Reactive transport in the dynamic capillary fringe

挥发性有机污染物（VOC）和土壤气体（如O2，CO2）通过毛细边缘（CF）的传输取决于地下水位的形态和动态。人们普遍认为，CF是一个高度生物活性的区域，在那里发生有机化合物或污染物的生物降解。总体生物降解速率取决于例如电子受体如氧的供应，其受到CF中的扩散和分散的限制。该研究单位第一阶段的工作重点是示踪技术（染料示踪剂）和横向流体动力学分散的氧气传质以及由于空气截留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，并调查瞬态条件和非均匀性的影响。在第二阶段，调查将扩大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）。该提案的目标是·在瞬态条件下量化CF中反应系统的基本传质参数，以及·调查粗颗粒夹杂物的影响（非均匀性）在多孔介质填料的总传质和反应速率。流通实验和数值模拟（与SP 2，Bastian/Ippisch合作），通过高分辨率的空间和时间分析，研究均匀和复杂非均匀多孔介质中的反应实例。

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.