應用微模型於接觸角及流體對間置換機制之研究

Abstract

非水相液（Non-Aqueous-Phase-Liquid, NAPL）雖然於水中溶解度很低，惟其在自然界中不易被分解，且部分非水相液具有毒性。因此，若不慎滲漏入土壤中，將對環境形成重大威脅，而非水相液、水及空氣等在土壤孔隙中的置換機制，為影響NAPL在土層中傳輸及宿命的重要因素。 傳統上以室內實驗探討孔隙介質中水或其他污染物的流動現象，多以砂箱進行，惟其無法直接觀察水、污染物及空氣等共存於孔隙中時微觀的互相置換過程，因此本研究以可透視微模型，配合數位影像分析觀察多孔介質中流體對間的置換現象，並由不同流體對之接觸角實驗，探討排退與汲取階段的接觸角是否一致，流體之進入先後順序是否會影響接觸角，再將所求得之各流體對之接觸角代入理論置換機制公式，與毛細壓力-飽和度實驗中所觀察到之流體對間取代的影像比較分析，發現理論置換機制公式所推估之毛細壓力與實驗中發生置換時之系統毛細壓力及現象大致吻合。於本研究中可以釐清各種置換機制與其發生的過程，未來更可以本研究為基礎發展理論模式，以推求更準確的毛細壓力-飽和度曲線。

Although the solubility of non-aqueous-phase-liquid (NAPL) is low in water, decomposing NAPL is extremely difficult and portions of NAPL are toxic. Consequently, the accidental leakages of NAPL into groundwater due to improper storage have threatened the surrounding environment. The displacement mechanics of NAPL, water and air in the porous media influence the outcome and transport process of NAPL in subsurface, making this an extremely important environmental issue. Conventional experimentation methods consider water or other contaminants fluid in porous media that always proceeds with sandy tank. However, the microscopic displacement process directly when water, contaminants and air are in a porous media simultaneously, has not been observed. Therefore, this study using transparent micro-model accompanied with digital image analysis attempts not only to observe fluids displacement in a porous media, but also to determine whether the contact angles are the same at drainage and imbibitions process. The displacement formulas are used to compare and analyze the displacement image of fluids in capillary pressure-saturation experiment. Results of this study clearly demonstrate the various forms of displacement mechanics and its occurrence, and can also help to develop a numerical model so that a more accurate capillary pressure-saturation curve can be estimated.