Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 7 2 2007 10.5194/acp-7-495-2007 http://www.atmos-chem-phys.net/7/495/2007/ http://www.atmos-chem-phys.net/7/495/2007/acp-7-495-2007.html http://www.atmos-chem-phys.net/7/495/2007/acp-7-495-2007.pdf 495 509 2007-01-26 Investigations of the photochemical isotope equilibrium between O₂, CO₂ and O₃ R. Shaheen robina.shaheen@mpi-hd.mpg.de C. Janssen T. Röckmann Max-Planck-Institute for Nuclear Physics, Division of Atmospheric Physics, 69117 Heidelberg, Germany University of California San Diego, Department of Chemistry, La Jolla, USA Laboratoire de Physique Moléculaire pour l'Atmosphère et l'Astrophysique, Université Pierre et Marie Curie/CNRS, 75252 Paris, France Institute for Marine and Atmospheric Research Utrecht, Utrecht University, The Netherlands Contrary to tropospheric CO₂ whose oxygen isotopic composition follows a standard mass dependent relationship, i.e. δ¹⁷O~0.5δ¹⁸O, stratospheric CO₂ is preferentially enriched in ¹⁷O, leading to a strikingly different relation: δ¹⁷O~1.7δ¹⁸O. It has been shown repeatedly that the isotope anomaly is inherited from O₃ via photolytically produced O(¹D) that undergoes isotope exchange with CO₂ and the anomaly may well serve as a tracer of stratospheric chemistry if details of the exchange mechanism are understood. We have studied the photochemical isotope equilibrium in UV-irradiated O₂-CO₂ and O₃-CO₂ mixtures to quantify the transfer of the anomaly from O₃ to CO₂ at room temperature. By following the time evolution of the oxygen isotopic compositions of CO₂ and O₂ under varying initial isotopic compositions of both, O₂/O₃ and CO₂, the isotope equilibria between the two reservoirs were determined. A very strong dependence of the isotope equilibrium on the O₂/CO₂-ratio was established. Equilibrium enrichments of ¹⁷O and ¹⁸O in CO₂ relative to O₂ diminish with increasing CO₂ content, and this reduction in the equilibrium enrichments does not follow a standard mass dependent relation. When molecular oxygen exceeds the amount of CO₂ by a factor of about 20, ¹⁷O and ¹⁸O in equilibrated CO₂ are enriched by (142±4)‰ and (146±4)‰, respectively, at room temperature and at a pressure of 225 hPa, independent of the initial isotopic compositions of CO₂ and O₂ or O₃. From these findings we derive a simple and general relation between the starting isotopic compositions and amounts of O₂ and CO₂ and the observed slope in a three oxygen isotope diagram. Predictions from this relation are compared with published laboratory and atmospheric data. Assonov, S S. and Brenninkmeijer, C. A M.: A new method to determine the $^17$O isotopic abundance in CO₂ using oxygen isotope exchange with a solid oxide, Rapid Communications in Mass Spectrometry, 15, 2426–2437, 2001. Bains-Sahota, S K. and Thiemens, M H.: A Chemically Produced Non-Mass Dependent Sulfur Isotope Effect, Meteoritics, 22, 320–321, 1987. Blunier, T., Barnett, B., Bender, M L., and Hendricks, M B.: Biological oxygen productivity during the last 60,000 years from triple oxygen isotope measurements, Global Biogeochem. Cycles, 16, 1029, \doi10.1029/2001GB001460, 2002. Boering, K A., Jackson, T., Hoag, K J., Cole, A S., Perri, M J., Thiemens, M., and Atlas, E.: Observations of the anomalous oxygen isotopic composition of carbon dioxide in the lower stratosphere and the flux of the anomaly to the troposphere, Geophys. Res. Lett., 31, L03109, \doi10.1029/2003GL018451, 2004. Brenninkmeijer, C. A M., Janssen, C., Kaiser, J., Röckmann, T., Rhee, T S., and Assonov, S S.: Isotope effects in the chemistry of atmospheric trace compounds, Chem. Rev., 103, 5125–5161, 2003. Chakraborty, S. and Bhattacharya, S K.: Experimental investigation of oxygen isotope exchange between CO₂ and O($^1\!\rm D$) and its relevance to the stratosphere, J. Geophys. Res., 108, 4724, doi:10.1029/2002JD002915, 2003. Ciais, P., Denning, A S., Tans, P P., Berry, J A., Randall, D A., Collatz, G J., Sellers, P J., White, J. W C., Trolier, M., Meijer, H. A J., Francey, R J., Monfray, P., and Heimann, M.: A three-dimensional synthesis study of $\rm \delta ^18O$ in atmospheric CO₂. 1. Surface fluxes, J. Geophys. Res., 102, 5857–5872, 1997. Farquhar, G D., Lloyd, J., Taylor, J A., Flanagan, L B., Syvertsen, J P., Hubick, K T., Wong, S C., and Ehleringer, J R.: Vegetation effects on the isotope composition of oxygen in atmospheric CO₂, Nature, 363, 439–443, 1993. Guenther, J., Krankowsky, D., and Mauersberger, K.: Third-body dependence of rate coefficients for ozone formation in $\rm ^16O−\rm^18O$ mixtures, Chem. Phys. Lett., 324, 31–36, 2000. Haverd, V., Toon, G C., and Griffith, D. W T.: Evidence for altitude-dependent photolysis-induced $^18$O isotopic fractionation in stratospheric ozone, Geophys. Res. Lett., 32, L22808, doi:10.1029/2005GL024049, 2005. Janssen, C.: Intramolecular isotope distribution in heavy ozone ($\rm ^16O^18O^16O$ and $\rm ^16O^16O^18O$), J. Geophys. Res., 110, D08308, \doi10.1029/2004JD005479, 2005. Janssen, C. and Tuzson, B.: A diode laser spectrometer for symmetry selective detection of ozone isotopomers, Appl. Phys. B, 82, 487–494, 2006. Janssen, C., Guenther, J., Krankowsky, D., and Mauersberger, K.: Temperature dependence of ozone rate coefficients and isotopologue fractionation in $\rm ^16O−\rm^18O$ oxygen mixtures, Chem. Phys. Lett., 367, 34–38, 2003. Johnston, J C., Röckmann, T., and Brenninkmeijer, C. A M.: CO$_2+\rm O(^1\!\rm D)$ isotopic exchange: Laboratory and modeling studies, J. Geophys. Res., 105, 15 213–15 229, 2000. Lämmerzahl, P., Röckmann, T., Brenninkmeijer, C. A M., Krankowsky, D., and Mauersberger, K.: Oxygen isotope composition of stratospheric carbon dioxide, Geophys. Res. Lett., 12, 1582, doi:10.1029/2001GL014343, 2002. Liang, M C., Irion, F W., Weibel, J D., Miller, C E., Blake, G A., and Yung, Y L.: Isotopic composition of stratospheric ozone, J. Geophys. Res., 111, D02 302, doi:10.1029/2005JD006342, 2006. Luz, B., Barkan, E., Bender, M L., Thiemens, M H., and Boering, K A.: Triple-isotope composition of atmospheric oxygen as a tracer of biosphere productivity, Nature, 400, 547–550, 1999. Mauersberger, K., Morton, J., Schueler, B., Stehr, J., and Anderson, S M.: Multi-Isotope Study of Ozone - Implications for the Heavy Ozone Anomaly, Geophys. Res. Lett., 20, 1031–1034, 1993. Mauersberger, K., Lämmerzahl, P., and Krankowsky, D.: Stratospheric ozone isotope enrichments – revisited, Geophys. Res. Lett., 28, 3155–3158, 2001. Mebel, A M., Hayashi, M., Kislov, V V., and Lin, S H.: Theoretical Study of Oxygen Isotope Exchange and Quenching in the O($^1$D) + CO₂ Reaction, J. Phys. Chem. A, 108, 7983–7994, prefixhttp://dx.doi.org/10.1021/jp049315h, 2004. Mentges, J.: Line sources, technical data sheet, prefixhttp://www.lot-oriel.com/site/site_down/ls_calibration_deen03% .pdf, 2006. Miller, C E., Onorato, R M., Liang, M C., and Yung, Y L.: Extraordinary isotopic fractionation in ozone photolysis, Geophys. Res. Lett., 32, L14814, doi:10.1029/2005GL023160, 2005. Mook, W G., ed.: Environmental Isotopes in the Hydrological Cycle: Principles and Applications, vol I, IAEA, prefixhttp://www.iaea.org/programmes/ripc/ih/volumes/volumes.htm, 2001. Morton, J., Barnes, J., Schueler, B., and Mauersberger, K.: Laboratory studies of heavy ozone, J. Geophys. Res., 95, 901–907, 1990. Perri, M J., Van~Wyngarden, A L., Boering, K A., Lin, J J., and Lee, Y T.: Dynamics of the O($^1$D) + CO₂ oxygen isotope exchange reaction, J. Chem. Phys., 119, 8213–8216, 2003. Perri, M J., Van~Wyngarden, A L., Lin, J J., Lee, Y T., and Boering, K A.: Energy dependence of oxygen isotope exchange and quenching in the O($^1$D) + CO₂ reaction: A crossed molecular beam study, J. Phys. Chem. A, 108, 7995–8001, 2004. Reader, J., Sansonetti, C J., and Bridges, J M.: Irradiances of spectral lines in mercury pencil lamps, Appl. Opt., 35, 78–83, 1996. Röckmann, T.: Measurement and interpretation of $^13$C, $^14$C, $^17$O and $^18$O variations in atmospheric carbon monoxide, Ph.D. thesis, University of Heidelberg, 1998. Sander, S P., Friedl, R R., Golden, D M., Kurylo, M J., Huie, R E., Orkin, V L., Moortgat, G K., Ravishankara, A R., Kolb, C E., Molina, M J., and Finlayson-Pitts, B J.: Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies, Evaluation Number 14, JPL Publication 02-25, 2003. Takahashi, K., Taniguchi, N., Sato, Y., and Matsumi, Y.: Nonthermal steady state translational energy distributions of O($^1$D) atoms in the stratosphere, J. Geophys. Res., 107, ACH 6-1–ACH 6-6, 2002. Thiemens, M H. and Jackson, T.: Pressure Dependency for Heavy Isotope Enhancement in Ozone Formation, Geophys. Res. Lett., 17, 717–719, 1990. Thiemens, M H., Jackson, T., Mauersberger, K., Schueler, B., and Morton, J.: Oxygen isotope fractionation in stratospheric $\rm CO_2$, Geophys. Res. Lett., 18, 669–672, 1991. Thiemens, M H., Jackson, T., Zipf, E C., Erdman, P W., and Van Egmond, C.: Carbon Dioxide and Oxygen Isotope Anomalies in the Mesosphere and Stratosphere, Science, 270, 969–972, 1995. Tuzson, B. and Janssen, C.: Unambiguous identification of $^17$O containing ozone isotopomers for symmetry selective detection, Isotopes Environ. Health Studies, 42, 67–75, 2006. Tuzson, B. and Janssen, C.: Temperature and Pressure Dependence of Ozone Isotopomer Formation: A Symmetry Resolved Study, in press, 2007. Wen, J. and Thiemens, M H.: Multi-Isotope Study of the $\rm O(^1$D)+CO₂ Exchange and Stratospheric Consequences, J. Geophys. Res., 98, 12 801–12 808, 1993. Yung, Y L., DeMore, W B., and Pinto, J P.: Isotopic Exchange between Carbon Dioxide and Ozone Via O($^1$D) in the Stratosphere, Geophys. Res. Lett., 18, 13–16, 1991.