NATURAL SURFACE-FILM STUDIES IN SHALLOW COASTAL WATERS OF THE BALTIC AND MEDITERRANEAN SEAS

Natural surface film experiments in shallow offshore waters of the Baltic and Mediterranean Seas were carried out in 1990 and 1991 under calm sea conditions, using a novel device for sampling and studies of monolayer properties [POGORZELSKI, 1992a, Review of scientific Instruments, 63(7), 3773-3776]. The sampler ''cuts out'' an undisturbed film-covered region, 8 cm in thickness, to perform force-area measurements of untreated water samples. Intercomparisons of the isotherm features for water samples from 0.5 m depth and those collected by the sampler, at the same location and time, have indicated significant differences. The selected film parameters (elasticity modulus, film homogeneity represented by the filling factor, isotherm reversibility, the mechanical energy transfer through surface films from isotherm hysteresis measurements, and film formation rate) are subjected to large seasonal and spatial variability. Averaged natural film signatures found in the Baltic and Mediterranean and reported by others (PBLINOVSKY and TALIPOVA, 1990, SAS films on the sea surface, SSSR Academy of Sciences) for the Black Sea differ significantly from each other.