Large-scale deposition of weathered oil in the Gulf of Mexico following a deep-water oil spill

TLDR

The Deepwater Horizon blowout in 2010 released an unprecedented amount of oil at depth (1,500 m) into the Gulf of Mexico. The study aims to assess the large‑scale deposition of hydrocarbons from the DWH spill to understand their long‑term fate, transformation, redistribution, and persistence. Sedimentary geochemical data from ~194,000 km² of the Gulf, comprising 2,613 cores and 158 hydrocarbon compounds, were used to map the amount, signature, distribution, and extent of DWH oil on the seafloor from 2010–2011. The analysis indicates that ~1.9 × 10⁴ metric tons of hydrocarbons (>C9) were deposited in 56 % of the area, representing 21 ± 10 % (up to 47 %) of the total oil discharged, with large weathered deposition in coastal and deep‑sea areas and negligible deposition on the continental shelf.

Abstract

The blowout of the Deepwater Horizon (DWH) drilling rig in 2010 released an unprecedented amount of oil at depth (1,500 m) into the Gulf of Mexico (GoM). Sedimentary geochemical data from an extensive area (∼194,000 km2) was used to characterize the amount, chemical signature, distribution, and extent of the DWH oil deposited on the seafloor in 2010-2011 from coastal to deep-sea areas in the GoM. The analysis of numerous hydrocarbon compounds (N = 158) and sediment cores (N = 2,613) suggests that, 1.9 ± 0.9 × 104 metric tons of hydrocarbons (>C9 saturated and aromatic fractions) were deposited in 56% of the studied area, containing 21± 10% (up to 47%) of the total amount of oil discharged and not recovered from the DWH spill. Examination of the spatial trends and chemical diagnostic ratios indicate large deposition of weathered DWH oil in coastal and deep-sea areas and negligible deposition on the continental shelf (behaving as a transition zone in the northern GoM). The large-scale analysis of deposited hydrocarbons following the DWH spill helps understanding the possible long-term fate of the released oil in 2010, including sedimentary transformation processes, redistribution of deposited hydrocarbons, and persistence in the environment as recycled petrocarbon.