辽东半岛东岸近海泥区悬沙浓度的时空分布及控制因素分析

Spatio-temporal distribution and control factors of surface suspended sediment concentration in the mud deposition along eastern coast offshore of the Liaodong Peninsula

鸭绿江作为典型的中小型河流,细颗粒沉积物从鸭绿江流域到辽东半岛东岸近海泥区的源汇过程有着独特的机制,而遥感解译是了解入海沉积物在河口-陆架输运过程和机制的有效手段之一。因此,本文通过在辽东半岛东岸海域进行了现场悬沙浓度测量,并与GOCI影像建立关系,反演了该地区2011年4月至2017年3月间的表层悬沙浓度,从而揭示了该海域表层悬沙浓度的时空特征,分析了潮流、大风天气和洪水对悬沙浓度变化的影响,在此基础上探讨了研究区的悬沙浓度输运格局。结果显示,研究区表层悬沙浓度空间差异大,河口附近是悬沙浓度高值区,可达500 g/m^3以上,其他区域则悬沙浓度多小于20 g/m^3。另外,研究区表层悬沙浓度枯季高,洪季低,有着显著的季节性变化。进一步分析表明,枯季大风天气引起的风浪作用增强,是导致表层悬沙浓度增高的主要原因;洪季虽然悬沙浓度较低,但流域洪水期间的悬沙浓度显著增加。此外,作为典型的中小型源-汇传输体系,沉积物从鸭绿江到辽东半岛东岸近海泥区总体上仍遵循"夏储冬输"的输运机制。

As a typical small and medium-sized river, the source to sink process of fine sediment from the Yalu River catchment to the mud deposition of the offshore eastern Liaodong Peninsula is characterized by a unique mechanism. Among other methods, remote sensing is an effective means to understand the process and mechanism of sediment transport in estuarine-continental shelf. In this paper, we measured the surface suspended sediment concentration (SSC) in the eastern coast offshore of the Liaodong Peninsula, and then established a relationship between the measured SSC and the Remote Sensing Reflectance (Rrs) of GOCI images to retrieve the long-term spatio-temporal distribution of surface SSC (April 2011 to March 2017). The effect of tidal current, strong wind and flood on the variations of surface SSC is further analyzed. The SSC transport pattern from the Yalu River to the mud deposition along eastern coast offshore of Liaodong Peninsula is finally discussed. The results show that the distribution of the surface SSC in the study area displays great spatial differences. Near the estuary, the surface SSC is of highest value and is greater than 500 g/m^3 . While in other areas, the SSC value is less than 20 g/m^3 . Concerning the seasonal variation, the surface SSC value in the dry season is higher than that in the flood season, which is mainly due to the enhanced wind waves by strong winds in the dry season. Although the surface SSC value is low in the flood season, it still significantly increased during the flood period of the Yalu River catchment. In addition, as a typical small and medium-sized source-sink conveying system, the sediment transport mechanism from the Yalu River to the mud deposition along eastern coast offshore of Liaodong Peninsula is generally characterized by “deposit in summer and transport in winter”.