移流-延散方程式廣泛應用描述及預測地下溶質傳輸。延散係數為移流-延散方程式中的關鍵參數，可由追蹤劑試驗決定。除了縱向延散係數之外，側向延散係數也是影響含水層中污染團形狀的控制因子。因此在預測污染物移動時，須同時獲得縱向與側向延散資料。現地三環入滲追蹤劑試驗為量測表土層的縱向及側向延散係數。然而如文獻所載，延散會隨著溶質移動的距離而增加。其原因為孔隙水流速隨空間地質異質性所造成。本研究將發展具尺度延散之三環入滲追蹤劑試驗解析數學模式。解析數學模式發展將藉由連續使用Laplace 及有限Hankel 轉換達成。此外本計畫將執行兩個不同土壤性質的現地試驗來驗證現地入滲追蹤劑試驗的適用性。發展的數學模式將可分析不同觀測位置的暫態濃度穿透曲線來決定縱向及側向延散係數。 ; The advection-dispersion equation (ADE) is widely used to describe and predict the subsurface solute transport. Dispersion coefficients are the key parameters for ADE and conventionally determined in field using tracer tests. In addition to longitudinal dispersion coefficient, transverse dispersion coefficients is also an important control factor affecting the shape of contaminant plume in two-dimensional mass transport in an aquifer. Therefore, it is important to have some knowledge of the transverse dispersion coefficient as well as he longitudinal dispersion coefficients. In-situ triple-ring infiltration tracer test has been proposed to measure the constant longitudinal and transverse dispersion coefficients in top-soil. However, as is frequently cited, dispersivity increases with solute travel distance in the subsurface. This behavior has been attributed to the inherent spatial variation of the pore water velocity in geological porous media. In this project we attempt to develop the analytical models for describing solute transport in an in-situ infiltration tracer test with scale-dependent dispersion. The analytical approach is achieved d by successively applying the Laplace and finite Hankel transforms. In addition, two field tests at two sites with different soil materials will be carried out to demonstrate the validity of the in-situ infiltration tracer test. The developed analytical models will be used for simultaneously determining the longitudinal and transverse dispersivities based on analysis of the transient concentration breakthrough curves at the different observation locations. ; 研究期間 9808 ~ 9907
