JP2005281439A - Soil aggregate for improving bottom sediment, bottom sediment improvement method and water bottom ground - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soil aggregate which is suitable for improving bottom sediment of various water areas including seaweed bed. <P>SOLUTION: An improver system 3 containing a double-shaft stirring blade 5 is held at the tip of a ladder 2 extending from a workboat 1. The improver system 3 is sunk to water bottom, and an aqueous solution containing an aggregating agent and an adsorption carrier carrying a hydroxy metal ion is supplied to the improver system 3 from a first mixer 11 mounted on the workboat 1 and mixed with bottom mud S of the bottom sediment to promote aggregation of the bottom mud S. After the aggregation has moderately progressed, an aqueous solution containing a solidifier is supplied to the improver system 3 from a second mixer 12 mounted on the workboat 1 to promote further aggregation and solidification and replace the bottom sediment with the water-resistant soil aggregate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to aggregated soil used for improving bottom sediments of sea areas, lakes, rivers, and the like, a bottom sediment improvement method performed using the aggregated soil, and water bottom ground in which bottom sediment is improved by the method.

  For example, seaweed beds and tidal flats in the sea are suitable for the inhabiting of various organisms such as benthic organisms, fish, plankton, birds, aquatic animals and plants, and also contribute to environmental improvements such as water purification and hydrophilicity. For this reason, recently, conservation and regeneration of seaweed beds and tidal flats have become important issues, and various attempts have been made to artificially create seaweed beds and tidal flats.

And conventionally, for example, as a method of artificially constructing a seaweed bed, a method of sinking a mat or concrete structure on which the seeds (seedlings) of aquatic plants such as seaweeds and diatoms are easy to settle (Patent Document 1, 2), or a method of laying and spreading a seeding base (seeding sheet or algae attachment net) to which seeds of aquatic plants have been attached in advance on the seabed (see Patent Documents 3, 4, etc.). However, according to the former method, there is a problem that cost effectiveness is small because it is only expected to naturally seed seeds. In addition, according to the latter method, in order to handle seeds that do not like drying, management of the sowing base is troublesome, and in addition to the troublesome work of spreading the seeding base and fixing it to the seabed, a lot of laying is required. There was a problem of requiring labor and time.
Japanese Patent Laid-Open No. 09-140284 JP 2002-167258 A JP-A-11-308904 Japanese Patent Laid-Open No. 08-242716

  By the way, it has been conventionally known that fine particles in earth and sand are useful for the growth of aquatic plants, particularly seaweeds and diatoms. Therefore, if seaweed or diatomaceous seeds are directly mixed (direct sowing) into sediments with a lot of fine particles, a seaweed bed can be created efficiently without depending on the seeding base. However, the fine particles in the soil have the property of being easy to flow due to the influence of tidal currents and waves. When the direct sowing method is adopted, the seeds also flow out together with the fine particles and are stable. It is difficult to create a seaweed bed.

  While the present inventors are diligently studying the creation of algae beds by the direct sowing method, agglomeration of earth and sand greatly contributes to the prevention of the outflow of seawater and diatom seeds. It was confirmed. Agglomerated soil has a structure in which aggregates formed by collecting soil particles (single grains) are arranged, and has a feature that the amount of pores is large. The soil with this aggregate structure developed has been confirmed to be extremely favorable for the growth of plants because its pores have various functions such as water retention, ventilation, and root growth promotion. The use is planned.

  The present invention was made by paying attention to various functions of the above-mentioned aggregated soil, and the problem is that the aggregated soil is suitable for improving the bottom sediment of various water areas as well as seaweed beds. In addition, it is intended to provide a method for improving the bottom quality by using this aggregated soil and a water bottom ground improved by the construction method.

  In order to solve the above-mentioned problems, the aggregated soil for improving sediment according to the present invention is characterized in that the aggregated material is mixed with an aggregating agent and a solidifying agent. The aggregated soil thus configured is mixed with a solidifying agent, so that aggregation is promoted and solidification is promoted. As a result, water resistance is sufficient and the aggregated structure is maintained over the long term. Is done. In addition, many pores of aggregated soil are suitable not only for aquatic plants but also for aquatic animals, so it is useful for improving the bottom sediments of lakes, rivers, etc. as well as seaweed beds and tidal flats. Become. In addition, since the fine particles are taken into the aggregate structure, the outflow is suppressed, and when seeds such as seaweeds and diatoms are sown therein, the outflow of the seeds is also suppressed.

  In this aggregate grain soil, the generation source of the earth and sand is arbitrary, and may be bottom mud or land earth and sand. However, because fine agglomerates are necessary for the growth of seaweeds and diatoms, sand and mud (particle size less than 0.425mm) is necessary when using aggregated soil for the conservation, regeneration, and creation of seaweed beds. It is desirable to use earth and sand having a particle size composition of 80 to 100% and a mud content (particle size of less than 0.075 mm) of 30% or less.

  In this aggregated grain soil, the amount of the aggregating agent is arbitrary, but it is preferably about 1 to 5% with respect to the dry weight of the soil. This is because if the addition amount is small, the desired aggregate structure cannot be obtained, and if it is too large, the consumption of the aggregate agent is unnecessarily increased and the cost is wasted. Moreover, although the addition amount of a solidifying agent is also arbitrary, it is desirable to set it as about 0 to 2% (however, except 0%) with respect to the dry weight of earth and sand. This is because if the amount of the solidifying agent added is small, the desired water resistance cannot be obtained, and if it is too large, the consumption of the aggregating agent increases unnecessarily and the cost is wasted.

  As the aggregating agent and solidifying agent, a substance that is not harmful to the growth of animals and plants is selected. Examples of such aggregating agents include synthetic organic polymers such as sodium polyacrylate, carboxymethylcellulose, polyacrylamide, and polyvinyl alcohol, and polysaccharides and natural organic polymers such as sodium alginate and chitosan. Examples of the agent include chlorides containing polyvalent cations such as calcium chloride, magnesium chloride, and iron chloride. 1 type or multiple types selected from these substances can be used for this aggregate grain soil.

  This aggregate grain soil may further be mixed with an adsorption carrier supporting a hydroxy metal ion. By mixing such an adsorbent carrier, metal ions serving as nutrients are gradually released from the adsorbent carrier, and the growth environment of aquatic animals and plants is maintained for a long time. In this case, the addition amount of the adsorption carrier is desirably 1 to 10% with respect to the volume of the earth and sand. This is because if the amount of adsorbent carrier added is small, the amount of nutrients supplied is insufficient and the growth of aquatic animals and plants is reduced. This is because if the amount added is too large, the amount of earth and sand is relatively lowered and the agglomeration becomes difficult, so that the growth is lowered. Furthermore, excessive addition causes a decrease in growth according to the law of diminishing yield. In order to support the hydroxy metal ion on the adsorption carrier, the adsorption carrier may be immersed in an aqueous solution containing the hydroxy metal ion. Since the degree of slow release of metal ions from the adsorption carrier is determined by the degree of polymerization (OH / M ratio: M is a metal), this degree of polymerization may be controlled to an appropriate value if necessary.

  When mixing the adsorption carrier carrying the hydroxy metal ion, a substance having excellent ion adsorption ability is selected as the adsorption carrier, and a substance serving as a nutrient for aquatic animals and plants is selected as the metal ion. Such adsorbent carriers include artificial zeolite, natural zeolite, synthetic zeolite, diatomaceous earth, activated carbon, charcoal, silica gel, alumina gel, bentonite, kaolinite, allophane, imogolite, cation exchange resin, corrosive acid, peat, etc. Examples of hydroxy metal ions include hydroxy iron ions, hydroxy copper ions, hydroxy zinc ions, hydroxy cobalt ions, hydroxy molybdenum ions, hydroxy calcium ions, hydroxy magnesium ions, and the like. 1 type or multiple types selected from these substances can be used for this aggregate grain soil.

  The bottom sediment improvement method according to the present invention is characterized in that the above-mentioned aggregated soil is laid on the bottom of the water. By laying the aggregate soil on the bottom of the water in this way, the bottom sediment is improved to an environment that is liable to live in aquatic plants and animals. In this case, the bottom mud of the improved zone may be used as the soil for the aggregate soil, and the bottom mud may be replaced with the aggregate soil, whereby the bottom quality is more reliably improved. When the bottom mud of the improved zone is used as the soil for aggregated soil, the improvement device is lowered from the ship to the bottom of the water, and even if the bottom mud is aggregated in the improved device, The bottom mud may be agglomerated on the ship, and the obtained aggregated soil may be backfilled to the bottom of the water. In any case, since construction can be performed in an improved area (site), transportation of the obtained aggregated soil as well as earth and sand becomes unnecessary. Further, in the former case, the work of dripping the bottom mud becomes unnecessary, and in the latter case, a large amount of processing is possible.

  The water bottom ground according to the present invention is characterized in that the bottom quality is improved by the above-described bottom quality improvement method. In this case, the seedbed of seaweed or diatom is previously sown in the aggregate soil, so that the water bottom ground becomes an algae bed as it is.

  According to the aggregate soil for improving sediment according to the present invention, since the aggregate structure is maintained for a long time with sufficient water resistance, it is suitable for inhabiting aquatic animals and plants, and the sea area of seaweed beds and tidal flats is Of course, it is extremely useful for improving the bottom sediments of lakes and rivers. Moreover, since a fine grain part is taken in in a aggregate structure, the outflow is suppressed and it becomes suitable toward seaweed bed construction, such as seaweeds and diatoms.

  In addition, the bottom sediment improvement method according to the present invention and the bottom sediment whose bottom sediment has been improved by the method are suitable for the inhabiting of aquatic animals and plants by the use of the above-mentioned aggregated soil. Greatly help in the creation of.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 1 and FIG. 2 show one embodiment of the bottom sediment improvement method using the aggregated soil according to the present invention. In this embodiment, the bottom sediment is directly improved at the bottom of the improved area, and the improved device 3 is supported at the tip of the ladder 2 extending from the work boat 1. In this improved device 3, a rotating body 6 having radially stirring blades 5 is arranged in two axes in a casing 4 so that the stirring blades 5 wrap around each other. Each rotating body 6 has a cylindrical shape and is driven to rotate in opposite directions by a motor (not shown). A delivery pipe 7 having a double pipe structure is disposed at the axial center position of each rotary body 6, and one end of each of the rotary bodies 6 is independently connected to two pipe lines in the delivery pipe 7. Each pair of discharge nozzles 8 and 9 is radially arranged with their positions shifted 90 degrees from each other.

  On the other hand, on the work boat 1, the aggregating agent, the first carrier 11 that mixes the adsorption carrier carrying hydroxy metal ions and water at a predetermined ratio, and the solidifying agent and water at a predetermined ratio. A second mixer 12 for mixing is disposed. Each of the first mixer 11 and the second mixer 12 and the improvement device 3 are independently connected by pipes 13 and 14, and the tips of the pipes 13 and 14 in the improvement device 3 are It is connected to a delivery pipe 7 having a double pipe structure via a swivel joint (substantially). The pipes 13 and 14 are provided with pumps 15 and 16, respectively, and a predetermined aqueous solution pumped from the first mixer 11 and the second mixer 12 to the delivery pipe 7 by the operation of the pumps 15 and 16. , And are discharged from the corresponding discharge nozzles 8 and 9 around the rotating body 6.

  When improving the bottom sediment, an aqueous solution of an aggregating agent containing an adsorbent carrier having a predetermined concentration is prepared in advance by the first mixer 11, and an aqueous solution of a solidifying agent having a predetermined concentration is prepared by the second mixer 12. Then, the ladder 2 is operated (winch operation), the improvement device 3 at the tip thereof is settled on the bottom of the water, and the pair of rotating bodies 6 inside is rotated. In this state, first, the operation of the pump 15 on the first mixer 11 side causes the aqueous solution of the aggregating agent containing the adsorption carrier to be pumped from the pipe 13 to the discharge nozzle 8 through the delivery pipe 7, and from this discharge nozzle 8 to the group. A predetermined amount of the granulating agent aqueous solution is discharged around the rotating body 6. Then, the bottom sediment (bottom mud) S and the aggregating agent containing the adsorbing carrier are stirred and mixed by the stirring blade 5 provided in the rotating body 6, and the agglomeration of the bottom mud gradually proceeds. When a predetermined time has elapsed after the stirring and mixing, the solidifying agent aqueous solution is pumped from the pipe 14 to the discharge nozzle 9 through the delivery pipe 7 by the operation of the pump 16 on the second mixer 12 side. A predetermined amount of the granulating agent aqueous solution is discharged around the rotating body 6. Then, the solidifying agent is mixed in the bottom mud where the agglomeration is progressing, and the agglomeration of the bottom mud further proceeds, and the solidification proceeds. By performing this stirring and mixing for a predetermined time, The bottom mud is replaced with aggregated soil with developed aggregate structure and sufficient water resistance. Therefore, by repeating the operation while moving the improvement device 3 at a predetermined pitch by the operation of the ladder 2, the bottom mud in the target improvement area is replaced with the aggregated soil. The reason why the mixing of the solidifying agent is delayed from the mixing of the aggregating agent is to prevent the aggregating agent from reacting with the solidifying agent and solidifying, and as described above, make a time difference. Thus, the mixing of the aggregating agent and the bottom mud is sufficiently promoted, and the agglomeration proceeds efficiently.

  Here, when the seaweed or diatom algae ground is constructed using the bottom sediment improvement method of the above embodiment, a water tank (not shown) in which the seaweed or diatom seeds are suspended on the work boat 1 is used. ), And a separate pipe (not shown) is extended from the work boat 1 into the improvement device 3. Then, at the final stage of the stirring and mixing process in the improvement device 3 described above (slightly before the rotation of the rotating body 6), a necessary amount of seeds is introduced into the improvement device 3 through the pipe. Then, the seed is dispersed and mixed (seeded) in the aggregate soil by the rotation of the stirring blade 5. In this case, it is desirable to stop the rotation of the stirring blade 5 by several rotations after putting the seed into the improvement device 3, thereby preventing the seed from being damaged. In this way, seeds are dispersed and arranged in the improved area improved by the aggregate soil in a state of being captured by the aggregate soil. In this case, since the fine particles are also taken into the aggregate soil, the outflow of fine particles is suppressed even in locations where the tide is intense and large waves are rushed, and as a result, the outflow of seeds is also suppressed, Grows stably. In particular, when the adsorbent carrier supporting hydroxy metal ions is included in the aggregate soil as in the first embodiment, metal ions as nutrients are gradually released, so aquatic plants such as seaweeds and diatoms are used. Is constantly supplemented with the necessary nutrients and grows vigorously.

  FIG. 3 shows another embodiment of the bottom improvement method performed using the aggregated soil according to the present invention. In this embodiment, the bottom quality is improved on the work boat 1 moored in the improved area. On the work boat 1, the backhoe 20 for dredging the bottom mud (sediment) S and the dredged bottom mud are primarily used. A mud storage tank 22 with a screen 21, a biaxial screw type agitator 23 for producing agglomerated soil, a conveyor 24 for conveying soil and sand from the mud storage tank 22 to the agitator 23, and agitator A feeder 25 for backfilling the aggregated soil made at 23 to the bottom of the water is mounted. Also on the work boat 1, as in the above embodiment, the aggregating agent, the first carrier 11 for mixing the adsorption carrier carrying hydroxy metal ions and water at a predetermined ratio, the solidifying agent and water, And a second mixer 12 that mixes at a predetermined ratio.

  When improving the bottom sediment, an aqueous solution of an aggregating agent containing an adsorbent carrier having a predetermined concentration is prepared in advance by the first mixer 11, and an aqueous solution of a solidifying agent having a predetermined concentration is prepared by the second mixer 12. Then, the bottom mud S is scooped by the backhoe 20 and sequentially put into the mud storage tank 22, and the stirrer 23 and the conveyor 24 are driven accordingly. Then, the bottom mud is sent to the stirrer 23 by a fixed amount by the conveyor 24. The bottom mud is first stirred and mixed with the aggregating agent containing the adsorbent carrier supplied from the first mixer 11, and stirred while gradually aggregating. Move to the exit side of the machine 23. On the other hand, the solidifying agent aqueous solution is supplied from the second mixer 11 to the outlet side of the stirrer 23, and the earth and sand in the middle of agglomeration is agitated and mixed with the solidifying agent, thereby further agglomerating the earth and sand. As it progresses, solidification progresses, and as a result, aggregated soil having water resistance is formed. This aggregated soil is continuously extruded onto the feeder 25 from the outlet of the stirrer 23 and backfilled to the bottom of the water by the feeder 25. Therefore, by repeating the above operation while moving the work boat 1 at a predetermined pitch, the bottom mud S in the target improved area is replaced with the aggregate soil.

  Here, when seaweed or diatom algae beds are constructed using the bottom sediment improvement method, a water tank (not shown) in which seaweed or diatom seeds are suspended is prepared on the work boat 1. At the same time, this water tank and the vicinity of the outlet of the stirrer 23 are connected by a pipe (not shown). Then, a necessary amount of seeds is continuously charged into the agitator 23 through the pipe. Then, the seeds are dispersed and mixed (seeded) in the aggregate soil by the rotation of the screw in the stirrer 23. Therefore, the seeds are dispersed and arranged in the improved area replaced with the aggregate soil in a state of being captured by the aggregate soil including the adsorption carrier supporting the hydroxy metal ions, as in the above embodiment. The outflow of seeds of seaweeds and diatoms is suppressed, and as a result, seaweeds and diatoms grow vigorously.

In the two-dimensional long water channel 30 shown in FIGS. 5 (A) and 5 (B), a first container 31 storing the aggregated soil according to the present invention and a second container 32 storing the comparative soil are installed in parallel. Irregular waves (H _1/3 = 18.0 cm, T _1/3 = 1.7 s) are generated in the long channel 30 for 26 minutes by the wave-making plate 34 that operates using the wave machine 33 as a drive source, and the fine particle fraction An outflow experiment was conducted. Aggregated soil is prepared by adding silica sand and artificial zeolite (adsorption carrier) to a 4% aqueous solution of sodium alginate (aggregating agent) so as to have the blending ratio shown in FIG. A 7.35% aqueous solution of calcium chloride (solidifying agent) was stirred and mixed while gradually adding so that the blending ratio shown in FIG. 4 was obtained. And before and after experiment, the particle size distribution was measured about the aggregate soil and the comparison soil.

  FIG. 6 shows the particle size distribution of the aggregate soil before and after the experiment, and FIG. 7 shows the particle size distribution of the comparative soil before and after the experiment. In the case of aggregate soil, as shown in FIG. 6, there is almost no change in the particle size distribution before and after the experiment, that is, before and after the wave action, and no outflow of fine particles is observed. On the other hand, as shown in FIG. 7, in the comparative sediment, the particle size distribution after the wave action is slightly different from the particle size distribution before the wave action on the fine particle side, and the outflow of the fine particles is is happening. In other words, it is clear that the outflow of fine particles can be suppressed by aggregation, and improving the sediment by the aggregate soil creates a very favorable environment for the growth of seaweeds and diatoms. I can say that.

Sand mixed sludge soil (raw mud) collected from Y fishing port, aggregated soil in which sodium alginate as an aggregating agent and calcium chloride as a solidifying agent are mixed with the original mud, and the aggregated soil, An aggregated soil (artificial zeolite-containing aggregated soil) mixed with Fe-type artificial zeolite supporting hydroxy Fe ions was prepared. Then, the three types of test soil are put in a paper pot, and 50 seeds of sea eel are sown in each pot. Two pots are prepared for each of the test soils, and the salt concentration is about It was put in a tank containing 3% seawater. In the test, the water temperature is increased from 10 ° C. necessary for germination of the eelgrass while irradiating the inside of the aquarium and irradiating the light with a white fluorescent light so that the photosynthesis energy of ³ to 4 E / m ² can be obtained. The temperature was gradually increased to 22 ° C., which was suitable for the growth, and the growth of the eel was observed.

  FIG. 8 shows the growth situation of sea cucumber after 3 months. In the figure, the growth number is expressed as an average value between two pots. From this, it was found that the aggregated soil and the artificial zeolite-added aggregated soil both had a significantly increased number of growth relative to the raw mud, and the aggregated soil had a large germination promoting effect and growth promoting effect. In addition, in the comparison between the aggregated soil and the artificial zeolite-containing aggregated soil, there is not much difference between the two, and at this stage, the effect of the artificial zeolite on the growth number is not clear.

  FIG. 9 shows the maximum root length per tree after 3 months. From these results, it was confirmed that the aggregated soil and the artificial zeolite-containing aggregated soil each had a maximum root length per one of the raw mud, and the aggregated soil had an effect of increasing the root length. In addition, in comparison between aggregated soil and artificial zeolite-containing aggregated soil, artificial zeolite-added granular soil has a longer root length than aggregated soil without artificial zeolite, and artificial zeolite has an effect of increasing root length. It was confirmed that it had.

  Prepare Ca-type artificial zeolite supporting hydroxy Ca ions and Fe-type artificial zeolite supporting hydroxy Fe ions, and add these artificial zeolites to six containers filled with eutrophic seawater. On the other hand, 1.00%, 0.10%, and 0.01% were mixed. Each container was shaken for 24 hours, and then centrifuged to collect the supernatant, and the nitrogen and phosphorus equilibrium concentrations were measured to determine the nutrient adsorption capacity of the artificial zeolite. Here, the nitrogen concentration was measured by indophenol blue absorptiometry, and the phosphorus concentration was measured by molybdenum blue absorptiometry. The nutrient adsorption power was expressed as an adsorption removal rate (%) by dividing the nitrogen equilibrium concentration difference and phosphorus equilibrium concentration difference before and after the experiment by the nitrogen concentration and phosphorus concentration before the experiment, respectively.

  FIG. 10 shows the result of the Ca-type artificial zeolite, and FIG. 11 shows the result of the Fe-type artificial zeolite. From these results, both the Ca-type artificial zeolite and the Fe-type zeolite have a higher adsorption removal rate as the amount added to the seawater increases, and the zeolite has the ability to adsorb nutrients (nitrogen, phosphorus) in the seawater. I found out. From this, it is clear that when artificial zeolite (adsorption carrier) supporting hydroxy metal ions is mixed in aggregated soil, nutritional supplementation for aquatic plants becomes possible by adsorbing nutrients in water.

It is a mimetic diagram showing one embodiment of the bottom quality improvement construction method concerning the present invention. It is sectional drawing which shows typically the structure of the improvement apparatus used in embodiment shown in FIG. It is a schematic diagram which shows other embodiment of the bottom quality improvement construction method which concerns on this invention. It is a chart which shows the kind and mixture ratio of the raw material which were used in Example 1 of this invention. The structure of the long water channel used for the outflow experiment of the fine grain performed in Example 1 is shown, and is the schematic diagram (A) shown in a plane and the schematic diagram (B) shown in a side view. It is a graph which shows the experimental result of Example 1, and shows the particle size distribution before and after the experiment of aggregated soil. It is a graph which shows the experimental result of Example 1, and shows the particle size distribution before and after the experiment of non-aggregated soil. It is a graph which shows the experimental result of Example 2 and which shows the influence of the test soil which has on the growth number of a eel. It is the graph which showed the experimental result of Example 2, and shows the influence of the test soil on the maximum root length per eel. It is the graph which showed the experimental result of Example 3 and shows the influence of the addition amount of Ca type artificial zeolite which acts on a nutrient adsorption rate. It is the graph which showed the experimental result of Example 3 and shows the influence of the addition amount of the Fe type artificial zeolite which acts on a nutrient adsorption rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Work ship 2 Ladder 3 Improvement apparatus 5 Stirring blade 11 1st mixer (aggregating agent + adsorption carrier + water)
12 Second mixer (solidifying agent + water)
20 Backhoe for dredging 23 Screw type stirrer 25 Feeder for backfilling S Bottom mud (sediment sediment)

Claims (12)

  A soil for improving bottom sediments, characterized in that it is agglomerated by mixing an aggregating agent and a solidifying agent with earth and sand.   The aggregating agent is at least one selected from synthetic organic polymers such as sodium polyacrylate, carboxymethyl cellulose, polyacrylamide, and polyvinyl alcohol, polysaccharides such as sodium alginate and chitosan, and natural organic polymers. The soil for improving bottom sediment according to claim 1.   The aggregate for sediment improvement according to claim 1 or 2, wherein the solidifying agent is a chloride containing a polyvalent cation such as calcium chloride, magnesium chloride or iron chloride.   The sedimentary soil for improving sediment according to any one of claims 1 to 3, further comprising an adsorbent carrying a hydroxy metal ion.   The adsorption carrier is at least selected from artificial zeolite, natural zeolite, synthetic zeolite, diatomaceous earth, activated carbon, charcoal, silica gel, alumina gel, bentonite, kaolinite, allophane, imogolite, cation exchange resin, corrosive acid, peat. The aggregate soil for improving bottom sediment according to claim 4, which is one type.   The hydroxy metal ion is at least one selected from hydroxy iron ion, hydroxy copper ion, hydroxy zinc ion, hydroxy cobalt ion, hydroxy molybdenum ion, hydroxy calcium ion and hydroxy magnesium ion. Debris for improving sediment described.   A bottom quality improving construction method comprising laying the aggregated soil according to any one of claims 1 to 6 on a water bottom.   The bottom sediment improvement construction method according to claim 7, wherein the bottom mud in the improved zone is used as the soil for the aggregate soil, and the bottom mud is replaced with the aggregate soil.   The bottom quality improvement construction method according to claim 8, wherein the improvement device is lowered from the ship to the bottom of the water, and the bottom mud is aggregated in the improvement device.   The bottom sediment improvement method according to claim 8, wherein the bottom mud is dredged and fried on a ship, the bottom mud is agglomerated on the ship, and the obtained aggregated soil is backfilled to the bottom of the water.   The bottom ground improved in the bottom quality by the construction method of any one of Claims 7 thru | or 10. The water bottom ground according to claim 10, wherein seeds of seaweeds or diatoms are sown in aggregated soil.

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