Using Carbon Isotope Fractionation to Constrain the Extent of Methane Dissolution Into the Water Column Surrounding a Natural Hydrocarbon Gas Seep in the Northern Gulf of Mexico
Using Carbon Isotope Fractionation to Constrain the Extent of Methane Dissolution Into the Water Column Surrounding a Natural Hydrocarbon Gas Seep in the Northern Gulf of Mexico
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DOI：
10.1029/2018gc007705
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发表时间：
2018-11
期刊：
影响因子：
3.7
通讯作者：
M. Leonte;B. Wang;S. Socolofsky;S. Mau;J. Breier;J. Kessler
中科院分区：
文献类型：
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作者：
M. Leonte;B. Wang;S. Socolofsky;S. Mau;J. Breier;J. Kessler
位于墨西哥湾北方的气泡渗漏进行了几天的调查，以确定是否可以使用甲烷的稳定碳同位素比的变化作为甲烷溶解通过水柱的示踪剂。在海底和整个水柱中采集气泡和水样，进行甲烷同位素比分析。我们的研究结果表明，甲烷同位素比值的变化与测量甲烷溶解的同位素分馏的实验室实验是一致的。瑞利同位素模型应用于同位素数据，以确定在每个深度溶解的甲烷的分数。平均而言，甲烷溶解的比例超过90%超过海拔400米以上的海底。甲烷溶解也进行了研究，使用修改版本的得克萨斯州A&M石油泄漏（排放口）计算器（TAMOC），其中甲烷同位素比的变化可以计算。TAMOC模型的结果表明，溶解取决于深度和气泡的大小，解释了在我们的调查中测量的同位素比的传播。Rayleigh和TAMOC模型都表明，甲烷气泡从海底排放后很快溶解。总之，这些结果表明，可以使用天然甲烷同位素的测量来限制海底排放后甲烷溶解的程度。
A gas bubble seep located in the northern Gulf of Mexico was investigated over several days to determine whether changes in the stable carbon isotopic ratio of methane can be used as a tracer for methane dissolution through the water column. Gas bubble and water samples were collected at the seafloor and throughout the water column for isotopic ratio analysis of methane. Our results show that changes in methane isotopic ratios are consistent with laboratory experiments that measured the isotopic fractionation from methane dissolution. A Rayleigh isotope model was applied to the isotope data to determine the fraction of methane dissolved at each depth. On average, the fraction of methane dissolved surpasses 90% past an altitude of 400 m above the seafloor. Methane dissolution was also investigated using a modified version of the Texas A&M Oil spill (Outfall) Calculator (TAMOC) where changes in methane isotopic ratios could be calculated. The TAMOC model results show that dissolution depends on depth and bubble size, explaining the spread in measured isotopic ratios during our investigations. Both the Rayleigh and TAMOC models show that methane bubbles quickly dissolve following emission from the seafloor. Together, these results show that it is possible to use measurements of natural methane isotopes to constrain the extent of methane dissolution following seafloor emission.