Diffusion/dispersion-limited mixing and reactions in saturated homogeneous and heterogeneous porous media

有机污染物在地下水中的自然衰减（主要是生物降解）往往依赖于电子给体和受体的混合。田间混合是横向扩散的结果，横向扩散是地下水流速、含水层典型长度尺度（如粒度）和含水层非均匀性以及自然水流系统动态的函数。该提案的目标有两个：1）在控制良好的实验室规模的实验中研究扩散限制反应，2）使用数值模型来阐述现场规模（时间和空间）的非均匀性和瞬态条件如何影响地下水中有机污染物的总体自然衰减率。受横向色散限制的示例反应将在实验室中使用创新的光学在线分析（TP 5）在时间和空间上以高分辨率进行研究。颗粒尺度的非均匀性和瞬态流动条件的影响将被量化，其结果将用于验证的数值传输/反应模型（PHT 3D）。该模型考虑了平流、扩散、吸附、生物降解（包括。动力学），并耦合到地球化学代码（PHREEQC）。经验证的代码用于现场规模的特定场景建模。

Natural attenuation (mainly biodegradation) of organic pollutants in groundwater often depends on mixing of electron donors and acceptors. Mixing in the field is the result of transverse dispersion, which is a function of groundwater flow velocity, the typical length scale in the aquifer (e.g. grain size) and aquifer heterogeneities, and the dynamics of the natural flow system. The objectives of this proposal are twofold: 1) to investigate dispersion-limited reactions in well-controlled bench-scale experiments and 2) to use numerical models to elaborate how heterogeneities and transient conditions at the field scale (in time and space) influence the overall natural attenuation rates of organic pollutants in groundwater. Example reactions limited by transverse dispersion will be investigated in the lab in high resolution in time and space using innovative optical online analysis (with TP 5). The influence of grain scale heterogeneities and transient flow conditions will be quantified and the results will be used for validation of a numerical transport/reaction model (PHT3D). The model accounts for advection, dispersion, sorption, biodegradation (incl. kinetics) and is coupled to a geochemical code (PHREEQC). The validated code is used for scenario specific modeling at the field scale.