JP6048088B2 - Amamo field construction method - Google Patents
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Description
本発明は、アマモ場を造成する方法に関する。 The present invention relates to a method for creating an ammo field.
海水中で生育する植物には、付着器によって岩礁帯に接着し、海水中に溶存した栄養塩類を摂取して生長する海藻類（コンブ、ノリ等）と、陸上植物と同様に種子によって増殖し、砂質又は砂泥質中に根を伸ばし、この根から栄養塩類を摂取して生長する海草類（アマモ等）がある。 Plants that grow in seawater are grown on seaweeds (comb, seaweed, etc.) that grow by ingesting nutrient salts dissolved in seawater, and seeds, as in land plants. There are seaweeds (such as sea cucumbers) that grow roots in sandy or sandy mud and grow nutrients from these roots.
海草類が群生する場所を主に海草藻場（アマモ場）と呼ぶが、このアマモ場は、多くの魚介類の産卵場、生育場であり、さらにアマモ表面に珪藻や動物プランクトンが付着することから、餌場にもなる。アマモ場によって形成される豊かな生態系は、水質浄化の役目も果たしている。 The place where seaweeds grow is called the seaweed algae field (Amamo field), which is a spawning ground for many seafood, and because diatoms and zooplankton adhere to the surface of the sea eels. It also becomes a feeding ground. The rich ecosystem formed by Amamo fields also plays a role in water purification.
しかし、近年、沿岸域の埋め立て工事、それによる海砂の流失、底質のヘドロ化等によって、アマモ場は激減しており、沿岸域の底質環境の改善によるアマモ場の復元が強く求められるようになった。
そして、これまでも、アマモ場の回復に向けて以下のような対策が提案され、実施されている。
In recent years, however, sea lions have drastically decreased due to land reclamation work in the coastal area, resulting in the loss of sea sand and sludge, etc., and there is a strong need for restoration of sea lions by improving the sediment environment in the coastal area. It became so.
So far, the following measures have been proposed and implemented for recovery of the eelgrass field.
１）アマモ苗の根を粘土で包み、直接海域底質に固定する方法（特許文献１）
２）人工栽培したアマモ苗を生分解性シートに移植し、海域底質に敷設する方法（特許文献２）
これらの方法１）及び２）は、アマモ苗を粘土や生分解性シートに固定させて移植するものであり、移植時の作業を簡便化するものではあるが、アマモ苗へのダメージが大きく、アマモ苗が根付くには容易ではなく、結果として、アマモ苗の根の伸長が遅くなり、海域底部付近の流速が速い場合等にはアマモが容易に流失することから、この移植後の苗の流失を予め考慮に入れた上でのアマモ場造成となってしまう。また、上記の方法は、汚濁の進んだ底質環境を改善するものではないのでアマモ場の復元は容易ではなく、ある程度環境が清浄化した場所に限定した適用となってしまう。さらに、上記の方法２）においては、アマモ種子の播種から移植まで一貫して同じ生分解性シートを用いているものの、移植可能になるまでの育成期間においては海水をかけ流しにする必要があり、設備投資が大きくなるほか、実施可能な箇所が限られてしまい、必ずしも簡便な方法であるとは言い難い。
1) A method of wrapping roots of sea cucumber seedlings with clay and fixing them directly to the sea sediment (Patent Document 1)
2) A method of transplanting artificially grown sea cucumber seedlings onto a biodegradable sheet and laying them on the sea bottom sediment (Patent Document 2)
These methods 1) and 2) are transplanted by fixing eel seedlings to clay or a biodegradable sheet, which simplifies the operation at the time of transplantation, but the damage to eel seedlings is large, It is not easy for root-growth seedlings to take root, and as a result, the root-growth of seagull seedlings slows down, and when the flow velocity near the bottom of the sea area is high, sea eels are easily washed away. It will be the Amamo field construction that takes into account the stake. Moreover, since the above method does not improve the polluted bottom sediment environment, the recovery of the eelgrass field is not easy, and the application is limited to a place where the environment has been cleaned to some extent. Furthermore, in the above method 2), although the same biodegradable sheet is used consistently from seeding of seedling to transplanting, it is necessary to pour seawater during the growing period until transplantation becomes possible. In addition to an increase in capital investment, the number of places that can be implemented is limited, and it is not necessarily a simple method.
上記のような方法１）及び２）に加えて、近年、海域の浚渫工事で発生する浚渫土砂を用いてアマモ場を復元する方法が提案されている。しかし、浚渫土砂は窒素、リン等のアマモの生長に必要な栄養源を多く含むものの、極めて粒度が小さく流失し易いため、そのままではアマモ場の基盤材として用いることが困難である。そこで、以下のような流出防止対策が考案されている。 In addition to the above methods 1) and 2), in recent years, a method for restoring the eelgrass field using dredged sand generated by dredging work in the sea has been proposed. However, although dredged soil contains many nutrients necessary for the growth of sea cucumbers such as nitrogen and phosphorus, it is extremely small in particle size and easily washed away, so that it is difficult to use as it is as a base material for the sea bream field. Therefore, the following spill prevention measures have been devised.
３）軽焼マグネシア系固化剤、セメント系固化剤を浚渫土に混合して、アマモを植え付ける方法（特許文献３）
４）高炉水砕スラグを浚渫土に混合して、アマモを植え付ける方法（特許文献４）
これらの方法３）及び４）は、流失し易い浚渫土に軽焼マグネシア系固化材、セメント系固化材、あるいは高炉水砕スラグを混合し、軟弱底質である浚渫土を改質してアマモ場の基盤材とするものであるが、浚渫土砂の改質指標が明確でなく、改質の程度とアマモの生長との関係も不明確であり、アマモ場の復元を期待できるものではない。それ故、これらの方法で永続的にかつ広範囲に安定してアマモ場を造成することは困難であり、また、高炉水砕スラグは天然砂よりも比重が重く、安定性に優れてはいるものの、潜在水硬性（アルカリ刺激でそれ自体が硬化する現象）があり、使用程度によっては底質の固化が過度に進行し、アマモの根の伸長を阻害することも懸念される。
3) A method of planting eelgrass by mixing light-burned magnesia-based solidifying agent and cement-based solidifying agent with clay (Patent Document 3)
4) Mixing blast furnace granulated slag with dredged soil and planting eelgrass (Patent Document 4)
In these methods 3) and 4), light-burned magnesia-based solidified material, cement-based solidified material, or granulated blast furnace slag is mixed with the easily-disappeared clay, and the soft soil, which is soft sediment, is reformed. Although it is used as a base material for the field, the improvement index of dredged soil is not clear, and the relationship between the degree of modification and the growth of the eel is unclear, and it cannot be expected that the eel field will be restored. Therefore, it is difficult to create an Amamo field permanently and over a wide range by these methods, and although granulated blast furnace slag has a higher specific gravity than natural sand and is excellent in stability. There is a latent hydraulic property (a phenomenon that cures itself by alkali stimulation), and depending on the degree of use, the solidification of the sediment may proceed excessively, and there is a concern that the root elongation of sea eels may be inhibited.
ところで、改質の程度を示す指標として「硬度」が挙げられており、この硬度を指標として用いる以下の方法が考案されている。
５）高炉水砕スラグと他の基盤用材料を混合して、山中式硬度計による硬度測定値が少なくとも一部において１０mm以上となるように人工水底基盤を作製する方法（特許文献５）
６）高炉水砕スラグと他の基盤用材料を混合して、山中式硬度計による硬度測定値が３〜２０mmとなるように人工水底基盤を作製する方法（特許文献６）
By the way, “hardness” is cited as an index indicating the degree of modification, and the following methods using this hardness as an index have been devised.
5) A method of producing an artificial submarine base by mixing blast furnace granulated slag and other base materials so that the hardness measured by a Yamanaka hardness tester is at least 10 mm or more (Patent Document 5)
6) A method of producing an artificial water bottom base by mixing blast furnace granulated slag and other base materials so that the hardness measured by a Yamanaka hardness meter is 3 to 20 mm (Patent Document 6)
これらの方法５）及び６）は、いずれも着底基盤の硬度を規定しているものの、施工完了から６カ月後の硬度を評価する必要があることから、着底基盤の施工とアマモ場の造成とを同時期に実行できず、たとえ同時期に実行したとしても、希望する硬度を得られる可能性が低く、アマモ場の復元までに長時間を要し、早急な対策を打てる方策とは言い難い。また、これらの方法では、固化状態が均一ではないため、必ずしもアマモやその他の底生生物に適した硬度が得られるとは限らない。高炉水砕スラグは、硫黄含有量が多く、水産用水基準からも海域底質に大量に用いるべきではなく、さらに、着生基盤から何らかの原因で高炉水砕スラグが露出した場合には、アルカリ成分が溶出して固化が異常に進行し、提案されている所望の均質な硬度を得ることが難しくなり、また、混合が不十分な場合には、その箇所での固化が異常に進み、生物の生息も困難になる。 Although these methods 5) and 6) both specify the hardness of the bottomed base, it is necessary to evaluate the hardness after six months from the completion of the construction. It is unlikely that the desired hardness can be obtained even if it is executed at the same time, and it takes a long time to restore the ammo field, and what can be done as soon as possible It's hard to say. Moreover, in these methods, since the solidified state is not uniform, it is not always possible to obtain hardness suitable for sea lions and other benthic organisms. Blast furnace granulated slag has a high sulfur content and should not be used in large quantities in marine sediments based on the marine water standards, and if blast furnace granulated slag is exposed for some reason from the settlement base, Elution and solidification progresses abnormally, making it difficult to obtain the desired uniform hardness, and when mixing is inadequate, solidification at that location progresses abnormally, It becomes difficult to live.
そこで、本発明者らは、これまでに提案・実施されてきたアマモ場の造成方法における種々の問題点を解決すべく鋭意検討した結果、意外なことには、浚渫土砂にカルシウムイオンを溶出する固化促進材、特に製鋼スラグを添加してアマモの生育に適すると共に流出防止を達成できる硬度の改質土を調製し、この改質土を用いることにより、アマモの種子の発芽を促進し、また、アマモ場を効果的に造成できることを見出し、本発明を完成した。 Therefore, the present inventors have intensively studied to solve various problems in the Amamo field construction methods that have been proposed and implemented so far, and surprisingly, calcium ions are eluted in dredged soil. A solidified accelerator , especially steelmaking slag, is added to prepare a modified soil with a hardness that is suitable for the growth of sea cucumber and can prevent outflow, and by using this modified soil, germination of sea eel seeds is promoted. The present inventors have found that an ammo field can be effectively created and completed the present invention.
従って、本発明の目的は、浚渫土砂を改質し、アマモの生育に適した硬度に制御することにより、アマモの発芽及び生育を促進し、これによってアマモ場を容易に造成し得るアマモ場の造成方法を提供することにある。 Therefore, the object of the present invention is to improve the dredged sand and control the hardness to be suitable for the growth of sea cucumber, thereby promoting the germination and growth of sea cucumber, thereby making it possible to easily create the sea eel field. It is to provide a creation method.
本発明の要旨とするところは、次の（１）〜（１５）の通りである。
（１）浚渫土砂と製鋼スラグとを混合して得られ、山中式硬度計で測定される硬度が、前記混合後３０日目で２０kPa以上５００kPa以下に達し、かつ、前記混合後３０日目以降も２０kPa以上５００kPa以下の範囲内である改質土を海底に敷設し、この改質土で海草類を育成することを特徴とするアマモ場の造成方法。
The gist of the present invention is as follows (1) to (15).
(1) obtained by mixing the dredged material and steel slag, hardness measured by Yamanaka-type hardness meter, the after mixing 30 days reached below 500kPa above 20 kPa, and the mixture after 30 days after A method for building an ammo field, comprising laying modified soil on the sea floor within a range of 20 kPa to 500 kPa and cultivating seaweeds with the modified soil.
（２） 前記改質土の硬度が、前記混合後３０日目で３０kPa以上に達し、かつ、前記混合後３０日目以降も３０kPa以上５００kPa以下の範囲内であることを特徴とする前記（１）に記載のアマモ場の造成方法。
（３）前記改質土中に予め海草類の種子を混合し、得られた種子入り改質土を海底に敷設することを特徴とする前記（１）又は（２）に記載のアマモ場の造成方法。
（４）海底に敷設された前記改質土に海草類の種子を播種し、育成することを特徴とする前記（１）又は（２）に記載のアマモ場の造成方法。
(2) The hardness of the modified soil reaches 30 kPa or more on the 30th day after the mixing, and is within the range of 30 kPa or more and 500 kPa or less after the 30th day after the mixing. ) Amamo field construction method described in .
(3) Creation of an ammo field as described in (1) or (2) above, wherein seaweed seeds are mixed in advance in the modified soil, and the obtained modified soil containing seeds is laid on the seabed. Method.
(4) The method for building an ammo field as described in (1) or (2) above, wherein seeds of seaweeds are sown and grown on the modified soil laid on the seabed.
（５）前記改質土を海水中分解可能な育成容器に入れてこの改質土に海草類の種子を播種し、種子が播種された改質土を育成容器と共に海底に敷設することを特徴とする前記（１）又は（２）に記載のアマモ場の造成方法。
（６）前記改質土を海水中分解可能な育成容器に入れてこの改質土に海草類の種子を播種し、育成して発芽した苗を前記改質土及び育成容器と共に海底に移植することを特徴とする前記（１）又は（２）に記載のアマモ場の造成方法。
(5) The modified soil is put in a growth vessel that can be decomposed in seawater, seeds of seaweeds are sown on the modified soil, and the modified soil on which the seeds are sown is laid on the seabed together with the growth vessel. The method for building an ammo field as described in (1) or (2) above.
(6) Putting the modified soil in a growth vessel that can be decomposed in seawater, sowing seeds of seaweeds on the modified soil, and transplanting the seedlings grown and germinated together with the modified soil and the growth vessel to the seabed. The method for building an ammo field as described in (1) or (2) above.
（７）前記海草類の種子が、改質土の表面から深さ１〜２cmまでの間に播種されることを特徴とする前記（４）〜（６）のいずれか１項に記載のアマモ場の造成方法。 (7) The seaweed field according to any one of (4) to (6) , wherein the seaweed seeds are sown from a surface of the modified soil to a depth of 1 to 2 cm. How to build.
（８）前記製鋼スラグの添加量が、前記改質土中３０質量%以下であることを特徴とする前記（１）〜（７）のいずれか１項に記載のアマモ場の造成方法。
（９）前記製鋼スラグは、０．０７５mm以下の粒径が１０質量%以下であって、２６．５mm以上の粒径が５質量%以下であることを特徴とする前記（１）〜（８）のいずれか１項に記載のアマモ場の造成方法。
(8) The amamo field creation method according to any one of (1) to (7) , wherein an amount of the steelmaking slag added is 30% by mass or less in the modified soil.
(9) the steelmaking slag is not more than the particle size of 10 wt% or less 0.075 mm, above, wherein the particle size of greater than or equal to 26.5mm is not more than 5 wt% (1) - (8 The construction method of the eelgrass field according to any one of (1) .
（１０）３０質量%の製鋼スラグを混合して得られる前記改質土の硬度が２０kPa未満の場合、前記改質土中に１質量%以下の高炉スラグを混合することを特徴とする前記（１）〜（９）のいずれか１項に記載のアマモ場の造成方法。
（１１）前記改質土中に、無機態栄養分として腐植土を混合することを特徴とする前記（１）〜（１０）のいずれか１項に記載のアマモ場の造成方法。
(10) said modified soil hardness that is obtained by mixing 30 mass% of steelmaking slag of less than 20 kPa, above, wherein the mixing 1 mass% of blast furnace slag to the reforming soil (1) The construction method of the eelgrass field given in any 1 paragraph of (9) .
(11) The method for building an ammo field according to any one of (1) to (10) , wherein humus soil is mixed as an inorganic nutrient in the modified soil.
（１２）前記海水中分解可能な育成容器が、生分解性プラスチック製であることを特徴とする前記（４）〜（１１）のいずれか１項に記載のアマモ場の造成方法。
（１３）前記海底が水深５m以上である場合、この海底に盛り土をして水深５m未満としてから前記改質土の敷設をして海草類を育成することを特徴とする前記（１）〜（１２）のいずれか１項に記載のアマモ場の造成方法。
(12) The method for building an ammo field according to any one of (4) to (11) , wherein the growth vessel capable of being decomposed in seawater is made of a biodegradable plastic.
(13) if the seabed is not less than 5m deep, the (1) to (12, characterized in that growing the seaweed and the laying of the reforming soil after less than 5m deep and the fill into the seabed eelgrass beds method Construction according to any one of).
（１４）前記盛り土が、３０質量%超の製鋼スラグを含むものであることを特徴とする前記（１３）に記載のアマモ場の造成方法。
（１５）前記盛り土が、浚渫土砂中に３０質量%超の製鋼スラグを混合して得られたものであることを特徴とする前記（１３）又は（１４）に記載のアマモ場の造成方法。
(14) The ammo field construction method according to (13) , wherein the embankment includes steelmaking slag of more than 30% by mass.
(15) The method for creating an ammo field according to (13) or (14), wherein the embankment is obtained by mixing steelmaking slag of more than 30% by mass in dredged sand.
本発明により、固化促進材を用いて軟弱土壌である浚渫土砂を改質し、アマモの生育に適した硬度に制御することによって、アマモ種子の発芽及び生長を促進し、さらに簡便にアマモ場を造成することが可能となる。 According to the present invention, the dredged sand, which is a soft soil, is modified by using a solidification promoting material and controlled to a hardness suitable for the growth of sea cucumber, thereby promoting the germination and growth of sea cucumber seeds, and more easily It can be created.
まず、本発明の海草藻場（アマモ場）の造成方法について説明する。
本発明が造成の対象とする海草藻場とは、水底の底質（天然の海草藻場であれば、砂質又は砂泥質）中に地下茎を張り巡らせ、そこから生育・繁殖するアマモ類（例えば、アマモ、コアマモ、オオアマモ、リュウキュウスガモ）等の海草類が群生している海底のことであり、一般にはアマモ場と呼ばれる。
First, the construction method of the seaweed algae field (Amamo field) of this invention is demonstrated.
The seagrass beds that are the subject of the present invention are the sea cucumbers that stretch the rhizomes in the bottom sediment (sandy or sandy mud in the case of natural seaweed algae beds) and grow and breed from there. This is the seabed where seaweeds such as sea cucumbers, core ducks, giant ducks, and Ryukyuus ducks are clustered and are generally called amamo fields.
このようなアマモ場を造成するために、本発明のアマモ場の造成方法では、浚渫土砂にカルシウムイオンを溶出する固化促進材を混合し、浚渫土砂の硬度をアマモ等の海草類の生育に適した範囲に調整し、海草類を育成するための改質土（基盤材）とする。この改質土によってアマモ種子の発芽、発芽体の生長を促進し、さらに海草類の地下茎又は根の安定性を増すことで、永続的なアマモ場の造成が可能となる。また、浚渫土砂の硬度を増大させることにより、浚渫土砂の流出を防止することが可能になる。 In order to create such an ammo field, in the amam field construction method of the present invention, a solidification promoter that elutes calcium ions is mixed with dredged sand, and the hardness of dredged sand is suitable for the growth of seaweeds such as amamo. Adjust to the range and use modified soil (base material) to grow seaweeds. This modified soil promotes the germination of eelgrass seeds and the growth of germination bodies, and further increases the stability of the rhizomes or roots of seaweeds, thereby making it possible to create a permanent eelgrass field. Further, by increasing the hardness of dredged sand, it is possible to prevent dredged sand from flowing out.
固化促進材としては、カルシウムイオンを溶出する材料を用いることが必要であり、これは、浚渫土砂から溶解性シリカが溶出するが、この浚渫土砂にカルシウムイオンが供給されると、浚渫土砂の粒子間にケイ酸カルシウム（ＣＳＨ）が生成し、固化が促進されるからである。このような固化促進材としては、水酸化カルシウム、酸化カルシウム、塩化カルシウム等も使用できるが、中でも、製鉄プロセスの副産物である製鋼スラグを用いることが最も望ましい。これは以下の理由による。 As the solidification promoter, it is necessary to use a material that elutes calcium ions. This is because soluble silica elutes from the dredged sand. When calcium ions are supplied to the dredged sand, This is because calcium silicate (CSH) is generated between them and solidification is promoted. As such a solidification promoting material, calcium hydroxide, calcium oxide, calcium chloride, and the like can be used. Among them, it is most desirable to use steel slag which is a byproduct of the iron making process. This is due to the following reason.
製鋼スラグは、製鉄系スラグの一つであり、安価で安定供給のできる資材である。また、主成分はカルシウムシリケート化合物であって、長期間に亘ってカルシウムイオンを供給することが可能である。また、比重も２．８〜３．０kg/Lと砂（2.3〜2.5kg/L）よりもかなり高く、浚渫土砂と混合することによって流失し難い安定した基盤材（改質土）となる。但し、製鋼スラグを過剰に添加し過ぎると周辺海水のｐＨ上昇が懸念されるため、最大添加量は５０質量%以下とすることが望ましい。混合する場合には、十分に混合し、それによって、酸性である浚渫土砂の間隙水が製鋼スラグのアルカリ分を中和し、極端なｐＨの上昇を抑えることができる。３０質量%を超える製鋼スラグの混合は、浚渫土砂の種類によっては間隙水のｐＨが過度に上昇する場合があり、アマモ等の海草類の生長を阻害する可能性がある。 Steelmaking slag is one of iron-making slags, and is a material that can be stably supplied at a low cost. The main component is a calcium silicate compound, which can supply calcium ions over a long period of time. Moreover, specific gravity is also 2.8-3.0 kg / L and is considerably higher than sand (2.3-2.5 kg / L), and it becomes a stable base material (modified soil) which is hard to be washed away by mixing with dredged soil. However, excessive addition of steelmaking slag may raise the pH of the surrounding seawater, so the maximum addition amount is desirably 50% by mass or less. In the case of mixing, the mixture is sufficiently mixed, whereby the acidic pore water of the clay soil can neutralize the alkali content of the steelmaking slag and suppress an extreme increase in pH. The mixing of steelmaking slag exceeding 30% by mass may excessively increase the pH of pore water depending on the type of dredged soil, which may inhibit the growth of seaweeds such as sea bream.
本発明で使用する製鋼スラグは、浚渫土砂を混合した改質土の硬度と相関性が確認されているＣaＯ、f-ＣaＯ、及びＳiＯ2の含有割合が、それぞれ２０〜６０質量%、０．２〜２０質量%、及び５〜２５質量%の範囲であるのが好ましい。また、粒径分布は、０．０７５mm以下の粒径が１０質量%以下、２６．５mm以上の粒径が５質量%以下であることが望ましい（JIS Z 8801に規定する網ふるいの呼び寸法で規定）。さらに、５０%粒径（粒子全体の５０%の粒径）が５mm以上１５mm以下であることが望ましい。０．０７５mm以下の粒径の製鋼スラグはf-ＣaＯの含有率が高く、また、表面積も大きくてｐＨが上昇し易いため、１０質量%以下とすることが望ましい。また、粒径が２６．５mm以上の製鋼スラグでは、逆にカルシウムイオンの溶出が抑制され、固化の進行が生じ難くなるため、５質量%以下とすることが望ましい。 The steelmaking slag used in the present invention has CaO, f-CaO, and SiO 2 content ratios of 20 to 60% by mass and 0.00%, respectively, which have been confirmed to correlate with the hardness of the modified soil mixed with dredged soil. The range of 2 to 20% by mass and 5 to 25% by mass is preferable. The particle size distribution is preferably 10% by mass or less for particles having a particle size of 0.075 mm or less, and 5% by mass or less for particles having a particle size of 26.5 mm or more (the nominal size of a screen sieve specified in JIS Z 8801). Regulations). Furthermore, it is desirable that the 50% particle size (50% of the total particle size) is 5 mm or more and 15 mm or less. Steelmaking slag having a particle size of 0.075 mm or less has a high content of f-CaO, and also has a large surface area, so that the pH tends to increase, so that it is desirable to make it 10% by mass or less. On the other hand, in the steelmaking slag having a particle size of 26.5 mm or more, the elution of calcium ions is suppressed on the contrary, and the progress of solidification hardly occurs.
さらに、本発明で使用する製鋼スラグは、５０%粒径が５〜１５mm程度の礫であるため、アマモ等の海草類は、根を礫に絡めながら伸長させることができるので、造成されたアマモ場においてその安定性が向上し、一般に生育困難であるとされている流速６０cm/sの海域でも流失することなく、アマモ場を造成することができる（アンカー効果）。なお、従来において、アマモ場の造成で推奨されている砂の５０%粒径は０．１４〜０．３９mmであり、上記のようなアンカー効果は期待することができない。また、本発明においては、施工時に、従来法（特許文献３）で使用が推奨されている草体安定工（例えば、エクスバンドメタル）を採用する必要がなく、より安価に、かつ、簡便にアマモ場を造成することが可能である。 Furthermore, since the steelmaking slag used in the present invention is a gravel with a 50% particle size of about 5 to 15 mm, seaweeds such as sea eels can be stretched while the roots are entangled with the gravel. The stability of the sea bream is improved, and an ammo field can be created without being lost even in a sea area with a flow velocity of 60 cm / s, which is generally considered difficult to grow (anchor effect). In addition, conventionally, the 50% particle size of sand recommended for the construction of an ammo field is 0.14 to 0.39 mm, and the anchor effect as described above cannot be expected. Further, in the present invention, it is not necessary to adopt a grass stabilizer (for example, an ex-band metal) recommended for use in the conventional method (Patent Document 3) at the time of construction, and it is cheaper and simpler. It is possible to create a place.
浚渫土砂に製鋼スラグを所定量混合しても硬度２０kPa以上の改質土が得られない場合には、さらに固化を促進させるために、高炉水砕スラグの微粉を製鋼スラグと共に加えてもよい。しかし、高炉水砕スラグの微粉はそれ自体が潜在水硬性（アルカリ刺激で硬化する現象）を有しているため、過剰に加えると、得られた改質土（スラグ混合土）の硬度が５００kPa以上になり、アマモ種子の発芽及び苗の生育を阻害する場合がある。そこで、改質土の硬度を５００kPa以下とするためには、高炉水砕スラグ微粉の添加については、比重２．８９及びブレーン値３０００〜５０００cm2/gで規定されるものを用いて、その添加量も１質量%以下とすることが望ましい。 If a modified soil with a hardness of 20 kPa or more cannot be obtained even when a predetermined amount of steelmaking slag is mixed with dredged soil, fine powder of blast furnace granulated slag may be added together with the steelmaking slag in order to further promote solidification. However, since the ground granulated blast furnace slag itself has latent hydraulic properties (a phenomenon that hardens by alkali stimulation), when added excessively, the hardness of the resulting modified soil (slag mixed soil) becomes 500 kPa. Thus, the germination of seedlings and the growth of seedlings may be inhibited. Therefore, in order to set the hardness of the modified soil to 500 kPa or less, the blast furnace granulated slag fine powder is added with a specific gravity of 2.89 and a brane value of 3000 to 5000 cm 2 / g. The amount is desirably 1% by mass or less.
ところで、アマモ等の海草類の生息できる基盤材（改質土）の理想的な環境としては、これまで、海底流速、底質砂面の変化量、そして底質の移動状況を示すシールズ数を指標として定義されてきた（非特許文献１）。特に、底質砂面の変化量の計測には１週間から１ヶ月を要し、アマモ場造成の候補地としての迅速な判断をすることが困難であった。また、これまでは、基盤材の硬度は、アマモ場の環境指標としては無視されてきた。これは硬度の増大は、アマモの生育にマイナスの効果しかないとして認識されてきたためである。しかし、発明者らは、本発明において、硬度の増加は必ずしもマイナスの効果ばかりではなく、アマモの生育に適した基盤材の硬度が存在することを初めて見出したのである。ここで述べる土壌の硬度は「山中式土壌硬度計」を用いて測定した圧入抵抗値である。山中式土壌硬度計を用いることによって、簡便、かつ短時間にアマモ場造成地としての適性を判断することができる。さらに、該硬度計は、測定者による誤差も生じ難く、安価に入手できる。 By the way, as an ideal environment for the base material (modified soil) in which seagrasses such as sea eels can inhabit, the seabed flow velocity, the amount of change in the bottom sand surface, and the number of shields indicating the state of movement of the bottom sediment have been indexed so far. (Non-patent Document 1). In particular, it took 1 week to 1 month to measure the amount of change in the sediment sand surface, and it was difficult to make a quick judgment as a candidate site for the Amamo field. In the past, the hardness of the base material has been ignored as an environmental indicator for the Amamo field. This is because an increase in hardness has been recognized as having only a negative effect on the growth of sea cucumber. However, the inventors found for the first time in the present invention that the increase in hardness is not necessarily a negative effect, but that there is a hardness of the base material suitable for the growth of sea cucumber. The soil hardness described here is a press-fit resistance value measured using a “Yamanaka soil hardness meter”. By using a Yamanaka type soil hardness meter, it is possible to judge suitability as an amamo field construction site in a simple and short time. Furthermore, the hardness meter is less prone to error by the measurer and can be obtained at a low cost.
製鋼スラグによる浚渫土砂の改質、つまり固化の促進は、製鋼スラグの混合割合によって調節することができる。通常、固化の進行は、混合直後から開始するが、材齢３０日で飽和となるため、３０日以降の硬度（山中式硬度計で測定した圧入抵抗値）が２０kPa以上５００kPa以下、好ましくは３０kPa以上４００kPa以下になるように、浚渫土砂に製鋼スラグを混合するのがよい。硬度が２０kPa未満では海流による流出を抑制することが困難であり、反対に、硬度が５００kPa超ではアマモの発芽に影響が出る。できれば、敷設する前に、少量の製鋼スラグ及び浚渫土砂でテストピースを作製し、３０日目の硬度が２０kPa以上５００kPa以下となる配合割合を特定しておくのがよい。以上のように、本発明によって、改質土の硬度を短期間で簡便に評価できるため、より迅速にアマモ場の造成を実現することができる。 The modification of dredged soil by steelmaking slag, that is, the promotion of solidification, can be adjusted by the mixing ratio of steelmaking slag. Normally, the solidification starts immediately after mixing, but becomes saturated at the age of 30 days, so the hardness after 30 days (press-fit resistance value measured with a Yamanaka hardness meter) is 20 kPa to 500 kPa, preferably 30 kPa. Steelmaking slag is preferably mixed with dredged soil so as to be 400 kPa or less. If the hardness is less than 20 kPa, it is difficult to suppress the outflow due to ocean currents. Conversely, if the hardness exceeds 500 kPa, it will affect the germination of sea bream. If possible, it is better to prepare a test piece with a small amount of steelmaking slag and dredged sand before laying, and specify the blending ratio at which the hardness on the 30th day is 20 kPa to 500 kPa. As described above, according to the present invention, the hardness of the modified soil can be easily evaluated in a short period of time, so that it is possible to more quickly create an ammo field.
本発明の改質土を海底に敷設し、この改質土で海草類を育成してアマモ場を造成するに際し、より具体的には以下の第１〜第４の方法が採用される。
すなわち、第１の方法は、前記改質土中に予め海草類の種子を混合し、得られた種子入り改質土を海底に敷設する方法である。この第１の方法において、浚渫土砂に製鋼スラグ及びアマモ等の海草類の種子を混合した改質土から、海草類の種子が流失せず、かつ、効率よく発芽できるように、好ましくは敷設する改質土の厚みを３〜５cmとするのが望ましい。アマモ等の海草類の種子は、表面から数cmの深さであれば容易に発芽することができる。また、発芽後、深さ５cm程度で２次元的に地下茎を伸長させ、分枝しながら、個体数を増やしていくため、海草類の種子を混合させた改質土を３〜５cmの厚みで敷設することによって、効率的にアマモ等の海草類の発芽及び生長促進を促すことができる。また、５cmよりも厚く敷設すると、５cmより深い場所に存在する種子は発芽し難くなり易く、アマモ場の造成効率が低下する可能性がある。
When the modified soil of the present invention is laid on the seabed and seaweeds are grown on the modified soil to create an ammo field, the following first to fourth methods are more specifically adopted.
That is, the first method is a method of previously mixing seaweed seeds in the modified soil and laying the obtained modified soil containing seeds on the seabed. In this first method, a modified soil preferably laid so that seeds of seaweeds are not washed away and can be efficiently germinated from modified soil obtained by mixing steelmaking slag and seaweed seeds such as sea bream into dredged soil. The thickness of the soil is preferably 3 to 5 cm. Seeds of seaweeds such as sea cucumber can germinate easily at a depth of several centimeters from the surface. In addition, after germination, a modified soil mixed with seaweed seeds is laid in a thickness of 3 to 5 cm in order to increase the number of individuals by extending the rhizomes two-dimensionally at a depth of about 5 cm and branching. By doing so, germination and growth promotion of seaweeds such as sea bream can be promoted efficiently. In addition, when laying thicker than 5 cm, seeds existing in a place deeper than 5 cm are difficult to germinate, and there is a possibility that the formation efficiency of the eelgrass field is reduced.
また、第２の方法は、海底に敷設された前記改質土に海草類の種子を播種して育成する方法であり、また、第３の方法は、前記改質土を海水中分解可能な育成容器に入れてこの改質土に海草類の種子を播種し、種子が播種された改質土を育成容器と共に海底に敷設する方法であり、更に、第４の方法、前記改質土を海水中分解可能な育成容器に入れてこの改質土に海草類の種子を播種し、育成して発芽した苗を前記改質土及び育成容器と共に海底に移植する方法である。そして、これら第２〜４の方法において、前記改質土に海草類の種子を播種する際の播種深さについては、改質土の表面から１〜２cmであるのがよく、これより深いと発芽率が低下し、また、これより浅いと発芽しても改質土から脱落する虞がある。 The second method is a method for growing seeds of seaweeds on the modified soil laid on the seabed, and the third method is a method for growing the modified soil in seawater. It is a method of placing seeds of seaweeds in this modified soil in a container, and laying the modified soil on which the seeds are sown together with a growing container on the sea floor, and a fourth method, wherein the modified soil is submerged in seawater This is a method in which seeds of seaweeds are sown in this modified soil in a degradable growing container, and the seedlings that have been grown and germinated are transplanted to the seabed together with the modified soil and the growing container. In these second to fourth methods, the seeding depth when seeding seaweed seeds on the modified soil is preferably 1 to 2 cm from the surface of the modified soil. The rate decreases, and if it is shallower than this, even if it germinates, it may fall off from the modified soil.
更に、本発明において、改質土の敷設予定地が、アマモ等の海草類の生育に適さない水深５m以上である場合、盛り土をして生育に適した水深に調整することも可能である。この場合、盛り土の種類には特に制限はないが、製鋼スラグを３０質量%超で含んで固化が促進された盛り土であることが好ましく、特に製鋼スラグを３０質量%超で含む浚渫土砂が好ましい。また、底質が極めて軟弱である場合には、浚渫土砂に製鋼スラグを３０質量%以上混合し、強固に固化させた盛り土でマウンドを作製し、その上にアマモ種子を混合した改質土（製鋼スラグ３０質量%以下混合）を敷設すればよい。なお、製鋼スラグを多量に混合した盛り土は、周辺海水のｐＨを上昇させ易くなるが、その上に本発明の改質土を被覆することにより周辺海水との間が遮蔽され、ｐＨの上昇を抑制することができる。
Furthermore, in the present invention, when the planned site of the modified soil is a depth of 5 m or more that is not suitable for the growth of seaweeds such as sea cucumbers, it is possible to adjust the depth to be suitable for growth by embankment. In this case, there is no particular limitation on the type of embankment, but it is preferably an embankment that contains steelmaking slag at more than 30% by mass and solidification is promoted, and in particular, dredged sand that contains steelmaking slag at more than 30% by mass is preferred. . In addition, when the sediment is extremely soft, a modified soil (mixed steel sand slag is mixed with 30% by mass or more of dredged soil, a mound is produced with a solidified solid embankment, and amamo seeds are mixed on the mound. What is necessary is just to lay
さらに、浚渫土砂と製鋼スラグを混合し固化が進行した改質土は、これまで広く用いられてきた山砂と腐植土の混合土よりも栄養塩を豊富に含むため、アマモ等の海草類の種子の発芽及び苗の生長をより促進することができる。すなわち、表１に示すように、浚渫土砂の間隙水には無機態の窒素及びリンが多量に含まれており、これらを摂取したアマモ等の海草類の種子は、その発芽及び生長が促されるものと考えられる。なお、本発明者らは、これら栄養塩の供給が改質土の固化によって阻害されないことを確認している。 In addition, the modified soil, which has been solidified by mixing dredged soil and steelmaking slag, contains abundant nutrients compared to the mixed soil of mountain sand and humus soil that has been widely used so far, so seaweed seeds such as sea eels Germination and seedling growth can be further promoted. In other words, as shown in Table 1, the pore water of dredged soil contains a large amount of inorganic nitrogen and phosphorus, and seeds of seaweeds such as sea cucumber that ingested them are encouraged to germinate and grow. it is conceivable that. In addition, the present inventors have confirmed that the supply of these nutrient salts is not hindered by the solidification of the modified soil.
なお、浚渫土砂が汚濁の進んでいない海域のもので砂分が多い場合等、浚渫土砂の間隙水中の窒素、リン等が少ない場合も想定される。このような浚渫土砂を用いる場合には、浚渫土砂及び製鋼スラグの他に、腐植土等を加えてもよい。このような腐植土の添加量は、間隙水中の窒素、リン等の濃度が水産用水基準で示されたノリの養殖の海水基準値（窒素：0.1mg/L、リン：0.014mg/L）の１０倍濃度以上（希釈を考慮）、即ち、窒素濃度が１mg/L以上、リン濃度が０．１４mg/L以上となるように添加すればよい。 It is also assumed that dredged soil has less nitrogen, phosphorus, etc. in the pore water of the dredged soil, such as when the dredged soil is from a marine area that is not polluted and has a large amount of sand. When such dredged soil is used, humus or the like may be added in addition to dredged soil and steelmaking slag. The amount of humus soil added is that of the seawater standard values (nitrogen: 0.1 mg / L, phosphorus: 0.014 mg / L) of seaweed culture in which the concentration of nitrogen, phosphorus, etc. in the pore water is indicated by the aquaculture water standard. The concentration may be 10 times or more (considering dilution), that is, the nitrogen concentration may be 1 mg / L or more and the phosphorus concentration may be 0.14 mg / L or more.
アマモ等の海草類の苗を陸上において育苗する場合、本発明で確立した浚渫土砂の改質によって、アマモ等の海草類の苗の生長を促進することができる。上記方法によって作製した浚渫土砂及び製鋼スラグを含む改質土を育成容器（例えば、バットやカップ等）中に通常３cm以上１５cm以下、好ましくは６cm以上１０cm以下の厚さで敷設し、そこにアマモ種子を表面から１〜２cm程度の深さに播種する。播種した育成容器は、遮光をして、できるだけ１５℃以下になるように静置する。種子の発芽を確認した後、育成容器を明条件に移し、苗の生長を促す。種子の播種の際、改質土（スラグ混合土）を予めプラスチック製のカップや生分解性プラスチック製カップや薄鉄板製カップ等の海水中分解可能なカップ等に入れて、苗を育苗してもよい。それによって、苗をアマモ場造成海域に移植する際に、海中でカップを外してから、もしくはカップを付けたままで、容易に移植することができるため、簡便にかつアマモ苗にダメージを与えることなく移植でき、効率的にアマモ場の造成を進めることができる。 When seaweed seedlings such as sea cucumbers are grown on land, the growth of seaweed seedlings such as sea eels can be promoted by the modification of dredged soil established in the present invention. The modified soil containing dredged sand and steelmaking slag produced by the above method is laid in a growth container (for example, a bat or a cup) in a thickness of usually 3 cm or more and 15 cm or less, preferably 6 cm or more and 10 cm or less. Seeds are sown to a depth of about 1 to 2 cm from the surface. The seeded growth container is shielded from light and allowed to stand at 15 ° C. or less as much as possible. After confirming the germination of the seeds, the growth container is moved to light conditions to promote seedling growth. When seeding, seedlings are grown by placing the modified soil (slag mixed soil) in a plastic cup, a biodegradable plastic cup, a thin iron plate cup, etc. that can be decomposed in seawater. Also good. As a result, when transplanting seedlings into the sea eel formation sea area, it can be easily transplanted after removing the cup in the sea or with the cup attached, so it is easy and without damaging the sea eel seedlings It can be transplanted, and the construction of the eelgrass field can be promoted efficiently.
実海域におけるアマモ等の海草類の種子の発芽率は、通常１０%未満とされており、また、天然アマモ場の密生域では、生育密度が３０株／m2程度である。したがって、アマモ場造成時の播種密度は、３００〜１０００粒／m2であることが好ましい。 The germination rate of seagrass seeds such as sea cucumbers in the actual sea area is usually less than 10%, and the growth density is about 30 strains / m 2 in the dense area of the natural sea eel field. Therefore, it is preferable that the seeding density at the time of the Amamo field construction is 300 to 1000 grains / m 2 .
以下、実施例に基づいて、本発明をより具体的に説明する。
〔実施例１：アマモ種子の発芽に適した硬度の特定〕
浚渫土砂への製鋼スラグの混合率（スラグ混合率）を変化させて４種類の改質土を作製し、アマモ種子の発芽率を比較することによって、アマモ種子の発芽に適した硬度の特定を行った。
Hereinafter, based on an Example, this invention is demonstrated more concretely.
[Example 1: Identification of hardness suitable for germination of sea cucumber seeds]
By changing the mixing ratio of steelmaking slag to dredged soil (slag mixing ratio), four types of modified soil were prepared, and the germination rate of eelgrass seeds was compared to identify the hardness suitable for the germination of eelgrass seeds. went.
東京湾で採取した浚渫土砂に製鋼スラグをスラグ混合率０質量%(0vol%)、１０質量%(6.3vol%)、２０質量%(13.1vol%)、３０質量%(20.6vol%)、及び５０質量% (37.7vol%)の割合で混合し、各々４００mLの改質土からなる試験土壌を作製した。また、コントロールとして、通常、アマモ種子の発芽に用いる山砂及び腐植物質を体積比７：３で混合した試験土壌４００mLを用いた。
Steelmaking slag is mixed with dredged sand collected in Tokyo Bay.
各試験土壌の中に、冷暗環境下で保管されたアマモ種子を９００粒／m2となるように５０個ずつ混合し、得られた種子入りの試験土壌を厚さ４cm程度となるようにバット上に広げた。次に、このようにして調製したアマモ種子入りの各試験土壌が敷設された各バットを、バケツに入れた東京湾の実海水中に沈め、遮光した後に１５℃に設定した人工気象室に移し、種子の発芽を促した。定期的に発芽した個体数を計測し、実験区での発芽率を算出した。結果を表２に示す。 In each test soil, 50 eel seeds stored in a cool and dark environment were mixed at a rate of 900 grains / m 2, and the obtained test soil containing seeds was batted to a thickness of about 4 cm. Spread over. Next, each vat laid with each test soil containing eel seeds prepared in this way was submerged in the actual sea water of Tokyo Bay in a bucket, and after being shielded from light, moved to an artificial weather chamber set at 15 ° C. , Encouraged seed germination. The number of individuals that regularly germinated was counted, and the germination rate in the experimental plot was calculated. The results are shown in Table 2.
（１）発芽率の比較（図１）
図１に示すように、敷設から８日目で最初の発芽を確認した。その後、発芽個体数は徐々に増加していった。コントロールの試験土壌（腐植土＋山砂）では、４２日目に発芽率が２４%となり、その後変化が見られなかった。実験系では、製鋼スラグを含まないスラグ混合率０質量%（浚渫土砂のみ）の試験土壌、及びスラグ混合率５０質量%の試験土壌において、コントロールよりも低く、５７日目で１２．５%となった。また、スラグ混合率１０〜３０質量%の各試験土壌では、ほぼ同率でコントロールよりも顕著に高くなり、スラグ混合率２０質量%の試験土壌において５７日目で３８%に達した。５７日目の発芽率を比較すると以下のようになった。
１０〜３０質量%＞コントロール（腐植土＋山砂）＞浚渫土砂、５０質量%
(1) Comparison of germination rate (Fig. 1)
As shown in FIG. 1, the first germination was confirmed on the 8th day after laying. Thereafter, the number of germinated individuals gradually increased. In the control test soil (humus soil + mountain sand), the germination rate was 24% on the 42nd day, and no change was observed thereafter. In the experimental system, the test soil with a slag mixing ratio of 0% by mass (only dredged soil) without steelmaking slag and the test soil with a slag mixing ratio of 50% by mass are lower than the control and 12.5% on the 57th day. became. In addition, in each test soil having a slag mixing ratio of 10 to 30% by mass, the ratio was substantially the same and significantly higher than that of the control, and reached 38% on the 57th day in the test soil having a slag mixing ratio of 20% by mass. The germination rate on day 57 was compared as follows.
10-30% by mass> control (humus soil + mountain sand)> soil soil, 50% by mass
アマモ種子の発芽には、根の伸長が伴う。そのため、浚渫土砂に製鋼スラグを混合した改質土（スラグ混合土）からなる試験土壌のように、硬度が上昇したとしても、底質中に礫があることで、根が絡まり易く、安定し易い。このことが、浚渫土砂単体（スラグ混合率０質量%の試験土壌）よりも硬度が高い改質土で発芽率が上回ったものと考えられる。しかし、スラグ混合率５０質量%の試験土壌において発芽率が低下したことから、アマモ種子の発芽に適した硬度があることが推察された。 Germination of eelgrass is accompanied by root elongation. Therefore, even if the hardness increases, as in the test soil consisting of modified soil (slag mixed soil) in which steelmaking slag is mixed with dredged soil sand, the roots tend to be entangled and stable due to the presence of gravel in the bottom sediment. easy. This is considered to be that the germination rate was higher in the modified soil having higher hardness than the dredged soil alone (test soil with a slag mixing rate of 0 mass%). However, since the germination rate decreased in the test soil having a slag mixing rate of 50% by mass, it was presumed that there was a hardness suitable for the germination of sea cucumber seeds.
（２）硬度の比較（図２）
上で作製した各試験土壌の硬度を、山中式硬度計を用いて計測した。硬度は、各試験土壌毎に３地点計測し、その平均値を求めた。
コントロールの試験土壌（腐植土＋山砂）では、３０日目には、１７kPaと約２０kPaになった。その後もそのままで推移し、飽和硬度は２０kPaと推定された。
(2) Comparison of hardness (Fig. 2)
The hardness of each test soil prepared above was measured using a Yamanaka hardness tester. The hardness was measured at three points for each test soil, and the average value was obtained.
In the control test soil (humus soil + mountain sand), it became 17 kPa and about 20 kPa on the 30th day. Thereafter, the temperature remained unchanged, and the saturation hardness was estimated to be 20 kPa.
また、浚渫土砂単体（スラグ混合率０質量%）の試験土壌では、硬度を発現することなく、０kPaのままであった。
スラグ混合率１０及び２０質量%の試験土壌では、コントロールよりも若干硬く、それぞれ３２kPa、３８kPaであった。その後もゆるやかに上昇し、飽和硬度は４０kPa程度と推定された。
In addition, the test soil of dredged soil alone (
The test soils with a slag mixing ratio of 10 and 20% by mass were slightly harder than the control and were 32 kPa and 38 kPa, respectively. After that, it gradually increased and the saturation hardness was estimated to be about 40 kPa.
スラグ混合率３０質量%の試験土壌では、１４日目に３１８kPaとなり、３０日目には４５８kPaとなり、飽和硬度は５００kPaと推定された。
スラグ混合率５０質量%の試験土壌では、さらに硬度が増し、３０日目に９８１kPaに達し、５７日目には１１５５kPaとなり、飽和硬度は、約１０００kPaと推定された。
In the test soil having a slag mixing ratio of 30% by mass, it was 318 kPa on the 14th day, 458 kPa on the 30th day, and the saturation hardness was estimated to be 500 kPa.
In the test soil having a slag mixing ratio of 50% by mass, the hardness further increased and reached 981 kPa on the 30th day, 1155 kPa on the 57th day, and the saturated hardness was estimated to be about 1000 kPa.
（３）硬度と発芽率の関係（図３）
上記の各試験土壌（改質土）におけるスラグ混合率に対する発芽率及び硬度変化の関係を図３に示す。
この図３から理解されるように、改質土の硬度が３０〜５００kPaの間で発芽率が高く、コントロール（硬度１７kPa）よりも上回った。しかし、この範囲以外にある場合、０kPa、及び１０００kPaでは、発芽率がコントロールよりも下回り、アマモ種子の発芽に適さないことが判明した。
(3) Relationship between hardness and germination rate (Figure 3)
FIG. 3 shows the relationship between the germination rate and the hardness change with respect to the slag mixing rate in each of the test soils (modified soils).
As understood from FIG. 3, the germination rate was high when the hardness of the modified soil was between 30 and 500 kPa, which was higher than the control (hardness of 17 kPa). However, when it was outside this range, it was found that at 0 kPa and 1000 kPa, the germination rate was lower than the control, and it was not suitable for germination of eelgrass seeds.
〔実施例２：実海域での試験〕
東京湾で採取した浚渫土砂に製鋼スラグを４０質量%の割合で混合し、改質土を調製した。この改質土を用いて東京湾沿岸の水深１０mの実海域に水深が４mになるように盛り土を行った。この盛り土の上に、表２に示した各試験土壌〔コントロール（山砂：腐植物質＝７：３）、スラグ混合率０質量%、１０質量%、２０質量%、３０質量%、５０質量%）の改質土〕を用い、厚さ５cmのマウンド（５m×５m）を作成した。
[Example 2: Test in actual sea area]
Steelmaking slag was mixed at a ratio of 40% by mass with dredged soil collected in Tokyo Bay to prepare modified soil. Using this modified soil, embankment was carried out in a real sea area of 10m depth along the Tokyo Bay coast so that the water depth would be 4m. On this embankment, each test soil shown in Table 2 [control (mountain sand: humic substance = 7: 3),
また、各マウンドと同様の試験土壌を生分解性プラスチックカップに入れて播種し、発芽させたアマモ苗（アマモ種子発芽体）を各マウンドに５０株／m2となるように植え付けた。移植から約２カ月後の５７日目にアマモ苗の各種部位を計測し、比較した。
結果を図４に示す。
Moreover, the test soil similar to each mound was put in a biodegradable plastic cup and sown, and the sprouting seedlings (seedling seedlings) were planted on each mound at 50 strains / m 2 . On the 57th day after about 2 months from the transplantation, various parts of the eelgrass seedlings were measured and compared.
The results are shown in FIG.
コントロールでは、４割の苗が脱落していたのに対し、スラグ混合率０質量%、１０質量%、２０質量%、３０質量%の各マウンドでは、アマモ苗の脱落は殆どなく、脱落個体は２割に止まっていた。また、スラグ混合率５０質量%のマウンドでは、７割が枯死していた。
また、マウンド付近のｐＨは、全条件で８．２前後となり、製鋼スラグを混合したことによるｐＨの上昇は全く認められなかった。
In the control, 40% of the seedlings had fallen, but in each mound with a slag mixing rate of 0%, 10%, 20%, and 30%, almost no eel seedlings dropped out. It stopped at 20%. In addition, 70% of the mound with a slag mixing ratio of 50% by mass was dead.
Further, the pH in the vicinity of the mound was about 8.2 under all conditions, and no increase in pH was observed due to the mixing of the steelmaking slag.
計測項目である葉幅、葉数、草丈、葉身全てにおいて、スラグ混合率０〜２０質量%の各マウンドは、コントロールを上回っており、スラグ混合土３０質量%のマウンドはコントロールとほぼ同程度という傾向が見られた。スラグ混合率５０質量%のマウンドでは、移植後殆ど生長が認められず、全ての計測項目でコントロールを下回った。スラグ混合率０〜３０質量%の各マウンドでコントロール以上もしくは同様にアマモ苗が生長したことから、浚渫土砂からの栄養塩類の溶出がアマモの生長に大きく影響していることが判明した。 For all measurement items, leaf width, number of leaves, plant height, and blade, each mound with a slag mixing ratio of 0-20% by mass exceeds the control, and the mound with 30% by mass slag mixed soil is almost the same as the control. The tendency was seen. In the mound with a slag mixing ratio of 50% by mass, almost no growth was observed after transplantation, and all the measurement items were below the control. It was clarified that elution of nutritive salts from dredged soil greatly affected the growth of sea cucumber, since the sea eel seedlings grew more than control or similarly in each mound having a slag mixing ratio of 0 to 30% by mass.
さらに、５７日目の各マウンドの硬度は、表３のようになり、実施例１の実験室内における検討と同様であった。これらの結果とアマモ種子の発芽率を考慮すると、アマモに適した硬度は２０〜５００kPaであり、製鋼スラグの混合率は１０〜３０質量%であることが判明した。
なお、スラグ混合率０質量%（浚渫土単独）のマウンドでは、アマモ苗の生長は良好であったが、マウンドの一部が流失しており、長期的には、盤石なアマモ場造成は困難であると判断した。
Further, the hardness of each mound on the 57th day was as shown in Table 3, which was the same as the examination in the laboratory of Example 1. Considering these results and the germination rate of eelgrass seeds, it was found that the hardness suitable for eelgrass is 20 to 500 kPa and the mixing rate of steelmaking slag is 10 to 30% by mass.
In addition, in the mound with a slag mixing ratio of 0% by mass (only dredged soil), the growth of eelgrass seedlings was good, but some of the mounds were washed away, and in the long term it would be difficult to create a rocky eel It was judged that.
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