Chapter 11 



Tracer Studies of the Sea and Atmosphere 



119 



made to prevent irreversible procedures which 

 might ehminate the opportunity to study such 

 mixing at the natural level where evaluation of 

 the long term variables is possible. On the other 

 hand, it is also evident that the introduction of 

 artificially produced radioisotopes into the geo- 

 sphere has been productive of a great deal of 

 new knowledge that might otherwise not have 

 been obtained. 



The importance of continuous monitoring of 

 the levels of such substances as tritium cannot 

 be overemphasized. As an example of this, it 

 may be pointed out that one reason that carbon 

 14 is such a powerful tool for the evaluation 

 of ocean-atmosphere interaction that we have 

 relatively precise records on just how much dead 

 carbon has been produced by the combustion of 

 fossil fuels ; were this information not available 

 the use of radiocarbon in such studies would be 

 exceedingly difficult, if not impossible. 



From the carbon 14 inventory discussed in 

 Part II, and assuming an average depth of 

 about 150 meters for the oceanic thermocline, 

 it appears that about 4 per cent of the carbon 

 14 in the sea lies above the thermocline; this 

 corresponds to an activity of about 10 mega- 

 curies. It is thus evident that introduction of 

 artificially produced radiocarbon in 10,000 curie 

 amounts above the thermocline would begin to 

 produce a critical level which would interfere 

 with the natural radiocarbon studies of such 

 fundamental importance. Introduction of 100- 

 1000 curie amounts above the thermocline 

 would produce activity sites which could be 

 traced for years, but such experiments could 

 not be done more than once every decade or 

 so if the natural level is to be preserved. It 

 would thus seem highly desirable that some 

 international body be constituted to record and 

 monitor the material put into the sea and the 

 atmosphere as wastes and for tracer experi- 

 ments. It is a truism to point out that a con- 

 taminated laboratory is rather easily replaced, 

 but that the laboratory of the earth scientists 

 is not easily renovated. 



-CONCLUSIONS 



Anderson, E. C. 1953. The production and 



distribution of natural radiocarbon. Ann. 



Rev. Nuclear Science 2:63-78. 

 Arnold, J. R., and H. A. Al-Salih. 1955. 



Beryllium-7 produced by cosmic rays. 



Science 121:451-453. 



Arnold, J. R., and E. C. Anderson. 1957. 

 The distribution of carbon- 14 in nature. 

 Tellus 9:28-32. 



Begemann, F. 1956. Distribution of artifi- 

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Benioff, p. a. 1956. Cosmic-ray production 

 rate and mean removal time of Beryllium-7 

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Craig, H. 1953. The geochemistry of the stable 

 carbon isotopes. Geochim. et Cosmochim. 

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 1954. Carbon 13 in plants and the relation- 

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Craig, H., and G. Boato. 1955. Isotopes. 

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Craig, H., G. Boato, and D. E. White. 1956. 

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Currie, L. a., \V. F. Libby, and R. L. Wolf- 

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De Vries, H. 1956. Purification of CO, for 

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Dingle, A. N. 1954. The carbon dioxide 

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Dole, M., G. A. Lane, D. P. Rudd, and D. A. 

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