A novel fiber-optic sensor for the long-term, autonomous measurement of pCO2 in seawater

A new fluorescence based fiber optic sensor with high sensitivity and accuracy, on the order of 1-2 μatm, has been developed that will allow for the long-term, autonomous, continuous measurement of the partial pressure of carbon dioxide in ocean waters. The initial use is the monitoring and mapping of the oceanic distribution of carbon dioxide to better understand the fate of industrial carbon dioxide and the air-sea flux of carbon dioxide. A single excitation, dual emission, pH sensitive dye was selected. This allowed for the use of a ratiometric technique that results in the sensor being independent of dye concentration changes. Field testing has been undertaken using a multi-parameter buoy equipped with both air and seawater carbon dioxide sensors, as well as dissolved oxygen (DO), pH, water temperature, conductivity, wind speed and direction, solar radiation, and air temperature sensors. In addition to the observation of a diurnal cycle in the surface water pCO₂ values, there were strong correlations between the seawater pCO₂ and both DO and pH