Iron ion supply fertilizer-encapsulating material, iron ion supply method, and seaweed bed formation method

Abstract

To provide an iron ion supply fertilizer-encapsulating material, enabling stable elution of an organic iron component from an iron ion supply fertilizer by allowing both diffusion of the organic iron component to outside of the fertilizer and delay of oxidation of ferrous iron inside the fertilizer.SOLUTION: An iron ion supply fertilizer-encapsulating material 1 is employed that comprises a particulate material 3 and an iron ion supply fertilizer 2 encapsulated in the particulate material 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an iron ion supply fertilizer-containing material that is installed in aquatic areas, particularly in the sea, and contains, in powder and granular form, an iron ion supply fertilizer material that serves as nutrients for algae and microorganisms growing in the aquatic areas, as well as a fertilizer supply method and a seaweed bed creation method that use this iron ion supply fertilizer-containing material. [Background technology]

[0002] In recent years, a decline in biological production due to a lack of iron, which is necessary for the growth of living organisms, has become a problem in marine, freshwater, brackish water, and other bodies of water. For example, in coastal areas around Japan, seaweed has stopped growing on rocky areas, and the area has become covered with calcareous algae, a phenomenon known as rocky shore denudation, which has led to a decline in the populations of kelp, wakame seaweed, and other seaweed species, resulting in barren conditions.

[0003] One of the causes of this coastal bleaching is thought to be environmental changes such as rising sea temperatures and water pollution, as well as the cutting down of trees upstream of rivers that flow into the sea, which has made it difficult for humic acid in the humus soil that was previously formed from the accumulation of fallen leaves to combine with iron in the soil to form humic acid iron, reducing the supply of iron to the sea that is necessary for algae growth.

[0004] To address this issue, a method for protecting the aquatic environment has been known in the past, in which a water-permeable bag material filled with a ferrous-containing substance, such as steel slag, and a humus-containing substance is placed in the sea or other areas (Patent Document 1).

[0005] In addition, a method for preserving the aquatic environment is known in which a hard container with an open top or a hard container with one or more holes is placed near blocks used to create seaweed beds, and the hard container contains a fertilizing material containing steel slag, or a water-permeable bag filled with this fertilizing material (Patent Document 2).

[0006] Furthermore, a method is known for sinking an aquatic environment conservation container on the seabed, which is made up of a container consisting of a bottom surface, a top surface, and side walls that serve as the installation surface, and which contains fertilization material containing steel slag, or a water-permeable bag filled with this fertilization material, and in which a plurality of openings are formed in the top and bottom surfaces for supplying nutrients from the fertilization material, the ratio of the total area of ​​the openings to the total area of ​​the top surface, bottom surface, and side walls being 0.2 to 2.0%, and the ratio of the area of ​​the openings formed in the bottom surface to the total area of ​​the openings formed in the entire container being 30 to 50% (Patent Document 3).

[0007] According to these methods, the divalent iron in steelmaking slag binds with fulvic acid or organic complexes, which are humus-containing substances, to form stable humic acid iron such as fulvic acid, and the humic acid iron diffuses, making it possible to efficiently supply divalent iron ions to water bodies. In other words, divalent iron ions (Fe ) that can be ingested by living organisms are usually 2+ Even if iron is dissolved, it is oxidized by the dissolved oxygen in seawater and immediately settles as solid iron (Fe2O3, Fe(OH)3), making it impossible for living organisms to ingest. However, by using aquatic environment conservation materials such as those mentioned above, it is possible to steadily supply iron as humic acid iron. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-212036 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-330254 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-236571 Summary of the Invention [Problem to be solved by the invention]

[0009] In order to stably dissolve humic acid iron, such as fulvic acid iron, from fertilizer materials such as aquatic environment conservation materials or aquatic environment conservation containers, it is effective to reduce oxidation due to dissolved oxygen, that is, to place the fertilizer materials in an anaerobic environment.

[0010] However, the aquatic environment conservation method described in Patent Document 1 does not consider a specific construction method for maintaining an anaerobic environment in which the fertilizer material (aquatic environment conservation material) is installed.

[0011] In addition, in Patent Document 3, in order to make the internal environment of the fertilizer material (aquatic environment conservation container) anaerobic with a reduced amount of dissolved oxygen, the opening rate of the container is determined so that the amount of dissolved oxygen flowing into the aquatic environment conservation container by passing water does not exceed the amount of dissolved oxygen consumed inside the aquatic environment conservation container.

[0012] However, in general, the greater the concentration gradient at the solid-liquid interface of a substance, the greater the amount of substance eluted from the solid due to diffusion. Therefore, in order for a fertilizer to exert its iron elution effect, it is important to ensure sufficient replacement of seawater inside the fertilizer. If the method shown in Patent Document 3 simply restricts the inflow of seawater into the container in order to reproduce anaerobic conditions, iron ions may remain inside the container and not be able to sufficiently diffuse into the seawater.

[0013] The present invention aims to provide an aquatic environment conservation material, an aquatic environment conservation method, and a method for creating a seaweed bed that enable both the elution and diffusion of humic acid iron from a fertilizer material regardless of the dissolved oxygen environment in the vicinity where the fertilizer material is installed. [Means for solving the problem]

[0014] The present inventors have conducted extensive research to solve the above problems, and have found that by incorporating an iron ion supplying fertilizer into a powder, it is possible to achieve both a delay in the oxidation of divalent iron within the iron ion supplying fertilizer and the diffusibility of divalent iron to the outside, thereby stably eluting iron humate, and have completed the present invention. That is, the gist of the present invention is as follows.

[0015] [1] Granular materials and An iron ion supplying fertilizer material contained in the powder and granules; A material containing an iron ion supplying fertilizer, characterized by comprising: [2] The iron ion supplying fertilizer containing material described in [1], characterized in that the maximum particle size of the particles contained in the powder is 2 mm or more and 30 mm or less. [3] The iron ion supplying fertilizer containing material described in [1], characterized in that the iron ion supplying fertilizer contains steel slag and a humic acid-containing substance. [4] The iron ion supplying fertilizer containing material described in [2], characterized in that the iron ion supplying fertilizer contains steel slag and a humic acid-containing substance. [5] A method for supplying iron ions to a water body, characterized by placing the iron ion supplying fertilizer-containing material described in any one of [1] to [4] in one of the water bodies, namely, sea water, fresh water, and brackish water. [6] The iron ion supplying method described in [5], characterized in that the iron ion supplying fertilizer-containing material is buried at the bottom of the water area. [7] A method for supplying iron ions to a water area described in [5], characterized in that the iron ion supplying fertilizer-containing material is laid on the bottom of the water area. [8] A method for supplying iron ions to a water area described in [5], characterized in that the iron ion supplying fertilizer-containing material is attached in a detachable manner to an artificial or natural structure installed in the water area. [9] A method for supplying iron ions to a water body described in [5], characterized in that the iron ion supplying fertilizer-containing material is attached in a detachable manner near the water surface of the water body.

[10] A method for creating a seaweed bed, comprising using the material containing the iron ion supplying fertilizer according to any one of [1] to [4] to create a seaweed bed. [Effects of the Invention]

[0016] According to the iron ion supply fertilizer-containing material of the present invention, it is possible to achieve both the dissolution and diffusion of humic acid iron regardless of the dissolved oxygen environment around the installation of the iron ion supply fertilizer-containing material, thereby enabling the efficient supply of humic acid iron to algae. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view schematically showing an example of an iron ion supplying fertilizer containing material of the present invention. [Figure 2] 1 is a graph showing an example of the relationship between the dissolved oxygen concentration in the fertilizer dissolution environment and the dissolved dissolved iron. [Figure 3] 1 is a diagram illustrating an example of the present invention; [Figure 4A] This is a graph showing the change in dissolved oxygen concentration inside and outside a material containing an iron ion supplying fertilizer when the material is immersed in seawater. [Figure 4B] This is a graph showing the change in dissolved oxygen concentration inside and outside a material containing an iron ion supplying fertilizer when the material is immersed in seawater. [Figure 4C] 1 is a graph showing the change in dissolved oxygen concentration inside and outside an iron ion supplying fertilizer material when the iron ion supplying fertilizer material is immersed in seawater. [Figure 5A] This is a graph showing the change in dissolved iron concentration inside and outside a material containing an iron ion supplying fertilizer when the material is immersed in seawater. [Figure 5B] This is a graph showing the change in dissolved iron concentration inside and outside a material containing an iron ion supplying fertilizer when the material is immersed in seawater. [Figure 5C] This is a graph showing the change in dissolved iron concentration inside and outside an iron ion supplying fertilizer material when the iron ion supplying fertilizer material is immersed in seawater. [Figure 6] 1 is a schematic diagram showing an example of application of an iron ion supplying fertilizer material containing material according to an embodiment of the present invention. FIG. [Figure 7] 1 is a schematic diagram showing an example of application of an iron ion supplying fertilizer material containing material according to an embodiment of the present invention. FIG. [Figure 8]1 is a schematic diagram showing an example of application of an iron ion supplying fertilizer material containing material according to an embodiment of the present invention. FIG. [Figure 9] 1 is a schematic diagram showing an example of application of an iron ion supplying fertilizer material containing material according to an embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 is a schematic diagram of an iron-ion supply fertilizer-containing material 1 according to this embodiment. The iron-ion supply fertilizer-containing material 1 includes a powder 3 and an iron-ion supply fertilizer 2 contained in the powder 3.

[0019] When the iron ion supply fertilizer-containing material 1 of this embodiment is placed in water, the water permeates into the iron ion supply fertilizer 2, and organic iron such as iron humate is eluted from the iron ion supply fertilizer 2. The eluted organic iron diffuses into the powder / granular material 3 and then moves from the powder / granular material 3 into the external water. It is then supplied as a nutrient component to marine organisms such as algae and microorganisms growing in the water.

[0020] 1, the iron ion supplying fertilizer material 2 may be contained in the powder granule 3 in the form of a single mass, or may be contained in two or more masses in the form of a single powder granule 3. It is preferable that the iron ion supplying fertilizer material 2 is contained in the form of a single mass in the powder granule 3.

[0021] The shape of the iron ion supplying fertilizer containing material 1, that is, the outer shape of the powder granules 3, is not particularly limited, and may be spherical, rectangular parallelepiped, or the like.

[0022] More specifically, the iron-ion supplying fertilizer-containing material 1 can be exemplified by a container having a specific shape, filled with powder 3, and the iron-ion supplying fertilizer material 2 disposed inside the filled powder 3. The container should be configured to allow water to flow into it. In other words, the iron-ion supplying fertilizer-containing material 1 should have a structure that places the powder 3 between the iron-ion supplying fertilizer material 2 and the water that constitutes the water area.

[0023] The container is preferably made of a material that does not contaminate water when it comes into contact with water. Furthermore, the container only needs to be strong enough to prevent breakage or collapse when filled with the iron ion supply fertilizer-containing material 1 or when placed in water, and to prevent the iron ion supply fertilizer-containing material 1 from being scattered. Examples of suitable containers include baskets made of steel, wood, or stone, bags made of mesh made of chemical or natural fibers, and bags made of sheets made of chemical or natural fibers.

[0024] The powder 3 is an aggregate of particles. Therefore, when the iron-ion supply fertilizer-containing material 1 is placed in water, the water around the iron-ion supply fertilizer-containing material 1 permeates the powder 3 and reaches the iron-ion supply fertilizer 2.

[0025] The material of the powder 3 may be any material that does not pollute water when placed in water. Examples of the powder 3 include natural materials such as sand and gravel, artificial stones such as hydrated slag, or combinations of these. However, the powder 3 is not limited to these.

[0026] The maximum particle size of the particles constituting the powder 3 is preferably 2 mm or more and 30 mm or less. This allows the dissolved oxygen concentration in the leaching environment of the iron ion supplying fertilizer material 2 to be maintained at less than 4.5 mg / L.

[0027] In order to obtain the effect of eluting divalent iron enough to maintain seaweed colonies in the water area using the iron ion supply fertilizer-containing material 1 of this embodiment, it is said that the iron concentration in the water area needs to be 100 nM or more, i.e., 5.58 μg / L or more. If the dissolved oxygen concentration of the water contained within the iron ion supply fertilizer material 2 mass is less than 4.5 mg / L, the dissolved iron concentration in the water surrounding the iron ion supply fertilizer-containing material 1 is maintained at 10 μg / L or more, making it possible to supply a sufficient amount of iron for seaweed growth. In order to maintain the dissolved oxygen concentration of the water contained within the iron ion supply fertilizer material 2 mass below 4.5 mg / L, as described above, the maximum particle size of the powder 3 should be 2 mm or more and 30 mm or less.

[0028] If the maximum particle size of the powder 3 exceeds 30 mm, the amount of water that penetrates from the outside of the iron-ion supply fertilizer-containing material 1 into the inside of the iron-ion supply fertilizer 2 increases, which increases the supply of dissolved oxygen, creating an aerobic environment for the leaching of organic iron, rapidly oxidizing the divalent iron, and reducing the amount of organic iron produced. On the other hand, if the maximum particle size is less than 2 mm, the water is not sufficiently replaced inside the iron-ion supply fertilizer 2, the amount of oxygen in the water contained inside the iron-ion supply fertilizer 2 decreases, the leaching of divalent iron is slowed, and the diffusion of organic iron within the powder 3 is also hindered, resulting in a decrease in the amount of divalent iron leaching into the external water. By setting the maximum particle size of the powder 3 to be between 2 mm and 30 mm, it is possible to achieve both the leaching and diffusion of organic iron from the iron-ion supply fertilizer 2.

[0029] The maximum particle size of the powder or granular material 3 is determined, for example, by the size of the openings of a sieve through which all of the powder or granular material passes. The powder or granular material 3 may be of uniform particle size, but preferably has an average particle size of 0.8 to 20 mm and a particle size distribution below the maximum particle size. Examples include natural sand and crushed stone.

[0030] The volume ratio of the iron ion supplying fertilizer material 2 to the powder granules 3 must be such that a powder granule diffusion layer of sufficient thickness can be formed to limit the penetration of water from the external water into the iron ion supplying fertilizer material 2, and it is preferable that the volume ratio of powder granules / iron ion supplying fertilizer material be 16.5 or more.

[0031] The iron ion supplying fertilizer material 2 may be any material that is placed in a water area and used as a fertilizer source for algae such as kelp and wakame seaweed, and is not particularly limited to this. Examples include fertilizer materials containing pure iron or alloys such as scrap iron, and fertilizer materials containing iron oxide such as scale sludge, iron cuttings, red rust, and steel slag.

[0032] In particular, a slag-based fertilizer, which is a mixture of steel slag and a humic acid-containing substance, is preferably used as the iron ion supply fertilizer 2. The slag-based fertilizer can improve the efficiency of the elution performance of organic iron, which is generated when humic acid, a chelating agent, coordinates with iron ions, and is therefore preferably used as a fertilizer that supplies iron mainly to water bodies.

[0033] Steelmaking slag is a source of iron, and it is preferable to use steelmaking slag with a relatively high iron content (total iron content of about 20% by mass or more). Examples of steelmaking slag include converter steelmaking slag and electric furnace steelmaking slag, hot metal pretreatment slag and secondary refining slag produced in a high-grade steel production process that includes processes before and after the converter (hot metal pretreatment, secondary refining), and even carbonated steelmaking slag that has been previously carbonated.

[0034] Humic acid-containing substances are a general term for organic substances containing humic acid or fulvic acid, and a representative example is soil humus, which is a heterogeneous aggregate of large yellow to black organic molecules that is produced during the decomposition of plant litter such as fallen leaves, fallen trees, and thinned wood by soil microorganisms.

[0035] Examples of humic acid-containing substances other than soil humus include artificial humus. Artificial humus can be obtained by fermenting organic matter such as thinnings, food waste, and seafood processing residues. Artificial humus can also be obtained by chemically processing lignite, as in the case of commercially available fertilizers (such as Denka Azumin Fertilizer, Azumin). Artificial humus is rich in inorganic nitrogen and phosphorus, which can be easily absorbed as nutrients. When using the iron ion supply fertilizer-containing material 1, these nutrients are dissolved and become a source of nitrogen and phosphorus. Only one of these humic acid-containing substances may be used, or two or more may be used in combination. The humic acid in this humic acid-containing substance acts as an iron chelator. Therefore, when mixed with steel slag, the iron dissolved from the slag forms a complex with the humic acid, remaining dissolved in the water for a long time, allowing algae to absorb the iron.

[0036] The iron ion supplying fertilizer material 2 may be encapsulated in its entirety in the powder granule 3, or may be encapsulated in the powder granule 3 after being filled in a water-permeable bag of an easy-to-handle size. The role of the water-permeable bag is to prevent the iron ion supplying fertilizer material 2 from scattering when encapsulating it in the powder granule 3 and to ensure good handling.

[0037] The material of the water-permeable bag body is not particularly limited as long as it is a material that does not pollute the water quality when it comes into contact with water, such as inorganic chemical materials such as polyvinyl chloride, polyethylene, polyurethane, polylactic acid, natural organic materials including plant fibers such as hemp and palm, or combinations of these, and is strong enough not to break when the iron ion supply fertilizer material 2 is packed in or placed in water, and can fulfill the above-mentioned role.

[0038] Furthermore, even if the material of the water-permeable bag does not elute divalent iron ions or iron fulvic acid, it can be used as long as it is made by weaving a fibrous material into a water-permeable bag material or by processing it to provide holes for elution. The size of the gaps in the stitches or the holes created by processing is not particularly specified, as long as it is large enough to allow divalent iron ions and iron fulvic acid to pass through, but is small enough to prevent the iron ion supply fertilizer material 2 from being sucked out and causing significant turbidity in the surrounding water area.

[0039] Next, the method for supplying iron ions to a water area according to this embodiment will be described. In the method for supplying iron ions to a water area of ​​this embodiment, the iron ion supplying fertilizer-containing material 1 is placed in one of the water areas, which are ocean water, freshwater water, and brackish water water.

[0040] Specific embodiments include the following. The iron ion supplying fertilizer-containing material 1 is buried at the bottom of a water area (Figure 6). The iron ion supplying fertilizer-containing material 1 is laid on the bottom of the water area (Figure 7). The iron ion supplying fertilizer containing material 1 is detachably attached to an artificial or natural structure installed in a water area (FIG. 8). The material 1 containing the iron ion supplying fertilizer is attached in a detachable manner near the water surface of the water area (FIG. 9).

[0041] When laying the iron-ion supplying fertilizer-containing material 1 on the bottom of a body of water such as the sea, freshwater, or brackish water (estuary), the iron-ion supplying fertilizer-containing material 1 is stored in a container or bag, which is then laid on the bottom of the body of water, as shown in Figure 7. Alternatively, as shown in Figure 6, the soil at the bottom of the body of water may be used as powder, and the iron-ion supplying fertilizer material 2 may be laid by burying it in the soil at the bottom of the body of water during construction. Here, the bottom of the water area can be exemplified by the bottom of the sea, river, lake, or swamp.

[0042] When burying material 1 containing iron ion supplying fertilizer at the bottom of a body of water such as the sea, freshwater, or brackish water (estuary), the soil at the bottom of the water in the construction area, such as in a coastal area, is dug up to create a depression, and material 1 containing iron ion supplying fertilizer is buried at the bottom of the water. The depression after installation needs to be in a form that does not prevent the elution of organic iron from material 1 containing iron ion supplying fertilizer, and material 1 containing iron ion supplying fertilizer may be in direct contact with the water, or may be covered with a thickness of soil that does not affect the elution.

[0043] As shown in Figure 8, when the iron ion supplying fertilizer-containing material 1 is attached in a detachable manner to the surface of a structure 7 of an artificial structure or natural structure in a water area such as the sea, freshwater, or brackish water (estuary), although there are no particular restrictions, it is preferable to place the iron ion supplying fertilizer-containing material 1 in a container or bag to ensure good handling.

[0044] "Removable from the surface of a structure" means that the iron ion supply fertilizer-containing material 1, whose fertilizing effect has been reduced, can be removed, the contained iron ion supply fertilizer 2 can be taken out, and new iron ion supply fertilizer 2 containing a sufficient amount of fertilizing components can be re-encapsulated and re-attached to the structure to which it was originally attached. The method of attachment to the structure 7 is not particularly limited, but examples of attachment methods include tying with a string or attaching with a removable hook as the attachment jig 8.

[0045] The artificial structure is not particularly limited as long as it is a structure to which iron ion supply fertilizer-containing material 1 can be attached on the surface or bottom of freshwater, brackish water, or seawater along the coast, but examples include artificially molded and solidified structures, structures for offshore wind power generation, civil engineering materials such as soil and sand packed in sandbags, etc.

[0046] The natural structure is not particularly limited as long as it is a structure to which the iron ion supplying fertilizer containing material 1 can be attached on the surface or bottom of freshwater, brackish water, or seawater along the coast, but examples include rocks and bedrock.

[0047] As shown in Figure 9, when installing the iron-ion supplying fertilizer-containing material 1 so that it can be detached from the water surface in a body of water such as the sea, freshwater, or brackish water (estuary), it is preferable to place the iron-ion supplying fertilizer-containing material 1 in a bag made of a net or basket made of chemical or natural fiber to ensure good handling. To install the iron-ion supplying fertilizer-containing material 1 so that it can be detached from the water surface, for example, the iron-ion supplying fertilizer-containing material 1 can be hung from a structure 7 such as an aquaculture facility or a floating raft on the water surface using a string, hook, or the like as an attachment jig 8.

[0048] Furthermore, the method for creating a seaweed bed of this embodiment uses the above-mentioned material containing an iron ion supplying fertilizer to create a seaweed bed.

[0049] For example, materials containing iron ion supplying fertilizers, as shown in Figure 1, can be placed in waters where the restoration or creation of seaweed beds is required, such as coastal barren sea areas. Examples of waters include beach nourishment, tidal flats, shallow areas, seaweed beds, and fishing grounds. Note that waters where materials containing iron ion supplying fertilizers are placed with the intention of creating tidal flats or seaweed beds also include waters that have not yet become tidal flats or seaweed beds.

[0050] The iron ion supply fertilizer-containing material of this embodiment can be installed at any position in the water. In situations where sunlight necessary for photosynthesis reaches the bottom of the water, or where organic iron eluted from the iron ion supply fertilizer-containing material is carried to a location where photosynthesis is possible due to upwelling currents, etc., it can be buried or laid at the bottom of the water. Furthermore, in cases where the water is deep, it can be detachably attached to an artificial or natural structure installed in the water, or detachably attached near the water surface of the water, allowing it to be installed at any depth in the water. The iron ion supply fertilizer-containing material of the present invention can be prepared in large quantities in advance or manufactured during the installation process. Specific examples of the iron ion supply fertilizer-containing material are shown in Figures 6 to 9. [Example]

[0051] The iron ion supplying fertilizer containing material of the present invention will be specifically described below.

[0052] [Test Example 1] Examination of the relationship between dissolved oxygen concentration during leaching and iron ion leaching In this test, the iron ion supplying fertilizer was placed in a 2 L container, and seawater was passed through it to adjust the dissolved oxygen concentration in the elution environment to 1.4 mg / L, 2.0 mg / L, 3.3 mg / L, and 4.8 mg / L. The dissolved iron concentration of the eluate at each dissolved oxygen concentration was measured using a micro-iron meter using the luminol luminescence method. The dissolved iron concentration was measured for the eluate after filtering through a 0.45 μm pore size filter.

[0053] To adjust the dissolved oxygen concentration, two types of seawater were prepared for flow; one was aerated with nitrogen to a dissolved oxygen concentration of 0%, and the other was aerated with air to a dissolved oxygen concentration of 100%. The dissolved oxygen concentration was checked every 15 minutes, and the amount of these two types of seawater added was adjusted to maintain a constant dissolved oxygen concentration.

[0054] The steel slag used was a carbonation-treated converter steelmaking slag with the composition shown in Table 1 below. The humic acid-containing material used was artificial humus obtained by fermenting thinned wood, seafood processing residues, and cow manure. The steel slag and humic acid-containing material were mixed in a mass ratio of 2:1 to prepare an iron ion supply fertilizer.

[0055] [Table 1]

[0056] Next, 400 g of the prepared iron ion supply fertilizer was placed in a 2 L sealed glass container. A dissolved oxygen concentration sensor was attached to the container, and the dissolved oxygen concentration of the seawater in the container was measured. Natural seawater collected from Tokyo Bay was then filtered through a glass fiber filter to prepare filtered seawater. This filtered seawater was divided into two portions: one was aerated with nitrogen to a dissolved oxygen concentration of 0%, and the other was aerated with air to a dissolved oxygen concentration of 100%. The filtered seawater with the adjusted dissolved oxygen concentration was pumped through the 2 L glass container, and the dissolved oxygen concentration was measured approximately every 15 minutes. The amount of filtered seawater with the adjusted dissolved oxygen concentration was varied to maintain a constant dissolved oxygen concentration for approximately 3 hours. During the period when the dissolved oxygen concentration was constant, water was sampled from the container using a tube, and the dissolved iron concentration of the water after filtration through a 0.45 μm pore size filter was measured.

[0057] The relationship between the dissolved oxygen concentration in the leaching environment and the dissolved iron concentration in the leaching solution is shown in Figure 2. The dissolved iron concentration decreased when the dissolved oxygen concentration increased from 1.35 mg / L to 2.01 mg / L, then remained constant up to 3.32 mg / L, and then decreased further at 4.81 mg / L. The results showed that the dissolved oxygen concentration in the leaching environment affects the leaching of iron from the iron ion supply fertilizer, and that a dissolved oxygen concentration of 4.5 mg / L or higher is particularly difficult to say is an optimal dissolved oxygen environment for iron leaching.

[0058] [Test Example 2] The relationship between the dissolved oxygen concentration inside and outside of the iron ion supply fertilizer material, in which the iron ion supply fertilizer material is contained in powder, was investigated.

[0059] In this test example, three 20 L containers were prepared. The first container was filled with iron-ion supply fertilizer-containing material 1, which was made by encapsulating iron-ion supply fertilizer material 2 in sand (granular material 3) with a maximum particle size of 2 mm. The second container was filled with iron-ion supply fertilizer-containing material 1, which was made by encapsulating iron-ion supply fertilizer material 2 in pebbles (granular material 3) with a maximum particle size of 25 mm. 10 L of natural seawater was added to each container, and the dissolved oxygen concentration and dissolved iron concentration were measured inside iron-ion supply fertilizer material 2 and outside iron-ion supply fertilizer-containing material 1.

[0060] More specifically, iron ion supplying fertilizer 2 was prepared in the same manner as in Test Example 1. Three 20 L polypropylene (PP) pails with an inner diameter of 300 mm were prepared, along with sand with a particle size of less than 2 mm and pebbles with a particle size of 20 to 30 mm as powder 3. Sand was placed in the first pail a, as shown in Figure 3(a), and pebbles were placed in the second pail b, as shown in Figure 3(b), so that the height from the bottom to the surface of each pail was 100 mm. Then, a burlap bag containing 1 kg of a slag-based fertilizer (iron ion supplying fertilizer 2) containing steel slag and humic acid-containing substances was placed in each pail. Sand was placed in the first pail, and pebbles in the second pail, so that the height from the bottom to the surface of each pail was 200 mm, thereby containing the slag-based fertilizer (iron ion supplying fertilizer 2). Furthermore, as shown in Figure 3(c), the third pail c contained only a burlap bag containing 1 kg of slag-based fertilizer (iron ion supply fertilizer 2).

[0061] As shown in Figures 3(a) to 3(c), 10 L of Tokyo Bay filtered seawater was poured into each pail and immersed. To simulate a real-world ocean environment, a propeller 4 was installed at a position submerged in the seawater at the top of the pail, and the propeller was constantly stirred at approximately 120 rpm. During the test, the water temperature in the test equipment was approximately 23°C. Half of the Tokyo Bay filtered seawater was replaced with fresh Tokyo Bay filtered seawater every 1 to 3 days. This procedure was repeated for 17 days. The dissolved oxygen and dissolved iron concentrations were periodically measured inside the slag-based fertilizer, in the seawater outside the fertilizer-containing material 5, and in the seawater outside the fertilizer 6. The dissolved iron concentration was measured using water filtered through a 0.45 μm pore size filter.

[0062] The changes in dissolved oxygen and dissolved iron concentrations over time are shown in Figures 4A-4C and 5A-5C. The seawater 5 and 6 outside the fertilizer-containing material were constantly maintained in an aerobic environment with a dissolved oxygen concentration of approximately 6.0 mg / L. Furthermore, the dissolved oxygen concentrations inside the slag-based fertilizer were 1.7 mg / L to 3.1 mg / L for pail a, 2.4 mg / L to 4.5 mg / L for pail b, and approximately 4.5 mg / L for pail c. The dissolved iron concentrations inside the slag-based fertilizer were in the following order: pail a > pail b > pail c. The dissolved iron concentrations in the seawater 5 outside the fertilizer-containing material and the seawater 6 outside the fertilizer were 0.02 to 0.10 mg / L in pails a and b, while in pail c the maximum was around 0.04 mg / L, which was generally lower than in pails a and b.

[0063] In this way, the fertilizer-containing material of the present invention increases the dissolved iron concentration in seawater compared to the fertilizer alone, making it possible to efficiently supply iron. Table 2 shows the relationship between powder particle size, dissolved oxygen concentration inside the fertilizer, diffusibility into external seawater, and organic iron elution.

[0064] [Table 2] [Explanation of symbols]

[0065] 1: Iron ion supply fertilizer containing material 2: Iron ion supply fertilizer 3: Powder 4: Stirring propeller 5: Iron ion supply fertilizer material containing material outside seawater 6: Iron ion supply fertilizer external seawater 7: Man-made or natural structures 8: Mounting jig

Claims

1. A powder and a granular material, An iron ion supplying fertilizer material contained in the powder and granules; A material containing an iron ion supplying fertilizer, characterized by comprising:

2. 2. The iron ion supplying fertilizer containing material according to claim 1, wherein the maximum particle size of the particles contained in the powder is 2 mm or more and 30 mm or less.

3. The iron ion supplying fertilizer containing material according to claim 1, characterized in that the iron ion supplying fertilizer contains steel slag and a humic acid-containing substance.

4. The iron ion supplying fertilizer containing material according to claim 2, characterized in that the iron ion supplying fertilizer contains steel slag and a humic acid-containing substance.

5. A method for supplying iron ions to a water area, characterized in that the iron ion supplying fertilizer containing material described in any one of claims 1 to 4 is placed in one of a sea area, a freshwater area, and a brackish water area.

6. 6. The method for supplying iron ions according to claim 5, wherein the material containing the iron ion supplying fertilizer is buried in the bottom of the water area.

7. 6. The method for supplying iron ions to a water area according to claim 5, wherein the iron ion supplying fertilizer-containing material is laid on the bottom of the water area.

8. 6. A method for supplying iron ions to a water area as described in claim 5, characterized in that the iron ion supplying fertilizer-containing material is removably attached to an artificial structure or natural structure installed in the water area.

9. 6. The method for supplying iron ions to a water area according to claim 5, wherein the iron ion supplying fertilizer containing material is detachably attached near the water surface of the water area.

10. A method for creating a seaweed bed, comprising creating the seaweed bed using the iron ion supplying fertilizer containing material according to any one of claims 1 to 4.

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