Aeolian dust chemistry and bacterial communities in snow are unique to airshed locations across northern Utah, USA

Abstract

Wind-blown dust is an important source of trace metals, nutrients, and biological material to montane ecosystems. Mountain ranges in northern Utah are located downwind of multiple dust sources including the Great Basin Desert and the Wasatch Front urban area, providing an opportunity to investigate regional-scale differences in dust deposition chemistry and bacterial composition. We sampled discrete dust layers from snowpack across multiple locations in the Wasatch and Uinta Mountains (Utah) and the Snake Range (Nevada) during spring 2014 and 2015. Dust chemistry was unique in each airshed, suggesting that spatial variability and local sources were more important than temporal variability for the sampling period. The central Wasatch dust contained the highest concentrations of playa-associated elements (U, Mg, Li, Ca, Sr, As) and anthropogenic elements (Sb, Cu, Pb, Se) compared with lowest concentrations of these elements in the northern Wasatch, which is further from playa and anthropogenic sources. Sequential extractions indicate that the majority of Ca, Sr, and Cd is potentially available for transport during snowmelt while other elements are relatively immobile. Central Wasatch dust was more reactive to acetic acid than northern Wasatch dust for most elements, including REE + Y. Sr isotopes (87Sr/86Sr ratios) were also unique to each sampling area, with the most radiogenic values in the central Wasatch. Similar to dust chemistry, bacterial communities in dusty snow reflected geographically localized dust events. In the central Wasatch, 69% of bacterial species were unique, suggesting that the airshed received the most diverse dust inputs from a combination of playa and anthropogenic sources. Gram-positive Actinobacteria and Firmicutes were common in snow but specific bacterial families distinguished airsheds (e.g., Bacillaceae, Geodermatophilaceae, Nakamurellaceae). Our results demonstrate that evaluating dust chemistry and bacteria in snow on a regional scale may more clearly link dust sources to the entrainment of pollutants and seeding of bacteria species to montane systems.