techniques available not only to study the distribution of total concentra- 

 tions of trace elements in seawater but also to distinguish between 

 weakly associated and complexed forms or other important physico- 

 chemical states (i.e., speciation). 



Although the appearance of a powerful new technique may permit 

 the investigation of a minor element not previously considered, a major 

 effort should continue to be undertaken in the refinement of techniques 

 presently being applied to the study of any of the minor elements. These 

 efforts help locate active sites of chemical processes in the ocean en- 

 vironment. 



At the present time, it is difficult to decide when variations in mea- 

 sured metal concentrations among various investigators are real differ- 

 ences or artifacts caused by different, arbitrarily chosen, sampling and 

 pretreatment methods. A serious effort to continue to develop techniques 

 for the construction and operation of noncontaminating sampling devices 

 is needed. Existing commercial and laboratory-built samplers should be 

 checked for adsorption and exchange reactions involving the minor 

 element to be determined from the sample. 



The problems of sample storage and shipment also remain unsolved. 

 Most investigators have arbitrarily chosen a certain container material 

 and subject the sample to some treatment such as acidification, freezing, 

 freeze-drying or the addition of preservatives such as mercuric chloride. 

 This has been operationally necessary to obtain any data at all, but the 

 consequences of such treatment on any given minor element are not 

 necessarily known. Also, existing methods for determining minor 

 elements all suffer to some extent from the lack of intercalibration 

 and standardization. The results of the Geochemical Ocean Sections 

 (GEOSECS) intercalibration attempts (Brewer and Spencer, 1970) 

 show that a perfectly reasonable and timely project in chemical oceanog- 

 raphy is the caHbration of methods. The question of how to store and ship 

 standards is unsolved. Research should be undertaken on the develop- 

 ment of sets of solids, soluble powders, standard solutions, and seawater 

 samples with sufficient integrity to permit intercalibration for perhaps 

 several years. 



Our ability to make direct measurements of trace-element concentra- 

 tions in the oceanic environment is in many cases inadequate. A con- 

 certed effort should be made to refine and extend the use of presently 

 available methods such as atomic absorption, polarography, and specific- 

 ion electrodes. At the same time, strenuous efforts should be made to 

 apply other spectroscopic techniques such as UV-visible spectroscopy 

 to direct and in situ measurements. 



The valuable information from the in situ equilibrium measurements 

 of Ben-Yaakov and Kaplan (1971), Petersen (1966), and Berger (1967) 



22 



