2023 年 11 巻 2 号 論文ID: 23-18037
After the outbreak of Minamata Disease, highly mercury-polluted sediment was dredged from Minamata Bay. Nevertheless, some studies indicated that trace mercury (Hg) migrated from Minamata Bay to the Yatsushiro Sea with the movement of sediments. Mercury was considered to adsorb on sediment particles and realized the transport. However, the influence of particle size as a crucial factor affecting adsorption is barely considered in the analysis of mercury migration.
In this study, we develop a novel method based on particle size classification to comprehend both horizontal and vertical distribution of the total-Hg (T-Hg) concentration in sediments with different particle sizes in the Yatsushiro Sea. From the experiment result, it could be concluded that overall, in the horizontal direction, the T-Hg concentration became smaller and smaller along A and B lines from the sampling point Y28, indicating the mercury transport from Minamata Bay to the Yatsushiro Sea. Moreover, the T-Hg concentration increased first and then decreased in the vertical direction, suggesting that the migrated mercury was mainly deposited in the upper sediments. Furthermore, according to the classification experiment results, the smaller the particle size, the higher the T-Hg concentration. And, the sediment particles migrating from Minamata Bay to the Yatsushiro Sea are mainly very fine slit to fine silt.
