University of Houston Cullen College of Engineering


Researcher Working to Quantify Real-World Impact of Automobiles


Toby Weber

While there are plenty of advantages to living in a big city, one big drawback is air quality. Nearly every large metropolitan area in the country struggles to keep its air pollution levels in line with standards recommended by physicians and mandated by government.

To more easily meet these standards, cities should first know what chemicals, exactly, can be found in pollution from different sources.

That’s where Shankar Chellam comes in. As a professor of civil and environmental engineering at the University of Houston Cullen College of Engineering, Chellam works to identify the unique chemical makeup, or “fingerprints,” of various sources of air pollution.

While much of his previous research examined industrial sources of pollution such as petroleum refineries, Chellam recently received a grant from the Texas Air Research Center to find the pollution fingerprint of gasoline-driven vehicles.

According to Chellam, it’s far more challenging to identify the pollution caused by vehicles than by stationary industrial sources. A sensor placed at an industrial site can provide an essentially undiluted sample of that site’s emissions. Vehicles, however, operate out in the open air, where their exhaust immediately mixes with pollution from other sources, making it extremely difficult to get a measure of their combined real-world impact.

The Houston area, though, is home to the Washburn Tunnel, the state’s only operational underwater vehicle tunnel and hence an ideal location for Chellam’s research. “If we sample the air in this tunnel, the chances of other sources impacting our sample are very, very slim. Whatever we measure can be directly attributed to the vehicles that go through the tunnel,” he said.

The first step of this process involves perfecting methods of measuring the metals emitted by automobiles. Working with post-doctoral researcher Suresh Kannan and doctoral student Nick Spada, Chellam will first work to extract from particulate matter samples metals such as platinum, palladium, vanadium, chromium, zinc, copper, barium, antimony and lead. The research team will then refine ways of measuring these metals in very low concentrations using instrumentation based on inductively coupled plasma – mass spectrometry. Chellam anticipates that this phase of the research will take roughly one year.

Afterwards, in cooperation with local and state officials and Professor Matt Fraser, a researcher from Arizona State University, Chellam will place air samplers in the tunnel to measure particulate matter emissions. Since the tunnel is closed to diesel-driven semi trucks, this project will offer the fingerprint of gasoline-powered vehicles only, with few exceptions.

By measuring pollution produced by thousands of cars over hours and even days at a time, Chellam will be able to determine the real-world make-up of the airborne particulate matter pollution arising from gasoline-driven vehicles.

While the immediate goal of this research is simply to identify the chemical fingerprint of automobile exhaust, Chellam hopes that his work ultimately will be used to make life in cities, and elsewhere, more livable.

“What we hope is that by communicating our findings, there may be some environmental policy decisions made based on our research and similar work that others are doing,” he said.



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