Timescales of water transport in viscous aerosol: measurements on sub-micron particles and dependence on conditioning history

Jessica W. Lu, Andrew M. J. Rickards, Jim S. Walker, Kerry J. Knox, Rachael E. H. Miles, Jonathan P. Reid*, Ruth Signorell

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

57 Citations (Scopus)

Abstract

Evaporation studies of single aqueous sucrose aerosol particles as a function of relative humidity (RH) are presented for coarse and fine mode particles down into the submicron size range (600 nm <r <3.0 mu m). These sucrose particles serve as a proxy for biogenic secondary organic aerosols that have been shown to exist, under ambient conditions, in an ultraviscous glassy state, which can affect the kinetics of water mass transport within the bulk phase and hinder particle response to changes in the gas phase water content. A counter-propagating Bessel beams (CPBBs) optical trapping setup is employed to monitor the realtime change in the particle radius with RH decreasing from 75% to 5%. The slow-down of the size change upon each RH step and the deviation from the theoretical equilibrium hygroscopic growth curve indicate the onset of glassy behavior in the RH range of 10-40%. Size-dependent effects were not observed within the uncertainty of the measurements. The influence of the drying time below the glass transition RH on the timescale of subsequent water condensation and re-equilibration for sucrose particles is explored by optical tweezers measurements of micron-sized particles (3 mu m <r <6 mu m). The timescale for water condensation and re-equilibration is shown to increase with increasing drying time, i.e. the time over which a viscous particle is dried below 5% RH. These studies demonstrate the importance of the history of the particle conditioning on subsequent water condensation and re-equilibration dynamics of ultraviscous and glassy aerosol particles.

Original languageEnglish
Pages (from-to)9819-9830
Number of pages12
JournalPhysical Chemistry Chemical Physics
Volume16
Issue number21
DOIs
Publication statusPublished - 2014

Keywords

  • SECONDARY ORGANIC AEROSOL
  • LOW RELATIVE-HUMIDITY
  • FORCE OPTICAL TRAP
  • ELECTRODYNAMIC BALANCE
  • SUPERCOOLED LIQUIDS
  • GLASS-TRANSITION
  • PHASE
  • EVAPORATION
  • DROPLETS
  • STATE

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