Carbon dioxide determination in atmosphere and seawater: Approaches for the comparability of measurement results

The rising levels of carbon dioxide in the atmosphere are responsible for fundamental changes occurring in seawater carbonate chemistry. For both air and water, there is a pressing need to assure metrological traceability thus obtaining comparable measurement results on spatial and temporal scales. At INRIM several activities are carried out to establish the metrological traceability for carbon dioxide measurement results. Two primary methods, the gravimetry and the dynamic dilution, are used for the preparation of reference standards for composition which can be used to calibrate sensors and analytical instrumentation for carbon dioxide determination both in atmosphere and seawater. An overview of possible approaches is given.