In eutrophic coastal regions, hydrogen sulfide (H2S) is a harmful material released from sediments under anoxic conditions. To suppress its release, we conducted laboratory experiments and assessed the impacts of treatment with three iron materials (Fe, Fe2O3, and FeOOH), focusing on the area-specific H2S release rate. These materials qualitatively exhibited a substantial suppression of H2S release; however, smaller treatment levels (<150 mmol m-2) were ineffective. FeOOH exhibited the best performance, followed by Fe2O3, and Fe. These differences were likely caused by variations in the oxidation or reduction potential of the materials and their reaction rates with H2S. A simplified model suggested that the required minimum Fe2+ concentration was determined using the H2S diffusivity, reaction rate constant, and treatment penetration depth. As the former two are physical constants, the latter must control the H2S release rate. Iron materials were experimentally confirmed to persist for over three weeks, and the effective treatment level was theoretically estimated as being capable of suppressing H2S release for more than a year. Our results will contribute to coastal environmental management and particularly benefit port authorities who manage enclosed and eutrophicated harbors and navigation channels where slag application should be avoided.