JP5807872B2 - Method for estimating the amount of natural heavy metal elements dissolved in water - Google Patents
Method for estimating the amount of natural heavy metal elements dissolved in water Download PDFInfo
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本発明は、土壌及び／又は岩石からの自然由来の重金属元素等の水系への溶出量を推定するための推定方法に関し、特に水質変化シミュレーションと併せて重金属元素等の水系への溶出量を長期的に推定するための推定方法に関する。 TECHNICAL FIELD The present invention relates to an estimation method for estimating the amount of elution of naturally-derived heavy metal elements from soil and / or rocks into an aqueous system, and in particular, the amount of elution of heavy metal elements into an aqueous system along with water quality change simulation. The present invention relates to an estimation method for estimation.
トンネル工事などの掘削で多量の残土が発生する。かかる残土には、ヒ素、セレン、カドミウム、鉛、クロム、亜鉛、銅、水銀などの有害な元素が微量に含まれていることがある。なお、以下において、これらの元素を単に「重金属元素等」と称する。このため、掘り返された残土が雨水や地下水等の水に曝されると、自然由来の重金属元素等が水系に溶出して自然環境を汚染することが指摘されている。そこで掘削工事の施工前の土壌及び／又は岩石（以下、「土壌等」と称する。）に含まれる重金属元素等の各種の測定が行われる。 Excessive soil is generated by excavation such as tunnel construction. Such residual soil may contain trace amounts of harmful elements such as arsenic, selenium, cadmium, lead, chromium, zinc, copper, and mercury. Hereinafter, these elements are simply referred to as “heavy metal elements and the like”. For this reason, it has been pointed out that when the excavated residual soil is exposed to water such as rainwater or groundwater, naturally-derived heavy metal elements are eluted into the water system and pollute the natural environment. Therefore, various measurements such as heavy metal elements contained in soil and / or rock (hereinafter referred to as “soil etc.”) before excavation work are performed.
例えば、非特許文献１では、土壌等に含まれる重金属元素等を特定するための測定方法について述べられている。掘削工事の施工前の土壌等から試料を採取、この試料を蛍光Ｘ線分析法や湿式分析法などで化学分析して元素を特定している。
For example, Non-Patent
ところで、土壌等に含まれる自然由来の重金属元素等の水系への溶出量を長期的に推定することは、公定法や特許文献１又は２に開示されたような土壌等の溶出試験だけでは困難であり、かかる溶出量を推定するために土壌等に含まれる鉱物種の溶出による水質変化シミュレーションが併せて行われる。該シミュレーションにより得られた水質変化に対応して、土壌等に含まれる重金属元素等の溶出量を推定するのである。ここで共沈現象など、特定の鉱物種の水への溶出が他の鉱物種の溶出にも影響を与えるため、かかる水質変化シミュレーションは非常に複雑である。
By the way, it is difficult to estimate the amount of elution of naturally-derived heavy metal elements and the like contained in soil in the water system in the long term only by the elution test of soil or the like as disclosed in the official method or
例えば、上記した非特許文献１では、このような水質変化シミュレーションの１つとして、米国地質調査所が無償供給しているＰＨＲＥＥＱＣなる地球化学用シミュレータについても述べられている。かかるシミュレータによれば、土壌等の情報と水系の情報から現在の水質がどのような反応系を経て形成されたかを推定できる。詳細には、水系の形成機構モデルを構築して、これに基づいて複数の各鉱物種の化学平衡論計算を行う。化学平衡論計算によれば、複数の鉱物種の溶出量を互いの相関関係を考慮しつつ得られ、これに反応速度項を加えて計算することによりｐＨを含む水質の時間変化をシミュレーション出来るのである。
For example, Non-Patent
非特許文献１に挙げられた地球化学用シミュレータ以外にもいくつかの水質変化シミュレーションが知られており、土壌等の化学分析などの実測値から水系の少なくともｐＨ情報を含む水質変化を求めることができる。かかるシミュレーションでは、鉱物種の水系への溶出量を求めるのと同様に、重金属元素等の情報を入力することで、理想的な重金属元素等の水系への溶出量についても求め得る。
In addition to the geochemical simulator listed in Non-Patent
本発明は、上記したような状況に鑑みてなされたものであって、本発明の目的とするところは、土壌及び／又は岩石からの自然由来の重金属元素等の水系への溶出量を推定するための推定方法において、水質変化シミュレータと併せて重金属元素等の水系への溶出量を長期的に推定するための推定方法を提供することである。 This invention is made | formed in view of the above situations, Comprising: The place made into the objective of this invention estimates the elution amount to the water system of the heavy metal element derived from nature, etc. from a soil and / or a rock. An estimation method for providing an estimation method for estimating the amount of elution of heavy metal elements into an aqueous system in the long term in conjunction with a water quality change simulator.
本発明による推定方法は、土壌等に含まれる自然由来の重金属元素等の水系への溶出量を長期的に推定するための推定方法であって、前記土壌等から採取された試料の化学分析などから前記水系の少なくともｐＨ情報を含む水質変化をシミュレートする水質変化シミュレーションと併せて、前記化学分析から得られた前記重金属元素等の含有情報から前記水質変化に対応させて前記重金属元素等の各々の理想溶存量及び水酸化鉄の沈殿量を求めるステップと、前記沈殿量に対応して吸着される前記重金属元素等の吸着量を求めるステップと、前記理想溶存量から前記吸着量を減じて前記重金属元素等の前記溶出量を推定するステップと、を含むことを特徴とする。 The estimation method according to the present invention is an estimation method for long-term estimation of the amount of elution of naturally-derived heavy metal elements contained in soil or the like into an aqueous system, such as chemical analysis of a sample collected from the soil or the like In addition to a water quality change simulation for simulating a water quality change including at least pH information of the water system, each of the heavy metal elements etc. corresponding to the water quality change from the content information of the heavy metal elements obtained from the chemical analysis Determining the ideal dissolved amount and iron hydroxide precipitation amount, obtaining the adsorption amount of the heavy metal element or the like adsorbed corresponding to the precipitation amount, subtracting the adsorption amount from the ideal dissolved amount, and Estimating the amount of elution of heavy metal elements and the like.
かかる発明によれば、土壌等からの自然由来の重金属元素等の各々の理想溶存量を補正して該重金属元素等の水系への溶出量を長期的に推定できるのである。すなわち、本発明者は、重金属元素等が水中へ溶出する場合、水系に存在する水酸化鉄のような沈殿物によって重金属元素等が吸着され、残部だけが水中に溶出して存在することに注目し、本発明に至ったのである。 According to this invention, it is possible to correct the ideal dissolved amount of each of the naturally derived heavy metal elements from the soil or the like and to estimate the amount of elution of the heavy metal elements into the water system over a long period of time. That is, the present inventor noticed that when heavy metal elements and the like are eluted into water, the heavy metal elements and the like are adsorbed by precipitates such as iron hydroxide present in the aqueous system, and only the remainder is eluted and present in water. Thus, the present invention has been achieved.
上記した発明において、前記土壌等に粘土鉱物が含まれる場合において、前記水質変化に対応させて前記粘土鉱物の沈殿量を求めこれに対応させて吸着される前記重金属元素等の吸着量を前記理想溶存量から更に減じるステップを含むことを特徴としてもよい。かかる発明によれば、粘土鉱物を含む土壌等であっても、土壌等からの自然由来の重金属元素等の各々の理想溶存量を補正して該重金属元素等の水系への溶出量を長期的に高精度で推定できるのである。 In the above-described invention, when clay mineral is contained in the soil or the like, the ideal amount is the amount of adsorption of the heavy metal element or the like adsorbed in accordance with the amount of sedimentation of the clay mineral corresponding to the water quality change. A step of further subtracting from the dissolved amount may be included. According to this invention, even in soil containing clay minerals, etc., the amount of elution of the heavy metal elements etc. into the water system is corrected over the long term by correcting the ideal dissolved amount of each of the naturally derived heavy metal elements etc. from the soil etc. Therefore, it can be estimated with high accuracy.
上記した発明において、前記含有情報は前記重金属元素等の元素種であることを特徴としてもよい。かかる発明によれば、簡便に重金属元素等の水系への溶出量を長期的に推定できるのである。 In the above-described invention, the content information may be an element species such as the heavy metal element. According to this invention, it is possible to easily estimate the amount of elution of heavy metal elements or the like into an aqueous system over a long period of time.
上記した発明において、前記含有情報は前記重金属元素等の元素種毎の含有量であることを特徴としてもよい。また、前記理想溶存量は、前記ｐＨ情報に対応させて求められることを特徴としてもよい。かかる発明によれば、簡便に重金属元素等の水系への溶出量を長期的に推定できるのである。 In the above-described invention, the content information may be a content for each element type such as the heavy metal element. Further, the ideal dissolved amount may be obtained in correspondence with the pH information. According to this invention, it is possible to easily estimate the amount of elution of heavy metal elements or the like into an aqueous system over a long period of time.
上記した発明において、前記理想溶存量は、前記水質変化シミュレーションの中で行われることを特徴としてもよい。かかる発明によれば、より正確に重金属元素等の水系への溶出量を長期的に推定できるのである。 In the above-described invention, the ideal dissolved amount may be performed in the water quality change simulation. According to this invention, it is possible to estimate the amount of elution of heavy metal elements or the like into an aqueous system more accurately over the long term.
上記した発明において、前記重金属元素等は、少なくともヒ素、鉛、セレンの１つ以上を含むことを特徴としてもよい。かかる発明によれば、より正確に重金属元素等の水系への溶出量を長期的に推定できるのである。 In the above-described invention, the heavy metal element or the like may include at least one or more of arsenic, lead, and selenium. According to this invention, it is possible to estimate the amount of elution of heavy metal elements or the like into an aqueous system more accurately over the long term.
本発明による土壌等に含まれる自然由来の重金属元素等の水系への溶出量、特に、ヒ素、鉛、亜鉛の水系への溶出量について長期的に推定する推定方法について図１乃至３を用いて説明する。 The estimation method for estimating the amount of elution of naturally-derived heavy metal elements and the like contained in soil according to the present invention into an aqueous system, particularly the amount of arsenic, lead, and zinc into an aqueous system over a long period of time will be described with reference to FIGS. explain.
まず、該推定方法の概略を図１に沿って説明する。掘削工事の施工予定地域の土壌及び／又は岩石をサンプル採取し（Ｓ１）、これに含まれる元素についての化学分析を行う（Ｓ２）。かかる化学分析の結果から、公知の水質変化シミュレーション、例えば、背景技術の欄で述べたＰＨＲＥＥＱＣのような地球化学用シミュレータによって、水質のｐＨ変化や、少なくともＦｅイオンを含む各種化学種の濃度を求める（Ｓ３）。この水質のｐＨ及びＦｅイオン濃度から水酸化鉄の沈殿量を求め（Ｓ４）、この沈殿量に対応して吸着され得る重金属元素等の吸着量を求める（Ｓ５）。一方、化学分析により検出された重金属元素等、特に、ヒ素、鉛、亜鉛といった元素の量と、上記した水質変化シミュレーションによって得られたｐＨの値から、この水質で溶出し得る理想溶存量を求める（Ｓ７）。若しくは、重金属元素等の元素量比から上記した水質変化シミュレーションにより理想溶存量を求める。そして、重金属元素等の理想溶存量から吸着量を減じることで溶出量を求め得るのである。ここで、土壌等に粘土鉱物が含まれる場合には、粘土鉱物の沈殿量を水酸化鉄の沈殿量とともに求め、これに吸着され得る重金属元素等の吸着量を求め、理想溶存量から更に減じて溶出量を求める（Ｓ８）。 First, the outline of the estimation method will be described with reference to FIG. A sample of soil and / or rock in the planned construction area for excavation work is collected (S1), and chemical analysis is performed on the elements contained therein (S2). From the results of such chemical analysis, the pH change of water quality and the concentration of various chemical species including at least Fe ions are obtained by a known water quality change simulation, for example, a geochemical simulator such as PHREEQC described in the background section. (S3). A precipitation amount of iron hydroxide is obtained from the pH and Fe ion concentration of the water quality (S4), and an adsorption amount of heavy metal elements and the like that can be adsorbed corresponding to the precipitation amount is obtained (S5). On the other hand, from the amounts of heavy metal elements detected by chemical analysis, especially elements such as arsenic, lead, and zinc, and the pH value obtained by the water quality change simulation described above, the ideal dissolved amount that can be eluted with this water quality is obtained. (S7). Alternatively, the ideal dissolved amount is obtained by the above-described water quality change simulation from the amount ratio of heavy metal elements and the like. And the elution amount can be obtained by subtracting the adsorption amount from the ideal dissolved amount of heavy metal elements and the like. Here, when clay minerals are contained in the soil, etc., the amount of clay mineral precipitated is determined together with the amount of iron hydroxide precipitated, the amount of adsorption of heavy metal elements etc. that can be adsorbed to this is determined, and further subtracted from the ideal dissolved amount. To obtain the elution amount (S8).
次に、図１に沿って、各ステップの処理について、その詳細を説明する。 Next, the details of each step will be described with reference to FIG.
掘削工事の施工予定地域から土壌及び／又は岩石をサンプル採取し（Ｓ１）、破砕・粉砕して粉体試料にする。粉体試料は蛍光Ｘ線分析法や湿式分析法などで全岩化学分析され、土壌等の中に含まれる元素を特定する（Ｓ２）。つまり、後述する地殻を構成する主要元素や、Ａｓ，Ｐｂ,Ｓｅなどの重金属元素等の各元素の含有量比を求め得る。ここで、塩酸のような所定の溶媒を用いることで全岩化学分析の結果から、土壌等の中に含まれる重金属元素等を含む各元素の含有量を求めることも出来得る。これに関しては後述する。 Sample soil and / or rock from the planned construction site for excavation work (S1), crush and pulverize it into a powder sample. The powder sample is subjected to whole rock chemical analysis by a fluorescent X-ray analysis method, a wet analysis method or the like, and an element contained in the soil or the like is specified (S2). That is, the content ratio of each element such as a main element constituting the crust described later and heavy metal elements such as As, Pb, and Se can be obtained. Here, by using a predetermined solvent such as hydrochloric acid, the content of each element including heavy metal elements contained in the soil or the like can be obtained from the result of the whole rock chemical analysis. This will be described later.
次に、上記した公知のシミュレーションによれば、全岩化学分析（Ｓ２）の結果から、少なくとも水系のｐＨ及び含まれ得る元素量などの水質情報を得ることができる（Ｓ３）。かかるシミュレーション方法の一例について以下に述べる。 Next, according to the known simulation described above, water quality information such as at least the pH of the water system and the amount of elements that can be contained can be obtained from the result of the whole rock chemical analysis (S2) (S3). An example of such a simulation method will be described below.
例えば、上記した全岩化学分析により、地殻を構成する主要元素としてのＦｅ，Ｍｎ，Ｔｉ，Ｃａ，Ｋ，Ｐ，Ｓｉ，Ａｌ，Ｍｇ，Ｎａの存在比率、微量元素としてＡｓ，Ｐｂ,Ｓｅなどの存在比率が測定されたとする。かかる存在比率から、各主要元素に対応する酸化物Ｆｅ２Ｏ３，ＦｅＯ，ＭｎＯ，ＴｉＯ２，ＣａＯ，Ｋ２Ｏ，Ｐ２Ｏ５，ＳｉＯ２，Ａｌ２Ｏ３，ＭｇＯ，Ｎａ２Ｏの比率に換算する（Ｓ３１）。次に、主要元素の元素量比に基づいて複数のノルム鉱物に系統的に分配するノルム計算によって、土壌中のノルム鉱物の存在量比を決定する（Ｓ３２）。 For example, by the whole rock chemical analysis described above, the abundance ratio of Fe, Mn, Ti, Ca, K, P, Si, Al, Mg, Na as the main elements constituting the crust, As, Pb, Se, etc. as trace elements Suppose that the abundance ratio of is measured. From these abundance ratios, oxides Fe 2 O 3 , FeO, MnO, TiO 2 , CaO, K 2 O, P 2 O 5 , SiO 2 , Al 2 O 3 , MgO, and Na 2 O corresponding to each main element. Converted to a ratio (S31). Next, the abundance ratio of the norm mineral in the soil is determined by norm calculation that systematically distributes the plurality of norm minerals based on the element quantity ratio of the main elements (S32).
土壌中のノルム鉱物の水への溶出については、図３に示すよう、不可逆的な溶解及び沈殿の平衡（Ｓ４１）と、可逆的な溶解及び沈殿の平衡（Ｓ４２）と、の２つを考慮され得る。 Regarding the elution of norm minerals in soil into water, as shown in FIG. 3, two considerations are taken: irreversible dissolution and precipitation equilibrium (S41) and reversible dissolution and precipitation equilibrium (S42). Can be done.
ノルム鉱物の水への不可逆的な溶解及び沈殿の平衡（Ｓ４１）では、ノルム鉱物Ａ、Ｂ、Ｃ、Ｄ、…について、
ｎＡＡ＋ｎＢＢ＋…＝ｎＣＣ＋ｎＤＤ＋… （式１）
の反応を生じるとする。各ノルム鉱物の含有量〔Ａ〕，〔Ｂ〕，〔Ｃ〕，〔Ｄ〕，…について、平衡定数Ｋ’は、
Ｋ’＝〔Ｃ〕ｎＣ〔Ｄ〕ｎＤ・・・／（〔Ａ〕ｎＡ〔Ｂ〕ｎＢ・・・） （式２）
と表される。つまり、（式２）で示すように、平衡定数Ｋ’は、ノルム鉱物の存在量比から計算できる。
In the irreversible dissolution and precipitation of the norm mineral in water (S41), the norm minerals A, B, C, D,...
n A A + n B B +... = n C C + n D D +.
It is assumed that the following reaction occurs. For each norm mineral content [A], [B], [C], [D],..., The equilibrium constant K ′ is
K '= [C] nC [D] nD ... / ([A] nA [B] nB ...) (Formula 2)
It is expressed. That is, as shown in (Formula 2), the equilibrium constant K ′ can be calculated from the abundance ratio of the norm mineral.
一方、ノルム鉱物の水への可逆的な溶解及び沈殿の平衡（Ｓ４２）では、飽和度指数ＳＩについて、平衡溶解度積Ｋｓｐを用いて、（式２）の平衡定数Ｋ’から、
ＳＩ＝Ｌｏｇ（Ｋ’／Ｋｓｐ） （式３）
と定義される。つまり、（式３）から飽和度指数ＳＩが正ならば沈殿反応が生じ、飽和度指数ＳＩが負ならば溶解反応が生じるのである。なお、飽和度指数ＳＩが零ならば平衡状態である。
On the other hand, the equilibrium of the reversible dissolution and precipitation in water norm minerals (S42), the saturation index SI, with an equilibrium solubility product K sp, the equilibrium constant K of (Formula 2) ',
SI = Log (K ′ / K sp ) (Formula 3)
Is defined. That is, from (Equation 3), if the saturation index SI is positive, a precipitation reaction occurs, and if the saturation index SI is negative, a dissolution reaction occurs. If the saturation index SI is zero, it is in an equilibrium state.
各ノルム鉱物の水への溶解及び沈殿の平衡（Ｓ４３）について、反応速度Ｒｋ〔ｍｏｌ・ｓ-１・ｋｇｗ-１〕は、
Ｒｋ＝ｒｋＡ０ｍｋ ｎ／（Ｖｍ０ｋ ｎ） （式４）
で表される。ここで、ｒｋ〔ｍｏｌ・ｍ-２・ｓ-１〕を定数、Ａ０〔ｍ２〕を各ノルム鉱物の初期の表面積、ｍｋ〔ｍｏｌ〕を特定時間におけるノルム鉱物のモル数、Ｖを溶液量〔ｋｇｗ〕、ｍ０ｋ〔ｍｏｌ〕をノルム鉱物の初期モル数とする。更に、ｎは各ノルム鉱物の形状因子（定数）である。例えば、ノルム鉱物の形状が球又は立方体ならば、このｎは２／３である。
About the equilibrium of dissolution and precipitation of each norm mineral in water (S43), the reaction rate R k [mol · s −1 · kgw −1 ] is
R k = r k A 0 m k n / (Vm 0k n) ( Equation 4)
It is represented by Here, r k [mol · m −2 · s −1 ] is a constant, A 0 [m 2 ] is the initial surface area of each norm mineral, m k [mol] is the number of moles of the norm mineral at a specific time, V Is the amount of solution [kgw], and m 0k [mol] is the initial number of moles of the norm mineral. Furthermore, n is a form factor (constant) of each norm mineral. For example, when the shape of the norm mineral is a sphere or a cube, this n is 2/3.
各ノルム鉱物の水への溶解及び沈殿の平衡における反応速度Ｒｋから所定時間後の水中に存在する全元素（イオン）の含有量を求め得る。また、これらから水のｐＨなどの水質情報を求め得る（Ｓ４４）。また、ｐＨに対応して、重金属元素等を含むノルム鉱物の溶解度積などから重金属元素等の濃度Ｃcalc,mについても求め得る。 The content of all elements (ions) present in water after a predetermined time can be determined from the reaction rate R k in the equilibrium of dissolution and precipitation of each norm mineral in water. Moreover, water quality information such as pH of water can be obtained from these (S44). Further, the concentration C calc, m of the heavy metal element or the like can be obtained from the solubility product of the norm mineral containing the heavy metal element or the like corresponding to the pH.
以上は、１つのシミュレーションの方法について述べたが、少なくとも水のｐＨ及び地殻を構成する主要元素の１つであるＦｅイオンの水中での含有量を求めることができるシミュレーションであれば、本発明のために用い得る。 The above is a description of one simulation method, but at least the pH of water and the content of Fe ions, which are one of the main elements constituting the earth's crust, can be determined in the present invention. Can be used for
ところで、上記したシミュレーションの反応速度Ｒｋから得られる重金属元素等の水中での濃度Ｃcalc,mは、実測される値とは差異を生じる。また、ｐＨから簡易的に重金属元素等の水中での濃度Ｃcalc,mを求め得るが、やはり差異を生じる。つまり、かかるシミュレーションによる水中での濃度Ｃcalc,mは理想溶存量である。この原因の１つとして、上記した地殻を構成する主要元素の１つであるＦｅイオンや、粘土質鉱物が重金属元素等、特に、Ａｓ，Ｐｂ,Ｓｅなどを吸着することにある。水に溶出したこれらの重金属元素等のうちＡｓなどは、オキソ酸陰イオンとなるが、これは水酸基と酸素を共有して結合し易い。このような理由により、水酸基を有する水酸化鉄や粘土質鉱物は重金属元素等を吸着すると考えられる。 By the way, the concentration C calc, m in water of heavy metal elements and the like obtained from the reaction rate R k of the simulation described above is different from the actually measured value. Moreover, although the concentration C calc, m in water of a heavy metal element or the like can be easily obtained from pH, a difference still occurs. That is, the concentration C calc in water by such simulations, m is ideal Dissolved amount. One reason for this is that Fe ions, which are one of the main elements constituting the crust, and clay minerals adsorb heavy metal elements, particularly As, Pb, Se, and the like. Among these heavy metal elements eluted in water, As and the like become oxoacid anions, which are easily bonded by sharing hydroxyl and oxygen. For these reasons, it is considered that iron hydroxide and clay mineral having a hydroxyl group adsorb heavy metal elements and the like.
重金属元素等の吸着の補正は、図１に示すように、吸着物質である沈殿物の量を求め（Ｓ４）、かかる沈殿物に吸着され得る重金属元素等の量Ｃsorp,mを求め（Ｓ５）、理想溶存量である濃度Ｃcalc,mからこれを減じる（Ｓ８）のである。
As shown in FIG. 1, the correction of the adsorption of heavy metal elements or the like is performed by determining the amount of precipitate as an adsorbent (S4) and determining the amount C sorp, m of heavy metal elements or the like that can be adsorbed on the precipitate (S5). ) is the concentration C calc ideally dissolved amount subtracts this from the m (S8).
まず、吸着物質の水酸化鉄については、シミュレーションでの水質情報のｐＨ値からこの水中に存在し得る理想のＦｅイオン量〔Ｆｅ３＋〕idealについて、図４に示すような水酸化鉄のイオン反応における溶解度積から、
〔Ｆｅ３＋〕ideal＝１０−３７．２／１０（ｐＨ−１４） （式５）
と表すことが出来る。つまり、水酸化鉄の沈殿量〔Ｆｅ（ＯＨ）３〕Ｓは、シミュレーションでの水質情報の〔Ｆｅ３＋〕calcとともに、
〔Ｆｅ（ＯＨ）３〕Ｓ＝〔Ｆｅ３＋〕calc−〔Ｆｅ３＋〕ideal
＝〔Ｆｅ３＋〕calc-１０−３７．２／１０（ｐＨ−１４） （式６）
のように表される。
First, regarding iron hydroxide as an adsorbing substance, the ideal iron ion amount [Fe 3+ ] ideal that can exist in this water from the pH value of water quality information in the simulation. From the solubility product in
[Fe 3+ ] ideal = 10 −37.2 / 10 (pH−14) (Formula 5)
Can be expressed as In other words, the precipitation amount [Fe (OH) 3 ] S of iron hydroxide, together with [Fe 3+ ] calc of the water quality information in the simulation,
[Fe (OH) 3 ] S = [Fe3 + ] calc- [Fe3 + ] ideal
= [Fe3 + ] calc- 10-37.2 / 10 (pH-14) (Formula 6)
It is expressed as
重金属元素等の水酸化鉄への吸着量Ｃsorp,mは、水酸化鉄の沈殿量〔Ｆｅ（ＯＨ）３〕ＳとｐＨとの関数であるから、
Ｃｓoｒｐ，ｍ＝ｆ（〔Ｆｅ（ＯＨ）３〕Ｓ、ｐＨ） （式７）
のように表される。かかる重金属元素等の水酸化鉄への吸着量Ｃsorp,mは、実験的に得ることが出来る。また、フロイドリッヒの式によれば、ａを定数、ｎを１以上の定数とすると、
Ｃｓoｒｐ，ｍ＝ａ（ｐＨ）×〔Ｆｅ（ＯＨ）３〕Ｓ １／ｎ （式８）
のように簡便にも表し得る。また、分配係数による方法や、ラングミュアの式による方法など、公知の経験式を用い得る。
Since the adsorption amount C sorp, m of heavy metal elements and the like on iron hydroxide is a function of the precipitation amount of iron hydroxide [Fe (OH) 3 ] S and pH,
C sorp, m = f ([Fe (OH) 3 ] S , pH) (Formula 7)
It is expressed as The adsorption amount C sorp, m of such heavy metal elements to iron hydroxide can be obtained experimentally. Further, according to Floydrich's equation, when a is a constant and n is a constant of 1 or more,
C sorp, m = a (pH) × [Fe (OH) 3 ] S 1 / n (Formula 8)
It can be expressed simply as follows. Further, a known empirical formula such as a method using a distribution coefficient or a method using a Langmuir formula can be used.
つまり、重金属元素等の水酸化鉄への吸着量Ｃsorp,mと、シミュレーションで得られる重金属元素等の濃度Ｃcalc,mとから、重金属元素等の溶出量Ｃaq,ｍは、
Ｃaq,m＝Ｃcalc,m−Ｃsorp,m （式９）
と補正され得る。ここで、重金属元素等の濃度Ｃcalc,mは、全岩化学分析により重金属元素等の含有量を求め、シミュレーションから得られたｐＨの値を用いて求めることも出来得る。
That is, from the amount of adsorption C sorp, m of heavy metal elements and the like to iron hydroxide and the concentration C calc, m of heavy metal elements obtained by simulation, the elution amount C aq, m of heavy metal elements etc.
C aq, m = C calc, m −C sorp, m (Equation 9)
And can be corrected. Here, the concentration C calc, m of the heavy metal element or the like can also be obtained by determining the content of the heavy metal element or the like by whole rock chemical analysis and using the pH value obtained from the simulation.
なお、水酸化鉄以外の吸着物質についても、例えば、土壌等が粘土鉱物を含む堆積岩からなる場合などには、粘土鉱物が吸着物質となる。かかる場合にあっても、上記同様に粘土鉱物の沈殿量を求めて、重金属元素等の吸着量を得て補正を行っても良い。 For the adsorbing material other than iron hydroxide, for example, when the soil or the like is made of sedimentary rock containing clay mineral, the clay mineral becomes the adsorbing material. Even in such a case, the amount of sedimentation of the clay mineral may be obtained in the same manner as described above, and the amount of adsorption of heavy metal elements or the like may be obtained and corrected.
上記した実施例によれば、土壌等からの自然由来の重金属元素等の各々の理想溶存量を補正して該重金属元素等の水系への溶出量を長期的に正確に推定できる。 According to the above-described embodiment, it is possible to accurately estimate the amount of elution of the heavy metal element or the like into the water system in the long term by correcting the ideal dissolved amount of each of the naturally derived heavy metal elements or the like from the soil or the like.
以上、本発明による実施例及びこれに基づく変形例を説明したが、本発明は必ずしもこれに限定されるものではなく、当業者であれば、本発明の主旨又は添付した特許請求の範囲を逸脱することなく、様々な代替実施例及び改変例を見出すことができるであろう。 As mentioned above, although the Example by this invention and the modification based on this were demonstrated, this invention is not necessarily limited to this, A person skilled in the art will deviate from the main point of this invention, or the attached claim. Various alternative embodiments and modifications could be found without doing so.
Claims (3)
少なくともＦｅ，Ｍｎ，Ｔｉ，Ｃａ，Ｋ，Ｐ，Ｓｉ，Ａｌ，Ｍｇ，Ｎａを主要元素とし、前記土壌等から採取された試料の化学分析によって得られた前記主要元素及び前記重金属元素等の各元素の含有量比から前記水系のｐＨ変化と、Ｆｅイオンを含む前記重金属元素等及び前記主要元素ごとのイオン濃度及び／又は元素濃度の濃度変化と、を少なくとも含む水質変化をシミュレートする水質変化シミュレーションと併せて、
前記化学分析から得られた前記重金属元素等の前記含有量比から前記水質変化に対応させて理想溶存量を求めるとともに、前記水質変化から水酸化鉄の沈殿量を求めるステップと、
前記沈殿量に対応して吸着される前記重金属元素等の吸着量を前記ｐＨ変化に対応させて求めるステップと、
前記理想溶存量から前記吸着量を減じて前記重金属元素等の前記溶出量を推定するステップと、を含むことを特徴とする自然由来の重金属元素等の溶出量推定方法。 Natural origin of As contained in the soil or the like consisting of excavation soils and / or rock, Pb, the amount of elution of an aqueous heavy metal elements such as consisting of at least one or more of Se in estimation method for estimation There,
At least Fe, Mn, Ti, Ca, K, P, Si, Al, Mg, Na as main elements, and each of the main elements and heavy metal elements obtained by chemical analysis of a sample collected from the soil or the like and p H change in the aqueous from the content ratio of the element, water to simulate the changes in water quality including at least, a change in concentration of the heavy metal element and the like and ion concentration and / or elemental concentrations for each of the major elements containing Fe ions Along with change simulation,
With obtaining the ideal dissolved amount in correspondence with the changes in water quality from the ratio of the content of such a heavy metal elements obtained from the chemical analysis, determining a precipitation amount of iron hydroxide from the water quality changes,
Obtaining an adsorption amount of the heavy metal element or the like to be adsorbed corresponding to the precipitation amount corresponding to the pH change ;
Subtracting the adsorption amount from the ideal dissolved amount to estimate the elution amount of the heavy metal element and the like, and a method for estimating the elution amount of naturally derived heavy metal element and the like.
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