New chemical insights into the structure and morphology of sea slicks and their geophysical interpretations

The different morphology of palmitic acid methyl ester (PME) slicks spread from

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-hexane or ethanol was studied by ‘Brewster Angle Microscopy’ [BAM]. In the latter case, already at large areas per molecule a foam-like structure is being formed on the water surface, i.e., a two-dimensional network which appears to be comparable with the morphological structure of biogenic sea slicks. In line with this assumption, both the magnitudes of the radar backscatter damping ratios and the characteristics of the damping ratio/wave number curves were comparable for the PME slick spread from ethanol and for the biogenic slicks, while in the presence of the PME slick spread from

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hexane lower damping ratios were determined. In the first instance, we were able to simulate the water wave damping characteristics of the biogenic sea slicks very well. Furthermore, the relaxation of alkanoic acid esters, which are often being found in biogenic sea slicks, was investigated by ‘Infrared Reflection-Absorption Spectroscopy’ [IRRAS]. It turned out that the ester group is continuously hydrated and dehydrated during compression and dilation on an undulating water wave field. It can be safely assumed that the strong water wave damping induced by these chemical compounds is centrally related to this phenomenon.