Quantifying Event-Driven Methane Fluxes from Northern Peatlands Using A Novel Automated Flux Chamber Technique

使用新型自动通量室技术量化北部泥炭地事件驱动的甲烷通量

基本信息

批准号：
NE/H01182X/1
负责人：
Yit Arn Teh
金额：
$ 8.31万
依托单位：
University of St Andrews
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FH01182X%2F1
关键词：
Quantifying Event Driven Methane Fluxes

项目摘要

Peatlands are the largest natural sources of the greenhouse gas methane (CH4), and understanding the potential contributions of peatlands to atmospheric CH4 budgets is crucial for understanding current and future climate change. Methane in peatlands is produced as a by-product of organic matter decomposition by anaerobic microorganisms called 'methanogens.' These organisms typically inhabit deeper, more saturated peat layers that receive little or no O2 input from the atmosphere. Methane is also destroyed by a group of soil microorganisms called 'methanotrophs,' which require O2 to breakdown CH4 to CO2. These organisms typically inhabit the upper peat horizons (0-10 cm) near the soil-atmosphere interface, where O2 exchanges more freely with the substrate below. Peatland net CH4 emissions are thus influenced by the relative balance of CH4 production by methanogens and CH4 breakdown by methanotrophs. One of the key unanswered questions in peatland CH4 cycling is the extent to which weather events influence CH4 emissions to the atmosphere. Weather events trigger changes in key environmental variables, such as atmospheric pressure, rainfall, soil moisture, and soil oxygen (O2) status, all of which play a role in regulating net CH4 emissions. Atmospheric pressure can strongly influence the amount of CH4 released from peat in bubble form, a process referred to as 'ebullition.' CH4 is a hydrophobic gas that tends to accumulate in peat as bubbles, rather than dissolving into soil pore waters. Sudden drops in atmospheric pressure caused by the passage of cyclonic weather systems can trigger bubble release because reductions in atmospheric pressure stimulates CH4 to de-gas from soil pore waters. In addition, reductions in atmospheric pressure result in the formation of bubbles with larger relative volumes, in accordance with the Ideal Gas Law, which may further enhance ebullition. Rainfall events also play a role in regulating CH4 emissions because inundation of upper soil horizons (0-10 cm) often reduces soil O2 concentrations, suppressing the activity of methanotrophs. Lowered rates of CH4 breakdown by methanotrophs means that more CH4 is emitted to the atmosphere, rather than being converted to CO2. It is likely that we are significantly underestimating peatland CH4 emissions by failing to adequately quantify or characterise the effects of atmospheric pressure and rainfall events. For example, studies of CH4 ebullition suggest that as much as 50-60 % of total peatland CH4 emissions can arise from bubbling (as opposed to diffusion or transport through aerenchymatic plants), with most of those emissions occurring because of reductions in atmospheric pressure. Likewise, rainfall events can cause dramatic increases in CH4 emissions, with areas that would otherwise destroy atmospheric CH4 becoming transient CH4 sources. The reason that we know so little about the effects of weather events on CH4 emissions is that these phenomena are transient and episodic, making them difficult to study using conventional measurement techniques. Because of the unpredictable and transient nature of weather events, the only suitable means of studying them is to collect continuous measurements of CH4 flux over time. However, it is financially and logistically difficult to collect continuous measurements of CH4 emissions using conventional sampling methodologies because these approaches are time and labour intensive. To address this problem, we have developed a novel automated flux chamber technique capable of measuring CH4 emissions quasi-continuously, with minimal user intervention and demand for consumables. We propose to use this novel system to quantify the effects of atmospheric pressure and rainfall events on peatland CH4 emissions, thus improving our overall understanding of the processes governing CH4 flux to the atmosphere.

泥炭地是温室气甲烷（CH4）的最大自然来源，了解泥炭地对大气CH4预算的潜在贡献对于理解当前和未来的气候变化至关重要。泥炭地中的甲烷作为有机物分解的副产品，被称为“甲烷剂”的厌氧微生物分解。这些生物通常居住在更深，更饱和的泥炭层中，几乎没有从大气中获得O2输入。甲烷还被称为“甲烷营养”的一组土壤微生物破坏，这些生物需要O2将CH4分解为CO2。这些生物通常居住在土壤 - 大气界面附近的上泥炭地平线（0-10厘米）中，其中O2与以下基材更加自由地交换。因此，泥炭净CH4排放受甲烷剂CH4产生的相对平衡和甲烷营养分解的相对平衡的影响。 Peatland CH4骑行中的主要未解决问题之一是天气事件在多大程度上影响CH4对大气的排放。天气事件引发了关键环境变量的变化，例如大气压力，降雨，土壤水分和土壤氧（O2）状态，所有这些状态都在调节净CH4排放量中发挥作用。大气压力可以强烈影响以气泡形式从泥炭释放的CH4量，这一过程称为“戒断”。 CH4是一种疏水气体，倾向于在泥炭中积聚为气泡，而不是溶解在土壤孔隙水中。由于气候天气系统的通过而引起的大气压力突然下降会触发气泡释放，因为大气压力的降低会刺激CH4从土壤孔隙水中刺激到加气。此外，根据理想气体定律，大气压的降低会导致相对体积较大的气泡形成，这可能会进一步增强戒烟。降雨事件在调节CH4排放方面也起作用，因为上层土壤层（0-10 cm）通常会降低土壤O2浓度，从而抑制甲烷营养的活性。甲烷营养的CH4分解率降低意味着更多的CH4发射到大气中，而不是转化为CO2。由于无法充分量化或表征大气压力和降雨事件的影响，我们可能会大大低估泥炭兰CH4的排放。例如，对CH4戒断的研究表明，多达50-60％的泥炭兰CH4排放量可能是由于冒泡（而不是通过气泡植物的扩散或运输）引起的，大多数这些排放会由于大气压力减少而发生。同样，降雨事件可能会导致CH4排放量的急剧增加，否则将破坏大气CH4成为瞬态CH4源的区域。我们对天气事件对CH4排放的影响很少的原因是，这些现象是短暂的和偶发的，因此使用常规测量技术很难研究。由于天气事件的不可预测和瞬时性质，研究它们的唯一合适方法是随着时间的推移收集CH4通量的连续测量。但是，在财务和逻辑上很难使用常规抽样方法来对CH4排放进行连续测量，因为这些方法是时间和劳动力密集的。为了解决这个问题，我们开发了一种新型的自动化通量室技术，能够以最小的用户干预和对消耗品的需求来测量CH4排放量。我们建议使用这种新型系统来量化大气压力和降雨事件对Peatland CH4排放的影响，从而提高我们对控制CH4通量到大气的过程的整体理解。