Liquid-Liquid Phase Separation (LLPS) Can Drive Aerosol Droplet Growth in Supersaturated Regimes
Kotiba A. Malek, Kanishk Gohil, Esther Olonimoyo, Nahin Ferdousi, Qishen Huang, Kiran R. Pitta, Lucy Nandy, Katelyn Voss, Tim Raymond, Dabrina Dutcher, Miriam Freedman, AKUA ASA-AWUKU,
University of Maryland, College Park Abstract Number: 681
Working Group: Aerosols, Clouds and Climate
AbstractThe atmospheric aerosol composition is typically a mixture and consists of a wide range of organic and inorganic particles that interact with each other. Furthermore, water-vapor is ubiquitous in the atmosphere and the presence of water can alter the aerosol morphology and propensity to form droplets. Specifically, aerosol mixtures can undergo liquid-liquid phase separation (LLPS) in the presence of water-vapor. However, the experimental conditions for which LLPS impacts water uptake and the subsequent prediction of aerosol mixtures is poorly understood. To improve our understanding of aerosol mixtures and droplets, this study explores two ternary systems that undergo LLPS, namely the 2MGA system (sucrose + ammonium sulfate + 2-methylglutaric acid) and the PEG1000 system (sucrose + ammonium sulfate + polyethylene glycol 1000). In this study, the ratio of species and the O:C ratios are systematically changed, and the hygroscopic properties of the resultant aerosol were investigated. Here we show that the droplet activation above 100% RH of the 2MGA system was influenced by LLPS, while the droplet activation of the PEG1000 system was observed to be linearly additive regardless of chemical composition, O:C ratio, and LLPS. A theoretical model that accounts for LLPS with O:C ratios was developed and predicts the water uptake of internally mixed systems of different compositions and phase states. Hence, this study provides a computationally efficient algorithm to account for the LLPS, and solubility parameterized by the O:C ratio for droplet activation at supersaturated relative humidity conditions and may thus be extended to mixed inorganic-organic aerosol populations with unspeciated organic composition found in the ambient environment.