Development and Deployment of Autonomous and Remotely Operated Chemical Sensor System: Integrated Laboratory and Field Studies of Seafloor Hydrothermal Vent Fluids

This project involves the continued development, integration, and application of chemical sensor systems that can be used autonomously to monitor key components in hydrothermal vent fluids at mid-ocean ridges. Hydrothermal vent fluids play a key role in the Earth sciences in helping to maintain ocean chemistry, while also providing chemicals essential for the origin and evolution of the spectacular communities of organisms associated with deep sea vents- now and in the ancient geological past. Here the investigators identify an integrated program of technical modifications and laboratory and vent related studies that will enhance the effectiveness of chemical sensor data for interpretation of deep-sea hydrothermal vent systems. The investigation will contribute to the enhancement of research infrastructure that will be available to ocean scientists and engineers involved in research and training in a wide range of disciplinary areas. Collaboration with colleagues in engineering at the University of Michigan and Zhejiang University in China has broadened participation in ocean science research and has allowed the investigators to apply recent advances in nanotechnology, micromachining, and process control software and hardware in developing concepts needed for the next generation of autonomous chemical sensor systems. Development of chemical sensors with autonomous operation capabilities is also important as progress is being made with fiber-optic cabled ocean observatories, which will provide power for instruments on the seafloor and ultimately at deep-sea vents, facilitating longer term measurements and unattended operation. Moreover, the research will benefit from the participation of undergraduate students in connection with the NSF Research Experiences for Undergraduates (REU) program - Fluids in the Earth. Graduate students at the University of Minnesota will also participate in the research. Indeed undergraduate and graduate students have worked with the investigators on sensor applications and participated in oceanographic research cruises, while playing a key role in the deployment on the seafloor of chemical sensors and vent fluid sampling systems that they helped to create.

Redox and pH represent master variables in all geochemical and biological systems. Thus, this research focuses on enhancing the measurement of these parameters for longer times and over a greater range of temperatures. Accordingly, the objectives are as follows: (1) Extend the autonomous in-situ calibration module to include redox components (e.g., dissolved H2S); (2) Replace conventional ceramic sensor for pH measurement with a functionally similar device composed of nano-ceramic, potentially enhancing measurements at lower temperatures with less frequent need for calibration. Recent advances in nanotechnology and microelectronics now make this possible; (3) Couple electrochemical sensor systems with newly developed hydrothermal fluid samplers for sensor triggered autonomous acquisition of hydrothermal fluid. By coupling the sensor system with a fluid sampling system, the investigators will achieve an instrument that combines event detection with event response; (4) Perform network (internet, LAN) tests of refined automation protocols; (5) Integrate lab and field calibration and verification measurements with deployments at seafloor hydrothermal vents in the Eastern Pacific ocean. The researchers have considerable experience at this vent system, and the data obtained will contribute to both technical and scientific objectives; and, (6) Conduct high-temperature lab experiments using a newly designed flow reactor adapted with ceramic-based pH sensors. These studies permit testing of recent predictions of elevated pH values at near critical conditions based on earlier pH (in-situ) data measured at the seafloor.