Dynamic Behavior of Micobial Growth and Activity in Mixing-Controlled Contaminant Plumes

有机污染物，例如石油碳氢化合物，经常被释放到含水层中，在溶解的电子受体中形成耗尽的羽状物。这种羽状物的生物降解需要通过横向分散混合提供溶解的反应伙伴。在稳态条件下，已经建立了羽流长度和总反应速率的解析表达式。然而，在野外条件下，稳定状态很少占上风。污染物羽流的横向位置和混合水的化学成分都可能随时间而改变。对于主要不动的、活跃的微生物生物量来说，可能难以应对这些变化，因此混合控制羽流的整体降解可能受到阻碍。局部化学条件的动态变化也可能引起微生物群落中细菌种群相对丰度的变化。我们将在准二维流动系统中进行控制良好的混合控制生物反应输运实验室实验，应用动态边界条件来阐明这种水力和化学动力学对整体降解和所涉及的微生物群落的影响。这些实验将通过所有相关过程的数值模拟进行分析，从而促进将结果转移到实验中未涵盖的条件。我们假设动态边界条件的重要性取决于这些变化的相对时间尺度，而不是物理传输、生物量生长/衰减和激活/失活的时间尺度。

Organic contaminants, e.g. petroleum hydrocarbons, are frequently released into aquifers, forming plumes depleted in dissolved electron acceptors. Biodegradation of such plumes requires a dissolved reaction partner provided by transverse dispersive mixing. Analytical expressions for the plume length and the overall reaction rates have been developed for steady-state conditions. Under field conditions, however, steady state seldom prevails. Both the lateral position of a contaminant plume and the chemical composition of the mixing waters may change over time. For the predominantly immobile, active microbial biomass it may be difficult to cope with these changes so that the overall degradation of mixing-controlled plumes may be hampered. Dynamic changes in local chemical conditions may also induce shifts in the relative abundance of bacterial populations in a microbial community. We will conduct well controlled laboratory experiments of mixing-controlled bioreactive transport in quasi two-dimensional flow-through systems applying dynamic boundary conditions to elucidate the influence of such hydraulic and chemical dynamics on the overall degradation and the microbial communities involved. These experiments will be analyzed by numerical simulation of all relevant processes facilitating the transfer of results to conditions not covered within the experiments. We hypothesize that the importance of dynamic boundary conditions depends on relative time scales of these changes in comparison to the time scales of physical transport, biomass growth/decay and activation/deactivation.