54 



The ones of most concern are those with half lives measured in years 

 and havino^ properties which may tend to concentrate them in marine 

 biota, or whicli otherwise may move thronfrh tlie food cliain to become 

 a threat to man. These, emanatino- from nuclear explosives are shown 

 in table 1. 



TABLE l.-RADIOACTIVE POLLUTANTS IN THE OCEANS FROM NUCLEAR EXPLOSIONS 



Half Life 

 Pollutant Symbol (years) 



lron-55 Fe" 2.9 



Tritium H3 12.0 



Strontium-90 Sr«« 28.0 



Cesium-137.. . Cs"' 30 



Carbon-14 . C" 5,500.0 



Plutonium-239 Pu23» 24,400.0 



The main pathway which broufjht these pollutants to the sea is fall- 

 out. The debris created in the nuclear detonation rises in the air and 

 then disperses, carried great distances by the winds. Since most of the 

 nuclear products were formed in larger explosions, they were car- 

 ried into the stratosphere. The fine particles resided in the strato- 

 sphere for an average period of about 1.5 years, during which they 

 were distributed all around the world, and gradually settled to the 

 Earth's surface, carried down mainly by precipitation. 



Since about 70 percent of the world surface is ocean, it is clear that 

 70 percent of all of the fallout was initially deposited in the seas. 

 Additional amounts of the nuclear bomb products are subsequently 

 carried to the oceans by the rivers and streams, but this is a small 

 fraction of the total. 



Table 2 summarizes the information available on concentrations of 

 the fallout pollutants in seawater and sediment; table 3 lists the data 

 for several biological groups. 



TABLE 2.— CONCENTRATIONS OF SOME FALLOUT POLLUTANTS IN SEAWATER AND SEDIMENTi 



Water Sediment 



FeM - 0.1 -1.0 



H3.... 1.0 -100.0 



Sr'c 1 -1.0 1.0-100 



Csis? 1 -1.0 1.0-100 



C" .01 - .1 



Pu239 00001- .001 .1-1 



I The units are picocureis (a millionth of a mlllonth of a curie) per liter of seawater, and picocuries per kilogram of 

 sediment. Picocurie is abbreviated pCi. 



TABLE 3.— CONCENTRATIONS OF SOME FALLOUT POLLUTANTS IN MARINE LIFE' 



> The units are pCi per kilogram of wet biological material. 



The total content of radioactive pollution contributed by nuclear 

 weapons tests in the world ocean at this time is about 10^ — 1.000 mil- 

 lion — curies. 



