Development of an oceanic in situ carbon dioxide sensor for high spatial and temporal resolution measurements

我们建议开发和试验一种新型的基于荧光寿命的海洋大气和海洋表面二氧化碳（CO2）浓度传感技术。这项技术有望在气候研究的科学能力方面迈出重要一步，与基于荧光寿命指示器的强大而精确的氧气传感器的出现所带来的成就类似，如果不是更大的话。二氧化碳是全球变暖和海洋酸化的主要媒介。自工业革命以来，全球约30%的人为二氧化碳排放已被海洋吸收。海洋作为汇的持续能力对大气中二氧化碳、气候和海洋酸化的未来趋势至关重要。至关重要的是，来自海气界面上方和下方的地表区域的二氧化碳数据对通量研究具有科学意义。这些研究使我们能够估计目前大气和海洋之间二氧化碳的转移速率。有证据表明，大气-海洋CO2通量背后的驱动力正在减弱，这是大气CO2浓度年增长率加速的部分原因。该博士项目的总体目标是开发下一代海洋原位pCO2传感器，该传感器将利用荧光寿命技术，使用先进的双寿命参考指标和采用高频光子计数和荧光衰减曲线拟合的光学询问技术。该传感器将利用CO2的酸性特性来确定市售（Presens GmbH）指示剂材料内的CO2依赖的pH值变化。传感器由pH敏感荧光指示剂、CO2敏感缓冲液、CO2不敏感参考指示剂和支持气体透性（但离子不透性）膜基质组成。博士项目的目标是1)优化荧光探测方法，2)确定传感器的精度/准确性，3)确定传感器的温度和盐度依赖性，4)开发温度补偿算法，5)将传感器封装在小型化外壳中，6)在沿海/海洋航行中试验二氧化碳传感器。这项研究将为英国在海洋传感器开发、大气-海洋二氧化碳交换、海洋酸化、海洋生物地球化学等方面的研究做出重要贡献，并将加强我们在气候变化研究方面的国际地位。博士生将利用NOCS建立的海洋微系统技术实验室和英国海洋酸化碳酸盐化学设施（使用NERC和EPSRC资本资助建立），因此将在优秀的分析设施中工作。该博士生将接受分析化学、传感器开发、碳酸盐化学和海洋生物地球化学方面的优秀实践培训，并将学习相应的分析化学和海洋生物地球化学课程。南安普顿国家海洋学中心的海洋微系统中心（NOCS）将来自南安普顿大学的技能和科学资源与NOCS自然环境研究委员会传感器部门相结合，提供一个国际知名的研究小组，致力于海洋传感器技术的前沿[见www.soton.ac.uk/rmst]]。这个庞大的团队的兴趣从微流体和微机械专业知识延伸到生物污垢的研究，为在拟议领域培养研究生提供了良好的环境。该小组的几个海洋原位传感器已经达到了4-6级的技术准备水平，并且通过PI Achterberg为拟议的项目提供了额外的化学分析和生物地球化学技能。除了关键技能培训外，研究团队还将促进NERC资助的博士研究生开发的领先技术，以回答关键的环境问题。

We propose to develop and trial a novel high performance fluorescence lifetime based technology for sensing of carbon dioxide (CO2) concentrations in the marine atmosphere and surface ocean. The technology promises a significant step in scientific capability in climate research, similar if not greater than that enabled by the advent of robust and accurate oxygen sensors based on fluorescence lifetime indicators. CO2 is the main vector for global warming and ocean acidification. Since the industrial revolution, ca. 30% of the global anthropogenic CO2 emissions have been taken up by the oceans. The continued ability of the oceans to act as a sink is of critical importance for future trends in atmospheric CO2, climate and ocean acidification. Crucially, CO2 data from the surface zone immediately above and below the air-sea interface, is of scientific interest for flux studies. Such studies enable estimation of current transfer rates of CO2 between the atmosphere and the oceans. There is evidence that the driving force behind the air-sea flux of CO2 is decreasing and that this is partly responsible for the acceleration of atmospheric CO2 concentration annual growth rate. The overall aim of this PhD project is to develop the next generation of marine in situ pCO2 sensors that will utilise fluorescence life-time technology, using advanced dual lifetime referenced indicators and optical interrogation techniques employing high frequency photon counting and fluorescence decay curve fitting. The sensor will use the acidic character of CO2 to determine CO2-dependent change of pH inside a commercially available (Presens GmbH) indicator material. The sensors are built from a pH sensitive fluorescence indicator, a CO2 sensitive buffer, a CO2 insensitive reference indicator and a supporting gas-permeable (but ion impermeable) membrane matrix. The objectives of the PhD project are to 1) optimise the fluorescence interrogation approach, 2) determine precision/accuracy of sensor, 3) determine temperature and salinity dependency of sensor, 4) develop temperature compensation algorithm, 5) package sensor in miniaturised housing, 6) trial the CO2 sensor on coastal/oceanic voyages. This study will provide an important contribution to UK research on marine sensor development, air-sea exchange of CO2, ocean acidification, marine biogeochemistry, and the proposed research will strengthen our international position in climate change research. The PhD student will utilise the established laboratories for Marine Microsystem technology at NOCS and the UK Ocean Acidification Carbonate Chemistry Facilities (set-up using NERC and EPSRC Capital Grants), and therefore will work in excellent analytical facilities. The PhD student will receive an excellent hands-on training in analytical chemistry, sensor development, carbonate chemistry and marine biogeochemistry, and will undertake appropriate courses in analytical chemistry and marine biogeochemistry. The Centre for Marine Microsystems at the National Oceanography Centre, Southampton [NOCS] combines skills and scientific resources from across the University of Southampton with the Natural Environment Research Council sensor section at NOCS to provide an internationally known research group working at the leading edge of marine sensor technology [see www.soton.ac.uk/rmst]. This large group with interests extending from micro fluidics and micromechanical expertise to studies on biofouling, provides an excellent environment for the training of a research student in the proposed area. Several marine in situ sensors from the group are already at technology readiness levels 4-6, and additional chemical analytical and biogeochemical skills are provided through the PI Achterberg for the proposed project. The research team will facilitate NERC funded leading technology to be developed by the PhD student to answer crucial environmental questions, in addition to key skills training.