Contrasting sulfur isotope signatures in two arid basins separated by the Qilian mountains.

Global climate variations have intensified the transformation of salt lakes and saline-alkali playas in arid regions into major sources of saline-alkali dust storms, actively influencing atmospheric circulation and climate dynamics. This study focuses on two geographically close but environmentally distinct regions, the Qaidam Basin and the Alxa Plateau, situated on opposite sides of the Qilian Mountains. Surface salts were collected from both areas and analyzed for ion composition and sulfur isotope characteristics. Results reveal high concentrations of Na and Cl in both regions, with Mg and SO also present, reflecting similarities in ionic composition. The δS values differ in distribution between the two regions: the Qaidam Basin shows higher and more clustered values (+ 9.11‰ to + 20.23‰), indicating a relatively closed system, while the Alxa Plateau includes lower and occasionally negative values (- 2.30‰ to + 11.43‰), reflecting more variable sulfur inputs and open-system conditions. The study also examines sulfur-to-chloride ratios, which vary significantly across sites in the Alxa Plateau, reflecting complex environmental interactions and diverse sulfur sources. In the Qaidam Basin, sulfur-to-chloride ratios are more stable, suggesting consistent sulfur cycling within a relatively closed environment. Additional analyses of sulfate-to-sodium and sulfate-to-magnesium ratios further emphasize the distinct sulfur sources and processes in each region, with minimal impact from these ions on δS values. This study provides insights into the contrasting sulfur isotopic and ionic ratios that shape the material sources and evolutionary processes in the Qaidam Basin and Alxa Plateau.