With funding through this Grant for Rapid Response Research (RAPID), researchers at the University of Southern Mississippi will examine the Deepwater Horizon oil spill in the northern Gulf of Mexico -- an oil spill of national significance -- to study the fate, transport and transformation of crude oil components and their interactions with marine organic matter from baseline to maximum impact in a complete time series. Their working hypothesis is that the crude oil components are isotopically light (in terms of carbon-13) and distinct in optical properties (UV-vis and fluorescence emission-excitation matrices [EEM]) from natural marine organic matter, thus allowing the use of stable isotopes and fluorescence techniques for quantitative understanding of their fate, transport, and transformations in the northern Gulf of Mexico. They will collect seawater samples at a station in the Mississippi Bight in the northern Gulf of Mexico from base line conditions to maximum impact. EEM fluorescence, stable isotopes, and flow field-flow fractionation techniques will be employed. Measurements will include dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and particulate organic carbon (POC) and their stable carbon isotopic composition (C-13), optical properties, including UV-vis absorbance, adsorption coefficient, spectral slope, and EEMs, composition and size spectrum of DOM, chlorophyll-a, and other common environmental parameters, such as salinity, temperature, dissolved oxygen, and nutrients. Results of this study are expected to provide new insights into how organic matter from oil spills interacts with marine organic matter affecting the ocean carbon budget, biogeochemical processes, and marine ecosystems as a whole.
Broader Impacts Combined with planned and ongoing research in response to this unprecedented oil spill in the northern Gulf of Mexico, this research will contribute to the understanding of the fate, transport and transformation of spilled oils and their interactions with natural marine organic matter in the water column in the coastal environment. The investigators will collaborate with other funded projects for data sharing. The project will support one graduate student, who will gain valuable experience in rapid response research as well as in interacting with other research teams in the Gulf Coast region.
Reject outcomes report The Deepwater Horizon oil spill in the northern Gulf of Mexico — an oil spill of national significance —provides an unfortunate opportunity and a natural laboratory to examine the fate, transport and transformation of oil components and their interactions with marine organic matter. Water samples and oil were collected from maximum oil impact to post spill clean up/recovery period three months and fifteen months after the oil spill was capped for the measurements of different carbon species including dissolved, colloidal, and particulate organic carbon, and optical properties including ultraviolet absorbance and fluorescence excitation-emission matrices (EEMs). Laboratory experiments were also carried out to examine the degradation kinetics and chemical evolution of oil during photochemical and biological degradation. We found that the Macondo crude oil had its maximum fluorescence intensities centered on 226/340 nm, located under the excitation wavelength between 220–240 nm and emission wavelength between 320-360 nm. Parallel factor modeling, PARAFAC, revealed three oil-related components corresponding to crude and weathered oil in the water column during oil spill. Based on our results from both field studies and laboratory experiments, we found that fluorescence intensity ratios between oil components, showing a consistent increase with increasing time from 2010 to 2011 in the Gulf of Mexico, can be quantitatively used a compelling index or proxy to effectively track the fate, transport, and transformation of crude oil in the water column.
