HR: 17:36h
AN: A14A-08    [Abstracts]
TI: Separation of Emitted and Photochemical Formaldehyde in the Mexico City Metropolitan Area using a Statistical Analysis and a New Pair of Gas-phase Tracers
AU: * Garcia, A
EM: agustin@troposfera.atmosfcu.unam.mx
AF: Departments of Earth, Atmospheric and Planetary Sciences and of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139 United States
AU: * Garcia, A
EM: agustin@troposfera.atmosfcu.unam.mx
AF: Ciencias de la Atm¢sfera, Universidad Nacional Aut¢noma de M‚xico, Ciudad Universitaria, Delegaci¢n Coyoac n, Mexico City, 04510 Mexico
AU: Volkamer, R
AF: Departments of Earth, Atmospheric and Planetary Sciences and of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139 United States
AU: Molina, L T
EM: ltmolina@mit.edu
AF: Departments of Earth, Atmospheric and Planetary Sciences and of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139 United States
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 United States
AU: Samuelsson, J
AF: Department of Radio and Space Science, Chalmers University of Technology, SE, G™TEBORG, 41296 Sweden
AU: Mellqvist, J
AF: Department of Radio and Space Science, Chalmers University of Technology, SE, G™TEBORG, 41296 Sweden
AU: Galle, B
AF: Department of Radio and Space Science, Chalmers University of Technology, SE, G™TEBORG, 41296 Sweden
AU: Herndon, S
AF: Aerodyne Research, Inc., 45 Manning Road, Billerica, MA 01821 United States
AU: Kolb, C E
AF: Aerodyne Research, Inc., 45 Manning Road, Billerica, MA 01821 United States
AB: In urban air, the presence of formaldehyde (HCHO) is the result of direct emissions from mobile sources (primary HCHO) and of its production by photochemical oxidation of volatile organic compounds (VOC) in the atmosphere (secondary HCHO). HCHO is a known carcinogen, and is further capable to jump-start photochemical smog formation. Pollution control strategies require deconvolution of the amounts of HCHO formed from primary and secondary sources. To separate primary, secondary and background HCHO, a statistical regression analysis of the time series of HCHO from pairs of gas-phase tracer molecules was undertaken. Carbon monoxide (CO) was used as tracer for primary sources; Two different species were compared as tracers for secondary HCHO: glyoxal (CHOCHO) and ozone (O3). These time series were measured at the field campaign supersite located at the National Center for Environmental Research and Training (CENICA) in the Mexico City Metropolitan Area during the MCMA-2003 campaign. In addition, background HCHO measurements were performed outside the city. Correlation coefficients were highest for the CHOCHO-CO tracer pair, indicating that CHOCHO is a better tracer for secondary sources than O3, used previously for this purpose. Results of the analysis are presented for the pre-Easter, Easter week and post-Easter periods. Further, the effect of temperature on the primary and secondary HCHO sources is assessed. On a 24-hour average basis, secondary sources dominate over primary sources. However, during sunrise, when HCHO acts as a radical source to jump-start photochemistry, a significant amount of the HCHO is associated with primary emissions.
DE: 0317 Chemical kinetic and photochemical properties
DE: 0345 Pollution--urban and regional (0305)
DE: 0365 Troposphere--composition and chemistry
DE: 0368 Troposphere--constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting