裂隙中双分子反应性溶质运移实验与模拟

Experiment and simulation of bimolecular reactive solution transport in fractures

地下水环境中化学作用对溶质运移具有重要影响,然而对于双分子反应性溶质运移研究,以往大多是在多孔介质中展开的,且使用传统的对流弥散方程不能很好地解决对生成物"过度预报"及"拖尾"问题。为了揭示双分子反应性溶质在裂隙介质中的运移机理,该文以苯胺(AN)和1,2-萘醌-4-磺酸钠(NQS)为例,开展了单个裂隙中双分子反应性溶质运移实验与模拟研究,重点研究了裂隙开启度和水流速度的影响,建立了考虑随时间衰减的反应性溶质运移数学模型(ADRE)并进行数值求解。与现有的对流弥散方程(ADE)模型及随机的截断幂函数模型(TPL)进行了比较,结果显示,裂隙中"过度预报"并不明显,TPL模型捕捉"拖尾"现象的能力高于ADE模型,改进的ADRE模型捕捉"拖尾"现象能力强且能较为准确地模拟反应物和生成物的浓度变化,其机理有待进一步研究。

Chemical action in groundwater environment has an important impact on solute transport. However, most of the studies on bimolecular reactive solute transport have been carried out in porous media in the past, and the traditional convection-dispersion equation can not solve the problem of "over-prediction" of the concentration of products and "long-tail" of products. In order to reveal the transport mechanism of bimolecular reactive solutes in fracture media, the aniline(AN) and 1,2-napthoquinone-4-sulfonic(NQS) acid were used as the chemical reactants in this study. The influence of the fracture width and flow velocity were mainly studied. A mathematical model of reactive solute transport(ADRE) considering effects of time decay was established and solved numerically. Compared with advection-dispersion equation(ADE) model and the stochastic Truncated Power-law(TPL) function model, it is concluded that the "over-prediction" in fracture media was not obvious, the TPL model is better than ADE model to fit the "long-tail". The improved ADRE model has a strong ability to catch "long-tail, and it can accurately simulate the concentration changes of reactants and products, and its mechanism needs further study.