Abstract
Stable isotope analytical techniques have a crucial role to play in the study of atmospheric pollutant and trace gas sources, sinks and transport processes. Quantum cascade laser absorption spectroscopy (QCLAS) allows the site-selective and high-precision analysis of many isotopic species at trace levels, yet not sensitive enough for atmospheric N2O mixing ratios. In this study, a quantum cascade laser based spectrometer combining with a liquid nitrogen-free preconcentration unit was developed to demonstrate the applicability of high sensitivity and high precision measurement of atmospheric N2O isotopomers. Primary laboratory tests have been performed for simultaneous determination of the mixing ratios of the most abundant nitrous oxide isotopic species: 14N15N16O, 15N14N16O and 14N216O. The experiment results showed that site-selective 15N/14N can be measured with the precision of 0.59‰ with an optimal averaging time of 258 s at 100 ppm. Details of spectral absorption line pairs selection and N2O adsorption/desorption processes are also discussed.
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