Abstract:
The oil released during the Deepwater Horizon (DWH) oil spill may have both short- and long-time impacts on the northern Gulf of Mexico ecosystems. An understanding of how the composition and concentrations of the oil were altered by weathering, including chemical, physical and biological processes, is needed to evaluate the oil toxicity and impact on the ecosystem in the northern Gulf of Mexico. This study examined petroleum hydrocarbons in oil mousse collected from the sea surface and salt marshes, and in oil deposited in sediments adjacent to the wellhead after the DWH oil spill. Oil mousses were collected at two stations (OSS and CT located 130 and 85 km away from the wellhead, respectively) in May 2010, and two sediment samples from stations SG and SC, within 6 km of the wellhead in May 2011. We also collected oil mousse from salt marshes at Marsh Point (MP), Mississippi, 186 km away from the wellhead in July 2010. In these samples, n-alkanes, polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs, BTEX (collective name of benzene, toluene, ethylbenzene, and p-, m-, and o-xylenes) and C3-benzenes, and trace metals were measured to examine how the oils were altered chemically. The chemical analysis indicates that the oil mousses underwent different degrees of weathering with the pattern of OSS<CT<MP. This pattern is consistent with the projected oil mousse movement from the accident site to salt marshes. Also, contents of trace metals Al, V, Cr, Fe, Mn, Ni, Co, Cu, As and Pb in oil mousse generally increased along the way to salt marshes, indicating that these trace metals were perhaps aggregated into oil mousse along the transport. Petroleum hydrocarbon data revealed that the oil deposited in sediments underwent only light to moderate degradation one year after the DWH oil spill, as supported by the presence of short-chained n-alkanes (C10- C15), BTEX, and C3 benzenes. The weathering of oil in sediment may result from biological degradation and dissolution, evidenced by the preferentially loss of mid-chained n-alkanes C16-C27, lower ratios of n-C17/Pr and n-C18/Ph, and preferentially loss of PAHs relative to alkylated PAHs.
Suggested Citation:
Liu, Zhanfei. 2013. Petroleum hydrocarbons in oil mousse in surface waters and oil-contaminated sediments adjacent to the wellhead, Marsh Point, 2010-05-20 to 2010-07-30.. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7W95745
Purpose:
To evaluate the oil toxicity and impact on the ecosystem in the northern Gulf of Mexico; To examine petroleum hydrocarbons in oil mousse collected from the sea surface and salt marshes, and in oil deposited in sediments adjacent to the wellhead after the DWH oil spill.
Data Parameters and Units:
alkanes, polycyclic aromatic hydrocarbons, trace metals; normalized to total solvent-extractable materials (TSEM); units as mg or ug per gram.
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