An experimental set-up for carbon isotopic analysis of atmospheric CO 2 and an example of ecosystem response during solar eclipse 2010

2013 Proceedings of the Indian Academy of Sciences, Earth and Planetary Sciences  
We present here, an experimental set-up developed for the first time in India for the determination of mixing ratio and carbon isotopic ratio of air-CO 2 . The set-up includes traps for collection and extraction of CO 2 from air samples using cryogenic procedures, followed by the measurement of CO 2 mixing ratio using an MKS Baratron gauge and analysis of isotopic ratios using the dual inlet peripheral of a high sensitivity isotope ratio mass spectrometer (IRMS) MAT 253. The internal
more » ... internal reproducibility (precision) for the δ 13 C measurement is established based on repeat analyses of CO 2 ± 0.03 . The set-up is calibrated with international carbonate and air-CO 2 standards. An in-house air-CO 2 mixture, 'OASIS AIRMIX' is prepared mixing CO 2 from a high purity cylinder with O 2 and N 2 and an aliquot of this mixture is routinely analyzed together with the air samples. The external reproducibility for the measurement of the CO 2 mixing ratio and carbon isotopic ratios are ±7 (n = 169) μmol·mol −1 and ±0.05 (n = 169) based on the mean of the difference between two aliquots of reference air mixture analyzed during daily operation carried out during November 2009-December 2011. The correction due to the isobaric interference of N 2 O on air-CO 2 samples is determined separately by analyzing mixture of CO 2 (of known isotopic composition) and N 2 O in varying proportions. A +0.2 correction in the δ 13 C value for a N 2 O concentration of 329 ppb is determined. As an application, we present results from an experiment conducted during solar eclipse of 2010. The isotopic ratio in CO 2 and the carbon dioxide mixing ratio in the air samples collected during the event are different from neighbouring samples, suggesting the role of atmospheric inversion in trapping the emitted CO 2 from the urban atmosphere during the eclipse. the intercomparison of data between different laboratories to merge the data for better understanding
doi:10.1007/s12040-013-0303-1 fatcat:do3t2uvosveepfpp3mhlim3afi