三氯乙烯地下水污染場址整治後期傳輸行為分析¬-應用開源FreeFEM++有限元素模式架構;Numerical analysis of TCE transport in a groundwater post remediation site: implementation of open source finite element module FreeFem++

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Title:	三氯乙烯地下水污染場址整治後期傳輸行為分析¬-應用開源FreeFEM++有限元素模式架構;Numerical analysis of TCE transport in a groundwater post remediation site: implementation of open source finite element module FreeFem++
Authors:	張家偉;Chang,Chia-Wei
Contributors:	應用地質研究所
Keywords:	有限元素法;污染傳輸模式;一般克利金法;三氯乙烯;FreeFEM++;finite element method;contaminant transport;ordinary kriging;TCE;FreeFEM++
Date:	2015-08-24
Issue Date:	2015-09-23 15:12:47 (UTC+8)
Publisher:	國立中央大學
Abstract:	數值模式的發展日新月異，已廣泛應用到許多領域中，有限元素方法是一個功能強大的數值方法，可以靈活處理許多複雜的問題。但有限元素法的模式開發包括複雜程式撰寫、除錯與模式最佳化驗證等，需投入大量資源提高程式開發效率。本研究應用高階計算偏微分方程的模組FreeFEM++ （Free Finite Element ++），透過物理控制方程的變分推導，編寫包含吸附與自然衰減特性的地下水與污染傳輸模式。模式經與MODFLOW與解析解驗證結果顯示水流與污染傳輸擬合良好，方均根誤差（RMSE）分別為0.003 m與0.0784 mg/L。模式應用於實際的三氯乙烯（TCE）污染場址，本研究將現地水文地質參數的一般克利金法（ordinary kriging）統計分析結果代入模式中率定，運用場址過去豐富的觀測數據與模式結果交互驗證。結果顯示污染團濃度分布與觀測結果擬合， RMSE介於0.1~0.69 mg/L，證實本研究所開發的FreeFEM++地下水流與污染傳輸模式可適切反應污染場址內污染團之移動機制。最後本研究評估自然衰減和抽水兩種整治方法應用於整治場址後期的整治效益，分析結果顯示場址TCE濃度大於 0.1 mg/L時，使用抽水整治效果較顯著，而且在污染團下游抽水效益最高，但濃度低於0.05mg/L時，兩種方法的效益會趨於一致。;Numerical models have been widely applied to many research fields. The finite element method is a powerful numerical method that can solve for complex problems. However, the model developers need to devote much resources to complete complex codes, perform debugging and code optimizing. The completed model typically requires systematical testing and verification before implementations. The objectives of the study are to employ an open source module FreeFem++ to efficiently develop a finite element groundwater flow and transport model, validate the developed model, calibrate and implement the developed mode for a site-specific problem. This study used MODFLOW and a analytical solution to evaluate the accuracy of the developed model for groundwater flow and contaminant transport. The model is then applied to a practical trichlorethylene (TCE) contaminated site. Geostatistical ordinary kriging method was used to analysis the hydrogeological parameters. The results of the kriged parameters are then employed in the model for site-specific calibrations. Based on the extensive observations and remediation data from the study site, the simulation results showed reasonably the behavior of plume migration. The RMSE of concentration is from 0.1 mg/L to 0.69 mg/L depending on the locations of wells. This study used the developed model to assess the strategies of natural decay and pump and treat remediations. The simulation results indicated that pumping remediation method is effective in the downstram when TCE concentration higher than 0.1 mg/L. However, the remediation efficiency of pump and treat reduces with the low TCE concentration (<0.1mg/L). If the concentration in aquifer lower than 0.05 mg/L, the long term operations of pump and treat show results same as the natural attenuation.
Appears in Collections:	[Graduate Institute of Applied Geology] Electronic Thesis & Dissertation

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