Freeze-thaw cycles enhance dust emission from soil aggregates

Dust particles play a crucial role in the formation and stability of soil aggregates, significantly influencing dust emissions from source areas. The gradual intensification of freeze–thaw cycles substantially affects soil erosion in alpine regions. However, the mechanisms governing aggregate stability during freeze–thaw cycles and the subsequent wind-driven dust emission processes remain unclear. In this paper, we present an experimental study into the microscopic changes in soil aggregates and the mechanisms of dust emission resulting from repeated freeze–thaw cycles. Specifically, we analyze the effects of the number of freeze–thaw cycles on dust emission, erosion rates, and dust contribution rates. Our results show that freeze–thaw cycles cause the deflection and separation of aggregates, increase surface porosity, promote localized particle fragmentation, and generate new particulate matter. The erosion rate of soil aggregates and the vertical dust release flux both increased with the number of freeze–thaw cycles, eventually stabilizing at levels 1.5 and 1.8 times higher, respectively, than those observed on unfrozen surfaces. Additionally, freeze–thaw cycles enhanced dust emission from dry soil aggregates, increasing the contribution to soil erosion by 22 %, with a significant increase in dust particle concentrations in the 10 to 32 μm range. This study provides valuable insights into the structural changes in soil aggregates and the mechanisms of dust emission under freeze–thaw conditions.