CIRES scientist Gabrielle Petron uses a specially equipped Toyota Prius to study air pollution

CIRES scientist Gabrielle Petron uses a specially equipped Toyota Prius to study air pollution.
Photo courtesy Adam Hirsch

Pollution hunters

Tracking down the sources of polluted air

By Jane Palmer

A multi-pronged Prius, decked with a recycling-container chapeau and sprouting tubes from its windows, might look like an artifact from an old science fiction movie, but it is just CIRES scientist Gabrielle Petron’s way of taking her research on the road.

From their mobile laboratory, Petron and her colleagues from NOAA’s Earth System Research Laboratory are tracking down the origins of the air pollution in the Colorado Northern Front Range region. “It’s invaluable being able to drive around and work like a detective,” Petron said. “That way, you can try to directly link the air pollution you observe to its source.”

The incentive for Petron’s grass-roots investigation came from some unexplained observations recorded at the NOAA Boulder Atmospheric Observatory (BAO), an instrumented, 1,000-foot-high tower located in Erie, Colo. (see story, page 14). Air pollution measurements at the tower revealed high levels of a class of pollutants called alkanes, especially relative to long-term measurements from eight similar towers located in other areas of the nation. “We thought, ‘Hmm,

BAO is not the same—what is going on there?’ ” Petron said.

The chemical and meteorological measurements, which indicate both the type of the air pollution and the wind direction it comes from, further surprised the scientists. “With the tower being so close to Denver, we thought we would mostly come across urban pollution,” Petron said. “But Denver was not a big piece in what we saw.”

Instead the scientists found that a lot of the air pollution came from the northeast part of the state, Petron said. This region, Weld County, houses more than 12,000 oil and gas wells and also numerous tanks that store the liquid hydrocarbons or condensate separated from the natural gas at the wells or processing plants. Could these wells and tanks be the major cause of the air pollution observed in the Northern Front Range?

To find out, the team equipped the car with cutting-edge air pollution detection instrumentation and hit the roads. The instruments measured all the common greenhouse gases and air pollutants, including carbon dioxide, ozone, methane and carbon

monoxide. The scientists drove around Weld County with a map and their monitoring system to see what they could find.

“We could see the real-time data,” Petron said. “Every so often, I’d say to my colleague: ‘Wait a second, something is happening. We have to stop and take a sample.’” After the scientists had spent a couple of hours driving, stopping and taking air samples, they would return to their base where the contents of the flasks could be analyzed at two labs.

The team’s research will give valuable information about emissions from the oil and gas industry, Petron said. Currently, a large portion of the Northern Front Range of Colorado is noncompliant for summertime ozone. The state and the Environmental Protection Agency are working hard to derive bottom-up inventories in the region, she said.
Petron hopes the study will encourage collaboration between the scientists and regulators with the goal of mitigating air pollution. “The power of doing something locally is that you can have a big impact,” she said. “You have direct access to people who have a strong interest in your measurements.”