Pockmark like structures in Lake Constance and their effects on methane emission from large lakes

博登湖麻点状结构及其对大型湖泊甲烷排放的影响

• 批准号: 36207447
• 负责人: Dr. Martin Wessels
• 金额: --
• 依托单位: Institut für Seenforschung
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2007
• 资助国家: 德国
• 起止时间: 2006-12-31 至 2009-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/36207447?language=en
• 关键词: Pockmark; like; structures; Lake; Constance

The role of lakes in the global methane budget seems to be more important than previously thought. However, the sources and the sinks of this climate active gas in large lakes are still quite unknown. Beside diffusive flux or ebullition due to high microbiological methane production, another potentially important methane source is the emission of fluids and gas from the deeper geosphere, such as methane seeps or pockmarks. Pockmarks are depressions at the sediment surface, often characterized by fluid flow and sites of enhanced methane release. Numerous pockmarks have been described for the marine environment, but pockmarks in limnic systems are rather unknown, as well as their associated geological, chemical and biological processes. In Lake Constance (southern Germany) pockmark like structures have been discovered recently. In a preliminary survey in 2005, we were able to observe methane ebullition and increased methane concentrations in the adjacent water column at these pockmarks. The objectives of this study are (1) to locate and to describe the pockmark areas in Lake Constance, (2) to identify the mechanisms responsible for the formation of pockmarks in Lake Constance, (3) to identify the sources of methane and (4) to quantify the fluxes of methane from the lake floor and their temporal variability.

湖泊在全球甲烷收支中的作用似乎比之前认为的更重要。然而，这种气候活动气体在大型湖泊中的来源和汇仍然相当未知。除了微生物甲烷产量高而产生的扩散通量或沸腾外，另一个潜在的重要甲烷来源是来自地圈更深的流体和气体的排放，如甲烷渗漏或麻点。麻点是沉积物表面的凹陷，通常以流体流动和甲烷释放增强为特征。海洋环境中有许多麻点被描述，但湖相系统中的麻点及其相关的地质、化学和生物过程相当鲜为人知。在康斯坦茨湖(德国南部)，最近发现了类似麻点的结构。在2005年的一次初步调查中，我们能够在这些麻点观察到甲烷沸腾和邻近水柱中甲烷浓度的增加。这项研究的目的是(1)定位和描述康斯坦茨湖的麻点区域，(2)确定康斯坦茨湖麻点形成的机制，(3)确定甲烷的来源，(4)量化湖底甲烷的通量及其时间变异性。