Viscosity of α -pinene secondary organic material and implications for particle growth and reactivity
- 25 April 2013
- journal article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences of the United States of America
- Vol. 110 (20), 8014-8019
- https://doi.org/10.1073/pnas.1219548110
Abstract
Particles composed of secondary organic material (SOM) are abundant in the lower troposphere. The viscosity of these particles is a fundamental property that is presently poorly quantified yet required for accurate modeling of their formation, growth, evaporation, and environmental impacts. Using two unique techniques, namely a "bead-mobility" technique and a "poke-flow" technique, in conjunction with simulations of fluid flow, the viscosity of the water-soluble component of SOM produced by α-pinene ozonolysis is quantified for 20- to 50-μm particles at 293-295 K. The viscosity is comparable to that of honey at 90% relative humidity (RH), similar to that of peanut butter at 70% RH, and at least as viscous as bitumen at ≤30% RH, implying that the studied SOM ranges from liquid to semisolid or solid across the range of atmospheric RH. These data combined with simple calculations or previous modeling studies are used to show the following: (i) the growth of SOM by the exchange of organic molecules between gas and particle may be confined to the surface region of the particles for RH ≤ 30%; (ii) at ≤30% RH, the particle-mass concentrations of semivolatile and low-volatility organic compounds may be overpredicted by an order of magnitude if instantaneous equilibrium partitioning is assumed in the bulk of SOM particles; and (iii) the diffusivity of semireactive atmospheric oxidants such as ozone may decrease by two to five orders of magnitude for a drop in RH from 90% to 30%. These findings have possible consequences for predictions of air quality, visibility, and climate.Keywords
This publication has 51 references indexed in Scilit:
- Technical Note: New methodology for measuring viscosities in small volumes characteristic of environmental chamber particle samplesAtmospheric Chemistry and Physics, 2013
- Phase of atmospheric secondary organic material affects its reactivityProceedings of the National Academy of Sciences of the United States of America, 2012
- Comparing the mechanism of water condensation and evaporation in glassy aerosolProceedings of the National Academy of Sciences of the United States of America, 2012
- Nonequilibrium atmospheric secondary organic aerosol formation and growthProceedings of the National Academy of Sciences of the United States of America, 2012
- Gas uptake and chemical aging of semisolid organic aerosol particlesProceedings of the National Academy of Sciences of the United States of America, 2011
- The role of long-lived reactive oxygen intermediates in the reaction of ozone with aerosol particlesNature Chemistry, 2011
- Evaporation kinetics and phase of laboratory and ambient secondary organic aerosolProceedings of the National Academy of Sciences of the United States of America, 2011
- Morphology of mixed primary and secondary organic particles and the adsorption of spectator organic gases during aerosol formationProceedings of the National Academy of Sciences of the United States of America, 2010
- Hygroscopic properties of aerosol formed by oxidation of limonene, α‐pinene, and β‐pinenePublished by American Geophysical Union (AGU) ,1999
- Modeling the Mass Transfer of Semivolatile Organics in Combustion AerosolsEnvironmental Science & Technology, 1994