University Times

Isotopes ID air pollution sources

Researchers from Pitt and the Electric Power Research Institute (EPRI) have developed a way to detect the isotopic signatures of nitrogen oxide (NOx) emissions that will help identify sources of air pollution. Their work was reported in the March 2012 issue of Environmental Science and Technology.

NOx emissions are formed during the combustion of fossil fuels. They mix with organic gases in the atmosphere to form ozone and particulate matter, the main components of smog. These emissions eventually settle onto surfaces and the deposited material, primarily nitrate, carries a measurable isotopic signature. However, until now, scientists were unable to interpret these signatures fully because they lacked the “fingerprints” of various NOx emission sources.

Pitt’s researchers modified existing Environmental Protection Agency methods to collect NOx from power plant stacks, then used bacteria to convert nitrate into a gaseous form for isotopic analysis. Prior to the coupling of these techniques, previous analytical approaches both were time- and labor-intensive and precluded widespread characterization of environmental nitrate isotopes.

Principal investigator Emily Elliott, a faculty member in the Department of Geology and Planetary Sciences, said, “We’ve been mapping the isotopes of nitrogen oxide deposition products across the nation. These ‘isoscapes’ can only be interpreted with fingerprint data like the isotopic signatures collected in this study.”

These results, combined with additional information from other NOx sources, will allow scientists to look at rain samples and determine how much nitrogen comes from power plants stacks as opposed to how much comes from such other sources as motor vehicles, lightning or soil.

J. David Felix, a project team member and doctoral candidate at Pitt, now is working to identify the isotopic composition of other reactive nitrogen emission sources, including those produced in animal feed lots, fertilizer applications and emissions produced by vehicles.

The team is conducting a pilot study with the Graduate School of Public Health to examine the isotopic composition of nitrogen oxides and determine their sources within the city of Pittsburgh, where exposures relevant to human health may be occurring.

Since incorporating low-NOx combustors and emissions control technologies, power plant emissions have decreased by more than 40 percent since 2005 and nearly 70 percent since 1990. Power plant NOx emissions are expected to continue to decline.

“Based on these results, the overall isotopic composition of power plant NOx emissions is expected to change and thus change the isotopic composition of nitrogen in environmental samples,” Elliott stated. “It was important for us to understand how the implementation of emission control technologies affects the isotopic nature of the NOx being emitted in order to evaluate its fate in the atmosphere.”

Funding for this study was provided by EPRI and the U.S. Department of Agriculture.

Researchers seek faster turbulent combustion models

A research team led by engineering faculty member Peyman Givi has been awarded a five-year U.S. Air Force grant to develop quantum-computing algorithms to better model turbulent combustion in aerospace applications.

The impetus for the Pitt team’s research is centered on the fact that despite its emergence more that two decades ago, quantum computing based on quantum mechanics hasn’t been used in aerospace applications, said Givi.

“Most people think of turbulence as unsettling or chaotic because of their experiences on planes,” said Givi. “But when it comes to engines, the hope is to make it as turbulent as possible. It’s like putting cream in your coffee. The more you mix it, the better it’ll taste or perform.”

Because of the nondeterministic nature of Givi’s classical equations for turbulence, the Pitt research team, which includes physics and astronomy faculty members Andrew Daley and Jeremy Levy and S. Levent Yilmaz of the Center for Simulation and Modeling, thought there might be a way to solve the equations on quantum computers, speeding the process of modeling turbulent combustion.

“We’ve developed equations that can model turbulent combustion very accurately, and we’ve been successful in solving them on today’s classical computers,” said Givi. “Now, with the help of this grant, we will formulate these equations in such a way that they can be solved on quantum computers.”

Because quantum computers have yet to be actualized, Daley and Levy will be looking at different concepts on how one might go about building quantum computers so the researchers can make hardware that acts like a quantum machine.

“If some of the things we are thinking do work and eventually we do achieve this, a process that could take weeks or months will transpire in minutes,” said Givi. “It really is a quantum leap.”

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The University Times Research Notes column reports on funding awarded to Pitt researchers as well as findings arising from University research.

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