Investigation of the behavior of tropospheric relevant compounds at the interface gas/organic acid aerosols: An ONIOM QM/MM study

International audience; The uptake of atmospheric gaseous oxidant such as O3 or the ROx (OH, HO2, RO2) family, have a strong impact on the oxidative capacity of the atmosphere. [1], [2] Last decade, few studies have been carried out on the uptake of such compounds on atmospheric aerosol. However, the large variety of organic compounds provides uptake coefficients with a wide range of order of magnitude. [3], [4] Furthermore, the uptake resulting from the combination of different processes (mass accommodation, bulk diffusion, reactivity), the detailed understanding of such a process is not always accessible through experiments. Theoretical tools such as quantum mechanics (QM) combined with Molecular Mechanics (MM) is one way to investigate separately the different processes.The ONIOM hybrid QM/MM method [5] allows to study the reactivity of few molecules in a large system. In our group, a methodology using this computational method have been developed in order to estimate the reactive uptake of gaseous compounds onto organic aerosol particles. In this presentation, reactive uptake of HO2 and O3 onto glutaric acid and oleic acid aerosols respectively will be discussed. Comparisons will be addressed with gas phase theoretical reaction rates and with experimental data.We acknowledge support by the French government through the Program “Investissement d'avenir” through the Labex CaPPA (contract ANR-11-LABX-0005-01) and I-SITE ULNE project OVERSEE (contract ANR-16-IDEX-0004), CPER CLIMIBIO (European Regional Development Fund, Hauts de France council, French Ministry of Higher Education and Research) and French national supercomputing facilities (grants DARI x2016081859 and A0050801859). References[1] H. L. Macintyre and M. J. Evans, “Parameterisation and impact of aerosol uptake of HO2 on a global tropospheric model,” Atmos. Chem. Phys., vol. 11, no. 21, pp. 10965–10974, Nov. 2011, doi: 10.5194/acp-11-10965-2011.[2] M. Zeng and K. R. Wilson, “Efficient Coupling of Reaction Pathways of Criegee Intermediates and Free Radicals in the Heterogeneous Ozonolysis of Alkenes,” The Journal of Physical Chemistry Letters, Jul. 2020, doi: 10.1021/acs.jpclett.0c01823.[3] P. S. J. Lakey, I. J. George, L. K. Whalley, M. T. Baeza-Romero, and D. E. Heard, “Measurements of the HO2 Uptake Coefficients onto Single Component Organic Aerosols,” Environ. Sci. Technol., vol. 49, no. 8, pp. 4878–4885, Apr. 2015, doi: 10.1021/acs.est.5b00948.[4] M. Mendez, N. Visez, S. Gosselin, V. Crenn, V. Riffault, and D. Petitprez, “Reactive and Nonreactive Ozone Uptake during Aging of Oleic Acid Particles,” J. Phys. Chem. A, vol. 118, no. 40, pp. 9471–9481, Oct. 2014, doi: 10.1021/jp503572c.[5] L. W. Chung et al., “The ONIOM Method and Its Applications,” Chem. Rev., vol. 115, no. 12, pp. 5678–5796, Jun. 2015, doi: 10.1021/cr5004419.