SCUID: A Carbon Nanotube Based Sensor for Measurement of Dissolved Gases in Water

本研究旨在开发一个原位海洋传感器平台，该平台能够测量海洋中感兴趣的溶解气体，以研究氧气最小带的氮循环。这种类型的传感器到目前为止还不存在，它是通过结合两个成熟的系统来实现的，一个是尖端技术的传感平台，一个是经过验证的潜水外壳。基于碳纳米管的气体传感器被认为是尖端技术，允许在相关灵敏度下检测广泛的环境和安全相关微量气体。它们是低功耗的，并且在空间中提供原位，实时，自动测量化学物质，用于火灾探测，燃料泄漏检测和健康监测系统。由于这些气体传感器的多功能性、灵敏度和测量范围，世界各地的公司都在寻求集成这些气体传感器。近年来，为了应对高需求，大量制造这些传感器的初创企业已经形成。虽然目前可以测量大气中的微量气体，如N2O、NO和DMS，但用于实时和原位测量海水中溶解气体的传感器仅限于CO2、CH4和H2S。已知这些与气候相关的气体中有几种是在低氧条件下产生的，例如公海中的氧气最低区和“死区”。在沿海海域。今天，像N2O和NO这样的溶解气体的高精度测量依赖于基于实验室的分析，如质谱法和气相色谱法。全球变暖是观测到的开放海洋氧最小带扩大的工作假设；增加的分层减少了上层海洋的通风和通气性。沿海地区缺氧的扩大与河流径流中过量营养物质的富营养化有关，这些营养物质来自施用于农场、田地和草坪的化肥等来源。海洋生物在缺氧条件下会受到高度压力，并可能产生巨大的生态影响，包括鱼类和贝类的大量死亡以及有害藻类的大量繁殖。由于幼鱼比成熟鱼更容易受到影响，因此也会产生更持久的影响，从而产生不利的后续影响，例如经济损失。迫切需要更深入地了解缺氧区的气体循环。测量与气候相关的微量气体对于量化海洋源和汇以及了解它们对全球气候变化的影响是必要的。海洋学界需要一种新的、小型的、低功耗的、实时的溶解气体传感器，它可以调谐到不同的感兴趣的气体，以便对感兴趣的特定气体进行高空间分辨率的采样。独立于平台的传感器可用于浮子、滑翔机、电导率-温度-深度传感器，以及用于开放水域和沿海溶解气体调查的自动水下航行器。这不仅将扩大传感器可以在现场检测到的溶解气体，而且还将加强在海洋空气交换、温室气体和热液喷口等领域的科学发现、数据和模型。传感芯片由单壁碳纳米管气体传感器组成。它由美国宇航局艾姆斯研究中心提供，迄今已被用于探测太空和地球上的几种气体。在这项研究中，传感芯片被训练来检测N2O和NO，这两种气体是海洋学界非常感兴趣的，但迄今为止还不可能在现场检测到。适用于海的潜水舱（至2000米）将由该领域的专家Pro-Oceanus提供。N2O和NO的目标检出限分别为100ppb和5ppb。气体传感器和集成传感系统的实验室测试将在APL/UW进行。胡德运河（西澳）和墨西哥湾的现场试验计划在本提案的第三年进行。如果成功，这些测试将产生N2O和NO气体浓度的无与伦比的空间分辨率，并使我们能够得出迄今为止不可能得出的关于海气相互作用的结论。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This research aims at developing an in-situ oceanographic sensor platform that enables the measurement of dissolved gases of interest in the ocean in order to study the nitrogen cycle in oxygen minimum zones. This type of sensor does not exist to date and is accomplished by marrying two mature systems - a cutting edge technology sensing platform, and a proven submergible housing. Carbon nanotube-based gas sensors are considered cutting edge technology, allowing to detect a wide range of environmental and safety related trace gases at relevant sensitivities. They are low power, and have provided in-situ, real time, automated measurement of chemicals in space, for fire detection, for fuel leak detection, and as health monitoring system. Companies around the world are looking to integrate these gas sensors due to their versatility, sensitivity, and range of measurement. In recent years, start-ups manufacturing these sensors in large numbers have formed in response to the high demand. While it is possible today to measure trace gases such as N2O, NO, and DMS in the atmosphere, the sensors to measure dissolved gases in seawater real time and in situ are limited to only CO2, CH4, and H2S. Several of these climatically relevant gases are known to be produced under low oxygen conditions, such as the oxygen minimum zones in the open ocean, and ?deadzones? in the coastal ocean. Today highly precise measurement of dissolved gases like N2O and NO rely on laboratory-based analyses such as mass spectrometry and gas chromatography. Global warming is the working hypothesis for the observed expansion of open ocean Oxygen Minimum Zones; increased stratification reduces upper ocean ventilation and aeration. Expansion of hypoxia in the coastal zone is linked to eutrophication associated with excess nutrients in river runoff, from sources such as chemical fertilizers applied to farms, fields, and lawns. Marine life becomes highly stressed under hypoxic conditions, and dramatic ecological impacts can occur, including massive kills of fish and shellfish and harmful algae blooms. Longer lasting impacts also occur since juvenile fish are more likely to be affected than mature fish, resulting in detrimental follow-on effects such as economic losses. There is a critical need for a deeper understanding of gas cycling in hypoxic zones. Measurement of climatically relevant trace gases are necessary to quantify ocean sources and sinks, and to understand their impact on global climate change. The oceanographic community needs a new, small, low-power, real time dissolved gas sensor that can be tuned to different gases of interest to allow high spatial resolution sampling for specific gases of interest. A platform independent sensor can be used on floats, gliders, conductivity-temperature-depth sensors, and automated underwater vehicles for open water and coastal surveys of dissolved gases. This will not only expand the dissolved gases that a sensor can detected in situ, but bolster scientific discovery, data, and models in areas such as sea-air exchange, greenhouse gases, and hydrothermal vents. The sensing chip consists of a single wall carbon nanotube gas sensor. It is provided by NASA Ames Research Center and has been used to detect several gases in space and on earth to date. For this research, the sensing chip is trained to detect N2O and NO, two gases that are of great interest to the oceanographic community but have not been possible to detect in situ to date. The sea-worthy, submergible housing (to 2000m) will be provided by Pro-Oceanus, an expert in this field. Detection limits aimed for are 100ppb and 5ppb, for N2O and NO respectively. Laboratory testing of the gas sensor and integrated sensing system will take place at APL/UW. Field tests to Hood Canal WA), and the Gulf of Mexico are planned in year 3 of this proposal. If successful, these tests will yield unparalleled spatial resolution of N2O and NO gas concentrations, and allow us to draw conclusions about air-sea interaction that have not been possible to date.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.