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

Abstract

We have examined microbubble scavenging of four different types of lipid materials (oleic acid, stearic acid, triolein, and cholesterol) from seawater. These experiments have covered a range of bubble diameters (approximately 200 to 750 μm), bubble Reynolds numbers (approximately 10 to 150), and bubble void fractions (approximately 0.08% to 1.3%). We present here a model which synthesizes the experimental results. The model is based on turbulent diffusion to a single bubble coupled with experimentally determined adsorption kinetics. We have also introduced into the model a factor to account for the dependency of the scavenging observations on bubble void fraction. The introduction of this factor can be anticipated, because the flow hydrodynamics of single bubbles and bubble plumes are quite different. However, these differences are not well enough understood at this time to permit a thorough theoretical explanation of the void fraction factor.

Light-enhanced primary marine aerosol production from biologically productive seawater

“…To evaluate the nature of diel variability in greater detail, influences of surfactant depletion via bubble scavenging on PE during daytime were quantified by turning off the seawater flow through the generator for approximately 30 min each at WACS‐S1 and WACS‐S2 and approximately 60 min each over two discrete intervals during CalNex; thereafter, continuous seawater flow was restored. These nonflowing conditions are comparable to those in previous studies that employed aerosol generators with fixed volumes of seawater that were not replenished, during which adsorption of seawater surfactants onto bubble surfaces and transport to the surface depleted surfactant concentrations in bulk solution [ Skop et al , ; Stefan and Szeri , ].…”

Surfactant Scavenging and Surface Deposition by Rising Bubbles

“…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). As we have mentioned, these conditions are considerably removed from what one can expect to find in the far wake of ships (18,6); they are perhaps more representative of near-wake conditions.…”

“…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 .…”

“…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…”

Measuring Partition Coefficients of Colloids at Air−Water Interfaces

“…Enrichment of particleassociated heavy metals and organic compounds has been found at the surface of oceans and lakes (1)(2)(3)(4)(5)(6). Their very small sizes (nm to µm) give them high specific surface areas and often high surface charge densities.…”