Watershed Symposium 2019

Linkages Between the Great Salt Lake and Air Quality

Summary:
History shows how climate change, drought, & water diversion quickly reduce once thriving lake ecosystems to a fraction of their former sizes. Entire ecosystems were disrupted, economies threatened, new pollution sources (i.e., dust plumes) created, & local populations suffered. The Great Salt Lake (GSL) is on track to suffer a similar fate.

Full Abstract:
History has shown that the combination of climate change, drought, and water diversion can quickly reduce once thriving lake ecosystems to a fraction of their former sizes (e.g., the Aral Sea, Owens Lake, and the Dead Sea). As these water bodies dried up, entire ecosystems were disrupted, industries were shuttered, economies were threatened, new pollution sources (i.e., dust plumes) were created, and local populations suffered. The Great Salt Lake (GSL) is on track to suffer a similar fate due to a combination of water diversion and drought. As the lake has receded, it has exposed more than 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. A two-year study was recently completed to: 1) Determine which areas of the GSL playa currently act as dust source regions. 2) Determine how fluctuating lake levels might impact future dust production. 3) Determine if the PM10 soil fraction of the GSL playa contains potentially hazardous heavy metals. To accomplish these goals, a systematic survey of the entire GSL playa was conducted between June 2016 and August 2018 using a bicycle/trailer system. Incremental Sampling Methodology protocols were used to ensure that soil samples and in situ observations of surface crust/vegetation conditions were representative. A total of 5246 soil samples and surface crust/vegetation observations were collected/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” matching these criteria were identified in all four quadrants of the GSL playa and comprised ~11% of the total exposed lakebed. Dust “hot spot” locations were then combined with a digital elevation model to determine their elevation distribution. This analysis revealed that the number of dust “hot spots” is linearly dependent upon the GSL elevation with slopes ranging from 6% to 13% per foot. The soil samples were composited into 122 samples which were subsequently dried and sieved. The PM10 fraction was analyzed using Inductively-Coupled Plasma Mass Spectrometry and Synchrotron X-ray Fluorescence to provide mass fractions for 54 elements. These results were then compared to the Regional Screening Levels established by the US Environmental Protection Agency to determine whether any of the elements might pose a risk to adjacent populations. Arsenic was the only heavy metal for which every measurement exceeded the RSLs for residential and industrial exposures. As a result, a site-specific exposure assessment should to be completed to determine if arsenic exposure poses an actual threat to human health. Learning Objectives: - Current and future water diversions of the GSL pose serious risks to maintaining water levels. - Potential impacts from a dried up GSL on residents along the Wasatch Front. - Understanding of the connections between snowpack, rivers, lakes, land, and air quality.