The Experimental Study and Parameter Inversion on the Transport of Na~+ and Cd~(++) in Unsaturated Soil

摘要

Under the unsaturated Condition, we carried put a number of experiments of pollutant transport on 8 kinds of soil samples from Portugal and 1 kind of soil sample from Belgium by using Vacuum Suction Apparatus. In these experiments, mixed fluid of Na~+ and Cd~(++) is adopted as pollutant solution, and the breakthrough curves of Na~+ and Cd~(++) were obtained relatively. By a series of analysis and study, we have found: there are two types of sorption in the heavy metal ion Cd~(++) transport process, one of which is reversible and the other is irreversible, and the two types of sorption need to be represented by different empirical parameters in building physical models, the reversible sorption can be described by equilibrium formula and the irreversible sorption (precipitation) must be described by non-equilibrium Langmuir formula. And the sorption of Na~+ is reversible and can be represented by equilibrium sorption formulae only. Finally, the physical models for representing transport processes of Na~+ and Cd~(++) were obtained and the characteristic parameters of dominated phenomena in the transport processes were determined by inverse method (Gradient-Regularization Method). The computational results are in good conformity with our experiments.