Characterizing Dust Sources of southern Colorado Plateau Tribal Land
Dust particles of geologic origin are a widely dispersed component of Earth’s atmosphere, often observed as plumes originating from arid and semi-arid areas. Those observed on Native lands of the southern Colorado Plateau result in long-range dust transport during synoptic weather events. Resulting dust storms may potentially become common as a consequence of increased aridity from climate change, bringing about catastrophic phenomena that can damage infrastructure, degrade rangeland, and affect transportation through reduced visibility, with a potential to cause tremendous economic losses. Constituents in dust that are transported by these events and may affect human health are diverse, and include soil microorganisms, trace metals and metalloids, radioactive elements, silicates, and alkali salts. The Little Colorado River (LCR) in northeastern Arizona is an important regional source of windblown dust, and transports a large sediment load of sand and silt. A significant decrease in streamflow in the LCR occurred over the 20 century, due to warmer and drier conditions and water supply demands. Currently, only a short segment of the LCR channel, near its confluence with the Colorado River, flows year-round, leaving dry river sediment in and adjacent to most of the river channel during the windy spring. Wind-blown flood deposits from the desiccated river valley are now likely to be a significant source of dust contributing to “dust on snow” events in the southern Colorado Rockies. To estimate potential contributions to dust on snow from this source area, wind deflation was measured in the flood plain during the spring of 2010. Measurements provide an estimate of the volume of silt and clay-sized particles that were transported by wind during five major, well-documented dust events. Three playas associated with the river system contributed 4.41 km of dust during March and April 2010 dust storms, or an average of 0.88 km of dust per wind event. Work is currently underway to produce a database to better characterize these dust sources, and their composition.
1U.S. Geological Survey, email@example.com