期刊
JOURNAL OF SEA RESEARCH
卷 49, 期 4, 页码 347-356出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/S1385-1101(03)00038-8
关键词
southern Baltic; Gulf of Gdansk; surfactant films; isotherm scaling; surface thermodynamics; visco-elasticity
Natural surface film experiments in inland waters and shallow offshore regions of the Baltic and Mediterranean Seas were carried out in the time period 1990-1999 under calm sea conditions using a novel device for sampling and force-area studies. The sampler-Langmuir trough-Wilhelmy filter paper plate system 'cuts out' an undisturbed film-covered sea area to perform phi-A studies without any initial physico-chemical sample processing. The limiting specific area A(lim) (2.68-31.57 nm(2)/molecule) and mean molecular mass M-w (0.65-9.7 kDa) of microlayer surfactants were determined from the 2D virial equation of state applied to the isotherms. Enthalpy DeltaH and entropy DeltaS(t) of the 2D first-order phase transitions were evaluated using the Clausius-Clapeyron equation applied to the isotherms. Miscibility of film components and film structure evolution is expressed by the scaling exponent y adopting the 2D polymer film scaling theory. The stress-relaxation measurements revealed a two-step relaxation process at the interface with characteristic times tau(1) = 1.1-2.8 and tau(2) = 5.6-25.6 seconds suggesting the presence of diffusion-controlled and structural organisation relaxation phenomena. The obtained results suggest that natural films are a complex mixture of biomolecules covering a wide range of solubilities, surface activity and molecular masses with an apparent structural organisation exhibiting a spatial and temporal variability. (C) 2003 Elsevier Science B.V. All rights reserved.
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