Specific problems in the measurement and interpretation of complexation phenomena in seawater (technical report)

Characterization of metal complexation phenomena in seawater is a formidable challenge. Adequate characterization of inorganic complexation schemes is currently limited by a paucity of well-defined hydrolysis constant data for chemical species which are important in the weakly alkaline conditions of normal seawater. Other important problems include the neglect of equilibria involving ligands and metals which form highly insoluble solids, and a poor understanding of the influence of pressure on stability constant behavior. Characterization of metal complexation by organic ligands in seawater is especially problematic. There is presently a large gulf between laboratory investigations of metal complexation by structurally characterized organic ligands, and investigations of complexation by natural organics whose molecular architecture is essentially unknown. In view of the wide variety of techniques used to investigate the complexation behavior of natural marine organics, and the diverse and occasionally conflicting attributes reported for metal complexation by natural organics in seawater, it would be most valuable if some level of effort were devoted to analysis of shared samples. In view of the multi-faceted strengths of the diverse procedures available for characterization of natural organo-metal interactions, conjugate analysis using a variety of techniques on identical samples seems essential for bringing a reasonable level of constraint to interpretation of complexation observations.