WASTES IN THE SEA — ^WALLEN 389 



their shells. Carbonates may be formed by precipitation or secre- 

 tion in shell formation by marine forms. E. D. Goldberg stated in 

 Chemical Scavengers of the Sea, published in 1954, that zirconium 

 and titanium, present as anions in sea water, are scavenged by iron 

 oxides and deposited in sediments. Alteration of suspended detritus 

 into apatite may occur in the ocean with attendant uptake of radio- 

 active elements. Bonelike materials of marine invertebrates may be 

 modified into minerals and metals, or alkaline soils. A host of ele- 

 ments are concentrated by the minerals in the sea tlirough accumulation 

 into the disordered structural layers, or by ion exchange mechanisms. 



Although no economic method of harvest has been discovered, about 

 10 percent of the abyssal area of the ocean floor is covered by aggre- 

 gates of iron, manganese, and other minerals which together are 

 called manganese nodules. Manganese, nickel, cobalt, copper, iron, 

 and perhaps other minerals are present m these nodules in such quan- 

 tities that they may be economically mined in the future. If radio- 

 active wastes contain substantial quantities of long-lived isotopes, they 

 should not be discharged into areas of the ocean covered by these min- 

 eral resources. 



BIOLOGICAL TRANSFER 



In addition to the translocation of waste materials through uptake 

 and migrations, the remains of dead organisms, undigested wastes, 

 and skeletal parts of marine organisms may sink to the bottom and 

 form a substantial portion of the bottom deposits in the ocean. Gen- 

 erally, the deeper sediments have relatively few biological organisms, 

 and no species are believed present that would readily concentrate 

 radioactivity to present a potential hazard to man's food resources. 



In 1961, G. Arrhenius proposed that biological extraction of barium, 

 strontium, and lead is evident in surface sea water, resulting in verti- 

 cal transport of these and other heavy metals to the sea floor where 

 they may be accumulated. Certain species of Protozoa (Acantharia, 

 Radiolaria), pteropods, and heteropods are believed to play an impor- 

 tant role in this vertical transport. The skeletons of certain Eadio- 

 laria appear to sink rapidly through the water and then to dissolve 

 entirely before burial in the sediment. In this manner, strontium 90 

 could be transported at a more rapid rate than would be assumed from 

 its behavior in the open ocean. 



Since colloidal clays tend to form stable suspensions on the sea floor 

 of the open ocean, the adsorption of radioactive wastes by sediments 

 normally would be a safety factor in their disposal. However, in 

 a situation where bottom areas adjacent to a disposal site are the 

 source of seafood products such as oysters, clams, mussels, and bottom- 

 dwelling fishes, the accumulation of wastes on the bottom may provide 

 for increased contamination of the fisheries. 



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