General Considerations 



national scientific cooperation will often be 

 essential for optimum results. 



IV. Chemical Processes and Radioactive 



Materials 



Elements in sea water 



Sea water is a solution of a large number of 

 dissolved chemicals containing small amounts of 

 suspended matter of organic and inorganic ori- 

 gin. The ratios of the more abundant elements 

 are very nearly constant, despite variations in 

 absolute concentrations in different parts of the 

 sea. Lower than average absolute amounts are 

 encountered in coastal areas and near river 

 mouths, while higher amounts are encountered 

 in areas of high evaporation, such as the Red 

 Sea. Vertical variations are usually small; in 

 general, in the open ocean in mid-latitudes, the 

 quantity of dissolved materials, measured by the 

 salinity, first decreases slightly with depth, then 

 increases slowly in the deep water. 



Table 2 (from Carritt and Harley, Chapter 6) 

 shows the concentrations of some of the ele- 

 ments in solution in sea water at a chlorinity 

 of 19.00^0, which is near average for the sea, 

 and the total amounts in the ocean as a whole. 

 Also shown are the total amounts and total 

 radioactivity of the principal naturally occur- 

 ring radio isotopes. In addition to the listed 

 elements, there are variable amounts of dis- 

 solved gases, including nitrogen, oxygen, and 

 the noble gases. A range of values is given for 

 some elements present in small quantities, such 

 as nitrogen, phosphorus, silicon, iron, and cop- 

 per. These are substances necessary for living 

 organisms, and the inorganic phases may be re- 

 duced to nearly zero in surface waters where 

 they have been almost completely removed by 

 organic uptake. 



Behavior of introduced materials 



A number of things can happen to materials 

 introduced into the sea either in solution or as 

 particles. The particles may go into solution. 

 The dissolved substances may be precipitated as 

 particles of colloidal or larger size either by co- 

 precipitation with other elements, by sorption 

 on organic or inorganic particles already present 

 in the sea, or by interaction with other sea water 

 constituents. Both dissolved materials and par- 

 ticles may be ingested by organisms and enter 

 into the biochemical cycles. 



Particles in the sea are continually removed 

 by settling out on the bottom. The rates of 

 settling depend on the size and density of the 

 particles, as modified by various physical and 

 biological factors. 



Normal removal of elements from sea ivater 



The results of geochemical studies provide 

 very approximate estimates of the fractions of 

 some elements supplied to the ocean that are 

 eventually removed from solution. In Table 3 



TABLE 3 Geochemical Balance of Some Ele- 

 ments IN Sea Water (From Goldschmidt, 

 Quoted in Rankama and Sahama, 

 1950, Table 16.19) 



are listed a number of elements, including some 

 of the elements having long-lived fission-product 

 isotopes, with their concentrations in the supply 

 to the ocean and in the ocean itself. Assuming 

 steady-state equilibrium, the ratio of the con- 

 centration in the ocean to the concentration in 

 the supply, the transfer percentage, indicates 

 what share of the supply stays in solution. Large 

 values of the transfer percentage indicate that 

 a relatively large fraction remains dissolved; 

 small values indicate that relatively much is 

 removed. 



These data give no information on the re- 

 moval processes or on the time rate of removal. 

 The latter can be obtained from estimates of 

 rates of natural sedimentation together with 

 chemical analysis of sediments or from study of 

 rates of sedimentation of radio isotopes follow- 

 ing weapons tests or waste disposal operations 

 (Carritt and Harley, Chapter 6) . 



Goldberg and Arrhenius (in press), from a 

 study of natural sediments, have estimated resi- 

 dence times in the ocean for several elements. 

 They conclude that one half the amount of 



