IDENTIFICATION OF DUST SOURCE “HOT SPOTS” ON THE EXPOSED PLAYA OF THE GREAT SALT LAKE, USA

Due to a combination of water diversion and drought, the terminal basin Great Salt Lake (GSL) has receded significantly exposing more than 1960 km² (~757 mi²) of playa. Dust plumes emanating from the playa now frequently degrade local air quality, potentially impacting the health of more than 2 million adjacent residents. The goal of this study was to determine which areas of the GSL playa currently act as dust source regions (i.e., dust “hot spots”) and place an upper bound on the fraction of the playa capable of generating dust plumes in the absence of vegetative cover and/or protective surface crusts.

A systematic survey of the entire GSL playa was conducted between June 2016 and August 2018 using in situ observations of vegetative cover, surface crust characteristics, and visible plumes stimulated by manual disturbance of the surface. A total of 5246 surface observations were made using a GPS-derived grid system with a nominal horizontal resolution of 500m. Active GSL dust “hot spots” were identified as locations which had little or no vegetation, had either no surface crust or an erodible shallow crust, and where visible plumes of fine particulate matter could be generated by manually disturbing the surface.

Dust “hot spots” were identified in all four quadrants of the GSL playa. Intact (i.e., non-eroding) shallow, moderate, or thick surface crusts covered ~75% of the playa. These surface crusts significantly limit the areal extent of the dust plume source regions. Vegetation was observed on 15% of the exposed playa. Vegetative encroachment from the margins helps stabilize the soil, reduce the windspeed near the surface, and reduce dust mobilization. ~11% of the total exposed lakebed was identified as active dust “hot spots”. These areas were characterized by little or no vegetation, no crust or an erodible shallow crust, and the presence of visible dust plumes when stimulated by manual disturbance of the surface. Only 21% of the playa generated dust plumes as a result of manual disturbance. This value represents the upper bound for the fraction of the GSL playa capable of generating dust plumes if all of the protective surface crusts erode away over time or are destroyed by human activities.