A fully automatic system for underway N2O measurements based on cavity ring-down spectroscopy

ABSTRACTN2O is one of the most important greenhouse and ozone-depleting gases and has been the source of considerable concern in recent years. The oceans account for ~ 1/4 of the global N2O emission budget; however, the oceanic N2O source/sink characteristics are not well understood. To enhance the study of oceanic N2O source/sink characteristics, our laboratory developed a fully automatic underway system for surface water N2O concentration and atmospheric N2O mole fraction measurements consisting of a cavity ring-down spectroscopy (CRDS) instrument and an upstream device. The developed device can be programmed to switch the CRDS measurements from the equilibrator headspace to the atmospheric sample and the reference gas sample. The surface water N2O concentration is calculated from the equilibrium headspace N2O mole fraction in the equilibrator. The response time of this equilibrator is ~ 3.4 min, and the estimated precision of this method for surface water N2O measurements is better than 0.5% (relative ...