10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Clustering of Sulfuric Acid, Bisulfate Ion and Organonitrate C10H15O10N: Thermodynamics and Atmospheric Implications
JASON HERB, Alexey Nadykto, Kirill Nazarenko, Nikolai Korobov, Fangqun Yu, SUNY at Albany
Abstract Number: 1025 Working Group: Aerosol Chemistry
Abstract Recently, Highly Oxidized Molecules (HOMs) have been suggested to play an important role in New Particle Formation (NPF) in the atmosphere. Although stable clusters containing organonitrates (ONs), a common form of HOM containing nitrogen in addition to carbon, hydrogen and oxygen, and neutral and negatively charged sulfuric acid molecules have been detected in both laboratory experiments under atmospherically relevant conditions and in-situ measurements, the role of ONs in their stability is still poorly understood. In this study, we seek to advance the understanding of the role of ONs in atmospheric NPF by carrying out a Density Functional Theory (DFT) study of the bonding of a selected C10H15O10N organonitrate, N-[2-(1,2-Dicarboxyethoxy)ethyl]-3-hydroxyaspartic acid with H2SO4 and bisulfate ion HSO4-. The present analysis reveals an important role of the C10H15O10N in the enhanced stability of both ionic and neutral clusters as all the mixed dimers, trimers and tetramers containing C10H15O10N are found to be more stable compared to pure ones. The substitution of the H2SO4 molecule with the ON is particularly favorable in the case of negative ions, when the stepwise Gibbs free energy increases by up to ~9 kcal mol-1 per step due to the presence of the ON. In particular, the free energies of the formation of (H2SO4)n-1(ON)(HSO4-) and (H2SO4)n(HSO4-) via the addition of H2SO4 differ by 0.7, 5.45 and 9.2 kcal mol-1 at n=2, 3 and 4, respectively, in the favor of (H2SO4)n-1(ON)(HSO4-) clusters. The effect of the C10H15O10N on clustering of H2SO4 molecules under is smaller, but still considerable as evidenced by ~ 0.7-2 kcal mol-1 difference in the formation free energies, also in the favor of ON-containing clusters. This indicates that the C10H15O10N is capable of facilitating the production of fairly large sulfuric acid clusters and may promote in this way atmospheric NPF under favorable conditions.