黄河口埕岛海域悬浮沉积物沉降规律原位观测

IN-SITU OBSERVATION OF SEDIMENT DEPOSITION PROCESS IN CHENGDAO SEA AREA OF THE YELLOW RIVER ESTUARY

运用时间序列沉积物捕获器,原位捕获了黄河口埕岛海域某观测点的沉降沉积物,并结合同步的波浪、海流、水深等水动力参数观测以及后续土样粒径分析等研究手段,计算了沉降通量,推断了沉降沉积物的来源,并结合理论计算探讨了悬浮沉积物沉降过程的影响因素以及沉降量在再悬浮量中所占的比例。研究结果表明:黄河口埕岛海域的悬浮沉积物沉降通量约为120~280g·m^(-2)·d^(-1),与该海域的再悬浮通量有着很好的正相关关系,推测很可能主要来源于海底沉积物的再悬浮;在该海域,即使过剩剪切力持续大于0,悬浮沉积物仍然会发生沉降,并且可以大于过剩剪切力小于0时的沉降量,推测与该地区粉质土海床的液化特性有关;再悬浮沉积物大约有5%发生原位沉降,绝大部分沉积物保持悬浮或者被输运至异地,这与该地区海底遭受强烈侵蚀的现象相一致。

The in-situ measured amount of deposits was obtained in the Chengdao sea area off the Yellow River Estuary using a time-series sediment trap.Combined with the synchronous hydrodynamic observation and subsequent laboratorial grain size analysis,we firstly calculated the depositional flux,and subsequently analyzed the source of trapped sediments,then discussed the influence factors of depositional process,and finally evaluated its proportion in the resuspended sediments.The results indicate that the sediment depositional flux in the Chengdao sea area is around 120~280g·m^(-2)·d^(-1).The depositional fluxes show a positive correlation with the re-suspended deposits possibly indicating that the deposited sediments maybe mainly come from the re-suspension of bottom sediments.Sediment deposition still occurs even the excess shear stress is greater than zero,and the amount of deposition may be greater than that when excess shear stress is intermittently less than zero.This is inferred as the consequence of the liquefaction properties of silty seabed in the area.About 5% of the resuspended sediments deposit in-situ,and most of them remain in suspension or will be transported elsewhere,which may be the reason of intense erosion of seabed in this area.