土壤溶质锋运移的解析解

Analytical Solution to Advance of Solute Front in Soils

为了推求土壤溶质锋运移与时间的关系 ,假设土壤溶质运移发生在溶质输入内边界至溶质锋之间 ,应用拉普拉斯变换方法求解输入内边界到溶质锋边界的对流—弥散方程 ( CDE)。溶质锋浓度解与半无限精确解的比较表明 ,在内边界至溶质锋边界内具有良好的一致性。溶质锋运移解的一个重要应用是估计实验室和田间条件的溶质运移参数。这个新的参数估计方法要求土壤中溶质锋随时间运移数据。如果应用有色示踪剂 ,溶质锋运移可以目测 ;如果应用其他示踪剂 ,可以通过 TDR或其它仪器测量示踪剂通量或体积浓度 ,确定溶质锋的深度。这个新的方法简单易行、节省时间 ,而且能够应用到实验和田间条件。

Solutes are assumed to transport from putting boundary(soil surface) to solute front boundary in order to find the solution of solute front ad vance with time for a semi-infinite porous media column or corresponding field soil conditions. Convection-dispersion equation(CDE), subjected to two bounda ry conditions both at soil surface (or inlet boundary) and at solute front i s solved analytically by using Laplace transformation method. The results of com parison between the analytical solution and the exact solution (in semi-infini te domain) show that the analytical solution is in good agreement with the solut ion in the range from putting boundary(soil surface)to the solute front. An im portant application of the advance of solute front is to estimate the transport parameters of solute movement through porous media under both laboratory and fie ld conditions. This leads to a new method for estimating parameters of solute tr ansport in soils. The new method requires observation of the advance of solute f ront with time. This can be done visually by using a tracer solution with dye in it. It can also be easily measured by using time domain reflectometry (TDR). Th e new method is simple, time saving, and is applicable to both laboratory soil co lumn and field soils.