HR: 0830h
AN: A51F-0743    [PDF]
TI: Mass Accommodation of Gas Phase Species on Octanol as a Function of Relative Humidity; Strange Behavior of Gas Phase Hydrogen Halides
AU: * Davidovits, P
EM: paul.davidovits@bc.edu
AF: Chemistry Department, Boston College, Merkert Chemistry Center, Chestnut Hill, MA 02467
AU: Zhang, H
AF: Chemistry Department, Boston College, Merkert Chemistry Center, Chestnut Hill, MA 02467
AU: Li, Y
AF: Chemistry Department, Boston College, Merkert Chemistry Center, Chestnut Hill, MA 02467
AU: Williams, L R
AF: Center for Aerosol and Cloud Chemistry, Aerodyne Research Inc., 45 Manning Road,, Billerica, MA 01821
AU: Jayne, J T
AF: Center for Aerosol and Cloud Chemistry, Aerodyne Research Inc., 45 Manning Road,, Billerica, MA 01821
AU: Kolb, C E
AF: Center for Aerosol and Cloud Chemistry, Aerodyne Research Inc., 45 Manning Road,, Billerica, MA 01821
AU: Worsnop, D R
AF: Center for Aerosol and Cloud Chemistry, Aerodyne Research Inc., 45 Manning Road,, Billerica, MA 01821
AB: At this point very little is known about the physical and chemical properties of organic aerosols that have been shown to be abundant in many regions of the troposphere. In the work to be discussed, 1-octanol was selected as a surrogate for the hydrophobic oxygenated organic compounds found in such aerosols. Using a droplet train apparatus, the uptake of several organic gas phase species and gas phase HCl, HBr and HI was measured to probe the nature of hydrophobic organic surfaces as a function of relative humidity. These measurements yielded the mass accommodation coefficient (alpha) which is the probability that a gas phase molecule striking the liquid surface, enters the bulk liquid. The measured uptake of the organic gas phase species is in accord with expectations. The uptake increases with decreasing temperature and is independent of relative humidity. On the other hand, the observed uptake of the gas phase acids is highly surprising. In the absence of water vapor, alpha for both HBr and HI is unity, however, alpha for HCl is much smaller on the order 0.015. The values of alpha change dramatically as a function of relative humidity (i.e. the density of water vapor). As the relative humidity increases, the alpha values for HBr and HI decrease and alpha for HCl increases. At a relative humidity of about 50%, alpha for all three species reaches values measured earlier on pure water (alpha between 0.15 and 0.3, depending on temperature). These results are discussed in terms of the nucleation model for mass accommodation and a mechanism is proposed to explain the surprising results related to the uptake of the hydrogen halides.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting