黄河口不同粒度泥沙沉积与扩散分析

本文采集和收集大量黄河三角洲沉积物剖面和钻孔泥沙粒度资料以及黄河口来沙粒度组成数据,定量研究了黄河口泥沙的沉积与扩散特征。结果显示黄河口来沙以粉砂为主,黏土次之,砂最少,年均中值粒径无长期变化趋势。黄河三角洲平原相泥沙与来沙的黏土、粉砂和砂含量无显著差异;前缘相泥沙比来沙的黏土含量较低,砂含量较高;前三角洲相泥沙比来沙的黏土含量明显提高,砂和粉砂含量显著降低。计算了一个亚三角洲分组粒径泥沙的沉积量和扩散量,发现黄河三角洲平原和前缘拦截了来沙中绝大部分砂颗粒、一半以上的黏土颗粒和近3/4的粉砂颗粒,但是向远海扩散的泥沙中粉砂含量超过50%。由于粉砂含量较大,扩散入海的泥沙在近距离内大量沉积在前三角洲上。

Deposition and dispersal of different grain-size sediments in the Yellow River estuary

Sediment dispersal in estuaries is an important topic in the study of estuarine and coastal processes. In this paper, sediment particle size data of a large amount of deposit sections and cores on the Yellow River delta and long-term monthly mean sediment size composition of riverine input were collected and analyzed, and the sediment dispersal in the Yellow River estuary was quantitatively studied. The results show that the sediment carried into the Yellow River mouth is composed mainly by silt-sized grains and secondarily by the clay-sized and sand-sized grains, without a long-term trend in the annual mean median particle size. There is no significant discrepancy of clay, silt and sand content between the deltaic plain sediment and riverine sediment input. Compared with the riverine input, the delta front sediment has a lower clay content, a higher sand content, and a similar silt content. The clay content of pro-delta sediment is about twice that of riverine input, and its sand content is much lower than that of riverine input. Although the silt content of the pro-delta is significantly lower than that of the riverine input, it is still over 50%. It is found that deposition and dispersal of different grain-size sediments in the delta can be quantified from the amount of riverine sediment input and the grain-size composition of the riverine sediment and deposits in the delta. The estimated amount of deposition and dispersal of different grain-size sediments in a sub-delta of the Yellow River showed that almost all sand-sized grains, nearly three-fourths of silt-sized grains and more than half of the clay particles were retained behind the delta front slope. The percentage of silt particles in the sediments that dispersed out of the delta front edge was more than 50%, so a high portion of the sediments that dispersed offshore tended to be deposited on the pro-delta surface in a short distance, leaving less sediment to be transferred to the deep sea. The results of this study are of reference value for understanding the processes of sediment dispersal in estuaries and the landform evolution of the Yellow River delta.