Transport of surface-active organic materials from seawater to the air-water interface by an ascending current field

Abstract

Surface slicks at sea arc characterized hy the occurence of capillary wave-damping materials at the air-water interface. Physical mechanisms causing such slicks are believed to include internal waves, Langmuir circulations, and other phenomena involving vertical or horizontal transport and compression of surfactants. We report the rates of transport and deposition of four naturally occurring surface-active organic materials to the scawatcrvair interface by an ascending current field. Our results indicate that the susceptibility of thcsc materials to transport bv current follows the same relative order as thcir susceptibility to transport by bubbles (although the latter ratc is dramatically greater). The current transport results obtained can be explained by standard surface adsorption kinetics. Our data also indicate that subtle variations in the chemical structure and polarity of different materials may he major determining factors influencing their transport to the sea surface by currents.

A model for microbubble scavenging of surface‐active lipid molecules from seawater

“…It should be noted that a 1% void fraction is typically 2 or more orders of where n is now the total quantity of surfactant at the water surface and where w is a characteristic velocity near the water surface. The characteristic velocity is unknown; however, for identical mixing processes, we have dn /dns_ k. dt / dt kas (28) Brown et al [1992] find k,/k,s as 5.397 for oleic acid, 0.741 for triolein, and 0.050 for cholesterol. These ratios compare favorably with those given in Table 5.…”

Surfactant Scavenging and Surface Deposition by Rising Bubbles

“…After 120 s of bubbling, the authors estimated that surface waves of less than 20 cm wavelength would be significantly damped by the surface concentrations achieved (15). Later work by the same group found that bulk surface enrichment of surfactants by currents alone was at least two orders of magnitude less effective than by moderate bubbling (16). Based on these and other experimental findings, a model was presented for surfactant scavenging by vigorously buoyant compact plumes of bubbles in the range of from 200 to 750 m with high volume fractions of a few percent (17).…”

“…With the covariance terms known to be small, [15], [16], and [17] reduce to a closed differential-algebraic system of equations. The steady-state surfactant concentration in the bulk fluid, including bubble induced mixing of surfactant and surfactant adsorption/desorption with bubble and bulk surfaces, is described by…”

“…To solve equations [15], [16], and [17] we must first resolve the closure problem presented by the unknown covariance terms. We proceed first to show that CЈ⌫Ј b is small by examining the ramifications of fluctuations in the bulk fluid concentration described by a periodic function with wavelength .…”

Supplementary material to "Concerted measurements of lipids in seawater and on submicron aerosol particles at the Cape Verde Islands: biogenic sources, selective transfer and high enrichments"

“…One physical parameter which shows a superficial correlation with bubble and/or current-transport susceptibility is specific gravity, also called relative density. An inverse relationship of this function with increased rates of surface accumulation by current seems logical since substances with lower densities would probably resist remixing into the water column once they have dissolved and concentrated at the air-water interface (Brown et al, 1992). Based on available density data from the literature presented within Table S7, we may roughly estimate that more nonpolar lipids such as FFA and ALC should have higher susceptibility for the air-water surface (surface accumulation) in comparison to GL and PP.…”