Hittin' the Road

Improving Air Quality Predictions

They come from different sources — diesel engine emissions and wood fires — but until recently, there was no clear picture for how organic aerosols change once they become part of the atmosphere.

"The atmosphere acts like Dan Aykroyd's Bass-O-Matic," explained Neil Donahue, the atmospheric chemist who heads Carnegie Mellon's Center for Atmospheric Particle Studies (CAPS). " It makes similar looking goop almost no matter what you start with; could be diesel soot, could be wood smoke, could be molecules emitted by trees. Once the atmosphere is done, it all looks the same."

So Donahue created a chemical map that provides some of the first clear images of how organic aerosols change once they become part of the atmosphere. Carnegie Mellon Professor Allen Robinson led an experimental team demonstrating those changes for aerosols emitted from diesel engines and wood fires.

The research was featured in a study they co-authored for a recent issue of Science.

"The blurring of the emissions of different sources is potentially a very important simplification, which is key to improving air quality and climate models," said Robinson, who is a professor of mechanical engineering and engineering and public policy.

He added, "Atmospheric processing alters the effects of aerosols on climate and human health. It appears to greatly simplify the effect of the aerosols from different sources on cloud formation and rainfall."

Donahue and Robinson are working with a team of more than 60 scientists, including researchers from the University of Colorado and the NOAA's Cooperative Institute for Research in Environmental Science, to develop a more holistic approach to improving climate and air quality prediction models.

The work at Carnegie Mellon's CAPS is key to those efforts, especially their work in the field.

Professor Robinson and CAPS Research Manager Albert Presto recently led a team of Carnegie Mellon researchers on a mission at the source of particulate pollution — a refueling wing at a major airport. They studied jet aircraft emissions and their impact on the region's air.

The team harnessed new technology — a custom-outfitted box truck with on-board instruments that allow researchers to conduct experiments at places where the pollution exists, rather than having to take everything back at the lab.

Outfitted through a $250,000 grant from Colcom Foundation, this “mobile lab” enables better data collection and monitoring. It also provides an ideal outreach tool to engage the local residents concerned about air quality. This past December, the CAPS team showcased the mobile lab to students from South Allegheny High School, where the team was doing air quality monitoring. The students learned about the global and local impacts of particle pollution.

In September, the team traveled to the Fire Science Laboratory in Missoula, Mont., to study how wildfires affect air quality. Next summer, in collaboration with the California Air Resources Board, the mobile lab will head to El Monte, Calif., to conduct auto emissions research.

For more than a decade, Carnegie Mellon researchers have been working to pinpoint the sources and effects of harmful atmospheric particles. And the future work of researchers at CAPs will continue to play a key role in better understanding issues around pollution that are adversely affecting human health.

Photo: Carnegie Mellon research team monitoring an experiment with the Mobile Research Lab. (l. to r.) Manish Ranjan, now a post doctoral researcher at Lawrence Berkeley National Lab; and Aaron Reader, a Mellon College of Science 2009 graduate.

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