Identifier

etd-04152009-172347

Degree

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

Document Type

Dissertation

Abstract

Important processes governing the fate and transport of light petroleum hydrocarbons in the Lower Mississippi River and other river delta systems are not adequately represented in existing oil spill models. In response, three methods were introduced to include the effects of dynamic annual discharges and variation of shoreline type on shoreline retention and re-floatation and the potential of oil- mineral aggregate formation based contributing environmental factors. Parcel tracking was used, in conjunction with detailed shoreline types correlated to flow rate, to evaluate the benefits of using multiple shoreline re-floatation half lives correlated to shoreline type instead of a single half life for total shoreline. At low flow rates, simulations with detailed delineation of shoreline type and multiple re-floatation half lives predicted that ~35% more oil re-floated than when a single shoreline type was used. In addition to shoreline type, river geometry and the hydrodynamics significantly influenced the distribution of oil along the shoreline. To evaluate the accuracy of mass balance estimates, potential oil- mineral aggregate (OMA) formation was quantified during four distinctly different states of the river during a year with different combinations of salinity, suspended sediments, discharge and temperature. The peak season for OMA formation in the river for the two lighter oils was found to be winter and spring when high sediment availability supports the process. The peak season for the dense, high viscosity oil was summer when the low flow rates and approaching salt wedge increased the river’s salinity. Typical dispersion modeling does not account for OMA providing inaccurate mass balances since as much as 36% of an oil spill has the potential to reach the Gulf of Mexico as OMA, depending on environmental conditions and spill characteristics. The methodology and resulting conclusions were verified by implementing the methods introduced in previous chapters to hindcast the trajectory and assess the mass balance of the DM932 spill that occurred in New Orleans on July 23, 2008. The incorporation of the multiple half live method resulted in an improved model capable of replicating actual spill data.

Date

2009

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Clinton Willson

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