Predicting Pollutant Dispersion Challenges Scientists

Posted: December 6, 2010 at 1:03 am, Last Updated: December 6, 2010 at 8:36 am

By Tara Laskowski

Pasquale Franzese. Photo courtesy of Pasquale Franzese

When disaster hits on action-packed TV shows like “24” or “CSI,” high-tech computers calculate risks and assessments almost instantly and provide exactly the information needed.

In real life, however, things are much more complicated.

Pasquale Franzese, research associate professor in the Department of Geography and Geoinformation Science, knows just how complicated.

He develops computer models that predict the rate of dispersion of pollutants that get released into the air. The pollutants could be anything from car exhaust fumes or an accidental chemical spill to a deliberate terrorist attack.

Even in the simplest of conditions, calculating how something will release into the air and how it will travel and expand is complex enough. Add in factors such as heat, weather, wind and geography, and you’re talking nearly impossible.

“It is an incredibly complicated problem, especially in urban areas,” says Franzese. “And yet, there is also a greater need for us to understand and predict pollution — especially deliberate or specific releases — as city populations and traffic increase.”

These studies are essential: If a disaster does happen, emergency responders and city and state officials can have models and analytics that predict evacuation areas as quickly and as accurately as possible.

With more sophisticated technology, the task does get easier.

“The tools are very good now. This branch of science and math has progressed tremendously, and there is more integration now,” says Franzese.

The National Science Foundation recently funded a three-year project for Franzese and his team at Mason and researchers at the University of Delaware. The team will be looking not only at how pollution disperses in cities, but also if there is a difference in that dispersion in the daytime compared to nighttime.

“The sun affects everything in the atmosphere,” he says. “Every motion — wind, rain, everything — is driven by sun. It heats up the ground, which in turn heats the air, creating movement.”

Therefore, when the sun is not shining — during the night — the way that pollution disperses is different.

Experiments in rural areas have shown this is so.

“If you go out at night in the countryside, it is very quiet. There is little wind and the atmosphere is more consistent. However, in the cities, the buildings make things more complicated — they still cause turbulence. We are looking now to see if the turbulence created by buildings at night in cities is comparable to the changes made by the sun during the day.”

The team will study these phenomena in two parts. Franzese and the other researchers at Mason will develop theoretical and computational simulations, and the team in Delaware will conduct laboratory experiments, simulating the dispersion using miniature buildings and water tanks. The team will also compare their data to experiments conducted in real cities.

Further down the line, Franzese would like to also assess the long-term health impact of chemical releases and pollution on people who live in or near a city or major highways.

“All of these components of research are important,” Franzese says. “Air pollution affects both the health and economics of entire societies.”

Write to mediarel at gazette@gmu.edu