- 51 form by precipitation,
co-precipitation with accompanying
materials, or by adsorption to organic material or inorganic
silts and clays.
As in other solutions, precipitation will
occur only when the solubility product of the least soluble
compound of the element has been exceeded.
Prediction of
the physical state of fission products in sea water is
difficult because most of them are elements that occur only
rarely in the complex mixture of elements in the sea and
little is known of their ionic activity.
Although water movement is the principal method
of horizontal transport of fallout materials in the ocean
and the physical and chemical forms of fallout are important to vertical transport,
the uptake of radioisotopes
by the biota temporarily removes some of the fallout material
from the forces of gravity and also may be an important
factor in the vertical transport of materials in the ionic
form across water boundaries such as the thermocline and
the stratified layers below the thermocline.
Plankton and
the organisms of the “deep scattering layer" commonly make
diurnal migrations from deep water to | near the surface.
When fallout material first enters the water,
plankton
acquire radioisotopes in both the soluble and insoluble