ACCURATE HEADSPACE ANALYSIS OF FCO(2) IN DISCRETE WATER SAMPLES USINGBATCH EQUILIBRATION

A high-accuracy, batch-equilibration, static-headspace technique for t he determination of the fugacity of CO2 (fCO(2)) in discrete water sam ples is described. The technique was designed for monitoring small cha nges of CO2 in the ocean and has accuracy and precision (<1% for water samples) comparable to that of the best techniques available. The met hod uses several novel approaches to maximize accuracy, requires only a small water sample (60 ml), and is very rapid (similar to 2 min per analysis). Precision of the calculated total alkalinity, based on the measured fCO(2) and C-T, is comparable to or better than is generally attained using potentiometric titration. Compared with C-T and total a lkalinity measurements, the small sample volume and rapid analysis tim e makes it practical to perform analysis of multiple replicates in ord er to improve confidence in the result. The method is readily applicab le to experimental studies such as incubations as well as to time-seri es measurements of in situ biological metabolism. Because the analysis employs gas chromatography, the technique can be adapted to measure s imultaneously a suite of gases dissolved in seawater.