Characteristics of the atmospheric dustfall in the Taklimakan hinterland: ground observation and microscopic analysis

Abstract

The physicochemical characteristics of dustfall particles are essential for the in-depth understanding on the aerodynamic processes of aeolian dust and its environmental effects. In this study, we conducted continuous high-frequency sampling of atmospheric dustfall in the Taklimakan hinterland during spring 2022, analyzing particle micromorphology, size distribution, mineral composition, deposition fluxes, and vertical dust characteristics. The results showed that the dustfall particles sampled in the Taklimakan hinterland were mostly micro-aggregates, angular, and subrounded based on the statistical analysis of the Focused Ion Beam Scanning Electron Microscope (FIB-SEM). As determined by the Laser Diffraction Particle Size Analyzer (LDPSA), the dustfall particles were predominately coarse particles, with particles between 20 μm and 80 μm accounting for 83.73 % of the total particle number. Volume proportion of dustfall particles with particle size of 60–150 μm was 72.41 %. Mineralogical analysis of dustfall particles using the Intelligent Scanning Electron Microscope Environmental Particle Analysis System (IntelliSEM EPAS) revealed that calcite was the dominant component (31.15 %), followed by quartz (18.52 %), chlorite (11.84 %), kaolinite (8.11 %), smectite (6.28 %), and illite (5.25 %). Halite was identified as the primary salt component, making up 9.52 % of detected particles. Vertical dust profiles derived by the ground-based Mie-scattering lidar indicated that large amounts of irregular dust floated in the tropospheric atmosphere over the Taklimakan Desert, causing a high depolarization ratio of more than 0.6 within 5 km of the surface. These dust aerosols suspended in the upper air with long periods were attributed to the frequent windblown dust weather over the Tarim Basin in spring, resulting in high ambient particulate concentration and dust deposition.