Dust

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Dust

From stardust to the Dust Bowl to what’s under your bed, dust is a ubiquitous part of life. Here, we learn what DUST means to modern-day Utahns.

If you live along the Wasatch Front, you’ve experienced this: windy days where you can’t help but think you’re stuck in the middle of a desert sandstorm. Highways close due to high winds and reduced visibility. School children are kept inside for recess. The air quality monitors show increased levels of particulate pollution, and sensitive populations are advised to remain indoors. A dust storm is blowing through. But where is it coming from? And what the heck is it that we’re breathing?

Utah’s maven of dust

Dr. Maura Hahnenberger, an assistant professor in the Geosciences Department at Salt Lake Community College, has become Utah’s maven of dust. She moved to Utah in 2001 to study meteorology and ski. Despite the air quality problems that almost drove her from the state several times, she remained dedicated to research and educating people about Utah’s air quality.

Hahnenberger’s research has the answers to our questions.

Hahnenberger wanted to get into research that really impacted people’s lives and health. In 2009 she started noticing the frequent dust storms. This piqued her interest and she was able to start a research project focusing on dust in the eastern portion of the Great Basin, in western Utah. Her research, primarily based in Utah, has drawn comparisons to similar dust problems in California, Nevada and the Middle East.

Dust events concern people in three major ways, says Hahnenberger: air quality, transportation accidents, and increased snowmelt. Health impacts are a clear concern for two criteria pollutants, PM10 and PM2.5. During dust events, decreased visibility causes transportation accidents. And dust deposition on snowpack increases snowmelt rates, which exacer­bates problems of early snowmelt caused by climate change.

Hatu winds

In 1967, meteorologist Mark Eubank joined the KSL Channel 5 News Team. He became  known for his extreme enthusiasm for weather that would usually include a variety of sound effects, and was famous for wearing a white sports coat throughout a broadcast preceding or during a snowfall. Eubank was also passionate about wind. He was fascinated by the strong south and southwesterly winds that would bring significant dust storms up to the Wasatch Front. He called these winds “Hatu” winds (Utah spelled backwards).

These Hatu winds typically precede storm fronts, and blow south to north or northwest. As these winds travel along the north/south-trending Great Basin ridges they pick up speed and fine sand, reaching speeds of over 90mph in some instances. Hatu winds peak in the springtime, with a secondary peak in August and September. Just as geography helps create strong inversions during the wintertime, geography plays an important role in declining air quality due to dust storms. The mountain/valley topography creates terrain that channels and funnels dust-bearing winds towards Salt Lake City.

Where does the dust come from?

Human-disturbed areas and barren playa (dry lake bed) surfaces are the two primary dust sources, according to Hahnenberger’s research. To identify significant dust sources she and other researchers look at satellite imagery from dust event days. From the plumes in these images they are able to pinpoint where the dust originates and how far it travels. They have  identified playa surfaces at Sevier Dry Lake, Tule Dry Lake, the Great Salt Lake Desert and the Milford Flat burn area.

Sevier Dry Lake, located in the Sevier Desert in Millard County, causes the most trouble for the Wasatch Front. Like the Great Salt Lake, Sevier is a remnant of Lake Bonneville, fed primarily by Sevier River. The lake has been mostly dry throughout recorded history, due to diversions of water upstream for farming.

The Millford Flat fire of 2007 remains the largest wildfire in Utah history. It was started by lightning on July 6, near Millford, Utah (about three hours southwest of Salt Lake City). Fueled by drought, high winds and an abundance of dry weeds, the fire burned about 567 square miles. Firefighters assigned to the area claimed it was the fastest-moving fire they’d ever seen. It led to fatal wrecks on I-15, loss of several structures and numerous evacuations. Efforts to rehabilitate the extensive damage to the land, to minimize long-term ecosystem damage, were challenging due to the complex soil patterns and low moisture conditions in this region.

The management team drilled, tilled and chained the surface of the land extensively in order to re-seed the area, but unfortunately hardly any of the seeds established, leaving loose, disturbed soil over a foot deep in some areas as warm and dry conditions persisted for about a year after the fire. Ten years later, this dust continues to be stirred by the winds, leading to the dust storms we see in Salt Lake City each year.

What’s in the dust is what really matters

Hahnenberger’s research has shown that the composition of dust influences air quality, which impacts human health and how ecosystems function. Local research has been able to identify unique chemical fingerprints in each dust site observed.

Dust from Southwest Utah and deposited in the alpine ecosystems of the Wasatch Mountains contains elevated levels of potentially hazardous elements that are, for the most part, naturally occurring in soil and sediment, but can also be elevated as a result of human-influenced deposits (such as mining) over decades.

Fugitive dust from local sources such as Geneva Rock, Kennecott, and other gravel pits is often composed of heavy metals, including mercury, uranium and arsenic. Crystalline silica may also be present in the dust from these sources and can cause chronic respiratory illness which has been shown to lead to cancer.

These local sources contribute to those days when dust can be seen throughout the valley, but also create a more frequent impact on neighbors living within close proximity to the sources. Permitting requires these sources to implement dust mitigation strategies, including watering to keep soil in place, paving access roads where possible, re-vegetating, and curtailing operations when specific weather conditions persist. Construction sites as small as a quarter of an acre are required to mitigate dust.

Though these strategies meet the definition of Best Available Controls, sometimes local weather prevails and the control measures aren’t enough to prevent neighbors from being impacted. For example, watering might not be effective when the wind reaches over 25mph. Areas surrounding Geneva Rock see average winds above 25mph often, due to the topography of the land.

Neighbors and advocates alike claim further measures must be implemented or operations should cease. The rest of the valley may only be affected by dust just a few times per year, but neighbors close to these local sources can be affected daily.

The Great Salt Lake, a great source of dust

Scientists and state researchers are closer to figuring out what’s blowing in and from where, but can’t quite pinpoint exactly how much dust comes from the Great Salt Lake versus other sources. What they do know is that dust storms from a drier Great Salt Lake are of greater concern because of the hazardous elements beneath the surface and on the shore.

Decades of heavy metals and other toxic substances have built up, becoming trapped in the sediment. Even if only a small portion of a dust storm’s source comes from the Great Salt Lake, what’s in the dust could be especially problematic for local health.

Mercury is of greatest concern. Farmington Bay is one of the first areas to dry out when lake levels drop, and the Bay’s dust samples reveal about double the amount of mercury measured in other parts of the lake. Researchers suspect the increased levels of mercury are due to the area’s industrial past—smelters that processed ore on the south shore of the lake and along the banks of the Jordan River, or the Sewer Canal, where oil refineries and other industrial sites once discharged waste into the Bay.

The Great Salt Lake dry-up: What causes the decline in lake levels?

As the level of the Great Salt Lake continues to decline, the threat to air quality rises exponentially. Researchers look to three main causes: weather, climate change and consumptive water use.

Lakes generally shrink and grow with natural climatic variation. A drought here and a big winter there will cause fluctuation in lake levels each year. But many of the saline lakes across the globe are shrinking at alarming rates, and the Great Salt Lake is no different.

In contrast to climatic variation, water withdrawals for human use exert a sustained reduction in lake levels, and modern civilization has significantly reduced the size of the Great Salt Lake. In October of 2016, the lake reached its lowest level in recorded history. Since 1847, the Great Salt Lake has declined to about half its historic size. Most of this decline can be attributed to human water use—taking water out of rivers and streams for use in industries, farms and homes. The future of further decline of the lake level remains unclear, but researchers are confident that with decline, Utah will experience worsening air quality, some using the words “disastrous levels of air pollution.”

Utah has examples to learn from. Owens Lake in California was desiccated by 1926, when diversions from the Owens River were made for the city of Los Angeles. Owens Lake is the largest source of air pollution in the United States and the ongoing cost of remediation is formidable. Drying lakes, like Owens, cause major respiratory health problems for nearby populations.

Like Owens, the Great Salt Lake is a closed basin, meaning it doesn’t have any outlets; the only way water leaves the lake is through evaporation. But it suffers from decreased input. Owens Lake was desiccated by human diversions. Similarly, the amount of water lost in the Great Salt Lake can be calculated by looking at the history of agriculture and urban growth.

The drying lake is the perfect recipe for dust storms. The lakebed is comprised of fine silt and salts deposited by streams over millennia. The lakebed is more prone to create blowing dust than surrounding land area. The finer the silt, the easier it is for the wind to blow it around. Not much vegetation is able to grow in the salty environment, making it even easier for the silt to become airborne.

Further challenges to Great Salt Lake

The Bear River Development project, designed to support the state’s growing population and water consumption needs, would dam and divert more water from one of the Great Salt Lake’s main feeds. The Bear River currently provides around 60% of the water flowing into the lake. The Bear River Dam would drop the lake level by an estimated eight and a half inches, or roughly 30 square miles more of lakebed. Environmental advocacy groups say this figure is potentially much higher, some claiming upwards of over two feet.

This decrease would have the most drastic effect across the Bear River Bay, where the lake is very shallow to begin with. Critics of this project say policymakers should focus on taking less water, not more, from the Great Salt Lake.

Consumptive water use

Some of the water we use, such as that in toilets and showers, flows into a sewer and then on to a wastewater treatment plant. About 71% of wastewater along the Wasatch Front is cleaned up and then deposited into Great Salt Lake.

Consumptive water use, on the other hand, takes water out of the system. This includes water for irrigation, such as lawns and crops. Much of this water evaporates, or is absorbed by plants, preventing it from recirculating to a source.

With Utah’s growing population and plans to build a large diversion on the Bear River sometime in the future,  the Great Salt Lake will take the biggest hit. Researchers say that with a changing climate and human developments, it’s quite possible the lake can go dry. The timeframe remains unclear.

Climate change

Research has demonstrated that consumptive water use, rather than long-term climate change, has greatly reduced the Great Salt Lake. However, a changing climate shouldn’t be ignored. A warming trend in the region is only expected to get worse. Continued warming means further evaporation, and the only way for water to go out of the Great Salt Lake is evaporation.

The elephant in the room: alfalfa

Statistics show Utahns use far more water than our counterparts in other population centers in arid Southwestern states, such as Las Vegas and Tucson. But even if Utahns began to conserve more and reduce water use by 10%, it would likely be offset by rapid population growth. This is a difficult problem, but it certainly doesn’t mean Utahns should abandon conservation. Conservation is the preferred alternative to spending billions of dollars on large water projects.

Policymakers should focus on better land-use planning and reducing urban sprawl. Individuals can focus on re-landscaping yards, replacing lawns with drought-resistant plants to reduce water use or food-producing crops protected by mulch.

A more difficult—and consequential—challenge will be to address agricultural water use. Utah’s hot and dry climate requires a much greater share of water for farmers to grow profitable crops. In fact, an estimated 82% of Utah’s developed water resources go to agriculture—and half of that, to one particular crop: alfalfa hay, which alone consumes more water each year than all the cities and towns in Utah combined, according to the Utah Foundation. Much of the alfalfa is shipped to China, where it supports that country’s growing dairy market.

But agriculture isn’t the only industry taking a toll on the Great Salt Lake. Mineral extraction and other industries require a lot of water to operate successfully. And most of these industries ramp up production during dry conditions. And just like extraction industries, watering, whether it’s for farming, or lawns and gardens, requires more water due to evaporation when temperatures rise. Abnormally hot and dry weather will continue to impact the level of the Great Salt Lake.

How to protect yourself during dust events

Especially for those in the “sensitive” population, it’s important to plan ahead for a dust event. Since they typically precede a storm front, local weather forecasters have become better at predicting dust events. And since dust events are visual, you can see with your own eyes when it’s happening.

It’s the regular air pollution drill: Keep school children indoors for recess during periods of elevated dust. People with pre-existing cardiovascular and respiratory conditions should also remain indoors. Limit outdoor activity. If you must be outdoors for extended periods of time during a dust event, wear a mask that adequately covers your nose and mouth.

And for everyone—neglect not the obvious: Make sure all windows are closed. No sense reactivating the storm later when you vacuum, dust and sweep.

Reduced visibility during dust events is especially problematic for traveling, as visibility rapidly declines, affecting  roads, highways and airport runways. Proceed with greater-than-usual care.

When in doubt, check the Utah Air App, or the Division of Air Quality website for current air quality conditions at air.utah.gov.

And if you have an opportunity to share information about the importance of the Great Salt Lake in regard to air quality, to say nothing of its many other invaluable qualities, speak up. Knowledge just may save the day—and the health of those to come.

Ashley Miller, J.D., is the program and policy director for Breathe Utah. She is a member of the state’s Air Quality Policy Advisory Board and is also on the Salt Lake County Health Department Environmental Quality Advisory Commission.

 
 
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