Development of Chemical Sensors and In-Situ Calibration: Enhanced Monitoring and Measurement of pH and Redox in Diffuse Flow Hydrothermal Systems

This project requests support for development, calibration, and testing of pH and redox sensors that have recently been incorporated into an auto-calibration system. pH and redox can control mass transfer between geochemical and biological systems existing in areas such as diffuse flow hydrothermal habitats at mid-ocean ridges. To understand the linkages between these systems requires longer term observations, which create the requirement for in-situ calibration of pH and redox sensors. With the availability of power sources at/near deep-sea vents provided by cabled observatories, instrumentation involving in-situ measurement and calibration will be essential to transform qualitative observations to quantitative processes. The PIs propose a three year study involving both field and lab programs with the objective of improving the performance of chemical sensors in complex chemical and biological systems at low to moderate temperatures. Phase one of the study involves technical upgrades to the in-situ calibration device recently deployed at diffuse flows vent sites. Funds requested will be used to add additional pH buffer fluid reservoirs for three point pH calibration for the solid state pH electrode. Moreover, the unit that houses the pH and redox sensors will be redesigned and made smaller to decrease the internal volume and increase signal response time and sensitivity, respectively. Phase two entails reconfiguration of the stand alone calibration unit for real-time measurements, enhancing use with HOV and ROV assets. Laboratory studies are planned that involve testing of ceramic pH electrochemical sensor systems and development of a new Na-based reference electrode that may be particularly suitable for chemical, physical and temporal conditions consistent with long-term monitoring applications at diffuse flow hydrothermal vent sites.