Effects of mixing processes on microbial degradation and the distribution of microorganisms in stationary and non-stationary contaminant plumes

在拟议的项目中，我们希望研究混合过程和改变地下水流动状态对受污染含水层中微生物降解潜力的影响。微生物的降解活性将通过化合物特定同位素分析(CSIA)来量化，即残留的、尚未降解的污染物部分中13C/12C和D/H的稳定同位素分馏。在实验室储罐实验中，在静止或瞬变流动条件下会产生人工污染物羽流(如甲苯)。在储罐系统中增加明确定义的细菌培养物，并供应氚和非氚污染物的混合物，将能够以高分辨率(毫米尺度)量化微生物的降解。由于好氧和厌氧菌株的分馏特性非常不同，我们将能够区分这两种菌株对整个降解过程的各自贡献。此外，还将研究稳态和非稳态流动条件对引入微生物的影响。这里的总体问题是，面对频繁变化的环境条件(如缺氧-缺氧)的微生物的耐受性和/或灵活性如何，以及在干扰之后可能需要多长时间才能启动和恢复显着的降解。这一概念还将在实地进行研究，在那里将对采样点的50x50厘米分辨率的污染羽流的横截面进行采样。CSIA将提供关于就地生物降解活动的空间分布的信息。通过分子方法，还将对现场样本进行分析，以确定是否存在不同的群体(例如硫酸盐还原细菌和铁还原细菌)和个别微生物菌株(我们从实际地点分离的微生物)。实验室和现场调查结果的比较应揭示混合和非稳定流动条件对受污染含水层中自然衰减过程的影响的一般见解。

In the proposed project we want to study the effects of mixing processes and changing groundwater flow regimes on the microbial degradation potential in contaminated aquifers. Microbial degradation activities will be quantified by compound-specific isotope analysis (CSIA), i.e. the stable isotope fractionation of 13C/12C and D/H in the residual, not yet degraded contaminant fraction. In laboratory tank experiments artificial contaminant plumes (e.g. toluene) will be produced under stationary or transient flow conditions. The augmentation of the tank system with well defined bacterial cultures and the supply of mixtures of deuterated and non-deuterated contaminants will allow to quantify microbial degradation at a high resolution (mm-scale). Because of extremely different fractionation properties of aerobic and anaerobic strains we will be able to differentiate between the respective contributions of the two to the overall degradation processes. Furthermore, the effects of stationary and non-stationary flow conditions on the introduced microorganisms will be investigated. Here the overall question is how tolerant and/or flexible are microorganisms which are confronted with frequently changing environmental conditions (e.g. oxic-anoxic) and how long after a disturbance it might take to initiate and resuscitate a pronounced degradation. The concept will also be investigated in the field where a cross section through a contamination plume with a 50 x 50 cm resolution of the sampling spots will be sampled. CSIA will provide information on the spatial distribution of biodegradation activities in situ. By means of molecular methods the field samples will also be analysed for the presence of different groups (e.g. sulfate-reducing and iron-reducing bacteria) and individual strains of microorganisms (the ones we isolated from the actual site). Comparisons of results from laboratory and field investigations should reveal general insights into the effect of mixing and non-stationary flow conditions on natural attenuation processes in contaminated aquifers.