Overlooked Contribution of Salt Lake Emissions: A Case Study of Dust Deposition From the Qinghai-Xizang Plateau

Abstract

The Qaidam Basin in the Northeastern Qinghai-Xizang Plateau, characterized by its numerous salt lakes and fragile ecosystem, is increasingly impacted by salt dust emissions. To evaluate the impact of salt dust on environment, monthly dust samples were collected from six monitoring stations between January 2020 and March 2023 and analyzed for dust and salt dust deposition flux (DF), mineral composition, water-soluble ions, trace elements, and carbonaceous content. The study used backward trajectory modeling, Pearson correlation, enrichment factor (EF) analysis, and positive matrix factorization (PMF) to quantify salt lake contributions to atmospheric dust. Results revealed that halite and gypsum content ranged from 0 to 47 wt%, with salt dust deposition flux (SDF) varying between 0 and 2.54 g/m²·30d. Key soluble ions included non-playa salt sulfate (nps-SO₄²⁻), playa salt chloride (ps-Cl⁻), and sodium (ps-Na⁺). Trace elements such as iron, aluminum, silicon, and titanium originated from both natural and anthropogenic sources. The organic carbon to element carbon (OC/EC) ratio and PMF model pointed to vehicle emissions, coal combustion, and biomass burning as major pollution sources, particularly in urban areas. PMF analysis showed that salt lakes contributed 5.23%–29.76% of total dust mass, aligning with changes in soluble ion and halite gypsum content. As the region is a key source of river systems, the soluble salts in dust pose risks to glaciers and freshwater resources. These findings highlight the substantial impact of inland salt aerosols in arid inland regions, emphasizing that their contribution to atmospheric processes is significant and should not be overlooked.