Abstract View
Exploring Supramolecular Effects on the Viscosity and Phase State of Aqueous Organic-Inorganic Aerosols
RYAN DAVIS, Erik Huynh, Josefina Hajek-Herrera, Trinity University
Abstract Number: 399
Working Group: Aerosol Chemistry
Abstract
The phase state of aqueous organic-inorganic aerosol particles is of interest for, e.g., understanding the aerosol impact on air quality and climate, the transmission of infectious disease through respiratory aerosols, and utilizing aerosols for micro-encapsulation processes. Despite this widespread interest, there remains significant uncertainty about the fundamental processes dictating the viscosity and phase state of aqueous organic-inorganic aerosols. Recently, it was demonstrated that supramolecular interactions between divalent inorganic ions and low-mass oxygenated organic molecules can lead to deviations from bulk expectations of viscosity, and enable humidity-dependent gel transitions in aerosol particles. It remains unclear whether this is a general effect occurring with all divalent ion-oxygenated organic combinations. Here, we discuss new experimental investigations that provides insight into aerosol supramolecular chemistry. Using Ca2+ as the divalent ion with a range of oxygenated organic molecules, we demonstrate that divalent ions can have different effects, dependent on the identity of the organic molecule. We identify three different Ca2+-organic compositions with distinct humidity-dependent outcomes: Ca2+-organic mixtures where gelation or vitrification is not observed, but have an increased viscosity (relative to predictions); mixtures where the viscosity is increased and a gel transition is observed; and mixtures where there is only a minor supramolecular effect (that is, mixtures behave similar to expectations based on bulk predictions). We discuss the underlying chemistry influencing supramolecular effects on aerosol viscosity and phase, and the potential impacts on atmospheric chemistry.