Airborne dust pollution has been a concern for Utahns for several years, especially with the exposed lakebed of Great Salt Lake potentially becoming more hazardous as the lake dries. Natural dust blows from the Great Basin and settles along the western edge of the Wasatch Front, Utah’s major population center, and the surrounding mountains. While airborne, the dust mixes with local human-made materials, potentially contaminating the nearby watershed and resulting in other negative consequences, according to new research from the University of Utah that investigates the influence of urban environments on transient dust.

A study team led by U atmospheric scientist Kevin Perry and Jeff Munroe, a geology professor at Middlebury College, considered Earth’s “Critical Zone,” a near-surface layer where organisms interact with rock, air, soils and water. Dust processes such as deposition, erosion and transport influence the Critical Zone.

Dust particles are typically diverse in their composition, as they are influenced by natural environments. However, agriculture, grazing, off-roading, construction, mining and other human activities alter the dust composition, with important implications for places like Utah’s populated Salt Lake Valley.

“The problem is that there are lots of dust sources in the urban area, and when it’s windy and it’s picking up dust from Great Salt Lake and other places upstream, it gets mixed in with this local dust that has a lot more junk in it,” Perry said. “So if we think about the contaminants of concern in Great Salt Lake dust, and then you add in additional contaminants from the local dust, it just makes it that much more potent, and not in a good way.”

Home to 2.5 million people, or three-fourths of Utah’s population, the Wasatch Front is particularly susceptible to dust pollution, so it provides an ideal laboratory for investigating interactions between natural and urban dust, according to the study, which was funded by the National Science Foundation.

“Our dust comes from various sources. We have natural sources like the West Desert, the Bonneville Salt Flats, Sevier Lake, but then we also have a lot of dust from Great Salt Lake and anthropogenic dust sources, quarries at Point of the Mountain, the Staker quarry in North Salt Lake,” said co-author Derek Mallia, a research assistant professor of atmospheric sciences. “This can be locally sourced, but you can also get dust impacts from sources on the other side of the Great Basin. An artifact of being on the eastern side of the Great Basin is we’re just downwind of a ton of dust sources.”

The research team analyzed 29 dust samples collected by Munroe during four separate seasonal periods from 2020 to 2022. These samples were sourced from five passive collectors spanning 500 square miles west of the Wasatch Front, two inside Salt Lake City and Provo, and another at the head of Little Cottonwood Canyon, the ski destination just outside the city.

Part of a long-running project Munroe leads called DUST ^2, or Dust Squared, the team collected dust samples with a low-tech improvised system that uses trough-lined trays filled with large glass beads. Munroe has installed the equipment at mostly mountaintop sites around the Southwest, including the eight used in the study.

(Click here to view a scenic video tour Munroe conducted of all 20 collection sites in Utah, Nevada and southern Idaho in October 2024.)

The trays capture whatever particles fall into these devices. Researchers periodically retrieved the beads and washed off the dust, which they analyzed to determine their geochemical composition, mass flux, color and grain size.

“The dust in the city was way more contaminated with all sorts of metals and other sorts of things than the natural dust,” Perry said.

Their results identified higher concentrations of zinc, calcium, molybdenum, cadmium, copper, lead, cobalt and arsenic in the urban dust. Many of these elements can be traced to mining and smelting, vehicle emissions and heavy industry. Of note, arsenic and cobalt concentrations exceed the U.S. Environmental Protection Agency’s Regional Screening Levels. Moreover, zinc, calcium and copper are particularly harmful for surface waters in the Wasatch Front region.

“A lot of the dust ends up in the snowpack, and then when the snowpack melts, it runs off into the waters,” Perry said. Research team member Greg Carling, a geology professor at Brigham Young University, is analyzing spring runoff from the Wasatch to measure the influx of metals it carries into streams and ultimately into Great Salt Lake.

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The study, “Mixing of natural and urban dust along the Wasatch Front of northern Utah, USA,” appears in the Jan. 31 edition of Scientific Reports. The lead author is Middlebury’s Jeffrey Munroe, who has a long history of collaborating with Utah scientists, and co-authors include U geology research professor Diego Fernandez.

Banner photograph captures a dust plume blowing into Salt Lake City on the morning of Jan. 20, 2025. Strong north winds carried dust off exposed playa in Great Salt Lake’s Farmington Bay into Utah’s most populated urban area. Photo credit: Jim Steenburgh.

• Brian Maffly Science writer, University of Utah Communications
  801-573-2382 brian.maffly@utah.edu