Standing in the heart of the city on a relatively clear March day, DRI chemist Dr. Barbara Zielinska (far left) looks toward a cathedral flanked by a few of the 40,000 buses and trucks of Mexico City.

Even in Moctezuma's day, the forerunner to modern Mexico City was larger than any existing Spanish city. And today, as the largest city in the world, and home to nearly a quarter of the country's total population and a third of its industrial activity, the Valle de Mexico has also become one of the world's most widely recognized air pollution challenges. Standing in the heart of the city on a relatively clear March day, DRI chemist Dr. Barbara Zielinska (far left) looks toward a cathedral flanked by a few of the 40,000 buses and trucks of Mexico City. Air quality scientists from DRI have joined colleagues from several Mexican and U.S. research organizations to study the nature and sources of the region's health-threatening airborne particles. They're also looking beyond the region to address a worldwide concern: how does air pollution from such major metropolitan areas"megacities"affect our planet's atmosphere, and in turn, our climate?

DRI's history in conducting this type of study is short compared to Mexico City's air quality experience, but lengthy in terms of the technology it is using there. DRI scientists first developed their air quality "fingerprinting" and modeling techniques for the U.S. Environmental Protection Agency in the early 1980s, first applied them under state-funded studies in Reno and Las Vegas, and since then, across the U.S. and in several foreign countries. Now they're putting them to use in a project regarded as an example of international cooperation in environmental research, and which was slated as an agenda item for discussion during President Bill Clinton's planned spring visit to Mexico City.

Mexico City may possess one of the world's most pleasing climates20 million people can't be wrong! But its 7,000-foot-plus elevation enhances the health-threatening aspects of particles, and hundreds of miles of unpaved roads and the spread of many small and medium-sized businesses that escape effective regulatory attention have created a major air pollution dilemma in an otherwise idyllic setting. Though quite picturesque when visible through the haze, the surrounding 20,000-foot-high mountains and active volcanos effectively block the wind from ventilating the valley, and the prevailing sunny weather peaks the production of health-threatening ozone regularly.

Every day, technicians from the Instituto de Mexicano de Petroleo changed filters on DRI air samplers at 30 sights around Mexico City. This is the "super site" in central Mexico City on the roof of a clinic adjacent to a school. The samplers collect particles from different times of the day on different filters to show the variation of air pollution over each 24-hour period.

As the world's most populous area, Mexico City must also contend with the usual number-one urban air quality culprit, auto emissions. Statistically, the vehicle density in Mexico City is low, only one car for every six and two-thirds persons (compared, for instance, with about one car for every one and a half residents in the Las Vegas area). An extensive and inexpensive modern subway system, uncounted colorful Volkswagen "beetle" taxis, and thousands of buses also provide city transportation for local residents.

Since 1990, aggressive regulatory efforts in Mexico City have paralleled the most stringent measures applied in any U.S. city. Several important pollutant categories, such as sulfur dioxide emissions from diesel fuel and residual oil, and lead from leaded gasoline usage have been significantly reduced. The mandatory switching of all major industry from coal and heavy fuel oil to liquefied petroleum gas (LPG) has traded some very serious pollutant sources for a much lesser, but still persistent one.

Mexico City residents, who demonstrated a very high awareness of the problemas well as interest in the project are also required to park their personal autos one day a week. Unless the vehicles have passed a stringent smog test, drivers risk the penalty of immediate impoundment if caught driving on the wrong day. Despite these efforts, the daily build-up of a brown pollutant haze still parallels peak traffic periods. Congested primary roadways crawl through the city center, while outlying traffic on unpaved roads kicks tons of dust into the air each day.

To learn more about and from these problems, Desert Research Institute scientists Drs. Judith Chow and John Watson are leading a group of Mexican and American scientists and technicians, including Dr. Barbara Zielinska, Dale Crow and Dick Egami from DRI. In late winter, they established a network of 30 instrumented sampling sites that ranged from the congested city center, to major industrial sectors, and out to rural fringe areas.

An intensive one-month, round-the-clock sampling portion of the project was wrapped up March 22. This resulted in the collection of more than 8,500 filter samples, many megabytes of meteorological data, and many other observations that will provide the first such comprehensive profile of the city's air quality character. The data will also provide information for estimating the contributions of other major cities to the total load of pollutants in the earth's atmosphere.

Before the project began, institute scientists hosted Mexican technicians in DRI's Reno laboratories and shared with them the latest analytical techniques, which they are now using in Mexico City. It will take the Mexican and American researchers two years to complete laboratory analyses of filtersand subsequent data analysis and interpretation.

Dr. Barbara Zielinska of DRI (with sunglasses) reviews the process for changing air filters with technicians Guadalupe Trejo Corona, left; Jose Arriaga Colina, Center; and Sergio Escalona Segura, right; in front of a DRI aerosol sampling device in central Mexico City.

The project is funded by the U.S. Department of Energy and the Mexican petroleum giant, PEMEX, through the Instituto de Mexicano de Petroleo, a senior Mexican research institute. The study includes major U.S. research entities such as Argonne National Laboratory, Los Alamos National Laboratory, Pacific Northwest Laboratory, and the National Oceanic and Atmospheric Administration (NOAA). Mexican regulatory agencies and university research groups are also participating.

When the project's results are reported in 1999, the Mexican government intends to use the information to strategically allocate pollution-fighting resources where they will have the greatest positive effect on Mexico City's air quality.

For DRI and its international collaborators, the project serves as a model for future joint efforts aimed at addressing major global air quality issues, one megacity at a time.
- John Doherty

	CLOUDING THE ISSUES 20 million people, 3 million cars High altitude increases health dangers of particulates Surrounding mountains block wind ventilation Ancient lakebed floor of Valle de Mexico creates major source for dust Thousands of small businesses and light industries escape effective air quality regulation CLEARING THE AIR Heightened citizen awareness and concern for air quality
Dr. John Watson checks the control mechanism on an air sampler in central Mexico City. The mail boxes serve as protective housing for the sampler's air pumps.	"No Drive" day each week for each private vehicle Introduction of unleaded fuels Elimination of coal and fuel oil for all heavy industry Extensive, inexpensive subway system

The DRI researchers who pioneered air pollution tracking techniques and cloud seeding technology broke new ground on April 10, literally. They were among the large crowd in a ceremonial groundbreaking celebrating the symbolic birth of the institute's new Northern Nevada Science Center.

Dr. Pat Arnott spoke for the 128 faculty and staff who will be moving from DRI's Stead facility to the new building in the Dandini Research Park. Their current home was constructed in 1954 as regional headquarters for the U.S. Air Force's North American Air Defense Command, complete with 18-inch-thick concrete walls. After a humorous description of the challenges of doing atmospheric research in a building with lots of concrete and very few windows, Arnott shared his enthusiasm and expectations for DRI's newscience center: "I expect to forge new ties with the institute, the NationalWeather Service and Truckee Meadows Community College . . . and I expect our strong university connections through students, teaching, and collaboration will be enhanced."

The people who applauded Arnott's words stood on a windswept hill overlooking the city of Reno. They were the people who helped turn a 30-year effort into reality: leaders from the institute, DRIfoundation, legislature, government, university system,community and business. After recognizing the key roles Nevada Senator Bill Raggio and retired DRI Vice President Dale Schulke played in securing state support for DRI'snew science center, institute President James V. Taranik turned the shovels over to the groups pictured on these pages. Before and afterthe ceremony, guests enjoyed a "Science Sampler," a poster session which showcased the worldwide environmental research of more than 40 different DRI scientists.

Made possible by an $11.3 million appropriation from the 1995 Nevada Legislature, the construction of DRI's new science center is under the direction of the Nevada State Public Works Board. The 60,000-square-foot building was designed by Dolven Simpson Associates; JMA Architecture Studios; and Martin, Peltyn and Early Engineers. At the time of this printing, construction bids were still being solicited and the University and Community College System of Nevada was seeking another $2.4 million in capital improvement funds from the current legislature to fully complete the internal space in the structure.

DRI hopes to occupy its new Northern Nevada Science Center, adjacent to the Maxey Science Center, in the summer of 1998. The facility will

NORTHERN NEVADA SCIENCE CENTER WILL INCLUDE THESE LABORATORIES: optics, acoustics, aerosol physics, weather, telemetry, radar, instrument development, cold room, clean room, precipitation sampling, paleobotany analysis, herbarium, image analysis, chemistry, ice physics, quality assurance, electronics and machine shops, field staging, drop columns, and a science tower.

consist of a three-story laboratory/office building with a two-story wing for library and meeting space. It will include a unique, vertical laboratory, or "science tower," with 70 feet of vertical space in which to create soil, water, or controlled-atmosphere columns for specialized experiments. The tower will be capped by a room overlooking the city that can be used for atmospheric research, such as laser remote sensing of Reno's smog layer.

The science center's library/meeting wing will provide space for DRI's research collection and will allow the institute's library to grow into the "virtual" library of the future, with the necessary infrastructure for computer networking. Just as the science laboratories will be state-of-the-art, so will the meeting facilities, with video conferencing equipment serving as both a cost-effective communications link between DRI's northern and southern science centers and as an important component in the state's distance education program.

When Taranik concluded the ceremonial groundbreaking, he spoke about what the new building means to the people of DRI. "I want you to leave with two things in mind," he said, "How important the new Northern Nevada Science Center is to our scientists and graduate students and the work they do, and how many people worked together to make the center a reality."