"Ozone concentrations in Summit County, at least in the Park City area, were similar to what we see in Salt Lake City," said Seth Arens, Department of Environmental Quality environmental scientist, at a Summit County Council meeting on Wednesday. "On most days that it was high in Salt Lake City, it was also high in Summit County. In fact, there were more moderately high ozone days in Summit County than in Salt Lake City."
Department of Environmental Quality has been monitoring ozone levels in Summit County since 2010. The highest levels of ozone last year were found in Parleys Summit, Snyderville Basin and Silver Summit.
The sites monitored in Summit County included Parleys Summit, Jeremy Ranch, Snyderville Basin, Park City, Silver Summit and Kamas.
The national standard for ozone levels is 75 parts per billion (ppb). Parleys Summit exceeded 75 ppb 10 days in 2012, with Snyderville Basin and Silver Summit trailing behind, with seven days of more than 75 ppb.
Salt Lake City also exceeded the federal standard on seven days last year.
Arens said the national standard will likely be soon lowered to between 60 and 70 ppb.
"If you look at the number of days greater than 70 parts per billion, there were more days that exceeded it in Silver Summit compared to Salt Lake City," Arens said. "If the national standard is lowered, Summit County will likely be put into a nonattainment area. And there's probably not a lot of ways to avoid that from what we've seen so far."
Nonattainment areas are places where pollutants exceed the regulated levels of ozone.
Wind patterns suggest that Parleys Canyon appears to be a corridor for the movement of air masses from Salt Lake City to Summit County, Arens added.
At 1 p.m. on Aug. 12, 2012, Salt Lake City reached a peak ozone concentration of 104 ppb.
"It was already quite elevated in the Summit County area with values in the 80s," he said. "At 3 p.m., the ozone was decreasing in Salt Lake City with 83 ppb."
During the same hour, Parleys Summit reached a peak of 94 ppb with elevated levels at other sites.
4 p.m., ozone began to decrease at Parleys Summit and Jeremy Ranch, while Snyderville Basin and Silver Summit reached their peak ozone levels for the day.
"And by 5 p.m., ozone started to decrease everywhere and reached a max concentration in Kamas," Arens said. "By looking at ozone data in this manner, it appears there is transport of ozone from Salt Lake City all the way to Kamas."
Like PM2.5, fine particles in the air measuring 2.5 micrometers or less that cause inversion in the winter, ozone is a secondary pollutant that is strongest during the summer.
"That means ozone is not emitted from a tailpipe or a smokestack," he said. "It's formed through complex chemical reactions in the atmosphere from nitrogen oxide and volatile organic compounds in the presence of strong sunlight. So even if you have all the right atmosphere chemistry going on, you aren't going to get a lot of ozone formation because you need a lot of ultraviolet radiation and sunlight to catalyze the reaction."
The increased levels of solar radiation at higher elevations could be a contributing factor to Summit County's ozone levels, Arens said.
"Since we sit about 2,000 feet higher than Salt Lake City, there is higher solar radiation," he said. "I found solar radiation here at Park City was almost 60 percent higher than Salt Lake City. This is important because you need strong solar radiation, and in particular, ultraviolet radiation, to catalyze particles. Without that, you wouldn't get any ozone formation."
Arens added that PM2.5 and ozone are caused by many of the same pollutants, so reductions that are now, or will be, in place should help combat both problems.
"By no means am I sitting here saying that's going to solve the problem, but there is a lot of overlap between the PM2.5 and ozone problems," he said.
Bo Call, Department of Environmental Quality air monitoring section manager, added that he doesn't know if there is a surefire way to control ozone.
"You are, and will be, subject to what comes up the canyon from Salt Lake City," he said. "Ozone will travel around, so it's not something you can just put your finger on and say, you made it, now you fix it. So the problem is not going to be initially solved at the local level."