Sensitive detection of atmospheric N2O isotopomers using a quantum cascade laser based spectrometer

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: (NNO)-N-14-N-15-O-16, (NNO)-N-15-N-14-O-16 and (N2O)-N-14-O-16. The experiment results showed that site-selective N-15/N-14 can be measured with the precision of 0.59 parts per thousand 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. (C) 2019 Elsevier Ltd. All rights reserved.