近百年来人类活动对鸭绿江口河床演变的影响

Influence of Human Activities on the Riverbed Evolution in Yalu River Estuary during Recent One Century

本文以鸭绿江口西汊道连续性较好、时间分辨率较高、以海湾性质为主的2处现代沉积物为样本,对其沉积速率、粒度特征、碎屑矿物、重金属进行了测定和分析。柱状样记录了1920年以来西汊道上游的沉积过程,平均沉积速率约为0.98cm/a,粒度参数、指示性碎屑矿物、重金属的垂向分布显示出这里的沉积是以海相河口湾沉积为主,但交替存在河流沉积。通过与前期研究成果的比较,揭示了近百年来人类活动对鸭绿江口河床演变的影响。其中,兴修水利对河床演变的影响集中在早期,并带来了河床地貌的重大改变,西汊道失去了河流主汊道的地位;围垦带来的河床演变出现在中期,对河床地貌的影响也很深刻,表现为陆域面积不断扩大,水域面积不断缩小;航道治理等人类活动对河床演变的影响出现在中后期,河床地貌没有明显的改变;最近的人类活动影响有待观察。

The two cores of modern sediments lying in the West-branch-way of Yalu River estuary is characterized by better continuity, higher time resolution and most gulf sediments. The deposition rate, grain characteristics, detrital minerals and heavy metals were measured and analyzed. The depositing process from 1920 with an average rate of 0.98 cm/a in the upstream of West-branch-way was recorded in the core. The vertical distribution of grain parameters, indicative detrital minerals and heavy metals shows that the sediments were mainly from the estuarine deposit of marine phase alternated with the deposit of fluvial phase. In comparison with previous studies, the result reveals the impact of human activities on the riverbed evolution in Yalu River estuary during recent 100 years. The influence of water conservancy projects was mainly in the early period, which led to a great change in riverbed landform. The evolution caused by land reclamation occurred in the middle period and it also exerted a significant effect on riverbed landform and made the terrestrial area bigger and water area smaller continuously. The influence of human activities such as waterway regulation appeared in the middle and late period, during which there was no obvious change in the riverbed landform. The influence of latest human activities needs to be further studied.