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

Abstract

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 troughWilhelmy 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 (A lim , M w , E isoth ), film solubility and the miscibility of its components (via R, DS c and y factors), and surface concentration (p eq , G eq ). The adsorption kinetics parameters: effective diffusion coefficient D eff /D and activation energy barrier E a /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.

Biological modification of mechanical properties of the sea surface microlayer, influencing waves, ripples, foam and air-sea fluxes

“…The third pool consists of less than 1% of the total OM in the ocean, but it is very labile and so represents a large C flux (Hansell et al, 2009). We suggest that this fraction, generally close in space and time to areas of high productivity, is also the most rheologically active, both in the SML (Pogorzelski et al, 2005) and in the bulk phase (Jenkinson and Sun, 2010;Jenkinson et al, 2015).…”

“…Concerning vertical molecular diffusion Pogorzelski (2001), Pogorzelski and Kogut (2001) and Pogorzelski et al (2005), reviewing previous work, calculated molecular mass M W from plots of surface pressure, Δτ 2D vs. t for short (t → 0) and long (t → ∞) times, and also calculated diffusion coefficient D as if it had been composed of monomers rather than polymeric clusters. Values of M w scattered widely from 2 to 166 kDa, with a typical value of 50 kDa.…”

Evolution of ocean slicks under a rising wind

“…For a wind‐sheared water surface, reasonable choices for the turbulence scales are the water friction velocity u * and the roughness length z o = a u * 2 /g, where a is a constant of the order of 1400 [e.g., Craig and Banner , 1994]. For a wind speed of 5 m/s, u * ∼ 1 cm/s and z o ∼ 1 cm; so using a value of E ∼ O (10 mN/m) as typical of a filmed area of ocean [e.g., Pogorzelski et al , 2006] yields β * ∼ O (10). This high value of β * suggests (based on Figure 5a) a thermal slick contrast near its maximum value.…”

“…How strong an underlying motion is needed to break up a film? It is known that the occurrence of slicks diminishes rapidly as the wind increases from near calm to a speed of ∼5 m/s [ Romano , 1996; Pogorzelski et al , 2006]. This behavior is usually attributed to a break‐up and dispersal by Langmuir circulation (Figure 1), but detailed observations of the dispersion of natural slicks by Langmuir circulation appear to be lacking.…”

n-Alkanes, PAHs and surfactants in the sea surface microlayer and sea water samples of the Gerlache Inlet sea (Antarctica)

“…Hunter and Liss [3] suggested that surface film is a gelatinous matrix, with molecules supported at the interface by inter and intramolecular interactions. Some authors [10] emphasize the multicomponent character of natural surfactant films and the consequent complications in attempting to predict interfacial elastic properties due to the diverse chemical makeup of such films.…”