HR: 08:30h
AN: A31C-03 [Abstracts]
TI: Flux Measurements of Trace Gases, Aerosols and Energy from the Urban Core of Mexico City
AU: * Velasco, E
EM: evelasco@mce2.org
AF: Molina Ceneter for Energy and the Environment (MCE2), 3262 Holiday Court, Suite 201, La
Jolla CA, CA 04530, United States
AU: Molina, L
EM: ltmolina@mce2.org
AF: Molina Ceneter for Energy and the Environment (MCE2), 3262 Holiday Court, Suite 201, La
Jolla CA, CA 04530, United States
AU: Lamb, B
EM: blamb@wsu.edu
AF: Washington State University, Laboratory for Atmospheric Research, Department of Civil
and Environmental Engineering, Pullman, WA 99164-2910, United States
AU: Pressley, S
EM: spressle@mail.wsu.edu
AF: Washington State University, Laboratory for Atmospheric Research, Department of Civil
and Environmental Engineering, Pullman, WA 99164-2910, United States
AU: Grivicke, R
EM: rgrivicke@gmail.com
AF: Washington State University, Laboratory for Atmospheric Research, Department of Civil
and Environmental Engineering, Pullman, WA 99164-2910, United States
AU: Westberg, H
EM: westberg@mail.wsu.edu
AF: Washington State University, Laboratory for Atmospheric Research, Department of Civil
and Environmental Engineering, Pullman, WA 99164-2910, United States
AU: Jobson, T
EM: tjobson@wsu.edu
AF: Washington State University, Laboratory for Atmospheric Research, Department of Civil
and Environmental Engineering, Pullman, WA 99164-2910, United States
AU: Allwine, E
EM: allwineg@wsu.edu
AF: Washington State University, Laboratory for Atmospheric Research, Department of Civil
and Environmental Engineering, Pullman, WA 99164-2910, United States
AU: Coons, T
EM: tcoons@wsu.edu
AF: Washington State University, Laboratory for Atmospheric Research, Department of Civil
and Environmental Engineering, Pullman, WA 99164-2910, United States
AU: Jimenez, J
EM: jose.jimenez@colorado.edu
AF: University of Colorado, UCB 216, Boulder, CO 80309-0216, United States
AU: Nemitz, E
EM: en@ceh.ac.uk
AF: Centre for Ecology and Hydrology, Bush Estate,
Penicuik,
Midlothian, EH26 0QB, Edinburgh, United Kingdom
AU: Alexander, L M
EM: mikaela.alexander@pnl.gov
AF: Pacific Northwest National Laboratory, 902 Battelle Boulevard
, Richland, WA 99352, United States
AU: Worsnop, D
EM: worsnop@aerodyne.com
AF: Aerodyne Research, Inc, 45 Manning Road, Bellerica, MA 01821-3976, United States
AU: Ramos, R
EM: rramos@sma.df.gob.mx
AF: Sistema de Monitoreo Atmosferico del GDF, Agricultura 21, Col.Escandon, Mexico City, DF
18800, Mexico
AB:
As part of the MILAGRO field campaign in March 2006 we deployed a flux system in a busy district of Mexico City
surrounded by congested avenues. The flux system consisted of a tall tower instrumented with fast-response
sensors coupled with eddy covariance (EC) techniques to measure fluxes of volatile organic compounds (VOCs),
CO2, CO, aerosols and energy. The measured fluxes represent direct measurements of emissions that include
all major and minor emission sources from a typical residential and commercial district. In a previous study we
demonstrated that the EC techniques are valuable tools to evaluate emissions inventories in urban areas, and
understand better the atmospheric chemistry and the role that megacities play in global change. We measured
fluxes of olefins using a Fast Olefin Sensor (FOS) and the EC technique, fluxes of aromatic and oxygenated VOCs
by Proton Transfer Reaction-Mass Spectroscopy (PTR-MS) and the disjunct eddy covariance (DEC) technique,
fluxes of CO2 and H2O with an open path Infrared Gas Analyzer (IRGA) and the EC technique, fluxes of CO using
a modified gradient method and a commercial CO instrument, and fluxes of aerosols (organics, nitrates and
sulfates) using an Aerodyne Aerosol Mass Spectrometer (AMS) and the EC technique. In addition we used a
disjunct eddy accumulation (DEA) system to extend the number of VOCs. This system collected whole air
samples as function of the direction of the vertical wind component, and the samples were analyzed on site using
gas chromatography / flame ionization detection (GC-FID). We also measured fluxes of sensible and latent heat
by EC and the radiation components with a net radiometer. Overall, these flux measurements confirm the results
of our previous flux measurements in Mexico City in terms of the magnitude, composition, and distribution. We
found that the urban surface is a net source of CO2 and VOCs. The diurnal patterns show clear anthropogenic
signatures, with important contributions from vehicular traffic. The DEA results for individual hydrocarbons show
that the alkane fluxes are considerably higher than alkene fluxes, which is consistent with ambient concentration
measurements and with the emission inventory for Mexico City. CO fluxes, estimated from a modified gradient
technique, were more than 10% of the measured CO2 fluxes (on a molar basis) which is much higher than is
generally expected for combustion efficiencies in mobile and other sources. Investigation of this result is
underway. The energy balance distribution and radiative parameters observed are similar to distributions and
parameters reported for other urban sites.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0312 Air/sea constituent fluxes (3339, 4504)
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly