Radiogenic isotope variability in contemporary mineral dust across the intermountain west of the United States

Mineral dust is a highly mobile component of Earth’s Critical Zone that influences ecosystem function, soil development, biogeochemical cycling, and environmental archives. Radiogenic isotopes provide a powerful means of characterizing dust because isotope ratios largely preserve source signatures during atmospheric transport. Here we present a dataset of 100 modern dust samples analyzed for 87 Sr/ 86 Sr and ε Nd from a network of 20 passive dust collectors distributed across the Intermountain West of the United States, including sites in the Uinta Mountains, Wasatch Mountains, Great Basin ranges of Nevada, southern Utah, southern Idaho, and urban environments. Pb isotope compositions were determined for samples from 8 of these collectors. Consideration of collector position, grain-size distribution, and local geology identifies a limited number of samples influenced by locally derived material, but most measurements provide a robust characterization of the isotope fingerprint of contemporary dust deposition. Distinct geographic patterns are evident, with dust from Nevada exhibiting lower 87 Sr/ 86 Sr ratios and higher ε Nd values than dust collected in Utah mountain environments, whereas samples from southern Utah, Idaho, and urban locations occupy intermediate but distinguishable isotopic fields. These isotope fingerprints can be provisionally linked with potential source areas upwind. In concert with Sr and Nd, Pb isotope ratios provide additional discriminatory power. Repeated sampling demonstrates that individual sites exhibit modest year-to-year variability, yet temporal variation is generally smaller than spatial differences among regions. The resulting geographic clustering indicates that dust deposited across the Intermountain West is not isotopically homogeneous, but instead exhibits persistent regional differences reflecting varying source landscapes and transport pathways. These results highlight the value of distributed monitoring networks for characterizing dust variability across broad regions and provide a foundation for future investigations of dust transport, landscape connectivity, and Critical Zone processes in western North America.