抄録
In enclosed coastal seas in Japan, water quality has been getting better and even more in "oligotrophic" state in some areas due to the reduction measure of land loads enacted in 1970s. On the other hand, the sediment is deteriorated with organic matter and sometimes produces hydrogen sulfide forming oxygen depleted water. To remediate such two contradictory conditions, in the present study, we developed a kind of fertilizer which supplies excess iron along with other nutrients. Iron can be a key essential element simultaneously to enhance the primary production and to suppress hydrogen sulfide. Iron powder that was used as a reference material to steelmaking slag was much effective in terms of iron elution. On the other hand, coal ash was useful to release macronutrients (N, P and Si) and Mn and Zn. To elute iron effectively from the pan-granulated materials, citric acid was selected as both a chelating agent of iron ion and a binder. Carbon pitch cokes which is believed to form an electrochemical cell and release divalent iron ion into the water was not so effective. The final product developed in the present study elutes iron excessively compared to macronutrients. Therefore, the products can be utilized for restoration of coastal marine ecosystems where the water is in the oligotrophic state and the sediment is as much eutrophic as producing hydrogen sulfide.
