A dual-droplet approach for measuring the hygroscopicity of aqueous aerosol
| Autor: | Craig S. Sheldon, Ravleen Kaur Kohli, Chelsea L. Price, Jack Choczynski, James F. Davies |
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| Rok vydání: | 2021 |
| Předmět: |
Atmospheric Science
Ammonium sulfate Range (particle radiation) Aqueous solution Materials science 010504 meteorology & atmospheric sciences Water activity Vapor pressure TA715-787 Analytical chemistry Environmental engineering TA170-171 010402 general chemistry 01 natural sciences 0104 chemical sciences Aerosol chemistry.chemical_compound Viscosity Earthwork. Foundations chemistry Relative humidity 0105 earth and related environmental sciences |
| Zdroj: | Atmospheric Measurement Techniques, Vol 14, Pp 5001-5013 (2021) |
| ISSN: | 1867-8548 |
| Popis: | Accurate characterization of the water activity and hygroscopicity of aqueous aerosol material allows us to predict the chemical and physical state of aerosol particles exposed to humid conditions in the environment. The hygroscopicity of aerosol determines the size, phase morphology, viscosity, chemical reactivity, and optical properties of constituent particles and directly impacts their ability to form clouds in the atmosphere. In this work, we describe measurements of hygroscopicity using a linear quadrupole electrodynamic balance (LQ-EDB). We levitate two droplets, one droplet that acts as a relative humidity (RH) probe and one sample droplet, and expose them to controlled environmental conditions. We describe the development of an RH measurement using probe droplets of aqueous NaCl or LiCl, allowing for precise in situ measurements of RH in the LQ-EDB chamber. We demonstrate that the RH may be determined with an accuracy of 0.5 % at 50 % RH and better than 0.1 % at 90 % RH using NaCl, and we show that LiCl is effective at characterizing the RH from ∼ 10 % RH up to ∼ 90 %. We simultaneously measure the response of sample droplets containing aqueous material (including ammonium sulfate, citric acid, 1,2,6-hexanetriol, and tetra-ethylene glycol) and report hygroscopic growth via their radial growth factors. We use established thermodynamic models to validate the accuracy of the RH probe and to compare with the measured hygroscopicity of the samples. This approach shows significant advantages over other methods for accurately characterizing the hygroscopicity of samples with a range of characteristics, such as high viscosity and vapor pressure. |
| Databáze: | OpenAIRE |
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