Characterization of sediment around Dauphin Island, Alabama for a biological context of ecosystem recovery related to the BP Horizon oil spill




Williams, Stephani C.

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On April 20, 2010, a faulty blow out preventer destroyed the BP Deepwater Horizon oil drilling platform releasing 4.9 million barrels of oil into the Gulf of Mexico affecting ecosystems around the coast. Ongoing studies are exploring ecological impacts of the oil spill around or adjacent to Dauphin Island, Alabama. This research contributes geological data to enhance biological interpretations by characterizing the geological influence on the recovery of this ecosystem to its pre-Deepwater Horizon state. Two components define this research: 1) mineralogical analysis and 2) granulometric analysis. This thesis reports results of granulometric analysis, X-ray Diffraction (XRD) bulk mineralogical analysis, and scanning electron microscope/energy dispersive X-ray analysis (SEM/EDS) for samples collected around Dauphin Island, AL. XRD analysis reveals that all samples are composed of quartz, suggesting very little oil may have been absorbed by, and retained in, the sediments. SEM/EDS analysis reveals the presence of a clay coating on some grains as well as feldspar and skeletal grains present below the XRD detection limit. Additionally, SEM/EDS shows hydrocarbons to be present in some pore spaces or adhering to grains. Granulometric analysis reveals primarily medium sized sand grains and an insignificant amount of clay sized particles. Grain size distribution is significant as oil retention is a surface area controlled phenomenon and clays and fine particles are more likely to retain both oil and oil-related toxins that may be released in the future.


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