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

点击翻译按钮获取中文摘要

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.