One reason for the evolution of barren ground in coastal areas is a deficiency of dissolved Fe(Il) species. A fertilizer that included steel slag and compost was evaluated, in an attempt to supply dissolved Fe (II) to coastal such areas. Basing on previously reported data, it is thought that the presence of fulvic acid (FA) in the compost permits Fe (II) in the steel slag to be eluted in the form of Fe (II) -FA complexes. However, in our observation and some previous reports, humic acid (HA) and FA are flocculated and precipitated in seawater. which suggests that FA cannot function as a carrier for the elution of Fe (II) from the fertilizer. To better understand the mechanisms that control the elution of Fe (II) from such a fertilizer, this paper introduced following two topics: (1) the seawater extractable organic matter (SEOM) in the compost and its binding to Fe (II), and (2) the alteration of HA in the fertilizer during fertilization. For the first topic, the SEOM contained less carboxylic and phenolic hydroxyl groups that can serve as binding sites to Fe (Ⅱ), compared to HA and FA. However, the binding constant of the Fe (II) -SEOM complex was comparable to that of the Fe (II) -fulvic acid complex. These results suggest that SEOM in the compost has strong binding sites to Fe (II) and can serve as a carrier of Fe (II) in seawater. For the second topic, the structural features of the organic matter in the fertilizer were monitored during 6 months of fertilization, in which HA was characterized as an abundant organic matter in the fertilizer. While no significant structural alterations of the HA were observed in the absence of steel slag, the structures were dramatically altered in the presence of steel slag. Higher levels of sulfur and a fatty acid biomarker(C16:1w7) were found in the HA after fertilization, suggesting that sulfate reducing bacteria are involved in the observed structuralalterations.
The fundamental studies on spatial distribution of metal elements, particularly essential elements such as iron, and the global circulation from geo-environment through aquatic environment are summarized in the article. The elution promotion of iron and the formation of complex between fumic substances and iron are considered to be an important process to rehabilitate the coaslal environment, because the organic complex of iron, fulvic acid iron and humic acid iron, are soluble substances in aquatic environment and can be directly utilized for marine algae. The coupled utilization of steel slag and humic substances can promote the elution of essential minerals enabling rehabilitation of coastal environment. These fundamental researches can provide various useful information and data needed for the proposed green innovative technology.
Barren grounds in coastal area are serious problems in Japan and throughout the world. Although several reasons were proposed to account for barren grounds, the shortage of dissolved iron has been especially focused in recent years. Supplying steelmaking slag and humus materials, such as compost, was proposed for restoring seaweed beds. Iron concentration in seawater could be increased if a mixture of slag and compost were supplied, since complexes, iron-humates, were produced from iron in slag and humic substances in compost. The field experiment was attempted on the side of Sea of Japan in Hokkaido and the restoration of seaweed bed from barren ground could be confirmed. This method contributes not only to restoration of coastal environment, but also to the efficient use of by-products and unutilized biomass. However, dependence of seaweed beds on water environment of coastal sea. such as dissolved iron concentration, should be understood more precisely so that this method is installed without negative impact on coastal ecosystem. In this study, two topics were investigated for understanding relationship between dissolved iron concentration and the growth of seaweed beds. The first was to evaluate the linkage between forest, river and sea based on iron. The dissolved iron concentration in seawater and river water, and the amount of humic substances and iron in soil were investigated in Okushiri Island. Hokkaido. The second was to develop a model of the seaweed growth in coastal ecosystem for evaluating the main possible factor that reduces seaweed beds. The importance of dissolved iron in seawater for the growth of seaweeds was found with this model. The model is useful for understanding the conditions of coastal environment and for deciding an appropriate method for restoration of seaweed beds from barren grounds.
We would introduce the developed new technologies to restore the marine environment by means of applying the steelmaking slag. First of them is the technology to recover the seaweeds beds which was destroyed by sea desertification and to create the marine forest. We have developed the new marine fertilizer called ”Ferrous supply unit” made of steel slag and humus soil, and also developed the artificial stone made of GBFS(Granulated Blast Furnace Slag) and steel slag. Second of them is the technology to construct the tide land and to purify the enriched seabed. We developed the method of making the improved soil by means of mixing the dredged soft clay and steel slag.
The results of two project concerning about improvement of marine environment by steelmaking slag are reported in this paper. One is ”Project of research on algae leaf development made of steelmaking slag for capturing CO2 and demonstration at KAWASAKI city” subsidized by the Ministry of Economy. Trade and Industry (METI). And the other is the project named ”environmental technology verification (ETV)” in fiscal year 2009. which is a project undertaking Ministry of the Environment. Technologies of ”Algae leaf development and water purifying by steelmaking slag” and ”Improvement of marine environment by BOP slag products” are recognized.
There are many borrow pits, caused by the sand mining at the bottom of the coastal sea in Japan. Borrow pits have been identified as a source of oxygen-deficient water killing benthic fauna by hydrogen sulfide. And, much nutrients such as nitrogen or phosphorus tend to release from the bottom of borrow pits, which is attributed to red tide. From these reasons, it has become more important to restore borrow pits for marine environment improvement. But, a large amount of earth and sand materials are needed to restore borrow pits. Then, we have examined the restoring borrow pits process by ”slag mixture material” mixing the steelmaking slag that is the by-product of the steel industry with the dredged material generated by the sea route maintenance. In this study, firstly, by the experiment using ”slag mixture material”, we examined the sulfide generation control effect and the microalgae generation control effect by phosphorus release control. Then, by the developed ”biogeochemical model” based on the experiment, we predicted the improvement effect when ”slag mixture material” are applied to a borrow pit of Osaki area in Mikawa Bay. As a result of that, ”slag mixture material” decreased 92% of the reduction material release such as hydrogen sulfide. And. compared with dredged material, ”slag mixture material” decreased 26% of the reduction material release. The prediction shows the ”slag mixture material” bring larger improvement effects. The restoring borrow pits process by ”slag mixture material” mixing the steelmaking slag is more effective for marine environment improvement.
Discoloration of nori, Porphyrayezoensis, is a terrible economic problem for the fisheries. One of the reasons for the discoloration of nori is suggested the decreasing concentrations of nutrients, nitrogen and phosphorus. The red tide by some diatom, rainfall, and so on cause the bad balance of water quality. Recently, it was showed that iron is important for the color maintenance of nori. Sea desertification, isoyake. can be seen in some Japanese coastlines. It is suggested that one of the reasons for this phenomenon is the decreasing concentrations of nutrients and iron. Against this backdrop, the fertilizer has been produced using steel-making slag and humus soil, which can stably supply iron and some nutrients. We have demonstrated the effect of the fertilizer on algal growth in Japan. In this study, we studied the effect of the fertilizer to the growth of nori by the mesocosm experiment Both of experimental tanks for the mesocosm were set up nori-meshes. and 60 kg fertilizer in one side, while the other tank was no fertilizer as a control. We surveyed the concentration of nutrients and trace metals, and the growth of nori. As a result, in the fertilizer containig tank the concentration of nitrogen, phosphorus and iron were raised, in brief the nutrients and iron eluted from the fertilizer. And only in the fertilizer containig tank, nori grew up over 10 cm in length. On the other hand, we could not identify the growth of nori by visual observation in the control tank, fertilizer not containing tank.