考虑尺度效应的土壤溶质运移动力学特征分析

An Analysis on Dynamic Characteristics of Solute Transport Through Heterogeneous Soils with Scale-dependent Dispersion

[目的]为了了解土壤环境中弥散尺度效应、动力学吸附等作用对溶质运移过程的影响。[方法]应用Laplace变换方法和复变函数理论推得溶质运移动力学模型的解析解。利用De Hoog数值反演方法,验证解析解的正确性,利用解析解分析溶质在土壤中的运移特征。[结果]解析解的计算结果与反演函数Fourier级数项数2 N较大(N=500)时的De Hoog数值计算结果吻合很好;土壤溶质浓度随尺度效应的增强、吸附作用及生物降解作用的减弱而增大;分子扩散、一阶动力学吸附以及吸附相溶质降解作用对溶质运移变化影响较小。[结论]所推求解析解是正确的;土壤溶质运移的弥散尺度效应,溶质在液相和吸附相间的线性分配作用及溶质在液相中的降解作用是影响土壤溶质运移过程的主要因素。

[Objective] To understand the scale-dependent dispersion and non-equilibrium kinetic adsorption etc. on solute transport in heterogeneous soils. [Methods] An analytical solution of one-dimensional reactive scale-dependent solute transport kinetic model was obtained by Laplace-transform and the inverse transform based on the complex formulation, and was illustrated to be accurate compared with the De Hoog numerical inversion method. Moreover, the distribution regularities of the solute concentration in soil were discussed and the scale effects of soil solute transport, sorption and degradation on the solute transport were analyzed by using the analytical solution. [Results] The calculations of the analytical solution and the De Hoog numerical inversion was in good agreement when inverse function Fourier series number N was 500. The solute concen- tration increased with the increase of the heterogeneity of soils and the decrease of adsorption and degradation of solute, and it had little change with the molecular diffusivity, first-order kinetic rate process and the degradation of the sorbed phase.[Conclusion] The research confirmed that the scale effects of soil solute transport, the sorption distribution between the two regions and the degradation in the liquid phase play major roles in solute transport through heterogeneous soils.