Underwater coded aperture miniature mass spectrometer (UW-CAMMS)

对海洋中溶解气体时空分布的测量提供了与全球气候、板块构造、水文环流模式、油污羽流跟踪和监测等各种科学问题有关的基本信息。测量海洋中溶解的甲烷特别重要，因为甲烷作为温室气体的效力是二氧化碳的84倍。随着全球变暖导致的海洋温度上升，海底的大型天然气水合物储藏库可能会向水柱中释放更多甲烷。目前，尚不清楚天然气水合物释放了多少甲烷(更不用说甲烷是否在增加了)，也不清楚有多少甲烷在到达海洋表面之前被氧化，在那里它可以释放到大气中。海洋表面以下甲烷的氧化可能导致海洋酸化，从而影响海洋生物，而释放到大气中可能会改变气候。因此，评估海洋表面以下和海洋表面混合层中甲烷的相对浓度对于我们理解天然气水合物可能如何影响海洋生态系统和对全球气候的反馈具有重要的意义。现场测量是非常可取的，因为基于实验室的测量降低了时空分辨率，增加了测量的时间和成本。在过去的20年里，由于水下膜进样质谱仪能够以高灵敏度(1 Ppb)和快速响应时间测量各种气体的浓度，因此已成为海洋中溶解气体的现场分析的主要方法。然而，目前可用的大多数水下质谱计由于质量范围、分辨率和/或水蒸气的干扰而不能很好地测量溶解的甲烷。该项目将作为一个平台，通过为高中生、本科生、研究生和博士后研究人员提供研究机会，加强跨学术水平和学科的教育，并将被用来扩大未被充分代表的群体，特别是妇女和未被代表的少数民族的参与。这项研究将开发一种水下编码孔径微型质谱仪(UW-CAMMS)，使用摆线质谱仪、空间孔径编码和焦平面阵列探测器，与目前用于现场测量海洋中溶解气体的最先进水下质谱仪相比，将提高灵敏度、分辨率和功率要求。较高的分辨率将消除甲烷测量中水蒸气的干扰问题。UW-CAMMS中的空间孔径编码将在不牺牲分辨率的情况下通过增加离子吞吐量来提高灵敏度，而UW-CAMMS中的离子阵列探测器将能够在大质量范围内实现高灵敏度和动态范围的同时检测。一旦开发完成，UW-CAMMS将被部署在R/V Searwater上进行实地测试，并研究北卡罗来纳州和南卡罗来纳州海岸外Blake Ridge上方水域的甲烷剖面。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Measurements of the spatiotemporal distribution of dissolved gases in the ocean provides essential information relating to a wide variety of scientific questions of relevance to global climate, plate tectonics, hydrologic circulation patterns, and oil spill plume tracking and monitoring, to name a few. Measurements of dissolved methane in the ocean are of particular importance in that methane is 84 times more potent as a greenhouse gas than carbon dioxide. With increasing ocean temperatures associated with global warming, large gas hydrate reservoirs on the ocean floor could potentially release more methane into the water column. Currently, it is not clear how much methane is being released by gas hydrates (let alone if it is increasing), and how much of it is being oxidized before reaching the ocean surface where it can be released into the atmosphere. Oxidation of the methane below the ocean surface may lead to ocean acidification, thereby impacting marine organisms, while release to the atmosphere could alter climate. Hence, assessment of the relative concentrations of methane below the ocean surface and in the ocean surface mixed-layer has important ramifications for our understanding of how gas hydrates may impact marine ecosystems and the feedbacks to our global climate. in situ measurements are highly desirable as laboratory-based measurements reduce the spatiotemporal resolution and increase time and cost of measurements. Over the past 20 years, underwater membrane inlet mass spectrometry has emerged as the primary method for in situ analysis of dissolved gases in the ocean due to their ability to measure the concentrations of a wide variety of gases with high sensitivity (1 ppb) and rapid response times. However most currently available underwater mass spectrometers are not ideal for measurements of dissolved methane due to limited mass range, resolution, and/or interference from water vapor. This project will be used as a platform for enhancing education across multiple academic levels and disciplines by providing research opportunities for high-school students, undergraduates, graduate students, and post-doctoral researchers and will be leveraged towards broadening the participation of underrepresented groups, particularly women and underrepresented minorities.This research will develop an underwater coded aperture miniature mass spectrometer (UW-CAMMS) using a cycloidal mass analyzer, spatial aperture coding, and a focal plane array detector that combined will improve sensitivity, resolution, and power requirements compared to the current state of the art underwater mass spectrometers used for in situ measurements of dissolved gases in the ocean. The higher resolution will eliminate the issue of interference from water vapor in measurements of methane. The spatial aperture coding in UW-CAMMS will increase sensitivity by increasing ion throughput without sacrificing resolution and the ion array detector in UW-CAMMS will enable simultaneous detection over a wide mass range with high sensitivity and dynamic range. Once developed, UW-CAMMS will be deployed on the R/V Shearwater for field testing and to study methane profiles in the waters above Blake Ridge off the coast of North and South Carolina.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.