| 摘 要： |
Understanding the particle size selectivity characteristics by rainfalls in the Gobi is of significance to the assessment and projection of the potential sources for the dust emissions. The particle size selectivity characteristics by extreme rainfall events and their correlations with rainfall characteristics and erosion processes were specifically investigated using indoor artificial rainfall experiments. The soils were collected from the Ala Shan Gobi, where was recognized as the major potential sources of dust emissions in Central Asia. The fine particles (<50 mu m) on-slope after rainfall event were significantly (P < 0.05) higher than the original value at rainfall intensity of 15 mm h-1, but they were significantly (P < 0.05) lower than the original value at other rainfall intensities (except 60 mm h-1) with different particle sorting mechanisms. The selectivity of the fine particles (<50 mu m) by rainfall was higher under 20 mm h-1 and 40 mm h-1, as the medium particle size (d50) of the eroded sediment was significantly (P < 0.05) lower than the original value and the fine particles (<50 mu m) enrichment ratio (ERf) of the eroded sediment was dramatically high (4.3 +/- 1.0 at 20 mm h-1 and 3.5 +/- 0.9 at 40 mm h-1). No significant fine particle sorting was showed both on-slope and in the eroded sediment at 60 mm h-1. The correlation analysis suggested that fine particle selectivity in the eroded sediment was more related with rainfall intensity, runoff rate and flow hydrodynamics. Implications of these findings for effects of the extreme rainfalls on the potential dust sources in the Ala Shan Gobi were presented and it could provide the scientific basis for the prediction of potential dust emission in the Ala Shan Gobi areas in the future. |
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