Curbing Wind-Blown Dust
|"We can watch the wind pick up soil, carry it in clouds miles above the ground, and then deposit dust over urban areas where it can cause respiratory problems," says ARS agricultural engineer Keith E. Saxton.
Saxton is speaking about a new computer prediction model for the Pacific Northwest's Columbia Plateau region. The model simulates dust storms from beginning to end by linking smaller models for wind erosion and dust emissions. Saxton and about 15 colleagues developed the model as part of the Northwest Columbia Plateau Wind Erosion/Air Quality Project.
The scientists are with ARS and Washington State University in Pullman and the University of Idaho at Moscow. They tested the model on a 50,000-square-mile section of the Columbia Plateau, using several previously recorded dust storms.
For those studies, "dust" was defined as particulate matter less than 10 micrometers in diameter—or PM-10. These particles are small enough to be drawn into the lungs. But more recent concerns about health problems have put the greatest focus on particles smaller than 2.5 micrometers—PM-2.5.
Often, about a third of the windblown soil particles caught in samplers are PM-2.5 in size. Other PM-2.5 sources include smoke from fireplaces, smokestacks, and fields that farmers burn to stop soilborne crop diseases.
"The Columbia Plateau is one of the world's largest areas of wind-blown volcanic soils," Saxton says. "These soils are extremely light and prone to forming dust clouds."
Farmers on the plateau typically grow winter wheat every other year. In the "off" year they leave the land bare to save soil moisture. But ARS agronomist Frank L. Young and several ARS and state scientists are developing crop rotations to keep land covered as much of the year as possible.
Saxton serves on the National Agricultural Air Quality Task Force charged with advising the Secretary of Agriculture on all aspects of air quality related to agriculture. This task force was formed in 1996 as ARS was beginning to expand its research on how agriculture affects air quality. Targets include not only dust but also odors, ozone, pesticides, and ammonia emissions from animal operations.
Following the task force's recommendations, the U.S. Environmental Protection Agency has formally agreed to work closely with USDA when air quality issues involve agriculture. This will help both agencies face the environmental challenges of the new century.—By Don Comis, Agricultural Research Service Information Staff.
Keith E. Saxton and Frank L. Young are in the USDA-ARS Land Management and Water Conservation Research Unit, 215 Johnson Hall, Washington State University, Pullman, WA 99164-6421; phone (509) 335-1552, fax (509) 335-3842.
"Curbing Wind-Blown Dust" was published in the March 2000 issue of Agricultural Research magazine.