Study quantifies role of oil and gas emissions in ozone formation along Colorado Front Range

Research to help shape efforts to reduce dangerous air pollution
ozone map

By Bob Berwyn
Emissions from oil and gas production along the Colorado Front Range are a significant, measurable part of the region’s chronic summer ozone problem, scientists concluded after taking a close look at air pollution during an extensive research project in the summer of 2014.

Ozone levels in the area often spike above 70 parts per billion, a level deemed by the EPA to be dangerous to human health and to the environment, causing respiratory problems and damage to plants. About 17 ppb of that ozone are produced locally; about 3 ppb come from oil and gas industry emissions, according to a new study, published in the Journal of Geophysical Research.

The researchers said their findings could help shape efforts to improve air quality in the region. Along with the volatile organic compounds released from oil and gas operations, nitrogen oxides from cars, buses and trucks are also a big factor. Any meaningful effort to improve air quality will have to address both sources.

“Chemical vapors from oil and gas contribute an average of 17 percent to local, chemically produced ozone during the summer,” said the study’s lead author, Erin McDuffie, a scientist at the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder, working in the NOAA Earth System Research Laboratory. “We should, along the lines of creating the most effective strategies, think about reducing both nitrogen oxides and VOCs from oil and gas,” McDuffie said, characterizing the findings as the “first peer-reviewed literature to quantify the link and make the direct connection” between oil and gas emissions and ozone formation.

“Seventeen percent is small but potentially still significant,” said Steven Brown, co-author and scientist at the NOAA Earth System Research Laboratory.

With more data coming from the coordinated 2014 research effort, researchers may be able to determine how oil and gas emissions may affect the number of days that ozone is above the standard. Brown said a network of observation sites between Denver and Fort Collins could also help inform efforts to improve air quality.

The new findings confirm the urgent need to address pollution from fracking, said Jeremy Nichols, director of WildEarth Guardians climate and energy program.

“It’s definitely not a surprise given all the studies over the years on the contribution of oil and gas to the Front Range’s ozone problem, but it is probably the most powerful indictment to date against the fracking industry,” said Nichols. “It also comes at a very urgent time. Not only is the state under the gun to strengthen air quality rules for the region after failing to meet the 2008 ozone standards last year, but people along the Front Range are looking to the state to take steps to meet the 2015 ozone standards. This study confirms the need for the state to stand up to the oil and gas industry more strongly than ever.  If they don’t, the Front Range stands to endure years of unhealthy smog with no relief in sight,” Nichols said.

Ozone pollution has frequently exceeded the EPA standard this summer, with five monitors —one at Chatfield, one in Adams Co., one at NREL, one at Rocky Flats, and one in Ft. Collins — currently in violation.

“We’re not talking about trivial violations, either,” he said, pointing out that the NREL monitor recently spiked with a reading of 80 ppb, well above the 70 ppb threshold.

The northern Front Range has seen a big boom in oil and gas activity in recent years, with the number of active wells nearly doubling to 27,000 between 2007 and 2015. State air quality experts have already used modeling data to determine that the oil and gas sector can be a significant source of VOCs for ozone pollution formation in certain weather conditions.

Ozone pollution is produced when sunlight sparks reactions between VOCs and nitrogen oxides. In cities like Denver, nitrogen oxides comes primarily from vehicle tailpipes. VOCs can come from both natural sources like trees and anthropogenic ones, like oil and gas activities.

McDuffie said the Front Range was good area to specifically study the role of emissions from oil and gas in the formation of ozone because there are few natural sources of VOCs during daytime hours when ozone forms, making the region potentially more sensitive to any oil and gas VOC emissions entering the air.

The study was also critical because on an average summer day, the region has a high natural background of ozone, up to 58 ppb from various sources, which is just 12 ppb below the EPA standard. That means there’s not a lot of room for locally produced ozone before the level is exceeded.

The study was part of a widespread effort to look at air quality along the Front Range, including the Front Range Air Pollution and Photochemistry Experiment (FRAPPE), and the Discover-AQ program. Altogether, the research should provide a much better understanding of Front Range pollution sources, said Gabriele Pfister, a scientist with the National Center for Atmospheric Research.

McDuffie’s study, combined with a large number of other studies the FRAPPE and DISCOVER-AQ Science Teams are working on, will eventually shed light into the sources and causes of high ozone pollution in the Front Range.

“Only if we understand these can we design appropriate measures to reduce pollution,” Pfizer said.

“There are a number of different sources in the Front Range, ranging from traffic and industry, to power generation and oil and gas, to agriculture. In addition we have pollution being transported into our region from upwind states or other continents,” she said, explaining the complexities of tracking ozone formation.

“How much the different sources contribute to ozone changes in time and space and transport. Mixing in the Front Range is extremely complex in the Front Range posing a high challenge on characterizing the driving factors behind ozone pollution. You can imagine, if you get it wrong where the plume from a specific source is transported to, your estimated contribution is wrong.

But with enough data and time, the scientists will eventually figure it out.

“We have an extremely comprehensive dataset of meteorological and chemical measurements, a number of teams working on different aspects of the study using different approaches and methods. All these work together and to some degree verify each other so that we can gain higher confidence in recommended emission control strategies,” she said.

To develop air quality improvement strategies, scientists use models to simulate reductions in various emissions sources to see how the changes affect ozone formation.

“Erin’s was one of the first studies that came out using FRAPPE data and gives a first estimate to how much oil and gas sources contribute to regional ozone,” she said. “Many others will appear over the coming months and year and add further understanding on the influence of oil and gas sources and all the other sources listed above.”

Pfister said the research isn’t just focused on oil and gas, which is only one of many relevant sources, including traffic, industry and power production.

“We need to take all of them under consideration as they all play together to give us the high ozone we don’t want,” she said.


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