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Antelope Island State Park • The weather was perfect. Temperatures in the low 90s. Clear, sunny skies. A slight breeze.

It's the kind of weather that makes you want to ride your bike, go for a swim — or fly an ozone-sniffing kite.

The half-dozen visitors in shorts and T-shirts who arrived at the gates of Antelope Island a few weeks ago with folding tables, canopy tents and sacks of granola bars in tow could have been headed out for a day on the shores of the Great Salt Lake.

But their "kite" is actually an aerostat — essentially a tethered balloon with a sail that catches the wind to help it fly higher. And rather than picnic, they planned to dedicate their day to an unprecedented study of Utah's atmosphere and, more specifically, air quality.

Flying the aerostat requires a certain set of conditions — some wind, but not too much. Likewise, if the kite is going to catch any of the ozone they're after, the researchers need to set up shop on sunny days.

This summer, when all the right conditions come together, professors and graduate students from the University of Utah, Weber State University and Utah State University head to the shores of the Great Salt Lake to fly their aerostat with the goal of answering a previously unexplored question: Why is so much more ozone, a pollutant generally associated with hot, smoggy cities such as Los Angeles, found over the Great Salt Lake than on the Wasatch Front?

On smoggy days, ozone levels are nearly three times as high over the lake as along the neighboring Wasatch Front.

Together with funding and assistance from the Division of Air Quality, the group intends to map Utah's summer skies to track the perplexing pollutant.

Their effort, they hope, will shed light on the origin of summer ozone in the state — the first step in finding a more efficient means of addressing one of Utahs' top health concerns.

"We know the photochemistry will be different over the lake," said John Sohl, a physics professor at Weber State University. "We just don't know how."

By the time temperatures cool this fall, the scientists will have collected more data on summertime ozone than Utah air-quality watchdogs have ever had.

Mapping the skies • Sohl and his fellow researchers are tackling an apparent quirk of chemistry that has upended conventional wisdom about pollution on the Wasatch Front.

The breakthrough came several years ago, when researchers discovered that the majority of the particulate pollution that plagues northern Utah in the winter was not directly emitted by cars and other sources, as once assumed. Rather, the pollutants that bottle up under winter inversions are a result of a chemical reaction among precursor pollutants, UV light, and, among other factors, salt from the Great Salt Lake.

The interaction isn't fully understood yet, but Sohl said that research got scientists wondering how the lake might impact ozone formation in northern Utah during summertime heat waves.

While the effect of nearby mountains blocking the movement of pollution is well-documented in research from Los Angeles, Sohl said, having a large saline lake and other nearby features such as the salt flats are unexplored variables.

"The giant lake is unique to this situation," Sohl said, "and no one really knows" how the lake impacts ozone formation.

But data already available suggest the lake impacts the airshed above it.

During an episode of high ozone the last week of June, for example, ozone levels at Salt Lake City's Hawthorne Elementary topped out one day at 83 parts per billion. But on Fremont Island, 10 miles west of Roy in the middle of the lake, ozone levels hovered above 90.

An invisible killer • Unlike particulate pollution — the much-despised culprit behind Utah's wintertime inversion woes — ozone is largely undetectable to the human senses.

"The trouble with ozone is: It's killing you and you can't see it," Sohl said. "When you're dying in the winter, at least you know why."

Ozone is a pollutant that isn't, for the most part, emitted directly into the atmosphere. Instead, ozone forms when certain chemicals in the air interact with ultraviolet light from the sun.

That makes ozone especially problematic. It's most concentrated in the summer, when people are most likely to be outside enjoying the nice weather, said John Horel, an atmospheric scientist with the University of Utah, the lead institution on the project.

Certain precursor pollutants such as nitrogen oxide and volatile organic compounds — groups of chemicals emitted by everything from the usual suspects, including cars and factories, to less-blamed homes and animals — contribute to the formation of ozone.

That's why big cities such as Los Angeles are known for their trouble with ozone, and why small rural towns generally are not.

Ozone, a respiratory irritant, can significantly impact sensitive populations, including young children, the elderly and people with heart disease or asthma. But healthy people aren't immune.

"Healthy people go out and exercise," Sohl said, "but we're fast-tracking ourselves to becoming sensitive groups."

Terabytes of data • In what Sohl characterized as a "massive" study of the airflow and chemistry over northern Utah, researchers have outfitted cars, planes, even trains with sensors to detect ozone and precursor pollutants.

In addition to the continuous data from fixed weather stations and from sensors placed aboard a TRAX light rail car and a KSL traffic helicopter, the team members also have four ozone-detecting cars they drive around the valley and a small unmanned airplane at their disposal.

And then there's the aerostat, which university professors and graduate students launch every hour, on the hour, from the shore of the Great Salt Lake ­— as long as the weather holds.

When they wrap up the sampling at the end of August, the team will have collected whole terabytes of data.

New technologies have made data collection much easier, Horel said.

It's not just the EPA-regulated lab equipment — although the researchers have that, too — but also contraptions such as a wind-tracking laser and even twice-daily data dumps from a satellite.

They also are using some custom-built equipment: everything from simple point-and-shoot cameras hacked to collect thousands of images and accommodate extra batteries, to the custom Atmosniffer, a highly sensitive air-sampling device. The Atmosniffer, which resembles a jumble of spare parts and loose wires in a Styrofoam box, was designed and patented by students at Weber State University and recently purchased by NASA.

"The easiest way to sum it up — we'll have more data collected during this past summer than has ever been possible before," Horel said.

Their hypothesis — Sohl really prefers the word "guess" — is that the high levels of summertime ozone along the Wasatch Front are the result of a complex system.

In the morning, he said, local winds blow precursor pollutants from the cities out over the lake, where they are exposed to high levels of ultraviolet light. Ozone forms as the air warms and rises, and then as the day progresses, additional winds and mixing air push the ozone back over the Wasatch Front.

Preliminary data have found evidence of such a wind pattern, said Seth Arens, a Division of Air Quality scientist collaborating on the study. On days of high ozone levels, sensors throughout northern Utah detect a "wave" of ozone that flows from the Great Salt Lake to Salt Lake City and beyond.

But all of this is still, as Sohl says, just a guess for now. And the data the three-university team collects this summer may not be able to provide all the answers.

A new model • The researchers also hope to better understand the vertical profile of the air over northern Utah.

Cars and trains sample air quality more or less at ground level, aerostats gather samples at 500 feet above ground level, planes sample over 1,000 feet and mountain towers test even higher. With a seasonlong, three-dimensional snapshot of ozone in northern Utah, the scientists hope they will finally have the data they need to map where all it all comes from — and where it's going.

Imagine, Horel said, if your local news service could not only forecast the odds of afternoon thundershowers, but also help you figure out when and where you could most safely exercise on a summer afternoon.

Air-quality watchdogs welcome any new information, but worry about how the data might be used.

Utah Physicians for a Healthy Environment's Brian Moench likes the idea of modeling, but worries it might be used to excuse human-generated sources of ozone such as industrial smokestacks and vehicle tailpipes, which are still the main sources of precursor pollutants on the Wasatch Front.

"What I hope doesn't happen," he said, "is that whatever is learned is then used as some kind of excuse — attributing our problems to our geography."

Sohl doesn't believe that would happen. While there may be a natural component to ozone formation, he said, it is still widely understood that human activity has a significant impact on the development of smog.

Instead, he said, the model could help lawmakers design more-targeted, more-efficient regulations that may have better odds of addressing the ozone problem than the blanket rules currently in place.

"What you really want to do is find out what really matters," he said.

For example, one of the fastest-growing sources of precursor pollutants is restaurants — particularly those with grills or broilers — according to Bryce Bird, director of the Utah Division of Air Quality.

Already, certain state air-quality regulations attempt to keep restaurant emissions in check. But what if what really matters is when they actually turn on their grills? Sohl asked. What if the data suggest restaurants just need to wait until after lunch before firing up the broiler?

"Maybe [what] we need to decide, as a group of people," he said, "is maybe we don't need this particular thing at lunchtime because we want better air."

That kind of targeted, data-based decision making has worked in the past, Sohl said. A similar ozone study in Los Angeles was instrumental in cleaning up what was once one of the nation's dirtiest airsheds.

"They figured out their air to clean it up," he said. "We can do the same thing."