HR: 15:45h
AN: A23C-05    [Abstracts]
TI: Radical production in the near field chemical regime during MILAGRO
AU: * Volkamer, R M
EM: rainer@alum.mit.edu
AF: Chemistry and Biochemistry, University of California, San Diego, 9500 Gilmann Drive, MC 0356, La Jolla, CA 92093-0356, United States
AU: * Volkamer, R M
EM: rainer@alum.mit.edu
AF: EAPS M.I.T., 77, Massachusetts Ave, Cambridge, MA 02139, United States
AU: Sheehy, P
EM: sheehy@mit.edu
AF: EAPS M.I.T., 77, Massachusetts Ave, Cambridge, MA 02139, United States
AU: Sheehy, P
EM: sheehy@mit.edu
AF: MCE2, 3262 Holiday Ct. Suite 201, La Jolla, CA 92037, United States
AU: Molina, L
EM: ltmolina@mit.edu
AF: EAPS M.I.T., 77, Massachusetts Ave, Cambridge, MA 02139, United States
AU: Molina, L
EM: ltmolina@mit.edu
AF: MCE2, 3262 Holiday Ct. Suite 201, La Jolla, CA 92037, United States
AU: Sinreich, R
EM: roman.sinreich@iup.uni-heidelberg.de
AF: IUP, University of Heidelberg, INF 229, Heidelberg, 69120, Germany
AU: Merten, A
EM: andre.merten@iup.uni-heidelberg.de
AF: IUP, University of Heidelberg, INF 229, Heidelberg, 69120, Germany
AU: Platt, U
EM: ulrich.platt@iup.uni-heidelberg.de
AF: IUP, University of Heidelberg, INF 229, Heidelberg, 69120, Germany
AU: Wagner, T
EM: thomas.wagner@iup.uni-heidelberg.de
AF: IUP, University of Heidelberg, INF 229, Heidelberg, 69120, Germany
AU: Wagner, T
EM: thomas.wagner@iup.uni-heidelberg.de
AF: MPI Chemistry, Otto Hahn Institute, Mainz, ?????, Germany
AB: A detailed analysis of OH, HO₂ and RO₂ radical sources is presented for the near field photochemical regime inside the Mexico City Metropolitan Area. During MILAGRO an extensive set of measurements was collected at T0 (MCMA-2006) to quantify time resolved RO_x (sum of OH, HO₂, RO₂) radical production from the photolysis of nitrous acid (HONO), formaldehyde (HCHO), glyoxal (CHOCHO), ozone (O₃), acetaldehyde (CH₃CHO), acetone (CH₃COCH₃). Respective photolysis-frequencies (J-values) were measured by spectroradiometry at ground-level. The Master Chemical Mechanism (MCMv3.1) is employed to calculate further ROx production from unconstrained sources, and express overall ROx production as OH-equivalents (i.e. taking into account the propagation efficiencies of RO₂ and HO₂ radicals into OH radicals). Quasi-simultaneous observations of HONO, HCHO and CHOCHO concentrations at ground-level (by open-path DOAS) and total vertical columns (by MAX-DOAS) enable the assessments of the vertical structure of radical production. Further, the total vertical column measurements enable a comparison with aircrafts intercepting the same airmass. The radical production during MILAGRO-2006 is compared MCMA-2003, which was held three years earlier in a different location of Mexico City. Further, a comparison of Mexico City with Milano, Chelmsford (near London), Birmingham, Pabstthum (near Berlin), and Nashville reveals differences in the magnitude and the timing of radical production. Since the photochemical processing of pollutants is radical limited in Mexico City, our analysis identifies the drivers for such processing. Opportunities are identified for effective air quality controls to reduce peak concentrations of secondary pollutants like O₃ and secondary organic aerosol (SOA). Our measurements and analysis comprise a database that enables testing of the representation of radical sources in photochemical models.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly