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

地下水中有机污染物的自然衰减（主要是生物降解）往往依赖于电子供体和电子受体的混合。野外混合是横向分散的结果，横向分散是地下水流速、含水层典型长度尺度（如粒度）和含水层非均质性以及自然流动系统动力学的函数。本提案的目标有两个：1)在控制良好的实验中研究分散性限制反应；2)使用数值模型来阐述野外尺度（在时间和空间上）的非均质性和瞬态条件如何影响地下水中有机污染物的整体自然衰减率。受横向色散限制的例子反应将在实验室中以高分辨率的时间和空间进行研究，使用创新的光学在线分析（使用TP 5）。晶粒尺度非均质性和瞬态流动条件的影响将被量化，结果将用于数值输运/反应模型（PHT3D）的验证。该模型考虑了平流、分散、吸附、生物降解（包括动力学），并与地球化学代码（PHREEQC）耦合。经过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.