結合零價鐵 (ZVI) 的滲透性反應牆 (PRB) 是一種用於處理現地地下水污染物的技術。 PRB內部發生的化學反應與礦物的二次沉澱，將導致PRB孔隙度降低。當孔隙率降低時，將改變流徑的方向、停留的時間與分路作用的產生。本研究使用 THMC 軟件（一種熱-水文-力學-化學 (THMC) 多相藕合的數值模型）通過流動建模和 PRB 內發生的化學反應來推估孔隙率降低情況。根據地下水流模型，PRB 中的滲透率高於鄰近的含水層材料，允許水流快速地通過，儘管過程中污染物遭移除，地下水的水文地質特性仍假設維持不變。模型結果表明孔隙率損失在入口面 (0.0138) 最為顯著，隨後在經由PRB 的入口處後下降並穩定在 0.2米。文石、菱鐵礦和氫氧化亞鐵可將孔隙率降低 99% 以上。此模式透過結果進一步說明進入地下水中碳酸氫鹽和硫酸鹽的高、低濃度對於孔隙率降低的影響。其中碳酸氫鹽的濃度對沉澱碳酸鹽礦物的形成則對於孔隙率降低有顯著影響。此外其中反應速率係數也影響孔隙率的下降，像是厭氧鐵腐蝕速率係數對於孔隙度下降呈現高度的敏感性，主要是因為鐵腐蝕影響Fe2+、OH-的形成和Fe(OH)2的沉澱作用。本研究成功透過THMC 模擬在 PRB 中孔隙率的降低，對於預測 PRB 中礦物沉澱造成孔隙率損失時應考慮的因素與分析孔隙率隨時間降低的變化有很大的幫助。;Permeable reactive barrier (PRB) involving zero-valent iron (ZVI) is an in-situ technique for treating groundwater contaminants. Chemical reactions take place inside the PRB, promoting secondary mineral precipitation and leading to a decrease in the porosity of the PRB. When the porosity reduction, flow path reorientation, residence time changes, and bypassing occur. This study used THMC software, a numerical model of Thermal-Hydrology-Mechanical-Chemical (THMC) through multiple phases, to determine porosity reduction through flow modeling and the chemical reactions occurring within the PRB. According to the groundwater flow model, PRB has a permeability higher than the neighbouring aquifer materials, allowing water to pass through quickly and preserving the groundwater′s hydrogeology despite removing contaminants. The model result indicates that porosity loss is most significant at the entrance face (0.0138), followed by a fall and stabilization after 0.2 m at the PRB entrance. Aragonite, siderite, and ferrous hydroxide reduce porosity by more than 99%. This model highlights the relative effect of concentration by illustrating porosity losses for the high and low levels of bicarbonate and sulfate in the entering groundwater. The concentration of bicarbonate has a significant impact on the reduced porosity caused by the formation of precipitated carbonate minerals. The rate coefficient also influences porous reduction, while the anaerobic iron corrosion rate coefficient is highly sensitive to porous reduction due to iron corrosion influencing the formation of Fe2+, OH-, and the precipitation of Fe(OH)2. Therefore, this research aims to use THMC to simulate the decrease of porosity in PRB, investigate the factors that should be considered when predicting porosity loss from mineral clogging in PRB and analyze the reduction of porosity over time.
