HR: 15:04h
AN: A23D-07    [Abstracts]
TI: Characterization and Atmospheric Processing of Soot Aerosols in the Mexico City Metropolitan Area
AU: * Johnson, K S
EM: kirstenj@mit.edu
AF: Departments of Earth, Atmospheric and Planetary Sciences and of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139
AU: Zuberi, B
AF: Departments of Earth, Atmospheric and Planetary Sciences and of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139
AU: Zuberi, B
AF: GEO2 Technologies, 770 Boylston St., Boston, MA 02199
AU: Molina, L T
AF: Departments of Earth, Atmospheric and Planetary Sciences and of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139
AU: Molina, M J
AF: Departments of Earth, Atmospheric and Planetary Sciences and of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139
AU: Laskin, A
AF: William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, POB 999, K8-88, Richland, WA 99352
AU: Cowin, J P
AF: William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, POB 999, K8-88, Richland, WA 99352
AU: Iedema, M J
AF: William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, POB 999, K8-88, Richland, WA 99352
AU: Gaspar, D J
AF: William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, POB 999, K8-88, Richland, WA 99352
AU: Wang, C
AF: William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, POB 999, K8-88, Richland, WA 99352
AB: Chemical composition, particle size, and mixing state are critical in determining the effects of atmospheric aerosol on the environment. There is growing evidence that soot aerosols play a particularly important role in both climate and health, but still relatively little is known of their physical and chemical nature. To investigate the effect of locality and residence time on properties of soot in a polluted urban environment, collections of particles 0.2-2.0 $\mu$m were taken in the Mexico City Metropolitan Area (MCMA) during the MCMA-2003 campaign. Samples were collected using an automated Time-Resolved Aerosol Collector (TRAC) both onboard a mobile laboratory and at stationary sites within the city. Individual particles were analyzed with Computer-Controlled Scanning Electron Microscopy with Energy Dispersed detection of X-rays (CCSEM/EDX), Transmission Electron Microscopy (TEM), and Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS). Our analysis shows that soot is a major component of aerosol in the MCMA, and freshly-emitted soot is rapidly processed, leading to the presence of inorganic species such as ammonium sulfate on the soot surface. While fresh, mixed-traffic tailpipe emissions are almost entirely carbonaceous (consisting of soot aggregate chains and lube-oil components), processed soot particles in the MCMA show evidence of heavy internal mixing. Our analysis also suggests that internal mixing may occur through several possible mechanisms, which require further investigation.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
DE: 0345 Pollution--urban and regional (0305)
DE: 0365 Troposphere--composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting