The goal of this project will be to use coagulation theory to develop a predictive, mechanistic model for how oil coagulates with particulate material in the marine environment. There is strong observational evidence that oil interacts with particles in the marine environment forming heterogeneous aggregates comprised of oil droplets, mineral particles such as clay and silica, and biological particles such as phytoplankton cells, zooplankton fecal pellets, and marine snow (large heterogeneous aggregates). Such oil-aggregates have been observed in surface waters and in sediment traps, indicating that oil contained in these aggregates can be transported vertically from the surface to the deep ocean, ultimately providing a flux of oil to the seafloor. Estimates from the Deepwater Horizon oil spill suggest that oil released into the environment accumulated at the seafloor as a result of such interactions, potentially affecting an area of at least 3,200 km2. However, sinking of oil associated with aggregates is rarely incorporated into models of the transport of oil, which focus on the distribution of oil by currents.
The PIs propose to build on their combined expertise to develop a depth-dependent model of the coagulation of oil with marine particles to determine the dominant factors governing oil-particle interactions and to predict rates and timing of sedimentation of oil associated with aggregates to the sea floor. They will use detailed particle observations, including size distributions and abundances, from the NE Gulf of Mexico, and observations from sediment traps and laboratory experiments, to develop and validate the model. The model will also incorporate environmental variables such as water temperature and salinity profiles. Multiple simulations will be run, varying factors that affect coagulation rates; e.g. oil-droplet size distributions, phytoplankton cell sizes, salinity, and mineral particle concentrations. From the results of these simulations the investigators will develop parameterizations that can be incorporated into predictive models of oil transport and deposition. The goal will be to build a generic framework that can be used in different locations with appropriate parameterization as part of an oil spill emergency response tool.
This proposal directly addresses the GOMRI Research Theme 1, "Physical distribution, dispersion, and dilution of petroleum (oil and gas), its constituents, and associated contaminants (e.g., dispersants) under the action of physical oceanographic processes, air-sea interactions, and tropical storms" and also directly addresses knowledge gaps identified in the GOMRI-funded MOSSFA Workshop report. Coagulation is a physical process, mediated by such physical oceanographic processes such as fluid shear and turbulence. However, these coagulation processes are not generally represented in models, thereby making predictions of oil deposition less certain. The development of accurate parameterizations will directly improve the community's ability to quantitatively model the distribution of petroleum and its constituents under a wide variety of oceanic conditions. This will have major societal implications by improving predictions of oil transport and areas that will be affected after a spill, and assisting emergency responders in understanding the physical conditions that will promote or hinder oil interactions with marine particles and the subsequent sedimentation to the deep ocean. This model will also help improve predictions of the impacts of oil spills on deep-sea biological communities by improving predictions of the footprint of oil deposition.
Project Research Overview (2016):
An overview of the proposed research activities from the GoMRI 2016 Meeting in Tampa.
Direct link to the Research Overview presentation.