SALT LAKE CITY — It's no secret that the Great Salt Lake has been shrinking, dwindling to less than half its historical size, at one point, leaving about 800 square miles of barren lakebed.
As more of its beach becomes exposed, concerns ramp up around the dust emitted by the dry lakebed. But what pollutants are present in these airborne sediments and just how impactful are they to human health?
This is the question researchers at the University of Utah endeavored to begin answering through a recent study published in the journal Atmospheric Environment. They found that sediments in the lake's exposed playa (the bottom of an undrained desert basin that becomes, at times, a shallow lake) are potentially more harmful than other major dust sources impacting air quality across the Wasatch Front.
'Adverse health effects'
"What we did was we measured something called oxidative potential. That's a way to kind of get an idea of how irritating and how toxic those (sediment) particles might be," said Kerry Kelly, associate professor in chemical engineering at the U. and lead author of the study. "We separated particles into a size that you could actually breathe in and then we determined, sort of, how reactive they were. As people start to look into health effects, this is a logical first step."
Kelly and the research team harnessed exposed lakebed sediments systematically gathered by U. atmospheric scientist Kevin Perry.
For nearly a decade, Perry has logged hundreds of miles on his bike, identifying "hot spots" on the playa that appear to be enriched with potentially toxic elements.
"After we've collected the particles, we suspend them in either phosphite-buffered saline or a synthetic lung fluid, which is very much like what we have in our lungs," Kelly said. "We suspend it in that fluid and then we measure how it interacts, you know, how reactive it is."
The sediments from the Great Salt Lake showed higher levels of reactivity and bioavailability (the proportion of a substance that enters circulation when introduced into the body, enabling it to have an active effect) when compared to sediments collected from other spots upwind of Utah's major population center along the Wasatch Front.
Chemical analysis also indicates the presence of numerous metals, and levels of arsenic and lithium that exceed the U.S. Environmental Protection Agency's soil residential regional screening levels.
Kelly added the sediments contain elevated levels of manganese, iron, copper and lead.
"Lead is a concern for developmental reasons. Manganese, iron and copper, these are transition metals and are known to be very irritating to your lungs. Once you get irritation, 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," Kelly said.
Who's impacted?
While the study found sediments in the lake's exposed playa are potentially more harmful than other major dust sources affecting the Wasatch Front, Kelly said this isn't a doomsday scenario.
"It doesn't mean that the sky is falling and we're all about to die, so I just want to make that clear," Kelly said. "But it does mean that it's definitely worthwhile to further study it. And some of those further studies would entail needing to understand, like, is the dust actually making it to the population centers along the Wasatch Front?"
Another University of Utah study published in June that Perry was a co-author on did look at this, finding wind-carried dust from the exposed lakebed disproportionately impacts disadvantaged communities in the Salt Lake metro area.
The study states exposure to particulate pollution arising from dry portions of the playa is highest among Pacific Islanders and Hispanics and lowest among white people compared to other racial/ethnic groups.
"People here in Utah are concerned about the lake for a variety of reasons — the ski industry, the brine shrimp, the migratory birds, recreation — and this study adds environmental justice and the equity implications of the drying lake to the conversation," lead author Sara Grineski, a professor of sociology and environmental studies, said in a statement.
For the study, U. researcher Derek Mallia developed a model for predicting exposure levels for the three counties abutting the lake's east and south shores — Salt Lake, Davis and Weber, home to 1.8 million residents — under four different lake level scenarios. It used a weather model that simulated wind direction and speed, and included a wind-blown dust model, which measured how much dust is emitted from an erodible surface, such as the Great Salt Lake playa, and is primarily based on the wind speed and soil texture and characteristics.
Mitigating the dust, saving the lake
Perry said about 9% of the exposed lakebed (about 43,000 acres) emits dust from areas where lakebed crusts are disturbed.
The rest of the playa is covered in a natural hardened layer that keeps the sediments in place. Perry's ongoing research examines what happens to the playa crusts over time. He said his initial findings indicate the broken layers reset fairly easily, suggesting the playa's threat to air quality may not be as dire as previously thought.
"That natural crust that exists out on the lakebed ... does a really good job of limiting the dust emission," Perry said. "The best way to mitigate the dust is to put water back in the lake. If the hot spots are underwater, they don't blow. In short of having water, what I discovered is that rewetting and saturating the crust will actually reset it."
With this in mind, Perry is currently working on a project resetting the crust using freshwater from the Bear River, Weber River, brine solution from the southern and northern parts of the lake, as well as commercially available salt of magnesium chloride.
The bed of the Great Salt Lake near Antelope Island on April 20. (Photo: Tim Vandenack, KSL.com)
The crust can also be reset via natural rain or wind events that push water across the playa.
"What I discovered this year is that it's a lot easier to reset the crust than I thought, which means that every year, there are natural processes that reset the crust," Perry said. "So, that's a little bit of good news."
Perry and Kelly both reiterated that the Great Salt Lake's shrinking is not driven by drought or climate change. Instead, it can be boiled down to excessive water depletion.
"That actually makes me optimistic about the future of the lake — because we actually have control over how we value and how we use our water, and we can make policy changes to emphasize conservation and shepherding of water to the lake," Perry said.
"So, it's within the power of Utahns to actually save the Great Salt Lake and reduce these environmental problems, which is very different from other watersheds like the Colorado River, which is being decimated by climate change."
