均一砂層力ラム中におけるSrイオン移動を 予測するモデルの評価

抄録

For an accurate prediction of contaminant migration in a porous medium, each of the various processes governing solute transport needs to be represented correctly in mathematical models. The transports of many contaminants of environmental concern are influenced by adsorption reaction in the subsurface. In this study, two models commonly used to represent adsorptive solute transport in homogeneous media, namely equilibrium model and two-site kinetic model, were examined for describing strontium transport in a homogeneous sand column. Carefully designed one-dimensional laboratory column experiments were conducted at three different fluid velocities using ⁸⁵Sr as an adsorptive tracer. Observed breakthrough curves (BTCs) showed asymmetric shape with large dispersion and slight velocity dependence in dispersion and skewness. The equilibrium model which was based on batch K,_d and a dispersivity of non-reactive tracer showed considerably smaller dispersion and apparently, failed to predict strontium transport in the sand. On the other hand, with a few optimizing parameters, the two-site kinetic model as well as the equilibrium model were able to describe observed BTCs successfully. However, the parameter sets required to describe BTCs for different fluid velocities are inconsistent with theory. In spite of good agreement observed between fitted and observed curves, inconsistent parameter sets indicate that processes occurring in the system are not accurately represented by these models. Since these models are virtually the only ones available to describe inorganic solute transport in homogeneous media, the presence of an additional unknown mechanism which causes considerably large dispersion in reactive BTCs is strongly suggested.