孔流速度對未飽和土層中溶質傳輸之影響

THE INFLUENCE OF PORE WATER VELOCITY ON SOLUTE TRANSPORT IN UNSATURATED SOILS

蔡清標(Ching-Piao Tsai) ； 蔡志勇(Chih-Yung Tsai)

《中華水土保持學報》 25卷2期 (1994/06) Pp. 61-71

https://doi.org/10.29417/JCSWC.199406_25(2).0001

摘要

汚染源通常先流經未飽和含水層後再汚染地下水源；故瞭解汚染溶質在未飽和含水層中之傳輸特性，將有助於瞭解地下水源受汚染的可能性。本文係引用冪級數展開及數值法解析含垂直入滲項之一維垂直水流及溶質傳輸方程式，在溶質傳輸方程式中的延散係數，本文以土壤中孔流速度之函數表之，以探討其在不同土壤中對溶質傳輸的影響。解析過程中，土壤之水力傳導度及水土擴散係數，則以水分張力曲線求之。由本文之解析結果，顯示土壤中的孔流速度及入滲效應對溶質傳輸有顯著的影響，土壤中孔流速度的影響，在傳輸的初期顯得重要，且以水力傳導度較大之土壤的影響時間較長；而入滲效應隨時間的增加而愈顯重要，且亦以水力傳導度較大之粗顆粒土壤爲顯著。

關鍵字

延散係數 ； 孔流速度 ； 水土擴散係數 ； 水分張力曲線

並列摘要

The vertical transport of solute in unsaturated soils influenced by the pore water velocity is investigated in this study. The methods of power series expansion and numerical scheme are extended to solve the vertical one-dimensional flow equation and the solute transport equation. The dispersion coefficient in the solute transport equation is considered as a function of pore water velocity instead of water content. The parameters of soils, such as soil-water diffusivity and hydraulic-conductivity, are obtained from the soil-water retention curve. The analysis results show that the effect of infiltration and pore water velocity to the solute transport in soils are significant in the higher hydraulic-conductivity soils. The effect of pore water velocity is important at the initial stage of the vertical transport. The effect of infiltration is also increasing as time goes.

並列關鍵字

Dispersion Coefficient ； Pore Velocity ； Soil-Water Diffusivity ； Soil-Water Retention Curve