CHOUAIB Zahraa: Theoretical Investigation of the Surface Activity and Reactivity of Organosulfate Aerosols

Thesis summary: The environmental impacts of atmospheric compounds are of great interest to scientists, the general public, and policy makers. Among these, sulfur compounds are an important component of atmospheric aerosols and cloud droplets. The health and climate effects of inorganic sulfur compounds such as sulfates are well-documented. On the other hand, the fates and environmental impacts of organosulfur compounds, which can have very different properties and toxicity from their inorganic counterparts, are relatively unknown. Among these, organosulfates (OSs) as a type of major organosulfur compounds, can potentially play an important role in determining the properties of both aerosols and droplets(1). It is thus crucial to better understand these OSs. To date, even though their formation mechanisms have become better understood, their transformation pathways remain largely unexplored. To fill this gap, we propose to investigate by a theoretical approach the heterogeneous reactivity and surface activity of these compounds.
Moreover, when located at the surface of aqueous aerosols, organic molecules can potentially contribute to the formation of cloud condensation nuclei (CCN) and are involved in a series of chemical reactions with gas phase oxidants. Molecular Dynamics simulations will thus be conducted to measure and estimate the surface tension of OSs on aqueous particles. In addition, quantum chemistry calculations will be carried out to estimate the rate of the oxidation reactions in both gas and aqueous phases.

(1) Xu, R., Ge, Y., Kwong, K. C., Poon, H. Y., Wilson, K. R., Yu, J. Z., Chan, M. N.* (2020) “Inorganic Sulfur Species formed upon Heterogeneous OH Oxidation of Organosulfates: A Case Study of Methyl Sulfate”, ACS Earth and Space Chemistry, 4, 2041–2049.

PhD student: CHOUAIB Zahraa - LinkedIn

Thesis supervisors: TOUBIN Céline - DUFLOT Denis