Mexico City Program

In the Spring of 2003 (April 1-May 5), a multinational team of experts led by Luisa Molina of MIT conducted an intensive, five-week field campaign in the Mexico City Metropolitan Area (MCMA). The overall goal of this effort is to contribute to the understanding of the air quality problem in megacities by conducting measurements and modeling studies of atmospheric pollutants in the MCMA. Such an understanding would help provide a scientific base for devising emissions control strategies to reduce exposure to harmful pollutants in the MCMA and also provide insights to air pollution problems in other megacities, including large urban centers in the US.

Aerial view of CENICA supersite.

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The MCMA-2003 field measurement campaign was designed to cover the height of the annual photochemical season just prior to the onset of the rainy season. Unlike the February 2002 exploratory field campaign (see Newsletter, Vol. 2, Fall 2002) that focused primarily on mobile laboratory measurements, the 2003 campaign also involved a highly instrumented “supersite” located at the National Center for Environmental Research and Training ( Centro Nacional de Investigación y Capacitación Ambiental or CENICA), a component of the National Institute of Ecology ( Instituto Nacional de Ecología or INE). The Aerodyne (ARI) Mobile Laboratory was deployed for measurements at various locations in Mexico City. In addition, extensive meteorological data and a wide range of fixed site chemical data were collected by our collaborating Mexican research groups.

The fixed “supersite” capability at CENICA was enhanced with state-of-the-art instrumentation contributed by many US and European teams. CENICA is housed in a building on the Iztapalapa campus of the Universidad Autónoma Metropolitana (UAM). CENICA maintains its own suite of routine (EPA level) air quality monitoring instruments for NOx, CO, O3, SO2, and PM10, and also has an automated sampling system for GC/FID analysis of volatile organic carbons (VOCs). In addition, the automatic monitoring network RAMA maintains two nearby air quality monitoring sites. When not involved in mobile off-site experiments, the mobile laboratory was sited at CENICA and its instrument suite contributed to the supersite’s database.

During the MCMA-2003 campaign, a tall flux tower was erected on the roof top of CENICA for continuous micrometeorological flux measurements of carbon dioxide, water vapor and total olefins and periodic flux measurements of NOy, NO2, NO, HNO3, NH3, H2CO, and other trace gases using mobile laboratory fast response sensors. The CENICA site also hosted collaborative measurements from various US and European institutions, including i) OH concentrations and reactivity measurements by William Brune’s team at Penn State; ii) a GC-based peroxyalkylnitrate instrument, an open-path near infrared ammonia vapor instrument, a Luminol chemiluminescent instrument for semi-continuous olefin measurements, and an Andersen Aethelometer for black carbon determinations from Jeffrey Gaffney and Nancy Marley of the Department of Energy’s Argonne National Laboratory (DOE/ANL); iii) nitro-PAH measurements by Roger Atkinson and Janet Arey’s team at the University of California, Riverside; iv) an aerosol mass spectrometer from José Jiménez’ team at the University of Colorado; v) a proton transfer reaction mass spectrometer (PTR-MS) and several radiometers and particle sampler from Pacific Northwest National Laboratory (PNNL); vi) two research lidars from Hubert van den Bergh and Valentin Simeonov’s team at EPFL and from MIT/Free University of Berlin, and a commercial lidar from Elight; vii) a research grade visible/near ultraviolet differ-ential optical analysis spectroscopy (DOAS) instrument provided by the University of Heidelberg and operated by the MIT team; viii) mini DOAS and FTIR from Bo Galle’s team at Chalmers University. A complete list of participating institutions is listed in the box.

A key feature of the spring MCMA-2003 campaign was the deployment of a new mobile laboratory designed and developed by ARI. The new ARI mobile lab is larger and equipped with significantly more instruments than the original version deployed for the MCMA 2002 exploratory field measurements described in the last newsletter (Vol. 2, Fall 2002). Additional fast response (1 s) instruments included a quantum cascade tunable infrared laser differential absorption spectrometer (QC-TILDAS) to measure gaseous ammonia (NH 3) from ARI, a commercial total nitrogen oxide (NO y) from MIT, a fast response DustTrak fine particle surface area monitor also from MIT, and a second commercial non-dispersive infrared carbon dioxide monitor from ARI. Additionally, slower response (10-60 s) instruments included a commercial UV absorption SO 2monitor from Washington State University, a commercial aethelometer on loan from the Lawrence Berkeley National Lab, a customized gas chromatographic instrument to measure peroxy acetyl nitrate (PAN) and related organic peroxynitrates from DOE/ANL, and a customized impactor to collect fine particles for subsequent synchrotr on X-ray analysis provided by PNNL. The PTR-MS from Montana State University used for fast response oxygenated and aromatic VOC compound measurements was successfully reconfigured to be used in mobile mapping and vehicle chase experiments as well as at fixed site deployments.

These additional instruments, coupled with the fast response trace gas and fine particle instrumentation from the original ARI mobile laboratory allowed a wide range of experiments to be pursued during the MCMA-2003 campaign. These included selected vehicle chase experiments to measure total nitrogen oxides, formaldehyde, acetaldehyde, ammonia, and selected aromatic VOCs exhaust emission ratios from heavy-duty diesel trucks, diesel buses, colectivos, taxis, and selected light-duty trucks and cars. We also mapped background concentrations of these and other compounds in selected MCMA industrial, commercial, and residential districts, paying particular attention to the area around the CENICA supersite, where we carefully characterized rush hour traffic emissions and detected industrial plumes of toluene and ethyl acetate. Large plumes of ammonia, uncorrelated with CO 2emissions, were also detected near CENICA and in other MCMA districts. Successful fixed site deployments were made to the Pedregal and La Merced RAMA monitoring sites and the Santa Ana boundary site.

An initial data analysis workshop will be held at MIT in August 2003 and a second workshop to discuss the preliminary results is scheduled for January 2004. Results of the field measurements will be communicated to the scientific community and decision makers through publications and conferences. It is anticipated that the insight obtained through the field measurements and analysis of the data will be crucial for protecting human health and ecosystem viability in the MCMA.

More than three dozen post-doctoral associates, graduate students and undergraduates from US and Mexican institutions were involved in the field measurement and data analysis. Working side by side, these researchers developed and used advanced methods for measuring pollutant emission fluxes and ambient concentrations. Thus, the MCMA-2003 campaign provides an excellent opportunity to build capacity for research, education, and policy in developing countries and contributes to international exchange.

Please visit our website on the field campaign and contact us if you have any questions or comments at ltmolina@mit.edu .

Jed Horne is an undergraduate Research Assistant and Robert Slott is a Visiting Engineer with the Integrated Program on Urban, Regional, and Global Air Pollution.

Field Campaign Photos

Field campaign participants; some who were not available during the photo session were added electronically.

Scene from the Fiesta Mexicana Farewell Party.

Terry Shirley and Robert Lesher explaining the OH measurements (mounted on flux tower platform) to Mario Molina.

Investigators (J. Jiménez, B. Lamb, R. Volkamer) explaining the measurements to visitors from UNAM, NOAA, and NCAR.

M. Castillejos, S. Lask, S. Zirath, V. Páramo and V. Gutierrez listening to Chuck Kolb inside the mobile lab.