A Robust and Sensitive In Situ Analyzer for Simultaneous Methane Carbon and Hydrogen Isotopic Measurements in the Deep Sea

尽管经过了几十年的研究，但由于在深海巨大压力下测量溶解气体的困难，对海洋甲烷循环的研究一直受到阻碍。通过开发能够连续测量甲烷浓度和同位素的新传感器，该项目旨在更好地了解深海的甲烷循环和甲烷来源，从而补充对这种温室气体的全球动态的理解。最近，基于量子级联激光(QCL)的传感器在严格的环境限制下，在坚固、高精度和异常灵敏的化学和同位素测量方面表现出了令人印象深刻的记录。该项目将基于QCL的传感器与透气膜入口相结合，将开发和部署用于深海生物地球化学的原位甲烷同位素传感器。该传感器将在与海洋探索信托基金合作的研究巡航上进行现场测试，利用具有远程临场感的勘探船(E/V)鹦鹉螺号和远程操作运载器(ROV)Hercules，促进教育人员、学生和公众同时参与海洋工程、技术、化学、探索和科学。为了设计先进的仪器来研究深海甲烷(CH4)的来源和生物地球化学循环，研究人员将开发一种基于量子级联激光的原位甲烷同位素传感器。通过将基于离轴集成腔输出光谱的方法与量子级联激光器相结合，该传感器将能够原位测量甲烷同位素。该项目的一个主要目标是演示使用基于量子级联激光的仪器进行深海化学传感。将实施新设计的进气系统，以减少水的干扰，并提高现场稳定同位素分析的灵敏度。传感器系统将在深海甲烷丰富的环境中使用E/V Nautilus和ROV Hercules进行现场测试。

Despite decades of research, study of the marine methane cycle has been hindered by the difficulties of measuring dissolved gases at the tremendous pressure of the deep ocean. Through development of new sensors capable of continuous methane concentration and isotope measurements, this project aims to provide a better understanding of methane cycling and methane sources in the deep sea and thereby complements the understanding of global dynamics of this greenhouse gas. Recently, Quantum cascade laser-based (QCL) sensors have demonstrated an impressive track record for robust, highly precise and exceptionally sensitive chemical and isotopic measurements under demanding environmental constraints. Coupling a QCL-based sensor with a gas-permeable membrane inlet, this project will develop and deploy an in situ methane isotope sensor for deep ocean biogeochemistry. The sensor will be field-tested on a research cruise in collaboration with the Ocean Exploration Trust utilizing the telepresence-enabled Exploration Vessel (E/V) Nautilus and the remotely operated vehicle (ROV) Hercules, facilitating the simultaneous engagement of educators, students, and the general public in ocean engineering, technology, chemistry, exploration, and science. In an effort to design advanced instrumentation for studying sources and biogeochemical cycling of methane (CH4) in the deep ocean, the investigators will develop a Quantum cascade laser-based in situ methane isotope sensor. By combining an off-axis integrated cavity output spectroscopy-based approach with Quantum cascade lasers, this sensor will be capable of measuring in situ methane isotopes. A primary goal of this project is to demonstrate the use of Quantum cascade laser-based instrumentation for deep sea chemical sensing. A newly designed gas inlet system will be implemented to reduce interference by water and to enhance the sensitivity of in situ stable isotopic analyses. The sensor system will be field tested at a deep-sea methane-rich environment using the E/V Nautilus and the ROV Hercules.