Developing a Reagentless In situ Sensor for Measurements of Dissolved Inorganic Carbon in Seawater

海水碳酸盐体系是全球碳循环的重要组成部分，主要由溶解二氧化碳(CO2)、碳酸氢盐(HCO3-)和碳酸盐离子(CO32-)组成。它调节海水的酸度和海洋与大气之间二氧化碳交换的方向和大小，从而控制海洋酸化和气候变化。开发有效测量碳酸盐体系参数的传感器技术已被广泛认为是海洋科学界的优先事项。溶解无机碳(DIC)是海水中溶解的CO2、HCO3-和CO32-的总和，是研究一系列与海洋碳循环和海洋有机碳对海洋生物和生态系统影响有关的重要研究问题的关键变量。在过去的十年中，各种原位DIC传感器的原型不断涌现。然而，这些系统需要化学试剂，因此复杂，功率要求高，部署持续时间和可使用的观测平台有限。为了解决这些局限性，本项目的目标是开发一种新的无试剂原位DIC传感器，用于海水应用，使用固态传感技术和无试剂化学反应。新的DIC传感器将在海洋研究领域具有广泛的适用性。美国国家海洋和大气局东北水产科学中心表示，如果开发成功，他们有兴趣获得新的DIC传感器，以便在其沿海调查中常规部署，以加强海洋生态系统监测，并改进对海洋海洋生态系统健康和渔业物种影响的现场研究。这一进展可能会为海洋研究界呼吁在滑翔机和浮标上长期部署急需的DIC传感器铺平道路。通过与瓦科伊特湾国家河口研究保护区的合作，将招募一名社区大学生和一名当地公民科学家进行传感器测试。他们的反馈将帮助非专家改进传感器的操作和整体性能。这一民主化战略将扩大未来的部署和应用，超越学术界，并向利益攸关方提供数据。该项目将通过麻省理工学院和伍兹霍尔海洋研究所(WHOI)的联合教育项目支持一名博士生。它将通过WHOI暑期学生奖学金计划和伍兹霍尔伙伴教育计划培训一名社区大学生和两名本科生暑期实习生。该项目将通过招收所有学生来支持多样性、公平性和包容性。研制和地面验证第一个无试剂原位DIC传感器构成了这项工作的智力价值的核心。新的DIC方法将基于受控的电酸化过程来酸化海水样品，然后进行光学二氧化碳检测。这种方法不使用任何化学试剂。开发的主要目标包括：(1)在实验室中开发和优化新的DIC方法，以实现高质量的海水DIC测量；(2)将新的DIC方法应用于能够在浅海系统中原位测量DIC的低功率原型传感器系统；(3)在海水水箱中测试和校准新的传感器系统，并评估其特点、性能和长期稳定性；(4)在马萨诸塞州瓦科伊特湾的一个时间序列站测试部署新传感器以及一套其他物理和生物地球化学传感器，以延长时间段，以评估传感器的现场性能和稳定性。这项新技术将是一次重大的技术飞跃，通过显著提高稳健性、功耗和部署持续时间，同时降低成本、复杂性和尺寸，解决当前原位DIC传感的关键挑战。因此，它有可能适用于许多固定和移动的观测平台，例如快速增长的水面车辆、滑翔机和生物地球化学浮标的舰队。该项目将显著提高我们研究和应对海洋碳循环和海洋酸化的能力。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。

The seawater carbonate system, mainly consisting of dissolved carbon dioxide (CO2), bicarbonate (HCO3-) and carbonate ions (CO3 2-), is an important part of the global carbon cycle. It regulates seawater acidity and the direction and magnitude of CO2 exchange between the ocean and the atmosphere, thus exerting control on ocean acidification (OA) and the changing climate. Development of sensor technologies to measure the carbonate system parameters efficiently has been widely recognized as a priority in the ocean science community. Dissolved inorganic carbon (DIC), the sum of dissolved CO2, HCO3 - and CO3 2- in seawater, is a master variable that is critical to study a suite of important research questions related to the marine carbon cycle and OA’s impacts on marine biology and ecosystems. Various prototype in situ DIC sensors have emerged in the past decade. However, these systems require chemical reagents, and are thus complex, have high power requirements, and are limited in deployment duration and observing platforms that can be used. To address these limitations, the goal of this project is to develop a new reagentless in situ DIC sensor for seawater applications using a solid-state sensing technology and reagentless chemical reactions. The new DIC sensor will have broad applicability to the ocean research community. NOAA Northeast Fisheries Science Center have expressed their interest, if development is successful, to acquire the new DIC sensor to be routinely deployed on their coastal surveys to enhance OA monitoring and improve in situ studies of the effects of OA on ecosystem health and fishery species. This development may pave the road for much-needed long-term deployments of DIC sensors on gliders and floats that the ocean research community is calling for. One community college student and one local citizen scientist will be recruited for sensor testing through collaboration with Waquoit Bay National Estuarine Research Reserve. Their feedback will help improve the sensor’s operation by non-experts and its overall performance. This democratized strategy will widen future deployments and applications beyond academia and provide data to stakeholders. This project will support one PhD student through the joint education program between Massachusetts Institute of Technology and Woods Hole Oceanographic Institution (WHOI). It will train one community college student and two undergraduate summer interns through the WHOI Summer Student Fellowship program and the Woods Hole Partnership Educational Program. This project will support diversity, equity, and inclusion through the recruitment of all students. Developing and ground truthing the first-of-its-kind reagentless in situ DIC sensor constitutes the core of the intellectual merit of this work. The new DIC method will be based on a controlled electro-acidification process to acidify seawater samples followed by optical pCO2 detection. No chemical reagents will be used in this method. The main objectives of the development include: (1) Develop and optimize the new DIC method in the laboratory to achieve high-quality measurements of DIC in seawater; (2) Adapt the new DIC method into a low-power, prototype sensor system capable of in situ DIC measurements in shallow coastal systems; (3) Test and calibrate the new sensor system in seawater tanks and evaluate its characteristics, performance and long-term stability; (4) Test-deploy the new sensor, along with a suite of other physical and biogeochemical sensors, at a time-series station at Waquoit Bay, MA for extended periods to evaluate the sensor’s in situ performance and stability. The new technology will be a significant technological leap forward, resolving key challenges in current in situ DIC sensing by significantly improving robustness, power consumption, and deployment duration, while reducing cost, complexity, and size. It thus has the potential to be adapted for many stationary and mobile observing platforms, such as the rapidly growing fleet of surface vehicles, gliders, and biogeochemical floats. This project will significantly improve our capability to study and respond to the marine carbon cycle and ocean acidification.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.