Atmospheric dustfall exhibits consistent sedimentary sorting with height evidenced by grain size characteristics

Abstract

The grain size of aeolian deposits is a key property to understanding their sedimentary sorting characteristics, which determine the sedimentary dynamics of an airflow field. Although atmospheric dust sedimentary sorting processes are understood well in the horizontal direction, those in the vertical direction and their influencing factors remain unclear. Herein, modern atmospheric dustfall was collected using dust traps at heights of 1, 2, 4, 6, and 8 m to reveal its sedimentary sorting characteristics. The analysis demonstrated that atmospheric dustfall exhibits a bimodal grain size distribution, and the bimodal grain size distribution curves change within a height of 8 m. However, either peak 1 or peak 2 exhibits consistent grain size characteristics with height; hence, each sub-peak indicates consistent sedimentary sorting within a height of 8 m. The modification of grain size distribution curves with height is mainly driven by different sedimentary fluxes for peak 1 at different heights. Dustfall grain size characteristics are also potentially affected by the settling height, concentration of the atmospheric dust, and dust sedimentary flux. However, the sedimentary sorting of sub-peak components is mainly governed by the near-surface airflow field. Thus, this reveals the process of formation and grain size distribution of aeolian deposits. Overall, atmospheric dustfall with mixed multi-peak components conceals information on the sedimentary environment.