Validation of oil fate and mass balance for the Deepwater Horizon oil spill: Evaluation of water column partitioning

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.

Automated summary

Comparisons were made between model predictions and field observations of the 2010 Deepwater Horizon oil spill in the Gulf of Mexico, showing that a significant amount of oil compounds were present in the form of microdroplets below 900 meters. The analyses also revealed processes such as biodegradation, recirculation of weathered microdroplets, and settling of marine oil snow carrying weathered particulate oil into the deep plume.