Stanisław J. Pogorzelski

Structural and thermodynamic signatures of marine microlayer surfactant films

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 kA studies without any initial physico-chemical sample processing. The limiting specific area Alim (2.68–31.57 nm 2 /molecule) and mean molecular mass Mw (0.65–9.7 kDa) of microlayer surfactants were determined from the 2D virial equation of state applied to the isotherms. Enthalpy DH and entropy DSt 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 H 1=1.1–2.8 and H 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. D 2003 Elsevier Science B.V. All rights reserved.

Isotherms of natural sea surface films: A novel device for sampling and properties studies

A double‐walled submersible sea surface film sampler which ‘‘cuts out’’ an undisturbed film‐covered area has been built for force‐area isotherm studies of untreated water samples. Preliminary results on static and dynamic surface properties of naturally formed films present in coastal zones of the Baltic Sea are presented and discussed in reference to water samples collected in a bottle (depth of 20 cm) at the same site and time, which in turn significantly differ from each other. The new sampler also allows a few statements of oceanographic relevance on the film homogeneity (i.e., film filling factor) and the energy transfer through surface films from isotherm hysteresis measurements.

Structural and thermodynamic characteristics of natural marine films derived from force–area studies

Abstract Natural marine film experiments in shallow offshore waters of the Baltic and Mediterranean Seas were carried out over the period 1990–1996 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 (8 cm thick) to perform π – A studies without any initial physico-chemical sample processing. The limiting specific area A lim (268–3157 A 2 per molecule) and mean molecular weight (0.65–9.7 kDa) of microlayer surfactants were determined from the 2D virial equation of state applied to the isotherms. The π – A isotherms recorded in the temperature range 5–35°C exhibited several plateaus and ‘kinks’ corresponding to 2D phase transitions that allowed for the first time completing the phase diagram ( π – T ) of natural films. Enthalpy Δ H and entropy Δ S t of the first-order phase transitions (G → LE → LC) were evaluated using the Clausius–Clapeyron equation applied to the isotherms. Additional information on the film structure were derived from the entropy change Δ S c attributed to the π – A hysteresis, and the polymer film scaling theory adopted to marine films. The results obtained suggest that natural films are a complex mixture of biomolecules covering a wide range of solubilities, surface activity and molecular weight with an apparent structural organisation.

Surface Rheology Parameters of Source-Specific Surfactant Films as Indicators of Organic Matter Dynamics

The paper contains the results of natural film experiments carried out on inland and coastal waters in the Dead Vistula catchment area and mouth 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. They appear to reflect in a quantitative and sensitive way the film composition (Alim, Mw, Eisoth), film solubility and the miscibility of its components (via R, ΔSc and y factors), and surface concentration (πeq, Γeq). The adsorption kinetics parameters: effective diffusion coefficient Deff/D and activation energy barrier Ea/RT are derived from dynamic surface pressure. 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 biosurfactants is postulated to reflect organic matter dynamics in natural waters and were measured for the Dead Vistula river, its tributaries and the adjacent coastal area.

Application of 2D polymer film scaling theory to natural sea surface films

The polymer film scaling theory was applied, by measuring the high-frequency limit of the surface modulus E0 as a function of the surface pressure P [E0 = yP, where y = 2ν(2ν − 1) and ν is the critical exponent of the excluded volume], to natural marine surface films. An increase in y from < 3.5 through ∼ 8 to over 10 indicating “good”, Θ, and “poor” solvent behaviour, respectively of the interfacial system is also correlated with the structure transition in the multicomponent film beginning from a homogeneous mixed monolayer, through a heterogeneous film with surface-active substances segregated into patches or domains to at least a vertically layered structure at the interface, and it is believed to hold for natural sea surface films. The scaling exponent y is a complex function of environmental factors affecting the film structure (bulk concentration of a surfactant, pH, ionic strength and composition of the subphase, temperature, locations of sampling site and film collection procedures).

Elastic Properties of Natural Sea Surface Films Incorporated with Solid Dust Particles: Model Baltic Sea Studies

◦)d eposited at surfaces of surfactant-containing original seawater and were studied with a Langmuir trough system. The composite surface dilational modulus predicted from the theoretical approach, in which natural dust load signatures (particle number flux, daily deposition rate, and diameter spectra) originated from in situ field studies performed along Baltic Sea near-shore line stations, agreed well with the direct experimentally derived data. The presence of seawater surfactants affected wettability of the solid material which was evaluated with different CA techniques applicable to powdered samples. Surface energetics of the particlesubphase interactions was expressed in terms of the particle removal energy, contact cross-sectional areas, collapse energies, and so forth. The hydrophobic particles incorporation at a sea surface film structure increased the elasticity modulus by a factor K (1.29–1.58). The particle-covered seawater revealed a viscoelastic behavior with the characteristic relaxation times ranging from 2.6 to 68.5sec.

Acoustic Returns from a Wind-Excited Surface Covered with Monomolecular Oil Films

Organic sea surface films of biogenic and man-made origin are particularly predominant in coastal zones.1 They modify the physics of the sea surface and influence remotely sensed optical and microwave imagery. 2,3 One of the most obvious and sensible film-induced effects is the Marangoni damping of short-gravity and capillary ripples water waves.4 A complete treatment of this problem also involves the physicochemical properties of the film itself.5

Characteristics of acoustic scattering from a wind-created water surface covered with monomolecular organic films

Abstract A spectrum of amplitude fluctuations of the acoustic signal scattered from a wind-driven water surface coated with a monomolecular film of well-defined viscoelastic surface properties was studied under laboratory conditions. The presence of an oil film causes a shift of the peak frequency to higher frequencies and increases the fall-off in the high-frequency band of the spectrum compared with clean surface scattering. The effect turned out to be unequivocally related to rheological parameters of the surface film. Similar features of the scattered signal and wind-generated wave spectra observed for film-covered surfaces can be treated by the Marangoni theory of damping of water surface waves by viscoelastic films.

INFLUENCE OF SURFACTANT CONCENTRATION AND TEMPERATURE GRADIENTS ON SPREADING OF CRUDE-OIL AT SEA

Spreading kinetics measurements were carried out on crude oils at natural surfactant-containing sea water of well-controlled thermo elastic surface properties in laboratory conditions. It was found that oil lens expansion rates, predicted from the classical surface tension-driven spreading theory, were higher by a factor of 6-9 than those experimentally derived for natural seawater. Previously, in order to explain such a discrepancy, the initial spreading coefficient S0 - entering the lens radius vs time dependence was exchanged with the temporal one St dependent on the water phase surface viscoelasticity of (Boniewicz and Pogorzelski, 2008). Now, natural surfactant concentration and temperature gradients perpendicular to the surface were shown to drive a particular cell-like flow at the surface microlayer, as a result of the classic and thermal Marangoni phenomenon. The balance of interfacial forces was taken as: -µ∂Us/∂z=∂γ/∂T•∂T/∂x+∂γ/∂c•∂c/∂x where: µ is the dynamic viscosity, Us - the velocity, z and x axes oriented perpendicularly and horizontally to the main flow direction, T, γ, c are the temperature, surface tension and concentration of surfactants. Computations performed on original seawater (Baltic Sea) systems, shown that the natural surfactant concentration term ∂γ/∂c is several times lower than the thermal ∂γ/∂T one (Boniewicz and Pogorzelski, 2016). Such a surface tension gradients induce the Benard-Marangoni instability, for high enough the so-called Marangoni numbers that could significantly slow down the spreading process. On the basis of thermo-physical model liquids properties, the critical temperature difference ∆Tc required to initiate the process under an evaporative cooling condition was evaluated.

Monitoring of Marine Biofilm Formation Dynamics at Submerged Solid Surfaces With Multitechnique Sensors

Biofouling on artificial and biotic solid substrata was studied in several locations in the Baltic Sea brackish water (Gulf of Gdansk) during a three-year period with contact angle wettability, confocal microscopy and photoacoustic spectroscopy techniques. As a reference, the trophic state of water body was determined from chemical analyses according to the following parameters: pH, dissolved O2, phosphate, nitrite, nitrate, ammonium etc. concentrations and further correlated to the determined biofilm characterizing parameters by means of Spearman’s rank correlation procedure. Biofilm adhesive surface properties (surface free energy, work of adhesion etc.) were obtained with the contact angle hysteresis (CAH) approach using an automatic captive bubble solid surface wettability sensor assigned for in-situ, on-line and quasi-continuous measurements of permanently submerged samples (Pogorzelski et al., 2013, Pogorzelski and Szczepanska, 2014). Structural and morphological biofilm features (biovolume, substratum coverage, area to volume ratio, spatial spreading, mean thickness and roughness) were determined from confocal reflection microscopy (COCRM) data. Photosynthetic properties (photosynthetic energy storage (ES), photoacoustic amplitude and phase spectra) of biofilm communities exhibited a seasonal variability as indicated by a novel closed-cell type photoacoustic spectroscopy (PAS) system. That allowed mathematical modeling of a marine biofilm under steady state, in particular the specific growth rates μi, and the conditioning or induction times λi to be derived from simultaneous multitechnique signals. A set of the established biofilm structural and physical parameters could be modern water body trophic state indexes.