%0 Journal Article
%T Evaluation of a cavity ring-down spectrometer for in situ observations of 13CO2
%A F. R. Vogel
%A L. Huang
%A D. Ernst
%A L. Giroux
%A S. Racki
%A D. E. J. Worthy
%J Atmospheric Measurement Techniques (AMT) & Discussions (AMTD)
%D 2013
%I Copernicus Publications
%X With the emergence of wide-spread application of new optical techniques to monitor ¦Ä13C in atmospheric CO2 there is a growing need to ensure well-calibrated measurements. We characterized one commonly available instrument, a cavity ring-down spectrometer (CRDS) system used for continuous in situ monitoring of atmospheric 13CO2. We found no dependency of ¦Ä13C on the CO2 concentration in the range of 303¨C437 ppm. We designed a calibration scheme according to the diagnosed instrumental drifts and established a quality assurance protocol. We find that the repeatability (1-¦Ò) of measurements is 0.25¡ë for 10 min and 0.15¡ë for 20 min integrated averages, respectively. Due to a spectral overlap, our instrument displays a cross-sensitivity to CH4 of 0.42 ¡À 0.024¡ë ppm 1. Our ongoing target measurements yield standard deviations of ¦Ä13C from 0.22¡ë to 0.28¡ë for 10 min averages. We furthermore estimate the reproducibility of our system for ambient air samples from weekly measurements of a long-term target gas to be 0.18¡ë. We find only a minuscule offset of 0.002 ¡À 0.025¡ë between the CRDS and Environment Canada's isotope ratio mass spectrometer (IRMS) results for four target gases used over the course of one year.
%U http://www.atmos-meas-tech.net/6/301/2013/amt-6-301-2013.html