The Deep Water Horizon (DWH) oil spill resulted in the largest accidental release of crude oil in U.S. waters with both short- and long-term effects on the marine environment. Extensive studies conducted immediately following the oil spill in the northern Gulf of Mexico provided greater understanding of the physical processes influencing the distribution of the released oil, including the use of optical detection of polycyclic aromatic hydrocarbons (PAHs), a toxic crude oil fraction in the northern Gulf of Mexico. In this study, the optical properties of chromophoric dissolved organic matter (CDOM) and the concentrations of dissolved organic carbon (DOC) were examined from seawater samples collected during two cruises in April of 2012 and 2013 near the DWH spill site in the northern Gulf of Mexico. During both 2012 and 2013, eddies associated with the Loop Current appeared to strongly influence the hydrography at the study site with deeper mixed-layer depths in 2012 than in 2013. Average DOC concentrations were similar in 2013 (mean 0.96 +- 0.20 mg L-1) in comparison to 2012 (0.85 +- 0.25 mg L-1) with higher levels in the near surface waters than at depths. Absorption and fluorescence properties of CDOM for samples obtained in 2013 revealed both the characteristics and composition of CDOM near the DWH site. Absorption coefficients at 355 nm (aCDOM(355) m-1) used to quantify CDOM in seawater varied over a small range and showed elevated values at depths corresponding to or just below the chlorophyll fluorescence maxima suggesting autochthonous contribution to the CDOM pool. In contrast to river-influenced coastal regions, relationships between CDOM optical properties and salinity were not clear due to the small salinity range in the study region. Excitation-emission matrix fluorescence (EEMs) of CDOM revealed the presence of typical humic-like and protein-like fluorophores. Parallel factor analysis (PARAFAC) of EEMs resulted in four fluorescent components characterized as humic-like (two) and protein-like (two). Higher values of protein-like components both in surface and depth at stations with more elevated surface chlorophyll fluorescence north of the DWH suggests biological contribution to the CDOM pool and its fluxes to depths with implications to related fluxes of contaminants such as PAHs.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-01162014-211815 |
| Date | 31 January 2014 |
| Creators | Li, Zhi |
| Contributors | White, John, Maiti, Kanchan, D'Sa, Eurico |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-01162014-211815/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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