Abstract:

A large amount of dust aerosols will be produced in degraded lake basins surface soil under wind erosion， which not only directly affects climate， but also indirectly affects land surface processes， surface temperature and hydrological cycle， thus endangering ecological environment and human health. Based on the dust fall and topsoil samples collected from seven stations from degraded lake basins （Sebei， Duran in Qaidam Basin， North of Qingtu Lake， East of Qingtu Lake， South of Qingtu Lake， Nan Lake and Hongshagang in the eastern part of the Hexi Corridor）， the contents of water-soluble salt ions were determined. The Mineral Liberation Analyser （MLA） was used to detect the micromorphology and chemical element composition， and the differences in physical and chemical composition between topsoil and dust fall in the degraded lake basins were compared and analyzed. The results show that： （1） The salt content in dust fall is much lower than that in topsoil. The salt content of dust fall in the degraded lake basins is less than 51.7 g·kg^-1， while the salt content of topsoil is as high as 166.61 g·kg^-1. （2） There are differences in the distribution of salt content of topsoil and dust in different surface types. From large to small， the salt content in topsoil is： salt crust， interdune-salt crust， dry saline-alkali flat， semi-fixed dune， salinized grassland， but the total content of water-soluble salt in dust fall of different surface types does not show obvious rules； （3） O， Si， Na and Al are the main elements of the dust fall， and the chemical composition is mainly Cl^-， Na⁺ and SO{}_{\mathrm{4}}^{\mathrm{2}-} both in the topsoil and dust. The shape of the dust particles is irregular and the roundness is generally poor. The potential provenance of Sebei and Dulan is mainly in situ dust， while the provenance of Qingtu Lake and its surrounding arid degraded lake basins may also include remote transport.

Key words: arid degraded lake basins, dust fall, micromorphology, chemical element