Efflux of methane (CH4) to the atmosphere from northern peatlands via ebullition: the role of plants and peat structure.

甲烷 (CH4) 通过沸腾从北部泥炭地流出到大气中：植物和泥炭结构的作用。

• 批准号: NE/F004958/1
• 负责人: Andrew Binley
• 金额: $ 22.14万
• 依托单位: Lancaster University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FF004958%2F1
• 关键词: Efflux; methane; CH4; atmosphere; northern

Large areas of the northern hemisphere's land mass are covered with peat soils. Peats form in waterlogged conditions. When peatland plants die and start to decay they form peat. Over many thousands of years, peat deposits have built up and may exceed 5-10 m in thickness. It is commonly thought that the decay of plant material cannot take place in waterlogged conditions. However, decay does occur below the water table and produces a gas called methane. Methane is an important greenhouse gas / that is, it contributes to the greenhouse effect / and northern peatlands are one of the largest global sources of this gas. Scientists are interested in predicting how much methane enters the atmosphere so that they are better able to predict climate change. As part of this effort, they have written computer models that simulate the production of methane in peat soils and the escape of this gas to the atmosphere. In the computer models it is assumed that methane can escape from peats to the atmosphere in three main ways: (i) by slow diffusion through the spaces between peat fibres, (ii) by diffusion and sometimes mass flow through vascular wetland plants like sedges, and (iii) as bubbles rising through the peat, a process called ebullition. A problem with applying these computer models is that we have very little understanding of how much methane escapes via bubbles and the factors involved in bubble loss, so it has not been possible to simulate accurately the process of ebullition. Some recent studies have shown that ebullition may be much more important than previously thought. Indeed, some researchers have suggested (i) that ebullition can account for more loss of methane to the atmosphere than the other two pathways combined (diffusion and plant-mediated transport) and (ii) that previous measurements of methane losses from northern peatlands are gross underestimates. However, that ebullition is the dominant pathway for transport of methane to the atmosphere in peatlands currently has the status of hypothesis and more work is urgently needed on characterising bubble build up and losses in northern peatlands. The purpose of our study is to gain a better understanding of both processes in one important class of peatland / bogs. We will take samples of peat (including the growing surface of the bog) back to the laboratory and keep them in state-of-the-art environmental cabinets where the light, temperature and humidity can be set to realistic values. We aim to answer three key research questions: 1. In bogs, how do the magnitude of the methane efflux and the relative importance of the mechanisms of that efflux (i.e. diffusion, plant-mediated, and ebullition) vary according to peat type? 2. How is bubble buildup and release affected by peat structure? 3. How does the presence of vascular plants, especially common types of sedge, affect bubble build up and loss from bog peats? Having the peat in the laboratory makes it possible to take sophisticated measurements of gas bubble dynamics that are not possible in the field. We will measure how gas bubbles accumulate in the peat during the onset of spring/summer conditions (when most methane is produced) and also how they are released from the peat. New technologies involving measuring the electrical properties of the peat will allow us to map where most bubbles form and how the volume of bubble accumulations changes in response to more methane being produced and the loss of bubbles to the surface of the peat. After the experiments, we will analyse the structure of the peat using an x-ray scanner. Using the x-rays we will be able to reconstruct the 'skeleton' of the peat and will be able to identify the plant remains that make up the peat, like stems of Sphagnum mosses and roots of sedges. With our knowledge of bubble build up in our samples, we will be able to identify which structures within the peat are most effective at trapping bubbles.

北半球土地的大面积覆盖着泥炭土。泥炭在水口条件下形成。当泥炭地植物死亡并开始腐烂时，它们会形成泥炭。在数千年的时间里，泥炭沉积已经建成，厚度可能超过5-10 m。人们普遍认为，植物材料的衰变不能在水口的条件下发生。但是，腐烂确实发生在地下水位下方，并产生一种称为甲烷的气体。甲烷是重要的温室气 /，即它有助于温室效应 /北部的泥炭地是该气体最大的全球来源之一。科学家有兴趣预测多少甲烷进入大气，以便他们能够更好地预测气候变化。作为这项工作的一部分，他们编写了计算机模型，该模型模拟了泥炭土壤中甲烷的产生，并将这种气体逃到大气中。在计算机模型中，假设甲烷可以通过三种主要方式从泥炭逃到大气中：（i）通过缓慢扩散穿过泥炭纤维之间的空间，（ii）通过扩散和有时通过血管湿地植物（如sedgus）等质量流动，（iii），（iii）作为气泡通过泥炭升起的过程，一种称为戒断的过程。应用这些计算机模型的一个问题是，我们对通过气泡和气泡损失所涉及的因素的逃逸数量很少，因此无法准确模拟戒断过程。最近的一些研究表明，戒烟可能比以前想象的重要得多。实际上，一些研究人员提出（i）（i）比其他两种途径（扩散和植物介导的运输）和（ii）先前对北泥炭北部的甲烷损失的测量值是严重的估计，这比其他两种途径（扩散和植物介导的运输）比其他两种途径更大。但是，这种戒烟是将甲烷运输到泥炭地的主要途径，目前具有假设的状态，并且在表征泡沫积聚和北部泥炭地的损失方面迫切需要更多的工作。我们研究的目的是在一类重要的泥炭地 /沼泽中更好地了解这两个过程。我们将将泥炭的样本（包括沼泽的生长表面）带回实验室，并将它们放在最先进的环境柜中，在这些环境柜中，可以将光，温度和湿度设置为逼真的值。我们的目的是回答三个关键的研究问题：1。在沼泽中，甲烷外排的大小以及该外排的机制的相对重要性（即扩散，植物介导和衰减）根据泥炭类型而有所不同？ 2。如何受到泥炭结构影响的气泡积聚和释放？ 3。血管植物的存在，尤其是常见的莎草类型，如何影响沼泽泥炭的气泡积聚和损失？在实验室中拥有泥炭使得可以对现场不可能的气泡动态进行复杂的测量。我们将在春季/夏季条件开始（生产大多数甲烷）以及如何从泥炭中释放出气泡在泥炭中的气泡在泥炭中积聚。涉及测量泥炭电气特性的新技术将使我们能够绘制大多数气泡形成的位置以及气泡积累的体积如何响应于产生更多的甲烷以及对泥炭表面的气泡损失。实验后，我们将使用X射线扫描仪分析泥炭的结构。使用X射线，我们将能够重建泥炭的“骨骼”，并能够识别构成泥炭的植物，例如泥炭苔藓的茎和Sedgen的根。随着我们对样品中气泡积聚的知识，我们将能够识别泥炭中哪些结构最有效地捕获气泡。

项目成果

Evaluating the effect of using artificial pore water on the quality of laboratory hydraulic conductivity measurements of peat

评估使用人工孔隙水对泥炭实验室水力传导率测量质量的影响

• DOI: 10.1002/hyp.7693
• 发表时间: 2010
• 期刊: Hydrological Processes
• 影响因子: 3.2
• 作者: Kettridge N

The effect of peat structure on the spatial distribution of biogenic gases within bogs

• DOI: 10.1002/hyp.10056
• 发表时间: 2014-10
• 期刊: Hydrological Processes
• 影响因子: 3.2
• 作者: X. Comas;N. Kettridge;A. Binley;L. Slater;A. Parsekian;A. J. Baird;M. Strack;J. Waddington

Efficient multi-scale imaging of subsurface resistivity with uncertainty quantification using ensemble Kalman inversion

使用集合卡尔曼反演对地下电阻率进行不确定性量化的高效多尺度成像

• DOI: 10.5194/egusphere-egu21-16358
• 发表时间: 2021
• 作者: Binley A