NUMERICAL MODELING OF MERCURY CONTAMINATED SEDIMENT TRANSPORT IN THE YATSUSHIRO SEA BASED ON IN-SITU MEASUREMENT OF SEDIMENT EROSION

抄録

 Mercury pollution has attracted more attention in marine environment since the outbreak of Minamata Disease in Japan more than 6 decades ago. Although the highly total mercury has been dredged by the government, many experiments for mercury measurement were carried out and indicated that trace mercury was still in Minamata Bay, and some were even transported along with the sediments from the bay to the nearby the Yatsushiro Sea. Hence, it is necessary to develop a numerical model for simulating the mercury migration. In this study, a numerical model was established in Delft3D based on in-situ measurement, where the transport simulation of bottom sediment coupled with the internal diffusion technique was applicated. It was used to simulate the transport of trace mercury from Minamata Bay to the Yatsushiro Sea which was assumed to primarily depend on sediment migration. From the modeling result, it could be concluded that mercury spread from Minamata Bay to the seas around Minamata Bay and gradually spread to the entire Yatsushiro Sea. The mercury transport was mainly divided into two patterns, that is, southwest migration and northeast one. Meanwhile, the trace mercury trended to deposit along the seacoast, which was mainly considered due to the terrain effect.