Electrochemical Characterization of Fluid Vesicles in Natural Waters

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Abstract
The electrochemical method of polarographic maximum based on the interfacial instability of a positively charged interface dropping mercury electrode/sea-water, allows a direct characterization of single events of coalescence and transformation of aggregates of fluid surfactants into adsorbed monolayers at the interface (relaxation times 10 – 500 ms, aggregation numbers > 109). Highly surface active aggregates, resembling those of unsaturated lipids, were detected in the sea surface microlayer samples and in the mixing layers in the estuaries, although the unsaturated lipids represent only a minor fraction (<10%) of the aquatic organic matter. Products of flocculation of dissolved organic matter during estuarine mixing resemble closely fluid vesicles released by marine microflagellate, such as Dunaliella tertiolecta, that was studied in a greater detail. The analysis of complex electrochemical responses in natural heterodispersion is developed using artificial dispersions of oleate and methyl oleate in sea-water, as models.