Abstract View
Pressure Implication in Atmospheric Aerosols: Rate Constant and Product Formation
CLÉMENT DUBOIS, Sebastien Perrier, Yinon Rudich, Sergey Nizkorodov, Frédéric Caupin, Thorsten Hoffmann, Chrisitan George, Matthieu Riva, CNRS-IRCELYON
Abstract Number: 332
Working Group: Aerosol Chemistry
Abstract
Secondary organic aerosols are key players in the atmosphere formed, either by nucleation of low volatile compounds or by heterogeneous reactions occurring onto pre-existing aerosols. The formation and aging of atmospheric aerosols is the object of intense research. Therefore, we decided to focus on one physical aspect not considered in the atmospheric sciences hitherto: the pressure inside nanoparticles. Due to the Young-Laplace law’s, the pressure inside nanometric aerosols can reach hundreds of bars. This pressure can affect chemical reactions, during which the molar volume of products differ from that of reactants. Thus, the pressure could allow the formation of compounds when the reaction mechanisms are favored under pressure. These reactions could aid in the formation and the growth of nanometric particles. To study the impact of the pressure on atmospheric aerosols, we placed aqueous samples containing glyoxal and ammonium sulfate under pressure using a high-reaction vessel. After different exposure times and pressures, the chemical composition of each sample was retrieved using high-resolution mass spectrometry and UV/Vis spectroscopy. The formation of reaction products was shown to be strongly (i.e., up to a factor of 2) slowed down under high pressures, typical of atmospheric nanoparticles. This may indicate that the reactional intermediate temporarily increases the total volume of the reaction, resulting in a decrease of the reaction products formation. To extend the analysis of the reactions under pressure, we developed an experimental system, allowing in-situ characterization of the absorbance of chemical compounds at various pressures. Chemical analyses were also performed using UHPLC-ESI-Orbitrap-MS to determine the chemical composition of the mixtures exposed to different pressures. Using this new system, we studied a large number of chemical mixtures to reveal the impact of pressure on atmospheric relevant systems. The chemical modification and/or a change in the rate constant can help predicting the formation of aerosols.