黄河宁蒙段河道粗细双组分泥沙分选沉积特征

黄河宁蒙段河道淤积严重，阐明近源粗泥沙和远源细泥沙分选沉积规律对于河道淤积治理有重要意义。本研究基于120根河道钻孔泥沙样品，通过粒径分布和元素矿物组成，分析了河道>0.05 mm、>0.08 mm和>0.1 mm粗泥沙沿河分选沉积变化特征，并定量评估了近源粗泥沙和远源细泥沙沉积对于河道泥沙淤积的贡献。结果表明：黄河宁蒙段河道淤积的主要是来源于近源沙漠及其下伏砒砂岩区>0.08 mm的粗泥沙，而来源于上游黄土区<0.05 mm的细泥沙主要沉积在河道滩地，对河道淤积的贡献小于30%。因此，风水复合侵蚀引起的沿黄沙漠和下伏砒砂岩粗泥沙入黄是黄河宁蒙沙漠河段河道淤积的根源，也是该河段“悬河”的治理重点。

Selective deposition of coarse and fine sediments in the Ningxia-Inner Mongolia reach of the Yellow River

The accumulation of silt in some sections of the Yellow River from Ningxia to Inner Mongolia is serious. It is of great significance to clarify the sorting and deposition law of near-source coarse-grained sediment and far-source fine-grained sediment for the control of accumulated silt in Ningxia-Inner Mongolia section of Yellow River. In this study， based on the 120 sediment samples obtained by drilling hole in the river， the variation characteristics of coarse-grained sediment content along the river with d>0.05 mm， d>0.08 mm and d>0.1 mm were analyzed through particle size distribution and mineral and element composition of coarse and fine sediment. And the contribution of near-source coarse sediment and far-source fine sediment sorting deposition to river sediment deposition was quantitatively evaluated. The results show that the main deposition of the river channel in the Ningxia-Inner Mongolia section of the Yellow River is the coarse sediment （d>0.08 mm） from the near-source desert and its underlying Pisha sandstone area， while the fine sediment （d<0.05 mm） from the upstream loess area is mainly deposited in the river beach， contributing less than 30% to the deposition of the river channel. Therefore， the coarse-grained sediment entering the Yellow River along the desert near Yellow River and underlying Pisha sandstone induced by the process of wind and water erosion should be the focus of river deposition and 'suspended river' control in the Ningxia-Inner Mongolia section of the Yellow River.