Author(s): Edistri Nur Fathya; Shinichiro Yano; Akito Matsuyama; Akihide Tada
Linked Author(s): Shinichiro Yano
Keywords: Mercury; Minamata bay; Fine sediment transport
Abstract: Mercury contamination in Minamata Bay, Japan was caused by organic mercury compound (methylmercury: MeH g), mostly deposited as sediment in the seabed. It is expected that the mercury contamination has reachedthe Yatsushiro Sea, the outer area of the bay[1]. Yatsushiro Sea is a large semi-enclosed bay and it will take time and enormous cost to sample core sediment directly. In order to get precise and effective data, the sediment core sampling is better to be done in the appropriate area where mercury has been concentrated and deposited. Therefore, the preliminary research for sediment transport before sediment sampling has to be done in order to get the accurate location for sampling data. Previous research has simulated the sediment transport on the uniform and coarse grid for only 5 layers[2]. By increasing the accuracy, the variable horizontal grid and additional layers for simulating the sediment transport areadapted. The rectangular variable grid is made by grid module in DELFT3D software, it consists of three different grid sizes, namely, 250m (original size), 125m, and the finest 62.5m. The finest area is anarea including Minamata Bay. DELFT3D is used for simulating the sediment transport and tidal flow around the Yatsushiro Sea and Minamata Bay. A number of layers up to 10. Six months simulation result is compared with the previousuniform and coarser grid simulation. The previous result of barotropic flow shows the dominant movement of sediment is both westward and southward [2]. By adapting the additional layers and the finer grid, the result shows not only to west and south but also, there is a northward movement of sediment around the coastal area. The result of baroclinic flow from previous and present result did not show significance different, the flow mostly northward. From 6 month simulation, it is showed that most deposit areas that generated by barotropic flow are the western and southern area from Minamata Bay and baroclinic flow moves the sediment to northern and finally dispersed it to outside area of the southern Yatsushiro Sea.
Year: 2016