Direct measurements of some selected systems (e.g., the ion com- 

 piexing of metal ions) must also be made because they serve as a check 

 for the various estimates. Several methods have been developed to 

 predict activity coefficients, partial molal volumes, and enthalpies of 

 solutes in seawater. Some of these are semiempirical (based on direct 

 measurements in seawater), while others are theoretical (based on 

 measurements in pure water). Further work is needed to determine 

 which method is more useful. Since there are considerable thermo- 

 dynamic and kinetic data available in pure water, estimates based on 

 pure-water data could prove to be the easiest and fastest to make. 



MINOR ELEMENTS 



Chemical processes involving minor constituents in the ocean may 

 be either homogeneous (within the solution phase) or heterogeneous 

 reactions (at a solution-solid phase or solution-gas interface). Knowledge 

 of the homogeneous reactions, such as chemical complexation and redox 

 transformation, is important in assessing and predicting the chemical 

 reactivity of minor elements in seawater. Understanding heterogeneous 

 reactions, such as adsorption, ion exchange, precipitation, and dissolu- 

 tion, is necessary for considering the flux of materials through the 

 ocean. Evaluations of these fluxes were considered in detail in Session 

 C; the concern here is to identify the processes and to indicate those 

 that should be emphasized in future research. 



A characterization of chemical reactions implies the quantification 

 of both their equihbrium and kinetic aspects. However, to apply this 

 information in the marine environment, we must identify the sites at 

 which active chemical processes occur. Analytical studies and in-situ 

 experimentation in the ocean will reveal the locations of active chemical 

 processes. 



Knowledge of inorganic chemical processes involving minor con- 

 stituents is important for a variety of reasons. For one, these reactions 

 determine the nonbiological cychng of trace elements in the marine 

 environment. The impact of man's activities on the ocean is largely 

 determined by the fate of chemical substances added to the sea. Con- 

 versely, the effect of the environment on man's activity within the 

 ocean depends on some of these processes. Minor elements can serve 

 as sensitive indicators of biochemical and geochemical processes in 

 seawater and sediments, and some of these constituents may be related 

 to biological productivity. Some of the reactions involving minor com- 

 ponents are significant in the formation of economically important 

 substances such as ferro-manganese and phosphate deposits. 



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