泥沙来源减少后长江口最大浑浊带变化研究

Processes of the maximum turbidity zone of the Yangtze Estuary under the background of reduced sediment sources

河口最大浑浊带常位于入海河口的盐水与淡水交汇处,含沙量显著高于其上游和下游,最大浑浊带在河口地貌发育、三角洲演变过程中具有重要意义。近几十年来随着长江口入海泥沙持续减少,河口最大浑浊带也产生相应变化。基于长江口最大浑浊带水文调查及历史资料,研究泥沙来源持续减少所导致的长江口最大浑浊带含沙量变化特征及影响机制。结果表明:流域来沙持续减少是河口最大浑浊带含沙量下降的主导因素;河口最大浑浊带含沙量下降滞后于流域来沙减少;最大浑浊带表层含沙量减少幅度高于底层含沙量;泥沙再悬浮过程和河口纵向环流有利于稳定最大浑浊带底部的高含沙量,从而延缓河口最大浑浊带含沙量的减少趋势。

The maximum turbidity zone is usually located at the confluence of salt and fresh water in estuaries, and the sediment concentration is higher than that in the upstream and downstream. In recent decades, with the continuous decrease of sediment from the Yangtze Estuary to the sea, the maximum turbidity zone has changed accordingly. Based on the hydrological survey and historical data in the maximum turbidity zone, the variation characteristics and the influence mechanism of sediment concentration in the maximum turbidity zone were studied under the continuous decrease of sediment sources. The results show that the continuous decrease of sediment inflow is the dominant factor for the decrease of sediment content in the estuarine maximum turbidity zone. The decrease of sediment content in maximum turbidity zone lags behind that of sediment inflow.