Mobile Laboratory Measurement of Black Carbon

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Mexico City Project

Air pollution in Mexico City

The Mexico City Metropolitan Area (MCMA) includes Mexico City and a number of municipalities of the neighboring State of Mexico. It sits at an altitude of 2240 m above mean sea level, and spreads over 5000 km2 of the Mexican plateau. The surrounding mountain ridges make the elevated basin roughly 800 -1000 m deep and effectively trap the atmospheric pollutants produced in this area. The meteorological conditions, featuring strong inversions and intense solar radiation, favor the photochemical formation of ozone.Added to these unmanageable natural factors, nearly 20 million residents, 3.5 million vehicles, and 35,000 industries consume daily more than 40 million liters of fuel (Molina et al. 2002), making the transportation sector an extremely important source of air pollution in this area. According to the 1998 emissions inventory, mobile sources contribute nearly all of the CO, about 80 percent of the NOx, 40 percent of the hydrocarbons (HC), 20 percent of the SO2, and 35 percent of the PM10 (particulate matter of aerodynamic diameter 10 µm and less) emitted in the MCMA (CAM 2001). Apart from the huge number of vehicles and amount of fuel consumed, the situation is especially exacerbated by congestion, lack of emission control and poor fuel quality.Having recognized the air pollution problem as a major social concern, the city has undertaken a series of measures to control the emissions since the mid-1980s, such as fuel reformulation, enforcement of a vehicle inspection and maintenance program and the“no-driving day” program. While these efforts successfully reduced the concentrations of some pollutants such as lead, CO and SO2 to a significant extent, some of the other air quality standards are still frequently violated. For example, the ozone standard has been exceeded on ~80% of the days every year since 1988, and the daily standard for PM10, which used to be violated on more than 40% of the days in some years, is still exceeded on ~10% of the days (Molina et al. 2002; Molina et al. 2004).

Mexico City Project and the MCMA 2003 field campaign

The Mexico City Project includes a variety of interrelated studies in health impacts,atmospheric science, transportation, economics, technology, and policy, aiming to“provide objective, balanced assessments of the causes and alternative cost-effective solutions to urban, regional and global air pollution problems” (Molina et al. 2002). The project involves a multidisciplinary group of researchers from a wealth of institutions from Mexico, the United States and Europe, and active collaboration with Mexican government officials and decision makers. As the main effort to support the understanding of the air pollution problem in the city, the five-week MCMA-2003 field campaign was launched in Spring 2003 to conduct measurements and modeling studies of atmospheric pollutants in the Mexico City Metropolitan Area. Such an understanding will not only help to build a scientific basis for developing emissions control strategies in the MCMA, but will also provide insights to air pollution problems in other megacities in the
world. The MCMA-2003 field measurement campaign was scheduled to capture the peak season of photochemical activity in this area, but to avoid the rainy season. A major feature of the campaign was the use of a mobile laboratory to measure air quality at different locations around the city and to chase vehicles and measure their emissions. The mobile laboratory was developed at Aerodyne Research, Inc. (ARI) and equipped with a range of real-time particle and trace gas analyzers. Table 0.1 presents the main instruments and the corresponding pollutants that were measured. Ambient measurements were also conducted at fixed sites, including a highly instrumented “supersite” where a suite of sophisticated monitoring equipment was housed in the National Center for Environmental Research and Training (Centro Nacional de Investigación y Capacitación Ambiental or CENICA). The mobile laboratory also spent time at a few other locations in Mexico City, including La Merced (near downtown), Pedregal (a downwind suburb) and Santa Ana (at the downwind boundary of the Mexico City air basin). When not involved in mobile mapping, chasing or other offsite experiments, the mobile laboratory was sited at CENICA, where its instrument suite contributed to the supersite’s database.

Mobile laboratory

The mobile laboratory deployed in the MCMA-2003 field campaign is a large van equipped with numerous instruments measuring gaseous and particulate concentrations.The instrumentation and its layout in the 2003 ARI mobile lab are shown in Table 0.1.

List of Figures
List of Tables
General Introduction
Research Objectives
Black Carbon
Emission Factors
Previous Studies
Mexico City Project
Air Pollution in Mexico City
Mexico City Project and the MCMA 2003 field campaign..
Mobile Laboratory
Selected Instruments
Manuscript: Mobile Laboratory Measurement of Black Carbon, Polycyclic Aromatic Hydrocarbons and Other Exhaust Emissions in Mexico City
Experimental section
Appendix A. Emission inventory calculations
Appendix B. Spatial and temporal distributions of BC and PPAHs
Appendix C. Black carbon QA procedures
Appendix D. Igor Pro procedures

Mobile Laboratory Measurement of Black Carbon, Particulate Polycyclic Aromatic Hydrocarbons and Other Exhaust Emissions in Mexico City

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