An ocean sensor for measuring the seawater electrochemical response of 8 metals referenced to zinc, for determining ocean pH

Abstract

Abstract-We describe the use of a multi-metal electrochemical cell for measuring ocean pH. The sensor was designed to be robust, inexpensive, and capable of 0.02 sensitivity to pH in the narrow ranges required for marine pH monitoring. A prototype sensor has undergone an extended ocean deployment with promising results.Ocean Sensors; pH Sensors; Metal electrochemistry; Arduino. I. TECHNOLOGY APPROACHThe idea behind the sensor comes from the very low cost unpowered sensors used for soil pH measurements [1]. These simple meters use two metals to generate a potential that is read on an analog meter and are surprisingly accurate at measuring soil pH. We purchased and tested many of these sensors and were very impressed with the accuracy and repeatability of this simple technology. Based on this idea we measured the potential across Zinc and Copper in pH buffered solutions of Instant Ocean. We found that we could calibrate the electrochemical cell to approximately 0.02 pH for the pH 7-9 range. This led to the idea that we could use metals for a useful low cost ocean pH sensor. II. POTENTIAL PROBLEMSBiofouling and corrosion will alter the metal surfaces over time [2], and the metal surface potentials will be sensitive to chemical potentials other than just pH. To overcome this we propose using metal diversity. We are currently using 9 different ¼ inch metal rods in our prototype sensor (Figure 1). These are all mass produced and available at low cost.

Remote Supervision System for Aquaculture Platforms

“…Brooke et al [18] present their work in an underwater sensor module for determining ocean pH. The system is essentially a straightforward data logger.…”