Collaborative Research: The role of interactions between organic components on aerosol hygroscopicity

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This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). The goal of this project is to characterize the impact of mixed organic fractions on the hygroscopicity of aerosol in the presence of inorganic ammonium sulfate. The PIs postulate that the systematic differences in organic-organic interactions will impact the dissolution process during water uptake, activation, and subsequent droplet formation and will modify the ability of compounds to partition to the droplet surface, influencing water uptake and cloud condensation nuclei (CCN) activity. This research will improve predictions of the direct and indirect effects of aerosols on radiative forcing and climate.The hypothesis of this proposal is that changes to the morphology of a system consisting of ammonium sulfate, an organic compound that undergoes liquid-liquid phase separation, and an additional organic compound will depend on the solubility and surface activity of the additional organic compound. As the concentration of the second organic compound is varied, the particles’ morphology will change, causing differences between theoretical and measured hygroscopicity. The PIs propose to characterize the following systems: (1) mixtures of ammonium sulfate and a highly soluble organic compound that is not surface active; (2) mixtures of ammonium sulfate and a surface-active organic compound; and (3) mixtures of ammonium sulfate and a highly surface-active organic compound (surfactant).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.