Crude oil is released into oceanic waters through production, transport, offshore exploration, and natural seeps. In spite of the significant environmental impacts of oil spills and substantial research efforts, many of the processes affecting the fate of oil spills are still unclear. Consequently, the scientific and engineering communities still lack significant knowledge required to understand and predict the fate of spilled oil, as well as its environmental and human health impacts. The DROPPS II consortium (DROPPS: Dispersion Research on Oil: Physics and Plankton Studies) brings together complementing experts from seven institutions and diverse disciplines, including marine biology, chemistry, transport phenomena, computational modeling, imaging, and healthcare professionals. The goal of DROPPS II is to investigate and model a series of processes affecting the fate of crude oil spills, including physical breakup and dispersion of oil patches, interactions of petroleum with marine organisms, biodegradation of oil, and the impact of aerosolized oil on public health. The experimental and numerical studies will be performed at varying scales and levels of complexity, from 'bench-top' investigations that fully characterize specific phenomena, to multi-component, meso-scale experiments and simulations that mimic realistic physical and biological conditions.
Physical processes affecting the breakup, distribution, dispersion, and settling of oil
Shortly after a spill, physical processes break a portion of the insoluble oil fraction (majority) into droplets, which are then entrained and transported by subsurface currents and wind. The size distribution of these droplets, which affects their transport and subsequent interactions, depends on the processes involved and the oil properties. An extensive series of experimental studies, many of them unique in terms of scales and associated instrumentation, complemented with computational modeling at varying levels of detail, will investigate physical processes involved with the breakup, generation, and transport of oil droplets below and above the water surface. Particular attention will be paid to the effects of dispersants, which drastically reduce the interfacial tension, and method of applying them, on the size and spatial distributions of droplets, as well as the subsequent suspension dynamics. A suite of state-of-the-art instruments will be used to track and characterize the droplets, e.g., high-speed imaging and holographic microscopy, light scattering sensors, as well as scanning mobility and aerodynamic particle sizers. Modeling will include applications of smoothed particle hydrodynamics to characterize wave breaking and fractal-based analysis for modeling non-spherical oil-particle aggregates.
Biological and chemical degradation of oil by marine organisms and the environment
The interfacial properties and chemical composition of subsurface oil change as it interacts with the chemical, biological, and physical environments. Biological interactions with planktonic organisms contributing to the 'biodegradation' of oil include consumption by marine animals and protists, colonization by bacteria and resulting formation of biofilms, and entrapment within biologically derived flocculent material (i.e., marine snow). The rates of biodegradation and oxidation of the oil are affected by environmental conditions along its path. The impact of environmental parameters, such as temperature, solar irradiance, and presence of nutrients, on the biodegradation of oil will be characterized. Results of incubation experiments will be evaluated using gas chromatography, mass spectrometry, flow-cytometry, and tag pyrosequencing.
Potential Impact of aerosolized oil on public health
Since dispersants enhance the generation of micron size droplets, it increases the likelihood of atmospheric transport by wind, and the potential for interaction with humans. Yet, little is known about the hazards to human health from exposure to oil and dispersants. Consequently, the DROPPS II consortium will use measured size distribution of aerosolized micro droplets in the 0.01 to 10 ?m size range in the physical facilities and use these data to model the transport potential of these small oil droplets, and effects of contact with the human respiratory tract. Chemical and microbial analyses of aerosolized byproducts of biofilms, along with endotoxins associated with proinflammatory response, will also be performed. An available lung cell exposure system will be used to determine the effects of these droplets on human lung cells, e.g., carcinogenic processes, cytotoxicity, cell death, barrier function, inflammation, and fibrosis.
Meso-Scale modeling of oil transport
Statistics of droplet size distributions, transport, aggregation, and biodegradation, as well as results of fine scale computational models, will be integrated to improve a large-scale computational model predicting the fate of an oil spill, as well as developing tools for assessing response options in future spills, such as burns, skimming, dispersant effectiveness, etc. The model predictions will be compared to surface oil observed during the Deepwater Horizon spill.
Project Research Overview (2015):
An overview of the proposed research activities from the GoMRI 2015 Meeting in Houston.
Direct link to the Research Overview presentation.