An autonomous sensor and telemetry system for low-level pCO2 measurements in seawater

The measurement of low-level dissolved C[O.sub.2] using a fiberoptic sensor is described. The sensor, based on the Severinghaus C[O.sub.2] electrode principle, consists of a C[O.sub.2]sensitive bicarbonate buffer solution containing the pH-sensitive fluorescent dye carboxy-SNAFL-1 immobilized at the end of an optical fiber using a gas-permeable membrane. The sensor is used in a ratiometric mode and has a reversible working dynamic range between 200 and 1000 ppm pC[O.sub.2] and a sensitivity [+ or -]1 ppm. Results are presented for the sensor calibration, effects of temperature, and response time characteristics. An integrated measurement system with electrooptic and data acquisition modules coupled to a satellite transmission system was tested in Vineyard Sound, MA, and data are presented that demonstrate continuous monitoring of pC[O.sub.2] in surface seawater.