Date of Award

11-13-2019

Document Type

Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

College

College of Science

First Advisor

Richard N. Peterson

Second Advisor

William Burnett

Third Advisor

Angelos Hannides

Additional Advisors

Samantha B. Joye; Susan M. Libes

Abstract

Petroleum pollution in the marine environment can be deleterious to coastal and marine ecosystems and can have sustained effects for years. While oil slicks on the surface of the ocean are tracked with relative ease using satellite-based technology, deep sea, neutrally-buoyant hydrocarbon plumes remain exceedingly difficult to track. We provide evidence for the utility of Ra-224 as a potential hydrocarbon tracer to determine the marine exposure time of crude oil. We employed time course incubations to constrain a time dependent Ra-224 release signature and tested a variety of timescales, temporal resolutions, oil sources, seawater, and experimental treatments to determine potential factors that contribute to the variability of Ra-224 release from hydrocarbons into seawater. Our results show quantitative release of Ra-224 from crude oil in contact with seawater and similar temporal variability (which increases with finer temporal resolution) in Ra-224 activity between two oil sources, regardless of the overall magnitude of release. The magnitude of Ra-224 release from crude oil is proposed to vary depending on the geochemistry of the source reservoir and biological activity therein as well as geochemical alterations as the oil flows through geologic conduits. Mechanisms of release are thought to be primarily associated with chemical degradation (i.e., photo- and bio-degradation) of the oil matrix and cation exchange processes. These interpretations warrant further investigation. However, our results provide the first evidence that release of Ra-224 from crude oil represents a disequilibrium from its particle-sorbed parent isotopes suggesting this isotope may be useful for examining the temporal dynamics of oceanic hydrocarbon plumes.

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