Ultrasonic detector for high precision measurements of carbon dioxide

A new instrument for monitoring atmospheric C[O.sub.2] has been developed based on the measurement of the speed of sound in air. The instrument uses a selective scrubber to yield highly precise and accurate measurements of C[O.sub.2] mixing ratios at ambient concentrations. The instrument has a precision of 0.3 ppmv (1[sigma]) with a signal that is independent of pressure and requires a flow rate of only 30 mL/min. Laboratory measurements of atmospheric C[O.sub.2] showed excellent agreement with values obtained by nondispersive infrared absorption. The instrument has the advantage of collecting continuous, high-precision data every 25 s and can be modified for vertical profiling studies using kites, balloons, or light aircraft for the purpose of measuring landscape-scale fluxes. 10.1021/ac101365p