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

TANIA GUHA, PROSENJIT GHOSH
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