engleski

Characterization of sea-surface microlayers by monolayer techniques and Brewster angle microscopy

The sea-surface microlayer has been defined as the top 1 to 1000&#61549 ; ; m of the sea surface. Sea-surface microlayers are sites of the adverse biological effects and a medium for the transfer of energy and material between the sea and the atmosphere, representing thus the interfacial region where many important bio-physical-chemical processes and flux of gases are taking place. Natural samples of sea-surface microlayer and samples which have been previously extracted by organic solvent and then reconstructed on the water surface were studied by monolayer techniques and Brewster angle microscopy (BAM). Surface pressure -area ( &#61552 ; ; -A) and surface potential - area (&#61508 ; ; V-A) isotherms have been measured. Simultaneously BAM video images have been recorded. From &#61552 ; ; -A isotherms, thermodynamic parameters describing the states of monolayers, namely compressional modulus Cs-1 and compressibility have been calculated. Monolayer techniques and BAM are proved to be very efficient analytical tools for a physico-chemical characterization of natural films improving thus our understanding of the mechanisms and physicochemical processes at natural phase boundaries. It was found that both natural sample of sea-surface microlayer and ex-situ reconstructed film exhibit the characteristics of a liquid expanded phase without undergoing a phase transition. The BAM images taken from these films depend on surface pressure. At lower surface pressures liquid condensed domains are surrounded by liquid expanded phase and by compressing the domains become smaller and densely packed. References: 1. The sea-surface microlayer and its role in global change, 1995. Gesamp Report and Studies Series b No. 59., WMO, Geneva, 76 p. 2. Z. Kozarac, D. Möbius and D.B.Spohn, Croat. Chem. Acta, in press. 3. B. Gašparović, Z. Kozarac, A. Saliot, B. Ćosović and D. Möbius, J. Colloid Interface Sci., submitted

natural samples; monolayer techniques; Brewster angle microscopy

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