222 and radium-228 in both the surface layers and the bottom water. 

 These results are useful for studying the air-sea and bottom-sea inter- 

 change of material. Several trace elements, notably copper, scandium, 

 antimony, and nickel, have been studied sufficiently to show that vertical 

 models should be useful in understanding their chemistry in the sea. 



A second type of model currently being used for chemical constituents 

 is a two-dimensional, horizontal diffusion and advection model. These 

 models are based on "Strommelian" geostrophy with vertical advection 

 balancing the horizontal inflow of water from western boundary currents 

 which feed the interior regions of the world oceans. Conceptually, they 

 are a natural extension of the simple "box models" that have been used 

 successfully to understand the general nature of the vertical distribution 

 of radioisotopes. 



Physical oceanographers are extending these simple models account 

 for such effects as topography and nonlinear terms in the equations 

 of motion. A similar approach can be made with nonconservative species. 

 To approach a realistic model of the chemical and particulate interac- 

 tion processes in the sea, efforts should be made to develop three- 

 dimensional models for describing oceanic processes. More emphasis 

 on this aspect of chemical oceanography is urgently required to guide 

 the future development of the subject and to insure a continual interac- 

 tion with the developments made in physical oceanography. 



Measurements of constituents of global fallout in the upper layers 

 of the Pacific during the past decade have suggested that distributions 

 of certain species may be dominated by lateral advection and lateral 

 mixing in certain large areas, notably in the North Pacific Ocean. Large 

 fractions of passive materials such as radiocesium have remained in 

 the upper 300 for more than 10 years after entering as fallout (Folsom 

 et al., 1968; Folsom et al., 1970; Hodge et al., 1972). For a period as 

 long as this, one must expect advections of thousands of miles and take 

 into account geographic and seasonal variations of inputs before attempt- 

 ing interpretations of vertical profiles. The sampling required for a model 

 of this scale needs specialized procedures and specialized analytical 

 methods. Nevertheless, a knowledge of the behavior of a passive material 

 such as cesium or tritium seems essential for any study of the progress 

 and chemical behavior of many other chemical species in the upper 

 ocean layers. The advective parameter simply cannot be ignored in 

 the model; however, chemical procedures can be evoked to discover their 

 magnitudes. 



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