engleski

Physico-chemical characterization of the sea surface microlayers

Sea surface microlayers (SSM) were collected in different seasons over a longer time period in the coastal areas of the Middle Adriatic. Using electrochemical methods the concentrations of surface active substances (SAS) in original SSM and enrichment factors were determined. Higher surfactant activities (> 0.7 mg dm-3) were found in the warmer May–October period compared to the winter season. It was also noticed that the microlayers from the warmer season had a higher contribution of more hydrophobic surfactants. Surface active material, isolated and concentrated from original SSM by extraction using organic solvents of different polarities (n-hexane and dichloromethane) was compared with model lipids of different polarities. Adsorption characteristics of different model and natural films indicated that nonpolar and less-polar lipids represent an important fraction of n-hexane extracts while more polar phospholipids were predominant in dichloromethane films. The latter ones were found to be dominant SAS of original SSM from the late spring-autumn period in the coastal areas of the Middle Adriatic. Monolayer technique has been applied for investigations of physical states and elastic properties of natural microlayers. The most of the SSM were of gaseous or liquid-expanded type. Alongside, Brewster angle microscopy (BAM) was used for characterization and optical visualization of microlayers at the air-water interface without perturbing their structure and/or morphology. Fractal analysis of 2D BAM images enabled new assign into the morphology and structural changes dynamics of original microlayers and reconstructed films in static and dynamic condition.

sea surface microlayer; surface active substances; air-water interface; rheological properties

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