AN OCEANOGRAPHIC CARBON DIOXIDE SENSOR

THE FEASIBILITY OF A SIMPLE ATMOSPHERIC CARBON DIOXIDE (CO2) SENSOR FOR OCEANOGRAPHIC DEPLOYMENT WILL BE EXPLORED IN THIS PHASE I PROJECT. THREE BASIC STEPS ARE REQUIRED FOR SENSOR OPERATION: MEMBRANE EQUILIBRATION OF GASEOUS AND AQUEOUS CO2, CHEMICAL AMPLIFICATION OF THE CONCENTRATION OF THE IONIZED BYPRODUCTS OF CO2 DISSOLUTION, AND SPECIFIC CONDUCTANCE DETECTION. ATMOSPHERIC CO2 EQUILBRATES ACROSS A MICROPOROUS HYDROPHOBIC MEMBRANE WITH AN AQUEOUS PHASE ACCORDING TO HENRY'S LAW. DISSOLVED AQUEOUS CO2 THEN UNDERGOES IONIZATION FORMING CONDUCTIVE SPECIES FOLLOWING THE DISSOCIATION EQUILIBRIA. THIS IONIZATION PROCESS IS CHEMICALLY AMPLIFIED IN A RECIRCULATING AQUEOUS LOOP, USING WATER SOLUBLE ALKANOLAMINES WHICH REVERSIBLY REACT WITH CO2, PRODUCING CONDUCTIVITY CHANGES CORRESPONDING TO THE ATMOSPHERIC CO2 PARTIAL PRESSURE FLUCTUATIONS. THESE CHANGES ARE DETECTED USING EXISTING FLOWTHROUGH CONDUCTIVITY MEASURING DEVICES. THE PLANNED SENSOR OFFES SEVERAL ADVANTAGES INCLUDING ACCURACY OVER THE RANGE OF ATMOSPHERIC CO2 PARTIAL PRESSURES, LOW UNIT COST, AND LOW WEIGHT AND POWER REQUIREMENTS. THE SYSTEM IS ALSO EXPECTED TO BE RESISTANT TO BIOFOULING AND INSENSITIVE TO THE EFFECTS OF STRONG RELATIVE MOTION. ADDITIONAL ADVANTAGES INCLUDE SIMPLICITY, RELIABILITY, EASE OF USE, EASE OF CALIBRATION, EASE OF AUTOMATION, OPERABILITY OVER A WIDE TEMPERATURE RANGE, AND CAPABILITY FOR UNATTENDED OPERATION FOR PERIODS OF UP TO ONE YEAR. THE METHOD CAN ALSO BE EXTENDED TO DETERMINE DISSOLVED CO2 IN SEA WATER.