JP3820522B2 - Method for detecting soil contamination by organic liquid substances - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、双極熱パルス法による体積熱容量ρＣ（Ｊ／ｍ３／Ｋ）の測定と、時間域反射法（ＴＤＲ法）による電磁波の反射特性から比誘電率ε及び電気伝導度σの測定とを組み合わせた２線以上のプローブ針を持つプローブを用いて前記各特性をほぼ同時的に観測できるサーモ−ＴＤＲ法により、汚染物濃度及び土壌水分量θが既知の標準土壌の試料を用いて、土壌水分量θと体積熱容量ρＣ（Ｊ／ｍ３／Ｋ）との相関、土壌水分量θと比誘電率εとの相関、及び土壌水分量θと電気伝導度σとの相関を作製し、原位置被測定土壌の体積熱容量ρＣ（Ｊ／ｍ３／Ｋ）又は／及び比誘電率εの測定値から土壌水分量θ（この水分量は、水分中に汚染物がある場合はそれを含めた値である）を検出し、該検出した土壌水分量θと時間域反射法（ＴＤＲ法）による原位置被測定土壌の電気伝導度σとから決定される点を前記標準土壌の試料を用いて作成した土壌水分量θと電気伝導度σとの相関中にプロットして、該プロットの最も近接する土壌水分量θと電気伝導度σとの相関から原位置被測定土壌中の汚染物の存在及び汚染物の濃度を検出することを特徴とする有機液体物質による土壌の汚染を検出する方法に関する。
【０００２】
【従来の技術】
従来、有機溶剤などが地下貯蔵タンク等から漏れて環境を汚染することがあった。そこで、そのような汚染を監視する必用があったが、監視手段としては、前記漏洩物が地下水面に達した後、近傍の井戸水を採取することよって初めて地下水などを汚染していることが発見できるに過ぎなかった。
これに対し、例えば、平成１２年１０月１３日：農業土木学会東北支部 第４５回研究発表会 講演要旨集「ＴＤＲ法による飽和土中のＮＡＰＬ（Non-Aqueous Phase Liquid）含有量測定の試み」（以下、文献１）において、発表者らは、水よりも比重が小さな非水相液（Light Non-Aqueous Phase Liquid＝Ｌ−ＮＡＰＬ）として灯油を用い、水−灯油飽和２相系カラム浸透試験における、供試体の灯油含有量の非破壊的測定方法としてＴＤＲ水分計の利用を検討している。
【０００３】
その測定法は、土の見かけの比誘電率と水分量との間に経験関数関係が成り立つことを利用するものである。その経験関数関係とは、水の比誘電率８０に対して、ＮＡＰＬの比誘電率は土粒子などとほぼ同じであり、土中に存在する場合ＮＡＰＬは土粒子と同質とみなすことができ、したがって、ＴＤＲ水分計により間隙率ｎの土の見かけの比誘電率を測定し、体積含水率既知の土を用いて、予め作製した比誘電率と体積含水率θＷとの相関に前記測定比誘電率を当てはめて、体積含水率θＷを求めると、ＮＡＰＬ含有率θｏｉｌ＝ｎ−θＷの関係からＮＡＰＬ含有量が求められる。しかしながら、前記原理は水−ＮＡＰＬ飽和２相系を前提とするため、飽和水の条件においてのみ適用できるにすぎません。したがって、貯蔵タンクから漏洩した有機溶媒が地下水面に達して初めて検出できるに過ぎない。したがって、漏洩地付近での有機溶媒の漏洩の検出という問題点の解決には役立たない。
【０００４】
土壌の見かけの比誘電率は、土壌水分量、有機溶媒誘電率、存在形態などの関数であり、土壌の見かけの誘電率は土壌の間隙を満たす有機溶媒の含水率により誘電率と含水率の相関関係が異なるので、前記文献記載の方法をそのまま不飽和土壌へ適用することは不可能である。
【０００５】
一方、本発明者らは、体積含水率θ、電気伝導度σ、見かけの比誘電率ε、体積熱容量ρＣなどをほぼ同時的に測定できるサーモ−時間域反射法 (Thermo-Time Domain Reflectometry、Thermo-ＴＤＲ)法を開発した（Ren, T., K. Noborio, and R. Horton. 1999. Measuring soil water content, electrical conductivity, and thermal properties with a thermo-time domain reflectometry probe. Soil Sci. Soc. Am. J. 63:450-457.以下、文献２）。その原理は、２以上、前記文献では３線（ロッド）のプローブ針からなる測定プローブに、前記プローブの少なくとも２以上のプローブ針にＴＤＲ法により前記体積含水率θ、電気伝導度σ及び見かけの比誘電率εを同時に測定でき機能を持たせると同時に、少なくとも２以上のプローブ針に双極熱パルス法（Dual−Probe Heat Pulse Method，ＤＰＨＰ）により、体積含水率θ、体積熱容量ρＣなどを測定できる機能を持たせて、小さな時間間隔、換言すればほぼ同時的に前記２つの測定法により、土壌の体積含液量(q)と電気伝導度(s)、見かけ誘電率ε及び体積熱容量を測定するものである。
【０００６】
前記文献２では、前記測定プローブを用いて、食塩水を用いて体積含水率θと電気伝導度σとの相関特性、体積含水率θと見かけの比誘電率εとの相関などを測定し、前記測定プローブはほぼ同時に体積含液量(q)と電気伝導度(s)、見かけ誘電率ε及び土壌の熱特性の測定に適用できること、そして、体積含水率θと電気伝導度σとの相関特性は良好であるが、土壌水分量θと比誘電率εとの相関には、別個の検量線の作成が必要であることに言及している。
しかしながら、有機溶剤などの汚染の検出及び汚染度を測定する方法に適用することについての言及はない。
【０００７】
地下水に達してからの汚染物質の除去には膨大な時間と経費が必要であるので、早期に不飽和土壌層中での漏れを検出するセンサーの開発が望まれ、汚染物質が地下水面に達する前に、初期段階においての検出が可能であれば、地下水汚染を未然に防止したり、最小限の汚染に食い止めることが可能である。
【０００８】
【発明が解決しようとする課題】
従って、本発明の課題は、有機溶剤などの土壌への漏れを漏洩地点の近傍にて検出する方法を提供することである。
本発明者は、前記文献２に開示したサーモ−ＴＤＲ方法による土壌の監視技術を基本とし、漏洩地点近傍において有機溶剤などの土壌への漏れを検出可能とするために、汚染物と水との飽和系でなくても、少なくとも汚染物の漏洩を検出でき、更には、汚染物の濃度を検出可能できる方法を確立するために、サーモ−ＴＤＲ方法によりほぼ同時測定可能な、体積含水率θに対する電気伝導度σ、見かけの比誘電率ε、及び体積熱容量ρＣのそれぞれの相関を有効に利用することにより、前記課題を解決できる手法が確立できるのではないかと考えた。
そこで、既知の汚染物濃度及び土壌水分量θの標準土壌の試料の体積熱容量ρＣ、比誘電率ε及び電気伝導度σを測定し、前記ほぼ同時的に測定された各特性から、土壌水分量θと体積熱容量ρＣ（Ｊ／ｍ３／Ｋ）との相関、土壌水分量θと比誘電率εとの相関、及び土壌水分量θと電気伝導度σとの相関を作製したところ、前記各相関における、汚染物濃度及び土壌水分量の違いに対する、体積熱容量ρＣ（Ｊ／ｍ３／Ｋ）、比誘電率ε及び電気伝導度σと土壌水分量θの相関に特徴があることを見出し、このような特性をうまく利用すると、汚染物の非飽和系でも、前記汚染物の土壌への漏洩の有無だけでなく、土壌水分中の汚染物のおおよその濃度も測定できることを見出し、本発明の前記課題を解決することができた。
なお、本明細書において、ほぼ同時的とは、同時ではないが、極めて短時間の経時の後に２つの測定が可能であることを意味する。
【０００９】
【課題を解決するための手段】
本発明は、双極熱パルス法による体積熱容量ρＣ（Ｊ／ｍ３／Ｋ）の測定と、時間域反射法（ＴＤＲ法）による電磁波の反射特性から比誘電率ε及び電気伝導度σの測定との組み合わせた測定ができる２線以上のプローブ針を持つプローブを用いて、既知の汚染物濃度及び土壌水分量θの標準土壌の試料の前記各特性をほぼ同時的に測定し、土壌水分量θと体積熱容量ρＣ（Ｊ／ｍ３／Ｋ）との相関、土壌水分量θと比誘電率εとの相関、及び土壌水分量θと電気伝導度σとの相関を作製し、原位置被測定土壌の体積熱容量ρＣ（Ｊ／ｍ３／Ｋ）又は／及び比誘電率εの測定値から土壌水分量θ（この水分量は、水分中に汚染物がある場合はそれを含めた値である）を検出し、該検出した土壌水分量θと原位置被測定土壌の電気伝導度σとに相当する点を前記標準土壌の試料を用いて作成した土壌水分量θと電気伝導度σとの相関中にプロットして、該プロットの最も近接する土壌水分量θと電気伝導度σとの相関における水分中の汚染物濃度から原位置被測定土壌中の汚染物の存在及び汚染物の濃度Ｃを検出することを特徴とする有機液体物質による土壌の汚染を検出する方法である。
【００１０】
好ましくは、比較的水分量が大きい場合には、土壌水分量θと電気伝導度σとの相関上に原位置被測定土壌の水分量をプロットする際の土壌水分量θの値として、土壌水分量θと体積熱容量ρＣ（Ｊ／ｍ３／Ｋ）との相関から得られた土壌水分量の値を利用し、比較的水分量が小さい場合には、土壌水分量θと比誘電率εとの相関から得られた土壌水分量の値を利用することを特徴とする前記の被測定土壌中の汚染物の存在及び汚染物の濃度Ｃを検出する方法であり、より好ましくは、双極熱パルス法における温度センサーを配置したプローブ針及び／又は時間域反射法（ＴＤＲ法）による電磁波の反射及び電気伝導度測定針を２以上とし、被測定土壌領域をプローブ針の数だけ拡げたことを特徴とする前記の各被測定土壌中の汚染物の存在及び汚染物の濃度Ｃを検出する方法であり、更に好ましくは、比誘電率εの測定がオシログラフ上に現れるプローブ針の始端と終端の電磁波の反射点から観察される見かけ状の長さの変化〔Ｌａ／Ｌ（実際のプローブの長さ）〕２の関数として知ることにより算出されることを特徴とする前記各被測定土壌中の汚染物の存在及び汚染物の濃度Ｃを検出する方法である。
【００１１】
【本発明の実施の態様】
本発明をより詳細に説明する。
Ａ．本発明の特徴を図面を参照しながら説明する。
図１は、３針またはロッドからなる３線のプローブ針ＰＲを持ったプローブＰからなり、該プローブ針の少なくとも２線には双極熱パルス法用のヒータＨ及び該ヒータによるパルス加熱の際の温度の経時変化を温度測定器、例えばサーモカップルＴＣまたはサーミスターが配置され、少なくとも１線には時間域反射法（ＴＤＲ法）用の電磁波による比誘電率ε及び電気伝導度σの測定のための同軸ケーブルＣＣに接続された長さＬの電磁波伝達電極ＰＥが配置された構造に設計されている。
前記時間域反射法（ＴＤＲ法）用の電磁波による比誘電率ε及び電気伝導度σの測定のための同軸ケーブルＣＣは、パルス発生器ＰＧと電磁波の相対速度Ｖｐの電磁波伝達電極の始端及び終端から反射た電磁波を検出し、前記電極の見かけ状の長さＬａを表示、情報処理機器を内蔵するオシロスコープＯＳに接続される、図２に示される構造に設計されている。
比誘電率ε及び電気伝導度σは以下の数式（１）及び数式（２）により算出される。
【００１２】
【数１】
【数２】
前記数式（２）において、Ｋｐはプローブの形状係数（１／ｍ）、Ｚｕは測定器の出力インピーダンス（Ω）、ρ∞はプローブ終端から十分離れたところでの電磁波の反射係数である。
【００１５】
双極熱パルス法により、ヒータＨに加えられた電力ｑ〔Ｗ／ｍ（分）〕により熱パルス、例えばｔo=１５秒の熱パルスを加え、これを適当な土壌厚ｒ（ｍ）さを介して配置されたプローブ針（温度センサー針）に配置された温度測定器、例えばサーモカップルＴＣにより温度の経時変化を測定し、そこでの最高温度Ｔｍ（℃）に達する時間ｔｍ〔秒（ｓ）〕を測定する。これらの測定から次の数式（３）により体積熱容量ρＣを求める。
【００１６】
【数３】
式（３）において、αは、次式（４）で求められる熱拡散係数であり、Ｅｉは指数積分である。
【００１８】
【数４】
ヒータＨ配置プローブにおける、熱パルス付与時の温度変化を図３（Ａ）で表され、距離ｒの土壌を介して配置されたセンサー針における温度変化を図３（Ｂ）で表される。
【００２０】
【実施例】
ここでは、本発明を実施例を挙げて説明するが、これは、より本発明を理解し易くするためのものであり、本発明はこれにより限定されないことは当然である。
【００２１】
実施例１
土壌水分量θと電気伝導度σとの相関（検量線）を示す図４の作製。
室内において、既知濃度、０％（●）、２０％（□）及び５０％（×）の汚染物質として想定したエチルアルコールを含む表中水分を砂質土壌に加えて土壌水分量θを変えたサンプルを作成し、時間域反射法（ＴＤＲ法）によりバルク電気伝導度σを測定して図４に示す土壌水分量θと電気伝導度σとの相関（検量線）を作成した。この相関の特徴は、汚染物質の濃度により土壌水分量θと電気伝導度σとの相関が識別できることである。この特性は、原位置被測定土壌における土壌水分量をより正確に測定できる手法と原位置被測定土壌の電気伝導度σとから汚染物質の濃度を知ることができるということである。
【００２２】
土壌水分量θと比誘電率εとの相関（検量線）を示す図５の作製。
室内において、既知濃度、０％（●）、２０％（□）及び５０％（×）の汚染物質として想定したエチルアルコールを含む表中水分を砂質土壌に加えて土壌水分量θを変えたサンプルを作成し、時間域反射法（ＴＤＲ法）により比誘電率εを測定して図５に示す土壌水分量θと比誘電率εとの相関（検量線）を作成した。この相関の特長は、土壌水分量の比較的少ない条件において、ここでは土壌水分量θが０．１ｍ3／ｍ3の近傍において汚染物質を想定したエタノールの濃度の違いがあってもほぼ正確な土壌水分量θの値を知ることができるということである。
因みに、自然土壌における土壌水分量の最大値はほぼ０．３５〜０．４０ｍ３／ｍ３程度である。
【００２３】
土壌水分量θと体積熱容量ρＣ（Ｊ／ｍ３／Ｋ）との相関（検量線）を示す図６の作製。
室内において、既知濃度、０％（●）、２０％（□）及び５０％（×）の汚染物質として想定したエチルアルコールを含む表中水分を粘質土壌に加えて土壌水分量θを変えたサンプルを作成し、双極熱パルス法（Dual−Probe Heat Pulse Method，ＤＰＨＰ）により体積熱容量ρＣを測定して図６に示す土壌水分量θと体積熱容量ρＣとの相関（検量線）を作成した。この相関の特長は、土壌水分量の比較的大きい条件において、ここでは土壌水分量θが０．３ｍ３／ｍ３の近傍において汚染物質を想定したエタノールの濃度の違いがあってもほぼ正確な土壌水分量θの値を知ることができるということである。
【００２４】
原位置被測定土壌の汚染物を想定したのエタノールの存在及びその濃度Ｃの検出
ここでは、実際の測定値を示さないが、前記検出における、前記図４〜６から汚染物に想定したエタノールの濃度を知る方法を説明知る。
先ず、原位置被測定土壌に設置したサーモ−ＴＤＲ法によるプローブＰにより、原位置被測定土壌の体積熱容量ρＣ、比誘電率ε及び電気伝導度σを測定する。これらの測定値の体積熱容量ρＣを前記図６に与えて、また、比誘電率εを前記図５に与えて、相関（検量線）から土壌水分量θ、例えば０．３を知る。
前記手法により知った土壌水分量θと前記原位置被測定土壌を測定して得られた電気伝導度σ、例えば１０（ｍＳ／ｍ）から決定される点（１０、０．３）を前記図４にプロット、例えば○、する。前記プロットした点が汚染物質２０％（容積濃度）の相関（検量線）に近いから、汚染物濃度を２０％（容積濃度）と知ることができる。
前記相関（検量線）は、前記測定原理から、汚染物質として想定したエタノールのみでなく、エタノールと近似の体積熱容量、比誘電率を持つ有機物質、例えばメタノール、アセトニトリルに対してそのまま適用できる。有機塩素系化合物、石油などに対しても前記相関の作成の手法により汚染の有無及び汚染物濃度の推定に適用可能である。
【００２５】
【発明の効果】
以上述べたように、想定される有機汚染物質をある程度知ることができれば、前記手法によりサーモ−ＴＤＲ法を用いて、多くの有機汚染物質を非飽和系において検出でき、有機汚染物質の漏洩地点近傍における監視が可能な手法を提供できたという優れた効果がもたらされる。
【図面の簡単な説明】
【図１】 サーモ−ＴＤＲ法に用いる３針またはロッドからなる３線のプローブ針ＰＲを持ったプローブＰ
【図２】 サーモ−ＴＤＲ法における、時間域反射法（ＴＤＲ法）用の電磁波による比誘電率ε及び電気伝導度σの測定のための同軸ケーブルＣＣと測定器との構造
【図３】 双極熱パルス法におけるヒータＨにおける温度の経時変化（Ａ）と温度センサー針における温度の経時変化（Ｂ）
【図４】 エタノール濃度、０％（●）、２０％（□）及び５０％（×）の既知濃度汚染物質を用いて作成した土壌水分量θと電気伝導度σとの相関（検量線）
【図５】 エタノール濃度、０％（●）、２０％（□）及び５０％（×）の既知濃度汚染物質を用いて作成した土壌水分量θと比誘電率εとの相関（検量線）
【図６】 エタノール濃度、０％（●）、２０％（□）及び５０％（×）の既知濃度汚染物質を用いて作成した土壌水分量θと体積熱容量ρＣ（Ｊ／ｍ３／Ｋ）との相関（検量線）
【符号の説明】
ＰＲ プローブ針 Ｈ 双極熱パルス法用ヒータ ＴＣ サーモカップル
ＣＣ 電磁波伝達同軸ケーブル Ｌ 電磁波伝達電極長 ＰＧ パルス発生器
ＰＥ 電磁波伝達電極 Ｌａ 電極の見かけ状の長さ ＯＳ オシロスコープ[0001]
BACKGROUND OF THE INVENTION
The present invention measures the relative dielectric constant ε and electrical conductivity σ from the measurement of volumetric heat capacity ρ C (J / m 3 / K) by the bipolar heat pulse method and the reflection characteristics of electromagnetic waves by the time domain reflection method (TDR method). Using a standard soil sample with known contaminant concentration and soil moisture content θ by the thermo-TDR method, which can observe each of the above characteristics almost simultaneously using a probe having two or more probe needles in combination with , Correlation between soil water content θ and volumetric heat capacity ρ C (J / m 3 / K), correlation between soil water content θ and relative permittivity ε, and correlation between soil water content θ and electrical conductivity σ The soil moisture content θ from the measured value of the volumetric heat capacity ρ C (J / m 3 / K) or / and the relative dielectric constant ε of the soil to be measured in situ (if this moisture content is contaminated with moisture, And the detected soil water content θ and the time domain reflection method (T The point determined from the electrical conductivity σ of the soil measured in situ by the DR method) is plotted in the correlation between the soil water content θ created using the standard soil sample and the electrical conductivity σ, Contamination of soil with organic liquid substances characterized by detecting the presence and concentration of contaminants in the in-situ measured soil from the correlation between soil water content θ and electrical conductivity σ closest to the plot It relates to a method of detection.
[0002]
[Prior art]
Conventionally, an organic solvent or the like has leaked from an underground storage tank or the like, thereby contaminating the environment. Therefore, it was necessary to monitor such contamination, but as a monitoring means, it was discovered that the groundwater was contaminated for the first time by collecting nearby well water after the leakage reached the groundwater surface. I could only do it.
On the other hand, for example, October 13, 2000: Tohoku branch of the Japan Society of Agricultural Civil Engineers 45th Research Presentation Lecture Summary “Attempt to measure the content of NAPL (Non-Aqueous Phase Liquid) in saturated soil by the TDR method” In the following (Reference 1), the presenters used kerosene as a non-aqueous phase liquid (L-NAPL) having a specific gravity smaller than that of water, and used a water-kerosene saturated two-phase column penetration test. Is considering the use of a TDR moisture meter as a non-destructive method for measuring the kerosene content of specimens.
[0003]
The measurement method uses the fact that an empirical function relationship is established between the apparent relative dielectric constant of soil and the amount of water. The empirical function relationship is that the relative permittivity of NAPL is almost the same as that of soil particles, etc. with respect to the relative permittivity of water 80, and if present in the soil, NAPL can be regarded as homogeneous with soil particles. Therefore, the apparent relative permittivity of the soil with the porosity n is measured with a TDR moisture meter, and the above measurement ratio is correlated with the correlation between the relative permittivity and the volume moisture content θ W prepared in advance using the soil with the known volume moisture content. When the volumetric water content θ W is obtained by applying the dielectric constant, the NAPL content is obtained from the relationship of NAPL content θ oil = n−θ W. However, since the above principle is based on a water-NAPL saturated two-phase system, it can only be applied under saturated water conditions. Therefore, the organic solvent leaked from the storage tank can only be detected after reaching the groundwater surface. Therefore, it does not help to solve the problem of detecting the leakage of organic solvent in the vicinity of the leakage area.
[0004]
The apparent relative permittivity of soil is a function of soil moisture content, organic solvent permittivity, existence form, etc., and the apparent permittivity of soil depends on the water content of organic solvent that fills the soil gap. Since the correlation is different, it is impossible to apply the method described in the above literature to unsaturated soil as it is.
[0005]
On the other hand, the present inventors found that volumetric water content theta, electrical conductivity sigma, the dielectric constant of the apparent epsilon, thermo can be almost simultaneously measured and volumetric heat capacity [rho C - time domain reflection method (Thermo-Time Domain Reflectometry, Thermo-TDR) method (Ren, T., K. Noborio, and R. Horton. 1999. Measuring soil water content, electrical conductivity, and thermal properties with a thermo-time domain reflectometry probe. Soil Sci. Soc. Am. J. 63: 450-457. The principle is that the volume moisture content θ, the electrical conductivity σ, and the apparent volume are measured by TDR method on a measurement probe composed of two or more probe needles in the above-mentioned document. The dielectric constant ε can be measured at the same time and the function is provided. At the same time, the volume moisture content θ, the volume heat capacity ρ C, etc. are measured on at least two probe needles by the dual-probe heat pulse method (DPHP). It is possible to obtain the volumetric liquid content (q) and electric conductivity (s), apparent dielectric constant ε, and volumetric heat capacity of the soil by a small time interval, in other words, almost the same time. Measure.
[0006]
In the literature 2, using the measurement probe, the correlation characteristics between the volumetric water content θ and the electrical conductivity σ using salt water, the correlation between the volumetric water content θ and the apparent relative dielectric constant ε, and the like are measured. The measurement probe can be applied to the measurement of volume liquid content (q) and electrical conductivity (s), apparent dielectric constant ε, and soil thermal properties almost simultaneously, and the correlation between volume moisture content θ and electrical conductivity σ. Although the characteristics are good, it is mentioned that a separate calibration curve is required for the correlation between the soil water content θ and the relative dielectric constant ε.
However, there is no mention of application to a method for detecting contamination and measuring the degree of contamination of organic solvents and the like.
[0007]
Since it takes a lot of time and money to remove pollutants after reaching the groundwater, the development of sensors that detect leaks in unsaturated soil layers is desired early, and pollutants reach the groundwater surface. If it is possible to detect at an early stage, it is possible to prevent groundwater contamination or to keep it to a minimum.
[0008]
[Problems to be solved by the invention]
Therefore, the subject of this invention is providing the method of detecting the leak to soil, such as an organic solvent, in the vicinity of a leak point.
The present inventor is based on the soil monitoring technique by the thermo-TDR method disclosed in the literature 2, and in order to be able to detect leakage of organic solvent or the like to the soil in the vicinity of the leakage point, In order to establish a method capable of detecting at least the leakage of contaminants and detecting the concentration of the contaminants even if not a saturated system, the volume moisture content θ can be measured almost simultaneously by the thermo-TDR method. electrical conductivity sigma, the dielectric constant of the apparent epsilon, and by effectively using the respective correlation volumetric heat capacity [rho C, techniques which can solve the above problems is considered that it would be able to establish.
Therefore, the volumetric heat capacity ρ C , relative permittivity ε, and electrical conductivity σ of a standard soil sample having a known contaminant concentration and soil moisture content θ were measured, and the soil moisture was calculated from the characteristics measured almost simultaneously. The correlation between the quantity θ and the volumetric heat capacity ρ C (J / m 3 / K), the correlation between the soil water content θ and the relative dielectric constant ε, and the correlation between the soil water content θ and the electrical conductivity σ were prepared. The correlation between the volumetric heat capacity ρ C (J / m 3 / K), relative dielectric constant ε, electrical conductivity σ, and soil moisture content θ with respect to the difference in contaminant concentration and soil moisture content in each of the above correlations. And using such properties, it is found that even in the unsaturated system of contaminants, not only the presence or absence of leakage of the contaminants into the soil, but also the approximate concentration of contaminants in soil moisture can be measured, The said subject of this invention was able to be solved.
In the present specification, “substantially simultaneous” means that two measurements are possible after a very short time, although not simultaneously.
[0009]
[Means for Solving the Problems]
The present invention measures the relative dielectric constant ε and electrical conductivity σ from the measurement of volumetric heat capacity ρ C (J / m 3 / K) by the bipolar heat pulse method and the reflection characteristics of electromagnetic waves by the time domain reflection method (TDR method). Using a probe with two or more probe needles that can be combined with the above, each characteristic of a standard soil sample with a known contaminant concentration and soil moisture content θ is measured almost simultaneously. A correlation between θ and volumetric heat capacity ρ C (J / m 3 / K), a correlation between soil water content θ and relative permittivity ε, and a correlation between soil water content θ and electrical conductivity σ were prepared, and in situ. Soil moisture content θ from the measured value of volumetric heat capacity ρ C (J / m 3 / K) or / and relative permittivity ε of the soil to be measured (this moisture content includes the contaminants in the moisture, if any) The detected soil water content θ and the in-situ measured soil electrical conductivity σ. In the correlation between the soil water content θ and the electrical conductivity σ created using the standard soil sample, the correlation between the soil water content θ and the electrical conductivity σ closest to the plot is plotted. It is a method for detecting soil contamination by an organic liquid substance, characterized by detecting the presence of a contaminant in the in-situ measured soil and the concentration C of the contaminant from the contaminant concentration in the water.
[0010]
Preferably, when the water content is relatively large, the soil water content θ is plotted as the value of the soil water content θ when plotting the water content of the in-situ measured soil on the correlation between the soil water content θ and the electrical conductivity σ. When the soil moisture value obtained from the correlation between the amount θ and the volumetric heat capacity ρ C (J / m 3 / K) is used, and the moisture amount is relatively small, the soil moisture amount θ and the relative dielectric constant ε A method for detecting the presence of contaminants in the soil to be measured and the concentration C of the contaminants, more preferably using bipolar heat. The probe needle with the temperature sensor in the pulse method and / or the reflection of electromagnetic waves by the time domain reflection method (TDR method) and the electrical conductivity measurement needle were set to 2 or more, and the soil area to be measured was expanded by the number of probe needles. The presence and presence of contaminants in each of the measured soils This is a method for detecting the concentration C of the contaminant, and more preferably, the change in the apparent length observed from the reflection points of the electromagnetic waves at the start and end of the probe needle appearing on the oscillograph. [La / L (actual probe length)] A method for detecting the presence of contaminants and the concentration C of contaminants in each of the soils to be measured, which is calculated by knowing as a function of 2. is there.
[0011]
[Embodiments of the present invention]
The present invention will be described in more detail.
A. The features of the present invention will be described with reference to the drawings.
FIG. 1 includes a probe P having a three-wire probe needle PR composed of three needles or a rod. At least two wires of the probe needle include a heater H for a bipolar heat pulse method and a pulse heating by the heater. A temperature measuring device, such as a thermocouple TC or a thermistor, is arranged to measure the change in temperature over time, and at least one line is used for measuring the relative permittivity ε and the electrical conductivity σ by electromagnetic waves for the time domain reflection method (TDR method). It is designed to have a structure in which an electromagnetic wave transmission electrode PE having a length L connected to the coaxial cable CC is arranged.
The coaxial cable CC for measuring the relative permittivity ε and the electric conductivity σ by the electromagnetic wave for the time domain reflection method (TDR method) includes a pulse generator PG and an electromagnetic wave transmission electrode having a relative velocity Vp of the electromagnetic wave. The structure shown in FIG. 2 is designed to detect an electromagnetic wave reflected from the electrode, display the apparent length La of the electrode, and connect to an oscilloscope OS incorporating an information processing device.
The relative dielectric constant ε and the electrical conductivity σ are calculated by the following formulas (1) and (2).
[0012]
[Expression 1]
[Expression 2]
In the equation (2), K p is the shape factor (1 / m) of the probe, Z u is the output impedance (Ω) of the measuring instrument, and ρ ∞ is the reflection coefficient of the electromagnetic wave at a position sufficiently away from the probe end.
[0015]
By a bipolar heat pulse method, a heat pulse, for example, a heat pulse of t o = 15 seconds, is applied by an electric power q [W / m (min)] applied to the heater H, and this is set to an appropriate soil thickness r (m). through and placed probes (temperature sensor needle) in the arranged temperature measuring device, for example, the time course of temperature was measured by thermocouple TC, the maximum temperature T m time to reach (° C.) t m [sec therein ( s)] is measured. From these measurements, the volumetric heat capacity ρ C is determined by the following formula (3).
[0016]
[Equation 3]
In Expression (3), α is a thermal diffusion coefficient obtained by the following Expression (4), and Ei is exponential integration.
[0018]
[Expression 4]
The temperature change at the time of applying the heat pulse in the heater H arrangement probe is shown in FIG. 3A, and the temperature change in the sensor needle arranged through the soil of the distance r is shown in FIG.
[0020]
【Example】
Here, the present invention will be described with reference to examples. However, this is for easier understanding of the present invention, and the present invention is naturally not limited thereto.
[0021]
Example 1
Production of FIG. 4 which shows the correlation (calibration curve) of soil water content (theta) and electrical conductivity (sigma).
In the room, soil moisture content θ was changed by adding moisture in the table containing ethyl alcohol assumed as pollutants of known concentration, 0% (●), 20% (□) and 50% (×) to sandy soil. A sample was prepared, and bulk electrical conductivity σ was measured by a time domain reflection method (TDR method) to create a correlation (calibration curve) between the soil water content θ and the electrical conductivity σ shown in FIG. The feature of this correlation is that the correlation between the soil water content θ and the electrical conductivity σ can be identified by the concentration of the pollutant. This characteristic is that the concentration of the pollutant can be known from the method that can measure the soil moisture content in the in-situ measured soil more accurately and the electrical conductivity σ of the in-situ measured soil.
[0022]
FIG. 5 shows the correlation (calibration curve) between the soil water content θ and the relative dielectric constant ε.
In the room, soil moisture content θ was changed by adding moisture in the table containing ethyl alcohol assumed as pollutants of known concentration, 0% (●), 20% (□) and 50% (×) to sandy soil. A sample was prepared, and the relative permittivity ε was measured by a time domain reflection method (TDR method) to create a correlation (calibration curve) between the soil water content θ and the relative permittivity ε shown in FIG. The feature of this correlation is that it is almost accurate even when there is a difference in the concentration of ethanol assuming a pollutant when the soil moisture content is near 0.1 m 3 / m 3 under conditions where the soil moisture content is relatively small. It means that the value of soil water content θ can be known.
Incidentally, the maximum value of soil moisture in the natural soil is approximately 0.35~0.40m 3 / m 3 approximately.
[0023]
Production of FIG. 6 which shows the correlation (calibration curve) of soil water content (theta) and volumetric heat capacity (rho) C (J / m < 3 > / K).
In the room, the soil moisture content θ was changed by adding moisture in the table containing ethyl alcohol assumed as a contaminant of known concentration, 0% (●), 20% (□) and 50% (×) to the sticky soil. create a sample, creating a bipolar heat pulse method (Dual-Probe heat pulse method, DPHP) correlation by measuring the volumetric heat capacity [rho C and soil moisture θ and the volume heat capacity [rho C shown in FIG. 6 by the (calibration curve) did. The feature of this correlation is that it is almost accurate even when there is a difference in the concentration of ethanol in the vicinity of the soil water content θ of 0.3 m 3 / m 3 under the condition that the soil water content is relatively large. It means that the value of soil water content θ can be known.
[0024]
Detection of the presence of ethanol and its concentration C assuming soil contamination in the in-situ measured soil Here, actual measurement values are not shown, but in the detection, the ethanol concentration assumed from FIG. Explain how to know the concentration.
First, the volume heat capacity ρ C , relative permittivity ε, and electric conductivity σ of the in-situ measured soil are measured by the probe P by the thermo-TDR method installed in the in-situ measured soil. The volumetric heat capacity ρ C of these measured values is given in FIG. 6 and the relative dielectric constant ε is given in FIG. 5, and the soil water content θ, for example 0.3, is known from the correlation (calibration curve).
The point (10, 0.3) determined from the soil water content θ obtained by the method and the electrical conductivity σ obtained by measuring the in-situ measured soil, for example, 10 (mS / m) 4 is a plot, for example, ◯. Since the plotted point is close to the correlation (calibration curve) of the
The correlation (calibration curve) can be applied as it is not only to ethanol assumed as a contaminant from the measurement principle, but also to an organic substance having a volumetric heat capacity and relative dielectric constant similar to ethanol, such as methanol and acetonitrile. The present invention can also be applied to the estimation of the presence or absence of contamination and the concentration of contaminants for organochlorine compounds, petroleum, and the like by the method for creating the correlation.
[0025]
【The invention's effect】
As described above, if the expected organic pollutants can be known to a certain extent, many organic pollutants can be detected in the unsaturated system by using the thermo-TDR method, and the vicinity of the organic pollutant leakage point It is possible to provide an excellent effect that a method capable of monitoring in can be provided.
[Brief description of the drawings]
FIG. 1 shows a probe P having a three-wire probe needle PR composed of three needles or a rod used in a thermo-TDR method.
FIG. 2 shows a structure of a coaxial cable CC and a measuring instrument for measuring relative permittivity ε and electric conductivity σ by electromagnetic waves for time domain reflection method (TDR method) in the thermo-TDR method. Temporal change of temperature in heater H in heat pulse method (A) and Temporal change of temperature in temperature sensor needle (B)
[FIG. 4] Correlation between soil water content θ and electrical conductivity σ prepared using known concentrations of contaminants with ethanol concentrations of 0% (●), 20% (□) and 50% (×) (calibration curve).
FIG. 5: Correlation between soil water content θ and relative dielectric constant ε (calibration curve) prepared using known concentrations of contaminants with ethanol concentrations of 0% (●), 20% (□), and 50% (×).
FIG. 6 shows soil moisture content θ and volumetric heat capacity ρ C (J / m 3 / K) prepared using known concentrations of contaminants with ethanol concentrations of 0% (●), 20% (□) and 50% (×). ) (Calibration curve)
[Explanation of symbols]
PR probe needle H heater for bipolar heat pulse method TC thermocouple CC electromagnetic transmission coaxial cable L electromagnetic transmission electrode length PG pulse generator PE electromagnetic transmission electrode La apparent length of electrode OS oscilloscope
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| JP4644806B2 (en) * | 2005-04-28 | 2011-03-09 | 国立大学法人島根大学 | Soil water movement speed deriving method and soil water movement speed measuring device |
| JP4929464B2 (en) * | 2007-02-28 | 2012-05-09 | 国立大学法人島根大学 | Soil management method |
| KR101011952B1 (en) | 2008-11-10 | 2011-02-09 | 대한민국 | Soil conductivity tester and method for measuring soil conductivity |
| CN108287368A (en) * | 2018-03-09 | 2018-07-17 | 上海岩土工程勘察设计研究院有限公司 | Polluted Soil all standing detection method based on complex geophysical prospecting and its arrangement of measuring-line structure |
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| CN116990357B (en) * | 2023-09-28 | 2023-12-12 | 湖南省交通规划勘察设计院有限公司 | Soil property in-situ test system and method based on dielectric constant |
| CN117368441A (en) * | 2023-10-12 | 2024-01-09 | 北京建工环境修复股份有限公司 | Layout method, identification method and related devices of hazardous characteristics identification points of contaminated soil |
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