Combining modeling and isotopic signatures to track Aeolian dust from source to sink in the Wasatch Front, Utah, USA

Abstract

Dust events are tracked from source to sink using geochemical/isotopic tracers, dust emission and transport modeling, or remote sensing, but these tools are rarely used together. To test the utility of combining multiple dust tracking methods, we used three Wasatch Front (Utah) dust events from August 2009, May 2020, and September 2020 to compare source apportionment estimated by the Community Multiscale Air Quality (CMAQ) model and strontium isotope (⁸⁷Sr/⁸⁶Sr) ratios. The Wasatch Front is impacted by atmospheric particulate matter (PM) from local urban sources and regional playas including Sevier Dry Lake, Great Salt Lake (GSL), and the GSL Desert. CMAQ modeling of the August 2009 event showed dust emission and transport from multiple playa sources to the Salt Lake City measurement site as wind patterns changed during the storm. The predicted mix of sources was consistent with the measured ⁸⁷Sr/⁸⁶Sr ratio of 0.71217 on the PM₁₀ filter collected during the event. Modeling of the May 2020 period showed a consistent meteorological pattern that carried dust from the Sevier Dry Lake area toward the Provo measurement site, consistent with the measured ⁸⁷Sr/⁸⁶Sr ratio of 0.71015. Modeling of the September 2020 period indicated a major dust event with complex wind patterns that changed during the event, resulting in relatively small amounts of dust from GSL Desert being transported to the Provo site. No emissions from Sevier Dry Lake were predicted to reach the site during the September event, suggesting GSL Desert contributions were mixed with local dust with a lower ⁸⁷Sr/⁸⁶Sr ratio to produce the measured value of 0.71097. Results from the three dust events demonstrate the benefits of combining CMAQ emission and transport modeling with isotopic data from PM₁₀ filters to better characterize dust source-to-sink behavior in Utah, and illustrate the potential for application in other arid regions.