Characterization of adsorbed microlayer thickness on an oceanic glass plate sampler

Abstract

The thickness of solution layers adsorbed onto rotating glass plates designed for use on an oceanic glass plate sampler was investigated in laboratory experiments using optical techniques. Using the Beer‐Lambert Law, light attenuation measurements were used to calculate the thickness of adsorbed solution layers on a rotating glass disk with and without salt and surfactants. The observations have shown that the adsorbed film thickness can vary between 80 and 40 µm for glass rotation speeds between 4 and 16 cm s−1, depending on salinity and surfactant concentrations. For example, the thickness of a film of water with 40 ppt of salt and 5 cm s−1 rotation speed was in the range of 80 µm. The adsorbed layer thickness increases with increasing salt concentration and with increasing concentrations of surface active substances. These results are comparable to results obtained by vertically dipping a glass plate and determining film thickness from the collected volume of water. Because the glass disk rotational speed significantly influences the thickness of the adsorbed solution layer, it is important that the speed is maintained at a value for which the adsorbed thickness has been calibrated. At typical oceanic salinities, the dependence of the adsorbed film thickness on rotation speed was limited. However, even small changes in surface active substances resulted in significant thickness changes.

The Ocean's Skin Layer in the Tropics

“…The adhering skin layer is scraped off on the ascending side of the rotating discs by wipers and pumped through in situ sensors. Rotating glass drum and discs samplers have been shown to effectively collect the skin layer, that is, the sea surface microlayer (Carlson et al, ; Shinki et al, ). The thickness of the collected skin layer was estimated to be 80 μm based on the disc area, collected volume, and sampling time.…”

On the imprint of surfactant‐driven stabilization of laboratory breaking wave foam with comparison to oceanic whitecaps

“…Identifying the occurrence, distribution, and composition of the SML, its relation to the physical and chemical properties of the underlying water column, and establishing best practices for doing so, remains an active area of research [ Cunliffe and Wurl , ]. The SML is typically sampled using in‐situ methods encompassing a variety of techniques, each with their own merit, focus, and application [e.g., Garrett , ; Harvey , ; Harvey and Burzell , ; Shinki et al ., ]. Remote sensing techniques, both direct and indirect, have also been explored to monitor aggregations of surface active materials, which manifest as sea surface slicks [e.g., Cox and Munk , ; Cini et al ., ; Romano , ; Gade et al ., , and references therein].…”

Influence of solar radiation on biogeochemical parameters and fluorescent dissolved organic matter (FDOM) in the sea surface microlayer of the southern coastal North Sea

“…Samples of the SML are collected by partially (15 cm of the disc diameter) immersing the set of glass discs in the water. As the glass discs rotate, the SML adheres to them through surface tension, a process studied in detailed by Shinki et al (2012). The catamaran is equipped with a collection of sensors to record in situ data of various biogeochemical parameters in high resolution, including conductivity, temperature, FDOM and Chlorophyll a (Chl a) fluorescence.…”