-22- 399 p in diameter (mostly 190-400 p). Identification of the chemical form was made by electron and X-ray diffraction techniques. Calculations of Miyoshi (18) indicate that particles of calcite 40) 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 sr39-39 in fallout introduced into the sea would be provided by calcite settling through the thermocline. __ Co-precipitation would provide another scavenging mechanism for radiostrontium in the fallout area. When calcium carbonate is precipitated in sea water strontium is co-precipitated 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, feeding organisms. then would become available to filter 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, DOE ARCHIVES 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 occurring non-radioactive form. 27