Air Quality: The Great Salt Lake Ozone Study

By Seth Arens

Air pollution in Utah conjures up images of frosty January mornings, the “brown cloud” over the Wasatch Front, and days or weeks of sunless skies. High temperatures and unhealthy ozone pollution in last half of June 2015 reminded Utah residents that bad air pollution also threatens our health while we enjoy the sunny skies of a Utah summer.

Ozone pollution is primarily a summer problem which requires clear, sunny skies, high temperatures and the presence of nitrogen gases and volatile organic compounds. Similar to winter pollution, the geography of the Wasatch Front plays a role in forming summer ozone pollution. Scientists at the Division of Air Quality (DAQ) have generally recognized that the Great Salt Lake (GSL) is an important factor in forming and distributing ozone pollution.

The Great Salt Lake Ozone Study is a project funded by the 2014 Utah Legislature to understand how the meteorology of the Great Salt Lake affects ozone pollution along the Wasatch Front. Better understanding of how the GSL influences ozone pollution will help DAQ make regulatory decisions to improve summer and winter air quality and more accurately forecast high ozone days. The Study is a collaborative project between the University of Utah (Dr. John Horel), Utah State University (Dr. Randy Martin), Weber State University (Dr. John Sohl), and DAQ.

Periodic monitoring of ozone at temporary sites since 2010 revealed very high ozone concentrations near the GSL. Typically, ozone forms in urban areas or areas directly downwind of urban areas. Sites on islands in the GSL or adjacent to the GSL do not quite fit that paradigm. So why is ozone so high over the GSL?

The GSL potentially influences ozone formation in three ways:

1. The GSL is in a closed basin surrounded by mountains. During periods of high temperatures and calm winds during summer, there is a daily flow of air from the lake to the mountains in the morning and back from the mountains to the lake overnight. The flow of air around the GSL is similar to a sea breeze off the ocean. This daily movement of air recycles and builds up air pollutants emitted from urban activities.
2. Ozone formation requires strong sunlight. The GSL is near an all-time low elevation and there are hundreds of square miles of salt flats surrounding the lake. Salt flats reflect sunlight and may increase the rate of ozone formation.
3. The GSL is a very salty lake. Chlorine is a major component of salt water. When chlorine enters the atmosphere, it can help initiate the ozone reaction. The Great Salt Lake Ozone Study will focus on understanding how the meteorology of the GSL influences ozone pollution. Preliminary data will be collected to address the effect of the salt flats and chlorine on ozone formation.

Beginning in April 2015, 23 study sites were established around the lake to record the geographic variability in ozone and weather variables. Since ozone varies tremendously based on location, time of day, and weather conditions, mobile measurements of ozone will be made during three intensive study periods. The research team was fortunate to capture a period of high ozone pollution in June, and a third period is scheduled for this week. Several unique modes of ozone measurements will be used, including three vehicles traveling around the lake, a TRAX train, the KSL-5 News Chopper, a weather balloon, and an unmanned aerial vehicle (UAV).

Data collection will continue through September, with a final report scheduled for completion by the end of 2015.

Visit the University of Utah Great Salt Lake Ozone home page for air quality and meteorological observations in real time as part of our project. Visit DEQ’s website to learn more about the Great Salt Lake Ozone Project, air quality research projects funded by the 2014 Legislature, and July 2015 presentations of project results to date.

I have worked as an Environmental Scientist for the Utah Division of Air Quality since 2010. Since joining DAQ, I have worked in the Air Monitoring Section, focusing on special research projects on ozone pollution and maintaining the permanent air quality monitoring network. My academic background is in ecosystem ecology, and I have earned a B.A. from Colby College in Maine and an M.S. from the University of Alaska-Anchorage and the University of Utah. In life away from DEQ, I can be found backcountry skiing the slopes of the Wasatch and rafting the rivers of the West with my wife and twin children.