Search

Abstract: The paper contains the results of natural film experiments carried out on inland waters in the Dead Vistula catchment area during 2000–2002 using the integrated Langmuir trough–Wilhelmy plate system. The static film parameters result from the generalized scaling procedures applied to the surface pressure-area isotherms and surface pressure–temperature isochores. They appear to reflect in a quantitative and sensitive way the film composition (A lim, M w, E isoth), film solubility and the miscibility of its components (via R, ΔS c and y factors), kinetic mobility of surfactant molecules (β s, π k), and its surface concentration (π eq, Γ eq). There is a reason to suggest that certain classes of film-forming components or “end-members” may dominate the static and dynamic surface properties. Variation in the surface rheological parameters of source-specific surfactants is postulated to reflect organic matter dynamics in natural waters and were measured for the Dead Vistula river, its tributaries and the adjacent sea coastal area. The obtained results demonstrate that natural films are o complex mixture of biopolymeric molecules covering a wide range of solubilities, surface activities and molecular masses with a complex interfacial architecture. For the first time, the apparent solvent polarity effect on the structure and surface parameters of ex-situ formed natural sea microlayer films was quantitatively evaluated by means of the author''s scaling procedures applied to unique Brewster angle microscopy and Langmuir trough isotherm data on Mediterranean Sea samples obtained by others. [Copyright &y& Elsevier]

The aim of the study was to quantify the adsorptive and thermo-elastic properties of snowmelt water surface films and their spatial-temporal evolution with snowpack structure characteristics and the entrapped surface-active organic composition. Surface pressure-area (π-A) T isotherms, surface pressure-temperature (π-T) A isochors, and stress-relaxation (π-t) measurements were performed using a Langmuir trough system on snowmelt water samples collected in a large-scale field studies performed at several industrialized and rural Tricity (Gdansk, Poland) areas at various environmental conditions and subsequent stages of the snowpack melting progress. Since the snow-melted water composition and concentrations of surface active organic matter fractions therein are largely undetermined, the force-area isotherm scaling formalisms (2D virial equation and 2D film scaling theory of polymeric films) were adapted to the complex mixture of surfactants. The surface film parameters and their spatial and temporal evolution turned out to be unequivocally related to principal signatures of the film-forming materials: surfactant concentrations (π, A lim ), surface activity (E isoth , |E|), film material solubility (R), surface material miscibility and 2D architecture complexity (y, β s ), molecular thermal mobility (π k ), and a timescale of the relaxation processes within the film (τ i , |E|). Moreover, the parameters appeared to be correlated with snowpack structure characteristics (snow density ρ, specific snow area SSA, snow cover thickness), sample age time, and anthropogenic atmospheric contamination pressure source locations. In particular, E isoth was found to be related to ρ and SSA, while R correlated with the solubility of film-forming organics which turned out to be long-chain fatty acids; similarly, spatial profiles of E isoth revealed the peak values next to the areas being under a severe anthropogenic air pollution pressure. Snowmelt water films stand for a structurally heterogeneous (y > 10) interfacial system where several transition processes of differentiated time-scales (relaxation times from 7 to 63 s) took place leading to the apparent surface viscoelasticity. To sum up, the established surface rheological parameters could serve as novel indicators, based solely on physical attributes, allowing to follow the snowpack evolution, and its melting polymorphism in order to test or improve the existing snow-entrapped organics release models based on chemical analyses. The cross-correlation functional dependences of practical value remain to be established on the larger data set.