Saltation-Sandblasting Processes Driving Enrichment of Water- Soluble Salts in Mineral Dust

Dust aerosols over the Taklamakan Desert contain up to 3%-4% of soil-derived water-soluble sulfate, much higher than that in the soil. It has been hypothesized that this is due to aerosol-soil fractionation during dust emission. Here, we tested this hypothesis based on laboratory simulations of saltation and sandblasting processes. Two types of soil samples (sandy deserts and gravel deserts) were collected from the Taklamakan Desert, from which dust aerosols were generated for offline chemical analyses. We found that these laboratory-generated dust aerosols contain soil-derived watersoluble ions, and the contents are comparable to those measured in ambient dust but were several to hundreds of times those of the original soils. We argue that it is the fractionation in the saltation and sandblasting processes that led to the enrichment of watersoluble salt in dust aerosols. Our results provide the first geochemical constraints for understanding the origins of water-soluble ions in dust particles emitted from the Taklamakan Desert and the impact of chemical processing on dust composition during long-range transport.