JP3729160B2 - Environmental improvement method and environmental improvement materials for underwater or beach - Google Patents

Description

【００２０】
また、細粒分を多く含んだ高炉水砕スラグを水中や水浜に敷設すると、敷設層中で細粒部分が次第に偏在し、この偏在した細粒部分が固結してしまうことがあるが、上述したような比較的粗い粒度構成とすることにより、そのような細粒部分の固結も生じることはない。
以上の理由から、本発明法では、粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上、好ましくは粒径１．０ｍｍ以上のスラグ粒子の割合が７０mass％以上である高炉水砕スラグを水底又は水浜に敷設するものである。また、表１の結果等からして、高炉水砕スラグのより好ましい粒度構成は粒径１．０ｍｍ以上のスラグ粒子の割合が８０mass％以上である。
このような粒度構成の高炉水砕スラグを得るために、通常、高炉水砕スラグの篩い分けを行う。篩い分け法は、乾式篩い、湿式篩い、気流分離などのいずれでもよい。
【００２１】
以下、本発明法の基本的な実施形態について説明する。
（Ａ）青潮発生防止等を目的とする高炉水砕スラグの敷設（覆砂）
内湾等において水底で海水の停滞が生じると硫化水素が発生し、所謂青潮の発生原因となる。
硫化水素の主要な発生源は、水が停滞しやすく且つ有機物が堆積し、酸素消費量が多いヘドロ状の水底部であり、特に土砂採取等によって水底が部分的に掘られ、比較的深さのある凹部が形成された水底部において硫化水素が発生しやすい。すなわち、このような凹部内では水が停滞する結果、特に夏期において著しい無酸素状態となり、有機物の腐敗やバクテリア（硫酸還元菌）の作用によって大量の硫化水素が発生し、硫化水素を含んだ大量の無酸素水塊が生じる。このように凹部内で硫化水素が大量発生すると、凹部内やその周囲の棲息生物が減少するだけでなく、硫化水素を含んだ上記水塊が周辺水域に流出し、所謂青潮の発生に至る。また、凹部以外の水底部であっても、水が停滞しやすく且つ有機物が堆積して酸素消費量が多いヘドロ状の水底部では、同様に硫化水素が発生して硫化水素を含んだ無酸素水塊が生じ、底棲生物のへい死を招いたり、無酸素水塊が周辺水域に流出して青潮を発生させたりする。
【００２２】
従来、このような問題に対しては、水底（特に水底の凹部）に石灰を散布したり、水底を天然砂（海砂、山砂）を用いて覆砂する、などの対策が採られているが、先に述べたように天然砂や天然石は特に化学的な底質・水質浄化作用を有していないため、これらを水底に敷設した場合、例えば、夏期の海水停滞期や生物の活動が活発な時期になると、ヘドロが堆積していない状態でも間隙水中において硫酸還元菌の作用により数ｐｐｍ程度の硫化水素が生成してしまう。
【００２３】
一方、水底に石灰を散布する方法には、▲１▼多大なコストかかる、▲２▼ｐＨの制御が困難で水質が高アルカリになる場合がある、▲３▼石灰が水底で板状に固まってしまうため、その下部の泥質中の水が入れ替らず、このため硫化水素がより多量に発生し、ある時期に板状に固った石灰層が崩壊すると高濃度の硫化水素を含む水が周囲に流れ出てしまう、等の問題がある。また、石灰を散布するとしても石灰によって凹部を埋めてしまうことは困難であるため、結果的に凹部はそのまま残ることになり、したがって、凹部内の水が夏期の海水停滞期に無酸素化し、硫化水素が大量発生するという現象を根本的に解消することはできない。
【００２４】
このような問題に対し、本発明法により所定の粒度構成を有する高炉水砕スラグを硫化水素の発生源となる水底に敷設することによって、硫化水素の発生（さらには、海水の富栄養化）とこれにより引き起こされる青潮の発生を効果的に抑制することができる。また、水底に敷設された高炉水砕スラグは、先に述べた理由により底棲生物に対して良好な棲息環境を提供し、それらの棲息量の顕著な増大をもたらす。
【００２５】
本発明法により硫化水素の発生源となる水底（例えば、水底に形成された凹部）に高炉水砕スラグを敷設することにより、以下のような作用が得られる。
(1) 高炉水砕スラグは化学的な底質・水質浄化作用を有している。すなわち、高炉水砕スラグ中に含まれるＣａＯが水中に溶出することによって水中のｐＨが適度に高められ、この結果、硫化水素を発生させる硫酸還元菌の活動が抑制される。また、高炉水砕スラグに含まれるＣａＯ、Ｆｅ_２Ｏ_３によって水中の硫化水素を固定化することにより、水中の硫化水素の低減化が図られる。さらに、高炉水砕スラグ中に含まれるＣａＯによって水中の燐が吸着・固定され、青潮発生等の要因の一つである水の富栄養化が抑制される。このため高炉水砕スラグを水底の凹部等のような硫化水素の発生源に敷設した場合、その領域で底泥からの硫化水素の発生が抑制されるとともに、敷設材上部層の間隙水中での硫化水素の発生も抑制され、さらに、スラグ粒子への硫化水素や燐の固定化作用による水質浄化作用も得られる。また、敷設材の上部層は硫化水素が少なく溶存酸素の多い状態となるため着生する生物にとって棲息しやすい環境となり、生物の着生基盤としても高い機能を有することになる。
【００２６】
(2) 高炉水砕スラグは高温の溶融状態にある高炉スラグ（溶融スラグ）を噴流水で急冷して得られるものであるため、その形態や組織において他のガラス質材料には無い以下のような特質がある。すなわち、一般のガラス質材料は組織が緻密であるのに対し、高炉水砕スラグの場合には、溶融状態にあるスラグを噴流水で急冷する過程でスラグ中に溶け込んでいる窒素や水分などによってスラグが発泡するため、得られるスラグ粒子は無数の内部気孔を有する多孔質組織のガラス質材料となり、しかも比較的細かい粒子となる。また、同様の理由から高炉水砕スラグの粒子は角張った形状（表面に多数の尖った部分を有する形状）を有している。このような形態上の特徴から、高炉水砕スラグの集合物は一般のガラス質材料からなる粒状物の集合物に較べて充填間隙が大きく、加えて本発明で使用する高炉水砕スラグは比較的粗い粒度構成を有しているため、通水性が非常に優れている。このためスラグ粒子間の間隙の水が入れ替りやすく、この間隙での溶存酸素濃度が十分に確保されるため、底棲生物に良好な環境を提供することができる。
【００２７】
(3) 高炉水砕スラグを水底に敷設した場合、スラグからのＣａ分の微量溶解によって間隙水中のｐＨが８．５程度に維持されることで、硫酸還元菌の活性が弱められ、硫酸還元菌による硫化水素の発生が効果的に抑制されるが、特に高炉水砕スラグは上述したようにガラス質であることから、他のスラグに較べて含有成分の溶出や水中又は底泥中の成分との反応が非常にゆっくりと進行する。このため水中のｐＨを急激に上昇させたり、底質・水質の改善効果が短期間で消失することがない。
【００２８】
(4) 天然砂や天然石を硫化水素の発生源である水底の凹部に敷設した場合、凹部の内壁に敷設材による大きな圧力が作用し、敷設後ある程度の期間が過ぎると敷設材が凹部の内壁を押し広げて水平方向に広がってしまい、その結果、敷設当初は周囲の水底面と略同レベルであった敷設材の上面レベル（水底面）が大きく沈下し、これより水の停滞を生じるような凹部が再び形成されてしまうという問題がある。
これに対して高炉水砕スラグは天然砂や天然石に較べて内部摩擦角がかなり大きく、このため高炉水砕スラグを水底の凹部に敷設した場合、敷設材から凹部の内壁に作用する圧力が比較的小さい。このため天然砂や天然石を用いた場合のように敷設材が凹部の内壁を押し広げて水平方向に広がってしまう現象が生じにくく、敷設材の上面レベル（水底面）の沈下も生じにくい。特に、高炉水砕スラグは他のスラグに較べても内部摩擦角が大きく、このため凹部内壁に対する圧力が小さく、また他のスラグに較べて嵩密度も小さいため、自重による沈下も起こりにくい。したがって、敷設材の上面レベル（水底面）の沈下も最小限に抑えることができる。
【００２９】
これを図２及び図３に基づいて説明する。図２は敷設材として天然砂や天然石を用いた従来法、図３は敷設材として高炉水砕スラグを用いた本発明法を示している。まず、従来法のように天然砂や天然石を水底の凹部１に敷設した場合（図２(a)）、凹部１の内壁に敷設材２による大きな圧力Ｆが作用し、敷設後ある程度の期間が過ぎると、図２(b)に示すように敷設材２が凹部１の内壁を押し広げて水平方向に広がってしまう。その結果、敷設当初は周囲の水底面Ｙと略同レベルであった敷設材の水底面Ｘが沈下し、これより再び凹部１′が形成されてしまう。これに対して高炉水砕スラグを水底の凹部１に敷設した場合（図３(a)）、高炉水砕スラグは天然砂や天然石に較べて内部摩擦角がかなり大きいため、敷設材２から凹部１の内壁に作用する圧力Ｆが小さい。このため図３(b)に示すように敷設材２が凹部１の内壁を押し広げて水平方向に広がってしまう現象が生じにくく、敷設材２の水底面Ｘの沈下も生じにくい。
【００３０】
(5) 敷設材を水底に敷設する場合、敷設材を船で敷設場所に運搬し、これを船上から直接又はシュート等を介して硫化水素の発生源となる水底に投入することになるが、この際、水底を構成する泥質や堆積したヘドロが水中に巻き上げられて大量の浮泥が発生し、この浮泥により周辺水域の水質や水底が汚染されてしまうという問題がある。ここで、高炉水砕スラグは比較的多量の未反応Ｃａを含んでおり、このため個々のスラグ粒子の表面にも未反応Ｃａが存在している。このため敷設材として高炉水砕スラグを船上から水底に投入した場合、水底を構成する泥質や堆積したヘドロが水中に巻き上げられて大量の浮泥が発生するが、浮泥は水底に降下する途中のスラグの表面に存在するＣａ基により凝集・捕捉され、スラグとともに水底に沈降する。特に、スラグは天然砂や天然石等に較べて真比重が大きいので、浮泥を凝集・捕捉したスラグは水底に速やかに沈降する。この結果、敷設材の水底への投入に伴う浮泥の発生と、この浮泥による周辺水域の水質や水底の汚染が適切に防止できる。
【００３１】
本実施形態において高炉水砕スラグを敷設する対象となる水底とは、硫化水素の発生源である又は発生源となるおそれのある水底であり、具体的には、(1)水底に形成された凹部、(2)底層水中で硫化水素が検出された水域又は底層水中の溶存酸素濃度が所定値以下の水域の水底、(3)底層水の流速が所定値以下の水域の水底、(4)水中に水温又は／及び塩分濃度による密度躍層が形成された水域の水底、のいずれかが対象となる。また、適用される水域としては、港湾を含む海、河川、河口、湖沼等のいずれでもよい。
【００３２】
本実施形態において高炉水砕スラグを敷設する対象となる水底の凹部とは、通常は土砂採取や浚渫等によって水底に人為的に形成された穴状または溝状の凹部であるが、これに限定されるものではなく、例えば、自然に形成された水底の凹部や、土砂採取や元々の地形により傾斜面や浅い凹部が形成されている水底にケーソン等を設置することで人工的に形成された凹部等も対象となる。一般に凹部が形成される水底は泥質又は砂質である。このような水底に形成された凹部は、水が停滞しやすく、またヘドロも溜まりやすいため、硫化水素の発生源となりやすい。
なお、凹部の定義としては、水の停滞等を考慮した場合、一般には周囲の水底面よりも２ｍ以上深くなっている水底部を凹部としてよい。また、場合によっては、周囲の水底面よりも１ｍ以上深くなっている水底部、或いは０．５ｍ以上深くなっている水底部を凹部としてよい。
【００３３】
ここで、適用される凹部の種類や規模には特別な制約はないが、典型的な形態として以下のようものがある。
(a) 自然に存在する水底の凹部：このような水底の凹部は比較的面積が大きい。一般にこの種のもので本発明法の対象となる凹部は、平面的でみて最も幅が狭い部分の幅が５０ｍ以上、深さが２ｍ以上あるような規模の凹部である。
(b) 土砂採取や浚渫等によって水底に人為的に形成された凹部：このような水底の凹部は比較的面積が小さい。一般にこの種のもので本発明法の対象となる凹部は、平面的でみて最も幅が狭い部分の幅が１０ｍ以上、深さが５ｍ以上あるような規模の凹部である。
(c) 水底にケーソン等の構造物を設置した場所において、この構造物と水底（例えば、自然に存在する水底の凹部や、土砂採取や元々の地形により傾斜面や浅い凹部が形成されている水底）とにより結果的に形成された凹部：このような水底の凹部も比較的面積が小さい。一般にこの種のもので本発明法の対象となる凹部は、平面的でみて最も幅が狭い部分の幅が１０ｍ以上、深さが２ｍ以上あるような規模の凹部である。
【００３４】
凹部内へ敷設材（高炉水砕スラグ）の敷設形態に特に制限はないが、凹部内に敷設された敷設材上面により形成される水底面は、その周囲の水底面と略同等かそれ以上の高さを有することが好ましい。また、少なくとも、敷設された敷設材により形成される水底面Ａの平均水深ｄ_１と凹部周囲（凹部近傍の周囲）の水底面Ｂの平均水深ｄ_０との差［ｄ_１−ｄ_０］が２ｍ以下、好ましくは１ｍ以下、より好ましくは０．５ｍ以下、特に好ましくは０．３ｍ以下（但し、いずれも［ｄ_１−ｄ_０］がマイナス値の場合を含む）となるようにすることが特に望ましい。この差［ｄ_１−ｄ_０］が２ｍ以下、好ましくは１ｍ以下、より好ましくは０．５ｍ以下、特に好ましくは０．３ｍ以下であれば、凹部が十分に浅くなるため凹部内外での水の流出入が円滑に行われるようになり（すなわち、凹部内での水の停滞がなくなる）、夏期等に凹部内の水が無酸素状態になるような現象が適切に防止できる。
【００３５】
ここで、敷設材上面により形成される水底面Ａの平均水深ｄ_１とは、敷設材により形成される水底面Ａに起伏や凹凸があるために水深にバラツキがある場合に、その水底面を平らに均した際の水深であり、また、凹部周囲（凹部近傍の周囲）の水底面Ｂの平均水深ｄ_０とは、凹部周囲の水底面Ｂに起伏や凹凸があるために水深にバラツキがある場合に、その水底面を平らに均した際の水深である。
【００３６】
また、上述のように水底の形態（凹部）に基づいて敷設材の敷設場所を選定する以外に、底層水中の硫化水素又は溶存酸素濃度を測定し、底層水中で硫化水素が検出された水域又は底層水中の溶存酸素濃度が所定値以下の水域の水底に、敷設材（高炉水砕スラグ）を敷設するようにしてもよい。
ここで、底層水とは水底の近くに存在する水のことであり、一般には水の深さ方向で水底から２ｍ以内、好ましくは１ｍ以内の水であればよく、このような底層水で硫化水素が検出され、或いは測定された溶存酸素濃度が所定値以下である水域の水底に敷設材を敷設する。硫化水素の場合は、それが底層水から検出されれば、その水域の水底に敷設材を敷設する。また、溶存酸素濃度の場合は、一般に底層水の溶存酸素濃度が飽和溶存酸素濃度の１０％以下であると硫酸還元菌の作用によって硫化水素が発生するおそれがあるため、溶存酸素濃度が飽和溶存酸素濃度の１０％以下の水域の水底に敷設材を敷設することが好ましい。また、一般に底層水の溶存酸素濃度が飽和溶存酸素濃度の６０％以下であると底棲生物の棲息に問題を生じるため、溶存酸素濃度が飽和溶存酸素濃度の６０％以下の水域の水底に敷設材を敷設するようにしてもよい。
【００３７】
また、底層水の流速を測定し、その流速が所定値以下である水域の水底に、敷設材（高炉水砕スラグ）を敷設するようにしてもよい。底層水の流速が小さく、水の停滞が生じやすい水底が硫化水素の発生源となりやすいからである。なお、底層水とは先に述べた通り水底の近くに存在する水のことであり、一般には水の深さ方向で水底から２ｍ以内、好ましくは１ｍ以内の水であればよい。
一般に底層水の流速が２０ｃｍ／秒以下の水域は底層水の溶存酸素濃度や硫化水素濃度が水底の影響を強く受けるため、そのような流速の水域の水底に敷設材を敷設することが好ましい。
【００３８】
さらに、水中に水温や塩分濃度による密度躍層が形成された水域の水底に、敷設材（高炉水砕スラグ）を敷設するようにしてもよい。水中に密度躍層が形成されると、大気から水中に供給される酸素が底層水まで拡散しにくくなり、硫化水素が発生しやすくなる。
密度躍層が形成されたことは水中の塩分濃度及び／又は水温等を測定することにより判定することができ、密度躍層が形成されたと判定されたときは、その水域の水底に敷設材を敷設する。
以上のように、(a)底層水中で硫化水素が検出された水域又は底層水中の溶存酸素濃度が所定値以下の水域の水底、(b)底層水の流速が所定値以下の水域の水底、(c)水中に水温又は／及び塩分濃度による密度躍層が形成された水域の水底、のいずれかを敷設材の敷設場所とする場合は、例えば、閉鎖性の高い港や湾（例えば、リアス式海岸等にある湾）等が対象とすることができる。
【００３９】
上述したような高炉水砕スラグの作用からして、敷設材としては高炉水砕スラグ１００％が最も好ましいと言えるが、高炉水砕スラグとそれ以外の素材、例えば製鋼スラグ等の高炉水砕スラグ以外のスラグやスラグ以外の素材を併用してもよい。高炉水砕スラグ以外の鉄鋼製造プロセスで発生するスラグとしては、高炉で発生する高炉徐冷スラグ、予備処理、転炉、鋳造等の工程で発生する脱炭スラグ、脱燐スラグ、脱硫スラグ、脱珪スラグ、鋳造スラグ等の製鋼スラグ、鉱石還元スラグ、電気炉スラグ等を挙げることができるが、これらに限定されるものではなく、また２種以上のスラグを混合して用いることもできる。また、これらのスラグは、水和処理、炭酸化処理、エージング、水和硬化、炭酸化硬化等を経たものを用いてもよい。また、スラグ以外の素材としては、資源のリサイクルという観点からは都市ゴミスラグ、廃コンクリート、モルタルや耐火物の廃材等が好ましいが、それ以外に例えば建設発生残土、フライアッシュ、天然砂、天然石等を用いてもよい。
また、都市ゴミスラグや廃コンクリート等は、水和処理、炭酸化処理、エージング、水和硬化、炭酸化硬化等を経たものを用いてもよい。
【００４０】
敷設材として高炉水砕スラグとそれ以外の素材とからなるものを用いる場合、上述したような高炉水砕スラグによる作用を適切に得るために、凹部に敷設された敷設材の５０mass％以上、好ましくは８０mass％以上が高炉水砕スラグで構成されることが望ましい。また、その場合には高炉水砕スラグとそれ以外の素材が混合されるか、又は高炉水砕スラグが上層側、それ以外の素材が下層側になるようにして凹部内に敷設されることが好ましい。
【００４１】
また、上層を高炉水砕スラグを含む敷設材で構成し、下層をそれ以外の素材からなる敷設材で構成する場合、上述したような高炉水砕スラグによる作用を適切に得るために、上層中の高炉水砕スラグの含有率は６０mass％以上、好ましくは８０mass％以上とすることが望ましい。
また、このように凹部内の敷設材の上層を高炉水砕スラグ又は高炉水砕スラグを６０mass％以上（好ましくは８０mass％以上）含む敷設材で構成する場合、この上層の厚みは０．１ｍ以上、好ましくは０．５ｍ以上とすることが望ましい。この上層の厚みが０．１ｍ未満では、その下方の硫化水素を含んだ水が簡単に通過してしまい、上述したような作用が十分に得られなくなる恐れがある。また、厚みが０．１ｍ未満では施工の際の厚み管理自体も難しくなる。また、特にこの上層の厚みが１ｍ以上あれば、当該上層部は底泥と混合しなくなるため、スラグが固結するようなことがなく、このため生物の棲息環境として好適な砂質水底を提供できる。
【００４２】
なお、高炉水砕スラグとともに他のスラグを使用する場合において、脱珪スラグ、脱炭スラグ等の製鋼スラグを用いた場合、これらのスラグは酸化鉄の含有量が高いため高炉水砕スラグ等に較べて硫化水素や燐を固定化する作用が大きいという特徴がある。このため、例えば凹部内の敷設材の下層を製鋼スラグ又は製鋼スラグを含む敷設材で構成することにより、底泥中の硫化水素や燐を効果的に固定することができる。下層を製鋼スラグを含む敷設材で構成する場合、下層中の製鋼スラグの含有率は６０mass％以上、好ましくは８０mass％以上とすることが望ましい。下層中の製鋼スラグの含有率が６０mass％未満では、上述した製鋼スラグに特有の作用が十分に得られない。
【００４３】
また、このように凹部内の敷設材の下層を製鋼スラグ又は製鋼スラグを６０mass％以上（好ましくは８０mass％以上）含む敷設材で構成する場合、この下層の厚みは０．１ｍ以上、好ましくは０．３ｍ以上とすることが望ましい。この下層の厚みが０．１ｍ未満では、製鋼スラグによる泥質中の硫化水素や燐の固定が十分に行われる前に、硫化水素や燐を含んだ水がこの下層を通過してしまい、硫化水素や燐の固定化作用が十分に得られなくなるおそれがある。また、厚みが０．１ｍ未満では、施工の際の厚み管理自体も難しくなる。
【００４４】
以上述べたような各スラグの特性からして、凹部内への敷設材の敷設形態としては、例えば、以下のようなものが考えられる。
▲１▼ 敷設材の全部：高炉水砕スラグ
▲２▼ 敷設材の上層：高炉水砕スラグ、敷設材の下層：高炉水砕スラグ以外のスラグ及び／又はスラグ以外の素材
▲３▼ 敷設材の上層：高炉水砕スラグ、敷設材の下層：製鋼スラグ
▲４▼ 敷設材の上層：高炉水砕スラグ、敷設材の中層：スラグ以外の素材又はスラグとスラグ以外の素材との混合物、敷設材の下層：製鋼スラグ
【００４５】
図４(a)〜(d)は、それぞれ水底の凹部１に敷設材２（高炉水砕スラグ又は高炉水砕スラグを含む敷設材）を敷設した状態を示しており、図４(a)に示すように、敷設材２はこれにより形成される水底面Ａの平均水深ｄ_１と凹部周囲の水底面Ｂの平均水深ｄ_０との差［ｄ_１−ｄ_０］が２ｍ以下、好ましくは１ｍ以下となるように（特に好ましくは、敷設材２により形成される水底面Ａが凹部周囲の水底面Ｂと略同等かそれ以上の高さとなるように）敷設される。
【００４６】
図４(a)は、高炉水砕スラグ１００％の敷設材２又は高炉水砕スラグとそれ以外の素材（例えば、廃コンクリート）とを混合した敷設材２を凹部１内に敷設した実施形態を示している。また、図４(b)は、敷設材２として高炉水砕スラグとそれ以外の素材を用いたもので、高炉水砕スラグ以外の素材２１（例えば、廃コンクリート）を下層側に、高炉水砕スラグ２０を上層側にそれぞれ敷設した実施形態を示している。また、図４(c)は、敷設材２として高炉水砕スラグ２０ａとその他のスラグ２０ｂ（例えば、製鋼スラグ）を用いたもので、高炉水砕スラグ２０ａを上層側に、それ以外のスラグ２０ｂを下層側にそれぞれ敷設した実施形態を示している。さらに、図４(d)は、浅い凹部が形成されている水底にケーソン３を設置することで人工的に形成された凹部１内に敷設材２（例えば、上記(a)〜(c)のような形態の敷設材）を敷設した実施形態を示している。
【００４７】
また、凹部以外の水底に敷設材を敷設する場合も、敷設材中の高炉水砕スラグの含有率は６０mass％以上、好ましくは８０mass％以上とすることが望ましく、特に高炉水砕スラグのみからなる敷設材が最も好ましい。高炉水砕スラグ以外の敷設材としては、上述した各種スラグや都市ゴミスラグ、廃コンクリート等を用いることができる。また、敷設材の厚みは、上述したと同様の理由から０．１ｍ以上、好ましくは０．５ｍ以上とすることが望ましい。
【００４８】
以上述べた青潮発生防止等を目的とする高炉水砕スラグの敷設（覆砂）に関する好ましい実施形態を整理すると、以下のようになる。
（１） 硫化水素発生源である水底に、粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上、好ましくは粒径１．０ｍｍ以上のスラグ粒子の割合が７０mass％以上の高炉水砕スラグを敷設する水中の環境改善方法。
（２） 水底に形成された凹部内に、全部又は一部が、粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上、好ましくは粒径１．０ｍｍ以上のスラグ粒子の割合が７０mass％以上の高炉水砕スラグからなる敷設材を敷設する水中の環境改善法。
（３） 底層水中で硫化水素が検出された水域又は底層水中の溶存酸素濃度が所定値以下の水域の水底に、全部又は一部が、粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上、好ましくは粒径１．０ｍｍ以上のスラグ粒子の割合が７０mass％以上の高炉水砕スラグからなる敷設材を敷設する水中の環境改善法。
【００４９】
（４） 底層水の流速が所定値以下の水域の水底に、全部又は一部が、粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上、好ましくは粒径１．０ｍｍ以上のスラグ粒子の割合が７０mass％以上の高炉水砕スラグからなる敷設材を敷設する水中の環境改善法。
（５） 水中に水温又は／及び塩分濃度による密度躍層が形成された水域の水底に、全部又は一部が、粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上、好ましくは粒径１．０ｍｍ以上のスラグ粒子の割合が７０mass％以上の高炉水砕スラグからなる敷設材を敷設する水中の環境改善方法。
【００５０】
（６） 水底に形成された凹部内に、全部又は一部が、粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上、好ましくは粒径１．０ｍｍ以上のスラグ粒子の割合が７０mass％以上の高炉水砕スラグからなる敷設材を敷設し、該敷設材により形成される水底面の平均水深ｄ_１と凹部周囲の水底面の平均水深ｄ_０との差［ｄ_１−ｄ_０］を２ｍ以下（但し、［ｄ_１−ｄ_０］がマイナス値の場合を含む）とする水中の環境改善方法。
（７） 上記（１）〜（６）の環境改善方法において、敷設材が高炉水砕スラグとそれ以外の素材とからなり、該敷設材は、高炉水砕スラグとそれ以外の素材が混合された状態であるか、又は高炉水砕スラグが上層側、それ以外の素材が下層側になるようにして水底に敷設される水中の環境改善方法。
【００５１】
（８） 上記（１）〜（７）の環境改善方法において、水底に敷設された敷設材の５０mass％以上が高炉水砕スラグからなる水中の環境改善方法。
（９） 上記（８）の環境改善方法において、水底に敷設された敷設材の最上部層が、高炉水砕スラグを６０mass％以上含む水中の環境改善方法。
（１０） 硫化水素の発生源となる水底に敷設される青潮防止材であって、粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上、好ましくは粒径１．０ｍｍ以上のスラグ粒子の割合が７０mass％以上の高炉水砕スラグからなることを特徴とする水中の環境改善用資材。
【００５２】
（Ｂ）養浜、浅場造成又は干潟造成等を目的とする高炉水砕スラグの敷設
養浜とは、海岸の浸食等により砂浜が消失した海岸や人工ビーチを造成する海岸に外部から砂を供給することを指す。
また、干潟とは、満潮時には水没するが干潮時には干上がり、表面に砂泥が堆積している平坦な場所を指し、一般に干潟は河口域や内湾の奥に発達している。また、浅場とは文字通り水深が数ｍ以下の浅い海域を指す。海岸から沖合に向かって伸びる海底では、おおよそ水深数ｍほどのところで所謂灘落ちと呼ばれるやや急な斜面に移行する地形がしばしば認められるが、一般に、浅場とはこの灘落ち点よりも浅い側の海域を指す。
【００５３】
砂浜や干潟、浅場は貝類やゴカイ類等の底棲生物の主要な棲息環境であるが、本発明法により所定の粒度構成を有する高炉水砕スラグを養浜材或いは干潟・浅場造成材として敷設することによって、先に述べたように底棲生物にとって棲息しやすい環境を提供することができ、底棲生物の棲息量を顕著に増大させることができる。
【００５４】
また、本発明法に敷設される高炉水砕スラグは、白色で且つ元々の高炉水砕スラグに含まれる針状物の割合が非常に少ないため、天然の砂地同様の外観で、しかも人や生物が針状物で傷付いたりすることがない安全な砂地（砂浜、干潟、浅場）を形成することができる。
また、養浜材、干潟や浅場の造成材として敷設された高炉水砕スラグは、先に（Ａ）で述べたような底質・水質の浄化機能を有し、また後述するようなケイ酸塩イオンの放出源としての機能も有することから、底質・水質浄化作用やスラグから溶出したケイ酸塩イオンによる海藻類等の生育促進作用も得られる。
本実施形態が適用される水浜又は水域としては、港湾を含む海、河川、河口、湖沼等のいずれでもよい。
【００５５】
以上述べた養浜、干潟・浅場造成等を目的とする高炉水砕スラグの敷設に関する好ましい実施形態を整理すると以下のようになる。
（１） 水浜に、養浜材として粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上、好ましくは粒径１．０ｍｍ以上のスラグ粒子の割合が７０mass％以上の高炉水砕スラグを敷設することにより、養浜を行う水中又は水浜の環境改善方法。
（２） 干潟を造成（修復を含む）すべき場所に、干潟造成材として粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上、好ましくは粒径１．０ｍｍ以上のスラグ粒子の割合が７０mass％以上の高炉水砕スラグを敷設することにより、干潟造成を行う水中又は水浜の環境改善方法。
（３） 浅場を造成（修復を含む）すべき海底部に、浅場造成材として粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上、好ましくは粒径１．０ｍｍ以上のスラグ粒子の割合が７０mass％以上の高炉水砕スラグを敷設することにより、浅場造成を行う水中又は水浜の環境改善方法。
【００５６】
（Ｃ）磯焼け防止等を目的とする高炉水砕スラグの敷設
本実施形態が適用される磯焼けが生じている海底部とは、岩礁や人工魚礁などの海藻着生基盤の表面が石灰藻に覆われることにより、コンブ、ワカメ、アラメなどの有用海藻が消失し又は消失しつつある海底部を指す。
岩礁や人工魚礁などの海藻着生基盤の表面が石灰藻に覆われる所謂“磯焼け”状態となった海域は、魚介類の餌となる有用海藻（例えば、コンブ、ワカメ、アラメなど）が繁殖せず、その海域の漁業生産量が著しく低下するという問題がある。
【００５７】
従来、磯焼けが生じた海域に対しては鋼製の藻礁を設置するなどの対策が試みられてきたが、鋼製藻礁を設置すると２年間程度は石灰藻以外の海藻が藻礁に繁殖して藻礁部分は磯焼け状態が解消されるものの、３年程度経過すると鋼製藻礁も石灰藻に覆われてしまい、その効果が無くなってしまう。このため再度鋼製藻礁を設置するなどの対策が必要となり、磯焼け防止の抜本的な解決策とはなり得ていない。また最近では、磯焼けが生じた海域のウニを駆除することによって藻場を復活させた例もあるが、ウニの駆除は人力で行う必要があるため効率が悪く、コストも多くかかる上、一度に適用できる海域が狭いなど、磯焼け解消の切り札とはなり得ていない。
【００５８】
一方、海水中のケイ酸塩濃度を高めることにより珪藻類が増殖し、その結果として石灰藻の増殖が抑制されることが知られており、このようなメカニズムを利用した磯焼けの改善方法として、コンクリート製などの藻礁の表面に成分の溶解度を調整したガラスプレートを張り付け、これを磯焼け海域に沈設する方法が提案されている。また、特開平６−３３５３３０号公報には、構成成分の海水中への溶出により海藻類を増殖させることを目的として、ケイ素、ナトリウム及び／又はカリウム、鉄を含有するガラス質材料からなる藻場増殖材を海中に沈設する方法が提案されている。
【００５９】
しかし、このような従来技術において海水中のケイ酸塩濃度を高めるために用いられるガラス質材料は人工物であるため高価であり、これを磯焼けが発生したり、何らかの原因で海藻成育環境が衰退・消失した広い海域に大量に設置するとなると膨大な費用がかかる。また、本発明者らが検討したところによれば、従来技術で用いられる人工のガラス質材料は海水などへのケイ素の溶出性が必ずしも十分ではなく、また沈設量も限られるため、ケイ素の供給はその設置場所近傍に限られてしまい、有効な磯焼け改善効果や海藻成育環境の改善効果が得られないことが判った。
【００６０】
このような問題に対して、本発明法により所定の粒度構成を有する高炉水砕スラグを磯焼けが生じている又は生じる恐れのある海域或いは海藻成育環境が衰退・消失している海域の水底に敷設することにより、高炉水砕スラグが海藻類の生育に有効なケイ酸塩イオンの放出源となり、磯焼けの改善又は予防や海藻類の生育促進を図ることができる。また、水底に敷設された高炉水砕スラグは、先に述べた理由により底棲生物に対して良好な棲息環境を提供し、それらの棲息量の顕著な増大をもたらす。
また、高炉水砕スラグを水底に敷設する際には、他の材料（例えば、製鋼スラグ、フライアッシュ、けい砂、山砂、海砂、粘土など）と混合した状態で用いることができるが、この場合でも所望のケイ酸塩溶出量を確保するために必要とされる量の高炉水砕スラグを用いる必要がある。
【００６１】
高炉水砕スラグはＳｉＯ_２成分とＣａＯ成分とを多量に含むガラス質材料（一般に、ＳｉＯ_２：３０mass％以上、ＣａＯ：３５mass％以上）であり、このため水底に敷設された高炉水砕スラグは、これに含まれるＣａＯの溶解により生じたＣａイオンのケイ酸塩網目構造へのアタックによりケイ酸塩網目構造が分断され、この結果、水中にケイ酸塩イオンを溶出させる。すなわち、高炉水砕スラグの場合には、水分子によるケイ酸塩網目構造の切断により徐々にケイ酸塩イオンが水中に溶解する作用に加えて、スラグから溶解したＣａイオンによるケイ酸塩網目構造の分断によりケイ酸塩イオンが水中に溶解する作用が得られ、したがって、このような高炉水砕スラグのケイ酸塩イオンの溶出機構は、先に従来技術として挙げた人工のガラス質材料と同様の水分子によるケイ酸塩イオンの溶出作用と、Ｃａイオンのアタックによるケイ酸塩イオンの溶出作用とが組み合わされたものとなり、人工のガラスよりもはるかにケイ酸塩が溶出しやすい。
【００６２】
さらに、高炉水砕スラグは高温の溶融状態にある高炉スラグ（溶融スラグ）を噴流水で急冷して得られるものであるため、その形態や組織において人工のガラス質材料には無い以下のような特質がある。
すなわち、一般に人工のガラス質材料は組織が緻密であるのに対し、高炉水砕スラグは、先に述べたように無数の内部気孔を有する多孔質組織のガラス質材料となり、しかも比較的細かい粒子となる。また、同様の理由から高炉水砕スラグの粒子は角張った形状（表面に多数の尖った部分を有する形状）を有している。したがって、このような形態及び組織面での特質から、高炉水砕スラグは人工のガラス質材料を破砕装置で破砕して得られたような粒状物に較べて比表面積が格段に大きく、その分ケイ酸塩イオンが溶出しやすいという特徴がある。さらに、高炉水砕スラグ粒子表面に多数存在する尖った部分は微細な形態であるため、微細な粉体が成分の溶解性が高いのと同様に、ケイ酸塩の溶解に非常に適している。
【００６３】
また、上記のような形態上の特徴から、高炉水砕スラグの積層物は人工のガラス質材料を破砕装置で破砕して得られたような粒状物の積層物に較べて充填間隙が大きく、しかも本発明で使用する高炉水砕スラグは比較的粗い粒度構成を有しているため、通水性が非常に優れている。このため高炉水砕スラグの積層物から溶出するケイ酸塩イオンは、人工のガラス質材料のそれに較べて積層物の外部に拡散し易いという特徴がある。
【００６４】
また、高炉水砕スラグはＣａイオンを溶出するため、水中に設置された場合に先に述べたような硫化水素の発生抑制効果を有し、このため高炉水砕スラグの積層物内では硫酸還元が起こりにくく、天然の砂やガラスの積層物内に較べて硫化水素が少なく溶存酸素の多い状態となる。この状態は着生する生物にとって棲息しやすい状態であると言え、したがって、海中に設置された高炉水砕スラグはケイ酸塩イオンの供給源であるとともに、生物の着生基盤としても機能し、この点からも磯焼けの改善に有効である。
【００６５】
ところで、鉄鋼製造プロセスにおいて副生成物として得られるスラグとしては、高炉水砕スラグ以外にも高炉徐冷スラグや製鋼スラグ（例えば、脱炭スラグ、脱燐スラグ、脱硫スラグ、脱珪スラグ、電気炉製鋼スラグなど）などがあるが、これらのスラグ粒子は組織が緻密で高炉水砕スラグのような多孔質組織ではなく、しかも、スラグ粒子の粒径も高炉水砕スラグに較べて格段に大きく、またこれを粉砕処理した場合でも個々のスラグ粒子の形状は高炉水砕スラグのような角張った形状（表面に多数の尖った部分を有する形状）にはならない。このため比表面積は高炉水砕スラグに較べて格段に小さい。また、高炉徐冷スラグは、硫化物の溶出量が大きいため、海水のＣＯＤを高めたり、スラグ積層物の充填間隙中で硫化水素の濃度が高くなるという問題がある。また、製鋼スラグの多くはＳｉＯ_２の含有量が少なくＣａＯの含有量が多いため、この面からもケイ酸塩の溶解量が少ない。したがって、これらのスラグからは水中へのケイ酸塩イオンの供給が十分にできず、いずれも磯焼け防止材には適さない。
【００６６】
なお、高炉水砕スラグの塩基度は四成分塩基度（ＣａＯ＋Ａｌ_２Ｏ_３＋ＭｇＯ）／ＳｉＯ_２で１．６〜２．５、望ましくは１．６〜２．０であることが好ましい。高炉水砕スラグの上記塩基度が１．６未満ではスラグ中でのＳｉＯ_２の安定度が高まるためケイ酸塩イオンの海水中への溶出性が低下する傾向がある。一方、上記塩基度が２．０を超え、特に２．５を超えるとスラグ中の結晶質の量が増加し、ケイ酸塩の溶出と同時にＣａの溶出も増加するため、ケイ酸塩がＣａと沈殿物を生成してケイ酸塩の水中への供給量が低下する場合がある。
【００６７】
珪藻類の増殖に必要な水中のケイ酸塩イオンの濃度は１０μmol／Ｌ以上とされているが、このようなケイ酸塩イオン濃度は高炉水砕スラグの敷設によって容易に達成される。これにより海底の海藻着生基盤表面に珪藻類が安定的に繁殖し、この結果、石灰藻の増殖が抑えられるとともに、昆布やアラメなどの大型の海藻類が繁殖する。また、海藻着生基盤表面に繁殖した珪藻類は、石灰藻とは異なり魚介類の餌となるため、珪藻類が繁殖すれば磯焼け海域において水産資源が増加する。また、高炉水砕スラグからのケイ酸塩イオンの溶出は長期間継続するため、珪藻類の増殖及びこれに伴う磯焼け防止効果も長期間に亘って継続することになる。
【００６８】
次に、磯焼け海域の藻場造成法について特に好ましい実施形態について説明する。
この藻場造成法では、磯焼けが生じている海底部において海藻着生基盤の周囲又は近傍に高炉水砕スラグを設置するのが好ましい。これにより高炉水砕スラグから溶出したケイ酸塩イオンにより海藻着生基盤周囲の海水が高ケイ酸塩濃度化し、海藻着生基盤に珪藻類を効果的に繁殖させることができる。
海藻着生基盤は天然又は人工のいずれでもよく、前者の場合は岩礁などであり、後者の場合には鋼製ブロック、コンクリートブロック、天然石、スラグ塊などである。また、この後者の場合には、高炉水砕スラグを敷設した後に海藻着生基盤を設置してもよい。人工の海藻着生基盤を設置する海底は、岩礁帯、砂地などを問わない。
【００６９】
また、高炉水砕スラグは、現に磯焼けを生じている海域だけでなく、磯焼けが生じる恐れのある海底部に設置することができ、これにより当該海域での磯焼けを予防する。この場合も高炉水砕スラグは、先に述べたものと同様の形態で設置される。
なお、上述したように本実施形態である磯焼け海域の藻場造成法や磯焼け防止法が適用される主たる海域（磯焼けを現に生じ又は生じる恐れのある海域）は主として外海に面した海域であり、したがって所謂赤潮が生じるような河川流入栄養塩などにより富栄養化した海域とは対照をなすような海域である。
【００７０】
以上述べた磯焼け防止等を目的とする高炉水砕スラグの敷設に関する本発明法の好ましい実施形態を整理すると以下のようになる。
（１） 磯焼けが生じている海底部に、磯焼け防止材として粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上、好ましくは粒径１．０ｍｍ以上のスラグ粒子の割合が７０mass％以上の高炉水砕スラグを敷設することにより、磯焼け海域での藻場造成を行う水中の環境改善方法。
（２） 上記（１）の環境改善方法において、天然又は人工の海藻着生基盤の周囲又は近傍に高炉水砕スラグを敷設することにより、磯焼け海域での藻場造成を行う水中の環境改善方法。
（３） 上記（２）の環境改善方法において、高炉水砕スラグを敷設した後、人工の海藻着生基盤を設置することにより、磯焼け海域での藻場造成を行う水中の環境改善方法。
【００７１】
（４） 磯焼けが生じるおそれがある海底部に、磯焼け防止材として粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上、好ましくは粒径１．０ｍｍ以上のスラグ粒子の割合が７０mass％以上の高炉水砕スラグを敷設することにより、磯焼けを防止する水中の環境改善方法。
（５） 上記（４）の環境改善方法において、天然又は人工の海藻着生基盤の周囲又は近傍に高炉水砕スラグを敷設することにより、磯焼けを防止する水中の環境改善方法。
（６） 上記（５）の環境改善方法において、高炉水砕スラグを敷設した後、人工の海藻着生基盤を設置することにより、磯焼けを防止する水中の環境改善方法。
（７） 磯焼けが発生している海底部又は磯焼けの発生を予防すべき海底部に敷設される磯焼け防止材であって、粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上、好ましくは粒径１．０ｍｍ以上のスラグ粒子の割合が７０mass％以上の高炉水砕スラグからなる水中の環境改善用資材。
【００７２】
（Ｄ）赤潮発生防止を目的とする高炉水砕スラグの敷設
赤潮とは水中の微生物、とりわけ植物プランクトンが異常増殖して海水が着色する現象であり、近年、養殖魚類（例えば、ハマチやタイなど）を大量斃死させるなど、特に養殖漁業に大きな被害を及ぼしていることから、その防止対策が切望されている。
赤潮を起こす生物の種類は多岐にわたると考えられるが、その中でもシャットネラなどの特定の鞭毛藻類の大増殖が養殖魚類の大量斃死を招く赤潮の主要な原因であると考えられている。赤潮は富栄養化の進行した海域において発生することから、赤潮の防止には覆砂や浚渫、下水道整備による河川流入栄養塩の低減化が有効であるとされている。
【００７３】
しかしながら、覆砂や浚渫は工事完了後に新たに堆積する有機物によってその効果が失われてしまい、また、工事可能な海域が比較的浅い海域に限られるため、赤潮の大発生が問題となる瀬戸内海中心部などへの適用は困難である。また、これらの工事には多大な費用がかかり、このことも適用範囲が限られる要因となる。また、下水道整備による河川流入栄養塩の低減化は、海域全体の栄養塩量を減らすには有効であるが、これも瀬戸内海中心部のような海岸から離れた場所では、夏期の海水停滞期に表層海水の貧栄養化の原因となり、この貧栄養化によって表層海水中の珪藻類が減少することが、赤潮の原因となるシャットネラなどの鞭毛藻類の増殖要因の一つとなる。
【００７４】
最近、赤潮防止対策の一つとして可溶性のケイ素（ケイ酸塩イオン）の海水中への付与により珪藻類を繁殖させ、赤潮の原因となるシャットネラなどの鞭毛藻類の増殖を抑制する方法が検討され、この方法に関して、可溶性のケイ素を含有した人工のガラス質材料を浮体に装着して海中に設置する赤潮予防方法が特開平１０−９４３４１号公報に提案されている。
可溶性のケイ素の海水中への付与は貧栄養状態となった表層海水中の珪藻類を繁殖させることが知られており、珪藻類は赤潮の原因となるシャットネラなどの鞭毛藻類の競合種であり、しかも鞭毛藻類よりも増殖力が高いため、珪藻類が表層海水中に安定に存在するとシャットネラなどの鞭毛藻類の異常増殖が抑制され、その結果、赤潮の発生が防止されることになる。
【００７５】
しかし、上記のような従来技術において海水中のケイ酸塩濃度を高めるために用いられるガラス質材料は人工物であるため高価であり、これを赤潮が発生した広い海域に大量に設置するとなると膨大な費用がかかる。また、先に述べたように、本発明者らが検討したところによれば、従来技術で用いられる人工のガラス質材料は海水などへのケイ素の溶出性が必ずしも十分ではなく、また沈設量も限られるため、ケイ素の供給はその設置場所近傍に限られてしまい、有効な赤潮防止効果が得られないことが判った。
このような問題に対して、本発明法により所定の粒度構成を有する高炉水砕スラグを赤潮防止材として水底に敷設することにより、高炉水砕スラグがケイ酸塩イオンの放出源となり、赤潮の発生が効果的に抑えられる。また、水底に敷設された高炉水砕スラグは、先に述べた理由により底棲生物に対して良好な棲息環境を提供し、それらの棲息量の顕著な増大をもたらす。
【００７６】
高炉水砕スラグを水底に敷設する際には、他の材料（例えば、製鋼スラグ、フライアッシュ、けい砂、山砂、海砂、粘土など）と混合した状態で用いることができるが、この場合でも所望のケイ素（ケイ酸塩イオン）溶出量を確保するために必要とされる量の高炉水砕スラグを用いる必要がある。
高炉水砕スラグがケイ酸塩イオンの放出源として優れた特性を有することは先に（Ｃ）で述べた通りであり、したがって、この実施形態の環境改善法においても、使用される高炉水砕スラグの組成や性状、高炉水砕スラグの敷設形態、高炉水砕スラグからのケイ酸塩イオンの溶出機構、その他の高炉水砕スラグの機能などは、先に（Ｃ）に関して述べたものと同様である。
【００７７】
また、本実施形態による赤潮防止法において、高炉水砕スラグは水深１５ｍ以内（以浅）、好ましくは１０ｍ以内（但し、いずれも干潮時の水深）に設置するのが望ましい。これは、高炉水砕スラグの設置深度があまり大きいと溶出したケイ酸塩イオンが表層海水に到達しにくくなり、表層海水のケイ酸塩濃度を高める上で効率が悪いからである。
また、赤潮発生海域が沿岸に近い場合（例えば、沿岸から数ｋｍ以内の場合）には、水深１５ｍ以内、好ましくは１０ｍ以内の海底を覆うように高炉水砕スラグを敷設すればよく、この高炉水砕スラグから溶出したケイ酸塩イオンにより沿岸海域の海水が高ケイ酸塩濃度化し、この海水が海流によって沖合に流されるため、その海域一帯の表層海水のケイ酸塩濃度が高まり、珪藻類を効果的に増殖させることができる。
【００７８】
珪藻類の増殖に必要な海水中でのケイ酸塩イオンの濃度は１０μmol／Ｌ以上とされているが、このようなケイ酸塩イオン濃度は本発明法により高炉水砕スラグを海中に設置すること、好ましくは水深１５ｍ以内（より好ましくは水深１０ｍ以内）の海中に設置することによって容易に達成される。これにより表層海水中に珪藻類（シャットネラなどの鞭毛藻類の競合種）が安定的に繁殖し、赤潮の原因となるシャットネラなどの鞭毛藻類の異常増殖が防止される。また、珪藻類の安定的な繁殖は、これを食料とする魚介類の増殖にも効果があり、水産資源の増加にも効果がある。また、高炉水砕スラグからのケイ酸塩イオンの溶出は長期間継続するため、珪藻類の増殖及びこれに伴う赤潮防止効果も長期間に亘って継続することになる。
【００７９】
本実施形態による赤潮防止法が適用される主たる海域（旧来の赤潮多発海域）は主として内海や湾などにおいて河川流入栄養塩などにより富栄養化した海域であり、したがって所謂“磯焼け”が生じるような海域とは対照をなすような海域である。
また、以上の実施形態では本発明を海水域に適用する場合について説明したが、赤潮は汽水域や淡水域でも発生するものであり、したがって、本実施形態による赤潮防止方法はこれらの水域に対しても適用することができる。
【００８０】
以上述べた赤潮発生防止を目的とする高炉水砕スラグの敷設に関する好ましい実施形態を整理すると以下のようになる。
（１） 海水域、汽水域又淡水域において、水中に赤潮防止材として粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上、好ましくは粒径１．０ｍｍ以上のスラグ粒子の割合が７０mass％以上の高炉水砕スラグを設置することにより赤潮発生を防止する水中の環境改善方法。
（２） 上記（１）の環境改善法において、水深１５ｍ以内の水中に高炉水砕スラグを設置することにより赤潮発生を防止する水中の環境改善方法。
（３） 赤潮が発生している海域又は赤潮の発生を予防すべき海域に設置される赤潮防止材であって、粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上、好ましくは粒径１．０ｍｍ以上のスラグ粒子の割合が７０mass％以上の高炉水砕スラグからなる水中の環境改善用資材。
【００８１】
本発明の水中の環境改善方法の具体的な実施形態としては、以上説明した形態、すなわち青潮防止法（覆砂）、養浜又は干潟・浅場の造成法、磯焼け海域の藻場造成法、磯焼け防止法、赤潮防止法以外にも、例えば、磯焼け以外の原因で海藻成育環境が衰退・消失した海域の環境改善法（修復）等などがある。
このような環境改善法においても、使用される高炉水砕スラグの組成や性状、高炉水砕スラグの敷設形態、高炉水砕スラグからのケイ酸塩イオンの溶出機構、その他の高炉水砕スラグの機能などは、先に磯焼け海域の藻場造成法や磯焼け防止法に関して述べたものと同様である。
【００８２】
以上述べた本発明の（Ａ）、（Ｃ）、（Ｄ）の各実施形態は、海岸に面した所謂浅場の造成又は修復を兼ねて行ってもよい。すなわち、主に海岸に面した海域において海藻類や魚介類の成育・棲息に適した所謂浅場が海砂の流失や浚渫などにより衰退・消失する場合があり、このような海底部を本来の浅場としての環境に造成又は修復することを兼ねて、その海底部に覆砂材等として高炉水砕スラグを敷設することができる。
またこの場合、海流等による高炉水砕スラグの流失を防止するため、敷設された高炉水砕スラグの周囲に潜堤を設置することが好ましい。また、高炉水砕スラグの敷設領域には人工の海藻着生基盤や漁礁を設置し、海藻類や魚介類の成育・棲息環境を整えることが好ましい。
【００８３】
高炉水砕スラグの流失を防止するための潜堤は任意の材料で構成することができるが、塊状スラグ（鉄鋼製造プロセスで発生した塊状スラグ）を積み上げて潜堤を構築することにより、例えばコンクリート製品を用いたり、コンクリート構造物を構築したりすることなく、簡易且つ安価に潜堤を形成することができる。高炉水砕スラグが元々粒状の形態であるのに対して、製鋼スラグ等は塊状のものが得られやすく且つ比重も大きいため、これを所定の高さに積み上げることにより堅牢な潜堤を構築することができ、しかもスラグが塊状であるため海流等により消失する恐れもない。また、製鋼スラグには底質や水質を浄化する作用もあるため、水中の環境改善にも寄与できるという利点がある。
【００８４】
使用する塊状スラグとしては、高炉で発生する高炉徐冷スラグ（但し、この高炉徐冷スラグは水中でＳが溶出しないようにするため、十分にエージング処理したものが好ましい）、予備処理、転炉、鋳造等の工程で発生する脱炭スラグ、脱燐スラグ、脱硫スラグ、脱珪スラグ、鋳造スラグ等の製鋼スラグ、鉱石還元スラグ、電気炉スラグ等が挙げられ、これらの２種以上を用いてもよい。またこれらのスラグなかでも、高比重であるという点では脱炭スラグ、鋳造スラグが特に好ましい。またスラグの大きさとしては、一般に塊径が３０ｍｍ程度以上のものが好ましい。
また、上記潜堤は後述するようなスラグを主原料とするブロック、すなわち、鉄鋼製造プロセスで発生したスラグを主原料とする粉粒状原料を炭酸反応で生成させたＣａＣＯ_３を主たるバインダーとして固結させて得られたブロック、鉄鋼製造プロセスで発生したスラグを主原料とする水和硬化体ブロックなどで構成することもできる。これらのブロックを適当に積み上げることにより、堅牢な潜堤を構築することができる。これらと上記塊状スラグを併用してもよい。
【００８５】
高炉水砕スラグの敷設領域に設置される人工の海藻着生基盤や漁礁は、自然石、ブロック、鋼製構造体等の任意のもので構成することができるが、特に、上述したような鉄鋼製造プロセスで発生した塊状スラグ、鉄鋼製造プロセスで発生したスラグ（鉄鋼スラグ）を主原料とする粉粒状の原料を炭酸固化させて得られたブロック、或いは同じく鉄鋼スラグを主原料とする水和硬化体ブロックなどを用いるのが好ましい。
【００８６】
これらのうち鉄鋼製造プロセスで発生した塊状スラグについては、先に述べた通りである。
また、主原料である鉄鋼スラグを炭酸固化させて得られたブロックとしては、例えば特許第３１７５６９４号で提案されている、鉄鋼スラグを主原料とする粉粒状原料を炭酸化反応で生成させたＣａＣＯ_３（場合によっては、さらにＭｇＣＯ_３）を主たるバインダーとして固結させ、塊状させたものを用いることができる。また、鉄鋼スラグとしては、先に挙げたような各種スラグ、すなわち高炉で発生する高炉水砕スラグや高炉徐冷スラグ、予備処理、転炉、鋳造等の工程で発生する脱炭スラグ、脱燐スラグ、脱硫スラグ、脱珪スラグ、鋳造スラグ等の製鋼スラグ、鉱石還元スラグ、電気炉スラグ等を用いることができる。
【００８７】
このような鉄鋼スラグを炭酸固化させて得られたブロック（石材）は、▲１▼スラグ中に含まれるＣａＯ（またはＣａＯから生成したＣａ（ＯＨ）_２）の大部分がＣａＣＯ_３に変化するため、ＣａＯによる海水のｐＨ上昇を防止できる、▲２▼スラグに適量の鉄分（特に、金属鉄、含金属鉄材）が含まれることにより、この鉄分が海水中に溶出することで海水中に栄養塩として鉄分が補給され、これが海藻類の育成に有効に作用する、▲３▼スラグを炭酸固化して得られたブロックは全体（表面及び内部）がポーラスな性状を有しており、このため石材表面に海藻類が付着し易く、しかも石材内部もポーラス状であるため、石材中に含まれている海藻類の成育促進に有効な成分（例えば、ケイ酸塩イオンや鉄分）が海水中に溶出しやすい、などにより海藻の着生基盤や漁礁として有効に機能する。また、主原料であるスラグの一部又は全部として高炉水砕スラグを用いることにより、上述したようなケイ酸塩イオンの溶出を特に促進することができるため、海藻成育環境の改善や磯焼け防止、赤潮防止などに特に有効である。このためブロックの全原料又は主原料を高炉水砕スラグとすることが最も好ましい。
【００８８】
また、鉄鋼スラグを主原料とする水和硬化ブロックは、鉄鋼スラグを主原料（骨材及び／又は結合材）として含む原料を水和硬化させて得られるものであり、鉄鋼スラグとしては、先に挙げたような各種スラグ、すなわち高炉で発生する高炉水砕スラグや高炉徐冷スラグ、予備処理、転炉、鋳造等の工程で発生する脱炭スラグ、脱燐スラグ、脱硫スラグ、脱珪スラグ、鋳造スラグ等の製鋼スラグ、鉱石還元スラグ、電気炉スラグ等を用いることができる。水和硬化によるブロックの製造では、原料を水と混練後、型枠に入れ、通常１〜４週間養生することによってブロックが製造される。
【００８９】
また、主原料（骨材及び／又は結合材）であるスラグの一部又は全部として高炉水砕スラグを用いることにより、上述したようなケイ酸塩イオンの溶出を特に促進することができるため、海藻成育環境の改善や磯焼け防止、赤潮防止などに特に有効である。このためブロックの全原料又は主原料を高炉水砕スラグとすることが最も好ましい。
なお、ブロックに用いる結合材としては、上述した高炉水砕スラグの微粉末などの他にシリカ含有物質（例えば、粘土、フライアッシュ、ケイ砂、シリカゲル、シリカシューム）、セメント、消石灰、ＮａＯＨなどを適宜組み合わせて使用することもできる。
【００９０】
以上のようなブロックを高炉水砕スラグの敷設領域に設置する場合には、個々のブロックを高炉水砕スラグ層上に設置してもよいし、複数のブロックを積み上げ或いは組み付けてもよい。特に、ブロックに漁礁としての機能を持たせる場合には、複数のブロックを積み上げ或いは組み付けることにより、複数のブロック間に魚介類が棲息できるような空間部を形成することが好ましい。
また、塊状スラグを高炉水砕スラグの敷設領域に設置する場合には、例えばスラグを山状に積み上げたり、或いはスラグを金網籠など入れて設置するなど、任意の設置形態を採ることができる。
【００９１】
以上述べたような高炉水砕スラグを敷設材とする浅場の造成又は修復において、高炉水砕スラグの流出防止用の潜堤として塊状スラグ及び／又はスラグ（特に好ましくは高炉水砕スラグ）を主原料とするブロックを用い、且つ高炉水砕スラグの敷設領域に設置する海藻着生基盤や漁礁としても、塊状スラグ及び／又はスラグ（特に好ましくは高炉水砕スラグ）を主原料とするブロックを用いることにより、先に述べたようなスラグによる水中の環境改善作用（すなわち、珪藻類の増殖による海藻類成育環境の改善作用や磯焼け・赤潮の発生抑制作用、硫化水素の発生防止による青潮の発生抑制作用、底質・水質の浄化作用など）が最も効果的に得られ、しかも浅場の造成又は修復用の資材として天然資源を用いることなく、１００％リサイクル材（鉄鋼スラグ）を用いることができ、リサイクル材の有効利用、施工の低コスト化、天然資源の利用による環境破壊の防止などの面からも極めて有利である。
【００９２】
図５は、高炉水砕スラグを敷設材とする浅場の造成又は修復の一実施形態を示したもので、４は水底に適当な厚さに敷設された高炉水砕スラグ、５は敷設された高炉水砕スラグの流失を防止するために高炉水砕スラグ４の周囲に設置された潜堤であり、この潜堤５は塊状スラグ（製鋼スラグ）を積み上げることにより構築されている。さらに、６は敷設された高炉水砕スラグ層上に積み上げられることにより海藻着生基盤及び／又は漁礁を構成するブロックであり、このブロック６としては、鉄鋼スラグ（好ましくは高炉水砕スラグ）を主原料とする粉粒状原料を炭酸固化させて得られたブロック、或いは同じく鉄鋼スラグ（好ましくは高炉水砕スラグ）を主原料とする水和硬化体ブロックなどを用いる。
【００９３】
このように高炉水砕スラグ４を海底に敷設するとともに、その流失防止用の潜堤５として塊状スラグを用い、さらに高炉水砕スラグ４の敷設領域に鉄鋼スラグ（好ましくは高炉水砕スラグ）で構成されたブロック６を海藻着生基盤及び／又は漁礁として設置することにより、海藻類や魚介類の成育・棲息環境に最も適した浅場が造成又は修復されることになる。
なお、以上述べた浅場の造成又は修復においても、使用される高炉水砕スラグの組成や性状、高炉水砕スラグの敷設形態、高炉水砕スラグからのケイ酸塩イオンの溶出機構、その他の高炉水砕スラグの機能などは、先に磯焼け海域の藻場造成法や磯焼け防止法に関して述べたものと同様である。
【００９４】
以上のようなスラグ流失防止用の潜堤を設ける場合の好ましい実施形態を整理すると以下のようになる。
（１） 海岸に面した海底に、粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上、好ましくは粒径１．０ｍｍ以上のスラグ粒子の割合が７０mass％以上の高炉水砕スラグを敷設するとともに、該高炉水砕スラグの敷設領域の周囲にスラグ流失防止用の潜堤を設置し、且つ該高炉水砕スラグの敷設領域には人工の海藻着生基盤及び／又は漁礁を設置する水中の環境改善方法。
（２） 上記（１）の環境改善方法において、潜堤の少なくとも一部を、鉄鋼製造プロセスで発生した塊状のスラグ、鉄鋼製造プロセスで発生したスラグを主原料とする粉粒状原料を炭酸反応で生成させたＣａＣＯ_３を主たるバインダーとして固結させて得られたブロック、鉄鋼製造プロセスで発生したスラグを主原料とする水和硬化体ブロックの中から選ばれる１種以上で構成する水中の環境改善方法。
（３） 上記（１）又（２）の環境改善方法において、人工の海藻着生基盤及び／又は漁礁の少なくとも一部を、鉄鋼製造プロセスで発生した塊状のスラグ、鉄鋼製造プロセスで発生したスラグを主原料とする粉粒状原料を炭酸反応で生成させたＣａＣＯ_３を主たるバインダーとして固結させて得られたブロック、鉄鋼製造プロセスで発生したスラグを主原料とする水和硬化体ブロックの中から選ばれる１種以上で構成する水中の環境改善方法。
【００９５】
【実施例】
［実施例１］
水深４ｍのヘドロが堆積した海底において、篩い分けして得られた粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上の高炉水砕スラグを３０ｃｍの厚さで１０ｍ×１０ｍの範囲に敷設した（本発明例）。また、比較例として、隣接する同様の条件の海底部に、篩い分けして得られた粒径０．５ｍｍ以上のスラグ粒子の割合が８５mass％の高炉水砕スラグを同様の条件で敷設した。なお、このヘドロが堆積した海底部には少量のゴカイ類のみが棲息していた。
【００９６】
敷設から１年経過後に、高炉水砕スラグの敷設層における生物棲息量、敷設層直上水と周囲のヘドロ層直上水の溶存酸素量と硫化水素量の調査を行った。その結果、本発明例、比較例とも高炉水砕スラグの敷設層中には貝類やゴカイ類等の多様な底棲生物が棲息していたが、生物棲息量は湿重量で本発明例が６３７ｇ／ｍ^２、比較例が５０３ｇ／ｍ^２であり、本発明例の生物棲息量は比較例に較べて約２０％多かった。また、溶存酸素量については、ヘドロ直上水の溶存酸素量が１．２ｐｐｍであったのに対して、敷設層直上水の溶存酸素量は本発明例、比較例ともに６ｐｐｍであった。また、硫化水素量については、ヘドロ直上水では０．０２ｐｐｍの硫化水素が検出されたのに対して、本発明例、比較例の敷設層直上水ではともに硫化水素は検出されなかった。
【００９７】
［実施例２］
水深５ｍのヘドロが堆積した海底から砂浜となる海岸までの領域において、篩い分けして得られた粒径１．０ｍｍ以上のスラグ粒子の割合が８０mass％以上の高炉水砕スラグを５０ｃｍ〜２ｍの厚さで２０ｍ×６０ｍの範囲に敷設した（本発明例）。また、比較例として、隣接する同様の条件の海底部に、篩い分けして得られた粒径０．５ｍｍ以上のスラグ粒子の割合が８０mass％の高炉水砕スラグを同様の条件で敷設した。なお、ヘドロが堆積した海底部には少量のゴカイ類のみが棲息していた。
【００９８】
敷設から１年経過後に、高炉水砕スラグの敷設層における生物棲息量、敷設層直上水と周囲のヘドロ層直上水の溶存酸素量と硫化水素量、敷設層中の間隙水のｐＨの調査を行った。その結果、本発明例、比較例とも高炉水砕スラグの敷設層中には貝類やゴカイ類等の多様な底棲生物が棲息していたが、生物棲息量は湿重量で本発明例が７８６ｇ／ｍ^２、比較例が４７２ｇ／ｍ^２であり、本発明例の生物棲息量は比較例に較べて約４０％多かった。また、溶存酸素量については、ヘドロ直上水の溶存酸素量が０．５ｐｐｍであったのに対して、水深２ｍの敷設層直上水の溶存酸素は本発明例、比較例ともに７ｐｐｍであった。また、硫化水素量については、ヘドロ直上水では０．０５ｐｐｍの硫化水素が検出されたのに対して、本発明例、比較例の敷設層直上水ではともに硫化水素は検出されなかった。また、水深２ｍ、スラグ敷設厚さ２ｍの地点におけるスラグ敷設層上面から深さ０．５ｍでの間隙水のｐＨは、本発明例では８．５であり、硫酸還元菌の活動を抑えられるレベルであった。また、比較例では間隙水のｐＨは、本発明例よりも高い８．７であった。
【００９９】
［実施例３］
・発明例(1)
図６に示すように磯焼けした岩礁性の海底の凹部に、篩い分けして得られた粒径０．５ｍｍ以上のスラグ粒子の割合が９５mass％以上の高炉水砕スラグを２０ｃｍ厚さで１０ｍ×１０ｍの範囲に設置した。その後、この付近の海底部での珪藻類及び大型海藻類の着生の調査を継続して行った。その結果、スラグ設置１週後には、スラグ設置場所近傍の岩礁に付着珪藻が観察され、スラグ設置１ヶ月後にはスラグ設置場所から海流の下流側３０ｍまで付着珪藻が観察された。また、大型の海藻類は、スラグ設置１ヶ月後にスラグ設置場所の近傍に観察され、スラグ設置６ヶ月後には海流の下流側２０ｍの範囲で観察された。また、長期の観察では、５年経過した後も６ヶ月後と同様に珪藻類と大型の海藻類が観察された。特に大型の海藻類はその種類も増加した。
【０１００】
・発明例(2)
砂質の海底で、その周囲２０ｍの岩礁性海底部が磯焼け状態となっている海域において、図７に示すように砂質部に、篩い分けして得られた粒径１．０ｍｍ以上のスラグ粒子の割合が８５mass％以上の高炉水砕スラグを５０ｃｍの厚さで３０ｍ×３０ｍの範囲に設置した。さらに、その上に製鋼スラグ硬化体及び製鋼スラグを設置し、人工の岩礁を作った。その後、この付近の海底部での付着珪藻及び大型海藻類の着生の調査を継続して行った。その結果、スラグ設置１週間後には、スラグ設置場所の人工岩礁に付着珪藻が観察され、スラグ設置１ヶ月後にはスラグ設置場所から２０ｍ離れた岩礁においても付着珪藻が観察された。また、大型の海藻類については、スラグ設置１ヶ月後にスラグ設置場所の人工岩礁に観察され、スラグ設置６ヶ月後には設置場所から２０ｍ離れた岩礁においても観察された。長期の観察では、５年経過した後も６ヶ月後と同様に人工岩礁と天然岩礁の双方に珪藻類と大型海藻類が観察された。特に大型の海藻類はその種類も増加した。
【０１０１】
［実施例４］
沿岸から沖合５００ｍ〜１ｋｍの赤潮多発海域（湾内）において、海岸近くの海底に、篩い分けして得られた粒径０．５ｍｍ以上のスラグ粒子の割合が９５mass％以上の高炉水砕スラグを略３０ｃｍの厚さに敷設した。その敷設範囲は海岸線から沖合に４０ｍ（水深２〜７ｍ）までの範囲であって、海岸線の総延長２００ｍの範囲とした。
高炉水砕スラグの設置後（設置時期は夏期）、その設置場所と旧来の赤潮発生ポイント（海域）の表層海水中のケイ酸塩濃度と珪藻量とを継続的に調査した。その結果を表２に示す。これによれば、高炉水砕スラグの設置２週間後には、その設置場所と旧来の赤潮発生ポイントでの表層海水中のケイ酸塩濃度が増加しており、元々ケイ酸塩濃度の低かった赤潮発生ポイントでも珪藻量が増加していた。また、高炉水砕スラグの設置後３年間調査を継続したが、この間赤潮の発生は全く認められず、また高炉水砕スラグの設置場所では海藻や魚介類も多数観察された。
【０１０２】
【表２】

【０１０３】
［実施例５］
・発明例(1)
湾内の平坦な水底（砂質上に泥質が堆積した水底）に形成された直径が約３０ｍの凹部（深掘り部分）に、篩い分けして得られた粒径１．０ｍｍ以上のスラグ粒子の割合が９０mass％以上の高炉水砕スラグを凹部周囲の水底面との平均高低差が１ｍ以下（［ｄ_１−ｄ_０］≦１ｍ）となるように敷設した。敷設厚みは約１５ｍであった。
この敷設材の敷設による水中の懸濁の度合いを調べるため、凹部の中心部の直上水深５ｍ地点において、上記敷設材の敷設直前の懸濁物質量と敷設材の敷設直後（３０分後）の懸濁物質量をそれぞれ測定し、その差を求めた。
また、敷設材の敷設後、３年にわたって半年毎に敷設部水底面の直上、敷設部から５０ｍ離れた地点での水底面の直上及び敷設部から１００ｍ離れた地点での水底面の直上の各位置で水の硫化水素濃度を測定した。また、敷設してから３年後の敷設材上面レベル（水底面）の沈下量（平均値）を測定した。それらの結果を表３に示す。
【０１０４】
・発明例(2)
湾内の平坦な水底（砂質上に泥質が堆積した水底）に形成された直径が約２０ｍの凹部（深掘り部分）に、篩い分けして得られた粒径１．０ｍｍ以上のスラグ粒子の割合が８５mass％以上の高炉水砕スラグ６０mass％、高炉徐冷スラグ１０mass％、製鋼スラグ２０mass％、都市ゴミスラグ１０mass％の混合物を凹部周囲の水底面との平均高低差が１ｍ以下（［ｄ_１−ｄ_０］≦１ｍ）となるように敷設した。敷設厚みは約１０ｍであった。
この敷設材の敷設による水中の懸濁の度合いを調べるため、凹部の中心部の直上水深５ｍ地点において、上記敷設材の敷設直前の懸濁物質量と敷設材の敷設直後（３０分後）の懸濁物質量をそれぞれ測定し、その差を求めた。
また、敷設材の敷設後、３年にわたって半年毎に敷設部水底面の直上、敷設部から５０ｍ離れた地点での水底面の直上及び敷設部から１００ｍ離れた地点での水底面の直上の各位置で水の硫化水素濃度を測定した。また、敷設してから３年後の敷設材上面レベル（水底面）の沈下量（平均値）を測定した。それらの結果を表３に示す。
【０１０５】
・発明例(3)
湾内の平坦な水底であって、砂質上に泥質が堆積した水底の５０ｍ×５０ｍの範囲に、篩い分けして得られた粒径０．５ｍｍ以上のスラグ粒子の割合が９０mass％以上の高炉水砕スラグ９０mass％、製鋼スラグ１０mass％の混合物を厚さ５０ｃｍに敷設した。
この敷設材の敷設による水中の懸濁の度合いを調べるため、敷設領域の中心部の直上水深５ｍ地点において、上記敷設材の敷設直前の懸濁物質量と敷設材の敷設直後（３０分後）の懸濁物質量をそれぞれ測定し、その差を求めた。
また、敷設材の敷設後、３年にわたって半年毎に敷設部水底面の直上、敷設部から５０ｍ離れた地点での水底面の直上及び敷設部から１００ｍ離れた地点での水底面の直上の各位置で水の硫化水素濃度を測定した。それらの結果を表３に示す。
【０１０６】
・比較例(1)
湾内の平坦な水底（砂質上に泥質が堆積した水底）に形成された直径が約４０ｍの凹部（深掘り部分）に、海砂を凹部周囲の水底面との平均高低差が１ｍ以下（［ｄ_１−ｄ_０］≦１ｍ）となるように敷設した。敷設厚みは約８ｍであった。
この敷設材の敷設による水中の懸濁の度合いを調べるため、凹部の中心部の直上水深５ｍ地点において、上記敷設材の敷設直前の懸濁物質量と敷設材の敷設直後（３０分後）の懸濁物質量をそれぞれ測定し、その差を求めた。
また、敷設材の敷設後、３年にわたって半年毎に敷設部水底面の直上、敷設部から５０ｍ離れた地点での水底面の直上及び敷設部から１００ｍ離れた地点での水底面の直上の各位置で水の硫化水素濃度を測定した。また、敷設してから３年後の敷設材上面レベル（水底面）の沈下量（平均値）を測定した。それらの結果を表３に示す。
【０１０７】
・比較例(2)
湾内の平坦な水底（砂質上に泥質が堆積した水底）に形成された直径が約３０ｍ、深さ１０ｍの凹部（深掘り部分）について、発明例１における敷設材の敷設時とほぼ同時期から３年にわたって半年毎に深掘部水底面の直上、深掘部から５０ｍ離れた地点での水底面の直上及び深掘部から１００ｍ離れた地点での水底面の直上の各位置で水の硫化水素濃度を測定した。その結果を表３に示す。
【０１０８】
【表３】

【０１０９】
［実施例６］
底層水の溶存酸素濃度が約２ｐｐｍ（飽和溶解度：約７ｐｐｍ）となっている水域（約４００ｍ四方の水域）の海底に、篩い分けして得られた粒径１．０ｍｍ以上のスラグ粒子の割合が８５mass％以上の高炉水砕スラグを厚さ約２０ｃｍに敷設した。１ヶ月経過後に、スラグ敷設水域の底層水の溶存酸素濃度を測定したところ約４.５ｐｐｍに上昇していた。
［実施例７］
底層水の硫化水素濃度が０．５〜１．２ｐｐｍとなっている水域（約１ｈａ）の海底に、篩い分けして得られた粒径１．０ｍｍ以上のスラグ粒子の割合が９０mass％以上の高炉水砕スラグを厚さ約３５ｃｍに敷設した。１ヶ月経過後、６ヶ月経過後、１年経過後にそれぞれスラグ敷設水域の底層水の硫化水素濃度を測定（測定方法：検知管式、検出限界：０．０１ｐｐｍ）したが、硫化水素は検出されなかった。
【０１１０】
［実施例８］
底層水の流速が３ｃｍ／秒の水域（約１．５ｈａ）の海底に、篩い分けして得られた粒径０．５ｍｍ以上のスラグ粒子の割合が９５mass％以上の高炉水砕スラグを厚さ約３ｍに敷設した。このスラグ敷設前とスラグを敷設してから３ヶ月経過後の底層水の水質を比較したところ、スラグ敷設前は硫化水素濃度が１．８ｐｐｍ、溶存酸素濃度が０．２ｐｐｍであったのに対し、スラグを敷設してから３ヶ月経過後では硫化水素濃度が検出限界以下に、溶存酸素濃度が４．８ｐｐｍにそれぞれ改善された。
【０１１１】
［実施例９］
海水塩分濃度による密度躍層（表層水の塩分濃度：１．５％、底層水の塩分濃度：２．６％）が形成された水域（約１０ｈａ）の海底に、篩い分けして得られた粒径１．０ｍｍ以上のスラグ粒子の割合が９５mass％以上の高炉水砕スラグを厚さ約０．２ｍに敷設した。このスラグ敷設前とスラグを敷設してから３ヶ月経過後の底層水の水質を比較したところ、スラグ敷設前は硫化水素濃度が３ｐｐｍ、溶存酸素濃度が０．１ｐｐｍであったのに対し、スラグを敷設してから３ヶ月経過後では硫化水素濃度が検出限界以下に、溶存酸素濃度が４ｐｐｍにそれぞれ改善され、また、高炉水砕スラグの敷設により水底が浅くなったため、底層水の塩分濃度も２．３％まで低下した。
【０１１２】
［実施例１０］
海水温による密度躍層（表層水の水温：２４℃、底層水の水温：１４℃）が形成された水域（約０．５ｈａ）の海底に、篩い分けして得られた粒径１．０ｍｍ以上のスラグ粒子の割合が９０mass％以上の高炉水砕スラグを厚さ約３ｍに敷設した。このスラグ敷設前とスラグを敷設してから６ヶ月経過後の底層水の水質を比較したところ、スラグ敷設前は硫化水素濃度が０．８ｐｐｍ、溶存酸素濃度が０．３ｐｐｍであったのに対し、スラグを敷設してから６ヶ月経過後では硫化水素濃度が検出限界以下に、溶存酸素濃度が３ｐｐｍにそれぞれ改善され、また、高炉水砕スラグの敷設により水底が浅くなったため、底層水の水温も１６℃まで上昇した。
【０１１３】
【発明の効果】
以上述べたように本発明の水中の環境改善方法によれば、安価で且つ大量に入手できる所定の粒度構成を有する高炉水砕スラグを水中に設置するだけで、水底や水浜における好ましい環境、特に覆砂、養浜、浅場や干潟の造成等において砂地に棲息する生物に好適な環境を形成することができる。また、青潮の発生防止、磯焼けの防止、赤潮の発生防止、或いは藻場の造成や海藻成育環境の修復などにも優れた効果を発揮できる。
【図面の簡単な説明】
【図１】生成ままの高炉水砕スラグの代表的な粒度構成（篩い通過重量）を示すグラフ
【図２】従来法において水底の凹部に敷設した敷設材の作用を示す説明図
【図３】本発明の実施形態において水底の凹部に敷設した敷設材の作用を示す説明図
【図４】本発明による水中の環境改善方法の一実施形態を示す説明図
【図５】本発明による水中の環境改善方法の実施形態において、造成された浅場を示す説明図
【図６】実施例３における磯焼け海域の藻場造成の実施状況を示す説明図
【図７】実施例３における磯焼け海域の藻場造成の他の実施状況を示す説明図説明図
【符号の説明】
Ａ…高炉水砕スラグ、１，１′…凹部、２…敷設材、３…ケーソン、４…高炉水砕スラグ、５…潜堤、６…ブロック、２０…スラグ、２０ａ…高炉水砕スラグ、２０ｂ…高炉水砕スラグ以外のスラグ、２１…スラグ以外の素材、Ｘ，Ｙ…水底面[0001]
[Technical field to which the invention belongs]
The present invention relates to an environment improvement technique for underwater or water beaches, and in particular, to an environment improvement method suitable for providing a favorable environment for living habitat in the formation of sand cover, beach nourishment, shallow fields and tidal flats. It relates to the materials used.
[0002]
[Prior art]
In recent years, in harbors and other coastal sea areas, sediment and water pollution due to sludge formation of sediments, shallow areas and sandy beaches due to sea sand collection and runoff have become problems. In particular, measures to prevent the occurrence of blue tides and red tides caused directly or indirectly by sediment and water pollution, the growth of seaweeds and aquatic organisms, and the decline and disappearance of habitats are major issues. Development of marine environment improvement technology that can solve this problem is desired.
[0003]
Conventionally, measures such as covering the sea bottom with natural sand (sea sand, mountain sand) may be taken in order to improve sludge bottom sediment. Occasionally sludge is performed.
In addition, when sand is covered with natural sand, it may also be used to create a habitat for seafood that inhabits sandy water bottoms. Sometimes used.
[0004]
However, the use of natural sand or natural stone as a sand-capping material may cause a new environmental destruction due to the collection. In addition, natural sand and natural stone have no chemical bottom sediment / water purification action, that is, no action to remove eutrophic components such as phosphorus eluted from the bottom sediment, or to suppress or remove hydrogen sulfide. Even if the sludge bottom is covered with sand, the purification effect of the bottom and water quality cannot be expected. For this reason, problems such as the occurrence of red tides and blue tides in coastal waters, the habitat of living organisms and seaweeds, and the attenuation and disappearance of growth environments cannot be effectively improved.
[0005]
In recent years, so-called beach nourishment, in which a large amount of sand is thrown into the beach, has been carried out for the purpose of restoring sandy beaches that have disappeared due to coastal erosion or the like, or for the purpose of creating artificial beaches that are marine recreational sites. . In addition, recently, the excellent water purification function of tidal flats and shallow areas is being recognized, and attempts have been made to artificially restore lost tidal flats and shallow areas or to create new ones. And a lot of sand etc. is thrown in for creation. However, when laying materials used for the construction of such beach nourishments, tidal flats, shallow fields, etc. are required for natural sand and natural stone, there is a possibility that new environmental destruction will be caused by the extraction.
[0006]
[Problems to be solved by the invention]
Therefore, the object of the present invention is to solve such problems of the prior art, and use a laying material that can be obtained in a large amount at a low cost other than natural sand and natural stone. Another object of the present invention is to provide an environmental improvement method capable of forming an environment suitable for living organisms living in sandy areas in the formation of shallow fields and tidal flats. Another object of the present invention is to provide an environmental improvement method that is effective in preventing the occurrence of red tides and blue tides, and preventing the decline and disappearance of the seaweed growing environment due to firewood burning. Furthermore, the other object of this invention is to provide the laying material suitable for such an environmental improvement method.
[0007]
[Means for Solving the Problems]
In response to the problems of the prior art as described above, the present inventors have examined a laying material suitable for the construction of sand-covered sand, beach nourishment, tidal flats and shallow fields, and as a result, blast furnaces generated in the steel manufacturing process. 1. Granulated slag is (1) close in nature and appearance to natural sand. (2) Unlike natural sand, it has a chemical bottom and water purification action when laid in water. 3) Since it contains a large amount of silicic acid and has high silicate ion elution, it effectively functions as a silicate ion release source effective in preventing the growth of diatoms and seaweeds and red tides, (4) It has been found that it is very suitable as the above-mentioned laying material in that it is inexpensive and can be obtained in large quantities and can be poured in large quantities into a wide water area or beach.
[0008]
Furthermore, the present inventors have examined the optimum conditions for granulated blast furnace slag when applied as laying material to sand cover, beach nourishment, tidal flats, and shallow grounds. In view of the particle form, it has been found that it is particularly effective to use granulated blast furnace slag having a specific particle size configuration.
The present invention has been made on the basis of the above findings, and the features thereof are as follows.
[0009]
(1) A method for improving the environment of underwater or beaches, characterized in that blast furnace granulated slag having a ratio of slag particles having a particle size of 0.5 mm or more is 90 mass% or more is laid on the bottom or beach.
(2) A method for improving the environment of an underwater or beach, characterized by laying granulated blast furnace slag having a particle size of 1.0 mm or more in a ratio of 70 mass% or more on the bottom of a water or on a beach.
(3) The ratio of slag particles having a particle size of 1.0 mm or more is 80 mass A method for improving the environment of underwater or beaches, characterized by laying ground granulated blast furnace slag at a water bottom or beach.
(Four)  the above (1) ~ (3) Any ofIn the environmental improvement method, ground granulated blast furnace slag is used as a sand bottom, water nourishing material, shallow ground material, tidal flat material, seaweed ground material, drought prevention material, red tide prevention material or blue tide prevention material. A method for improving the environment of underwater or a water beach characterized by laying on the beach.
[0010]
(Five)  Above (1) ~(Four)In any one of the above-mentioned environmental improvement methods, the blast furnace granulated slag laid in the bottom of the water or on the beach serves as a silicate ion release source.
(6)  It is a material laid on the bottom of the water or on the beach as a sand-covering material, beach nourishing material, shallow ground material, tidal flat material, seaweed ground material, drought burning prevention material, red tide prevention material or blue tide prevention material. A material for improving the environment of underwater or beaches, characterized by comprising blast furnace granulated slag having a ratio of slag particles of 0.5 mm or more of 90 mass% or more.
(7)  It is a material laid on the bottom of the water or on the beach as a sand-covering material, beach nourishing material, shallow ground material, tidal flat material, seaweed ground material, drought burning prevention material, red tide prevention material or blue tide prevention material. A material for improving the environment of underwater or beaches, characterized by comprising blast furnace granulated slag having a ratio of 1.0 mm or more of slag particles of 70 mass% or more.
(8) It is a material laid on the bottom of the water or on the beach as a sand-covering material, beach nourishing material, shallow ground material, tidal flat material, seaweed ground material, drought burning prevention material, red tide prevention material or blue tide prevention material. The ratio of slag particles of 1.0 mm or more is 80 mass A material for improving the environment of underwater or watery beaches, characterized by comprising blast furnace granulated slag that is at least%.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In the underwater or beach environment improvement method of the present invention, blast furnace granulated slag having a predetermined particle size configuration is laid on the bottom or beach, but the blast furnace granulated slag is used as a material for laying on the bottom or beach. The reason why it is very suitable is as follows.
(1) Granulated blast furnace slag is granular and white, and has a property and appearance close to natural sand, so it can provide an environment suitable for living organisms living in sand.
(2) Blast furnace granulated slag, unlike natural sand, has a chemical bottom and water purification action when laid on the bottom of the water or on the beach.
[0012]
(3) Granulated blast furnace slag contains a large amount of silicic acid and has high silicate ion elution, making it an effective source of silicate ions for preventing the growth of seaweeds, burning of firewood and red tide. Works effectively.
(4) Granulated blast furnace slag is produced in large quantities as a by-product in the steel manufacturing process and is a very inexpensive material, so it can be introduced into water and beaches. It is possible to input to 1 million tons.
The operations (2) and (3) will be described in detail later.
[0013]
The method of the present invention is an environmental improvement method capable of providing a water bottom or beach environment suitable for living organisms (eg, shellfish and shellfish bottom organisms) that inhabit sandy areas. In particular, the present invention can be suitably applied to shallow ground creation, tidal flat creation, and the like. In these cases, blast furnace granulated slag is laid on the bottom of the water or on the beach as sand-capping material, beach nourishing material, shallow-field material, or tidal flat material.
In addition, the method of the present invention is also effective for the formation of seaweed beds, prevention of sea urchin, prevention of red tide, and prevention of blue tides. Or lay on the bottom of the water or beach as a blue tide prevention material.
[0014]
As blast furnace granulated slag, slag as obtained as a by-product in the steel manufacturing process, or slag removed from the ground iron (iron), crushed, crushed before or after removal of the ground iron In the method of the present invention, blast furnace granulated slag having a predetermined particle size configuration is prepared by adjusting the particle size of these slags by sieving or the like.
[0015]
The amount of inhabitants of shellfish and shellfish living in sandy areas such as the seabed, beach, and tidal flats is greatly related to the size of the sand that composes the sandy area, and the relatively coarser sand has more habitat. . This is because many living organisms living in the sandy land enter the sand and inhabit, and therefore, when the sand is rough to some extent and the gap between the sand particles is larger, the living organism is more likely to live. However, if the gap is too large, it will be difficult for small creatures to live, so the gap needs to be moderate in size.
[0016]
The granulated blast furnace slag is originally granular (that is, as-produced) in which the ratio of slag particles having a particle size of 5 mm or less is 90 mass% or more and D50 is about 1 mm to 1.5 mm. In FIG. 1, the typical precision structure (sieve passage weight) of the blast furnace granulated slag as produced | generated is shown. Moreover, this granulated blast furnace slag contains a lot of needle-like materials for reasons of its manufacturing method, and these needle-like materials are sharp so as to be pierced and injured when touched by a person or an organism.
[0017]
The present inventors conducted an experiment to lay blast furnace granulated slag having various particle sizes on the shallow sea floor where sludge was deposited, and to confirm the inhabitants of benthic organisms (shellfish and sandworms) after a certain period of time. went. As a result, the shallow seabed laid with granulated blast furnace slag showed an increase in the inhabited amount of benthic organisms compared to the seabed where sludge was deposited, regardless of its grain size composition. When the blast furnace granulated slag having a particle size composition of 90 mass% or more, particularly a ratio of slag particles of 1.0 mm or more in particle size composition of 70 mass% or more is laid, A significant increase was observed.
[0018]
Moreover, the granulated blast furnace slag is sieved with sieves of 0.49 mm and 1.18 mm, and the ratio of slag particles having a particle size of 0.5 mm or more and the ratio of slag particles having a particle size of 1.0 mm or more The relationship with the content was investigated. The results are shown in Table 1. According to this, when the ratio of slag particles having a particle size of 0.5 mm or more is increased, the ratio of needles is decreased, and particularly when the ratio of slag particles having a particle size of 0.5 mm or more is 90 mass% or more, The content of the needle-like material is about 1/10 of the original (before sieving). In addition, when the ratio of slag particles having a particle size of 1.0 mm or more is 70 mass% or more, the content of the needle-like material is about 1/100 of that at the beginning (before sieving). Accordingly, the particle size constitution of the granulated blast furnace slag is such that the ratio of slag particles having a particle diameter of 0.5 mm or more is 90 mass% or more, preferably the ratio of slag particles having a particle diameter of 1.0 mm or more is 70 mass% or more. It can be set as a highly safe laying material with a small content of the state-like material.
[0019]
[Table 1]

[0020]
In addition, when blast furnace granulated slag containing a large amount of fine particles is laid on the water or on the beach, the fine-grained portion is gradually unevenly distributed in the laying layer, and this unevenly-distributed fine-grained portion may be consolidated. By adopting a relatively coarse particle size configuration as described above, such fine-grained portions are not consolidated.
For the above reasons, in the method of the present invention, a granulated blast furnace slag in which the ratio of slag particles having a particle diameter of 0.5 mm or more is 90 mass% or more, preferably the ratio of slag particles having a particle diameter of 1.0 mm or more is 70 mass% or more. It is laid on the bottom of the water or on the beach. From the results shown in Table 1, etc., the more preferable particle size constitution of the granulated blast furnace slag is such that the ratio of slag particles having a particle size of 1.0 mm or more is 80 mass% or more.
In order to obtain such granulated blast furnace granulated slag, blast furnace granulated slag is usually sieved. The sieving method may be any of dry sieving, wet sieving, air flow separation and the like.
[0021]
Hereinafter, basic embodiments of the method of the present invention will be described.
(A) Laying blast furnace granulated slag for the purpose of preventing the occurrence of blue tide (covering sand)
When seawater stagnation occurs at the bottom of the water in an inner bay, hydrogen sulfide is generated, which causes so-called blue tide.
The major source of hydrogen sulfide is the sludge bottom where water is likely to stagnate, organic matter accumulates, and oxygen consumption is high. Hydrogen sulfide is likely to be generated at the bottom of the water in which a concave portion having a gap is formed. In other words, water stagnates in such a recess, resulting in a marked anoxic state, especially in summer. A large amount of hydrogen sulfide is generated due to the decay of organic matter and the action of bacteria (sulfate-reducing bacteria). Of oxygen-free water mass. Thus, when a large amount of hydrogen sulfide is generated in the recess, not only the organisms in and around the recess are reduced, but the water mass containing hydrogen sulfide flows into the surrounding water area, leading to the generation of so-called blue tide. . In addition, even in the bottom of the water other than the concave portion, in the sludge bottom where the water tends to stagnate and the organic matter accumulates and consumes a large amount of oxygen, hydrogen sulfide is similarly generated and oxygen-free containing hydrogen sulfide. A water mass occurs, causing the death of benthic organisms, and an anoxic water mass flows into the surrounding water area and generates a blue tide.
[0022]
Conventionally, countermeasures such as spraying lime on the bottom of the water (especially in the recesses of the bottom) or covering the bottom with natural sand (sea sand, mountain sand) have been taken. However, as mentioned above, natural sand and natural stone have no chemical bottom sediment / water purification action, so when they are laid on the bottom of the water, for example, in the summer seawater stagnation period and biological activities When the period becomes active, hydrogen sulfide of about several ppm is generated in the pore water by the action of sulfate-reducing bacteria even when sludge is not deposited.
[0023]
On the other hand, the method of spraying lime on the bottom of the water is (1) very expensive, (2) pH control is difficult and the water quality may become high alkali, (3) lime is solidified in a plate at the bottom of the water Therefore, the water in the lower mud is not replaced, so that a larger amount of hydrogen sulfide is generated, and if the hardened lime layer collapses at a certain time, water containing high concentration hydrogen sulfide May flow out to the surroundings. In addition, since it is difficult to fill the concave portion with lime even if lime is sprayed, the concave portion will remain as a result. Therefore, the water in the concave portion is deoxygenated in the summer seawater stagnation period, The phenomenon of large amounts of hydrogen sulfide cannot be fundamentally eliminated.
[0024]
In response to such a problem, the generation of hydrogen sulfide (and eutrophication of seawater) is achieved by laying granulated blast furnace slag having a predetermined particle size structure on the bottom of the water, which is a source of hydrogen sulfide, according to the method of the present invention. The generation of blue tide caused by this can be effectively suppressed. In addition, the blast furnace granulated slag laid on the bottom of the water provides a good habitat for the benthic organisms for the reasons described above, resulting in a significant increase in their habitat.
[0025]
By laying blast furnace granulated slag on the bottom of the water (for example, a recess formed in the bottom of the water) as a hydrogen sulfide generation source according to the method of the present invention, the following effects can be obtained.
 (1) Blast furnace granulated slag has chemical bottom sediment and water purification action. That is, when CaO contained in granulated blast furnace slag is eluted in water, the pH in the water is appropriately increased, and as a result, the activity of sulfate-reducing bacteria that generate hydrogen sulfide is suppressed. CaO and Fe contained in granulated blast furnace slag₂O₃By immobilizing hydrogen sulfide in water, the reduction of hydrogen sulfide in water is achieved. Furthermore, phosphorus in the water is adsorbed and fixed by CaO contained in the granulated blast furnace slag, and eutrophication of water, which is one of the factors such as generation of blue tide, is suppressed. For this reason, when blast furnace granulated slag is laid in a source of hydrogen sulfide such as a recess in the bottom of the water, generation of hydrogen sulfide from the bottom mud is suppressed in that region, and Generation of hydrogen sulfide is also suppressed, and further, a water purification effect is obtained by fixing hydrogen sulfide and phosphorus to the slag particles. In addition, since the upper layer of the laying material is in a state with little hydrogen sulfide and a lot of dissolved oxygen, it becomes an environment inhabited by living organisms and has a high function as a living foundation of living organisms.
[0026]
 (2) Granulated blast furnace slag is obtained by quenching blast furnace slag (molten slag) in a high-temperature molten state with jet water. There are special characteristics. In other words, a general glassy material has a dense structure, whereas in the case of granulated blast furnace slag, the slag in the molten state is rapidly cooled with jet water, which is caused by nitrogen or moisture dissolved in the slag. Since the slag is foamed, the resulting slag particles become a vitreous material having a porous structure having innumerable internal pores and relatively fine particles. For the same reason, the particles of granulated blast furnace slag have an angular shape (a shape having a number of sharp portions on the surface). Due to such morphological features, the aggregate of blast furnace granulated slag has a larger filling gap than the aggregate of granular materials made of general glassy material. In addition, the granulated blast furnace slag used in the present invention is compared. The water permeability is very excellent because of its coarse particle size structure. For this reason, the water in the gaps between the slag particles can be easily replaced, and the dissolved oxygen concentration in the gaps is sufficiently secured, so that a good environment can be provided to the benthic organisms.
[0027]
 (3) When granulated blast furnace slag is laid on the bottom of the water, the activity of sulfate-reducing bacteria is weakened by maintaining the pH in the pore water at about 8.5 by the slight dissolution of Ca from the slag. Generation of hydrogen sulfide by fungi is effectively suppressed, but especially blast furnace granulated slag is glassy as described above, so the content of elution of contained components and components in water or bottom mud compared to other slags The reaction proceeds very slowly. For this reason, the pH in water does not rise rapidly, and the bottom sediment / water quality improving effect does not disappear in a short period of time.
[0028]
 (4) When natural sand or natural stone is laid in a recess in the bottom of the water, which is the source of hydrogen sulfide, a large pressure is applied to the inner wall of the recess, and after a certain period of time has passed, As a result, the upper surface level (bottom surface) of the laying material, which was approximately the same level as the surrounding water bottom surface at the beginning of the laying, sinks greatly, causing water stagnation. There is a problem that a concave portion is formed again.
On the other hand, granulated blast furnace slag has a considerably larger internal friction angle than natural sand and natural stone, so when blast furnace granulated slag is laid in a recess in the bottom of the water, the pressure acting on the inner wall of the recess from the laying material is compared. Small. For this reason, unlike the case where natural sand or natural stone is used, the laying material hardly spreads the inner wall of the recess and spreads in the horizontal direction, and the laying material is less likely to sink at the upper surface level (water bottom surface). In particular, the granulated blast furnace slag has a larger internal friction angle than other slags, and therefore the pressure on the inner wall of the recess is small, and the bulk density is also small compared to other slags. Therefore, settlement of the upper surface level (water bottom surface) of the laying material can be minimized.
[0029]
This will be described with reference to FIGS. FIG. 2 shows a conventional method using natural sand or natural stone as a laying material, and FIG. 3 shows the method of the present invention using blast furnace granulated slag as a laying material. First, when natural sand or natural stone is laid in the concave portion 1 at the bottom of the water as in the conventional method (FIG. 2 (a)), a large pressure F by the laying material 2 acts on the inner wall of the concave portion 1, and a certain period of time after laying. If it passes too much, as shown in FIG.2 (b), the laying material 2 will spread the inner wall of the recessed part 1, and will spread in a horizontal direction. As a result, the bottom surface X of the laying material, which was at the same level as the surrounding bottom surface Y at the beginning of the laying, sinks, thereby forming the recess 1 'again. On the other hand, when blast furnace granulated slag is laid in the recess 1 at the bottom of the water (Fig. 3 (a)), the granulated blast furnace slag has a considerably larger internal friction angle than natural sand or natural stone, so The pressure F acting on the inner wall of 1 is small. For this reason, as shown in FIG. 3B, the laying material 2 hardly spreads the inner wall of the recess 1 and spreads in the horizontal direction, and the water bottom surface X of the laying material 2 is less likely to sink.
[0030]
 (5) When laying material is laid on the bottom of the water, the laying material is transported to the place of laying by ship and thrown into the bottom of the water where hydrogen sulfide is generated, either directly from the ship or via a chute. At this time, there is a problem that the mud and the sludge accumulated in the bottom of the water are rolled up in the water and a large amount of floating mud is generated, and the water quality and the bottom of the surrounding water area are polluted by the floating mud. Here, the granulated blast furnace slag contains a relatively large amount of unreacted Ca. Therefore, unreacted Ca is also present on the surface of each slag particle. For this reason, when blast furnace granulated slag is thrown into the bottom of the ship as a laying material, the mud and the sludge that form the bottom of the water are rolled up into the water, generating a large amount of floating mud, but the mud falls to the bottom of the water. It is aggregated and captured by Ca groups present on the surface of the slag, and settles on the bottom of the water together with the slag. In particular, since slag has a greater true specific gravity than natural sand, natural stone, etc., slag that aggregates and traps floating mud quickly settles on the bottom of the water. As a result, the generation of floating mud accompanying the introduction of the laying material to the bottom of the water and the contamination of the water quality and the bottom of the surrounding water area by this floating mud can be prevented appropriately.
[0031]
In the present embodiment, the water bottom that is the target for laying blast furnace granulated slag is a water bottom that may or may be a hydrogen sulfide generation source, specifically, (1) formed on the water bottom. Recess, (2) Water bottom where hydrogen sulfide was detected in bottom water or bottom of water where the dissolved oxygen concentration in bottom water is below a predetermined value, (3) Bottom of water where the flow rate of bottom water is below a predetermined value, (4) Any one of the bottoms of the water area in which the density climax is formed by the water temperature or / and the salt concentration in the water is a target. In addition, the water area to be applied may be any of seas including harbors, rivers, estuaries, lakes, and the like.
[0032]
In this embodiment, the concave portion of the bottom of the water to be laid with the granulated blast furnace slag is usually a hole-shaped or groove-shaped concave portion artificially formed in the bottom of the water by collecting sand or dredging, but is not limited thereto. For example, it was artificially formed by installing caisson etc. on the bottom of the water where the concave part of the water bottom formed naturally, or the bottom of the slope where the earth and sand collection and the original topography formed the inclined surface or the shallow concave part Recesses and the like are also targeted. In general, the water bottom where the concave portion is formed is muddy or sandy. Such a recess formed in the bottom of the water tends to be a source of hydrogen sulfide because water tends to stagnate and sludge tends to accumulate.
In addition, as a definition of a recessed part, when the stagnation of water etc. are considered, generally the bottom part which is 2 m or more deeper than the surrounding water bottom may be used as the recessed part. Moreover, depending on the case, the water bottom part which is 1 m or more deeper than the surrounding water bottom, or the water bottom part which is 0.5 m or more deeper may be used as the recess.
[0033]
Here, although there is no special restriction | limiting in the kind and scale of a recessed part to be applied, There exist the following as a typical form.
 (a) Naturally existing bottom of water bottom: Such a bottom of water bottom has a relatively large area. In general, the concave portion that is the object of the method of the present invention of this type is a concave portion having a scale such that the width of the narrowest portion in a plan view is 50 m or more and the depth is 2 m or more.
 (b) Recesses artificially formed on the bottom of the water by collecting sand, dredging, etc .: The bottom of such a bottom of the water has a relatively small area. In general, the concave portion which is the object of the method of the present invention of this kind is a concave portion having such a scale that the width of the narrowest portion in plan view is 10 m or more and the depth is 5 m or more.
 (c) In the place where a structure such as caisson is installed at the bottom of the water, this structure and the bottom of the water (for example, a concave portion of a naturally existing bottom, an inclined surface or a shallow concave portion is formed by sediment collection or original topography. Recesses formed as a result of the bottom of the water): The recesses of such a bottom also have a relatively small area. In general, the concave portion which is the object of the method of the present invention of this type is a concave portion of such a scale that the width of the narrowest portion in plan view is 10 m or more and the depth is 2 m or more.
[0034]
There is no particular limitation on the laying form of the laying material (blast furnace granulated slag) in the recess, but the bottom surface formed by the top surface of the laying material laid in the recess is substantially equal to or higher than the surrounding bottom surface. It is preferable to have a height. Further, at least the average water depth d of the bottom surface A formed by the laid material.₁And the average water depth d of the bottom surface B around the recess (around the recess)₀[D₁-D₀] Is 2 m or less, preferably 1 m or less, more preferably 0.5 m or less, and particularly preferably 0.3 m or less (provided that all of [d₁-D₀It is particularly desirable to include a negative value. This difference [d₁-D₀] Is 2 m or less, preferably 1 m or less, more preferably 0.5 m or less, and particularly preferably 0.3 m or less, so that the recesses are sufficiently shallow so that water can flow in and out of the recesses smoothly. (That is, there is no stagnation of water in the recess), and the phenomenon that the water in the recess becomes oxygen-free in summer can be appropriately prevented.
[0035]
Here, the average water depth d of the bottom surface A formed by the laying material upper surface₁Is the water depth when the water bottom is flattened when the water bottom A formed by the laying material has undulations or unevenness, and the periphery of the recess (in the vicinity of the recess) The average water depth d of the surrounding water surface B₀Means the water depth when the water bottom surface is leveled when the water bottom surface has unevenness due to undulations or irregularities on the water bottom surface B around the recess.
[0036]
In addition to selecting the laying location of the laying material based on the form of the water bottom (recessed portion) as described above, the hydrogen sulfide or dissolved oxygen concentration in the bottom water is measured, and the water area where hydrogen sulfide is detected in the bottom water or A laying material (blast furnace granulated slag) may be laid on the bottom of the water area where the dissolved oxygen concentration in the bottom layer water is a predetermined value or less.
Here, the bottom layer water is water existing near the bottom of the water. In general, the bottom layer water is water within 2 m, preferably within 1 m from the bottom in the depth direction of the water. A laying material is laid on the bottom of a water area where hydrogen is detected or the measured dissolved oxygen concentration is a predetermined value or less. In the case of hydrogen sulfide, if it is detected from the bottom water, a laying material is laid on the bottom of the water area. In the case of dissolved oxygen concentration, generally, if the dissolved oxygen concentration in the bottom layer water is 10% or less of the saturated dissolved oxygen concentration, hydrogen sulfide may be generated by the action of sulfate reducing bacteria, so the dissolved oxygen concentration is saturated and dissolved. It is preferable to lay a laying material on the bottom of a water area having an oxygen concentration of 10% or less. In general, if the dissolved oxygen concentration in the bottom layer water is 60% or less of the saturated dissolved oxygen concentration, there will be a problem with the habitat of benthic organisms, so the dissolved oxygen concentration is laid on the bottom of the water area where the dissolved oxygen concentration is 60% or less of the saturated dissolved oxygen concentration. You may make it lay material.
[0037]
Further, the flow rate of the bottom layer water may be measured, and a laying material (blast furnace granulated slag) may be laid on the bottom of the water area where the flow rate is a predetermined value or less. This is because the bottom of the bottom layer has a low flow rate, and the bottom of the water that is likely to stagnate is likely to be a source of hydrogen sulfide. In addition, bottom layer water is water existing near the bottom of the water as described above. Generally, it may be water within 2 m, preferably within 1 m from the bottom in the depth direction of the water.
In general, in a water area where the flow rate of bottom layer water is 20 cm / sec or less, the dissolved oxygen concentration or hydrogen sulfide concentration of the bottom layer water is strongly influenced by the bottom of the water. Therefore, it is preferable to lay a laying material on the bottom of the water area having such a flow rate.
[0038]
Furthermore, a laying material (blast furnace granulated slag) may be laid on the bottom of a water area where a density climbing layer is formed in the water due to water temperature or salt concentration. When a density stratum is formed in water, oxygen supplied from the atmosphere to water becomes difficult to diffuse to the bottom water, and hydrogen sulfide is likely to be generated.
The formation of the density crest can be determined by measuring the salinity concentration and / or water temperature in the water. When it is determined that the density crevice has been formed, a laying material is placed on the bottom of the water area. Lay down.
As described above, (a) water bottom where hydrogen sulfide is detected in the bottom water or water bottom where the dissolved oxygen concentration in the bottom water is a predetermined value or less, (b) bottom of water where the flow velocity of the bottom water is a predetermined value or less, (c) In the case where any one of the bottoms of the water area where the density climax is formed due to water temperature and / or salinity in the water is used as the laying place of the laying material, for example, a highly closed port or bay (for example, a rias coast) Etc.) can be targeted.
[0039]
From the above-mentioned action of granulated blast furnace slag, 100% blast furnace granulated slag is the most preferable laying material, but granulated blast furnace slag such as blast furnace granulated slag and other materials such as steelmaking slag. Other slag and materials other than slag may be used in combination. Slag generated in steel manufacturing processes other than blast furnace granulated slag includes blast furnace slow-cooled slag generated in the blast furnace, decarburization slag, dephosphorization slag, desulfurization slag, desulfurization generated in processes such as pretreatment, converter, and casting. Examples thereof include steel slag such as silica slag and cast slag, ore reduction slag, electric furnace slag, and the like, but are not limited thereto, and two or more kinds of slag can be mixed and used. These slags may be used after hydration treatment, carbonation treatment, aging, hydration hardening, carbonation hardening, and the like. Moreover, as materials other than slag, from the viewpoint of resource recycling, urban waste slag, waste concrete, mortar and refractory waste materials, etc. are preferable, but other than this, for example, construction generated residual soil, fly ash, natural sand, natural stone, etc. It may be used.
In addition, municipal waste slag, waste concrete, and the like may be used after being subjected to hydration treatment, carbonation treatment, aging, hydration hardening, carbonation hardening, and the like.
[0040]
When using blast furnace granulated slag and other materials as the laying material, in order to appropriately obtain the action of the blast furnace granulated slag as described above, 50 mass% or more of the laying material laid in the recess, preferably It is desirable that 80 mass% or more is composed of granulated blast furnace slag. In that case, blast furnace granulated slag and other materials may be mixed, or blast furnace granulated slag may be laid in the recess so that the other material is on the upper layer side and the other material is on the lower layer side. preferable.
[0041]
In addition, when the upper layer is composed of a laying material including blast furnace granulated slag and the lower layer is composed of a laying material made of other materials, in order to appropriately obtain the effect of the blast furnace granulated slag as described above, The content of the granulated blast furnace slag is 60 mass% or more, preferably 80 mass% or more.
In addition, when the upper layer of the laying material in the recess is constituted by a laying material containing 60 mass% or more (preferably 80 mass% or more) of blast furnace water granulated slag, the thickness of the upper layer is 0.1 m or more. Preferably, the thickness is 0.5 m or more. If the thickness of this upper layer is less than 0.1 m, the water containing hydrogen sulfide below it will easily pass through, and there is a possibility that the above-described action cannot be obtained sufficiently. In addition, if the thickness is less than 0.1 m, the thickness management itself during construction becomes difficult. In particular, if the thickness of the upper layer is 1 m or more, the upper layer portion does not mix with the bottom mud, so that the slag does not solidify, and therefore provides a sandy water bottom suitable as a habitat for living organisms. it can.
[0042]
In addition, when using other slag with blast furnace granulated slag, when using steelmaking slag such as desiliconized slag, decarburized slag, etc., these slags have high iron oxide content. Compared with this, it has a feature that the effect of fixing hydrogen sulfide and phosphorus is large. For this reason, hydrogen sulfide and phosphorus in bottom mud can be effectively fixed, for example by constituting the lower layer of the laying material in a crevice with steel slag or the laying material containing steel slag. When the lower layer is composed of a laying material containing steelmaking slag, the content of steelmaking slag in the lower layer is preferably 60 mass% or more, preferably 80 mass% or more. When the content of the steelmaking slag in the lower layer is less than 60 mass%, the above-described effects specific to the steelmaking slag cannot be sufficiently obtained.
[0043]
Further, when the lower layer of the laying material in the recess is constituted by a laying material containing steelmaking slag or steelmaking slag of 60 mass% or more (preferably 80 mass% or more), the thickness of the lower layer is 0.1 m or more, preferably 0. .3m or more is desirable. If the thickness of this lower layer is less than 0.1 m, water containing hydrogen sulfide or phosphorus passes through this lower layer before hydrogen sulfide and phosphorus in the mud are sufficiently fixed by the steelmaking slag, and the sulfide There is a possibility that the immobilizing action of hydrogen and phosphorus cannot be obtained sufficiently. Moreover, if thickness is less than 0.1 m, thickness management itself in the case of construction will also become difficult.
[0044]
From the characteristics of each slag as described above, for example, the following can be considered as the laying form of the laying material in the recess.
(1) All laying materials: granulated blast furnace slag
(2) Upper layer of laying material: blast furnace granulated slag, lower layer of laying material: slag other than blast furnace granulated slag and / or materials other than slag
(3) Upper layer of laying material: Blast furnace granulated slag, Lower layer of laying material: Steelmaking slag
(4) Upper layer of the laying material: blast furnace granulated slag, middle layer of the laying material: material other than slag or a mixture of slag and material other than slag, lower layer of laying material: steelmaking slag
[0045]
4 (a) to 4 (d) show a state in which a laying material 2 (laying material containing blast furnace water granulated slag or blast furnace water granulated slag) is laid in the concave portion 1 of the bottom of the water, respectively. As shown, the laying material 2 has an average water depth d of the bottom surface A formed thereby.₁And the average water depth d of the bottom surface B around the recess₀[D₁-D₀] Is 2 m or less, preferably 1 m or less (particularly preferably, the bottom surface A formed by the laying material 2 is approximately equal to or higher than the bottom surface B around the recess). The
[0046]
FIG. 4 (a) shows an embodiment in which a laying material 2 composed of 100% blast furnace granulated slag or a blasting material 2 mixed with blast furnace granulated slag and other materials (for example, waste concrete) is laid in the recess 1. Show. Fig. 4 (b) shows the blast furnace granulated slag and other materials used as the laying material 2. The material 21 (for example, waste concrete) other than the blast furnace granulated slag is placed on the lower layer side. Embodiment which each slag 20 was laid in the upper layer side is shown. Moreover, FIG.4 (c) uses the blast furnace granulated slag 20a and the other slag 20b (for example, steelmaking slag) as the laying material 2, The blast furnace granulated slag 20a is made into the upper layer side, and other slag 20b Is shown on the lower layer side. Furthermore, FIG. 4 (d) shows a laying material 2 (for example, the above-mentioned (a) to (c)) in the concave portion 1 which is artificially formed by installing the caisson 3 on the water bottom where the shallow concave portion is formed. The embodiment which laid the laying material of such a form is shown.
[0047]
Moreover, also when laying laying material on the water bottom other than a recessed part, it is desirable for the content rate of the granulated blast furnace slag in a laying material to be 60 mass% or more, Preferably it is 80 mass% or more, and especially consists only of blast furnace granulated slag. Laying materials are most preferred. As laying materials other than the blast furnace granulated slag, the above-mentioned various slags, municipal waste slag, waste concrete, and the like can be used. Further, the thickness of the laying material is 0.1 m or more, preferably 0.5 m or more for the same reason as described above.
[0048]
The preferred embodiments relating to the laying (covering sand) of granulated blast furnace slag for the purpose of preventing the occurrence of blue tide as described above are summarized as follows.
(1) Blast furnace granulated slag having a ratio of slag particles having a particle size of 0.5 mm or more, preferably 90 mass% or more, preferably 70 mass% or more, at the bottom of the water, which is a hydrogen sulfide generation source. How to improve the underwater environment.
(2) The ratio of slag particles having a particle diameter of 0.5 mm or more is 90 mass% or more, preferably 70 mass%, or the ratio of slag particles having a particle diameter of 1.0 mm or more in the recesses formed in the bottom of the water. Underwater environmental improvement method to lay laying material consisting of the above granulated blast furnace slag.
(3) The proportion of slag particles with a particle size of 0.5 mm or more is 90 mass% in whole or in part in the water bottom where water sulfide is detected in the bottom water or in the water bottom where the dissolved oxygen concentration in the bottom water is a predetermined value or less. As described above, preferably an underwater environmental improvement method for laying a laying material made of granulated blast furnace slag having a particle size of 1.0 mm or more in a ratio of 70 mass% or more.
[0049]
(4) The ratio of the slag particles having a particle diameter of 0.5 mm or more is 90 mass% or more, preferably slag particles having a particle diameter of 1.0 mm or more at the bottom of the water area where the flow rate of the bottom layer water is a predetermined value or less Underwater environmental improvement method of laying laying material made of granulated blast furnace slag with a ratio of 70 mass% or more.
(5) The proportion of slag particles having a particle size of 0.5 mm or more is 90 mass% or more, preferably the particle size at the bottom of the water area where the density climatic layer is formed in the water due to water temperature or / and salt concentration. An underwater environment improvement method for laying a laying material made of granulated blast furnace slag having a ratio of slag particles of 1.0 mm or more of 70 mass% or more.
[0050]
(6) The ratio of slag particles having a particle size of 0.5 mm or more is 90 mass% or more, preferably 70 mass%, or the proportion of slag particles having a particle size of 1.0 mm or more in the recesses formed in the bottom of the water. The laying material made of the above blast furnace granulated slag is laid, and the average water depth d of the bottom surface formed by the laying material₁And the average water depth d at the bottom of the water around the recess₀[D₁-D₀] 2 m or less (however, [d₁-D₀] Is a negative value).
(7) In the environmental improvement method of said (1)-(6), laying material consists of blast furnace granulated slag and other materials, and this laid material is mixed with blast furnace granulated slag and other materials. A method for improving the underwater environment where the blast furnace granulated slag is on the upper layer side and the other materials are on the lower layer side.
[0051]
(8) In the environmental improvement method of said (1)-(7), the underwater environmental improvement method in which 50 mass% or more of the laying material laid in the water bottom consists of granulated blast furnace slag.
(9) The environmental improvement method according to (8), wherein the uppermost layer of the laying material laid on the bottom of the water includes 60 mass% or more of blast furnace granulated slag.
(10) A blue tide prevention material laid on the bottom of the water, which is a source of hydrogen sulfide, and the ratio of slag particles having a particle size of 0.5 mm or more is 90 mass% or more, preferably slag particles having a particle size of 1.0 mm or more. A material for improving the environment in water characterized by comprising blast furnace granulated slag having a ratio of 70 mass% or more.
[0052]
(B) Laying blast furnace granulated slag for the purpose of beach nourishment, shallow ground creation or tidal flat creation
Beach nourishment refers to supplying sand from the outside to the coast where sandy beaches have disappeared due to coastal erosion or the like, or to the coast where artificial beaches are created.
A tidal flat is a flat place that is submerged at high tide but dries up at low tide and has sand and mud on its surface. In general, the tidal flat develops in the estuary and the inner bay. Moreover, a shallow place literally refers to a shallow sea area with a depth of several meters or less. On the sea floor that extends from the coast to the offshore, a terrain that moves to a slightly steep slope called the so-called “falling point” is often found at a depth of about a few meters, but in general, a shallow field is located on the shallow side of this falling point. Refers to the sea area.
[0053]
Sandy beaches, tidal flats, and shallow ground are the main habitats of benthic organisms such as shellfish and sandworms, but blast furnace granulated slag having a predetermined particle size configuration is laid as beach nourishment or tidal flat / shallow ground preparation material by the method of the present invention. By doing so, as described above, it is possible to provide an environment in which the benthic organisms are liable to live, and it is possible to significantly increase the amount of benthic organisms.
[0054]
In addition, the granulated blast furnace slag laid in the method of the present invention is white and has a very small proportion of needle-like materials contained in the original granulated blast furnace slag. Can form safe sand (sand beaches, tidal flats, shallow fields) that will not be damaged by needles.
Also, blast furnace granulated slag laid as beach nourishment material, tidal flats and shallow ground construction material has the function of purifying the bottom and water as described in (A) above, and silicic acid as described later. Since it also has a function as a release source of salt ions, an effect of purifying sediment / water quality and an effect of promoting the growth of seaweeds by silicate ions eluted from slag can be obtained.
The beach or water area to which this embodiment is applied may be any of a sea, a river, an estuary, a lake and the like including a harbor.
[0055]
The preferred embodiments regarding the laying of granulated blast furnace slag for the purpose of beach nourishment, tidal flats, shallow ground creation, etc. are summarized as follows.
(1) A blast furnace granulated slag having a ratio of slag particles having a particle diameter of 0.5 mm or more as a beach nourishing material of 90 mass% or more, preferably 70 mass% or more of a slag particle having a particle diameter of 1.0 mm or more. A method of improving the environment of underwater or water beaches by laying the beach.
(2) The ratio of slag particles having a particle size of 0.5 mm or more as a tidal flat construction material is 90 mass% or more, preferably the ratio of slag particles having a particle size of 1.0 mm or more in a place where a tidal flat should be created (including restoration). A method for improving the environment of underwater or watery beaches where tidal flats are constructed by laying blast furnace granulated slag of 70 mass% or more.
(3) The ratio of slag particles having a particle size of 0.5 mm or more as a shallow field preparation material is 90 mass% or more, preferably a ratio of slag particles having a particle size of 1.0 mm or more, as a shallow field preparation material on the sea floor where shallow fields should be created (including repair). Is a method for improving the environment of underwater or watery beaches by constructing shallow ground by laying blast furnace granulated slag of 70 mass% or more.
[0056]
(C) Laying blast furnace granulated slag for the purpose of preventing burning
The bottom of the sea where firewood is burning to which this embodiment is applied means that the surface of the seaweed settlement base such as reefs and artificial fish reefs is covered with lime algae, so that useful seaweeds such as kombu, wakame and alame disappear. It refers to the bottom of the sea that is or is disappearing.
Useful seaweeds (eg, kombu, wakame, arame, etc.) breed for seafood in sea areas where the surface of the seaweed settlement, such as rocky reefs and artificial fish reefs, is covered with lime algae. However, there is a problem that the fishery production in the sea area is significantly reduced.
[0057]
Conventionally, measures such as installing a steel algae reef have been tried for the sea area where the sea bream has occurred. However, when a steel algae reef is installed, seaweeds other than lime algae have remained in the algae reef for about two years. Although the algae reef part is bred and the burnt state is resolved, the steel algae reef is covered with lime algae after about 3 years, and the effect is lost. For this reason, measures such as installing a steel algae reef are necessary, and it cannot be a drastic solution to prevent burning. Recently, there have been cases where seaweed beds have been revived by eliminating sea urchins in the sea area where the sea bream was burned, but since the sea urchin needs to be removed manually, it is inefficient and costly. It is not possible to become a trump card for eliminating firewood burning because the sea area that can be applied to is narrow.
[0058]
On the other hand, it is known that diatoms grow by increasing the silicate concentration in seawater, and as a result, the growth of lime algae is suppressed. A method has been proposed in which a glass plate with adjusted solubility of components is attached to the surface of a concrete reef such as concrete, and this is submerged in a toasted sea area. Japanese Patent Laid-Open No. 6-335330 discloses a seaweed bed made of a vitreous material containing silicon, sodium and / or potassium, and iron for the purpose of growing seaweeds by elution of components into seawater. A method has been proposed in which a breeding material is submerged in the sea.
[0059]
However, the glassy material used to increase the silicate concentration in seawater in such a conventional technique is expensive because it is an artificial material, and this causes burning of the seaweed, or the seaweed growing environment for some reason. If it is installed in large quantities in a wide area that has faded or disappeared, it will cost a huge amount of money. Further, according to the study by the present inventors, the artificial vitreous material used in the prior art is not necessarily sufficient for the dissolution of silicon into seawater and the amount of sedimentation is limited. Was limited to the vicinity of the place where it was installed, and it was found that effective burning improvement effect and improvement effect of seaweed growth environment could not be obtained.
[0060]
In order to solve such a problem, the ground granulated blast furnace slag having a predetermined particle size configuration according to the method of the present invention is applied to the bottom of a sea area where sea burning or seaweed growing environment has faded or disappeared. By laying, the granulated blast furnace slag becomes a release source of silicate ions effective for the growth of seaweeds, and can improve or prevent burning and promote the growth of seaweeds. In addition, the blast furnace granulated slag laid on the bottom of the water provides a good habitat for the benthic organisms for the reasons described above, resulting in a significant increase in their habitat.
In addition, when blast furnace granulated slag is laid on the bottom of the water, it can be used in a mixed state with other materials (for example, steel slag, fly ash, silica sand, mountain sand, sea sand, clay, etc.) Even in this case, it is necessary to use an amount of granulated blast furnace slag required to secure a desired silicate elution amount.
[0061]
Blast furnace granulated slag is SiO₂Glassy material containing a large amount of components and CaO components (in general, SiO₂Therefore, the granulated blast furnace slag laid on the bottom of the water is a silicate network by attacking Ca ions generated by dissolution of CaO contained in the blast furnace granulated slag. The salt network is disrupted, resulting in the elution of silicate ions in water. That is, in the case of granulated blast furnace slag, in addition to the action of gradually dissolving silicate ions in water by cutting the silicate network structure with water molecules, the silicate network structure with Ca ions dissolved from the slag Therefore, the silicate ion elution mechanism of blast furnace granulated slag is the same as that of the artificial glassy material mentioned above as the prior art. This is a combination of the elution action of silicate ions by water molecules and the elution action of silicate ions by the attack of Ca ions, and silicates are much easier to elute than artificial glass.
[0062]
Furthermore, granulated blast furnace slag is obtained by quenching blast furnace slag (molten slag) in a molten state at high temperature with jet water. There are characteristics.
In other words, artificial vitreous materials are generally dense in structure, while blast furnace granulated slag is a vitreous material having a porous structure with countless internal pores as described above, and relatively fine particles. It becomes. For the same reason, the particles of granulated blast furnace slag have an angular shape (a shape having a number of sharp portions on the surface). Therefore, the blast furnace granulated slag has a much larger specific surface area than the granular material obtained by crushing an artificial glassy material with a crushing device. It has a feature that silicate ions are easily eluted. In addition, since many sharp points on the surface of granulated blast furnace slag particles are in a fine form, fine powder is very suitable for dissolving silicate as well as having high component solubility. .
[0063]
In addition, from the above morphological features, the blast furnace granulated slag laminate has a larger filling gap than the granular laminate obtained by crushing an artificial vitreous material with a crushing device, And since the granulated blast furnace slag used by this invention has a comparatively coarse particle size structure, water permeability is very excellent. For this reason, the silicate ion which elutes from the laminated body of granulated blast furnace slag has the characteristic that it is easy to spread | diffuse outside the laminated body compared with the artificial glassy material.
[0064]
In addition, since blast furnace granulated slag elutes Ca ions, it has the effect of suppressing the generation of hydrogen sulfide as described above when installed in water. Is less likely to occur, resulting in less hydrogen sulfide and more dissolved oxygen than in natural sand and glass laminates. This state can be said to be a habitable state for living organisms, and therefore blast furnace granulated slag installed in the sea is a source of silicate ions, and also functions as an organism's epiphytic foundation, From this point as well, it is effective in improving the burning.
[0065]
By the way, as slag obtained as a by-product in the steel manufacturing process, blast furnace slag, steelmaking slag (for example, decarburization slag, dephosphorization slag, desulfurization slag, desiliconization slag, electric furnace) Steelmaking slag etc.), but these slag particles are dense and not porous like blast furnace granulated slag, and the particle size of slag particles is much larger than blast furnace granulated slag, Moreover, even when this is pulverized, the shape of each slag particle does not become an angular shape (a shape having a number of sharp portions on the surface) like blast furnace granulated slag. For this reason, the specific surface area is much smaller than that of granulated blast furnace slag. Moreover, since the blast furnace slow-cooled slag has a large amount of sulfide elution, there is a problem that the COD of seawater is increased and the concentration of hydrogen sulfide is increased in the filling gap of the slag laminate. Many steelmaking slags are made of SiO.₂Since there is little content of CaO and there is much content of CaO, the amount of dissolution of silicate is also small from this aspect. Therefore, these slags cannot sufficiently supply silicate ions into the water, and none of them is suitable for the anti-burning material.
[0066]
The basicity of granulated blast furnace slag is four-component basicity (CaO + Al₂O₃+ MgO) / SiO₂1.6 to 2.5, preferably 1.6 to 2.0. If the basicity of the granulated blast furnace slag is less than 1.6, SiO in the slag₂Since the stability of silicate increases, the elution of silicate ions into seawater tends to decrease. On the other hand, when the basicity exceeds 2.0, particularly when it exceeds 2.5, the amount of crystalline material in the slag increases, and the elution of Ca increases simultaneously with the elution of silicate. In some cases, the amount of silicate supplied to the water decreases due to the formation of precipitates.
[0067]
The concentration of silicate ions in water necessary for the growth of diatoms is 10 μmol / L or more. Such silicate ion concentration is easily achieved by laying blast furnace granulated slag. As a result, diatoms are stably propagated on the surface of the seaweed settlement base on the seabed. As a result, the growth of lime algae is suppressed, and large-scale seaweeds such as kelp and alame breed. In addition, diatoms that have propagated on the surface of the seaweed settlement base are food for seafood, unlike lime algae. In addition, since elution of silicate ions from the granulated blast furnace slag continues for a long period of time, the growth of diatoms and the accompanying burning prevention effect will also continue for a long period of time.
[0068]
Next, a particularly preferred embodiment of the method for creating a seaweed bed in the seared sea area will be described.
In this seaweed bed construction method, it is preferable to install granulated blast furnace slag around or near the seaweed settlement base at the bottom of the sea where firewood is burning. As a result, the silicate ions eluted from the granulated blast furnace slag increase the concentration of silicate in the seawater around the seaweed settlement base, and the seaweed growth base can be effectively propagated.
The seaweed settlement base may be either natural or artificial. In the former case, it is a reef, and in the latter case, it is a steel block, a concrete block, a natural stone, a slag lump or the like. In the latter case, the seaweed settlement base may be installed after blast furnace granulated slag is laid. The bottom of the sea where the artificial seaweed settlement base is installed does not matter whether it is a reef zone or sand.
[0069]
In addition, the blast furnace granulated slag can be installed not only in the sea area where the burning is actually occurring, but also in the bottom of the sea where the burning is likely to occur, thereby preventing the burning in the sea area. In this case as well, the blast furnace granulated slag is installed in the same form as described above.
In addition, as mentioned above, the main sea area (the sea area where the sea bass burning actually occurs or may occur) is mainly the sea area facing the open sea. Therefore, it is a sea area that contrasts with a sea area that has been eutrophied by river inflow nutrients or the like that generate a so-called red tide.
[0070]
The preferred embodiment of the method according to the present invention relating to the laying of blast furnace granulated slag for the purpose of preventing the burning of firewood as described above is summarized as follows.
(1) The ratio of slag particles having a particle size of 0.5 mm or more is 90 mass% or more, preferably 70 mass% of the slag particles having a particle size of 1.0 mm or more, as an anti-burning material, A method for improving the underwater environment by constructing a seaweed bed in the seared sea area by laying the above granulated blast furnace slag.
(2) In the environmental improvement method of (1) above, improving the underwater environment by constructing a groundwater slag in the seared sea area by laying blast furnace granulated slag around or near a natural or artificial seaweed settlement base Method.
(3) In the environmental improvement method of (2) above, an underwater environmental improvement method for constructing a seaweed bed in a seawater-burned sea area by installing an artificial seaweed settlement base after laying blast furnace granulated slag.
[0071]
(4) The ratio of slag particles having a particle size of 0.5 mm or more as the anti-burning material is 90 mass% or more, preferably 70 mass in the sea bottom where there is a risk of burning. A method for improving the underwater environment that prevents firewood burning by laying more than 50% of granulated blast furnace slag.
(5) In the environmental improvement method of (4) above, an underwater environmental improvement method for preventing firewood burning by laying blast furnace granulated slag around or near a natural or artificial seaweed settlement base.
(6) In the environmental improvement method of (5) above, after laying blast furnace granulated slag, an underwater environmental improvement method for preventing firewood burning by installing an artificial seaweed settlement base.
(7) Slag burning prevention material laid on the bottom of the sea where the burning is occurring or where the burning is to be prevented, and the ratio of slag particles having a particle size of 0.5 mm or more is 90 mass% or more The material for environmental improvement in water which consists of blast furnace granulated slag whose ratio of the slag particle | grains with a particle size of 1.0 mm or more preferably is 70 mass% or more.
[0072]
(D) Laying blast furnace granulated slag to prevent red tide
Red tide is a phenomenon in which microorganisms in the water, especially phytoplankton, grow abnormally and color the seawater. In recent years, a great deal of damage has been caused to aquaculture, such as drowning a large amount of cultured fish (such as hamachi and Thailand). Therefore, prevention measures are eagerly desired.
The variety of organisms that cause the red tide is thought to be diverse, but among them, the major growth of certain flagellate algae such as shutella is considered to be the main cause of the red tide that causes massive mortality of cultured fish. Since red tide occurs in sea areas where eutrophication has progressed, it is considered effective to reduce river inflow nutrients by covering sand, dredging and sewerage in order to prevent red tide.
[0073]
However, the effect of sand cover and dredging is lost due to newly deposited organic matter after the completion of construction, and because the sea area where construction is possible is limited to relatively shallow sea areas, the occurrence of red tide is a problem. It is difficult to apply to the center. In addition, these construction works are very expensive, and this is also a factor that limits the scope of application. In addition, reducing the amount of nutrients flowing into the river by improving the sewerage system is effective in reducing the amount of nutrients in the entire sea area. One of the causes of proliferation of flagellated algae such as Shutnera, which causes red tide, is the cause of eutrophication of surface seawater and a decrease in diatoms in surface seawater due to this eutrophication.
[0074]
Recently, as one of the measures to prevent red tide, a method of breeding diatoms by applying soluble silicon (silicate ions) to seawater and suppressing the growth of flagellae such as shutella that cause red tide has been studied. In connection with this method, Japanese Patent Application Laid-Open No. 10-94341 proposes a red tide prevention method in which an artificial glassy material containing soluble silicon is attached to a floating body and installed in the sea.
Addition of soluble silicon to seawater is known to propagate diatoms in underwater seawater, and diatoms are competing species of flagella such as shutella that cause red tide. In addition, since the growth ability is higher than that of flagellate algae, if diatoms are stably present in the surface seawater, abnormal growth of flagellae such as shutella is suppressed, and as a result, the occurrence of red tide is prevented.
[0075]
However, the glassy material used for increasing the silicate concentration in the seawater in the above-described prior art is expensive because it is an artificial material, and it is enormous if it is installed in large quantities in the wide sea area where the red tide occurs. Cost. In addition, as described above, according to the study by the present inventors, the artificial vitreous material used in the prior art is not necessarily sufficient for the dissolution of silicon into seawater, and the amount of sedimentation is also large. Therefore, it was found that the supply of silicon is limited to the vicinity of the installation location, and an effective red tide prevention effect cannot be obtained.
To solve such problems, by laying blast furnace granulated slag having a predetermined particle size structure on the bottom of the water as a red tide preventing material according to the present invention method, the blast furnace granulated slag becomes a release source of silicate ions. Generation is effectively suppressed. In addition, the blast furnace granulated slag laid on the bottom of the water provides a good habitat for the benthic organisms for the reasons described above, resulting in a significant increase in their habitat.
[0076]
When blast furnace granulated slag is laid on the bottom of the water, it can be used in a mixed state with other materials (eg steelmaking slag, fly ash, silica sand, mountain sand, sea sand, clay, etc.). However, it is necessary to use the amount of granulated blast furnace slag required to secure the desired amount of silicon (silicate ion) elution.
As described above in (C), the granulated blast furnace slag has excellent characteristics as a release source of silicate ions. Therefore, the granulated blast furnace used in the environmental improvement method of this embodiment is also used. Slag composition and properties, blast furnace granulated slag laying configuration, elution mechanism of silicate ions from blast furnace granulated slag, other functions of blast furnace granulated slag, etc. are the same as those described for (C) above. It is.
[0077]
In the red tide prevention method according to the present embodiment, the blast furnace granulated slag is preferably installed within a depth of 15 m (hereinafter shallow), preferably within 10 m (however, both are at the depth of low tide). This is because if the installation depth of the granulated blast furnace slag is too large, the eluted silicate ions are difficult to reach the surface seawater, and the efficiency is poor in increasing the silicate concentration in the surface seawater.
In addition, when the red tide generation area is close to the coast (for example, within a few km from the coast), blast furnace granulated slag may be laid so as to cover the seabed within a depth of 15 m, preferably within 10 m. Seawater in the coastal sea area has a high silicate concentration due to the silicate ions eluted from the granulated slag, and this seawater is washed offshore by the ocean current, increasing the silicate concentration in the surface seawater in that area, and diatoms Can be effectively propagated.
[0078]
The concentration of silicate ions in seawater necessary for the growth of diatoms is set to 10 μmol / L or more. Such silicate ion concentration sets blast furnace granulated slag in the sea according to the method of the present invention. It is easily achieved by installing in the sea, preferably within a depth of 15 m (more preferably within a depth of 10 m). As a result, diatoms (competitive species of flagellae such as shuttella) stably propagate in the surface seawater, and abnormal growth of flagellae such as shuttella that cause red tide is prevented. In addition, stable breeding of diatoms is effective for the growth of fish and shellfish using this as food, and is effective for increasing marine resources. In addition, since elution of silicate ions from the granulated blast furnace slag continues for a long period of time, the growth of diatoms and the accompanying red tide prevention effect also continue for a long period of time.
[0079]
The main sea area (old red tide frequent sea area) to which the red tide prevention method according to this embodiment is applied is a sea area that is eutrophied mainly by inflow nutrients in the inland sea and bay, so that so-called “burning” occurs. This is a contrasting sea area.
Further, in the above embodiment, the case where the present invention is applied to the seawater area has been described. However, the red tide is also generated in the brackish water area and the freshwater area. Therefore, the red tide prevention method according to the present embodiment is applied to these water areas. Even can be applied.
[0080]
The preferred embodiment relating to the laying of blast furnace granulated slag for the purpose of preventing the occurrence of red tide as described above is summarized as follows.
(1) In seawater, brackish water, or freshwater, the proportion of slag particles with a particle size of 0.5 mm or more as a red tide prevention material in water is 90 mass% or more, preferably the proportion of slag particles with a particle size of 1.0 mm or more is 70 mass. An underwater environment improvement method that prevents the occurrence of red tide by installing more than 50% of granulated blast furnace slag.
(2) In the environmental improvement method of (1) above, an underwater environmental improvement method for preventing the occurrence of red tide by installing blast furnace granulated slag in water within a depth of 15 m.
(3) It is a red tide prevention material installed in a sea area where red tide is generated or a sea where red tide should be prevented, and the ratio of slag particles having a particle size of 0.5 mm or more is 90 mass% or more, preferably the particle size A material for improving the environment in water comprising blast furnace granulated slag having a slag particle ratio of 1.0 mm or more of 70 mass% or more.
[0081]
Specific embodiments of the underwater environment improvement method of the present invention include the above-described forms, that is, the blue tide prevention method (covering sand), the nourishment method of beach nourishment or tidal flat / shallow ground, and the seagrass bed creation method of the seared sea area In addition to the methods for preventing burning and red tide, there are, for example, environmental improvement methods (restoration) for sea areas where the seaweed growth environment has declined or disappeared due to causes other than burning.
Even in such an environmental improvement method, the composition and properties of the blast furnace granulated slag used, the laying form of the blast furnace granulated slag, the elution mechanism of silicate ions from the blast furnace granulated slag, and other blast furnace granulated slag The functions are the same as those described above for the seaweed bed construction method and the method of preventing sea urchin in the sea bream sea area.
[0082]
Each of the embodiments (A), (C), and (D) of the present invention described above may also be performed to create or repair a so-called shallow field facing the coast. In other words, the so-called shallow ground suitable for the growth and habitat of seaweeds and seafood mainly in the sea area facing the coast may fade or disappear due to the loss of sea sand or drought. It is possible to lay blast furnace granulated slag as a sand-capping material or the like on the bottom of the sea.
In this case, it is preferable to install a submerged dike around the blast furnace granulated slag that is laid in order to prevent the blast furnace granulated slag from being lost due to ocean currents. In addition, it is preferable to provide an artificial seaweed settlement base and fishing reef in the area where blast furnace granulated slag is laid, so as to improve the growth and habitat environment of seaweeds and seafood.
[0083]
The submerged dike to prevent runoff of granulated blast furnace slag can be made of any material, but by building up the submerged dike by building up the bulk slag (bulk slag generated in the steel manufacturing process), for example concrete A submerged bank can be formed easily and inexpensively without using a product or constructing a concrete structure. While granulated blast furnace slag is originally in a granular form, steelmaking slag, etc. is easy to obtain in bulk and has a large specific gravity. Therefore, a solid submerged dike is constructed by stacking this to a predetermined height. Moreover, since the slag is massive, there is no fear of disappearance due to ocean currents. In addition, steelmaking slag has an effect of purifying the bottom sediment and water quality, and thus has an advantage that it can contribute to the improvement of the underwater environment.
[0084]
The bulk slag used is a blast furnace slow-cooled slag generated in a blast furnace (however, this blast furnace slow-cooled slag is preferably sufficiently aged to prevent S from eluting in water), pretreatment, converter , Decarburized slag, dephosphorized slag, desulfurized slag, desiliconized slag, steelmaking slag such as cast slag, ore reducing slag, electric furnace slag, etc. generated in the process of casting, etc., and using these two or more Also good. Among these slags, decarburized slag and cast slag are particularly preferable in terms of high specific gravity. Moreover, as a magnitude | size of slag, generally a thing with a lump diameter of about 30 mm or more is preferable.
In addition, the submerged dike is a block made of slag as a main raw material as described later, that is, a CaCO produced by a carbon dioxide reaction of a granular raw material made mainly of slag generated in a steel manufacturing process.₃It is also possible to form a block obtained by solidifying as a main binder, a hydrated cured body block using slag generated in the steel production process as a main raw material, and the like. By properly stacking these blocks, a robust submerged bank can be constructed. You may use these and the said massive slag together.
[0085]
Artificial seaweed settlement bases and fishing reefs installed in the blast furnace granulated slag laying area can be composed of natural stones, blocks, steel structures, etc., especially steel as described above Blocks obtained by carbonizing solid slag generated in the manufacturing process, slag generated in the steel manufacturing process (steel slag) as a main raw material, or hydration hardening using steel slag as the main raw material It is preferable to use a body block or the like.
[0086]
Among these, the massive slag generated in the steel manufacturing process is as described above.
In addition, as a block obtained by carbonizing and solidifying steel slag as a main raw material, for example, CaCO produced by carbonation reaction of a granular raw material mainly using steel slag as proposed in Patent No. 3175694 is proposed.₃(In some cases, MgCO₃) Can be used as a main binder. Steel slag includes various types of slag as mentioned above, that is, granulated blast furnace slag and blast furnace slow-cooled slag generated in the blast furnace, decarburized slag, dephosphorization generated in processes such as pretreatment, converter and casting. Steelmaking slag such as slag, desulfurization slag, desiliconization slag, cast slag, ore reduction slag, electric furnace slag, and the like can be used.
[0087]
The block (stone) obtained by carbonizing such steel slag is (1) CaO contained in slag (or Ca (OH) generated from CaO).₂) Is mostly CaCO₃Therefore, it is possible to prevent the pH of seawater from rising due to CaO. (2) By containing an appropriate amount of iron (especially metallic iron and metal-containing iron) in the slag, this iron is eluted into the seawater. Iron is supplemented as a nutrient salt inside, and this effectively works for the growth of seaweeds. (3) The block obtained by carbonizing slag has a porous property as a whole (surface and inside). Because of this, seaweeds are easy to adhere to the stone surface, and the inside of the stone is also porous, so there are ingredients (for example, silicate ions and iron) that are effective in promoting the growth of seaweed contained in the stone. It functions effectively as a seaweed settlement base and fishing reef due to its elution into seawater. In addition, by using blast furnace granulated slag as part or all of the main raw material slag, elution of silicate ions as described above can be promoted in particular, improving the seaweed growth environment and preventing burning Especially effective for preventing red tide. For this reason, it is most preferable to use blast furnace granulated slag as the entire raw material or main raw material of the block.
[0088]
Moreover, the hydration hardening block which uses steel slag as a main raw material is obtained by hydrating and hardening a raw material containing steel slag as a main raw material (aggregate and / or binder). Slag, blast furnace granulated slag generated in blast furnace, blast furnace slow-cooled slag, decarburized slag, dephosphorized slag, desulfurized slag, desiliconized slag generated in processes such as pretreatment, converter, casting, etc. Steelmaking slag such as cast slag, ore reduction slag, electric furnace slag, and the like can be used. In the production of a block by hydration curing, the raw material is kneaded with water, then placed in a mold and usually cured for 1 to 4 weeks to produce the block.
[0089]
Also, by using blast furnace granulated slag as part or all of the slag that is the main raw material (aggregate and / or binder), elution of silicate ions as described above can be particularly promoted, It is particularly effective for improving the seaweed growth environment, preventing firewood burning, and preventing red tides. For this reason, it is most preferable to use blast furnace granulated slag as the entire raw material or main raw material of the block.
In addition to the above-mentioned fine powder of granulated blast furnace slag, as a binder used for the block, silica-containing substances (for example, clay, fly ash, silica sand, silica gel, silica scum), cement, slaked lime, NaOH, etc. are appropriately used. It can also be used in combination.
[0090]
When installing the above blocks in the blast furnace granulated slag laying area, individual blocks may be installed on the blast furnace granulated slag layer, or a plurality of blocks may be stacked or assembled. In particular, when a block has a function as a fishing reef, it is preferable to form a space part where a plurality of blocks can be stacked or assembled so that seafood can live between the plurality of blocks.
Moreover, when installing massive slag in the laying area | region of a blast furnace granulated slag, arbitrary installation forms, such as stacking slag in a mountain shape or putting slag in a wire netting etc., can be taken, for example.
[0091]
In the construction or restoration of shallow areas using blast furnace granulated slag as described above, massive slag and / or slag (particularly preferably blast furnace granulated slag) is mainly used as a submerged dike for preventing blast furnace granulated slag outflow. Use blocks made of raw materials, and also use blocks made mainly of bulk slag and / or slag (particularly preferably blast furnace granulated slag) as seaweed settlement bases and fishing reefs to be installed in the area where blast furnace granulated slag is laid As mentioned above, slag as described above improves the environment in water (that is, improves the growth environment of seaweeds by the growth of diatoms, suppresses the occurrence of sea urchin / red tide, prevents the generation of hydrogen sulfide, Generation suppression, bottom sediment / water purification, etc.) are most effective, and 100% recyclable without using natural resources as materials for construction or restoration of shallow fields Can be used wood (steel slag), effective use of recycled materials, the cost of the construction, it is extremely advantageous in terms of prevention of environmental destruction by the use of natural resources.
[0092]
FIG. 5 shows an embodiment of shallow field creation or restoration using blast furnace granulated slag as a laying material, 4 is a blast furnace granulated slag laid at an appropriate thickness on the bottom of the water, and 5 is laid. In order to prevent the flow of granulated blast furnace slag, it is a submerged dike installed around the blast furnace granulated slag 4, and this submerged dike 5 is constructed by stacking massive slag (steel slag). Furthermore, 6 is a block that forms a seaweed settlement base and / or fishing reef by being stacked on the laid blast furnace granulated slag layer. As this block 6, steel slag (preferably blast furnace granulated slag) is used. A block obtained by carbonizing a powdery raw material as a main raw material, or a hydrated hardened body block using steel slag (preferably blast furnace granulated slag) as a main raw material is used.
[0093]
In this way, the blast furnace granulated slag 4 is laid on the seabed, and a massive slag is used as the submerged dike 5 for preventing the runoff. Further, steel slag (preferably blast furnace granulated slag) is used in the laid area of the blast furnace granulated slag 4. By installing the constructed block 6 as a seaweed settlement base and / or fishing reef, a shallow field most suitable for the growth and habitat environment of seaweeds and seafood is created or restored.
In addition, the composition and properties of the blast furnace granulated slag used in the construction or restoration of the shallow ground described above, the laying form of the blast furnace granulated slag, the elution mechanism of silicate ions from the blast furnace granulated slag, and other blast furnaces The functions of the granulated slag are the same as those described above for the seaweed formation method and the method for preventing sea urchin burning in the sea bream sea area.
[0094]
A preferred embodiment in the case of providing a submerged dike for preventing slag flow as described above is summarized as follows.
(1) Laying blast furnace granulated slag with a ratio of slag particles with a particle size of 0.5 mm or more on the seabed facing the coast of 90 mass% or more, preferably with a ratio of slag particles with a particle size of 1.0 mm or more being 70 mass% or more In addition, a submerged slag for preventing slag flow is installed around the blast furnace granulated slag laying area, and an artificial seaweed settlement base and / or fishing reef is installed in the blast furnace granulated slag laid area. Environmental improvement methods.
(2) In the environmental improvement method of the above (1), at least a part of the submerged dike is made of massive slag generated in the steel manufacturing process, and a granular raw material made mainly of slag generated in the steel manufacturing process by a carbonic acid reaction. Generated CaCO₃A method for improving the underwater environment comprising at least one selected from a block obtained by solidifying as a main binder and a hydrated cured body block made mainly of slag generated in a steel production process.
(3) In the environmental improvement method of the above (1) or (2), at least a part of the artificial seaweed settlement base and / or fishing reef, massive slag generated in the steel manufacturing process, slag generated in the steel manufacturing process CaCO produced by carbonic acid reaction of granular raw materials mainly composed of₃A method for improving the underwater environment comprising at least one selected from a block obtained by solidifying as a main binder and a hydrated cured body block made mainly of slag generated in a steel production process.
[0095]
【Example】
[Example 1]
Laying blast furnace granulated slag with a ratio of 90 mass% or more of slag particles with a particle size of 0.5 mm or more obtained by sieving on the sea floor where sludge with a depth of 4 m is deposited in a range of 10 m x 10 m with a thickness of 30 cm (Example of the present invention). In addition, as a comparative example, blast furnace granulated slag having a mass ratio of 85 mass% of slag particles having a particle diameter of 0.5 mm or more obtained by sieving was laid under the same conditions on the adjacent seabed under the same conditions. In addition, only a small amount of sandworms lived in the seabed where this sludge was deposited.
[0096]
One year after the laying, the amount of biological habitat in the blast furnace granulated slag laying layer, the amount of dissolved oxygen and the amount of hydrogen sulfide in the water immediately above the laying layer and the surrounding sludge layer were investigated. As a result, in both the present invention example and the comparative example, various bottom organisms such as shellfish and sandworms lived in the laying layer of the granulated blast furnace slag. / M²Comparative example is 503 g / m²Thus, the amount of biological inhabitants of the examples of the present invention was about 20% higher than that of the comparative examples. As for the amount of dissolved oxygen, the amount of dissolved oxygen immediately above the sludge was 1.2 ppm, whereas the amount of dissolved oxygen immediately above the laying layer was 6 ppm in both the inventive example and the comparative example. As for the amount of hydrogen sulfide, 0.02 ppm of hydrogen sulfide was detected in the water immediately above sludge, whereas no hydrogen sulfide was detected in the water directly above the laying layer of the present invention and the comparative example.
[0097]
[Example 2]
Blast furnace granulated slag with a ratio of slag particles with a particle size of 1.0 mm or more obtained by sieving in a region from the sea bottom where the sludge with a depth of 5 m is accumulated to the beach as a sandy beach is 50 cm to 2 m. It was laid in a range of 20 m × 60 m in thickness (example of the present invention). In addition, as a comparative example, blast furnace granulated slag having a mass ratio of 80 mass% obtained by sieving and slag particles having a particle size of 0.5 mm or more was laid under the same conditions on adjacent seabeds under similar conditions. In addition, only a small amount of sandworms lived in the seabed where sludge was deposited.
[0098]
One year after laying, investigation of the biological habitat in the blast furnace granulated slag laying layer, the dissolved oxygen amount and hydrogen sulfide water directly above the laying layer and the surrounding sludge layer, and the pH of pore water in the laying layer went. As a result, in both the present invention example and the comparative example, various bottom organisms such as shellfish and sandworms lived in the laying layer of the granulated blast furnace slag. / M²Comparative example is 472 g / m²Thus, the amount of biological inhabitants of the examples of the present invention was about 40% higher than that of the comparative examples. As for the amount of dissolved oxygen, the amount of dissolved oxygen immediately above the sludge was 0.5 ppm, whereas the amount of dissolved oxygen immediately above the laying layer having a water depth of 2 m was 7 ppm in both the present invention example and the comparative example. As for the amount of hydrogen sulfide, 0.05 ppm of hydrogen sulfide was detected in the water directly above the sludge, whereas no hydrogen sulfide was detected in the water directly above the laying layer of the present invention example and the comparative example. In addition, the pH of the pore water at a depth of 0.5 m from the upper surface of the slag laying layer at a point where the water depth is 2 m and the slag laying thickness is 2 m is 8.5 in the present invention example, which is a level that can suppress the activity of sulfate-reducing bacteria. Met. In the comparative example, the pH of the pore water was 8.7, which was higher than that of the inventive example.
[0099]
[Example 3]
・ Invention example (1)
As shown in FIG. 6, granulated blast furnace slag having a mass ratio of 95 mass% or more obtained by sieving into a reefed bottom of a reefed seabed is 10 m in thickness of 20 cm. It installed in the range of * 10m. After that, we continued to investigate the growth of diatoms and large-scale seaweeds at the bottom of the sea. As a result, one week after the slag installation, adhering diatoms were observed on the reef near the slag installation place, and one month after the slag installation, adhering diatoms were observed from the slag installation place to 30 m downstream of the ocean current. Large seaweeds were observed in the vicinity of the slag installation location one month after the slag installation, and were observed in the range 20 m downstream of the ocean current six months after the slag installation. Further, in the long-term observation, diatoms and large-scale seaweeds were observed after 5 years as well as after 6 months. The size of large seaweeds has increased.
[0100]
・ Invention example (2)
In the sea area where the reef sea bottom of 20m around the sandy seabed is in a burnt state, as shown in FIG. 7, the sandy part has a particle size of 1.0 mm or more obtained by sieving. A granulated blast furnace slag having a slag particle ratio of 85 mass% or more was installed in a range of 30 m × 30 m with a thickness of 50 cm. Furthermore, a steelmaking slag hardened body and steelmaking slag were installed on it, and an artificial reef was made. After that, we continued to investigate the deposition of attached diatoms and large-scale seaweeds on the seabed in the vicinity. As a result, one week after slag installation, adhering diatoms were observed on the artificial reef at the slag installation site, and one month after slag installation, adhering diatoms were also observed on the reef 20 m away from the slag installation site. Large seaweeds were observed on artificial reefs at the slag installation site one month after the slag installation, and also on reefs 20 m away from the installation site six months after the slag installation. In long-term observations, diatoms and large seaweeds were observed on both artificial and natural reefs after 5 years, as well as 6 months later. The size of large seaweeds has increased.
[0101]
[Example 4]
Blast furnace granulated slag with a ratio of 95 mass% or more of slag particles with a particle size of 0.5 mm or more obtained by sieving to the sea floor near the coast in the red tide frequent occurrence sea area (inside the bay) 500 m to 1 km offshore. Laying to a thickness of 30 cm. The laying range was from the coastline to 40m offshore (water depth 2-7m), and the total length of the coastline was 200m.
After the installation of granulated blast furnace slag (in the summer season), the silicate concentration and the amount of diatoms in the surface seawater at the installation location and the traditional red tide generation point (sea area) were continuously investigated. The results are shown in Table 2. According to this, two weeks after the installation of the granulated blast furnace slag, the silicate concentration in the surface seawater at the installation location and the traditional red tide generation point increased, and the red tide was originally low in silicate concentration. The amount of diatoms also increased at the occurrence point. The survey continued for three years after the installation of granulated blast furnace slag, but no red tide was observed during this period, and many seaweed and seafood were observed at the location where the granulated blast furnace slag was installed.
[0102]
[Table 2]

[0103]
[Example 5]
・ Invention example (1)
Slag particles with a particle size of 1.0mm or more obtained by sieving into a recess (deep digging part) with a diameter of about 30m formed on the flat bottom of the bay (the bottom of the mud on the sand) The average height difference between the blast furnace granulated slag having a ratio of 90 mass% or more and the bottom surface around the recess is 1 m or less ([d₁-D₀] ≦ 1 m). The laying thickness was about 15 m.
In order to investigate the degree of suspension in the water due to the laying of the laying material, the amount of suspended solids immediately before laying the laying material and immediately after laying the laying material (at 30 minutes) at a water depth of 5 m directly above the center of the recess. The amount of suspended solids was measured and the difference was determined.
In addition, after laying the laying material, every three years over the three years, each directly above the bottom surface of the laying part, directly above the bottom surface at a point 50 m away from the laying part, and immediately above the bottom surface at a point 100 m away from the laying part. The hydrogen sulfide concentration of water was measured at the position. In addition, the amount of settlement (average value) at the top surface level (water bottom surface) of the laying material three years after the laying was measured. The results are shown in Table 3.
[0104]
・ Invention example (2)
Slag particles with a particle size of 1.0 mm or more obtained by sieving into a recess (deep digging) with a diameter of about 20 m formed on the flat bottom of the bay (the bottom of the mud on the sand) The average height difference between the bottom of the water around the recess is 1 m or less ([d] in a mixture of granulated blast furnace slag 60 mass%, blast furnace slow-cooled slag 10 mass%, steelmaking slag 20 mass%, municipal waste slag 10 mass%₁-D₀] ≦ 1 m). The laying thickness was about 10 m.
In order to investigate the degree of suspension in the water due to the laying of the laying material, the amount of suspended solids immediately before laying the laying material and immediately after laying the laying material (at 30 minutes) at a water depth of 5 m directly above the center of the recess. The amount of suspended solids was measured and the difference was determined.
In addition, after laying the laying material, every three years over the three years, each directly above the bottom surface of the laying part, directly above the bottom surface at a point 50 m away from the laying part, and immediately above the bottom surface at a point 100 m away from the laying part. The hydrogen sulfide concentration of water was measured at the position. In addition, the amount of settlement (average value) at the top surface level (water bottom surface) of the laying material three years after the laying was measured. The results are shown in Table 3.
[0105]
・ Invention example (3)
The proportion of slag particles with a particle size of 0.5 mm or more obtained by sieving into a 50 m × 50 m range of the bottom of the water where the mud has accumulated on the sandy surface is 90 mass% or more. A mixture of blast furnace granulated slag 90 mass% and steelmaking slag 10 mass% was laid to a thickness of 50 cm.
In order to investigate the degree of suspension in the water due to the laying of the laying material, the amount of suspended solids immediately before laying the laying material and immediately after laying the laying material (at 30 minutes) at a point of 5 m above the center of the laying area The amount of suspended solids was measured and the difference was determined.
In addition, after laying the laying material, every three years over the three years, each directly above the bottom surface of the laying part, directly above the bottom surface at a point 50 m away from the laying part, and immediately above the bottom surface at a point 100 m away from the laying part. The hydrogen sulfide concentration of water was measured at the position. The results are shown in Table 3.
[0106]
・ Comparative example (1)
The average height difference between the sea sand and the bottom of the water around the recess is less than 1m in the recess (deep digging) with a diameter of about 40m formed on the flat bottom of the bay (sand bottom where the mud deposits on the sand) ([D₁-D₀] ≦ 1 m). The laying thickness was about 8 m.
In order to investigate the degree of suspension in the water due to the laying of the laying material, the amount of suspended solids immediately before laying the laying material and immediately after laying the laying material (at 30 minutes) at a water depth of 5 m directly above the center of the recess. The amount of suspended solids was measured and the difference was determined.
In addition, after laying the laying material, every three years over the three years, each directly above the bottom surface of the laying part, directly above the bottom surface at a point 50 m away from the laying part, and immediately above the bottom surface at a point 100 m away from the laying part. The hydrogen sulfide concentration of water was measured at the position. In addition, the amount of settlement (average value) at the top surface level (water bottom surface) of the laying material three years after the laying was measured. The results are shown in Table 3.
[0107]
・ Comparative example (2)
About the recessed part (deep digging part) with a diameter of about 30m and a depth of 10m formed on the flat bottom of the bay (sand bottom where mud is deposited on the sand) is almost the same as when laying the laying material in Invention Example 1. Water at each position directly above the bottom of the deep digging section, half a year over three years from the season, directly above the bottom of the deep digging section at a point 50 m away from the deep digging section, and just above the bottom of the water bottom at a point 100 m away from the deep digging section The hydrogen sulfide concentration of was measured. The results are shown in Table 3.
[0108]
[Table 3]

[0109]
[Example 6]
Proportion of slag particles with a particle size of 1.0 mm or more obtained by sieving the bottom of the sea water in the water area (about 400 m square water area) where the dissolved oxygen concentration of the bottom layer water is about 2 ppm (saturated solubility: about 7 ppm) However, blast furnace granulated slag of 85 mass% or more was laid in a thickness of about 20 cm. After one month, when the dissolved oxygen concentration of the bottom layer water in the slag laying water area was measured, it was increased to about 4.5 ppm.
[Example 7]
The ratio of slag particles having a particle size of 1.0 mm or more obtained by sieving on the seabed of the water region (about 1 ha) where the hydrogen sulfide concentration of the bottom layer water is 0.5 to 1.2 ppm is 90 mass% or more. Blast furnace granulated slag was laid to a thickness of about 35 cm. After one month, six months, and one year, the hydrogen sulfide concentration of the bottom water in the slag laying water area was measured (measurement method: detector tube type, detection limit: 0.01 ppm), but hydrogen sulfide was detected. There wasn't.
[0110]
[Example 8]
Thickness of granulated blast furnace slag with a ratio of 95 mass% or more of slag particles with a particle size of 0.5 mm or more obtained by sieving on the seabed of the water zone (about 1.5 ha) with a flow rate of bottom layer water of 3 cm / second Laying about 3m. When comparing the water quality of the bottom water before slag laying and after 3 months from slag laying, the hydrogen sulfide concentration was 1.8 ppm and the dissolved oxygen concentration was 0.2 ppm before slag laying. After 3 months from laying the slag, the hydrogen sulfide concentration was below the detection limit and the dissolved oxygen concentration was improved to 4.8 ppm.
[0111]
[Example 9]
Obtained by sieving on the sea bottom of the water area (about 10 ha) where the density climax by the seawater salinity (surface water salinity: 1.5%, bottom water salinity: 2.6%) was formed. Blast furnace granulated slag having a ratio of 95 mass% or more of slag particles having a particle diameter of 1.0 mm or more was laid to a thickness of about 0.2 m. The water quality of the bottom water before the slag laying and after 3 months from the slag laying were compared. The hydrogen sulfide concentration was 3ppm and the dissolved oxygen concentration was 0.1ppm before slag laying. After 3 months, the hydrogen sulfide concentration was below the detection limit, the dissolved oxygen concentration was improved to 4 ppm, and the bottom of the water became shallow due to the blast furnace granulation slag, so the salinity of the bottom water It decreased to 2.3%.
[0112]
[Example 10]
A particle size of 1.0 mm obtained by sieving on the seabed of the water area (about 0.5 ha) where the density jump layer (surface water temperature: 24 ° C., bottom water temperature: 14 ° C.) formed by seawater temperature is formed. Blast furnace granulated slag having a slag particle ratio of 90 mass% or more was laid to a thickness of about 3 m. When comparing the water quality of the bottom water before slag laying and 6 months after slag laying, the hydrogen sulfide concentration was 0.8 ppm and the dissolved oxygen concentration was 0.3 ppm before slag laying. After 6 months from the slag installation, the hydrogen sulfide concentration was below the detection limit, the dissolved oxygen concentration was improved to 3 ppm, and the bottom of the water became shallow due to the blast furnace granulation slag installation. Also rose to 16 ° C.
[0113]
【The invention's effect】
As described above, according to the underwater environment improvement method of the present invention, it is preferable to install a ground granulated blast furnace slag having a predetermined particle size configuration that is inexpensive and available in large quantities, in a preferable environment on the bottom of a water or a beach, In particular, it is possible to form an environment suitable for living organisms living in sandy areas, such as sand cover, beach nourishment, shallow ground and tidal flats. In addition, it can also exhibit excellent effects in preventing the occurrence of blue tide, preventing burning of salmon, preventing the occurrence of red tide, or creating seaweed beds and restoring the seaweed growing environment.
[Brief description of the drawings]
FIG. 1 is a graph showing a typical particle size configuration (sieving passing weight) of as-produced blast furnace granulated slag
FIG. 2 is an explanatory diagram showing the action of a laying material laid in a recess in the bottom of the water in the conventional method.
FIG. 3 is an explanatory view showing the action of the laying material laid in the concave portion of the water bottom in the embodiment of the present invention.
FIG. 4 is an explanatory view showing an embodiment of the underwater environment improvement method according to the present invention.
FIG. 5 is an explanatory diagram showing a shallow field created in the embodiment of the underwater environment improvement method according to the present invention.
FIG. 6 is an explanatory diagram showing the implementation status of seaweed beds in the seared sea area in Example 3
FIG. 7 is an explanatory diagram illustrating another implementation status of seaweed beds in the seared sea area in Example 3.
[Explanation of symbols]
A ... Blast furnace granulated slag, 1, 1 '... Recess, 2 ... Laying material, 3 ... Caisson, 4 ... Blast furnace granulated slag, 5 ... Submerged dike, 6 ... Block, 20 ... Slag, 20a ... Blast furnace granulated slag, 20b ... Slag other than granulated blast furnace slag, 21 ... Material other than slag, X, Y ... Water bottom

Claims (8)

  An underwater or beach environment improvement method characterized by laying ground granulated blast furnace slag having a particle size of 0.5 mm or more in a blast furnace granulated slag having a ratio of 90 mass% or more.   An underwater or beach environment improvement method characterized by laying blast furnace granulated slag having a particle size of 1.0 mm or more in a ratio of 70 mass% or more on a water bottom or beach. The ratio of slag particles having a particle size of 1.0 mm or more is 80 mass A method for improving the environment of underwater or beaches, characterized by laying ground granulated blast furnace slag at or above the water bottom or beach. Laying blast furnace water granulated slag on the bottom of the water or on the beach as sand-capping material, beach nourishing material, shallow ground material, tidal flat material, seaweed ground material, drought prevention material, red tide prevention material or blue tide prevention material The method for improving the environment of water or a beach according to any one of claims 1 to 3 . The method for improving the environment of water or a beach according to any one of claims 1 to 4, wherein the granulated blast furnace slag laid on the bottom of the water or on the beach serves as a silicate ion release source.   It is a material laid on the bottom of the water or on the beach as a sand-covering material, beach nourishing material, shallow ground material, tidal flat material, seaweed ground material, drought burning prevention material, red tide prevention material or blue tide prevention material. A material for improving the environment of underwater or beaches, characterized by comprising blast furnace granulated slag having a ratio of slag particles of 0.5 mm or more of 90 mass% or more.   It is a material laid on the bottom of the water or on the beach as a sand-covering material, beach nourishing material, shallow ground material, tidal flat material, seaweed ground material, drought burning prevention material, red tide prevention material or blue tide prevention material. A material for improving the environment of underwater or beaches, characterized by comprising blast furnace granulated slag having a ratio of 1.0 mm or more of slag particles of 70 mass% or more. It is a material laid on the bottom of the water or on the beach as a sand-covering material, beach nourishing material, shallow ground material, tidal flat material, seaweed ground material, drought prevention material, red tide prevention material or blue tide prevention material. The ratio of slag particles of 1.0 mm or more is 80 mass A material for improving the environment of underwater or watery beaches, characterized by comprising blast furnace granulated slag that is at least%.

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