Evaluation of Possible Inputs of Oil From the Deepwater Horizon Spill to the Loop Current and Associated Eddies in the Gulf of Mexico

Abstract

Monitoring and M A Record-Breakin Geophysical Mon Copyright 2011 b 10.1029/2011GM The results of the analyses of 282 discreet water samples collected at various depths throughout the water column in the area of the Loop Current and associated eddies in the Gulf of Mexico are reported. No subsurface colored dissolved organic matter fluorescence maximum or oxygen minimum were observed, so samples were collected at standard depths. The concentration of Deepwater Horizon (DWH) total oil equivalents (TOE) estimated from total scanning fluorescence (TSF) maximum intensities ranged from less the practical quantitation limit (PQL) of 0.70 to 5.04 μg L . The presence of petroleum could not be confirmed in two thirds of the water samples having TOE below the PQL. Forty-eight samples were analyzed by gas chromatography/mass spectrometry for polycyclic aromatic hydrocarbons (PAHs) from primarily samples with higher TOE and from a few samples at the PQ. Of these 48 samples, 35% had PAH concentrations less than or equal to the procedural blank. These concentrations are in the lower range of historical prespill reported results. The oil detected could be from the DWH oil spill as oceanographic currents could have carried the oil from the region of the spill to the sampling sites. If the DWH oil spill was the source of the hydrocarbons detected, the oil would have to have been weathered and greatly diluted by the time it reached these sampling stations. The possibility of other potential sources of oil at the sampling locations cannot be ruled out, including oil from natural seepage, small unrelated discharges, contamination from shipping activities, and atmospheric deposition. Total scanning fluorescence is shown to be a very sensitive indicator of the presence of oil and serves as a valuable screening tool.