遲滯效應及尺度原則對NAPLs於孔隙介質中傳輸模擬之影響

Abstract

隨著台灣的電子、電鍍、石化工業在近年來的急速發展，使得工業廢水及所用之有機溶劑日益增加，由於此種廢液於水中的溶解度甚低並在自然界中不易被分解，其污染能力比水溶性污染物更為嚴重，一旦不小心或使用不當而滲入含水層時，極易導致地下水污染，故研究NAPLs於地表下的傳輸分佈進而解決此類污染問題是刻不容緩的。 本文運用最新的NAPL模擬模式(NAPL Simulator, Guarnaccia and Pinder, 1997)，並以一虛擬砂箱系統，依據實驗所得之保持特性曲線資料(鄭淑華, 1997)(k-S-P關係)，探討遲滯效應與尺度原則對孔隙介質中之NAPLs傳輸模擬的影響。由模擬結果顯示，不論是DNAPL或是LNAPL，忽略遲滯效應模擬所得之NAPL注入量均大於考慮遲滯效應之注入量，並且分佈範圍較廣；另外初始水分含量之分佈及尺度原則的正確性均對模擬結果有相當影響，其中尤以尺度原則之影響最為顯著。以空氣-水為參考流體對時，經由尺度原則所求得其它流體對之特性曲線與實際實驗值之誤差為最小，另由DNAPL的模擬結果顯示，不論是否有考慮遲滯效應，以空氣-水為參考流體對所推估的NAPL注入量也最多，因此，若欲應用尺度原則於NAPLs之模擬，以GW為參考流體對應是保守而合理的選擇。

The increasing amount of organic solvents used in industry has elevated the risk of leakage or spilling of organic compounds. In addition to having a low solubility in water, most organic solvents are difficult to decompose naturally. While leaking into the aquifer, the organic compounds can more seriously contaminate the aquifer than other high soluble pollutants do. Therefore, understanding the fate and transport mechanism of the organic compounds in aquifer is a relevant task. This study investigates how hysteresis and scaling rule affect simulation of the transport of NAPLs in a porous media by using a simulation model, NAPL Simulator (Guarnaccia and Pinder, 1997), and a data set obtained by a series of characteristic curve experiments on multiphase systems. Scaling rule analysis of the experimental data reveals that, by using the characteristic-curve of the gas-water phases as a referenced curve, the calculated characteristic-curve for other phases pairs have the minimum error to the experimental data. Therefore, the characteristic curve of the gas-water phases is a reasonable referenced curve when applying the scaling rule to NAPLs simulation. Simulation results also point towards several important findings. For LNAPLs and DNAPLs, larger amounts of NAPLs enter the hypothesis system when omitting the hystersis effects than when considering the hystersis. The initial water content and the accuracy of the scaling rule also affect the simulation results and the last one most significantly impact the pollutants distribution. When simulating the DNAPLs, regardless of whether the hystersis effects is considered, simulation results indicate a larger amount of pollutants entering the system when selecting the characteristic curve of gas-water phases as a referenced curve than that based on other characteristic curves. Simulating NAPLs transport is a complicated task and results in this study provide a valuable reference for conducting a field simulation on NAPLs transport.