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U Runs $1.49 Million Urban Airshed Study

December 16, 2002 — Mention urban air pollution, and people often think of vehicle exhaust pipes and smokestacks. But the factors contributing to the ugly haze over a city are far more complex. They also include urban sprawl, weather, government policies, water vapor from landscape irrigation, commuter psychology, and volatile organic compounds from gas stations, industrial solvents, vegetation and other sources.

To better understand those factors and how they interact, more than two dozen University of Utah researchers and students are mounting a $1.49 million effort to study the complicated Salt Lake Valley airshed as an ecosystem. They will develop a high-tech computer simulation to help government officials test possible ways of cleaning the air. The simulation software eventually will be available on the Internet.

“The urban airshed is a complex environment. If we are going to make good decisions about how to keep the air clean and healthy in the coming decades, we need to understand how the system works,” says project spokesman and hydrogeologist Craig B. Forster, a research associate professor of geology and geophysics. “We could spend a lot of money on strategies to improve air quality that might ultimately be wasted if we don’t understand how the airshed works.”

The computer simulation will incorporate data on population growth, land use, vehicle miles traveled in the valley, various emission-reducing federal and state laws and policies, ongoing air pollution data, and new measurements of three kinds of emissions that enter the airshed: water vapor, volatile organic compounds and carbon dioxide, a combustion product that is a “greenhouse gas” because it helps trap heat from the sun in Earth’s atmosphere.

Atmospheric scientists, ecologists, urban planners and social scientists are among those involved in the multidisciplinary Salt Lake Valley Airshed Project, which began Sept. 1 and will last until spring of 2005 with $1.49 million from the National Science Foundation. The project includes faculty from the University of Utah Health Sciences Center and the Colleges of Science, Engineering, Humanities, Mines and Earth Sciences, and Social and Behavioral Sciences.

The study will help “develop a new approach to looking at cities as ecosystems,” says ecologist Diane Pataki, a research assistant professor of biology and leader of the project’s five principal investigators.

“We want to study lots of different components of the city that contribute to the quality of the urban airshed and greenhouse gas emissions within it. We’re basically trying to understand biocomplexity – the fact that biological systems and lots of different physical and human systems all interact. We are picking a specific part of biocomplexity: the airshed. Our focus is on the linkage between the city and the atmosphere.”

Pataki says air pollution is influenced by “what people emit into the atmosphere through driving cars and through industrial activities. We also have an urban forest here that helps absorb pollution. There is atmospheric chemistry and weather that moves gases into and out of the valley. All of these things are influenced by the decisions people make – in politics and also individual decisions, personal behavior.”

The computer simulation software developed during the study will be used by “scientists and policy people to explore scenarios of how to clean up our air,” Pataki says. “There also will be scenarios of different future patterns of growth in the valley and how they affect air quality.”

Forster says 14 U. faculty members plus at least a dozen undergraduate and graduate students will work on the project, as well as student volunteers and personnel from state and local government agencies.

“Lots of different areas of science are part of the way cities functions,” Pataki says. “We’re bringing together people from different disciplines who are interested in individual aspects of cities.”

The five principal investigators:
— Pataki will measure water vapor, carbon dioxide and volatile organic compounds emissions at three sites with different land cover – suburban, urban and industrial-commercial – and the contribution by trees and other plants.
— Forster will help build the computer simulation and use his expertise in the water cycle in the Salt Lake Valley.
— Philip Emmi, an urban and regional planning professor, will work on urban growth and transportation components of the computer simulation.
— Joseph Klewicki, the U.’s chair of mechanical engineering, will study the effect of land use on wind patterns and air circulation.
— Tarla Peterson, an associate professor of communication, will be instrumental in bringing the research team together with government officials and the public.

“We are going to get a lot of input from decision makers,” Pataki says. “We are working more with agency people, the technical people.”

Forster says the study will focus on carbon dioxide because of its role in climate warming; water vapor because of its role, in what once was non-irrigated desert, in the formation of ozone and other pollutants and its effect on weather; and volatile organic compounds because “they are health concern in their own right and also contribute to formation of ozone and other air pollutants” in smog.

He says these “trace gases” are rarely measured. The scientists will use measurements and calculations to determine how much of the gases come from vehicles, industry, vegetation and other sources in each of three different land use zones: a low-density residential suburb, a high-density urban residential area and an industrial-commercial area.

The researchers will work with the Utah Division of Air Quality to use that agency’s data on ozone, nitrous oxides, sulfur dioxide, carbon monoxide and other air pollutants.

Forster says meteorologist Jim Steenburgh will help provide weather data needed for the study; psychologist Carol Werner will study driving habits, such as why more people seem to drive when “no drive” days are declared due to air pollution; and geographer Elizabeth Dudley-Murphy will study satellite images over time to measure changes in the extent of vegetation and residential, industrial and total urban land use, and how land use contributes to air pollution.

Engineer Hendrik Meuzelaar will sample emissions of volatile organic compounds; Pataki and biologist Jim Ehleringer will analyze carbon and oxygen isotopes in carbon dioxide to determine how much of the greenhouse gas comes from fuel-burning in homes and vehicles and how much comes from plants; engineer Peter Martin, director of the Utah Traffic Lab, will provide traffic measurements used to estimate real-time vehicle emissions; and engineer Bonnie Tyler will study particulate air pollution.

The computer simulation will crunch the data to see what factors give the most bang for the buck in improving air quality, Forster says. “We’re going to play what-if games with the computer simulation.”

Near the end of the study period, the researchers will involve public officials in the computer simulations and ask them “to explain what futures they want and how they are going to get there,” Forster says.

Pataki says the project will “come to some conclusions about how to clean our air, but we can’t solve all the problems.”

But Forster adds: “We are trying to help people living in the community learn more about how what they do affects air quality in terms that might change behavior.”