Projects per year
Abstract
Organic aerosol particles are known to often absorb/desorb water continuously with change in gas phase relative humidity (RH) without crystallisation. Indeed, the prevalence of metastable ultraviscous liquid or amorphous phases in aerosol is well-established with solutes often far exceeding bulk phase solubility limits. Particles are expected to become increasingly viscous with drying, a consequence of the plasticising effect of water. We report here measurements of the variation in aerosol particle viscosity with RH (equal to condensed phase water activity) for a range of organic solutes including alcohols (diols to hexols), saccharides (mono-, di- and tri-) and carboxylic acids (di-, tri- and mixtures). Particle viscosities are measured over a wide range (10-3 to 1010 Pa s) using aerosol optical tweezers, inferring the viscosity from the timescale for a composite particle to relax to a perfect sphere following the coalescence of two particles. Aerosol measurements compare well with bulk phase studies (well-within an order of magnitude deviation at worst) over ranges of water activity accessible to both. Predictions of pure component viscosity from group contribution approaches combined with either non-ideal or ideal mixing reproduce the RH-dependent trends particularly well for the alcohol, di- and tri-carboxylic acid systems extending up to viscosities of 104 Pa s. By contrast, predictions over-estimate the viscosity by many orders of magnitude for the mono-, di-, and tri-saccharide systems, components for which the pure component sub-cooled melt viscosities are >>1012 Pa s. When combined with a typical scheme for simulating the oxidation of α-pinene, a typical atmospheric pathway to secondary organic aerosol (SOA), these predictive tools suggest that the pure component viscosities are less than 106 Pa s for ~97% of the 50,000 chemical products included in the scheme. These component viscosities are consistent with the conclusion that the viscosity of α-pinene SOA is most likely in the range 105 to 108 Pa s. Potential improvements to the group contribution predictive tools for pure component viscosities are considered.
Original language | English |
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Pages (from-to) | 8123–8137 |
Number of pages | 5 |
Journal | Journal of Physical Chemistry A |
Volume | 120 |
Issue number | 41 |
Early online date | 29 Sept 2016 |
DOIs | |
Publication status | Published - 20 Oct 2016 |
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Dive into the research topics of 'Measurements and Predictions of Binary Component Aerosol Particle Viscosity'. Together they form a unique fingerprint.Projects
- 2 Finished
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Diffusion and Equilibration in Viscous Atmospheric Aerosol
Reid, J. P. (Principal Investigator)
1/12/14 → 31/03/18
Project: Research
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New Frontiers in Aerosol Measurements
Royall, C. P. (Co-Principal Investigator) & Reid, J. P. (Principal Investigator)
30/03/14 → 29/08/17
Project: Research
Datasets
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Measurements and Predictions of Binary Component Aerosol Particle Viscosity (J Phys Chem A, 2016)
Bzdek, B. (Creator), Haddrell, A. (Creator), Reid, J. (Creator) & Miles, R. (Creator), University of Bristol, 21 Sept 2016
DOI: 10.5523/bris.gelaxwmkbqz91h9t54467wpsw, http://data.bris.ac.uk/data/dataset/gelaxwmkbqz91h9t54467wpsw
Dataset
Profiles
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Dr Bryan R Bzdek
- School of Chemistry - Proleptic Associate Professor
- Cabot Institute for the Environment
Person: Academic , Member
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Professor Jonathan P Reid
- Cabot Institute for the Environment
- School of Chemistry - Professor
- Soft Matter, Colloids and Materials
Person: Academic , Member