| 摘要: | 由於土壤與地下水污染物和整治藥劑作用範圍在地下難以界定，因此，本研究嘗試引入地球物理探勘技術中的自然電位法（Self-Potential Method, SP），期能以地下水污染和整治藥劑於土壤中擴散產生的流動電位（Streaming Potential）做為監測的指標。本文在研究場址佈下兩條相互垂直的測線，將原始自然電位觀測數據中的直流地電阻法施測效應、降雨效應從資料預處理中消除，並以中位數和四分位差作為資料篩選以及品質的評估，最後於Matlab©應用與改寫André Revil等人開發的SP2DINV，解釋自然電位法靈敏度和探測範圍，並逆推演算每日的自然電位剖面。首先，為了探討本自然電位監測系統探測實際電流源的分布，以砂箱實驗比較三種電極陣列法於兩種已知電流源分布的探測能力，再討論有無埋藏金屬導體對自然電位的影響，得到表土暨井下陣列法具有較佳的解析能力。並以飽和食鹽水灌注的砂箱實驗，以逆推自然電位剖面探討流動電位的分布，以驗證研究場址的監測結果，得到流體源頭為負電位；入滲前緣為正電位的特徵。在污染場址的監測中，從自然電位日變化剖面劃定兩次不同區域的整治藥劑作用範圍，並以上升的局部電位估算視地下水流速，估算值與區域的流速測定吻合。此外，從每日自然電位剖面的電位特徵與電流分布，可判定近地表的人造構造物、北北東的地下水流方向，以及推測污染物的擴散前緣。並且以一維近似的研究方法，從每小時累計雨量與近地表流動電位估算流電係數，透過經驗公式計算後得到地下水的導電率，計算值與實際測定值相近。最後，透過氣象局的雨量觀測資料以及研究場址現地場勘，探討降雨事件、雷擊事件、直流地電阻法施測、地形以及地表建築物對於自然電位的影響。;In this study, we have proposed the use of time-lapse SP (Self-Potential) monitoring system to investigate remediation reagents injection and rainfall effect at the soil and groundwater contaminated site, located in Yung Kang, Taiwan. We set up two mutually perpendicular survey lines to continuously record the SP data at a sampling rate of 25 Hz. By averaging 1 day hourly SP median data, we calculate the time-lapse SPT (Self-Potential Tomography) with a published code SP2DINV every day, and get the following results. First, in order to prove the SP results at the soil and groundwater contaminated site, we conduct 12 sandbox experiments to compare the detecting ability of 3 SP arrays with 2 known current source, and discuss the influence from buried metal wire. We also carry on a saline injection to demonstrate the pattern of streaming potential. And from the synthetic test, we define the sensitivity of SPTs and demonstrate the ability to detect SP. Second, by analyzing the SPTs variation from 13 to 18 October 2015 and from 23 to 25 November 2015, SP monitoring system successfully monitor the remediation reagents injection and evaluate the Apparent Groundwater Velocity. Third, making use of interpolation scheme, this study filter the rainfall effect out of the raw SP data, then show the SP response to the precipitation, and evaluate the Apparent Groundwater Velocity and Streaming Potential Coupling Coefficient. Forth, by observing the positive and negative electric potential distributions in both N-S and E-W SPTs, we determine that the regional groundwater flow direction is in NNE and infer that the forefront of contamination is at 20m. Furthermore, in the daily SPTs, there are some artificial structures at a depth of circa 10 m. |
