ONIOM QM/MM investigation of iodide oxidation by ozone on an aqueous particle
- 1Laboratory of Environmental Chemistry, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
- 2Univ. Lille, CNRS, UMR 8523 - PhLAM - Physique des Lasers Atomes et Molécules, F-59000 Lille, France
- 3Department of Chemistry & Cooperative Institute for Research on Environmental Sciences (CIRES), University of Colorado, Boulder, USA
Recently, Koenig et al. [1] measured both gas phase iodine species and particulate iodine (iodate and iodide) in the lower stratosphere indicating that tropospheric multiphase redox reactions prevent poorly soluble gaseous iodine species from removal by wet deposition leading to injections of inorganic iodine into the lower stratosphere. This may influence stratospheric ozone depletion both indirectly through activation of iodide to molecular halogens and directly through the aqueous phase reaction of ozone (O3) with iodide [2]. The product of this reaction, IO-, is reacting with I- to I2(g) under most circumstances. Sakamoto et al. [3] have suggested that in addition IO(g) may be formed. The primary reaction of iodide with O3 depends on pH. Solute strength effects and the extent of a surface reaction have not been sufficiently established [3,4].
An hybrid ONIOM QM/MM method [5] has been used to investigate the reactivity of ozone on a iodide-containing slab of water. The reaction pathway has been determined both at the interface and in the bulk aqueous phase. Both singlet and triplet state surfaces are investigated as the triplet state can be reached through photoexcitation of ozone or by spin state change along the reaction coordinate. These theoretical calculations provide insight into the uptake process at the molecular scale. Comparisons with experimental measurements performed using a trough reactor [6] coupled to Cavity Enhanced – Differential Optical Absorption Spectroscopy (CE-DOAS) [7,8] are also discussed.
References
[1] T. K. Koenig et al., PNAS, 117, 4 (2020).
[2] L. J. Carpenter et al., Nat. Geosci., 6 (2013).
[3] Y. Sakamoto et al., J. Phys. Chem. A, 113, 27 (2009).
[4] C. Moreno et al., Phys. Chem. Chem. Phys., 22 (2020)
[5] L. W. Chung et al., Chem. Rev., 115, 12 (2015)
[6] L. Artiglia et al., Nat. Commun., 8 (2017)
[7] M. Wang et al., Atmos. Meas. Tech., 14, (2021).
[8] R. Thalman and R. Volkamer, Atmos. Meas. Tech., 3, (2010).
How to cite: Roose, A., Toubin, C., Réal, F., Finkenzeller, H., Volkamer, R., Ammann, M., and Vallet, V.: ONIOM QM/MM investigation of iodide oxidation by ozone on an aqueous particle, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4762, https://doi.org/10.5194/egusphere-egu22-4762, 2022.
