自然界中的地下水含水層系統為多種不同成分的介質組成之系統，因不同介質有不同的物理與化學性質，使傳輸行為變得複雜。另外，常見的地下水污染物會在傳輸過程中發生衰變作用或降解反應，比如含氯有機溶劑、核廢料、氨氮肥料等。因此，單區域單一物種污染物之解析解模式已不敷使用。多層多物種耦合一階序列衰變反應之移流–延散方程組為用來理解多層介質系統傳輸機制之有效率的工具。本研究發展多區域多物種反應傳輸解析解模式，模擬多物種污染物在多層介質地下水系統中的傳輸行為。研究中傳輸方程式分別以第三類定濃度入流邊界及變濃度入流邊界求解，並利用Laplace轉換消除時間偏微分項，撰寫FORTRAN程式執行解析解的逆轉換以及運算。所得之解析解比對Laplace轉換有限差分法(Laplace transform finite difference,LTFD)求得之數值解，並與過去文獻的結果比較後相符，驗證了本篇解析解模式的正確性。本篇解析解能應用於調查不同傳輸機制與行為對溶質分布的影響，對於調查污染物及應用於污染防治有所貢獻。

The transport behaviors through layered groundwater system are complicated due to the different physical and chemical properties of different materials of each layer. Transport processes of some contaminants, such as chlorinated solvents, radionuclides, and nitrogen fertilizers involve a series of sequential first-order decay chain reactions, and during migrations of decaying contaminants may sequentially form and move downstream with elevated concentrations. As the result, single-species analytical models do not permit transport behaviors of successor species of these decaying contaminants to be evaluated. A set of advection-dispersion equations couple with first-order sequential decay chain reactions in multi-domain system are efficient tools to understand how the various mechanisms affects reactive solute transport through nonhomogeneous layered geological media. This study presents an analytical model for multi-species transport in multi-domain system to simulate the transport behavior of degradable contaminants. The analytical solutions are solved for both the first-type and third-type inlet boundary conditions and derived with the aid of Laplace transform. The solutions are compared with the results of the numerical model which are solved by using the advanced Laplace transform finite difference method. The developed multi-domain analytical model can be applied to investigate how transport processes and mechanisms influence the multi-species solute transport in the multi-layer groundwater system.

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