Modeling Distribution, Fate, and Concentrations of Deepwater Horizon Oil in Subsurface Waters of the Gulf of Mexico

doi:10.1016/B978-0-12-804434-6.00031-8

Oil Spill Environmental Forensics Case Studies

2018, Pages 683-735

https://doi.org/10.1016/B978-0-12-804434-6.00031-8 Get rights and content

Abstract

Oil spill modeling of the 2010 Deepwater Horizon discharge was performed to evaluate the fate of the oil in subsurface waters of the Gulf of Mexico. The oil fate model Spill Impact Model Application Package (SIMAP) was used to estimate rise rate of oil droplets, dissolution of oil constituents, movements of oil droplets and dissolved components, and degradation of hydrocarbon components in the deep-sea. As sampling during April–July 2010 was primarily performed within 20 km of the spill site, model predictions were compared to field data from within a 25-by-25-km box centered on the wellhead. Concentrations of soluble and semisoluble hydrocarbon components predicted by the model agreed well with chemical measurements when compared as frequency distributions within varying depth zones of the water column. The results showed that the soluble hydrocarbons primarily dissolved near the release depth, while semisoluble compounds were partially dissolved at depth and as droplets rose.

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Cited by (33)

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Fluorescence-estimated oil concentration (F<inf>oil</inf>) in the Deepwater Horizon subsea oil plume
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Counter-historical study of alternative dispersant use in the Deepwater Horizon oil spill response
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2021, Marine Pollution Bulletin
Citation Excerpt :
Concentrations of S&SS compounds (Table A-3 in Appendix A; from Stout, 2015a, Stout et al., 2016a) were very similar to those measured by Reddy et al. (2012) using a pressure-tight sample taken just above the wellhead on 21 June 2010. Each of the modeled pseudo-components were assigned physical-chemical properties and empirically based biodegradation rates using mass-weighted means for the individual compounds (French-McCay et al., 2015, 2018a, 2018c; summarized in French-McCay et al. (2021b) and Table A-4, Appendix A). The bulk properties of the oil released to the farfield were based on measurements of oil collected on 21 May 2010 from the riser insertion tube that was receiving oil and gas directly from the well's broken riser near the sea floor (Stout, 2015b).
Model predictions of oil transport and fate for the 2010 Deepwater Horizon oil spill (Gulf of Mexico) were compared to field observations and absolute and relative concentrations of oil compounds in samples from 900 to 1400 m depth <11 km from the well. Chemical partitioning analyses using quantitative indices support a bimodal droplet size distribution model for oil released during subsea dispersant applications in June with 74% of the mass in >1 mm droplets that surfaced near the spill site within a few hours, and 1–8% as <0.13 mm microdroplets that remained below 900 m. Analyses focused on 900–1400 m depth <11 km from the well indicate there was substantial biodegradation of dissolved components, some biodegradation in microdroplets, recirculation of weathered microdroplets into the wellhead area, and marine oil snow settling from above 900 m carrying more-weathered particulate oil into the deep plume.
Oil fate and mass balance for the Deepwater Horizon oil spill
2021, Marine Pollution Bulletin
Citation Excerpt :
The direction and speed of transport in the offshore environment did not greatly affect the fate processes and so did not significantly affect the mass balance. Thus, comparison of the model and observed trajectories are not reviewed here, but are provided in French-McCay et al. (2015a, 2018a, 2018c, 2021a). Based on these model simulations, one set of forcing data, that which led to the best fit with the observations overall (described in Section 2.6), was used for the model simulations examined herein.
Based on oil fate modeling of the Deepwater Horizon spill through August 2010, during June and July 2010, ~89% of the oil surfaced, ~5% entered (by dissolving or as microdroplets) the deep plume (>900 m), and ~6% dissolved and biodegraded between 900 m and 40 m. Subsea dispersant application reduced surfacing oil by ~7% and evaporation of volatiles by ~26%. By July 2011, of the total oil, ~41% evaporated, ~15% was ashore and in nearshore (<10 m) sediments, ~3% was removed by responders, ~38.4% was in the water column (partially degraded; 29% shallower and 9.4% deeper than 40 m), and ~2.6% sedimented in waters >10 m (including 1.5% after August 2010). Volatile and soluble fractions that did not evaporate biodegraded by the end of August 2010, leaving residual oil to disperse and potentially settle. Model estimates were validated by comparison to field observations of floating oil and atmospheric emissions.

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Chapter 31 - Modeling Distribution, Fate, and Concentrations of Deepwater Horizon Oil in Subsurface Waters of the Gulf of Mexico

Abstract