United States Department of Transportation
i
Quantifying Bioavailable Metals and Potential Dust Emissions from Highway-Related and Desert Sediments at Lordsburg Playa, New Mexico
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2021-11-01
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[PDF-6.79 MB]
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Corporate Contributors:United States. Department of Transportation. University Transportation Centers (UTC) Program ; United States. Department of Transportation. Office of the Assistant Secretary for Research and Technology ; United States. National Aeronautics and Space Administration ; United States. National Science Foundation
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Edition:Final 01/01/2018–12/31/2020
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Abstract:Lordsburg Playa, a dry lakebed in the Chihuahuan Desert of southwestern New Mexico, is crossed by Interstate 10 (I-10). Clouds of dust blowing from the playa onto the highway represent an acute traffic safety hazard, making I-10 at Lordsburg Playa the deadliest stretch of highway in the United States for dust hazard. Metals contained in Lordsburg Playa dust may represent an additional health risk to motorists and others exposed to them. The research team performed field investigations at Lordsburg Playa to assess land-surface conditions contributing to dust emission, quantify dust emissivity of playa surfaces using a portable in-situ wind erosion laboratory, and collect playa materials for subsequent analysis and modeling. Threshold friction velocities for dust entrainment ranged from < 0.30 ms−1 for delta and shoreline areas to > 0.55 m s−1 for ephemerally flooded playa areas; mean PM10 vertical flux rates ranged from < 500 μg m−2s−1 for ephemerally flooded playa areas to ~25,000 m−2s−1 for disturbed delta surfaces. The unlimited supply of coarse sediments along the western playa shoreline may contribute particles triggering dust events; this zone should be a focus area for dust mitigation efforts. If playa surface crusts become disturbed, loose sediment underneath is revealed, increasing dust emission potential; thus, activities on the playa that degrade the crust should continue to be restricted. Playa sediments generally were rich in silt, composed of minerals common to regional playas, and contained up to ~20 ppm bioavailable Pb, ~1830 ppm bioavailable Cu, and ~4690 ppm bioavailable Zn (possibly reflecting traffic-related emissions deposited near the highway). Researchers combined two numerical models, the Single-Event Wind Erosion Evaluation Program and the American Meteorological Society and U.S. Environmental Protection Agency Regulatory Model, to estimate the generation and dispersion of dust and PM10 from key hotspots during two typical dust event days using data from field and laboratory tests, soil and land databases, and on-playa weather stations. Results from modeling were consistent with observations from traffic webcam photos and visibility records from meteorological sites. The combined models predicted transient dust PM10 concentrations of up to ~200,000 μg m−3 could impact I-10, presenting acute but short exposures to dust and airborne metals at the highway, although these brief exposures are not likely to significantly impact the long-term aerosol inhalation burden to anyone caught in a playa dust event.
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