Department of Earth Science and Marine Science Institute, University of California, Santa Barbara, CA 93106;
Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole MA 02543; and.
Proc Natl Acad Sci U S A. 2014 Nov 11;111(45):15906-11. doi: 10.1073/pnas.1414873111. Epub 2014 Oct 27.
The sinking of the Deepwater Horizon in the Gulf of Mexico led to uncontrolled emission of oil to the ocean, with an official government estimate of ∼ 5.0 million barrels released. Among the pressing uncertainties surrounding this event is the fate of ∼ 2 million barrels of submerged oil thought to have been trapped in deep-ocean intrusion layers at depths of ∼ 1,000-1,300 m. Here we use chemical distributions of hydrocarbons in >3,000 sediment samples from 534 locations to describe a footprint of oil deposited on the deep-ocean floor. Using a recalcitrant biomarker of crude oil, 17α(H),21β(H)-hopane (hopane), we have identified a 3,200-km(2) region around the Macondo Well contaminated by ∼ 1.8 ± 1.0 × 10(6) g of excess hopane. Based on spatial, chemical, oceanographic, and mass balance considerations, we calculate that this contamination represents 4-31% of the oil sequestered in the deep ocean. The pattern of contamination points to deep-ocean intrusion layers as the source and is most consistent with dual modes of deposition: a "bathtub ring" formed from an oil-rich layer of water impinging laterally upon the continental slope (at a depth of ∼ 900-1,300 m) and a higher-flux "fallout plume" where suspended oil particles sank to underlying sediment (at a depth of ∼ 1,300-1,700 m). We also suggest that a significant quantity of oil was deposited on the ocean floor outside this area but so far has evaded detection because of its heterogeneous spatial distribution.
墨西哥湾深水地平线号的沉没导致石油失控地排入海洋，官方估计有∼500 万桶石油泄漏。围绕这一事件的紧迫不确定性之一是，据认为有∼200 万桶被淹没的石油被困在深海侵入层中，深度约为 1000-1300 米。在这里，我们使用来自 534 个地点的超过 3000 个沉积物样本中的碳氢化合物化学分布来描述沉积在深海海底的石油足迹。我们使用原油的一种难降解生物标志物 17α（H），21β（H）-藿烷（藿烷），确定了马贡多井周围一个受污染的 3200 平方公里区域，该区域含有∼1.8±1.0×10^6g 过量藿烷。基于空间、化学、海洋学和质量平衡的考虑，我们计算出这种污染代表了 4-31%的海洋深处封存的石油。污染的模式指向深海侵入层是污染源，最符合两种沉积模式：一种是富油层的水横向冲击大陆斜坡（在深度约 900-1300 米处）形成的“浴缸环”，另一种是悬浮油颗粒下沉到下面沉积物的高通量“沉降羽流”（在深度约 1300-1700 米处）。我们还表明，大量的石油沉积在该区域以外的海底，但由于其不均匀的空间分布，迄今为止尚未被发现。
