State and federal scientists are trying to determine why so much air pollution builds up each winter in a rural area of Utah with few people.
The region is the Uintah Basin, an oil-and-gas rich patch in Utah's northeast corner bordering Colorado with a coal-fired power plant.
Scientists are not certain that drilling emissions or the Bonanza Power Plant cause the Uintah Basin's notoriously bad air during winter. The region's air pollution eases in summer.
The scientists from a number of government agencies and research institutions are trying to determine why snow on the ground in winter seems to produce so much ozone, the main ingredient in smog. The ozone readings can reach nearly twice the limit considered safe by the U.S. Environmental Protection Agency and can last for weeks at a time.
For many urban areas around the country, ozone is a problem during hot summers, not the cold of winter.
Scientists are at a loss to explain why ozone not only forms in winter in the Uintah Basin but does so at levels that far exceed those seen during summer months in urban areas.
Chemistry will be central to understanding the puzzle, said Brock LeBaron, deputy director at the Utah Division of Air Quality.
"You have some sort of chemistry going on with different emissions that can produce different end products," he said.
Last winter, Utah officials and scientists began intensively monitoring the basin's air quality. This winter they hoped to ramp up the study, but the ozone has largely disappeared owing to a dry season with little snow.
The weather has left little chemistry for scientists from the National Oceanic and Atmospheric Administration to study.
"We're not happy with the conditions right now," LeBaron said. "This is a very unusual year."
Ground-level ozone forms from a reaction of sunlight with air containing hydrocarbons and nitrogen oxides. When inhaled, the colorless gas can cause respiratory problems, congestion and worsen some pre-existing health issues.
Data from 2010 showed winter ozone levels in the eastern Utah basin were some of the highest recorded in the United States. EPA figures show basin ozone levels had reached 123 parts per billion, far higher than the 75 parts per billion deemed unhealthy.
Snow also appears to be a factor because it reflects energy from sunlight back into the air. When combined with high pressure, sun and snow turn the basin into a bowl that seals out cleansing precipitation and wind.
Pollution in the basin has lingered for as many as 40 days in the winter of 2010.
The study is monitoring weather conditions, including temperature, relative humidity and other factors. It's also logging ozone readings every few minutes at 10 locations.
