As Utah’s Great Salt Lake shrinks, leaving more of its beach area exposed, concerns are growing about dust emitted from the dry lake bed. But scientists lack the data to fully understand what pollutants are present in these airborne sediments.
Researchers at the University of Utah are trying to answer this question, and the latest findings are worrying.
Sediments on the lake’s exposed playa are potentially more harmful than other major dust sources affecting Wasatch Front air quality, according to a study published online recently in the journal Atmospheric environment.
These sediments, when pulverized, showed higher levels of reactivity and bioavailability compared to sediments collected at other locations upwind of Utah’s major population center along the Wasatch Front. Chemical analysis also indicated the presence of numerous metals and levels of arsenic and lithium exceeding regional residential soil screening levels established by the U.S. Environmental Protection Agency.
“We’re talking about a very large dust source located next to a very large population, and there are elevated levels of manganese, iron, copper and lead. Lead is a concern for developmental reasons,” said senior author Kerry Kelly, a professor of chemical engineering. “Manganese, iron and copper are transition metals and are known to be very irritating to the lungs. Once irritation occurs, that can lead to this whole inflammatory response. And that’s part of the problem with particulate matter and its adverse health effects, like asthma.”
The Great Salt Lake is a terminal body that receives runoff water from a vast drainage basin spanning northern Utah and parts of three other states. Metals from natural sources and human disturbances are pushed into the lake by inflows or atmospheric deposition, and these materials accumulate on the lake bed. The potential for harmful dust pollution has become a priority for Utah state officials, who released a list of priorities aimed at addressing the problem.
Another recent study led by sociology professor Sara Grineski found that lakebed dust disproportionately affects disadvantaged neighborhoods in Salt Lake County.
In a separate, soon-to-be-published study led by the lab of U biologist Michael Werner, another team of researchers characterized the levels of toxic metals deposited in submerged lakebed sediments sampled during the lake’s record low-water year of 2021 and looked at how these levels have changed since Utah’s mining-era years. Concentrations of some metals, such as lead and zinc, appear to have declined, likely reflecting the region’s declining mining activity, while mercury levels have, surprisingly, increased.
Researchers cautioned that they cannot conclude whether these pollutants are actually being blown into populated areas during wind events because monitoring equipment to capture that dust has not yet been adequately deployed downwind of the lake. Most high wind events arrive from the southwest, blowing for several hours from the lake northward to Weber or Box Elder County, before shifting south as the front passes.
To conduct the published study, Kerry Kelly’s lab, which specializes in air quality, collaborated with researchers at the University of Utah’s College of Science. They examined sediment samples previously collected from the Great Salt Lake and compared them to sediment from other Great Basin dust sources, namely Sevier Lake, Fish Springs Lake and the Western Desert in western Utah and Tule Lake in northeastern California. These locations are known to contribute to dust pollution reaching Salt Lake City.
Over the past few years, co-author Kevin Perry, a professor of atmospheric sciences, has systematically collected exposed lakebed sediment, cycling hundreds of miles. His previous research has identified “hot spots” on the beach that appear to be enriched with potentially toxic elements.
According to Perry, only 9% of the exposed lake bed, or 175 square kilometers (about 43,000 acres), emits dust from areas where lakebed crusts are disturbed. The rest of the playa is covered by a natural hardened layer that holds sediment in place. Perry’s ongoing research examines what happens to the playa crusts over time. He said his initial findings indicate that the broken layers reestablish themselves fairly easily, suggesting the playa’s threat to air quality may not be as severe as previously thought.
The latest study is the first to analyze the “oxidative potential” of dust, a measure of its ability to react with oxygen.
“When you inhale something that’s really reactive, it will interact with the cells inside your lungs and cause damage,” Kelly said.
In the lab, the team aerosolized sediment samples to isolate particles that are small enough to be inhaled and lodge in lung tissue — those smaller than 10 micrometers, or PM10.
These particles were captured on filters and subsequently analyzed using a method called inductively coupled plasma mass spectrometry to determine their elemental composition and other tests to determine their oxidative potential (OP) and bioaccessibility.
“We’ve come up with a way to dissolve the metals using increasingly more caustic acids to determine at what level these metals are leaching out of the particles,” Perry said. “It turns out that the Great Salt Lake dust has more leachable metals that are bioavailable than we would wish.”
Meanwhile, high levels of OP were detected in dust associated with certain metals, including copper, manganese, iron and aluminum.