New pH sensor for monitoring ocean acidifcation

Abstract

The QUIMA group at the University of Las Palmas de Gran Canaria and SensorLab have developed a new family of rugged and extremely stable spectrophotometric pH sensors for both lab-based research and buoy monitoring, specifcally designed for unattended operation independently of dye and aging effects in surface waters. Achieving high accuracy in open water proved to be quite challenging, as the pressure changes due to the swell caused small, short-term pH measurement errors. A pressure compensation system was designed and implemented so the undesirable effects of pressure variations fell below the measurement uncertainty. The presence of fouling was a big challenge as well. The design of the pH sensors allows for the same accuracy achievable in the lab, but autonomously deployed in the ocean, enabling long-term measurements without human intervention. As environmental conditions change, the sensor is designed to adjust all the measurement parameters automatically to provide maximum accuracy. An important point to note is that the system also returns the internally calculated error for each measurement.