12
These investigators also described the effects of hydration and wetting
on the CaQ - Ca(OH}o perticies.
Beczuse of the derse low porosity nature of
these particles, their atmospheric hydration was dependent on the aqueous
environment encountered during "fallout."
Complete hydration, observed over
several weeks time, was accompanied by a 100% increase in particle volume and
the development of a crumbly, fluffy structure.
When CaQ/Ca(0H)> particles
were wet with seawater, they beaan to dissolve slowly.
The freed calcium fons
reacted with sulphate ions in the seawater to form calcium sulphate-dihydrate
(gypsum) while the hydroxy] ions reacted to form insoluble Mg(OH)2.
A hard
shell of Mg(OH)> formed around the particle, which, during the period of observation, apparently stopped any further intrusion of seawater as a region of
Ca(OH)> remained on the inner surfaces of the often hollow spherical particles.
The remaining radioactivity was associated with the Ca(OH)> in the center of
the sphere.
Some of the freed Ca ions in the spheres also formed CaC03 by
the reaction with the bicarbonate ions in seawater.
3.3
Chemical Properties of Plutonium and Americium in Aqueous
Environments
3.3-1
General Considerations
Plutonium (element 94) and americium (element 95) are
revvers of the innter transition series of elements (from actinium (Z = 89]
to lawrencium [Z = 103] known as the actinide elements.
These elements, like
their rare earth homologs, the lanthanides, and the main ("d") group of
transition elements, are defined as those elements having partly filled d or
f quantum shells.
The chemical bonding and complexing properties of trans-
‘tion elements are determined by the electronic environment around their
valence (bonding) electrons.
Many chemical reactions possible for actinide
elements are understood by analogy of the similarities and differences between