= 17- 
cesium and strontium, when introduced into the sea from fall- 
out, would be present most likely in the insoluble or par- 
ticulate state. Indirect evidence (8, 20) and direct 
observations (9) support this view. The indirect evidence is 
based on geochemical studies in which the potential supplies 
of the elements to the seas from weathering of igneous rocks 
are compared with the amounts of the elements present in 
solution in the sea. These values cannot be applied directly 
to fallout analyses but they do provide the basis for an 
estimate of the fraction of a given fallout element that would 
remain ini solution jin ‘ther sear 
The levels in the sea (ppm) of the naturally occurring 
forms of those elements reported in the present work are shown 
in Table 3. Also listed are the forms of the naturally occur- 
ring elements in sea water, the percentage of the fallout ele- 
ments in solution according to direct and indirect evidence, 
the principal chemical state of the fallout in sea water, and 
the average percentages of the fallout elements observed in 
plankton samples collected about three months after fallout. 
Of the radioactive fallout elements shown, only two, cesium 
and strontium, would occur normally in soluble form in the sea. 
The radioisotopes of these elements were found in the least 
amount in plankton. In contrast, the radioactive fission: 
products with the lowest solubilities, Zr95 and Cel44, were 
present in plankton in the greatest amount (20.2, 8.6 per cent) 
