engleski

Adsorption properties of surface active substances in the natural sea surface microlayer

The sea surface microlayer (SSM) represents natural interface between the atmosphere and ocean defined as the uppermost 30 to 300 μm of the ocean surface. The SSM plays a key role in the global biogeochemical cycling because all gaseous, liquid and particulate materials must pass through this interface when exchanging between the ocean and the atmosphere. The SSM thus represents a very important driver enhancing air–water exchange processes. There is a widely accepted concept that the SSM is complex gelatinous matrix of different organics. A large fraction of the SSM organic matter includes surface active substances (SAS) which adsorbed at the air–water interface form surface films and change the physicochemical and optical properties of the natural interface region. The goal of this work is to use electrochemical methods to provide better insight into the physicochemical characteristics of dominant surface active material in the natural sea surface microlayers obtained from two specific locations in the coastal area of Middle Adriatic Sea. Natural SSM were studied as original samples and as ex-situ reconstructed films after previous extraction by organic solvents of different polarities. Using alternating current (ac) voltammetry the concentration of SAS in original SSM was determined, and the enrichment factor in the SSM was related to the underlayer water samples collected at 0.5 m depth. The ex-situ films were studied using modified ac voltammetry by transferring an organic extract of natural microlayers spread onto electrolyte from the air-water interface to the mercury electrode surface and the obtained results will be compared with adsorption characteristics for model lipids of different polarities. Additionally, it will be presented that useful information on the dominant microlayer forming material can be obtained by investigating the influence of SAS on the electrode process of other ions which are used as an electrochemical probe.

surface active substances; lipids; electrochemical methods

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