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High-precision Dual-inlet Irms Measurements of the Stable Isotopes of Co2 and the N2O / Co2 Ratio from Polar Ice Core Samples : Volume 7, Issue 11 (19/11/2014)

By Bauska, T. K.

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Book Id: WPLBN0003999523
Format Type: PDF Article :
File Size: Pages 13
Reproduction Date: 2015

Title: High-precision Dual-inlet Irms Measurements of the Stable Isotopes of Co2 and the N2O / Co2 Ratio from Polar Ice Core Samples : Volume 7, Issue 11 (19/11/2014)  
Author: Bauska, T. K.
Volume: Vol. 7, Issue 11
Language: English
Subject: Science, Atmospheric, Measurement
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Historic
Publication Date:
2014
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

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Brook, E. J., Ross, A., Mix, A. C., & Bauska, T. K. (2014). High-precision Dual-inlet Irms Measurements of the Stable Isotopes of Co2 and the N2O / Co2 Ratio from Polar Ice Core Samples : Volume 7, Issue 11 (19/11/2014). Retrieved from http://www.ebooklibrary.org/


Description
Description: College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA. An important constraint on mechanisms of past carbon cycle variability is provided by the stable isotopic composition of carbon in atmospheric carbon dioxide (δ13C-CO2) trapped in polar ice cores, but obtaining very precise measurements has proven to be a significant analytical challenge. Here we describe a new technique to determine the δ13C of CO2 at very high precision, as well as measuring the CO2 and N2O mixing ratios. In this method, ancient air is extracted from relatively large ice samples (~400 g) with a dry-extraction ice grater device. The liberated air is cryogenically purified to a CO2 and N2O mixture and analyzed with a microvolume-equipped dual-inlet IRMS (Thermo MAT 253). The reproducibility of the method, based on replicate analysis of ice core samples, is 0.02‰ for δ13C-CO2 and 2 ppm and 4 ppb for the CO2 and N2O mixing ratios, respectively (1σ pooled standard deviation). Our experiments show that minimizing water vapor pressure in the extraction vessel by housing the grating apparatus in a ultralow-temperature freezer (−60 °C) improves the precision and decreases the experimental blank of the method to −0.07 ± 0.04‰. We describe techniques for accurate calibration of small samples and the application of a mass-spectrometric method based on source fragmentation for reconstructing the N2O history of the atmosphere. The oxygen isotopic composition of CO2 is also investigated, confirming previous observations of oxygen exchange between gaseous CO2 and solid H2O within the ice archive. These data offer a possible constraint on oxygen isotopic fractionation during H2O and CO2 exchange below the H2O bulk melting temperature.

Summary
High-precision dual-inlet IRMS measurements of the stable isotopes of CO2 and the N2O / CO2 ratio from polar ice core samples

Excerpt
Ahn, J., Brook, E. J., and Howell, K.: A high-precision method for measurement of paleoatmospheric CO2 in small polar ice samples, J. Glaciol., 55, 499–506, 2009.; Assonov, S. S. and Brenninkmeijer, C. A. M.: On the N2O correction used for mass spectrometric analysis of atmospheric CO2, Rapid Commun. Mass Sp., 20, 1809–1819, doi:10.1002/rcm.2516, 2006.; Assonov, S. S., Brenninkmeijer, C. A. M., and Jöckel, P.: The 18O isotope exchange rate between firn air CO2 and the firn matrix at three Antarctic sites, J. Geophys. Res.-Atmos., 110, D18310, doi:10.1029/2005JD005769, 2005.; Bertolini, T., Rubino, M., Lubritto, C., D'Onofrio, A., Marzaioli, F., Passariello, I., and Terrasi, F.: Optimized sample preparation for isotopic analyses of CO2 in air: systematic study of precision and accuracy dependence on driving variables during CO2 purification process, J. Mass Spectrom., 40, 1104–1108, 2005.; Bottinga, Y. and Craig, H.: Oxygen isotope fractionation between CO2 and water, and the isotopic composition of marine atmospheric CO2, Earth Planet. Sc. Lett., 5, 285–295, 1968.; Brenninkmeijer, C. A. M., Kraft, P., and Mook, W. G.: Oxygen Isotope Fractionation Between CO2 and H2O, Isot. Geosci., 1, 181–190, 1983.; Ellehoj, M. D., Steen-Larsen, H. C., Johnsen, S. J., and Madsen, M. B.: Ice-vapor equilibrium fractionation factor of hydrogen and oxygen isotopes: Experimental investigations and implications for stable water isotope studies, Rapid Commun. Mass Sp., 27, 2149–2158, doi:10.1002/rcm.6668, 2013.; Elsig, J., Schmitt, J., Leuenberger, D., Schneider, R., Eyer, M., Leuenberger, M., Joos, F., Fischer, H., and Stocker, T. F.: Stable isotope constraints on Holocene carbon cycle changes from an Antarctic ice core, Nature, 461, 507–510, doi:10.1038/nature08393, 2009.; Fischer, H., Severinghaus, J., Brook, E., Wolff, E., Albert, M., Alemany, O., Arthern, R., Bentley, C., Blankenship, D., Chappellaz, J., Creyts, T., Dahl-Jensen, D., Dinn, M., Frezzotti, M., Fujita, S., Gallee, H., Hindmarsh, R., Hudspeth, D., Jugie, G., Kawamura, K., Lipenkov, V., Miller, H., Mulvaney, R., Parrenin, F., Pattyn, F., Ritz, C., Schwander, J., Steinhage, D., van Ommen, T., and Wilhelms, F.: Where to find 1.5 million yr old ice for the IPICS Oldest-Ice ice core, Clim. Past, 9, 2489–2505, doi:10.5194/cp-9-2489-2013, 2013.; Mader, H. M.: Observations of the water-vein system in polycrystalline ice, J. Glaciol., 38, 333–347, 1992.; Flückiger, J., Blunier, T., Stauffer, B., Chappellaz, J., Spahni, R., Kawamura, K., Schwander, J., Stocker, T. F., and Dahl-Jensen, D.: N2O and CH4 variations during the last glacial epoch: Insight into global processes, Global Biogeochem. Cy., 18, GB1020, doi:10.1029/2003GB002122, 2004.; Francey, R. J., Allison, C. E., Etheridge, D. M., Trudinger, C. M., Enting, I. G., Leuenberger, M., Langenfelds, R. L., Michel, E., and Steele, L. P.: A 1000-year high precision record of δ13C in atmospheric CO2, Tellus B, 51, 170–193, doi:10.1034/j.1600-0889.1999.t01-1-00005.x, 1999.; Friedli, H. and Siegenthaler, U.: Influence of N2O on isotope analyses in CO2 and mass-spectrometric determination of N2O i

 

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