长江口表层沉积物粒度时空分布特征

Temporal and Spatial Characteristics of Surface Sediment Grain-size Distribution in Changjiang Estuary

结合近期长江口558个表层沉积物采样资料,分析了长江口表层沉积物时空分布特性,得到了近期长江口表层沉积物中值粒径和沉积物类型分布特征。横沙以上海域表层沉积物粒径洪枯季变化较小;浑浊带海域洪季粗,枯季细;口外海域则枯季粗,洪季细。横沙以上和口外海域沉积物类型洪枯季变化较小,浑浊带海域沉积物类型变化较复杂。无论洪枯季北港表层沉积物最粗,北槽次之,南槽最小。表层沉积物大小潮变化较小,两次采样平均差别为9.7%;沉积物年际变化随大通流量和输沙量的变化而变化。近十五年来,长江口表层沉积物类型变化较大的区域主要是北支上段、南北港分流口、北槽和南槽浑浊带海域,主要与河槽的自然演变和人类活动有关。结合Pejrup新三角图对长江口各沉积动力环境进行分区,对比各沉积环境亚区的粒度特征,并对黄河口、长江口、珠江口表层沉积物粒度参数进行对比。

Based on 558 surface sediment samples collected in Changjiang Estuary recently, the temporal and spatial characteristics of surface sediment grain size were analyzed, and the distribution of D50 and types were obtained, too. The results showed that few changes of the surface sediment grain size in upper Hengsha Island was showed between flood and dry seasons. The grain size in flood season was coarser than that of dry season in the Turbidity Maximum, and in the mouth of the estuary, the grain size in flood season was finer than that of dry season. The types of surface sediment in upper Hengsha Island and mouth of the estuary were changeless between flood and dry seasons, while in the Turbidity Maximum, it was much more complex and various. Whether in flood season or in dry season, the coarsest surface sediment was in North Channel, then in the North Passage, and the finest surface sediment was in the South Passage. Little difference of surface sediment grain size was showed between spring tide and neap tide, and the difference of mean diameter was about 9.7%. The grain size of different years was changed with the Water discharge and sediment discharge of Datong Station. The grain size of surface sediment in upper North Branch, distributary site of South and North Channels and Turbidity Maximum of South and North Passages were much more changeable in the recent fifteen years. These changes were due to the natural channel processes and human activities. The dynamic sediment environment in Changjiang Estuary was of each sediment environment were discussed. divided by Pejrup triangular diagram, and the grain size characteristics Then, the grain size parameters of surface sediment in Yellow River, Changjiang and Pearl River Estuary were contrasted in this paper.