CHEYENNE, Wyo. - Ozone-forming air pollution measured along the Colorado Front Range by scientists is up to twice the amount that government regulators have calculated should exist, according to a new study.
The researchers pinpoint oil and gas development as the main source - a finding that could have broad implications for the petroleum industry across the Rocky Mountain region.
The Front Range in recent years hasn't met U.S. Environmental Protection Agency standards for ozone pollution during the summertime. A similar problem occurs in the growing gas fields of western Wyoming and eastern Utah during the winter, when conditions including bright sunshine, temperature inversions and snow on the ground help stimulate ozone formation.
Ozone levels in Wyoming's Upper Green River Basin last winter exceeded some of the worst days in big cities during the summertime, causing some to complain of itchy eyes and nosebleeds and Wyoming regulators to urge children and the elderly to stay indoors.
This winter, the scientists are conducting research similar to the Front Range study in eastern Utah's Uintah Basin. One Utah environmental official said his state, too, might have underestimated emissions seeping from the basin's myriad pipelines and other gas field equipment.
"There are a lot of valves out there. It's very hard to get at a real detailed, accurate emissions inventory out there. We try to do the best we can but sometimes things get missed," said Brock LeBaron, deputy director at the Utah Division of Air Quality.
He said he welcomed Gabrielle Petron and other atmospheric scientists to his state for what he said is the largest air pollution study in Utah history.
Starting in 2007, the scientists measured elevated levels of methane and other atmospheric hydrocarbons from atop a nearly 1,000-foot tower north of Denver. The tower is one of eight nationwide monitored by the National Oceanic and Atmospheric Administration.
Unlike the other seven towers, the Boulder Atmospheric Observatory tower had been picking up unusually high levels of substances such as propane, butane and pentane.
"These are tracers of natural gas. When we noticed that, we thought, OK, could it be Denver because Denver is only 25 miles south of our tower? Could it be that, or is it something else in the region that we're not aware of?" Petron said Thursday.
They pump air down from the tower for sampling by way of a 1,100-foot-long tube.
The researchers then took their study down to ground level, driving up and down the Front Range in a mobile lab. They took air samples by elevating some Teflon tubing attached to the end of a 9-foot expandable fishing pole. They got similar results.
Meanwhile, they checked and ruled out other possible pollution sources such as landfills and feedlots. That left oil and gas development in the Denver-Julesburg Basin northeast of Denver as the best match as the pollution source.
"We knew that there was oil and gas activity in the area but we didn't expect it to be such a large source. We didn't expect to see so much fugitive emissions," said Petron, a scientist with the Cooperative Institute for Research in Environmental Sciences, a joint effort of NOAA and the University of Colorado.
The Journal of Geophysical Research is publishing their study.
The levels of pollution measured are significant for exceeding the amounts the researchers determined would be predicted by emission inventories, or projected air pollution based on estimated emissions from known pollution sources. The EPA and state regulators use emission inventories to estimate air pollution.
A University of Wyoming researcher specializing in air pollution from hydrocarbons called the Front Range study excellent and a good example of the importance of backing up emission inventories with actual measurements.
"Emission inventories are really difficult to construct and maintain. It is important to realize that inventories are air quality management tools and as such they provide broad estimations for wide areas, whereas measurements give more site specific information," said Robert Field.
Environmentalist Linda Baker with the Upper Green River Basin Alliance said inaccurate emission inventories could explain why high ozone occurred in the basin last winter even as Wyoming regulators said emissions had decreased.
"We can learn from this study," she said.
The Denver-based petroleum industry group Western Energy Alliance played a role in helping government regulators to develop emission inventories. Emissions sources outside the oil and gas industry could have been responsible for the air pollution measured, suggested Kathleen Sgamma, the group's vice president of government and public affairs.
"We're working to understand that and make sure those assumptions are good ones and provide input to the study as well," Sgamma said.
Steven Dietrich, air quality administrator for the Wyoming Department of Environmental Quality, said he hadn't yet reviewed the paper and couldn't comment on it. His counterpart in Colorado, Will Allison, said he planned to review the study.
"We welcome studies that help increase understanding of the potential air quality issues associated with oil and gas development," Allison said.