HR: 13:40h
AN: A43E-01 INVITED    [Abstracts]
TI: The Formation and Growth of Atmospheric Aerosols: Recent Results from MILAGRO
AU: * Smith, J N
EM: jimsmith@ucar.edu
AF: National Center for Atmospheric Research, 1850 Table Mesa Dr., Boulder, CO 80305, United States
AU: Dunn, M
EM: mattdunn@ucar.edu
AF: National Center for Atmospheric Research, 1850 Table Mesa Dr., Boulder, CO 80305, United States
AU: Eisele, F L
EM: eisele@ucar.edu
AF: National Center for Atmospheric Research, 1850 Table Mesa Dr., Boulder, CO 80305, United States
AU: VanReken, T M
EM: vanreken@wsu.edu
AF: Washington State University, P.O. Box 642910, Pullman, WA 99164, United States
AU: Iida, K
EM: iida@me.umn.edu
AF: University of Minnesota, 111 Church Street S.E., Minneapolis, MN 55455, United States
AU: Kuang, C
EM: kuang@cems.umn.edu
AF: University of Minnesota, 111 Church Street S.E., Minneapolis, MN 55455, United States
AU: McMurry, P H
EM: mcmurry@me.umn.edu
AF: University of Minnesota, 111 Church Street S.E., Minneapolis, MN 55455, United States
AU: Stolzenburg, M R
EM: mstolz@me.umn.edu
AF: University of Minnesota, 111 Church Street S.E., Minneapolis, MN 55455, United States
AB: In March, 2006, a team of researchers from NCAR and the University of Minnesota carried out measurements pertinent to new particle formation and growth at the T1 ground-based site in Tecamac, Mexico, as part of the MILAGRO field campaign. Our goal was to understand the processes by which new particles form and grow in the polluted outflow of a megacity. Several important results have emerged from these measurements and the ensuing analyses. New particle formation and subsequent condensational growth occurred frequently outside of Mexico City, and were often the dominant processes affecting number concentrations in that area. Nucleation rates calculated from our measurements were found to have a squared dependence on sulfuric acid vapor concentrations, which is consistent with observations from diverse atmospheric environments including Boulder, Atlanta, Mauna Loa, and Idaho Hill (Rocky Mountains). Nucleation was dominated by neutral cluster formation, with ion-induced nucleation playing a relatively minor role. Finally, newly formed, sub-10 nm particles were composed of a complex mix of chemical compounds, with nitrate and organics appearing as the dominant species following strong new particle formation events while sulfate compounds remained relatively constant. This new information on nanoparticle composition is key to understanding why the growth rates of freshly nucleated particles are often significantly higher than can be explained by the condensation of sulfuric acid alone.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting