An autonomous sensor and telemetry system for low-level pCO(2) measurements in seawater

The measurement of low-level dissolved CO2 using a fiber-optic sensor is de scribed. The sensor, based on the Severinghaus CO2 electrode principle, con sists of a CO2-sensitive bicarbonate buffer solution containing the pH-sens itive 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 m ode and has a reversible working dynamic range between 200 and 1000 ppm pCO (2) and a sensitivity +/-1 ppm. Results are presented for the sensor calibr ation, effects of temperature, and response time characteristics. An integr ated measurement system with electrooptic and data acquisition modules coup led to a satellite transmission system was tested in Vineyard Sound, MA, an d data are presented that demonstrate continuous monitoring of pCO(2) in su rface seawater.