中文摘要：

选取黄河上游的位于内蒙古境内的一条支流—毛不拉孔兑作为研究区,选取7个典型断面对其河床表层沉积物粒度组分进行测量分析。结果表明：（1）毛不拉流域沉积物中以砂的平均含量最高,达84.17%,其他级配的颗粒物含量均较低,粉粒（14.62%）,粘粒（1.21%）。从流域上游至下游,砂粒含量呈下降趋势。（2）平均粒径的范围为1.17~5.56Φ,平均为2.62Φ,属于砂的粒级范围,平均粒径总体变化趋势为距沟头越远,平均粒径越小;所有断面的分选系数均大于1,属于分选差的级别;偏度均大于0,均为正偏,尖度值在6.99~15.63之间,均为窄峰型。平均粒径和分选系数呈正相关,偏度和尖度呈正相关。（3）毛不拉孔兑泥沙的主要运动形式为推移质。取样分析得出的泥沙粒度分布特征更多地反映出洪水过后水流分选的结果,并且显示出中小水不能挟带粗砂入黄河。（4）产沙地层颗粒组成差异可以看作沉积物颗粒组成差异的内因,水动力为影响沉积物粒度组成差异的外因。影响毛不拉孔兑泥沙粒度组成的主要因素为地貌条件,上游丘陵沟壑区是粗泥沙的主要来源。因此,控制和减少毛不拉孔兑粗泥沙入黄关键在于泥沙源的控制,应加强对上游坡道和沟道的水土保持治理。

英文摘要：

Ten kongduis（the transliteration of ephemeral flood gully in Mongolian）,is ten tributaries on the south bank of the upper Yellow River between Bayangol and Hekou towns. The ten kongduis are one of the principal sediment sources to the upper Yellow River. The Maobula River,one of the ten kongduis,lies at the extreme west. With its special geographical settings,the Maobula River is dominated by wind and water erosion and hyper-concentrated flows. As a tributary from the desert,a large number of coarse sediment from the Maobula River has been transported to the Yellow River with the hyper-concentrated flows. These coarse sediment deposits in the Yellow River,resulting in the elevation of riverbed and even blocking the river for days sometimes,causing serious sediment disasters and huge economic losses. However,previous studies mainly focus on the transporting characteristics of sediment of the Maobula River,and the grain-size distribution characteristics of sediment in the catchment were rarely reported. Grain size is a key factor impacting the sediment transport and river channel changes,meanwhile,it is one of the main factors controlling the pollutant distribution in sediment,especially for the adsorption and release of heavy metals. Therefore,in this paper,the grain size distribution characteristics of sediments in the Maobula River channel and influencing factors are investigated using the moment method for calculating grain-size parameters and analysis of variance. The grain size distribution characteristics are very important to understand the change of sedimentary environment of the study area,implement the soil and water conservation measures in the wind and water erosion area and reduce coarse sediment transported to the Yellow River. Along the Maobula River,seven typical sampling points were set,and analysis of grain-size fractions was carried out by using Mastersizer 2000. The results show as follows：（1）The sand grains are the main component of the deposits on average,and the silt and clay grain