ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-9-8503-2009 A consistent molecular hydrogen isotope chemistry scheme based on an independent bond approximation Pieterse G. 1 Krol M. C. 1 Röckmann T. 1 Institute for Marine and Atmospheric Research Utrecht, Utrecht, The Netherlands 09 11 2009 9 21 8503 8529 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/9/8503/2009/acp-9-8503-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/9/8503/2009/acp-9-8503-2009.pdf

The isotopic composition of molecular hydrogen (H<sub>2</sub>) produced by photochemical oxidation of methane (CH<sub>4</sub>) and Volatile Organic Compounds (VOCs) is a key quantity in the global isotope budget of (H<sub>2</sub>). The many individual reaction steps involved complicate its investigation. Here we present a simplified structure-activity approach to assign isotope effects to the individual elementary reaction steps in the oxidation sequence of CH<sub>4</sub> and some other VOCs. The approach builds on and extends the work by Gerst and Quay (2001) and Feilberg et al. (2007b). The description is generalized and allows the application, in principle, also to other compounds. The idea is that the C-H and C-D bonds – seen as reactive sites – have similar relative reaction probabilities in isotopically substituted, but otherwise identical molecules. The limitations of this approach are discussed for the reaction CH<sub>4</sub>+Cl. The same approach is applied to VOCs, which are important precursors of H<sub>2</sub> that need to be included into models. Unfortunately, quantitative information on VOC isotope effects and source isotope signatures is very limited and the isotope scheme at this time is limited to a strongly parameterized statistical approach, which neglects kinetic isotope effects. Using these concepts we implement a full hydrogen isotope scheme in a chemical box model and carry out a sensitivity study to identify those reaction steps and conditions that are most critical for the isotope composition of the final H<sub>2</sub> product. The reaction scheme is directly applicable in global chemistry models, which can thus include the isotope pathway of H<sub>2</sub> produced from CH<sub>4</sub> and VOCs in a consistent way.

 References Allan, W., Struthers, H., and Lowe, D.: Methane carbon isotope effects caused by atomic chlorine in the marine boundary layer: Global model results compared with Southern Hemisphere measurements, J. Geophys. Res., 112, D04306, doi:10.1029/2006JD007369, 2007. Arsene, C., Bougiatioti, A., Kanakidou, M., Bonsang, B., and Mihalopoulos, N.: Tropospheric OH and Cl levels deduced from non-methane hydrocarbon measurements in a marine site, Atmos. Chem. Phys., 7, 4661–4673, 2007. Atkinson, R.: Kinetics and mechanisms of the gas-phase reactions of the OH radical with organic compounds under atmospheric conditions, Chem. Rev., 86, 69–201, 1986. Atkinson, R.: A Structure-Activity Relationship for the Estimation of Rate Constants for the Gas-Phase Reactions of OH Radicals with Organic Compounds, Int. J. Chem. Kin., 19, 799–828, 1987. Atkinson, R., Baulch, D. L., Cox, R. A., Crowley, J. N., Hampson, R. F., Hynes, R. G., Jenkin, M. E., Rossi, M. J., Troe, J., and IUPAC Subcommittee: Evaluated kinetic and photochemical data for atmospheric chemistry: Volume II – gas phase reactions of organic species, Atmos. Chem. Phys., 6, 3625–4055, 2006. Bacher, C., Tyndall, G S., and Orlando, J J.: The Atmospheric Chemistry of Glycolaldehyde, J. Atmos. Chem., 39, 171–189, 2001. Barnes, I., Becker, K H., and Ruppert, L.: FTIR product study of the self-reaction of β-hydroxyethyl peroxy radicals, Chem. Phys. Lett., 203, 295–301, 1993. Brenninkmeijer, C. A M., Janssen, C., Kaiser, J., Röckmann, T., Rhee, R S., and Assonov, S S.: Isotope effects in the chemistry of atmospheric trace components, Chem. Rev., 103, 5125–5161, 2003. Cantrell, C. A., Shetter, R. E., McDaniel, A. H., Calvert, J. G., Davidson, J. A., Lowe, D. C., Tyler, S. C., Cicerone, R. J., and Greenberg, J. P.: Carbon kinetic isotope effect in the oxidation of methane by the hydroxyl radical, J. Geophys. Res., 95D, 455–462, 1990. Derwent, R G., Jenkin, M E., Saunders, S M., and Pilling, M J.: Photochemical ozone creation potentials for organic compounds in North West Europe calculated with a master chemical mechanism, Atmos. Environ., 32, 2429–2441, 1998. Ehhalt, D H.: Gas phase chemistry of the troposphere, in Global Aspects of Atmospheric Chemistry, in: Topics Phys. Chem., Vol 6, edited by: Zellner, R., Springer-Verlag, New York, 21–109, 1999. Endresen, O., Sørgard, E., Sundet, J K., Dalsøren, S B., Isaksen, I. S A., Berglen, T F., and Gravir, G.: Emissions from international sea transport and environmental impact, J. Geophys Res., 108, 4560, doi:10.1029/2002JD002898, 2003. Fan, J. and Zhang, R.: Atmospheric oxidation scheme of isoprene, Environ. Chem., 1, 140–149, 2004. Feck, T., Grooß, J.-U., and Riese, M.: Sensitivity of Arctic ozone loss to stratospheric H<sub>2</sub>O, Geophys. Res. Lett., 35, L01803, doi:10.1029/2007GL031334, 2008. Feilberg, K L., Johnson, M S., and Nielsen, C J.: Relative reaction rates of HCHO, HCDO, DCDO, H$^13$CHO, and HCH$^18$O with OH, Cl, Br, and NO<sub>3</sub> radicals, J. Phys. Chem. A, 108, 7393–7398, 2004. Feilberg, K L., D'Anna, B., Johnson, M S., and Nielsen, C J.: Relative tropospheric photolysis rates of HCHO, H$^13$CHO, HCH$^18$O, and DCDO measured at the European photoreactor facility (EUPHORE), J. Phys. Chem. A, 109, 8314–8319, 2005. Feilberg, K L., D'Anna, B., Johnson, M S., and Nielsen, C J.: Relative tropospheric photolysis rates of HCHO, H$^13$CHO, HCH$^18$O, and DCDO measured at the European photoreactor facility (EUPHORE), J. Phys. Chem. A, 111, 992, 2007a. Feilberg, K L., Johnson, M S., Bacak, A., Röckmann, T., and Nielsen, C J.: Relative tropospheric photolysis rates of HCHO and HCDO measured at the European photoreactor facility, J. Phys. Chem. A, 111, 9034–9036, 2007b. Feria, L., Gonzalez, C., and Castro, M.: Ab initio study of the CH<sub>3</sub>O<sub>2</sub> self-reaction in gas phase: Elucidation of the CH<sub>3</sub>O<sub>2</sub>+CH<sub>3</sub>O<sub>2</sub> → 2CH<sub>3</sub>O+O<sub>2</sub> pathway, Int. J. Quant. Chem., 99, 605–615, 2004. Gerst, S. and Quay, P.: The deuterium content of atmospheric molecular hydrogen: Method and initial measurements, J. Geophys. Res., 105, 26433–26445, 2000. Gerst, S. and Quay, P.: Deuterium component of the global molecular hydrogen cycle, J. Geophys. Res., 106, 5021–5031, 2001. Gery, M W., Whitten, G Z., Killus, J P., and Dodge, M C.: A photochemical kinetics mechanism for urban and regional scale computer modeling, J. Geophys. Res., 94, 12925–12956, 1989. Grotheer, H H., Riekert, G., Walter, D., and Just, T.: Non-Arrhenius Behavior of the Reaction of Hydroxymethyl Radicals with Molecular Oxygen, J. Phys. Chem., 92, 4028–4030, 1988. Hauglustaine, D A. and Ehhalt, D H.: A three-dimensional model of molecular hydrogen in the troposphere, J. Geophys. Res., 107(D17), 4330, doi:10.1029/2001JD001156, 2002. Henon, E., Bohr, F., Chakir, A., and Brion, J.: Theoretical study of the methyl peroxy self-reaction: the intermediate structure, Chem. Phys. Lett., 264, 557–564, 1997. Hess, W P. and Tully, F P.: Hydrogen-Atom Abstraction from Methanol by OH, J. Phys. Chem., 93, 1944–1947, 1989. Houweling, S., Dentener, F., and Lelieveld, J.: The impact of non-methane hydrocarbon compounds on tropospheric photochemistry, J. Geophys. Res., 103, 10673–10696, 1998. Jenkin, M. E., Saunders, S. M., Wagner, V., and Pilling, M. J.: Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part~B): tropospheric degradation of aromatic volatile organic compounds, Atmos. Chem. Phys., 3, 181–193, 2003. Jiménez, E., Gilles, M K., and Ravishankara, A R.: Kinetics of the reactions of the hydroxyl radical with CH<sub>3</sub>OH and C<sub>2</sub>H$_5$OH between 235 and 360 K, J. Photochem. Photobiol. A: Chemistry, 157, 237–245, 2003. JMA and NASA-WFF: World Ozone and Ultraviolet Radiation Data Centre (WOUDC) [Data], http://www.woudc.org, Retrieved: 2 December 2008. Karunanandan, R., Hö1lscher, D., Dillon, T J., Horowitz, A., and Crowley, J N.: Reaction of HO with Glycolaldehyde, HOCH<sub>2</sub>CHO: Rate Coefficients (240-362 K) and Mechanism, J. Phys. Chem. A, 111, 897–908, 2007. Krol, M., Houweling, S., Bregman, B., van den Broek, M., Segers, A., van Velthoven, P., Peters, W., Dentener, F., and Bergamaschi, P.: The two-way nested global chemistry-transport zoom model TM5: algorithm and applications, Atmos. Chem. Phys., 5, 417–432, 2005. Kwok, E. and Atkinson, R.: Estimation of hydroxyl radical reaction rate constants for gas-phase organic compounds using a structure-reactivity relationship: An update, Atmos. Environ., 29, 1685–1695, 1995. Lathière, J., Hauglustaine, D A., De~Noblet-Ducoudré, N., Krinner, G., and Folberth, G A.: Past and future changes in biogenic volatile organic compound emissions simulated with a global dynamic vegetation model, Geophys. Res. Lett., 32, L20818, doi:10.1029/2005GL024164, 2005. Lathière, J., Hauglustaine, D. A., Friend, A. D., De Noblet-Ducoudré, N., Viovy, N., and Folberth, G. A.: Impact of climate variability and land use changes on global biogenic volatile organic compound emissions, Atmos. Chem. Phys., 6, 2129–2146, 2006. Levin, I., Bergamaschi~P., Dörr, H., and Trapp, D.: Stable isotopic signature of methane from major sources in Germany, Chemosphere, 26, 161–177, 1993. Lightfoot, P D., Cox, R A., Crowley, J N., Destriau, M., Hayman, G D., Jenkin, M E., K., M G., and Zabel, F.: Organic peroxy radicals: kinetics, spectroscopy and tropospheric chemistry, Atmos. Environ., 26A, 1805–1961, 1992. Mar, K A., McCarthy, M C., Connell, P., and Boering, K A.: Modeling the photochemical origins of the extreme deuterium enrichment in stratospheric H<sub>2</sub>, J. Geophys. Res., 112, D19302, doi:10.1029/2006JD007403, 2007. McCaulley, J A., Kelly, N., Golde, M F., and Kaufman, F.: Kinetic Studies of the Reactions of F and OH with CH<sub>3</sub>OH, J. Phys. Chem., 93, 1014–1018, 1989. McGillen, M R., Crosier, J C., Percival, C J., Sanchez-Rayna, G., and Shallcross, D E.: Can topological indices be used to predict gas-phase rate coefficients of importance to tropospheric chemistry? Reactions of alkenes with OH, NO<sub>3</sub> and O<sub>3</sub>, Chemosphere, 65, 2035–2044, 2006a. McGillen, M R., Percival, C J., Raventos-Duran, T., Sanchez-Rayna, G., and Shallcross, D E.: Can topological indices be used to predict gas-phase rate coefficients of importance to tropospheric chemistry? Free radical abstraction reactions of alkanes, Atmos. Environ., 40, 2488–2500, 2006b. McGillen, M. R., Percival, C. J., Pieterse, G., Watson, L. A., and Shallcross, D. E.: Predicting arene rate coefficients with respect to hydroxyl and other free radicals in the gas-phase: a simple and effective method using a single topological descriptor, Atmos. Chem. Phys., 7, 3559–3569, 2007. Minato, T., Yamabe, S., Fujimoto, H., and Fukui, K.: A molecular-orbital calculation of chemically-interacting systems. Interaction between two radicals. Self-reaction of peroxyl radicals, Bull. Chem. Soc. Jpn., 51, 682–689, 1978. Nesbitt, F L., Payne, W A., and Stief, L J.: Temperature dependence for the absolute rate constant for the reaction CH<sub>2</sub>OH+O<sub>2</sub> → HO<sub>2</sub>+H<sub>2</sub>CO from 215 K to 300 K, J. Phys. Chem., 92, 4030–4032, 1988. Niki, H., Maker, P D., M., S C., and Breitenbach, L P.: An FTIR study of mechanisms for the HO radical initiated oxidation of C<sub>2</sub>H<sub>4</sub> in the presence of NO: Detection of glycolaldehyde, Chem. Phys. Lett., 80, 499–503, 1981. Nilsson, E. J. K., Johnson, M. S., Taketani, F., Matsumi, Y., Hurley, M. D., and Wallington, T. J.: Atmospheric deuterium fractionation: HCHO and HCDO yields in the CH<sub>2</sub>DO+O<sub>2</sub> reaction, Atmos. Chem. Phys., 7, 5873–5881, 2007. Novelli, P C., Lang, P M., Masarie, K A., Hurst, D F., Myers, R., and Elkins, J W.: Molecular hydrogen in the troposphere: Global distribution and budget, J. Geophys. Res., 104, 30427–30444, 1999. Olivella, S., Bofill, J M., and Soé, A.: Ab Initio Calculations on the Mechanism of the Oxidation of the Hydroxymethyl Radical by Molecular Oxygen in the Gas Phase: A Significant Reaction for Environmental Science, Chem. Eur. J., 7, 3377–3386, 2001. Orlando, J J., Tyndall, G S., Bilde, M., Ferronato, C., Wallington, T J., Vereecken, L., and Peeters, J.: Laboratory and Theoretical Study of the Oxy Radicals in the OH- and Cl-Initiated Oxidation of Ethene, J. Phys. Chem. A, 102, 8116–8123, 1998. Pöschl, U., Kuhlmann, R v., Poisson, N., and Crutzen, P J.: Development and intercomparison of condensed isoprene oxidation mechanisms for global atmospheric modeling, J. Atmos. Chem., 37, 29–52, 2000. Press, W., Teukolsky, S., Vetterling, W., and Flannery, B.: Numerical Recipes in C, Cambridge University Press, 2nd Edn., 1992. Price, H., Jaeglé, L., Rice, A., Quay, P., Novelli, P C., and Gammon, R.: Global budget of molecular hydrogen and its deuterium content: Constraints from ground station, cruise, and aircraft observations, J. Geophys. Res., 112, D22108, doi:10.1029/2006JD008152, 2007. Rahn, T., Kitchen, N., and Eiler, J M.: D/H ratios of atmospheric H<sub>2</sub> in urban air: Results using new methods for analysis of nano-molar H<sub>2</sub> samples, Geochim. Cosmochim. Acta, 66, 2475–2481, 2002b. Rahn, T., Eiler, J M., Boering, K A., Wennberg, P O., McCarthy, M C., Tyler, S., Schauffler, S., Donnelly, S., and Atlas, E.: Extreme deuterium enrichment in stratospheric hydrogen and the global atmospheric budget of H<sub>2</sub>, Nature, 424, 918–921, 2003. Ravishankara, A R.: Kinetics of radical reactions in the atmospheric oxidation of CH<sub>4</sub>, Ann. Rev. Phys. Chem., 39, 367–394, 1988. Rhee, T S., Mak, J E., Brenninkmeijer, C. A M., and Röckmann, T.: Continuous-flow isotope analysis of the D/H ratio in atmospheric hydrogen, Rap. Commun. Mass Spectrom., 18, 299–306, 2004. Rhee, T S., Brenninkmeijer, C. A M., Brass, M., and Bruhl, C.: Isotopic composition of H<sub>2</sub> from CH<sub>4</sub> oxidation in the stratosphere and the troposphere, J. Geophys. Res., 111, D23303, doi:10.1029/2005JD006760, 2006a. Rhee, T. S., Brenninkmeijer, C. A. M., and Röckmann, T.: The overwhelming role of soils in the global atmospheric hydrogen cycle, Atmos. Chem. Phys., 6, 1611–1625, 2006b. Rhee, T. S., Brenninkmeijer, C. A. M., and Röckmann, T.: Hydrogen isotope fractionation in the photolysis of formaldehyde, Atmos. Chem. Phys., 8, 1353–1366, 2008. Rice, A L. and Quay, P D.: Isotopic analysis of atmospheric formaldehyde by gas chromatography isotope ratio mass spectrometry, Anal. Chem., 78, 6320–6326, 2006. Röckmann, T., Rhee, T. S., and Engel, A.: Heavy hydrogen in the stratosphere, Atmos. Chem. Phys., 3, 2015–2023, 2003. Sander, S P., Finlayson-Pitts, B J., Friedl, R R., Golden, D M., Huie, R E., Keller-Rudek, H., Kolb, C E., Kurylo, M J., Molina, M J., Moortgat, G K., Orkin, V L., R., R A., and Wine, P H.: Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies, Evaluation Number 15, Tech. rep., JPL Publication 06-2, Jet Propulsion Laboratory, Pasadena, 2006. Sanderson, M G., Collins, W J., Derwent, R G., and Johnson, C E.: Simulation of global hydrogen levels using a lagrangian threedimensional model, J. Atmos. Chem., 46, 15–28, 2003. Saueressig, G., Bergamaschi, P., Crowley, J N., Fischer, H., and Harris, G W.: D/H kinetic isotope effect in the reaction CH<sub>4</sub> + Cl, Geophys. Res. Lett., 23, 3619–3622, 1996. Saueressig, G., Crowley, J N., Bergamaschi, P., Brühl, C., Brenninkmeijer, C. A M., and Fischer, H.: $^13$C and D kinetic isotope effects in the reactions of CH<sub>4</sub> with O$^1$D and OH: New laboratory measurements and their implications for the isotopic composition of stratospheric methane, J. Geophys. Res., 106, 23127–23138, 2001. Saunders, S M., Jenkin, M E., Derwent, R G., and Pilling, M J.: World wide Web site of a master chemical mechanism (MCM) for use in tropospheric chemistry models, Atmos. Environ., 31, 1249, http://mcm.leeds.ac.uk/MCM/, 1997. Saunders, S. M., Jenkin, M. E., Derwent, R. G., and Pilling, M. J.: Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part A): tropospheric degradation of non-aromatic volatile organic compounds, Atmos. Chem. Phys., 3, 161–180, 2003. Schocker, A., Uetake, M., Kanno, N., Koshi, M., and Tonokura, K.: Kinetics and Rate Constants of the Reaction CH<sub>2</sub>OH+O<sub>2</sub>→CH<sub>2</sub>O+HO<sub>2</sub> in the Temperature Range of 236–600 K, J. Phys. Chem. A, 111, 6622–6627, 2007. Schultz, M G., Diehl, T., Brasseur, G P., and Zittel, W.: Air pollution and climate-forcing impacts of a global hydrogen economy, Science, 302, 624–627, 2003. Tromp, T K., Shia, R.-L., Allen, M., Eiler, J M., and Yung, Y L.: Potential Environmental Impact of a Hydrogen Economy on the Stratosphere, Science, 300, 1740–1742, 2003. Tyndall, G S., Wallington, T J., and Ball, J C.: FTIR Product Study of the Reactions CH<sub>3</sub>O<sub>2</sub>+CH<sub>3</sub>O<sub>2</sub> and CH<sub>3</sub>O<sub>2</sub>+O<sub>3</sub>, J. Phys. Chem. A, 102, 2547–2254, 1998. Tyndall, G S., Cox, R A., Granier, C., Lesclaux, R., Moortgat, G K., Pilling, M J., Ravishankara, A R., and Wallington, T J.: Atmospheric chemistry of small organic peroxy radicals, J. Geophys. Res., 106, 12157–12182, 2001. van~der Werf, G R., Randerson, J T., Collatz, G J., and Giglio, L.: Carbon emissions from fires in tropical and subtropical ecosystems, Global Change Biol., 9, 547–562, 2003. Venn, J.: On the Diagrammatic and Mechanical Representation of Propositions and Reasonings, Dublin Philosophical Magazine J. Sci., 9, 1–18, 1880. Warwick, N J., Bekki, S., Nisbet, E G., and Pyle, J A.: Impact of a hydrogen economy on the stratosphere and troposphere studied in a 2D model, Geophys. Res. Lett., 31, L05107, doi:10.1029/2003GL019224, 2004. Weaver, J., Meagher, J., R., S., and Heicklen, J.: The oxidation of acetyl radicals, J. Photochem., 4, 341–360, 1975. Zahn, A., Franz, P., Bechtel, C., Grooß, J.-U., and Röckmann, T.: Modelling the budget of middle atmospheric water vapour isotopes, Atmos. Chem. Phys., 6, 2073–2090, 2006.