Characterizing a Hazardous Dust Source in the Chihuahuan Desert Using Ground-Based Measurements, Remote Sensing, and Modelling

Ephemeral lakebeds, common features in semiarid and arid regions, are often potent sources of atmospheric dust. One such ephemeral lake in southwestern New Mexico, USA, Lordsburg Playa, is transected by Interstate 10 (I-10), a major transportation artery crossing the southern US. Since construction of I-10 in the 1960s, at least 45 people have perished in motor vehicle crashes at Lordsburg Playa caused by dust-associated loss of visibility. The rate of visibility reductions from dust and traffic crash deaths has increased as climate change has resulted in persistent drought in this region. We used ground-based measurements creating dust emissions from increasing levels of shear stress via a Portable In-Situ Wind ERosion Laboratory (PI-SWERL) to test natural and disturbed surfaces. These tests assessed the potential dust emissivities of different sediment surfaces and landscape positions along with the effects of surface disturbance by anthropogenic activities. We also investigated the evolution of the playa and surrounding landscapes using 35 years of remotely sensed images from the Landsat 5 and Landsat 8 satellites and a shorter time period for the higher spatial resolution images from the Sentinel-2 satellite using spectral unmixing to separate the relative contributions of bare soil, water, and vegetation endmembers from the spectral reflectance of individual pixels. Interferometric techniques were applied to data obtained from Synthetic Aperture Radar instrumentation aboard the Sentinel-1 satellite to develop digital elevation maps for the playa and surrounding landscapes. Finally, we used process-based models to simulate wind erosion, resulting PM₁₀ emissions (SWEEP), and plume transport (AERMOD) from a dust source immediately adjacent to and often upwind of the highway. We found that natural surfaces in the playa basin were highly variable with respect to their potential dust emissivities. Beach deposits along the eastern and particularly western margins of the lakebed were the most highly emissive, followed by soils in the Animas Creek Delta south of the lakebed which were in turn much more emissive than the indurate sediments of the lakebed floor and similar buried lakebed sediments. Further, disturbance of the soil surface in the delta sediments resulted in order of magnitude increase in dust emissions. Analysis of the remote sensing images revealed annual and seasonal differences in the proportion of the bare soil, vegetation, and water endmembers present on the playa lakebed and surrounding landscapes. The bare soil endmember was greatest during the spring and in years with less than average rainfall. In many cases, these drought-affected years aligned temporally with the increased frequency of dust events and fatalities from motor vehicle crashes. The summer monsoon season generally resulted in an increase of the water endmember in the lakebed and in increases of the vegetation endmember on the delta sediments and uplands surrounding the playa. Years with more water surface coverage in the lakebed and greater vegetation coverage tended to have less frequent dust events. Modelling using SWEEP to simulate wind erosion and dust entrainment and AERMOD to simulate transport and dispersal of the resulting dust plume agreed well with visual images obtained with cameras adjacent to the modelled source area and a nearby New Mexico Department of Transportation meteorological tower.