86 BIOLOGICAL EFFECTS OF ATOMIC RADIATION 



the major radioisotope in Columbia River fish. The concentrations of Zn"^ and Cr"^ in the 

 fish are considerably lower(9). 



Monitoring data indicate that the exposure to persons living in the vicinity of the 

 plant and who eat fish caught from the river is below permissible limits. Concentrations 

 of radioisotopes in the waters off the mouth of the Columbia River will be substantially less 

 than in the river near the plant, not only because of additional radioactive decay but also be- 

 cause of retention of the isotopes in river silt and biota, and additional dilution. 



The experiences at Hanford and Windscale illustrate that it may be possible to release 

 radioactive materials to the marine environment with safety in significantly greater amounts 

 than one could predict from preliminary information. Each environment presents a different 

 set of conditions, however, and increase of releases at specific sites should be undertaken with 

 caution and extensive monitoring. Because of the need for relatively precise data on the 

 radiation exposures associated with waste discharge and for further knowledge of safe con- 

 centrations of various isotopes in the water, it is recommended that comprehensive monitoring 

 programs be carried out at all future atomic energy installations that discharge substantial 

 amounts of radioactive waste into marine or fresh water environments. 



6. Recent Developments in our Knowledge of the Deep Sea and in Field Measurement 

 Techniques. 



Significant advances, pertinent to problems of the distribution of radioactivity in the 

 oceans, have been made in two general fields: the measurement of water mass movements 

 and the activity levels of man-produced isotopes in the oceans. Several papers, (10, 11, and 

 12) for example, have appeared on the uptake of elements, principally the heavy metals, by 

 marine organisms, and the results have elaborated and extended previously obtained knowl- 

 edge. In addition, the development of deep-sea cameras(13) has reached the point where it 

 is quite feasible to use these instruments to study the integrity of waste containers on the sea 

 floor. 



Although the knowledge of the circulation of the deep ocean has increased in the past few 

 years, the data are still too scarce and scattered to permit construction of a coherent picture. 

 Carbon- 14 measurements in the Pacific by Rafter, Fergusson and others in New Zealand ( 14) 

 and by Suess in the United States( 15) have confirmed earlier speculation that the deep waters 

 of the Pacific are much older than those of the North Atlantic. Rafter and Fergusson report 

 the average C* age of South Pacific water below 300 m to be greater than 1000 years. Suess' 

 measurements in the eastern Pacific show a regularly increasing age of the deep water from 

 1500 years at 47° S to about 1900 years at 15° N. Wooster and Volkman(16) have shown 

 that the bottom water of the eastern North Pacific is the oldest in the open Pacific. Broecker's 

 C" measurements of Atlantic circulation ( 17) indicate the deep waters have ages of the order 

 or 10^ years or less. 



Within the last few years numerous measurements of the flow in the intermediate and 

 deep layers have been made. Most of the deep observations have been made with the 

 Swallow neutrally-buoyant float. Using this instrument in the Pacific, Knauss(18) has de- 

 scribed the Equatorial Undercurrent, which, at a depth of about 100 m, has an eastward 

 transport along the equator of about 30x10' mVsec and speeds of 100-150 cm-sec. 

 Knauss( 19) has also found a strong eastward flow under the Equatorial Countercurrent, with 

 a transport of about 30x 10" mVsec and speeds of 15-20 cm/sec in the water below the 

 thermocline and extending to 800 m or deeper. In the Atlantic, currents of 2-5 cm/sec have 



