocupied
by Joint Task Force ONZ.
It was assumed that this was due to the increased or-
ganic activity in the water resulting from the large amounts of organic hutrient
materials put into the water by the Task Force. Since the amount of phosphorus
and nitrogen contributed by the Task Force was only a amall fraction of that nor-
mally present in the water, it is difficult to believe that thia effect alone
could persist for a year in view of the continual partial flushing of the water
of the lagoon, Immediately after test Baker there was a large increase in the
bacterial population, probably due to nutrients from organiams killed by the explosion, It appears poesible that this increaae in bacterial numbers presaged
e change in the biological balance which resulted in a more or less permanent
increase in organic activity and corresponding decrease in transparency of water,
Studies of plankton population during the Resurvey, however, showed no obvious
differences from 1946, and bacteriological observations later in the summer
showed that bacterial levels had resumed their pre-explosion status, The observed decrease in transparency may be a normal, seasonal effect occurring in the
summertime when long swells from the South Pacific enter the lagoon through Enyu
Channel and stir up the bottom sediment, These materials are below the depth
that can be affected by the short, high wind-waves of winter and spring. It is
quite possible that the Pine materials stirred up by the test Baker explosion
and redeposited on the bottom surface sre more easily kept in suspension by wave
action than the bottom sediment existing prior to test Baker, Essential data
that would be critical in reaolving this problem would be measurements of the
transparency in the eastern part of the lagoon during the winter months.
On the basis of the chemists' work some detail can now be added to the
phenomena of the Baker explosion,
Within a tenth of a second after the explo-
sion, some 275-day cerium 144, which is one of the more abundant and troublesome
long-lived isotopes, had been formed as the end-product of a fast radioactive
chain beginning with xenon 144,
Under the great heat and pressure still prevail-
ing, this was mineralized, in a way not possible in a reasonable amount of time
in the laboratory, to an extremely insoluble form, Within a few minutes a large
fraction of all the fission products which ultimately remained in the area were
in the water of the lagoon, An exception was 53-day strontium 89, another longlived substance, some of which was still in the form of 3-minute xenon andwas
carried to the outer edge of the area of precipitation,
The result was that
only about half of the amount of strontium 89 finally produced was deposited in
the target area, After the explosion, the water in the target area was turbid
for more than an hour with bottom debris, some very finely powdered, Photographs
taken shortly after the cloud cleared away show an unsymmetrical patch of milky
water about the size of the target array. All the fissionable material from the
explosion and the following long-lived fission products: yttrium, zirconium,
columbium, antimony, praseodymium, element 61 and europium, as well as many
short-lived fission products, were quickly and permanently adsorbed on the sue-
pended material and carried to the bottom, where all but an insignificant frac-
tion still are, Thirty-three-year cesium was not adsorbed because of the large
quantity of the chemically similar element sodium already present. Twenty-fiveyear and shorter-lived radio-strontium were not adsorbed because the relatively
large amount of chemically identical neutral strontium normally present in sea
water had saturated the surface of the adsorbent.
Only a small fraction of the
various radioactive ruthenium isotopes was carried down because of the tendency
- 102 (2) -