2023 Volume 79 Issue 17 Article ID: 23-17143
In this study, we focused on the circulation of sulfides, iron, and manganese in the enclosed water area of Tokyo Bay. We conducted field observations and numerical analysis using a three-dimensional coupled model of the pelagic and benthic systems. Through load surveys of rivers, we created a quantitative formula for the forms of Fe and Mn in the Arakawa and Tama rivers and calculated the load of each river. Additionally, analysis of water and sediment samples in the bay revealed an increase in P-Fe in the anoxic bottom layer where H2S was present, suggesting that the formation of oxidized iron resulted from the reaction between H2S and Fe2+. On the other hand, D-Mn was found to be highly concentrated due to leaching from the sediment under anoxic conditions (ORP <-200 mV). In the analysis using the three-dimensional coupled model, there are challenges such as overestimation of H2S in sediments and underestimation of D-Mn in the water column. However, the model was able to generally reproduce the vertical distribution of DO, D-Fe, H2S in the water column, and D-Fe, D-Mn in the sediment.
