=20— 
390 p in diameter (mostly 190-400 p). Identification of 
the chemical form was made by electron and X-ray dif- 
fraction techniques. Calculations of Miyoshi (18) indicate 
that particles of calcite 400 p in diameter would settle 
from the surface to 200 meters in 26 minutes and those 100 p 
in diameter in 7 hours. Thus the mechanism for rapid 
scavenging of Sr°97?9 tn fallout introduced into the sea 
would be provided by calcite settling through the thermocline. 
Co-precipitation would provide another scavenging mecha- 
nism for radiostrontium in the fallout area. When calcium 
carbonate is precipitated in sea water strontium is co-pre- 
cipitated and carried down with the calcium. This technique 
is commonly used in radiochemical separations on sea water. 
The amount of strontium removed from solution in the sea by 
the precipitation of calcium derived from oxidized and hydro- 
lyzed coral is not known but probably is not low. 
Strontium, co-precipitated with calcium carbonate into 
the particulate form, then would become available to filter 
feeding organisms. However, a limited fraction of the parti- 
cles would settle out of reach of the biosphere into deep 
water. A rapid turnover of strontium has been observed in 
all marine invertebrates and fishes studied up to now (1, 3). 
Thus, ingested radioactive strontium in the particulate form 
would be continually recycled to the sea in solution so that 
in time it would come to equilibrium with the naturally oc- 
curring non-radioactive form. 
