Mercury dynamic simulation of Minamata Bay by using a three-dimensional numerical model

Abstract

Residual mercury dynamic has been the research emphasis since mercury contamination was publicly recognized in Minamata Bay. Simulation of mercury distribution and transport pattern is performed based on an integrated three-dimensional numerical model. Simulated dissolved total mercury and dissolved methyl-mercury show acceptable agreements with measurements. Deviation occurs during the simulation of particulate mercury at bottom layer and is probably caused by the existence of coarser sediments which could barely suspend to upper layers. Mercury transport pattern in larger Yatsushiro Sea is simulated and analyzed with mercury source from Minamata Bay. Study results suggest that substantial mercury deposition happened during preliminary stage of simulation. Due to the effect of current outside bay mouth, transport of mercury at middle and bottom layers has the trend to north, while west transportation of mercury output is presumed to happen during slack tide. Surface mercury transport is sensible to wind effect, moreover, higher magnitude of flow velocity causes different transport tendency compared with lower layers.