Oil-material fractionation in Gulf deep water horizontal intrusion layer: Field data analysis with chemodynamic fate model for Macondo 252 oil spill

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• 作者：A.T. Melvin^a ; L.J. Thibodeaux^a ; ^{thibod@lsu.edu" class="auth_mail" title="E-mail the corresponding author} ; A.R. Parsons^c ; E. Overton^b ; K.T. Valsaraj^a ; K. Nandakumar^a
• 关键词：Deepwater horizon ; Oil-material trapping layer ; Chemodynamics ; Sub-surface plume ; Far field modeling
• 刊名：Marine Pollution Bulletin
• 出版年：2016
• 出版时间：15 April 2016
• 年：2016
• 卷：105
• 期：1
• 页码：110-119
• 全文大小：903 K

文摘

Among the discoveries of the Deepwater Horizon blowout was the so-called “sub-surface plume”; herein termed the “oil-trapping layer”. Hydrocarbons were found positioned at ~ 1100–1300 m with thickness ~ 100–150 m and moving horizontally to the SW in a vertically stratified layer at the junction of the cold abyssal water and the permanent thermocline. This study focuses on its formation process and fate of the hydrocarbons within. The originality of this work to the field is two-fold, first it provides a conceptual framework which places layer origin in the context of a horizontal “intrusion” from the near-field, vertical, blow-out plume and second, it offers a theoretical model for the hydrocarbon chemicals within the horizontal layer as it moves far-afield. The model quantifies the oil-material fractionation process for the soluble and fine particle. The classical Box model, retrofitted with an internal gradient, the “G-Box”, allows an approach that includes turbulent eddy diffusion coupled with droplet rise velocity and reactive decay to produce a simple, explicit, transparent, algebraic model with few parameters for the fate of the individual fractions. Computations show the soluble and smallest liquid droplets moving very slowly vertically through the layer appearing within the trapping layer at low concentration with high persistence. The larger droplets move-through this trapping zone quickly, attain high concentrations, and eventually form the sea surface slick. It impacts the field of oil spill engineering science by providing the conceptual idea and the algorithms for projecting the quantities and fractions of oil-material in a deep water, horizontal marine current being dispersed and moving far afield. In the field of oil spill modeling this work extends the current generation near-field plume source models to the far-field. The theory portrays the layer as an efficient oil-material trap. The model-forecasted concentration profiles for alkanes and aromatics against the available field data support the proposed theory and the resulting model.