A New Study Finds That Dust Blown Across U.S. Has Increased
WESTERN SAN JUANS – It’s a phenomenon many residents in the region know, anecdotally, to be true: The amount of dust being deposited by storms is on the rise. Now, a University of Colorado study is providing evidence this is correct.
The study, led by C.U. doctoral student Janice Brahney and recently published online in the journal Aeolian Research, found that the amount of dust being blown across large swaths of land in the Western U.S. has increased over the past 17 years.
To conduct the study, Brahney used calcium deposits as a means of measuring dust deposition around the country. Calcium, according to Brahney, can make its way into the atmosphere — before falling back to earth, along with precipitation — through a number of avenues, including coal-fired power plants, forest fires, ocean spray and, key to this study, wind erosion of soils.
The amount of calcium dissolved in precipitation has long been measured by the National Atmospheric Deposition Program, which first began recording the chemicals dissolved in precipitation in the late 1970s, when it began studying acid rain.
Brahney’s team reviewed calcium deposition data from 175 NADP sites across the United States between 1994 and 2010, and found that calcium deposition had increased at 116 of them. The sites with the greatest increases, the study found, were clustered in the Northwest, the Midwest and the Intermountain West, with Colorado, Wyoming and Utah seeing especially large increases.
“There was a lot of anecdotal evidence to suggest that [dust] has been increasing, and we have heard a lot of people commenting” on it, Brahney said in an interview with The Watch on Monday. “We haven’t had a way of actually knowing this for sure, so we thought we could use calcium records to determine if this is true. We were able to closely track the trends of calcium deposition, and it strongly suggests that calcium deposits are related to dust.”
The researchers were able to determine that the increase was linked to dust erosion because none of the other possible sources of atmospheric calcium — including industrial emissions, forest fires or ocean spray — had increased during the 17-year period studied.
“None of the alternative sources matched the variability or trends in the data,” she said.
It’s also likely, Brahney said, that the calcium deposition record underrepresents the amount of dust being blown around. That’s because the NADP network only measures dust that has collided with water in the atmosphere before precipitating to earth — not dust that is simply moved by the wind. And not all dust contains the same amount of calcium.
Besides the fast-melting effects it can have on snowpack in the Rocky Mountains, Brahney said the higher levels of dust can have a host of other impacts, including impoverished soils where dust is being lost. Wind tends to pick up the finer particles in the soils, and those are the same particles that have the most nutrients and can hold onto the most soil moisture.
“Dust storms cause a large-scale reorganization of nutrients on the surface of the Earth,” Brahney said. “And we don’t routinely monitor dust in most places, which means we don’t have a good handle on how the material is moving, when it’s moving, and where it’s going.”
Increasing amounts of dust in the atmosphere also can cause people living in the rural West a variety of problems, including poor air quality and low visibility. In extreme cases, dust storms have shut down freeways, creating delays and hazards for travelers.
The areas where dust travels are also affected, with effects both good and bad. For example, when dust is blown onto an existing snowpack, as is often the case in the Rockies, the dark particles that land there better-absorb the sun’s energy and cause the snowpack to melt more quickly. On the other hand, dust that is blown in also brings nutrients to alpine areas, and the calcium it contains can buffer the effects of acid rain.
In the future, researchers at Geological Sciences Associate Professor Jason Neff’s lab hope to get a more precise picture of dust movement by measuring the dust itself. In the last five years, large, vacuum-like measuring instruments designed specifically to suck in dust emissions have been installed at sites between the canyonlands of Utah and the Front Range. Once scientists have enough data collected, they’ll be able to look for trends in dust emissions without relying on proxies.
And, while the study has not concluded what the increasing dust may mean for the future, Brahney said iinspiring to conduct an investigation that helps confirm what people are talking about.
“It was exciting to find a way to actually look at what everyone has been noticing and be able to say yes, you are right,” Brahney said.