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THERE’S SOMETHING IN THE SUMMER AIR: OZONE

SHARE THERE’S SOMETHING IN THE SUMMER AIR: OZONE

Scientists have confirmed what they've long suspected about hot-weather air pollution along the Wasatch Front:

- It forms in tunnellike patterns over major streets and freeways and gets caught behind highway sound barriers and big buildings.- It creates a massive ozone cloud that drifts back and forth between the Great Salt Lake and urbanized land masses to the east.

"We're kind of unique here from the rest of the country," noted Robert Dalley, manager of the state's Air Monitoring Center and supervisor of a five-day project in late July and early August that tracked pollution using an airplane, weather balloons and a roving van.

Wedged between two mountain ranges - the Oquirrhs to the west and the Wasatch to the east - metropolitan Salt Lake City in the summertime routinely finds itself blanketed with dirty air that has nowhere to go.

Hot, sunny and calm weather conditions create the ideal mix for the photochemical process that forms excessive ozone from pollution emitted by automobiles and some industries.

If ozone is good to have 40 miles high, where it filters out harmful ultraviolet rays, it's bad for life on Earth when it occurs in unnatural abundance.

"Down here at ground level it can damage lung tissue and cause breathing difficulties," said Dalley.

While Wasatch Front ozone in recent times has not reached the national health-hazard ceiling of 125 parts per billion, it has frequently come close, at 120 parts per billion.

"We're on the edge," said Dalley, explaining why studies like the one conducted by the state are important.

Data from the tests will go into a new series of complex three-dimensional computer models designed to help scientists understand how air pollution behaves along the Wasatch Front.

"If we have a model of how the ozone forms over the region, then we can use that model to simulate possible mitigation strategies," said Brock LeBaron, manager of the technical analysis section of the Division of Air Quality.

Remedies might include mandates for additional pollution-control devices on vehicles, better regulation of smokestacks and gas-pump nozzles designed to catch vapors that would otherwise react with sunlight and oxygen to form ozone.

LeBaron said the area's last serious ozone violations were in the early 1990s. Pollution-control measures have since curbed some emissions, but an ongoing population boom worries experts that standards might be exceeded again.

Dalley said the geography of the area causes special problems similar to urban coastal regions.

In the evening, air masses from Salt Lake and Davis counties are blown toward the Great Salt Lake, where pollutants go through a chemical reaction that creates ozone.

Unless winds are strong enough to push the ozone out of the valley, the cloud drifts back over cities on the lake's eastern shore as land masses warm up in the daytime and create updrafts.

Depending on weather conditions, the cycle can repeat itself for days on end.