Doctoral Dissertation Research: Magnitude and Spatial-Temporal Variability of Methane Sinks in a Seasonally Stratified, Eutrophic Northern Temperate Lake

甲烷是一种重要的温室气体，其大气浓度目前以每年约1%的速度上升。甲烷也是地球水体中碳循环的重要组成部分。这个博士论文研究项目的目标是测量甲烷在大气中流失的量、速率和空间分布，而不是在淡水湖中被微生物氧化而流失的量。由于生产、排放和消费的不均匀性和瞬态性，对天然水体中的甲烷过程进行量化是困难的。在这个项目中要测试的一个假设是冒泡——一个空间和时间上的异质性过程——是甲烷从湖底释放到大气中的主要模式。博士候选人将使用现代传感器技术获得甲烷鼓泡的连续测量。定制的锥形室将用于捕获气泡，并将部署在湖中的各个位置。这些腔室将配备压力传感器和红外传感器，以连续测量收集的气体体积和气泡中存在的甲烷的平均浓度。将开发软件来分析数据，以检测和记录主要的沸腾事件。此外，水样将通过注射器采样装置收集，样品中的甲烷将使用气相色谱法分析。这些样本还将通过孵化实验，用于测试不同湖泊深度的甲烷氧化程度。为了提供上述测量的背景，辅助数据，如水质参数（如水温、溶解氧）、大气条件（如气温、气压）和主要离子（如硫酸盐、硝酸盐）也将被收集。该项目的主要油田位于马萨诸塞州沃本富含甲烷的上神秘湖。向大气释放甲烷不仅影响地球的辐射收支；它还代表了碳的损失，减少了水生生态系统的能量和能量。由于以前的甲烷研究中使用的测量技术缺乏连续性，目前从水体，特别是淡水湖排放的甲烷量被认为被大大低估了。这项研究的结果将有助于弥合全球变暖中甲烷驱动成分的现有差距。这些知识对于制定减缓气候变化的公共政策至关重要，这些政策应适当地优先考虑管理工作。因为湖泊中的甲烷可能是当地有用的替代燃料来源；加强对甲烷过程的理解将有助于确定收集这种燃料作为周边地区良性能源的可行性。作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立研究生涯。

Methane is an important greenhouse gas whose atmospheric concentration is currently rising by about 1 percent every year. Methane also is an important component of the carbon cycle in the earth's water bodies. The goal of this doctoral dissertation research project is to measure the magnitude, rate, and spatial distribution of methane that is lost to the atmosphere as opposed to that lost to oxidation by micoorganisms in a freshwater lake. Quantifying methane processes in natural waters is difficult because of the patchy and transient nature of production, emission, and consumption. One hypothesis to be tested during this project is that bubbling -- a spatially and temporally heterogenous process -- is the major mode of methane release to the atmosphere from the bottom of the lake. The doctoral candidate will use modern sensor technology to obtain continuous measurements of methane bubbling. Custom-made conical chambers will be used to capture the bubbles and will be deployed at various locations in the lake. The chambers will be equipped with pressure sensors and infra-red based sensors to continuously measure the volume of gas that is collected and the average concentration of methane present in the bubbles. Software will be developed to analyze the data to detect and record major ebullition events. In addition, water samples will be collected via a syringe-based sampling device, and the methane present in the samples will be analyzed using gas chromatography. The samples also will be used to test the extent of methane oxidation at various lake depths through incubation experiments. In order to provide a context for the above measurements, ancillary data such as water quality parameters (e.g. water temperature, dissolved oxygen), atmospheric conditions (e.g. air temperature, air pressure) and major ions (e.g. sulfate, nitrate) will also be collected. The primary field site for this project is the methane-rich Upper Mystic Lake in Woburn, Massachusetts.The release of methane to the atmosphere not only affects the planetary radiation budget; it also represents a loss of carbon, reducing power, and energy from aquatic ecosystems. The amount of methane currently emitted from water bodies, and freshwater lakes in particular, is thought to be greatly underestimated due to the lack of continuity in measurement techniques used in prior methane studies. The results of this research will help bridge existing gaps in the methane-driven component of global warming. Such knowledge is essential in formulating public policies on climate change mitigation that appropriately prioritize management efforts. Because methane in lakes could represent a locally useful alternate source of fuel; an enhanced comprehension of methane processes would help determine the feasibility of harvesting this fuel as a benign source of power for surrounding areas. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.