Arsenic mobilization at the water-shore interface of a shrinking saline lake

Shrinking saline lakes present significant environmental and public health concerns due to the mobilization and potential transport of toxic elements from exposed sediments. This study primarily investigates arsenic (As) mobility in sediments of the Great Salt Lake, Utah, under varying shoreline conditions and wet-dry cycles. Sediment cores were collected from two sites in the South Arm of the lake and analyzed for As, iron (Fe), manganese (Mn), calcium (Ca), sodium (Na) and carbonates. Field observations indicated higher As, Fe, and Mn concentrations in recently exposed sediments compared to sediments that had undergone prolonged wet-dry cycling. A significant correlation was observed between sediment moisture content and As concentration, highlighting the role of hydrological fluctuations in elemental redistribution. Carbonates are abundant (over 50 % on a mass basis) and ubiquitous at these sites, with aragonite as the dominant carbonate mineral playing a significant role in As chemistries. Laboratory wetting-drying experiments confirmed that As is predominantly associated with carbonate minerals and is redistributed under changing wet-dry cycle conditions. Site-specific differences in elevation influenced elemental patterns, with stronger trends observed at the site with greater topographic variability. These findings underscore the importance of shoreline processes and sediment geochemistry in controlling As mobility, which has implications for dust emissions and potential human exposure to harmful elements. Future studies should examine long-term sediment dynamics and atmospheric transport pathways in As mobilization to further inform risk assessments for terminal lake ecosystems.