Wind Dust: How cities change natural aerial particles

Air dust pollution is an increasing problem for residents of Utah and other western states. In particular, as the lake dries, the exposed lake bottom of Great Salt Lake can become potentially dangerous. Natural dust blows from the large basin and settles along the western edge of Utah’s major population centers and surrounding mountains.

In the empty borne, dust can mix with local human materials and contaminate nearby basins, with other negative consequences.

The findings can be found in Journal Scientific Reports.

A research team led by Utah atmosphere scientists Kevin Perry and Jeff Munro, a professor of geology at Middlebury College, saw it as a “critical zone” of the Earth, a near-surface layer where organisms interact with rocks, air, soil and water. Dust processes such as deposition, erosion, and transport affect the critical zone.

Dust particles are usually influenced by the natural environment, and therefore have a variety of compositions. However, agriculture, grazing, off-roading, construction, mining and other human activities change the composition of dust that has important implications for places like Utah’s populous Salt Lake Valley.

“The problem is, when there are a lot of dust sources in urban areas, and when it’s windy and picking up dust from Great Salt Lake and elsewhere, it’s mixed with this local dust with more junk,” Perry said. “So, when you think about the contaminants of concern to the dust in the salt lake, adding additional contaminants from the local dust makes it much more powerful and not a good way.”

With 2.5 million people, or three-quarters of Utah’s population, the Wasatch Front is particularly susceptible to dust pollution, so research has shown that it provides an ideal lab for investigating the interactions of nature and urban dust.

“Our dust comes from a variety of sources. We have natural sources like the western desert, Bonneville salt flats, and Lake Sevier, but there are also plenty of dust from Great Salt Lake and artificial sources of dust.

“This can be sourced locally, but you can also get dust impacts from sources on the other side of the basin. The artifact of being on the east side of the Great Basin is that we have turned a large amount of dust downwind.”

The research team analyzed 29 dust samples collected by Munro during four seasonal periods from 2020 to 2022. These samples were fed to five passive collectors, 500 square miles west of Wasatch Front, two Salt Lake City and Provo, and the other to the head of Little Cotton Wood Canyon, a ski destination just outside the city.

The team, part of the Munroe lead of a long-term project called Dust^2 or Dust Squared, collected dust samples in a low-tech improvisation system that used trays of trough lining filled with large glass beads. Munroe installed equipment at most summit sites in the southwest, including the eight used in this study.

(Click here to watch a scenic video tour that ran all 20 collection sites in Utah, Nevada and Southern Idaho in October 2024.)

The tray captures the particles that correspond to these devices. Researchers regularly retrieved the beads, washed away dust, and analyzed them to determine geochemical composition, mass flux, color and grain size.

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

Their results identified high concentrations of zinc, calcium, molybdenum, cadmium, copper, lead, cobalt and arsenic in urban dust. Many of these elements can be traced back to mining and smelting, vehicle emissions and heavy industry. Notably, arsenic and cobalt levels exceed U.S. Environmental Protection Agency’s regional screening levels. Additionally, zinc, calcium and copper are particularly harmful to surface waters in the Wasatch Front region.

“A lot of dust ends in snowman and when the snow melts, it runs into the water,” Perry said. Greg Carling, a member of the Research team, a professor of geology at Brigham Young University, analyzes the spring runoff from Wasatch, transports it to a stream and measures the metal inflow that eventually flows into Great Salt Lake.