Isotope Studies of Methane Sources in Large Marine Anoxic Basins

摘要：本研究旨在通过考虑海洋源端组分的同位素组成来更好地约束甲烷CH4的全球生物地球化学循环。最近，人们对海洋甲烷包合物地球化学的几个方面重新产生了兴趣，提出了一些有趣的问题，这些问题很可能由所提出的同位素信息提供。甲烷以海底天然气水合物的形式存在，可能是地球上已知最大的碳氢化合物储藏库。至少出于两个原因，充分了解海洋中的甲烷循环是很重要的：1)评估其作为能源的潜力；2)评估其过去和未来从海洋排放的气体对大规模气候变化的影响。甲烷是一种强大的温室气体，其辐射影响接近。是二氧化碳的25倍。该项目的研究人员将测量水柱中甲烷的天然同位素组成（d 13C-CH4和d 2H-CH4，以及一些d 14C-CH4的测量），以及沉积物中可疑的端元源，以构建成分混合模型。这项工作利用了缺氧盆地（如黑海）的有限循环，利用上面的水柱来整合不同来源的影响，以及当CH4通过水柱时发生的过程。这项研究将建立并扩展对d13c - ch4和d2h - ch4的初步测量，这些测量是在1988年黑海考察中收集的样本上进行的。

ABSTRACTOCE-0099280This study sets out to better constrain the global biogeochemical cycle of methane, CH4, by a consideration of the isotopic composition of oceanic source end members. Recent renewed interest in several aspects of the geochemistry of marine methane clathrates poses a number of intriguing problems that the proposed isotopic information is likely to inform. Methane, in the form of submarine gas hydrates, potentially represents the largest known reservoir of hydrocarbons on the planet. It is important to fully understand the methane cycle in the oceans for at least two reasons, i) evaluation of its potential as an energy source, and ii) evaluation of the propensity of its past and future outgassings from the ocean to effect large scale climatic change. Methane is a powerful greenhouse gas, with a radiative impact approx. 25 times that of CO2. The investigators on this project will measure the natural isotopic composition of methane (d 13C-CH4 and d 2H-CH4 in addition to some measurements of D 14C-CH4) from the water column as well as suspected end-member sources in sediments in order to construct composition mixing models. The work takes advantage of the restricted circulation of anoxic basins such as the Black Sea, using the overlying water column to integrate the effects of different sources of and processes taking place on CH4 as it passes through the water column. The study will build on and extend preliminary measurements on d 13C-CH4 and d 2H-CH4 made on samples collected from a 1988 Black Sea expedition.