Static and dynamic surface tension of marine water: onshore or platform-based measurements by the oscillating bubble tensiometer

The functionality and performances of an oscillating bubble tensiometer designed for the measurement of static and dynamic surface tension of marine water samples are illustrated. The instrumentation completely works in automatic mode. Semi-continuous operation can also be easily implemented. By virtue of its geometrical configuration, the apparatus shows a relative insensitivity to external disturbances, in comparison to other measurement techniques, and consequently it can be employed even under severe environmental conditions, such as those encountered onshore or on platform-based locations. Experimental observations of the dynamic surface tension response to harmonic surface area changes are reported, for samples of sea water and for a dilute aqueous solution of a standard surfactant. The observed results are considered useful for a physical characterisation of marine water in respect to interfacial ocean-atmosphere phenomena and processes. Furthermore, the oscillating-air-bubble tensiometer mimics the real behaviour of the bubbles (ubiquitously present in the near surface of the oceans) and appears to be a suitable instrument for the assessment of the presence of natural and man-made adsorption-film-forming organic materials at the air/water interface.