Reactive transport in the dynamic capillary fringe

挥发性有机污染物（VOC）和土壤气体（如O2、CO2）通过毛细条纹（CF）的运输取决于地下水位的形态和动态。人们普遍假设CF是一个高度生物活性的区域，在那里有机化合物或污染物的生物降解发生。总体生物降解率取决于电子受体（如氧气）的供应，这受到CF中的扩散和分散的限制。研究单元第一阶段的工作重点是示踪技术（染料示踪剂）和通过横向流体动力学分散的氧的传质，以及由于空气困住而导致的水相和气相之间的气体分配。总体目标是量化CF中的基本传质参数，并研究瞬态条件和异质性的影响。在第二个阶段，调查将扩展到非生物的快速模型反应（例如，通过减少地下水中的物种消耗氧气）。本提案的目标是：•量化瞬态条件下反应体系CF中的基本传质参数；•研究多孔介质填料中粗粒包裹体（非均质性）对总体传质和反应速率的影响。流动实验和数值模拟（与sp2， Bastian/Ippisch合作）将通过高分辨率的空间和时间分析来研究均匀和复杂非均质多孔介质中的示例反应。

Transport of volatile organic contaminants (VOC) and soil gases (e.g. O2, CO2) across the capillary fringe (CF) depends on the morphology and the dynamics of the groundwater table. It is widely hypothesized that the CF is a highly bioactive region, where biodegradation of organic compounds or pollutants takes place. Overall biodegradation rates depend for example on the supply of electron acceptors such as oxygen, which is limited by diffusion and dispersion in the CF. The work in the first phase of the research unit focused on tracer techniques (dye tracers) and mass transfer of oxygen by transverse hydrodynamic dispersion as well as gas partitioning between the aqueous and the gaseous phase due to air entrapment. Overall objectives were the quantification of the basic mass transfer parameters in the CF and the investigation of the impact of transient conditions and heterogeneities. In the second period, the investigations will be extended to abiotic, rapid model reactions (e.g. consumption of oxygen by reducing species in groundwater). Goals of this proposal are• to quantify the basic mass transfer parameters in the CF for reactive systems under transient conditions and• to investigate the impact of coarse-grained inclusions (heterogeneities) in the porous medium packing on overall mass transfer and reaction rates.Flow-through experiments and numerical modeling (in collaboration with SP 2, Bastian/Ippisch) will be carried out in order to study example reactions in homogeneous and complex heterogeneous porous media by high-resolution spatial and temporal analysis.