毛乌素沙地风沙土粒径分布特征及其影响因素

为揭示毛乌素沙地风沙土粒径分布特征，推测其影响因素，以毛乌素沙地流动、半固定和固定沙丘风沙土为研究对象，利用激光衍射技术分析其粒度组成，并计算粒度参数，解析粒配曲线，研究结果表明：（1） 毛乌素沙地风沙土优势粒径组为细砂，其平均体积含量约为29.89%～32.46%，不同类型沙丘无显著差异（P>0.05）；少数粒径组分为粗砂、黏粒和极粗砂，其中流动沙丘与半固定、固定沙丘黏粒与粗砂含量均无显著差异（P>0.05），从半固定到固定沙丘，黏粒含量显著增加（P<0.05），粗砂含量显著减小（P<0.05），从流动沙丘到固定沙丘，极粗砂含量显著减小（P<0.05）。（2） 毛乌素沙地风沙土平均粒径为3.35 Φ，粒度分布集中，分选性较差，偏度状况为正偏，尖窄峰态。在沙丘固定的过程中，平均粒径与标准偏差无显著变化（P>0.05），峰态显著变宽平（P<0.05），半固定沙丘偏态值与其他2种沙丘相比显著偏负（P<0.05）。（3） 流动、半固定与固定沙丘跃移组分的粒径区间分别为44～435 μm、63～500 μm和31～354 μm，风沙运动在半固定沙丘中最为强烈。毛乌素沙地风沙土优势粒径组分含量主要受物源影响，少数粒径组分含量主要受沙丘流动性影响，风沙运动强度随沙丘的固定呈先增大后减小的规律。

Particle size distribution of aeolian soils in the Mu Us Sandy Land and the influence factors

To reveal the characteristic of particle size distribution (PSD) of Aeolian soils and the influence factors at the Mu Us Sandy Land,which is between Shaanxi Province and Inner Mongolia,China,the soil PSD were identified from the mobile,semi-fixed and fixed dunes using laser diffraction technique.Subsequently,soil PSD parameters and curves were calculated including average particle size,standard deviation,skewness,kurtosis and frequency distribution and cumulative curves.The results indicated as follows: (1) fine sand was the dominative group accounting for 29.89% up to 32.46% of the total volume in the Mu Us Sandy Land and there were no significant differences between different types of dunes (P >0.05).Accordingly,coarse sand,clay and extreme coarse sand were much less.For clay and coarse sand,there was no significant difference between mobile,semi-fixed and fixed dunes (P >0.05).However,the content of clay particles was increased significantly and the content of coarse sand was decreased significantly from semi-fixed and fixed dunes (P <0.05).Furthermore,the content of extreme coarse sand was significantly decreased from mobile and fixed dunes (P <0.05).(2) The average particle size was 3.35 Φ in the Mu Us Sandy Land.Soil particle size distributions were centralized,which reflected a poor sorting capability,a very positive skewness and sharp kurtosis.During the sand dune fixation,there was no significant difference in average particle size and standard deviation (P>0.05).Nevertheless,kurtosis became significantly wider (P<0.05).For the semi-fixed dunes,the skewness was inclined to negative if compared with the other two types of dunes.(3) The particle size of the saltation in the mobile,semi-fixed and fixed dunes was 44-435,63-500 and 31-354μm,respectively,which indicated strongest Aeolian movement in the semi-fixed dunes.In the Mu Us Sandy Land,the dominative particles were primarily affected by sand source,while the minorities were mainly influenced by the mobility of sand dunes.The intensity of sand transport was growing first and then reducing as the sand dune got fixation.This information from this study will contribute to reveal the sand transport during the sand dune fixation,and provide firm basis for ecological restoration in desertified areas.