HR: 1340h
AN: A43C-0112    [Abstracts]
TI: Determining Ion-Aerosol Nucleation Rates in the Lower Atmosphere: Thermodynamic and Kinetic Modeling and Data Requirements
AU: D'Auria, R
EM: rdauria@uci.edu
AF: University of California Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095-1565 United States
AU: D'Auria, R
EM: rdauria@uci.edu
AF: Univeristy of California Irvine, 315 Rowland Hall, Irvine, CA 92697-2025 United States
AU: * Turco, R P
EM: turco@ucla.edu
AF: University of California Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095-1565 United States
AB: In situ measurements in the free troposphere [Eichkorn et al., 2002] have detected massive positively charged clusters (up to 2500 amu) that appear to be composed of water, acetone and sulfuric acid. Previous modeling studies have suggested that such ionic clusters participate in a number of atmospheric processes, including aerosol formation [Yu and Turco, 1999] and phase transitions in polar stratospheric clouds [D'Auria and Turco, 2001a]. Other work [Lee et al., 2003] indicates that ultrafine particle bursts detected in the upper troposphere can be explained by negative ion clustering mechanisms constrained by laboratory thermodynamic data [Lovejoy et al., 2004], offering further evidence for ion-mediated nucleation. In the lower troposphere, where charged clusters containing hydrated acids, ammonia and a variety of organic compounds are seen, ion-based modeling can often explain nucleation events observed in this region [Yu and Turco, 2001]. We discuss the thermodynamic and kinetic aspects of ion growth and activation in the atmosphere, and describe a "hybrid" representation for common ion families that integrates laboratory measurements with quantum mechanical simulations of charged cluster structure and energetics [D'Auria and Turco, 2001b]. We show that a kinetic model of ion cluster evolution applicable to atmospheric phenomena, including particle nucleation, can be constructed using a hybrid data approach. We present recent results--based on high-level quantum mechanical geometry optimization and thermochemical calculations--for positive ion clusters composed of water, sulfuric acid and acetone [D'Auria, 2005]. It is argued that ions with ternary compositions provide a high degree of cluster stabilization, and are therefore likely to generate pre-condensation nuclei throughout the lower atmosphere. We also discuss errors in the determination of cluster free energies and entropies under atmospheric conditions, and identify the types and precision of data needed to build a comprehensive model of ion-aerosol interactions. References: D'Auria, R.: A Study of Ionic Clusters in the Lower Atmosphere and Their Role in Aerosol Formation. PhD Thesis, University of California, Los Angeles, 2005. D'Auria, R., and R. P. Turco: Ionic clusters in the polar winter stratosphere. GRL 28, 3871, 2001a. D'Auria, R., and R. P. Turco: A thermodynamic-kinetic model for ionic cluster formation, growth and nucleation, Proc. Workshop Ion-Aerosol-Cloud Interactions, ed. J. Kirkby, CERN 2001-007, Geneva, 2001b. D'Auria, R., R. P. Turco and K. Houk: Effects of hydration on the properties of protonated-water-nitric acid clusters. JPC-A 108, 3756, 2004. Eichkorn, S., S. Wilhelm; H. Aufmhoff; K. H. Wohlfrom and F. Arnold: Cosmic ray-induced aerosol-formation: First observational evidence from aircraft-based ion mass spectrometer measurements in the upper troposphere. GRL 29, 43-1, 2002. Lee, S.-H., J. M. Revees, J. C. Wilson, D. E. Hunton, A. A. Viggiano, T. M. Miller, J. O. Ballenthin and L. R. Lait: Particle formation by ion nucleation in the upper troposphere and lower stratosphere. Science 301, 1886, 2003. Lovejoy, E. R., J. Curtius and K. D. Froyd: Atmospheric ion-induced nucleation of sulfuric acid and water. JGR 109, D08204, 2004. Yu, F., and R. P. Turco: Ultrafine aerosol formation via ion-mediated nucleation. GRL 27, 883, 2000. Yu, F., and R. P. Turco: From molecular clusters to nanoparticles: The role of ambient ionization in tropospheric aerosol formation. JGR 106, 4797, 2001.
DE: 0320 Cloud physics and chemistry
DE: 1610 Atmosphere (0315, 0325)
DE: 1650 Solar variability (7537)
DE: 2104 Cosmic rays
DE: 2479 Solar radiation and cosmic ray effects
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005