Cayla Whitney Dean

Surface Dynamics of Crude and Weathered Oil in the Presence of Dispersants: Laboratory Experiment and Numerical Simulation

Marine oil spills can have dire consequences for the environment. Research on their dynamics is important for the well-being of coastal communities and their economies. Propagation of oil spills is a very complex physical-chemical process. As seen during the Deepwater Horizon event in the Gulf of Mexico during 2010, one of the critical problems remaining for prediction of oil transport and dispersion in the marine environment is the small-scale structure and dynamics of surface oil spills. The laboratory experiments conducted in this work were focused on understanding the differences between the dynamics of crude and weathered oil spills and the effect of dispersants. After deposition on the still water surface, a drop of crude oil quickly spread into a thin slick; while at the same time, a drop of machine (proxy for weathered) oil did not show significant evolution. Subsequent application of dispersant to the crude oil slick resulted in a quick contraction or fragmentation of the slick into narrow wedges and tiny drops. Notably, the slick of machine oil did not show significant change in size or topology after spraying dispersant. An advanced multi-phase, volume of fluid computational fluid dynamics model, incorporating capillary forces, was able to explain some of the features observed in the laboratory experiment. As a result of the laboratory and modeling experiments, the new interpretation of the effect of dispersant on the oil dispersion process including capillary effects has been proposed, which is expected to lead to improved oil spill models and response strategies.

Surfactant-associated bacteria in the near-surface layer of the ocean from in-situ DNA sampling and SAR imaging

Certain marine bacteria found in the near-surface layer of the ocean are expected to play an important role in the production and decay of surface active materials. Identifying a connection between marine bacteria and the production of natural surfactants may provide a better understanding of the global picture of biophysical processes at the boundary between the ocean and atmosphere, air-sea exchange of gases, and production of climate-active marine aerosols. Kurata et al. (2016) and Hamilton et al. (2015) have developed measurement methodology combining DNA sampling of sea surface microlayer with SAR satellite technology. Following Franklin et al. (2005) and Cunliffe et al. (2011), these authors used polycarbonate membrane filters in order to minimize potential contamination that may occur with other sampling techniques. A hydrophilic polycarbonate filter, attached to the sea surface by capillary forces, collected bacteria effectively from a 35–42 μm surface layer. A fly fishing technique was used in Kurata et al. (2016) and Hamilton et al. (2015) to ensure that the filter sat on the sea surface for a few seconds (away from the vessel and its wake in order to avoid these sources of disturbance to measurements of the microlayer). Samples from the water column at approximately 0.2 m depth were taken with a peristaltic pump for comparison with the sea surface results.