Complete understanding of the physical and chemical properties of atmospheric aerosol is essential in quantifying their overall effect on Earth’s radiation budget. During relative humidity (RH) changes in the atmosphere, aerosol particles take up or lose water as they try to equilibrate with surrounding water vapor. In certain situations, the ability of an aerosol to reach equilibrium can be inhibited by particle viscosity as water transport becomes limited by condensed phase diffusion. Understanding the mechanisms which govern these diffusion-limited processes and the timescales over which growth or shrinkage of the aerosol occurs is key in predicting aerosol effects on atmospheric processes. We utilize both the aerosol optical trap and the electrodynamic balance – the two most popular single-particle techniques – for precise measurements of aerosol properties over a range of sizes. By performing RH steps with these instruments, water uptake and loss by viscous aerosol can be monitored and quantified when transport is limited by particle phase diffusion. Information on equilibration sizes, timescales and mechanistic behaviors of uptake and loss can be obtained for aqueous organic aerosol. We compare these experimental measurements to mass transport models in order to gain a better overall understanding of water uptake and loss by high viscosity aerosol particles in the atmosphere.

Measuring water uptake and loss in viscous aerosol particles

2019 Fall National Meeting

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