A tale of two recent spills--comparison of 2014 Galveston Bay and 2010 Deepwater Horizon oil spill residues

Abstract

Managing oil spill residues washing onto sandy beaches is a common worldwide environmental problem. In this study, we have analyzed the first-arrival oil spill residues collected from two Gulf of Mexico (GOM) beach systems following two recent oil spills: the 2014 Galveston Bay (GB) oil spill, and the 2010 Deepwater Horizon (DWH) oil spill. This is the first study to provide field observations and chemical characterization data for the 2014 GB oil spill. Here we compare the physical and chemical characteristics of GB oil spill samples with DWH oil spill samples and present their similarities and differences. Our field observations indicate that both oil spills had similar shoreline deposition patterns; however, their physical and chemical characteristics differed considerably. We highlight these differences, discuss their implications, and interpret GB data in light of lessons learned from previously published DWH oil spill studies. These analyses are further used to assess the long-term fate of GB oil spill residues and their potential environmental impacts.

Fig 1. Locations of the two oil spills and sampling points: a) Galveston Bay spill; and b) Deepwater Horizon spill (maps from OpenStreetMap).

Fig 2. Comparison of Galveston Bay and Deepwater Horizon oil spill deposition patterns: a) blackish oily material deposited on a sandy beach in Galveston Bay, Texas (Photo taken on March 23^rd, 2014, by NOAA's Office of Response and Restoration); b) brownish emulsified oil deposited on a sandy beach in Orange Beach, Alabama (Photo taken on June 11^th, 2010, by Auburn University team).

Fig 3. Field observation made at the Texas Dike road (Photographs taken on March 29^th 2014, by Auburn University team): a) oil sheen observed in nearshore water; b) oil on a plastic sheet and rocks; c) oil on rocks and on a beached soccer ball and other objects; and d) beached oil blobs observed close to the waterline.

Fig 4. Comparison of extracted ion chromatograms of n-alkanes (m/z of 57) for Galveston Bay and Deepwater Horizon oil spill residues.

Fig 5. Concentration levels of various n-alkanes (ranging from C₁₃ to C₃₀) measured in Galveston Bay and Deepwater Horizon oil spill residues.

Fig 6. Comparison of extracted ion chromatograms of hopanes (m/z of 191) for Galveston Bay and Deepwater Horizon oil spill residues.

Fig 7. Radar plots of hopane diagnostic ratios of Galveston Bay and Deepwater Horizon oil spill residues.

Fig 8. Comparison of extracted ion chromatograms of steranes (m/z of 217) for Galveston Bay and Deepwater Horizon oil spill residues [Peak 1: DiaC₂₇βα(S); Peak 2: DiaC₂₇βα(R); Peak 3: C₂₇ααα(S); Peak 4: C₂₇αββ(R); Peak 5: C₂₇αββ(S); Peak 6: C₂₇ααα(R); Peak 7: C₂₈ααα(S); Peak 8: C₂₈αββ(R); Peak 9: C₂₈αββ(S); Peak 10: C₂₈ααα(R); Peak 11: C₂₉ααα(S); Peak 12: C₂₉αββ(R); Peak 13: C₂₉αββ(S); Peak 14: C₂₉ααα(R)].

Fig 9. Concentration levels of various PAHs and alkylated PAH homologs measured in Deepwater Horizon and Galveston Bay oil spill residues.