Collaborative Research: Characterization and mechanistic modeling of methane production, flow and ebullition from fine-grained sediments in a temperate lake

合作研究：温带湖泊细粒沉积物甲烷产生、流动和沸腾的特征和机制模拟

• 批准号: 1045193
• 负责人: Ruben Juanes
• 金额: $ 40.36万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-03-15 至 2015-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1045193&HistoricalAwards=false
• 关键词: Collaborative; Research; Characterization; mechanistic; modeling

Methane is a potent greenhouse gas, but its effects on Earth?s climate remain poorly constrained, in part due to uncertainties in global methane fluxes to the atmosphere. An important source of atmospheric methane is the methane generated in organic-rich sediments underlying surface water bodies, including lakes, wetlands, and the ocean. The fraction of the methane released from the sediments that bypasses dissolution in the water column and reaches the atmosphere may contribute significantly to global warming, and this fraction depends critically on the mode and spatiotemporal characteristics of free-gas venting from the underlying sediments. Advances in understanding methane ebullition require better mechanistic models of the hydrologic processes in the sediments, better understanding of the parameters and driving forces controlling gas production and accumulation, bubble growth, conduit evolution and persistence, vent spacing, ebullition rates, and the episodicity, frequency, and duration of venting events. The goal of this project is to develop quantitative models of methane production, migration and release of methane from fine-grained sediments. The mathematical and computational models will be constrained by and tested against comprehensive field and laboratory experiments that will characterize the rate, duration, and frequency of methane venting, bubble rise and dissolution of methane in the water column, the morphology and spacing of gas vent conduits in sediments, the distribution of gas in shallow sediments relative to its likely locus of production, and methane production metabolic pathways and rates in the sediments. Field data to inform the numerical models will be acquired from an area of known methane venting from fine-grained sediments in the central basin of Upper Mystic Lake, a dimictic kettle lake near Boston, Massachusetts.Methane is an important greenhouse gas, nominally 20 times more potent than carbon dioxide. There is currently a focused effort from the scientific community to better constrain methane fluxes and improve our understanding of the feedbacks between methane sources and climate change. In many settings, methane is released not directly to the atmosphere, but to bodies of water from underlying sediments where the methane is generated by biological activity, or transported from deeper sources of thermogenic origin. The mechanisms controlling methane venting from sediments are not well understood. In this project, we seek to advance current understanding of methane transport and release from fine-grained sediments. If successful, our findings will lay the groundwork for integrated modeling to constrain the global methane release from lakes, wetlands, estuaries and shallow continental margins.

甲烷是一种有效的温室气体，但其对地球气候的影响仍然很差，部分原因是全球甲烷通量不确定到大气中的不确定性。大气甲烷的一个重要来源是在地表水体内的有机富含沉积物中产生的甲烷，包括湖泊，湿地和海洋。从沉积物中释放出来的甲烷的比例绕过水柱中的溶解并到达大气中可能会对全球变暖产生重大贡献，并且这一比例严重取决于从基础沉积物的自由气体的模式和时空特征。理解甲烷消失的进步需要更好地理解沉积物中的水文过程，更好地理解参数和控制气体产生和积累的驱动力，气泡生长，导管的进化和持久性，排气间距，戒断速率，以及发射事件的频率，频率和持续时间。该项目的目的是开发甲烷生产，迁移和从细粒沉积物中释放的定量模型。数学和计算模型将受到限制和测试，并针对全面的现场和实验室实验，这些实验和实验室实验将表征水柱中甲烷通风量的速度，持续时间和频率，甲烷通风量的升高，气泡上升和甲烷的溶解，沉积物中气体导管的形态和间隔，在产量和甲基矿石的产量和甲基水平的浅色速度和甲基水位的分布相对于矿床和甲基矿石的生产速度分布。要告知数值模型的现场数据将从已知的甲烷排气区域中获取，该区域是从上部神秘湖中央盆地的高颗粒沉积物，这是马萨诸塞州波士顿附近的dimictic kettle湖中，甲烷是一种重要的温室气体，名义上是二氧化碳效率高的20倍。目前，科学界正在为更好地限制甲烷通量，并提高我们对甲烷源和气候变化之间的反馈的理解。在许多情况下，甲烷不是直接释放到大气中的，而是从生物活性产生甲烷或从更深层次的热源来源传输到的甲烷的基础沉积物中的水体。控制从沉积物排气的甲烷排气的机制尚不清楚。在这个项目中，我们试图提高人们对甲烷运输和从细粒沉积物中释放的理解。如果成功，我们的发现将为综合建模奠定基础，以限制湖泊，湿地，河口和浅色大陆边缘的全球甲烷释放。